According to the study background, liquid electrolytes can undergo oxidative decomposition during prolonged operation, while parasitic reactions at electrode–electrolyte interfaces can contribute to impedance growth and capacity decay. For the experiment, poly(vinylidene fluoride-co-hexafluoropropylene), abbreviated PVDF-HFP, and polyacrylonitrile, or PAN, formed the polymer host. The researchers added LLZTO, a Ta-substituted form of lithium lanthanum zirconate, as an inorganic ceramic filler.

They then prepared two composite membranes by separately introducing LiTFSI or LiODFB. In both formulations, the salt dosage was fixed at 30 wt% calculated from the combined mass of PVDF-HFP and PAN, allowing the two salt identities to be compared within the same general electrolyte design. The formulation designated PSI 30% contained LiTFSI, while the membrane designated PFB 30% contained LiODFB.

PSI 30% combined an ionic conductivity of 6.08 × 10−4 S cm−1 with a tensile strength of approximately 8.5 MPa and a lithium-ion transference number of 0.58. PFB 30% performed less well on the reported mechanical-strength and lithium-ion transport measures. Electrochemical testing was performed in LiFePO₄/CPE/Li cells, which paired a lithium iron phosphate cathode with the composite polymer electrolyte and a lithium-metal anode.

Cells assembled with PSI 30% delivered discharge capacities of 162.61 mAh g−1 at a 0.1 C rate and 107.14 mAh g−1 at 1 C. The lower capacity at the higher rate shows that the membrane’s strong material-level results did not translate into identical discharge performance across the two tested rates. After 100 cycles, the PSI 30% cells retained a capacity above 159 mAh g−1, corresponding to nearly 98% retention.

This is a cell-level result obtained with lithium iron phosphate electrodes, lithium-metal anodes, the tested composite electrolyte and the study’s specified discharge rates. It provides evidence of stable electrochemical performance over the reported 100-cycle test, while the scope of the result remains tied to that laboratory cell configuration and test period. Under the reported conditions, the LiTFSI-containing composite outperformed the LiODFB-containing composite on the stated mechanics and transport measures, and cells using the former sustained nearly all of their capacity through 100 cycles.

The findings support lithium-salt selection as a potential lever for coordinating material properties and cell behavior in PVDF-HFP/PAN/LLZTO composite electrolytes. For battery researchers, the practical appeal of the work is that it compares two salt choices without changing the broad architecture of the composite.

Subject of Research: Effects of lithium-salt identity on composite polymer electrolyte transport, mechanics and cell performance

Article Title: Lithium-salt anion regulation of ion transport and interfacial stability in PVDF-HFP/PAN/LLZTO composite polymer electrolytes

Article References: Ou, Y., Huang, L., Lan, L., Liang, X., Dong, J., Chen, P., Zhang, L., & Mo, Q. (2026). Lithium-Salt Anion Regulation of Ion Transport and Interfacial Stability in PVDF-HFP/PAN/LLZTO Composite Polymer Electrolytes. Frontiers in Chemistry, 14, 1961300. https://doi.org/10.3389/fchem.2026.1961300

Image Credits: AI Generated

DOI: 10.3389/fchem.2026.1961300

Keywords: LiTFSI, LiODFB, polymer electrolytes, lithium-ion batteries, PVDF-HFP, PAN, LLZTO, ionic conductivity, lithium-ion transference, capacity retention, Lithium-salt, anion

The material in question is LiNi0.90Co0.05Mn0.05O2, often abbreviated as NCM90 or simply a high-nickel NCM cathode. With 90 percent of its transition-metal sites occupied by nickel, it delivers a high specific capacity and a strong voltage platform, the two properties that translate directly into longer driving ranges and better energy density for electric vehicles. The trade-off is well documented in the literature. As the nickel fraction climbs, the layered crystal structure that stores lithium becomes increasingly unstable, particularly at high states of charge where the lattice contracts, cracks form, and reactive nickel species are exposed to the liquid electrolyte.

That exposure triggers a cascade of degradation. Electrolyte decomposition products accumulate on the particle surface as a resistive layer, impeding the flow of lithium ions into and out of the cathode. Microcracks admit more electrolyte deeper into secondary particles, accelerating the damage. At elevated temperatures, the reactions run faster and the structural collapse accelerates. Previous studies have attributed the poor cycling of nickel-rich materials to this combination of interfacial parasitic reactions and internal mechanical stress, which is why surface coatings have become one of the most intensively explored remedies in battery research.

