Quasi-solid polymer electrolytes occupy a strategic position in battery design. Conventional liquid electrolytes conduct lithium ions quickly and wet electrode surfaces efficiently, but they leak, evaporate and burn. Fully solid-state electrolytes eliminate these hazards, yet they struggle with brittle mechanical behaviour, poor contact with electrodes and stubbornly low ionic conductivity at room temperature. Quasi-solid systems blend a polymer matrix with a small quantity of liquid or plasticising component, capturing much of the ionic mobility of a liquid while retaining the mechanical integrity and processability of a solid. The concept is not new; polymer electrolytes have been studied since the early 1980s, and nanocomposite approaches date back to landmark work in the late 1990s showing that ceramic nanoparticles could dramatically improve polymer electrolyte performance.

The central difficulty, as the review by Alexander Pavlovskii and colleagues makes clear, is that no single electrolyte material excels at everything. A practical electrolyte must conduct lithium ions rapidly, block electrons, withstand high voltages, resist dendrite penetration, remain mechanically robust and, crucially, form stable interfaces with both the anode and the cathode. These requirements frequently pull in opposite directions. Polymers such as poly(ethylene oxide), or PEO, are flexible and easy to process but conduct ions poorly at room temperature and oxidise above roughly four volts. Fluorinated polymers such as poly(vinylidene fluoride-co-hexafluoropropylene) offer better electrochemical stability but depend heavily on the liquid trapped in their pores. Gel polymer electrolytes based on polyacrylonitrile, polycarbonates and cellulose each bring their own trade-offs between conductivity, stability and sustainability.

This is where inorganic fillers enter the picture. The review organises the field’s filler strategies into several families: inert oxide ceramics such as silica, alumina, titania and zirconia; lithium-ion-conducting ceramics such as garnet-structured LLZO and NASICON-type LATP; and more exotic porous frameworks including metal-organic frameworks and covalent organic frameworks. Inert oxides do not conduct lithium ions themselves, yet decades of evidence show they can substantially raise conductivity and improve cycling. The classical explanation invokes Lewis acid-base interactions: surface hydroxyl and metal centres on the ceramic compete with lithium ions for coordination with the polymer chains and the salt anions, loosening the polymer structure, promoting segmental motion and freeing more charge carriers to move. Computational studies have recently added nuance, suggesting that silica nanoparticles can also create favourable percolating pathways for lithium transport along polymer-filler interfaces.

Lithium-ion-conducting ceramics go a step further by acting as genuine fast-ion conduits embedded in the polymer. Garnet-type Li7La3Zr2O12 and its tantalum-doped variants boast bulk conductivities that rival liquids, and when distributed as particles, fibres or three-dimensional frameworks within a polymer matrix, they provide continuous highways for lithium ions. Recent work highlighted in the review shows that the garnet surface chemistry matters enormously: lithium-rich surfaces can trap anions and raise the transference number, meaning a larger fraction of the total current is carried by lithium ions rather than counterions, while fluorinated surface treatments such as fluoroethylene carbonate modification improve wettability against lithium metal and suppress parasitic reactions. Three-dimensional garnet frameworks infiltrated with in-situ polymerised monomers represent one of the most sophisticated versions of this strategy, combining ceramic-level conductivity with intimate electrode contact.

Metal-organic frameworks and covalent organic frameworks are the newcomers. These crystalline, porous materials offer tunable pore chemistry at the atomic scale. Cationic covalent organic framework nanosheets, first reported as fast lithium-ion conductors in 2018, provide ordered one-dimensional channels through which ions migrate, and functionalised variants such as lanthanum-decorated ZIF-8 have been shown to enhance quasi-solid electrolyte performance. Because their pore surfaces can be designed to anchor anions, expose lithium-binding sites or catalyse beneficial decomposition reactions, these frameworks act less like passive fillers and more like programmable interfacial machinery. The review treats them as a frontier direction, noting that cost and scalability remain open questions.

Perhaps the most consequential theme of the review is interfacial chemistry, specifically the formation of the solid electrolyte interphase on the anode and the cathode electrolyte interphase on the cathode. These nanometre-thin layers, formed by electrolyte decomposition during the first charge cycles, determine whether a battery lives or dies. A good interphase conducts lithium ions, blocks electrons and stops growing; a bad one consumes active lithium, impedes ion flow and allows dendrites to nucleate. The authors emphasise that inorganic fillers reshape both layers. Ceramic surfaces can nucleate inorganic-rich interphases composed of lithium fluoride, lithium oxide and lithium carbonate species, which are mechanically strong and electrochemically stable. Fillers can also locally concentrate lithium ions at the electrode surface, homogenising the flux and delaying dendrite initiation, a mechanism implicated in the dendrite-free cycling achieved by several sandwich-structured and multilayer quasi-solid designs.

On the cathode side, the challenges are different but equally severe. High-voltage nickel-rich layered oxides release reactive oxygen and dissolve transition metals, which migrate to the anode and poison it. Conventional PEO-based electrolytes oxidise at these potentials, and recent theoretical work has mapped the degradation pathways and predicted cathode electrolyte interphase components. The review describes how tailored fillers and layered electrolyte architectures, including quasi-double-layer designs with adjustable interphases, can buffer the cathode surface, scavenge harmful species and extend the practical voltage window. Strong Lewis-acid coordinated polymer systems have even demonstrated compatibility with 4.8-volt cathodes in all-solid-state cells delivering over 580 watt-hours per kilogram, a figure that rivals or exceeds the best liquid-electrolyte cells.

The authors are careful to frame these advances against the remaining obstacles. Scalable fabrication is the elephant in the laboratory: many of the highest-performing composite electrolytes rely on intricate in-situ polymerisation, electrospinning or framework synthesis that would be difficult to translate to gigafactory roll-to-roll processing. Advanced operando characterisation is needed to watch interphases form and evolve in real cells rather than inferring them from post-mortem analysis. The review also points to data-driven electrolyte optimisation, in which machine learning navigates the vast compositional space of polymers, salts, solvents and fillers far faster than trial-and-error experimentation. Sustainability concerns appear as well, with recent demonstrations of PFAS-free quasi-solid electrolytes and fluorine-free formulations that form lithium-oxide-rich interphases signalling a push toward greener chemistry.

What emerges from the survey is a coherent design philosophy rather than a single breakthrough material. The performance of a quasi-solid polymer electrolyte is not dictated by any one component but by the engineered interplay between polymer chemistry, filler identity, filler surface treatment and the resulting electrode-electrolyte interphases. Rational filler selection, the authors conclude, is as important as the polymer matrix itself, and interface engineering is the lever that converts good materials into practical batteries. With the International Energy Agency projecting continued rapid growth in electric vehicle adoption and safety standards such as IEC 62660-3 tightening requirements for automotive cells, the incentive to commercialise non-flammable, high-performance electrolytes has never been stronger. Quasi-solid polymer electrolytes, armed with intelligently chosen inorganic fillers, may be the architecture that finally delivers it.

Subject of Research: Roles of inorganic fillers in quasi-solid polymer electrolytes for lithium-ion batteries

Article Title: Interfacial chemistry and hybrid phase engineering in quasi-solid polymer electrolytes: roles of inorganic fillers in advanced lithium-ion batteries

Article References: Pavlovskii, A. A., Pushnitsa, K., Kosenko, A., Novikov, P., & Popovich, A. A. (2026). Interfacial chemistry and hybrid phase engineering in quasi-solid polymer electrolytes: roles of inorganic fillers in advanced lithium-ion batteries. Ionics. https://doi.org/10.1007/s11581-026-07488-x

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07488-x

Keywords: quasi-solid polymer electrolytes, lithium-ion batteries, inorganic fillers, solid electrolyte interphase, cathode electrolyte interphase, garnet ceramics, metal-organic frameworks, covalent organic frameworks, interface engineering, hybrid materials, solid-state batteries, ionic conductivity

The core chemistry of NIPUs rests on a reaction that avoids phosgene entirely, the notorious reagent used to manufacture conventional isocyanate monomers in the first place. Instead, NIPU synthesis begins with epoxidized compounds, often derived from plant oils such as soybean, castor or linseed oil, which are converted into cyclic carbonates by reaction with carbon dioxide. These five-membered cyclic carbonate rings then undergo a polyaddition reaction with polyamines, yielding polyhydroxyurethanes. The step is elegant in its atom economy: carbon dioxide is literally locked into the polymer backbone, and the reaction produces beta-hydroxy urethane linkages that conventional polyurethanes lack. Those extra hydroxyl groups are not a cosmetic detail. They dramatically increase the density of hydrogen bonding within the cured adhesive, which in turn governs cohesive strength, viscosity, and the way the adhesive wets and grips a substrate. The Roorkee review emphasizes that understanding this beta-hydroxy urethane chemistry is the single most important lever for tuning NIPU adhesive performance.