Coatings, however, come with a catch. A thick, dense protective layer shields the cathode from the electrolyte effectively, but it also adds resistance in series with the lithium-ion pathway, degrading rate capability. The ideal coating must be thin, chemically robust, electrochemically inert, and somehow favorable to ion transport all at once. The Chinese team addressed this challenge with cerium fluoride, CeF3, applied at just 1.0 weight percent through what the authors describe as a facile in-situ liquid-phase method. The process forms a coating layer roughly 10 nanometers thick, thin enough to barely register on the scale of the cathode particles yet continuous enough to act as a functional barrier.

The electrochemical results are striking. At a moderate cycling rate of 0.3 C and room temperature of 25 degrees Celsius, the CeF3-coated cathode delivered a high initial discharge capacity of 201.71 milliampere-hours per gram. After 200 cycles, the material retained 82.83 percent of its capacity, a figure that stands out for a cathode with such a high nickel content. Capacity fade in uncoated high-nickel materials over comparable cycling windows is typically much more severe, driven by the interfacial reactions the coating is designed to suppress.

High-temperature performance is where the coating truly earns its keep. Batteries in real vehicles rarely enjoy laboratory temperatures; summer heat inside a pack can push cells well above 40 degrees Celsius, and degradation chemistry accelerates sharply with temperature. When the researchers cycled their coated cathode at 0.3 C and 55 degrees Celsius, it retained 83.32 percent of its capacity after 100 cycles. Maintaining that level of retention at elevated temperature suggests the cerium fluoride layer remains a stable, protective interface under conditions that would otherwise rapidly consume an unprotected nickel-rich surface.

Equally important is what the coating did not cost in speed. At a demanding rate of 5 C, meaning a full discharge in roughly twelve minutes, the coated material still delivered 155.76 milliampere-hours per gram. This rate capability underscores the central argument of the paper: the CeF3 layer does more than passivate the surface. According to the authors, the tailored coating establishes a functional barrier that mitigates adverse reactions at the electrode-electrolyte interface while significantly improving lithium-ion diffusion kinetics across the interface. In other words, the coating is not a toll booth on the ion highway but a smoother on-ramp.

The choice of cerium fluoride is chemically deliberate. Fluoride-based coatings are inherently resistant to the acidic species, principally hydrofluoric acid, that form when electrolyte decomposes, making them durable candidates for interfacial protection. Rare-earth fluorides add another dimension, as prior work has explored cerium doping in spinel cathodes and shown that rare-earth elements can confer structural benefits. The in-situ liquid-phase route is also notable for its simplicity: rather than requiring energy-intensive gas-phase deposition, the coating forms directly from solution during synthesis, a process more compatible with the large-scale manufacturing that high-volume battery production demands.

The study positions itself within a crowded field of surface engineering approaches. Aluminum oxide, zirconium oxide, titanium dioxide, lithium phosphates, lithium niobate, and lithium-conducting garnets have all been tested as cathode coatings, each with strengths and limitations. What distinguishes the CeF3 result is the demonstrated balance between interfacial protection and diffusion kinetics, a combination the authors argue is essential for practical adoption. Coatings that protect but slow the cell down simply trade one problem for another, and the 5 C performance reported here indicates the nanometer-scale fluoride layer threads that needle.

The broader significance lies in what it means for the commercial trajectory of high-nickel cathodes. Automotive manufacturers have been pushing nickel content ever higher to squeeze more range out of every kilogram of cell material, but cycle life and thermal robustness remain gating factors for warranty guarantees and fast-charging protocols. A coating that simultaneously improves room-temperature cycling, high-temperature retention, and fast-discharge capability addresses the full spread of real-world stresses. As the authors conclude, this work introduces a novel strategy to mitigate structural instability in high-nickel cathodes, effectively balancing interfacial protection with lithium-ion diffusion kinetics, and thereby accelerating their application in high-performance lithium-ion batteries. If the approach survives the leap from coin cells to full-size pouch cells, a ten-nanometer whisper of cerium fluoride could prove to be one of the quieter breakthroughs in the race for better batteries.