Yet the same chemistry that makes NIPUs greener also makes them slower. The aminolysis of cyclic carbonates proceeds at a markedly lower rate than the isocyanate-polyol reaction that cures conventional polyurethane adhesives, and the steric environment of the carbonate ring matters enormously. Five-membered cyclic carbonates, the easiest to make from epoxides, are the least reactive; six- and seven-membered rings react faster but are harder to synthesize. Catalysts, including organocatalysts and metal salts, can accelerate the polyaddition, but the review highlights that curing kinetics remain one of the central bottlenecks for industrial adoption, where production lines demand rapid bond formation within seconds or minutes. The kinetics also interact with network evolution: as the polyhydroxyurethane network grows and crosslink density rises, the mobility of remaining amine and carbonate groups falls, slowing conversion further and leaving residual unreacted functionality that can compromise moisture resistance and long-term durability.

Adhesive performance, the review stresses, is never a bulk property alone. It emerges from a complex interplay among molecular structure, reaction kinetics, network architecture and interfacial phenomena at the boundary between adhesive and substrate. A polyhydroxyurethane may be strong in the middle of a bond line yet fail at the interface if its surface tension, viscosity or curing shrinkage are poorly matched to the adherend. Hydrogen bonding contributes not only to cohesion but also to specific interactions with polar substrates such as wood, glass, metal oxides and cellulosic fibers, which is one reason bio-based NIPU systems perform well in wood bonding and composite applications. The authors argue that a comprehensive understanding of the interplay between molecular architecture, network topology and interfacial interactions is essential for optimizing adhesion, and they frame interface engineering as a discipline equal in importance to monomer synthesis.

One of the most active frontiers is the use of bio-based precursors. Epoxidized vegetable oils provide multifunctional cyclic carbonate feedstocks at low cost and from renewable sources, and lignin-derived, tannin-derived and carbohydrate-derived carbonates extend the palette further. But renewable does not automatically mean high-performing. Flexible aliphatic chains from plant oils tend to produce soft, low glass-transition networks with excellent toughness but limited heat resistance, while aromatic and cycloaliphatic carbonate monomers raise thermal stability and stiffness at the expense of flexibility and, sometimes, of renewability. The review examines how synthetic monomers and bio-based monomers can be blended to balance these properties, and how the hydrophobicity of the chosen precursors directly affects one of NIPU adhesives’ weakest points: wet durability, the retention of bond strength after prolonged exposure to moisture, where the very hydroxyl groups that strengthen hydrogen bonding can also invite water uptake and plasticization.

To overcome these limits, researchers have developed a suite of hybridization and modification strategies that the review treats in depth. Epoxy hybridization combines the carbonate-amine polyaddition with epoxy-amine curing in a single system, allowing the fast-reacting epoxy network to deliver early strength and environmental resistance while the urethane network contributes toughness and hydrogen bonding. Siloxane modification introduces flexible, hydrophobic silicon-oxygen segments that repel water, lower surface energy and improve adhesion to difficult substrates, addressing the moisture-sensitivity problem at its chemical root. Both approaches preserve the isocyanate-free synthesis route while borrowing performance features from established adhesive chemistries, and the review presents them as among the most effective demonstrated routes to improving curing efficiency, environmental stability and mechanical performance simultaneously.

Perhaps the most conceptually exciting strategy is the design of vitrimer-like NIPU networks. Vitrimer chemistry, in which covalent bonds can exchange under heat without losing network connectivity, has transformed the recyclability debate in polymer science, and polyhydroxyurethanes are natural candidates because their beta-hydroxy urethane linkages participate in reversible transcarbamoylation and related exchange reactions. A vitrimer-like NIPU adhesive can in principle be debonded on demand, reprocessed, or repaired, enabling disassembly of bonded structures and recovery of components at end of life, a capability conventional thermoset adhesives cannot offer. Dynamic covalent chemistries also allow self-healing of microdamage within the bond line, extending service life. The review positions these dynamic networks as a way to make the sustainability case for NIPUs even stronger, coupling a green synthesis route with a circular end-of-life scenario.

The challenges that remain are formidable and honestly catalogued. Slow curing kinetics clash with high-throughput manufacturing. Wet durability and hydrolytic stability still trail conventional polyurethanes in the most demanding applications. Processing windows can be narrow, since the viscosity of hydroxyurethane prepolymers and the stoichiometric balance between carbonate and amine groups must be carefully controlled. Industrial scalability depends not only on formulation but on the supply of cyclic carbonate monomers at commodity volumes, which in turn depends on carbon dioxide utilization technology and epoxide availability. The review notes recent developments in cyclic carbonate structural design, including ring-size engineering and catalytic carbonation of epoxides, and alternative synthetic pathways beyond the classical carbonate-amine route as active areas that could relax these constraints.

What emerges from the IIT Roorkee analysis is a field moving from laboratory curiosity toward genuine industrial contender, driven by regulatory pressure on isocyanates, consumer demand for bio-based materials, and the intrinsic elegance of a chemistry that consumes carbon dioxide. The authors’ central message is that NIPU adhesives cannot be optimized by recipe tweaking alone; progress requires a holistic grasp of how monomer structure dictates kinetics, how kinetics shape network topology, and how topology controls both bulk mechanics and interfacial bonding. If the remaining hurdles of cure speed and wet strength fall to the hybrid and dynamic strategies now proliferating in the literature, the sticky future of manufacturing may well be one in which the strongest bonds are also the cleanest, formed without isocyanates, built partly from captured carbon dioxide, and designed from the outset to come apart again when their job is done.

Subject of Research: Non-isocyanate polyurethane (NIPU) adhesive chemistry and interface engineering

Article Title: Non-isocyanate polyurethane (NIPU) adhesives: Chemistry to interface engineering and applications

Article References: Chatterjee, A., Datta, S., Haldar, M., Sen, S., Sadhu, A., AM, S., & Maji, P. K. (2026). Non-isocyanate polyurethane (NIPU) adhesives: Chemistry to interface engineering and applications. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02044-7

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02044-7

Keywords: non-isocyanate polyurethane, NIPU adhesives, cyclic carbonates, polyhydroxyurethane, sustainable polymers, hydrogen bonding, curing kinetics, vitrimer networks, bio-based monomers, interface engineering, epoxy hybridization, siloxane modification

The strategy, described by the authors as a pre-calcination thermomechanical hot-pressing treatment, was integrated into an established hydrothermal synthesis route for carbon-coated lithium iron phosphate, commonly abbreviated LFP/C. In a typical hydrothermal process, the olivine precursor particles are formed in solution, mixed with an organic carbon source such as glucose, and then calcined at high temperature to crystallize the phase and pyrolyze the carbon coating into a conductive shell. The Korean team inserted an additional step between these stages. After the hydrothermal reaction but before the high-temperature sintering, they subjected the amorphous precursor-glucose matrix to uniaxial pressure of 5 megapascals at a temperature of 200 degrees Celsius for 10 minutes. The parameters were deliberately optimized and held fixed to establish reproducibility and to define clear processing boundaries for the technique.

The timing of this mechanical treatment is what makes it scientifically interesting. At 200 degrees Celsius, the precursor material has not yet crystallized into the ordered olivine framework. It exists as a soft, amorphous matrix interspersed with glucose, the organic molecule that will later become the carbon coating. Applying pressure at this stage produces what the researchers describe as localized physical consolidation within that matrix. In practical terms, the pressing bridges void spaces that exist between and within the precursor particles, forcing them into more continuous contact with one another. Because this compaction happens before phase crystallization, the improved particle-to-particle contact is locked in when the material is subsequently fired, rather than being erased by later processing steps.

Why does this matter for battery performance? The answer lies in the concept of charge-transfer resistance, a quantity electrochemists denote as Rct. Every time a lithium ion crosses the interface between the electrode material and the electrolyte, and every time an electron hops between particles in the composite electrode, it encounters resistance. High interfacial resistance manifests as voltage polarization, meaning the cell delivers less voltage than it theoretically should during discharge and requires more voltage than expected during charge. That wasted energy appears as heat and reduces the usable capacity of the battery, particularly at high charge and discharge rates where the demand for rapid ion and electron transport is greatest. Poorly connected particle networks force electrons to take tortuous paths through the carbon additive, and isolated particles may be electronically disconnected altogether, contributing nothing to the cell’s capacity.

When the team compared hot-pressed and conventional unpressed electrodes, the differences were clear. The hot-pressed LFP/C cathode exhibited remarkably minimized voltage polarization and a significantly reduced interfacial charge-transfer resistance relative to the unpressed baseline. The continuous electrical contact networks enforced by the pre-sintering compaction gave electrons shorter, more direct pathways through the electrode, while the bridged void spaces improved the physical intimacy between active material, carbon coating, and conductive additives. The result is an electrode in which a larger fraction of the active material participates effectively in the lithiation and delithiation reactions, and in which the reactions themselves proceed with less energetic penalty at the interface.

The galvanostatic cycling results underscore the practical value of the treatment. Under repeated charge and discharge, the optimized hot-pressed cathode demonstrated robust early-stage transport kinetics and maintained a highly stable discharge capacity of well over 110 milliampere-hours per gram after 100 cycles. For lithium iron phosphate, whose theoretical capacity is approximately 170 milliampere-hours per gram, sustaining capacity above 110 milliampere-hours per gram over a hundred cycles indicates that the electrode retains both its structural integrity and its transport advantages through repeated lithium insertion and extraction. Stability in early cycling is particularly significant because degradation mechanisms such as particle cracking, carbon coating disruption, and interfacial film growth tend to be most aggressive in the initial cycles, when the electrode microstructure is still adapting to the volume changes of lithiation.

The study also carries a broader message about where the next gains in battery materials may come from. Much of the historical progress on lithium iron phosphate has come from chemistry: reducing particle size to shorten lithium diffusion distances, coating particles with carbon to improve conductivity, and doping the lattice with supervalent ions to create charge carriers. The work of Choi, Heo, and their colleagues, supervised by corresponding author Jong-Tae Son, demonstrates that processing engineering, the physical manipulation of the material between chemical synthesis steps, offers a complementary and potentially inexpensive lever. Hot pressing requires no exotic reagents, no rare additives, and no fundamental change to the synthesis chemistry. It is a mechanical step that could, in principle, be incorporated into existing powder processing lines with modest capital investment.

The choice of 200 degrees Celsius, 5 megapascals, and 10 minutes reflects a careful balancing act. The temperature must be high enough to soften the amorphous precursor and the glucose matrix so that particles can deform and consolidate under pressure, but low enough to avoid premature crystallization or carbonization that would fix the microstructure before compaction is complete. The pressure must be sufficient to close voids and enforce contact, yet gentle enough to avoid fracturing particles or damaging the nascent carbon precursor coating. The 10-minute hold keeps the process compatible with industrial throughput. By strictly optimizing and reporting these boundaries, the authors have provided a reproducible recipe that other laboratories can replicate and extend, testing whether different pressures, temperatures, or hold times yield further improvements.

The findings arrive at a moment when lithium iron phosphate is expanding its share of the global battery market. Its cobalt-free chemistry sidesteps the ethical and supply-chain concerns associated with cobalt-based cathodes, and its thermal stability makes it attractive for applications where safety is paramount. Improving its rate capability and interfacial kinetics without raising cost is therefore a goal with enormous economic leverage. Interface engineering of the kind demonstrated here, in which the physical connectivity of the electrode’s internal network is deliberately sculpted before the material reaches its final form, could complement ongoing advances in electrolyte formulation, cell design, and manufacturing scale-up.

For the battery community, the study offers a reminder that the path from powder to performance runs through microstructure. Two electrodes made from chemically identical active material can behave very differently depending on how well their particles touch, how continuous their conductive networks are, and how much resistance ions and electrons encounter at each interface. By pressing the question of connectivity into the synthesis process itself, quite literally, the Korean team has shown that a modest thermomechanical nudge at the right moment can echo through the entire life of a battery cell. As manufacturers search for incremental gains that add up to faster charging, longer range, and cheaper storage, such processing insights into the olivine framework may prove to be among the most practical tools available.

Subject of Research: Hot-pressing treatment of hydrothermally synthesized LiFePO4/C cathodes to reduce charge-transfer resistance in lithium-ion batteries

Article Title: Effect of hot-pressing on charge transfer resistance and electrochemical performance of LiFePO₄ cathodes

Article References: Choi, Y.-H., Heo, G.-W., Kim, J. H., Won, J.-M., Lee, S.-H., Choi, M.-S., Cho, J.-H., Kang, S., & Son, J.-T. (2026). Effect of hot-pressing on charge transfer resistance and electrochemical performance of LiFePO₄ cathodes. Ionics. https://doi.org/10.1007/s11581-026-07522-y

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07522-y

Keywords: LiFePO4, cathode, hot pressing, charge-transfer resistance, hydrothermal synthesis, olivine, lithium-ion battery, carbon coating, voltage polarization, electrochemical performance, interface engineering, sintering

Writing in Advanced Composites and Hybrid Materials, the group led by Tata Sanjay Kanna Sharma, Jin Suk Chung, and Won Mook Choi describes a bifunctional heterostructure in which phase-pure bismuth telluride nanosheets are woven into a matrix of titanium carbide MXene, a conductive ceramic-like material derived by etching aluminum from layered titanium carbide precursors. The strategy is deceptively simple in concept: let the topological insulator supply the catalytic chemistry while the MXene supplies the electrical plumbing and the mechanical armor. In practice, achieving that partnership required precise control over synthesis, because bismuth telluride is notoriously easy to form with defects and secondary phases that ruin its electronic character.

The researchers produced their bismuth telluride nanosheets through a surfactant-assisted hydrothermal method, a wet-chemical route in which crystals grow from a hot aqueous solution under the guidance of organic molecules that steer nucleation along particular crystal faces. The surfactant acts like a molecular traffic controller, encouraging the growth of thin, well-defined platelets rather than irregular clumps. Once the nanosheets were formed, they were integrated into the MXene framework, whose negatively charged, functionalized surfaces, denoted Ti3C2Tx in the literature, help anchor the chalcogenide sheets and create intimate interfacial contact between the two layers.

What makes the interface so important is the physics of charge transfer. In electrocatalysis, every molecule of hydrogen gas produced or oxygen bond broken requires electrons to move from the electrode to the reacting species, or vice versa. Any bottleneck along that path, whether from poor conductivity, a sluggish interface, or a corroding surface, shows up as extra voltage that must be supplied to drive the reaction. That extra voltage, called overpotential, is the enemy of efficient energy conversion, because it represents energy wasted as heat. By fusing the two materials at the atomic scale, the team created a highway for electrons that bypasses the conductivity limitations of bulk bismuth telluride entirely.

The evidence for this synergy comes from an unusually thorough battery of structural probes. Synchrotron-based X-ray analysis allowed the researchers to examine the crystal structure of the composite with high precision, confirming that the bismuth telluride retained its phase purity even after integration with the MXene. Temperature-dependent Raman spectroscopy, which tracks how the vibrational fingerprints of a material shift as it is heated and cooled, revealed that the MXene incorporation modifies the structural and vibrational characteristics of the bismuth telluride, a sign that the two materials interact strongly at their junction rather than merely sitting side by side.

Perhaps the most consequential finding concerns durability. Bismuth telluride, like many chalcogenides, is vulnerable to oxidation, and a corroded surface loses the very electronic properties that make it interesting. Time-of-flight secondary ion mass spectrometry, a technique capable of mapping chemical species layer by layer with exquisite sensitivity, indicated that the MXene effectively passivates the chalcogenide surface, shielding it against oxidation. In other words, the MXene does double duty: it is both a conductive scaffold that ferries electrons and a structural buffer that protects the delicate topological insulator from the chemical assault of its own working environment.

The electrochemical performance numbers are striking. For the hydrogen evolution reaction, the cathodic half of water splitting, the composite required an overpotential of just 260 millivolts to sustain a current density of 100 milliamperes per square centimeter, a current level relevant to industrial electrolyzers rather than laboratory curiosities. For the oxygen evolution reaction, the anodic counterpart and historically the more difficult of the two reactions, the overpotential was 490 millivolts at the same demanding current density. The material also catalyzed the oxygen reduction reaction with an onset potential of 0.81 volts, the reverse chemistry that powers fuel cells and rechargeable metal-air batteries. In every case, the heterostructure significantly outperformed pristine bismuth telluride, confirming that the improvement stems from the engineered interface rather than the topological insulator alone.

Mechanistic probing added a layer of understanding that goes beyond performance metrics. The experiments indicate that the hydrogen evolution reaction proceeds predominantly at bismuth sites, enabled by partial bismuth-oxygen surface termination, a subtle surface chemistry that appears to tune the binding energy of hydrogen intermediates into the optimal range. The MXene, meanwhile, plays a supporting but indispensable role: it supplies rapid electron conduction to the active sites and acts as a sink for defects, stabilizing the catalytic centers that would otherwise degrade. This division of labor, with one material hosting the chemistry and the other managing the electrons and the damage, offers a design template that could be applied well beyond this particular pairing.

The broader significance lies in the emerging field of van der Waals heterostructures, in which atomically thin layers of different materials are stacked and coupled to produce properties that neither constituent possesses alone. The keywords that accompany the paper, including active-site engineering, charge-transfer kinetics, and energy storage electrodes, signal the authors’ ambition to treat the interface itself as the active component. Because both bismuth telluride and MXenes are two-dimensional, their junctions can in principle be designed with atomic precision, opening a path to rational optimization of charge transport and ion kinetics rather than the trial-and-error mixing that has historically dominated composite electrode research.