Subject of Research: Cerium fluoride surface coating to enhance the interfacial stability and lithium-ion diffusion kinetics of high-nickel lithium-ion battery cathodes

Article Title: CeF₃-coated LiNi0.90Co0.05Mn0.05O2cathode with enhanced interfacial stability and lithium-ion diffusion kinetics for high-performance lithium-ion batteries

Article References: Yi, J., Zhao, Z., Liu, Z., Song, W., Bao, X., Niu, H., Dong, H., & Wu, C. (2026). CeF₃-coated LiNi0.90Co0.05Mn0.05O2cathode with enhanced interfacial stability and lithium-ion diffusion kinetics for high-performance lithium-ion batteries. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13545-7

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13545-7

Keywords: lithium-ion batteries, high-nickel cathode, NCM90, cerium fluoride coating, interfacial stability, lithium-ion diffusion, capacity retention, electrode-electrolyte interface, energy materials, surface modification, electric vehicles, rate capability

The scale of the improvement reported in the Journal of Materials Science study is striking. After three hundred charge-discharge cycles at a one-coulomb rate, the uncoated NMC811 cathode retained only 53.9 milliampere-hours per gram of capacity. The graphene-modified counterpart, by contrast, still delivered 101.4 milliampere-hours per gram after the same punishing regimen — nearly double the retained capacity. For a coating step as simple as mechanical mixing, the payoff is the kind of leap that battery engineers usually associate with years of formulation fine-tuning. Understanding where that extra stability comes from, however, required the team to look far deeper than conventional electrochemical testing could reach.

The problems afflicting NMC811 are rooted in its chemistry at high states of charge. When the battery is nearly full, most lithium ions have been pulled out of the layered oxide structure, leaving the remaining lattice in a highly oxidised and energetically precarious state. Three intertwined degradation pathways follow. Transition metal ions, particularly nickel, migrate from their assigned octahedral sites into the lithium layers, gradually destroying the ordered structure that allows lithium to move in and out efficiently. The particle surface reconstructs into new phases that impede ion transport. Most dangerously of all, the lattice oxygen itself becomes unstable and can be released from the crystal, a process that not only permanently damages the material but also raises serious safety concerns, since oxygen release at high states of charge feeds into thermal runaway.

To combat these failure modes, the researchers turned to graphene nanoplatelets, thin sheets of conductive carbon a few atoms thick, applied by ball milling — a mechanical process in which the cathode powder and graphene are tumbled together with milling media until the platelets adhere to the particle surfaces. The approach avoids the solvents, high temperatures and complex chemistry required by many other coating strategies, such as the aluminium oxide, cerium oxide, titanium dioxide and lithium niobate coatings explored by other groups. Earlier work had already hinted that carbon coatings can help: reduced graphene oxide wrappings, graphene ball architectures and amorphous carbon layers have all been shown to improve nickel-rich cathodes. What was missing was a rigorous, atom-by-atom account of how the graphene actually interacts with the cathode surface — and that is where the new study sets itself apart.

The team paired a full suite of experimental diagnostics with density functional theory, the workhorse quantum-mechanical method of computational materials science. On the experimental side, electrochemical impedance spectroscopy probed how readily lithium ions and electrons crossed the interface, rate capability tests measured performance under fast charging, and differential capacity curves tracked subtle changes in the phase behaviour of the cathode as it aged. On the computational side, the researchers calculated the charge density difference, the electron localization function, the total and partial density of states, and — perhaps most tellingly — the formation energy of oxygen vacancies at states of charge ranging from zero to sixty-six percent.

Those oxygen vacancy calculations delivered the study’s central insight. Across every state of charge examined, the graphene-coated material exhibited a higher oxygen vacancy formation energy than bare NMC811. In plain terms, it costs more energy to knock an oxygen atom out of the crystal when the graphene layer is present, which means the lattice oxygen is thermodynamically more stable and less inclined to escape during deep charging. Since oxygen release is one of the most damaging and safety-critical degradation pathways in nickel-rich cathodes, shoring up the oxygen framework strikes the problem at its root. This atomistic picture dovetails neatly with the cycling data: the dramatic difference in capacity retention after three hundred cycles is exactly what one would expect if the primary failure mechanism had been substantially suppressed.

The simulations also revealed something unexpected about the nature of the graphene-cathode bond. The charge density difference and electron localization function analyses showed localised charge redistribution at the interface but only weak electronic coupling between the graphene and the underlying oxide — the signature of an interface dominated by van der Waals forces rather than true chemical bonding. This is a subtle but consequential finding. It means the graphene does not merely act as an inert physical barrier sitting on top of the cathode; instead, the weak interfacial interaction is sufficient to perturb the local electronic structure of the nickel-oxygen framework, as confirmed by the partial density of states analysis, while leaving the cathode’s essential chemistry intact. The researchers describe graphene in this role as an interfacial electronic modifier — a material that improves stability not by building a wall, but by tuning the electronic environment of the surface it touches.

The impedance and rate capability measurements fill in the kinetic half of the story, which is where the study’s title earns its mention of interfacial kinetics. Graphene is one of the best electrical conductors known, and wrapping cathode particles in conductive platelets shortens the path electrons must travel and improves the connectivity of the electrode’s conductive network. Better electronic contact at the particle surface means faster charge transfer reactions, lower interfacial resistance and better performance at high charging rates — properties that matter enormously for fast-charging electric vehicles, where sluggish kinetics translate directly into long waits at the charger. The combination of improved kinetics and improved structural stability is what makes the coating strategy attractive from an engineering standpoint: it addresses the two halves of the battery performance equation simultaneously.

Why does this matter beyond the laboratory? Nickel-rich cathodes like NMC811 are at the heart of the push to extend the driving range of electric vehicles while keeping costs down, and they feature in many commercial cell chemistries already on the road. But durability and safety at high states of charge have remained stubborn obstacles, forcing manufacturers into conservative trade-offs between energy density and lifespan. A modification that can be applied with nothing more exotic than a ball mill — equipment already ubiquitous in cathode production plants — could in principle be integrated into existing manufacturing lines with minimal disruption. The study’s mechanistic clarity also hands other researchers a design principle: rather than searching blindly for coatings, they can now target interfaces that raise oxygen vacancy formation energies while maintaining weak, van der Waals-type coupling to the oxide surface.

There are, of course, the usual caveats that accompany laboratory-scale battery research. The results were obtained in coin-cell-type testing over three hundred cycles, a useful benchmark but a far cry from the thousands of cycles and wide temperature ranges that automotive qualification demands. How the graphene layer behaves over years of cycling, in contact with real electrolytes and at commercial electrode loadings, will only become clear through further work. Even so, the convergence of evidence is compelling: nearly doubled capacity retention, a computationally verified stabilisation of the lattice oxygen, and a physically coherent explanation that ties the experimental observations to the electronic structure of the interface. In a field where incremental gains are the norm, a simple carbon veil that teaches a temperamental cathode to hold itself together is the kind of result that could ripple quickly from journal pages into battery factories.

Subject of Research: Graphene nanoplatelet coating to improve the interfacial kinetics and structural stability of Ni-rich NMC811 lithium-ion battery cathodes

Article Title: Boosting the interfacial kinetics and structural stability of Ni-rich lithium nickel manganese cobalt oxide (NMC811) cathodes via graphene modification: a combined experimental and DFT study

Article References: Leong, Y. L., Lim, H. N., Ibrahim, I., Wan Mohd Abd Kalam, W. N., Mot, A. C., Pop, L. C., Hassan, M. R., Chong, W. G., Mohammad Latif, M. A., Ong, S. C., Ng, R. C. K., & Huang, N. M. (2026). Boosting the interfacial kinetics and structural stability of Ni-rich lithium nickel manganese cobalt oxide (NMC811) cathodes via graphene modification: a combined experimental and DFT study. Journal of Materials Science, 61(42), 33256-33278. https://doi.org/10.1007/s10853-026-13734-4

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13734-4

Keywords: NMC811, lithium-ion batteries, cathode materials, graphene nanoplatelets, density functional theory, oxygen vacancy formation energy, capacity retention, interfacial kinetics, structural stability, van der Waals interface, surface coating, electric vehicles

The research team, led by Haiying Yang and corresponding authors Li Wang and Shunri Zheng, set out to solve a persistent problem in electrode engineering. MXenes, a family of two-dimensional transition metal carbides and nitrides first discovered in 2011, are celebrated for their metallic conductivity, hydrophilic surfaces, and layered architecture that can host ions between the sheets. Vanadium carbide MXene, known as V2CTx, is particularly attractive for zinc-ion batteries because vanadium can undergo multielectron redox reactions, potentially delivering high capacities. But the very properties that make MXenes useful also make them fragile: their surfaces are terminated with functional groups, and their layered structure can degrade, restack, or oxidize during processing and cycling, choking off the ion pathways that give the material its electrochemical edge.

To address this, the researchers turned to MXene quantum dots, or MQDs, tiny fragments of the same material measuring just a few nanometers across. Quantum dots derived from MXenes inherit the conductive and redox-active character of their parent material while adding new features: an enormous surface-to-volume ratio, abundant edge sites where reactions can occur, and the ability to anchor themselves onto larger scaffolds. In the composite the team designed, MQDs are generated in situ directly on the V2CTx matrix, producing a hybrid structure in which nanodots with an average particle size of 2.5 nanometers are homogeneously distributed across the MXene sheets. The idea is elegant in principle: the dots act as spacers and active sites that improve ion access, while the underlying MXene framework preserves the conductive highway needed for electrons.