Challenges remain before such materials reach commercial electrolyzers or fuel cell stacks. MXenes are themselves susceptible to oxidation in water, scaling up surfactant-assisted hydrothermal synthesis demands careful process control, and long-term stability testing under industrial conditions will be essential. Still, the demonstration that a single interface-engineered heterostructure can drive hydrogen evolution, oxygen evolution, and oxygen reduction with high efficiency is a compelling proof of concept. If the approach generalizes to other topological insulators and MXene chemistries, the exotic surface states first predicted in quantum physics laboratories may one day help split water on an industrial scale, turning a celebrated curiosity of condensed matter into a workhorse of the clean energy economy.

Subject of Research: Interface engineering of Bi2Te3-MXene two-dimensional heterostructures for electrocatalytic energy conversion and storage

Article Title: Interface-engineered Bi2Te3-MXene heterostructure for multifunctional energy conversion and storage

Article References: Sharma, T. S. K., Babu, B. M., Jana, J., Solaiappan, L., Kumar, R., Kuriam, M. M., Lee, Y., Hur, S. H., Shin, T. J., Chung, J. S., & Choi, W. M. (2026). Interface-engineered Bi2Te3-MXene heterostructure for multifunctional energy conversion and storage. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02072-3

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02072-3

Keywords: bismuth telluride, MXene, topological insulator, heterostructure, hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, electrocatalysis, two-dimensional materials, charge transfer, energy storage, interface engineering

The appeal of perovskites begins with their crystal chemistry. The archetypal ABX₃ structure pairs an organic or inorganic cation such as methylammonium, formamidinium, or cesium in the A site with a divalent metal cation, usually lead, tin, or germanium, in the B site, and a halide anion such as iodide, bromide, or chloride in the X site. This arrangement delivers strong absorption across the visible spectrum, tunable bandgaps, long carrier diffusion lengths, low exciton binding energies, and a remarkable tolerance to defects. Crucially, these films can be deposited from solution at low temperature, opening the door to roll-to-roll printing and flexible substrates that rigid silicon panels cannot match.

A typical device stacks the perovskite absorber between an electron transport layer and a hole transport layer, all held between a transparent conductive oxide and a metal electrode. When light strikes the absorber, excitons dissociate almost effortlessly into free charges, which must then be swept out by the correct transport layer before they recombine. In the conventional n–i–p configuration the electron transport layer sits beneath the perovskite; in the inverted p–i–n design the hole transport layer does. Although both operate on the same photophysical principles, the review emphasizes that interfacial energetics, charge dynamics, and long-term stability diverge sharply between the two, and that interfaces are also the sites where the perovskite film nucleates and crystallizes, shaping grain size, morphology, and defect density.

One stubborn symptom of poor interfaces is current–voltage hysteresis, in which the measured efficiency depends on the direction and speed of the voltage scan. Mobile ions migrating through the lattice and charges trapped at interfaces are the chief culprits, which is why the review treats interface optimization as the central lever for reproducible performance. On the electron transport side, tin oxide has become the material of choice, processed at roughly 150 degrees Celsius and driving efficiencies from just over 17 percent in 2015 to 25.7 percent in recent years. Its rivals carry heavier baggage: zinc oxide degrades perovskites under thermal and ultraviolet stress, titanium dioxide demands sintering above 450 degrees Celsius and photocatalytically damages the absorber under UV light, and niobium pentoxide offers stability but lower conductivity and trickier processing.

Tin oxide, however, is not flawless. The review catalogs its limited carrier concentration, inherent surface defect density, and the hysteresis that follows, then details how elemental doping has rescued it. Alkali metal fluorides form coordination bonds with tin at oxygen vacancies, raising electron mobility while hydrogen bonding with amine groups suppresses organic cation diffusion. Zirconium doping delivered 19.54 percent efficiency through low-temperature solution processing, niobium doping reached 20.47 percent by cutting series resistance and balancing electron and hole flux, and magnesium doping controlled oxygen vacancy formation to lift efficiency from 6.62 to 17.25 percent. Even titanium dioxide has been revived: magnesium doping boosted efficiency by 16 percent with 91 percent retention after 30 days in ambient air, tin doping achieved 17.2 percent through improved charge collection, and rubidium chloride additives seeded dense, low-trap perovskite growth with negligible hysteresis and fill factors above 80 percent.

The frontier has since moved to molecular-scale interface modification. Water-dispersed tin oxide quantum dots spin-coated onto rough fluorine-doped tin oxide often agglomerate, leaving poor hole-blocking and depressed voltage and fill factor. Polyacrylic acid stabilization improves dispersion, but the breakthrough came when atomic layer deposition supplied a hydroxyl-rich underlayer for chemical anchoring, yielding 24.97 percent efficiency with strong stability even in larger-area devices. A thiazole-based molecule called TDA then demonstrated asymmetric dual-site passivation, with one nitrogen site mending tin-related defects and another addressing lead and iodide defects, reaching 24.96 percent efficiency and an open-circuit voltage of 1.20 volts. A π–π stacked bilayered molecular bridge built from an imidazolium salt pushed a certified efficiency to 25.27 percent, while sulfonyl diimidazole modification lifted efficiency from 21.61 to 23.31 percent by aligning energy levels and promoting uniform crystallization.

Cross-linking and gluing strategies round out the electron transport story. Bisphenol S cross-linked tin oxide films grew larger grains and better-oriented formamidinium lead iodide, delivering 24.87 percent efficiency against 23.55 percent for controls. Chitosan grafted with ethylenediaminetetraacetic acid stabilized the nanoparticle colloid and produced pinhole-free buried interfaces worth 25.12 percent. Most strikingly, a three-dimensional molecular glue formed from potassium tetrafluoroborate and trifluoromethane sulfonamide simultaneously tamed lattice mismatch, oxygen vacancies, and formamidinium cations, yielding 25.8 percent efficiency with negligible hysteresis and a certified 24.57 percent on a one-square-centimeter device, a scale that matters for commercialization.

Inverted devices tell a parallel tale on the hole transport side. The p–i–n architecture avoids high-temperature sintering, uses cheaper silver or aluminum electrodes instead of gold, and tolerates dopant-free transport layers that show less hysteresis and better stability. Yet its workhorse material, PEDOT:PSS, is acidic and hygroscopic, corroding the transparent electrode and inviting degradation, while its common dopant LiTFSI undermines longevity and the additive tert-butylpyridine can dissolve into the perovskite. Remedies include dedoping with sodium hydroxide, a self-woven polyionic complex deposition method that achieved 19.49 percent with a pinhole-free monolayer, and copper(II) counterions that raised efficiency to 19.44 percent by adjusting the work function. The hydrophobic polymer PTAA offers better energy alignment but resists coating; doping it with the π-conjugated molecule NPB reached 20.15 percent, and two-dimensional black phosphorus doping suppressed trap-assisted recombination while enhancing hydrophobicity.

The most consequential trend the review identifies is the rise of self-assembled monolayers, ultrathin molecules that chemisorb onto oxide electrodes and act as dopant-free hole selectors. Their minimal thickness cuts parasitic absorption, their energy levels are tunable, and they passivate defects while promoting high-quality perovskite growth. Dye-based monolayers such as N719 stabilized contacts at 24 percent efficiency; a thermally cross-linkable fluorinated carbazole monolayer exceeded 24 percent with superior solvent resistance; and an asymmetric design built on a fused thienoindole core with fluorine substitution achieved a certified 25.17 percent. Binary monolayer systems pairing a dipole-enhancing dibenzocarbazole molecule with the standard MeO-2PACz reached 24.52 percent with improved thermal stability, while perdeuterated carbazole lowered molecular vibrations to suppress non-radiative recombination, hitting 24.87 percent with added UV shielding. A spiro-type monolayer with a twisted, aggregation-resistant core outperformed the widely used 4PACz at 25.28 percent, and methylthio and thiophene substitutions pushed efficiencies to 25.13 percent and beyond by tuning dipoles and Lewis-basic passivation.

The authors close with a clear-eyed roadmap: scalable low-temperature electron transport deposition, real-time probing of interfacial degradation, hybrid inorganic–organic transport layers, uniform monolayer coverage over large areas, and roll-to-roll compatible SAM chemistries. The message for the field is that perovskite photovoltaics no longer hinge on discovering a better absorber but on mastering the few nanometers where absorber meets transport layer. If the molecular toolkit documented here continues its trajectory, the review suggests, the gap between laboratory champions and manufacturable modules may close faster than skeptics expect, positioning perovskites as a genuinely viable platform for next-generation solar energy.