The synthesis method is where the study becomes genuinely striking. Rather than employing multi-step solvothermal reactions or laser ablation, the researchers used a household-scale technology: microwave irradiation. Microwaves heat the reaction mixture volumetrically and almost instantaneously, driving the controlled cleaving of MXene sheets into quantum dots while the surrounding matrix remains largely intact. The critical variable, the team found, is time. By systematically varying the irradiation duration and comparing the resulting structures and electrochemical behavior against pristine V2CTx, they mapped out how the balance between dot formation and framework degradation evolves minute by minute.

The results reveal a classic Goldilocks trade-off. With moderate microwave treatment, uniform MQDs form and anchor evenly on the MXene matrix, and the composite delivers improved capacity retention compared with the untreated material. The dots appear to open up the structure, creating additional pathways and active sites for zinc ion storage while the conductive MXene skeleton remains functional. But when irradiation is extended too long, the story reverses. Excessive exposure degrades the MXene host, undermining the very framework that supports fast electron transport and structural robustness. The electrochemical performance of the over-treated samples falls below that of the optimally treated ones, demonstrating that more processing is emphatically not better processing.

The sweet spot, according to the study, is twenty minutes of microwave irradiation. The sample treated for this duration delivered the best comprehensive electrochemical performance of all the variants tested, achieving what the authors describe as an optimal balance between in situ MQD growth and preservation of the MXene matrix integrity. In other words, at twenty minutes the material gains the benefits of quantum dot decoration without paying the price of structural collapse. The finding elevates irradiation time from a mere procedural detail to a key design parameter, one that can be tuned to modulate MQD formation while safeguarding the architecture of the underlying MXene.

What makes this work notable beyond the specific material system is the conceptual framework it establishes. The authors argue that the dominant factor controlling the electrode’s electrochemical response is not the quantity of quantum dots per se, but the trade-off between quantum-dot generation and matrix preservation. This reframing has implications well beyond V2CTx. Any strategy that introduces nanostructures onto a host material, whether by etching, exfoliation, or irradiation, must contend with the same tension: the process that creates the beneficial features is often the same one that damages the supporting structure. Identifying the crossover point, as this study does with a simple time axis, provides a practical template for other MXene-based and two-dimensional material systems.

The team is also refreshingly candid about the limits of the achievement. The capacity improvement over pristine V2CTx is moderate rather than dramatic, and all samples, including the best performer, still exhibit partial capacity fading within 100 charge-discharge cycles. For a battery technology that aspires to decades of service in stationary storage applications, 100 cycles is a modest benchmark, and the authors explicitly position their findings as useful references for designing advanced MXene-based composite electrodes rather than as a finished solution. This honesty matters in a field where headline-grabbing capacity numbers sometimes obscure poor cycling stability, and it gives the community a clear signal about where future effort must be directed, particularly in stabilizing the MXene framework against long-term degradation.

The broader context underscores why such incremental but rigorous work matters. Aqueous zinc-ion batteries are being pursued worldwide as candidates for safe, inexpensive stationary storage, and research activity spans every component of the cell, from zinc metal anodes and their notorious dendrite problems to electrolyte formulations and cathode architectures. Vanadium-based cathodes, including vanadium oxides and vanadium carbide MXenes, are among the leading contenders because of their high theoretical capacities and tunable structures. Meanwhile, MXene quantum dots are emerging as versatile building blocks in their own right, finding applications in catalysis, sensing, photodetectors, and electromagnetic shielding, in addition to energy storage. The Jilin Normal University study sits at the intersection of these trends, showing that the same microwave technique used to make MQDs can be harnessed to build composite electrodes in a single, time-controlled step.

For battery engineers, the practical takeaway is that processing windows are not incidental. A twenty-minute difference in microwave exposure separates an improved electrode from a degraded one, and the same logic likely applies to other irradiation-based synthesis routes for two-dimensional materials. As the field moves toward commercialization of aqueous zinc batteries, manufacturing-friendly methods that are fast, scalable, and precisely controllable will be essential, and microwave chemistry fits that description well. The study, supported by the Science and Technology Development Project of Jilin Province, demonstrates that with careful parameter optimization, a kitchen-adjacent technology can produce sophisticated nanoscale architectures. The remaining challenge, preserving that architecture over thousands of cycles, will define the next chapter of MXene-based zinc-ion battery research.

Subject of Research: Microwave synthesis of MXene quantum dot composites for aqueous zinc-ion battery cathodes

Article Title: Balancing MQD generation and MXene framework preservation via microwave irradiation time for aqueous zinc-ion batteries

Article References: Yang, H., Zhou, C., Li, J., Han, W., Wang, L., & Zheng, S. (2026). Balancing MQD generation and MXene framework preservation via microwave irradiation time for aqueous zinc-ion batteries. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13894-3

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13894-3

Keywords: aqueous zinc-ion batteries, MXene, MXene quantum dots, V2CTx, microwave irradiation, cathode materials, energy storage, electrochemistry, two-dimensional materials, capacity retention, nanocomposites, vanadium carbide

The team synthesized a carbon-coated version of the compound, NFPP/C, using a gel-combustion method, a synthesis route prized for its simplicity and scalability. The in-situ carbon coating serves a dual purpose: it improves the electronic conductivity of what is otherwise a relatively insulating phosphate framework, and it helps stabilize the electrode surface during repeated cycling. This combination is critical for polyanionic cathodes, whose inherently poor electronic transport has historically limited how fast they can be charged and discharged without sacrificing storage capacity.

What makes the new study scientifically compelling is the mechanism the researchers uncovered. When the NFPP/C electrode is first cycled in an aqueous lithium nitrate electrolyte, it does not initially behave as a lithium-ion host. Instead, the initial cycles trigger a gradual ion-exchange process in which lithium ions from the electrolyte replace sodium ions within the polyanionic structure. The team confirmed this structural transformation using ex-situ X-ray diffraction, which revealed the evolving crystalline phases as the exchange progressed. Only after this conditioning period does the electrode settle into a stable redox regime corresponding to genuine lithium-ion insertion and de-insertion from the framework.

Once that stabilization was achieved, the performance was striking. The electrode delivered a highly stable specific capacity of approximately 117 milliampere-hours per gram at a scan rate of 20 millivolts per second, a figure close to the theoretical capacity predicted for the compound. For context, capacities measured at such high scan rates reflect the material’s ability to operate under fast-charging conditions, so reaching near-theoretical values at speed is a meaningful benchmark rather than a laboratory curiosity achievable only at impractically slow rates.

The comparison with sodium storage revealed an intriguing split personality in the material. When tested for sodium-ion storage in an analogous aqueous sodium nitrate electrolyte, the same composite delivered a comparable capacity of 122 milliampere-hours per gram at the 20 millivolts per second scan rate. But when the researchers varied the scan rate, the two ions behaved differently in ways that illuminate the underlying physics. At low scan rates of 1 millivolt per second, lithium storage outperformed sodium storage, delivering 128 versus 118 milliampere-hours per gram. At high rates of 50 millivolts per second, the ranking flipped, with sodium pulling ahead at 97 versus 79 milliampere-hours per gram.

The explanation lies in the balance between two competing factors: the intrinsic thermodynamics of ion insertion and the kinetics of ion transport through the electrolyte and the electrode. Lithium ions are smaller and carry a higher charge density, which favors their insertion into the framework when time is not a constraint. Sodium ions, by contrast, are larger but benefit from the openness of NFPP’s three-dimensional polyanionic framework, and at high scan rates the ionic conductivity of the electrolyte becomes the determining factor, allowing the more diffusively mobile sodium ions to win. Chronopotentiometry measurements, which track the voltage response of the electrode under constant current, showed the same trend, reinforcing the reliability of the observation across two independent electrochemical techniques.

Long-term cycling tests over more than 100 cycles in both lithium nitrate and sodium nitrate solutions added a further layer of nuance. Capacity retention proved better in the lithium nitrate electrolyte, suggesting that the lithium-conditioned structure is somewhat more robust under repeated insertion and extraction. However, the cycling data also indicated that both lithium and sodium ions are co-inserted during operation rather than acting in strict isolation. This co-insertion behavior means the electrode does not behave as a pure single-ion intercalation host in practice, a detail that will matter for engineers designing cells around this chemistry but which also underscores the flexibility that makes the material attractive.

The broader significance of the work lies in what it says about the dual Na-Li functionality of NFPP/C in aqueous systems. A cathode that can operate with either ion, or with a mixture of both, gives battery designers an unusual degree of freedom. Water-based electrolytes are inherently non-flammable, inexpensive and tolerant of manufacturing imperfections that would be dangerous in organic-solvent cells, and pairing them with an earth-abundant iron phosphate cathode pushes the chemistry toward the low-cost, safe, sustainable end of the battery spectrum that grid storage and stationary applications demand.