Subject of Research: Interface engineering in conventional and inverted perovskite solar cells

Article Title: Emerging trends in interface processing: a comparative review of conventional and inverted perovskite solar cells

Article References: Nisa, Q. A. K., & Kim, J. H. (2025). Emerging trends in interface processing: a comparative review of conventional and inverted perovskite solar cells. Advances in Industrial and Engineering Chemistry, 1(1), Article 13. https://doi.org/10.1007/s44405-025-00013-0

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00013-0

Keywords: perovskite solar cells, interface engineering, electron transport layer, hole transport layer, tin oxide, self-assembled monolayers, PEDOT:PSS, PTAA, power conversion efficiency, dopant-free materials, photovoltaics, device stability

The appeal of liquid metals begins with a basic physical paradox. Conventional stretchable conductors rely on rigid fillers, such as silver flakes or carbon particles, embedded in an elastic matrix. Increasing the filler loading improves conductivity but stiffens the composite and accelerates fatigue under repeated strain; reducing the loading preserves softness but degrades electrical performance. This conductivity–softness trade-off has constrained generations of wearable and implantable devices. Liquid metals, most notably eutectic gallium–indium alloys that remain molten at room temperature, sidestep the problem entirely because the conductive phase is itself a fluid. Droplets of the alloy can be suspended in elastomers, where they deform, elongate and reconfigure with the surrounding polymer rather than resisting it, maintaining metallic properties across large strains.

The review emphasizes that liquid metal composites deliver far more than stretchable wiring. When droplets are dispersed through a soft polymer, they enhance not only electrical conductivity but also dielectric and thermal properties. Elongated liquid metal inclusions, for example, have been shown to raise the thermal conductivity of elastomers dramatically, enabling soft materials that can dissipate heat, and liquid metal inclusions have been used to create high-permittivity dielectric elastomers for capacitive and actuating applications. In one striking demonstration highlighted in the review, an electrically insulating liquid metal silicone compound combined electromagnetic interference shielding with direct electronic potting and thermal management, showing that a single soft composite can perform multiple functions once reserved for rigid metal housings.

Yet the same fluidity that gives liquid metals their conformability creates their greatest engineering headaches. A liquid conductor can leak, smear, delaminate or migrate within a device, destroying pattern fidelity and reliability. The authors argue that the decisive design variable is not the liquid metal itself but the interfaces it forms, both between liquid metal and the surrounding polymer and between liquid metal inks and the substrates and components they must connect. Interface engineering, they contend, is essential for mitigating leakage, delamination and functional degradation under deformation, and tailored interfacial design is what converts a promising ink into a robust, integrated device.

A rich toolkit of surface chemistry has emerged to control these interfaces. Gallium-based alloys spontaneously form a thin native oxide skin that dramatically alters their interfacial energy, lowering surface tension enough to allow the metal to be shaped, printed and stabilized as droplets. Researchers have exploited this oxide, and chemical modifications of it, to stabilize particles, tune wettability and promote adhesion. Polyphenol-induced adhesives have produced liquid metal inks that write directly on nearly any substrate, while thiol coordination chemistry has been used to soften liquid metal particles and switch their conductivity on demand. Hydrogen-doped viscoplastic microparticles have enabled stretchable printed metal lines, and finite-gel strategies have produced highly concentrated inks suitable for direct writing.

Patterning at high resolution remains one of the field’s defining challenges, and the review surveys how recent advances in droplet stabilization and ink formulation are addressing it. Ultrasonic sintering has been used to assemble liquid metal particles within polymers into elastic printed circuit boards, in which pressing or sonicating the particles ruptures their oxide shells and merges them into continuous, leakage-resistant traces. Laser sintering of liquid metal nanoparticles offers a scalable route to soft, flexible electronics, and projection lithography has enabled rapid printing of highly stretchable circuits. Meniscus-guided printing has produced stable semi-solid microgranular particles for soft electronics, while high internal phase emulsion inks have allowed direct-ink-writing of three-dimensional liquid metal structures. One recent metalgel formulation maintained a conductivity of three million siemens per metre through a million stretching cycles, a durability benchmark that would have seemed unattainable for a fluid conductor only a decade ago.

The applications catalogued in the review span the full breadth of soft electronics. In wearable healthcare, liquid metal electrodes and sensors have been fashioned into electronic tattoos, electromyography patches for tendon localization and muscle injury prevention, and pressure sensors for health monitoring. In implantable and bioelectronic systems, liquid metal microelectrodes have been wafer-patterned for chronic biocompatibility, printed directly on the cranium for soft neural probes, and formed into three-dimensional microelectrode arrays integrated with ultrathin retinal prostheses for vision restoration; liquid metal neuro-interfaces have even been used to stimulate and record from human hippocampal organoids. Phase-transition behavior adds another dimension: temperature-responsive intravenous needles that irreversibly soften on insertion, and biphasic microfibers for minimally invasive implantable electronics, exploit alloys that are rigid at room temperature and compliant at body temperature.

Soft robotics and integrated systems feature prominently as well. Liquid metal–elastomer composites have demonstrated autonomous electrical self-healing, in which damaged circuits reconnect themselves as the liquid metal flows back together, and liquid metal inclusions have enabled shape-morphing elastomers that couple thermal transport with programmable actuation. Stretchable Arduinos embedded in soft robots, octopus-inspired sensorized arms, and stretchable core–shell cables that are patternable, recyclable and noise-resistant all illustrate how liquid metals can bridge soft and rigid electronic domains. Liquid crystal elastomer composites actuated by induction heating point toward untethered, programmable soft machines, while liquid metal antennas exploit fluidic deformability for reconfigurable radio-frequency devices.

The authors are candid about what stands between laboratory demonstrations and real-world deployment. Long-term interface durability and manufacturing precision remain the key translation challenges: devices must survive millions of deformation cycles in wet, biological environments without leaking, delaminating or drifting in performance, and patterning methods must reach the resolution and throughput that industrial electronics demand. Questions of biocompatibility are being actively studied, with gallium’s known antimicrobial activity offering intriguing therapeutic possibilities even as toxicity profiles continue to be mapped. The review’s central message is nonetheless one of momentum: by treating the liquid metal–material interface as the primary design object, rather than an afterthought, researchers now have a coherent strategy for building soft electronics that no longer force a choice between how well a device performs and how gracefully it bends. If that strategy matures, the circuits of the future may not merely sit on the body but move with it, heal with it and, in the case of implants, dissolve the boundary between machine and tissue altogether.

Subject of Research: Design strategies for liquid metal-based soft and stretchable electronics

Article Title: Design strategies for liquid metal-based soft electronics

Article References: Pan, C., Zhang, C., Wang, J., Han, M., CHIU, W. Y. P., Zhao, P., & Dickey, M. D. (2026). Design strategies for liquid metal-based soft electronics. Nature Reviews Electrical Engineering. https://doi.org/10.1038/s44287-026-00335-1

Image Credits: AI Generated

DOI: 10.1038/s44287-026-00335-1

Keywords: liquid metals, stretchable electronics, soft electronics, gallium alloys, interface engineering, wearable devices, implantable bioelectronics, soft robotics, elastomer composites, self-healing materials, printed electronics, dielectric elastomers

The review, led by Jongryeol Yang, Haeun Kwon, Dawon Jeong, and Jin Woong Kim, surveys recent advances in what the authors call nanocellulose interface engineering. Their central message is that cellulose nanocrystals and cellulose nanofibrils, the two principal forms of nanocellulose, already possess the raw ingredients for exceptional emulsion stabilization: natural abundance, biodegradability, high aspect ratios, controllable wettability, and remarkable mechanical strength. What they lack, in their native state, is sufficient hydrophobicity to anchor themselves firmly at oil-water interfaces. The paper describes a growing toolbox of chemical and physical strategies designed to overcome this limitation and unlock applications in pharmaceutical delivery, food preservation, and cosmetic formulation.

To understand why particles can outperform molecules at stabilizing emulsions, the authors turn to a classic piece of colloid science. The adsorption energy of a spherical particle at an oil-water interface follows the relationship E = πr²γ(1 ± cosθ)², where r is the particle radius, γ is the interfacial tension, and θ is the contact angle the particle makes with the interface. Because this energy scales with the square of the particle size, even modest particles experience adsorption energies thousands of times greater than thermal energy, producing what researchers describe as irreversible interfacial anchoring. Once lodged at the boundary between oil and water, a particle essentially cannot be dislodged, which is why Pickering emulsions, named after early twentieth-century observations by Walter Ramsden and Spencer Umfreville Pickering, resist coalescence far better than surfactant-stabilized systems.

Cellulose nanocrystals, or CNCs, present a fascinating paradox. Produced by acid or enzymatic hydrolysis of cellulose fibers, these needle-like particles measure roughly 5 to 20 nanometers across and hundreds of nanometers long, and their surfaces carry negative charges from sulfate groups introduced during processing. That electrostatic repulsion should, in principle, disfavor interfacial adsorption and prevent the close packing needed for robust stabilization. Yet CNCs stabilize emulsions remarkably well, and the review explains why: crystallographic anisotropy. Different crystal faces of a CNC carry different chemistries. The hydrophilic faces, such as the (010) and (110) planes, expose hydroxyl groups and charged species, while the hydrophobic (200) edge planes present minimal polar functionality. When a CNC arrives at an oil-water interface, it orients itself so that its charged faces align with water and its hydrophobic edges dip into the oil, achieving favorable anchoring despite its overall hydrophilic character.

That elegant self-orientation, however, does not solve everything. The same sulfate groups that make CNCs water-soluble also generate intermolecular repulsion that impedes the formation of dense, mechanically strong interfacial networks. One remedy is ionic cross-linking. Simple monovalent salts such as sodium chloride and potassium chloride screen the negative charges, lowering both surface and interfacial tension. More dramatically, divalent metal cations such as zinc nitrate forge genuine cross-links between neighboring nanocrystals. Rheological measurements show that adding divalent metal nitrates transforms CNC suspensions into gel-like materials with enhanced storage and loss moduli, and the resulting three-dimensional networks suppress creaming, aggregation, and coalescence, conferring superior kinetic stability on the emulsions.

Chemical modification offers an even more direct route to better stabilizers. Because cellulose is studded with hydroxyl groups, chemists can graft a wide variety of molecules onto its surface. The review highlights work by Nigmatullin, Xu, and colleagues showing that attaching alkylamine chains of increasing length creates a controlled gradient of surface hydrophobicity. Longer alkyl chains amplify hydrophobic interactions between particles, attenuating electrostatic repulsion and promoting percolated self-associative networks with greater mechanical integrity. Octylamine-modified CNCs substantially reduce surface tension, and cryo-scanning electron microscopy confirms the formation of stable emulsion droplets armored with the modified crystals. In a related approach, Ataeian and colleagues used EDC/NHS coupling chemistry to graft polyamidoamine dendrimers onto CNCs, increasing water contact angles and enabling direct microscopic visualization of how densely the particles assemble on individual droplet surfaces.

Perhaps the most striking demonstration of molecular design comes from Tang and colleagues, who grafted polystyrene chains specifically onto the end groups of CNCs rather than their side surfaces. The result is a surfactant-mimicking architecture in which each particle carries a hydrophilic crystalline body and hydrophobic polymer tails. Emulsions stabilized by these amphiphilic CNCs exhibited exceptional coalescence resistance, maintaining their structural integrity for four months of storage. Such longevity, achieved without any molecular surfactant, illustrates how deliberately engineered particle geometry can rival or exceed conventional emulsifiers while avoiding their toxicity concerns.

Cellulose nanofibrils, or CNFs, behave differently from their crystalline cousins. With diameters of 10 to 50 nanometers and lengths of several micrometers, these flexible filaments do not simply sit at interfaces; they weave them. CNFs form interconnected fibrillary films at oil-water boundaries while simultaneously building three-dimensional networks in the surrounding water, restricting both droplet coalescence and droplet mobility. The review emphasizes that the degree of fibrillation is critical: completely nanofibrillated CNFs adsorb irreversibly onto droplet surfaces and form entanglement networks that raise viscoelastic moduli, whereas incompletely fibrillated material allows droplet deformation and eventual coalescence. Complementary strategies, including TEMPO-mediated oxidation that converts C6 hydroxyl groups into carboxylates and cationic modification with glycidyltrimethylammonium chloride, further tune charge and adhesion, with TEMPO-oxidized CNF emulsions maintaining consistent droplet size distributions for thirty days.

The most advanced engineering targets the remaining weaknesses of CNF films: porosity that lets internal phases leak out, and vulnerability to crystallization-induced destabilization when the encapsulated material is waxy or crystalline. Metal-phenolic network technology addresses the first problem by coating CNF-armored droplets with dense layers of phenolic compounds and metal ions. Park and colleagues validated the mechanism using DLVO theory, showing that the metal-phenolic coating amplifies hydrophobic interaction energies between CNFs and oil droplets, enabling stable emulsions even under low-energy vortexing. The phenolic layer adds antioxidant functionality, protecting oxidatively fragile cargo. For the second problem, metal-organic membranes built from metal cations and organic ligands create comprehensive envelopes around droplets, preventing leakage and confining crystal growth within the droplet interior. These membranes also promote interdroplet association networks that raise bulk viscosity and preserve long-term structural stability, and dual-chain hydrophobically modified CNFs have stabilized high-internal-phase emulsions exceeding 74 volume percent oil.

The authors are candid about the obstacles between laboratory success and industrial reality. Manufacturing nanocellulose at scale remains expensive and energy-intensive, with acid hydrolysis, TEMPO oxidation, and mechanical fibrillation all consuming significant resources, and batch-to-batch variability undermines the reproducibility that commercial products demand. Regulatory frameworks for nanomaterials in food, cosmetics, and pharmaceuticals are still underdeveloped, and comprehensive toxicological data remain scarce. The long-term degradation behavior of nanocellulose-stabilized interfaces under storage conditions is also poorly understood, complicating shelf-life predictions. Still, the review concludes that nanocellulose has already demonstrated remarkable colloidal stability, with reported formulations exceeding one month of ambient storage without phase separation. With greener processing, standardized safety protocols, and scalable formulation design, these plant-derived nanomaterials could transform how industry stabilizes everything from ice cream to injectable drug carriers, replacing a century of surfactant chemistry with engineered wood at the nanoscale.

Subject of Research: Nanocellulose interface engineering for stabilizing Pickering emulsions

Article Title: Advanced nanocellulose interface engineering for Pickering emulsion stabilization

Article References: Yang, J., Kwon, H., Jeong, D., & Kim, J. W. (2025). Advanced nanocellulose interface engineering for Pickering emulsion stabilization. Advances in Industrial and Engineering Chemistry, 1(1), Article 25. https://doi.org/10.1007/s44405-025-00021-0

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00021-0

Keywords: nanocellulose, Pickering emulsions, cellulose nanocrystals, cellulose nanofibrils, interface engineering, emulsion stabilization, surfactants, surface modification, metal-phenolic networks, metal-organic membranes, drug delivery, colloid science

For more than a decade, the standard approach to protecting perovskite solar cells has been planar interface engineering. Researchers deposit thin, flat interlayers of organic molecules, polymers, or inorganic salts between the perovskite absorber and the adjacent charge-transport layer. These interlayers serve two purposes: they chemically passivate dangling bonds and defects at the interface, reducing the recombination of charge carriers, and they act as a kind of glue, interlocking the two layers mechanically. The trouble is that these goals pull in opposite directions. A thicker, denser interlayer bonds the layers together more robustly, but it also adds an insulating barrier that impedes the flow of electrons or holes across the junction. A thinner interlayer lets charges pass freely but offers little mechanical reinforcement. The result has been a persistent trade-off, in which gains in stability come at the cost of efficiency, and vice versa.

The Hong Kong team, led by Yuanyuan Zhou with Pengfei Guo and Wenjian Yu as co-first authors, sidestepped this trade-off by abandoning the flat interlayer altogether. Instead of building a wall between the perovskite and the charge-transport layer, they built bridges through it. Their trans-interface engineering creates vertically aligned, mechanically tough nanolinks that penetrate into both layers simultaneously, anchoring the interface from both sides at once. Because these molecular links are discrete and vertically oriented rather than continuous and planar, they provide mechanical reinforcement without blanketing the interface in insulating material. Charge carriers can still travel across the junction through the unoccupied regions between the nanolinks, while the links themselves hold the two layers together under the thermal and mechanical stresses of operation.

The chemistry behind the nanolinks is a two-step molecular handshake. First, the researchers pre-incorporated two different organic linkers into the device stack: a triple organic linker embedded within the perovskite layer, and a single organic linker distributed in the charge-transport layer. Each linker is designed to integrate into its host layer without disrupting its function. Then came the trigger: the team applied radicals derived from azobisisobutyronitrile, a common free-radical initiator better known in polymer chemistry as AIBN. These cyanoisopropyl radicals initiated polymerization of the two linkers within their respective layers, and, crucially, also bonded the two linker populations to each other vertically at the heterointerfacial contacts. The result is a covalently stitched interface, with polymerized molecular tethers running from the body of the perovskite layer, across the junction, and into the body of the charge-transport layer.

Mechanical testing showed that this stitched interface outperformed other reported interfacial approaches by a wide margin. This matters because mechanical failure, not chemistry alone, has emerged as a leading cause of perovskite device degradation. Metal halide perovskites are soft, brittle ionic crystals, and the repeated thermal cycling, humidity exposure, and mechanical stress of real-world operation cause delamination, cracking, and grain-boundary failure that begin precisely at the heterointerfaces. Previous work from other groups has explored interfacial toughening with self-assembled monolayers, chiral-structured heterointerfaces, and interpenetrating networks, but the trans-interface approach is distinctive in reinforcing the interface from within both layers rather than merely coating it from one side. By suppressing the mechanical failure modes that initiate degradation, the nanolinks address degradation at its root rather than treating its symptoms.