The result also connects to a vigorous research frontier. Polyanionic cathodes have emerged as leading candidates for next-generation sodium batteries precisely because their rigid frameworks can be tuned through phosphate and pyrophosphate building blocks to stabilize multiple redox couples, and iron-based compositions avoid the cobalt and nickel supply chains that plague conventional cathodes. The new study extends that logic by showing that the same framework, already proven in commercial sodium cells, can be repurposed for lithium chemistry in water, effectively letting one material serve two distinct battery ecosystems.

Challenges remain before such aqueous dual-ion chemistry reaches commercial hardware. The ion-exchange conditioning period must be understood and controlled during cell manufacturing, the co-insertion of mixed ions will need to be managed to guarantee predictable long-term performance, and the modest capacities of polyanionic materials still trail the best organic-electrolyte cathodes in energy density. Yet the study provides a clear proof of concept: a commercially established sodium cathode, synthesized by a simple combustion route, can approach its theoretical capacity while storing lithium ions in water. For a field racing to make batteries safer, cheaper and more sustainable, that is a result worth watching closely.

Subject of Research: Lithium and sodium ion storage in Na4Fe3(PO4)2(P2O7)/C cathodes in aqueous electrolytes

Article Title: Electrochemical behaviour of Na4Fe3(PO4)2(P2O7)/C in an aqueous Li+ electrolyte

Article References: Gezović-Miljanić, A., Mišurović, J., Grudić, V., Dominko, R., & Vujković, M. (2026). Electrochemical behaviour of Na4Fe3(PO4)2(P2O7)/C in an aqueous Li+ electrolyte. Ionics. https://doi.org/10.1007/s11581-026-07475-2

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07475-2

Keywords: aqueous batteries, NFPP, cathode material, sodium-ion battery, lithium-ion storage, polyanionic cathode, gel-combustion synthesis, ion exchange, iron phosphate, capacity retention, mixed ion insertion, energy storage

The strategy, developed by Yanni Li, Zhigui Zhang, Yu Chen, and colleagues under the supervision of corresponding authors Dan Wang and Zhiyuan Wang, hinges on constructing a dual-function surface coating composed of lithium phosphate, Li3PO4, and a spinel phase directly on the surface of the LRMO particles. What makes the approach remarkable is its economy: ammonium dihydrogen phosphate, NH4H2PO4, serves as the sole precursor. During a facile thermal treatment, this single compound orchestrates the simultaneous formation of two structurally distinct surface layers, each tackling a different failure mode of the cathode. No exotic reagents, no multi-step deposition sequences, no vacuum processes—just one salt, one heat treatment, and a carefully tuned chemistry.

The electrochemical results are impressive. The optimized sample, designated LP-1% for its one percent precursor loading, retains a discharge capacity of 194 milliampere-hours per gram after 200 cycles at a demanding 1C rate, corresponding to a capacity retention of 94 percent. For context, untreated pristine LRMO particles typically bleed capacity far more rapidly under identical conditions, and their voltage curves sag in ways that erode the usable energy of a full battery pack. The coated material also shows significantly improved rate capability, meaning it can deliver its charge faster without collapsing—a property that matters enormously for electric vehicles that need to accelerate and fast-charge.

To understand why the coating works, it helps to dissect the two layers independently. The outer Li3PO4 layer acts as a chemical shield. In an uncoated LRMO, the highly reactive surface of the cathode particle is in direct contact with the liquid electrolyte, and at the high operating voltages these materials demand, that contact triggers a cascade of parasitic side reactions. Electrolyte decomposition products build up, oxygen atoms escape from the lattice, and the surface gradually transforms into an electrochemically dead layer. The Li3PO4 coating interrupts this process by physically isolating the active material from the electrolyte, suppressing the interfacial side reactions that would otherwise consume both lithium inventory and electrolyte over hundreds of cycles.

The inner spinel phase performs a subtler but equally vital role. Spinel-structured oxides offer three-dimensional channels through which lithium ions can diffuse rapidly, in contrast to the more constrained pathways of the layered rock-salt structure that dominates the LRMO bulk. By converting the outermost shell of each particle into spinel, the treatment effectively builds a fast-ion highway around every grain, explaining the improved rate performance. Even more importantly, the spinel shell reduces the unit cell volume change that the particle experiences as lithium ions shuttle in and out during cycling. Repeated expansion and contraction is what drives mechanical fatigue in cathode particles: microscopic cracks nucleate, propagate, and eventually fracture the particle into electrically disconnected fragments. By damping this volume change, the spinel layer substantially mitigates particle cracking and the structural degradation that follows.

The synergy between the two layers is the conceptual heart of the work. Interfacial instability and bulk structural decay have traditionally been treated as separate problems requiring separate solutions—perhaps a protective oxide here, a dopant there. The NH4H2PO4 treatment demonstrates that a single, well-chosen precursor can address both simultaneously, because the phosphate chemistry naturally yields a lithium-ion-conducting insulator while the reaction with the underlying oxide reconstructs the surface into the spinel framework. The authors also note that the coating suppresses oxygen release from the lattice and intergranular cracking, two processes that are tightly coupled: when lattice oxygen escapes at high voltage, it leaves behind vacancies and structural disorder that weaken the particle and accelerate voltage decay.

The significance of this work is amplified by the broader context of battery materials research. Cobalt has become the industry’s problem child: its supply chain is concentrated in politically unstable regions, mining practices raise serious human rights concerns, and its price volatility destabilizes cell economics. Cobalt-free lithium-rich manganese-based oxides sidestep all of these issues while offering capacities that exceed conventional layered cathodes by a wide margin, thanks in part to the participation of anionic oxygen redox in charge storage. But the very oxygen redox chemistry that grants LRMOs their high capacity is also the source of their instability, because highly oxidized lattice oxygen is prone to irreversible loss. Surface engineering strategies like the one reported here are therefore among the most actively pursued routes to making these materials practical, and the field has seen a wave of related approaches, from alumina and lithium aluminate coatings to aluminum phosphate dual shells and lithium titanate or lithium zirconium phosphate modifications.

What distinguishes the new study within this crowded landscape is the in situ character of the coating. Many conventional coating methods deposit a foreign material onto pre-synthesized cathode particles, which raises questions about adhesion, uniformity, and unwanted interfacial reactions between coating and substrate. An in situ treatment, by contrast, grows the protective layers out of the cathode’s own surface chemistry, ensuring intimate contact and structural compatibility. The result is a coating that is not merely painted on but integrated into the particle, which likely explains why the LP-1% sample outperforms both the pristine material and the other coating loadings tested in the study—too little precursor leaves the surface exposed, while too much presumably adds resistive dead weight.

The research was carried out at the School of Materials Science and Engineering at Northeastern University in Shenyang and the School of Resources and Materials at Northeastern University at Qinhuangdao, with support from the Key Laboratory of Dielectric and Electrolyte Functional Material of Hebei Province. Funding came from the National Natural Science Foundation of China, the Hebei Natural Science Foundation, the Fundamental Research Funds for the Central Universities, and several provincial and university programs. The team’s earlier publications reveal a sustained campaign against LRMO degradation mechanisms, including work on spinel-carbon composite coatings, oxygen vacancy and stacking fault engineering, and dual-element substitution strategies to suppress voltage decay—efforts that have now converged on this streamlined single-precursor solution.

For the battery industry, the practical appeal is obvious. A coating process that requires only ammonium dihydrogen phosphate and a thermal treatment slot could, in principle, be grafted onto existing cathode manufacturing lines with minimal capital investment, unlike approaches that demand atomic layer deposition equipment or multiple sintering steps. If the 94 percent capacity retention over 200 cycles can be extended to the thousands of cycles demanded by electric vehicle warranties, and if the voltage stability proves durable at the pack level, cobalt-free lithium-rich manganese cathodes could finally graduate from laboratory curiosity to commercial contender. The work is a reminder that in materials science, the most transformative advances sometimes arrive not as exotic new compounds but as clever, economical treatments that coax existing materials into behaving like the versions we always hoped they could be.

Subject of Research: In situ surface coating of cobalt-free lithium-rich manganese-based cathode materials for lithium-ion batteries

Article Title: In situ construction of surface coating for boosting the electrochemical performance of cobalt-free Li-rich Mn-based cathode

Article References: Li, Y., Zhang, Z., Chen, Y., Zheng, R., Wang, D., Song, Z., Sun, H., Liu, Y., & Wang, Z. (2026). In situ construction of surface coating for boosting the electrochemical performance of cobalt-free Li-rich Mn-based cathode. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13804-7

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13804-7

Keywords: lithium-ion batteries, cathode materials, lithium-rich manganese oxide, cobalt-free, surface coating, Li3PO4, spinel phase, voltage decay, capacity retention, electrolyte interface, NH4H2PO4 precursor, energy storage