The photovoltaic results are striking. Devices built with the TIE-treated interface achieved power conversion efficiencies of up to 27.04 percent, with an independently certified value of 26.67 percent, placing them among the most efficient perovskite solar cells ever reported. But efficiency records in this field are common; what has been rare is stability delivered reproducibly. Under maximum-power-point tracking at one-sun-intensity illumination, the standard operating condition used to assess how a cell performs while actually generating electricity, 92 percent of the tested devices reached T80 lifetimes of 1,400 hours, meaning they retained at least 80 percent of their initial performance for nearly two months of continuous simulated sunlight. That statistical consistency across a large population of devices is arguably the more important headline, because industrialization depends not on a single champion cell but on thousands of cells that all behave the same way.

The reproducibility stems largely from what the nanolinks prevent. In conventional devices, tiny variations in interface quality from sample to sample translate into wildly different degradation rates, so one cell might last ten times longer than its nominally identical twin. By mechanically reinforcing every interface in the same way, trans-interface engineering narrows that distribution. The team attributes the high reliability chiefly to the suppression of mechanical failure during operation: when the interface cannot delaminate or crack, the chemical degradation pathways that follow mechanical damage never get started. This reframing of stability as a mechanical problem as much as a chemical one echoes a growing consensus in the field, articulated in recent reviews of the mechanical reliability of metal halide perovskites, that fracture and delamination deserve the same attention traditionally reserved for ion migration and moisture attack.

The implications extend well beyond a single efficiency chart. Perovskite solar cells are the leading candidates for next-generation photovoltaics because they can be made cheaply, at low temperatures, on flexible substrates, and in tandem configurations stacked on silicon to break through the efficiency limits of single-junction cells. But investors and module manufacturers have been wary of a technology whose lab champions fade within weeks and whose production batches vary unpredictably. A strategy that simultaneously boosts efficiency, extends lifetime, and tightens the statistical spread of device performance directly addresses the three objections that have kept perovskites out of mass production. The fact that the TIE process relies on well-understood radical polymerization chemistry, compatible with existing solution-processing fabrication, suggests it could be integrated into manufacturing without exotic equipment.

Perhaps the most far-reaching claim in the paper is that trans-interface engineering is not limited to photovoltaics. Multilayered optoelectronic devices of every kind, including organic light-emitting diodes, photodetectors, and perovskite-based transistors, suffer from the same fundamental weakness: dissimilar layers stacked on top of one another form fragile heterointerfaces that fail under stress. A generalizable method for growing vertically aligned molecular links across any such junction, decoupling mechanical reinforcement from charge transport, offers a design principle for the entire field of layered electronics. A US patent has been filed based on the work by Zhou, Guo, and Yu, signaling commercial interest in translating the concept. If the approach survives the transition from laboratory cells to full-size modules and outdoor field testing, the molecular stitching demonstrated here may be remembered as the moment perovskite solar cells stopped being a laboratory marvel and started becoming a product.

Subject of Research: Trans-interface engineering of perovskite solar cell heterointerfaces for efficiency and stability

Article Title: Trans-interface engineering for reliable perovskite solar cells with reproducible stability

Article References: Guo, P., Yu, W., Hao, M., Wang, K., Duan, T., Li, S., & Zhou, Y. (2026). Trans-interface engineering for reliable perovskite solar cells with reproducible stability. Nature Photonics. https://doi.org/10.1038/s41566-026-02007-w

Image Credits: AI Generated

DOI: 10.1038/s41566-026-02007-w

Keywords: perovskite solar cells, trans-interface engineering, nanolinks, power conversion efficiency, operational stability, interface engineering, radical polymerization, mechanical reliability, charge transport, photovoltaics, heterointerfaces, reproducibility

The core problem is well known to anyone following battery science. Conventional lithium-ion cells rely on flammable liquid electrolytes, which limit energy density and pose fire risks. Lithium-metal anodes could dramatically boost capacity, but they react violently with liquid electrolytes and grow needle-like dendrites that can short-circuit cells. Solid polymer electrolytes, typically built from polymers such as poly(ethylene oxide), offer a safer, flexible, and easily processed alternative. Yet at room temperature their ionic conductivity is orders of magnitude too low, their lithium-ion transference number is poor, their mechanical strength is modest, and their electrochemical stability window is narrow. Pure inorganic ceramic electrolytes conduct ions beautifully but are brittle and difficult to mate with electrodes.

The review’s central argument is that composite electrolytes, blending polymer hosts with inorganic fillers, can capture the best of both worlds, but only if the fillers are chosen and engineered intelligently. The authors distinguish sharply between passive fillers such as alumina and titania, which improve conductivity only indirectly by disrupting polymer crystallization and expanding free volume, and active fillers, which are themselves fast ion conductors. Active fillers participate directly in lithium-ion transport, boosting the availability of free lithium ions, enabling conduction along particle surfaces, and interacting with anions to streamline charge movement. Materials such as lithium aluminum oxide and lithium nitride exemplify this class, and the newest generation includes garnet, NASICON, perovskite, and sulfide ceramics.

Each ceramic family brings a distinct personality to the composite. Garnet-type fillers, especially lithium lanthanum zirconium oxide known as LLZO, combine respectable ionic conductivity between 10⁻⁴ and 10⁻³ siemens per centimeter with exceptional electrochemical and thermal stability and a natural talent for suppressing dendrites. NASICON-type fillers such as LATP and LAGP offer robust three-dimensional open frameworks with interconnected diffusion channels, ambient-temperature conductivity near 10⁻³ siemens per centimeter, and stability up to five volts. Perovskite fillers like LLTO conduct lithium ions through abundant A-site vacancies but can suffer interfacial instability against lithium metal. Sulfide fillers, including the celebrated Li₁₀GeP₂S₁₂, reach conductivities of 10⁻³ to 10⁻² siemens per centimeter, rivaling liquids, though they demand careful moisture control and interface engineering.

The review documents how these fillers work their magic through several interlocking mechanisms. By disrupting the periodic ordering of polymer chains, they shrink the crystalline fraction and expand the amorphous phase, where segmental motion is freer and lithium salts dissociate more readily. Because ion conduction in amorphous regions requires activation energies of only 0.45 to 0.60 electron-volts, compared with more than 1.2 electron-volts in crystalline domains, this microstructural shift is decisive. Well-dispersed fillers also create continuous ion-conducting networks and interfacial zones where coordination environments loosen, lowering the barriers to ion hopping. Neutron diffraction and X-ray absorption studies cited in the review show lithium ions at polymer-filler interfaces with reduced coordination numbers, moving faster as a result.

Defect engineering emerges as a particularly striking frontier. Introducing oxygen vacancies into oxide fillers such as Li₄Ti₅O₁₂ at densities between 10¹⁸ and 10²⁰ per cubic centimeter creates Lewis acid centers that strengthen local interactions with lithium ions and generate shallow energy wells that shorten hopping distances. Electron paramagnetic resonance measurements reveal a strong linear correlation between defect concentration and the lithium-ion transference number, with activation energies dropping by 20 to 30 percent. Grain-boundary engineering offers similar gains: confining ceramic grains below 100 nanometers produces amorphous transition layers where diffusion coefficients exceed those in the grain interior by one to two orders of magnitude. Coating LLZO surfaces with tungsten oxide boosted room-temperature conductivity more than sevenfold, reaching 1.1 × 10⁻³ siemens per centimeter.

Concrete demonstrations show how far the strategy has come. In one study highlighted by the review, adding just one weight percent of Li₁₀GeP₂S₁₂ to a self-supporting polymer framework yielded conductivities of 1.2 × 10⁻³ siemens per centimeter at 80 degrees Celsius and a wide electrochemical stability window spanning zero to 5.7 volts. In another, garnet particles embedded in a poly(propylene carbonate) host produced a flexible electrolyte with 5.2 × 10⁻⁴ siemens per centimeter conductivity, a lithium-ion transference number of 0.75, a tensile strength of 6.8 megapascals, and stable operation at low temperature with fast charging capability, a combination rarely achieved simultaneously. Perovskite nanofibers in PVDF-HFP matrices have formed lithium-fluoride-rich protective interphases that stabilize cycling against lithium metal.

Dendrite suppression deserves special attention because it addresses the most feared failure mode of lithium-metal batteries. Stiff filler particles act as physical barriers that mechanically resist dendritic penetration, while the more uniform lithium-ion flux that active fillers promote prevents the localized current densities that nucleate dendrites in the first place. The review also flags an emerging class of halide fillers, including Li₃InCl₆ and Li₃YCl₆, which combine good conductivity and compatibility with high-voltage cathodes, though moisture sensitivity, cost, and weaker mechanical reinforcement remain hurdles. The authors stress that filler selection should weigh conductivity alongside stability, interfacial compatibility, processability, scalability, and cost rather than chasing conductivity numbers alone.

Looking forward, the review charts an ambitious roadmap. Multifunctional fillers refined through doping, defect engineering, and surface chemistry could simultaneously enhance transport, mechanics, and stability. Three-dimensional interconnected filler networks, built by electrospinning, freeze-casting, or additive manufacturing, could shorten diffusion pathways dramatically. Machine learning, molecular dynamics, and density functional theory promise to accelerate the search for optimal polymer-filler pairings, while operando spectroscopy and microscopy are needed to capture the dynamic, cycling-induced evolution of interfaces that ex situ methods miss. Perhaps most critically, the field must move from laboratory-scale demonstrations to roll-to-roll fabrication, solvent-free synthesis, and melt extrusion, while embracing recyclable polymer hosts and environmentally benign filler chemistries. If those threads come together, the humble ceramic nanoparticle may prove to be the quiet hero that finally delivers the safe, high-energy solid-state battery the industry has been waiting for.

Subject of Research: Active ceramic filler engineering in solid polymer electrolytes for solid-state lithium batteries

Article Title: Emerging horizons in active filler engineering for next generation solid polymer electrolytes: a mini review

Article References: Jagan, M., Sreeja, S., Raju, S., & Vijayachamundeeswari, S. P. (2026). Emerging horizons in active filler engineering for next generation solid polymer electrolytes: a mini review. Discover Electrochemistry, 3(1), Article 85. https://doi.org/10.1007/s44373-026-00173-8

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00173-8

Keywords: solid polymer electrolytes, active fillers, solid-state batteries, ionic conductivity, garnet, NASICON, perovskite, sulfide electrolytes, lithium dendrites, interface engineering, lithium-metal batteries, composite electrolytes

Yet a stubborn problem has persisted across nearly every BiVO4 electrode ever fabricated: the material performs very differently depending on which side the light strikes. Because the hole diffusion length in BiVO4 is shorter than 100 nanometers, photogenerated holes created far from the electrolyte interface tend to recombine before they can oxidize water. When light enters through the transparent conductive oxide substrate, a geometry known as back-side illumination, most charge carriers are born close to the substrate where electrons can be collected efficiently, and the measured photocurrent is comparatively high. When light enters directly through the semiconductor surface, front-side illumination, holes generated near the electrolyte interface must travel only a short distance, but electrons generated deeper in the film face a long, lossy journey to the substrate. The result is a pronounced asymmetry, with back illumination routinely outperforming front illumination by a wide margin, a disparity that complicates device design and wastes a portion of the absorbed solar energy.

A research team led by Sarwar Saad, Wonjung Choi, and Yiseul Park at Pukyong National University in Busan, Republic of Korea, has now demonstrated that this direction-dependent behavior can be dramatically reduced with a processing step so simple it borders on the mundane: rinsing. In work published in Advances in Industrial and Engineering Chemistry, the group showed that selectively washing away weakly adhered bismuth particles after electrodeposition produces BiVO4 thin films whose photocurrents under front and back illumination are nearly identical. The finding, published as open access on 9 December 2025, suggests that interface engineering through precursor control may be as important as the more elaborate strategies the field has traditionally pursued.

The fabrication route began with fluorine-doped tin oxide, or FTO, glass substrates that were ultrasonically cleaned in acetone, ethanol, and deionized water. Bismuth was then electrodeposited from a solution of bismuth nitrate and sodium perchlorate dissolved in dimethyl sulfoxide at 80 degrees Celsius, using a pulsed potential of minus 1.4 volts in a three-electrode configuration. The researchers prepared two sets of electrodes. In the first, the bismuth films were simply dried at 100 degrees Celsius and carried forward as deposited. In the second, the films were rinsed sequentially with ethanol and deionized water before drying, a step designed to strip away the loosely bound, overgrown bismuth branches that electrodeposition tends to leave behind. Vanadium was introduced by drop-casting a vanadyl acetylacetonate solution onto the bismuth-coated substrates, and a slow anneal in air at 450 degrees Celsius for three hours converted the stacked precursors into the characteristic yellow BiVO4 phase. A final soak in sodium hydroxide removed unreacted vanadium species.

Scanning electron microscopy revealed just how consequential the rinsing step was. The non-rinsed bismuth precursors displayed the classic signatures of diffusion-limited electrodeposition: dendritic structures at low deposition charges that coalesced into large, irregular aggregates as the passed charge increased to 300 and 500 millicoulombs. Cross-sectional imaging exposed voids at the bismuth-FTO interface, evidence of weak adhesion and uncontrolled crystal growth. After thermal conversion, these defects propagated directly into the BiVO4 layer, which emerged as a coarse, porous film riddled with interparticle voids and separated from the substrate by distinct gaps, a configuration prone to delamination during operation. The rinsed precursors told a different story. With the weakly attached branches removed, the remaining bismuth formed a compact, densely packed, and uniformly distributed layer that remained void-free at the interface even at the highest deposition charge. The converted BiVO4 films inherited this discipline, showing fine grains, tight packing, and a well-defined, gap-free boundary with the FTO substrate.

Optical measurements reinforced the structural picture. Ultraviolet-visible spectrophotometry showed that absorbance in the non-rinsed films climbed steadily with deposition charge, as thicker precursors yielded thicker, more light-hungry BiVO4 layers with a strong absorption edge near 520 nanometers. The rinsed films, by contrast, absorbed less light across the visible spectrum, reflecting their reduced thickness. Crucially, the researchers interpret this lower optical density not as a degradation but as a refinement: by thinning the film, rinsing brought its dimensions closer to the carrier diffusion length intrinsic to BiVO4, optimizing the trade-off between light harvesting and charge collection. The improved transparency of the rinsed films also carries practical appeal for tandem cell architectures, where a semi-transparent top photoanode must allow unused photons to reach an underlying absorber.

The photoelectrochemical tests delivered the headline result. Under back-side illumination in a sulfite electrolyte at pH 7, the non-rinsed BiVO4 electrodes generated photocurrents of roughly 1.5 milliamperes per square centimeter, but their front-side response was far weaker, reproducing the familiar asymmetry that has long plagued the material. The rinsed electrodes collapsed this gap to less than 1 milliampere per square centimeter, delivering nearly identical photocurrents from either direction. Moreover, at equivalent deposition charges, the rinsed films consistently outperformed their non-rinsed counterparts overall, despite absorbing less light. The team attributes this to the compact film-substrate interface formed during rinsing, which facilitates efficient electron extraction from BiVO4 into the FTO, minimizes series resistance, and suppresses the recombination pathways that porous, poorly adhered films inevitably introduce. In effect, the optimized electron transport compensates for the reduced optical thickness, and the electrode becomes genuinely direction-independent.

Durability testing added a further layer of significance. When a rinsed BiVO4 electrode was held at 1.25 volts versus the reversible hydrogen electrode under continuous AM 1.5G illumination, its photocurrent density remained essentially constant for more than five hours, with no noticeable degradation or fluctuation. The authors connect this stability directly to the mechanical and electrochemical robustness imparted by the rinsing step: strong bonding between the BiVO4 layer and the FTO substrate minimizes delamination and crack formation, while the compact, uniform microstructure suppresses photocorrosion and limits the defect sites that typically accelerate degradation during extended operation. For a technology whose commercial prospects hinge on devices surviving thousands of hours in real electrolytes, demonstrating that a simple fabrication modification can deliver both performance and longevity is a meaningful contribution.

What makes the result particularly attractive is what it does not require. Strategies to improve BiVO4 have historically involved dopant incorporation, elaborate nanostructuring, or the loading of oxygen evolution cocatalysts, each of which adds cost, complexity, and process variability. The rinsing strategy, by contrast, is a single additional washing step inserted into an existing electrodeposition workflow, requiring no exotic chemicals, no high-vacuum equipment, and no post-growth surface treatments. The authors position it as a scalable and cost-effective route to direction-independent BiVO4 photoanodes, and the underlying principle, that the morphology and adhesion of the metallic precursor dictate the quality of the final oxide film, is likely transferable to other electrodeposited photoelectrode systems. As solar fuels research matures from laboratory curiosities toward practical hydrogen production, results like this one serve as a reminder that sometimes the most powerful lever in materials engineering is not a new compound or a clever catalyst, but careful control of the interface where the material meets its substrate.

Subject of Research: Interface engineering of BiVO4 photoanodes for balanced front-back illumination performance in photoelectrochemical water splitting

Article Title: Interface-controlled BiVO4 thin films via selective rinsing for balanced front-back illumination performance

Article References: Saad, S., Choi, W., & Park, Y. (2025). Interface-controlled BiVO4 thin films via selective rinsing for balanced front-back illumination performance. Advances in Industrial and Engineering Chemistry, 1(1), Article 36. https://doi.org/10.1007/s44405-025-00034-9

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00034-9

Keywords: BiVO4, photoanode, photoelectrochemical water splitting, solar hydrogen, electrodeposition, interface engineering, selective rinsing, FTO substrate, charge recombination, illumination symmetry, photostability, thin films