Researchers led by Siti Nor Hafiza Mohd Yusoff of Universiti Teknologi MARA in Malaysia systematically examined what actually happens when rutile titanium dioxide nanoparticles, with a nominal size below 100 nanometers, are dispersed into PEO and into PEO loaded with lithium perchlorate, one of the classic polymer-salt electrolyte systems. Their findings, published in Discover Industrial Chemistry and Materials, are striking in their consistency: across every composition tested, the nanofiller behaved as an essentially inert passenger. It did not change the glass transition temperature, the heat capacity step, the crystallinity, the melting behavior, the spherulitic morphology, or the ionic conductivity of the host matrix. The particles simply sat there, largely untouched by and un-touching of the polymer around them.

The team prepared free-standing films by solution casting, dissolving PEO, lithium perchlorate, and titanium dioxide in acetonitrile, stirring for 24 hours at 50 degrees Celsius, and then homogenizing the mixture with an Ultra-Turrax at 5000 rpm to minimize agglomeration. The salt concentration was deliberately fixed at a mass fraction of 0.107, a composition thoroughly characterized in the group’s earlier work, so that any observed changes could be attributed cleanly to the nanofiller rather than to shifting polymer-salt interactions. Filler mass fractions ranged from zero up to 0.043 in the ternary system, and every film was carefully dried and thermally annealed to erase any history from the preparation process.

Differential scanning calorimetry provided the first line of evidence. The glass transition temperature of the PEO-lithium perchlorate system dropped from 243 K to roughly 235 K upon the very first addition of titanium dioxide, a shift the authors attribute to a slight weakening of ion-dipole interactions between the polymer and the salt. But beyond that initial step, further increases in filler content produced no significant change whatsoever in the glass transition, the change in heat capacity at the transition, the apparent melting temperature, or the degree of crystallinity, which was calculated against the reference enthalpy of 188.3 joules per gram for perfectly crystalline PEO. In a genuinely miscible system, adding a second component should depress the melting point and reshape the thermal signature of the host. Here, nothing of the sort occurred, a hallmark of phase separation and weak molecular interaction.

The heat capacity data carried particular weight. Because the glass transition reflects the configurational entropy and segmental freedom of amorphous polymer chains, a filler that actively modified the matrix would alter both the transition temperature and the magnitude of the heat capacity step. The researchers normalized their measured values to account for the amorphous fraction of PEO, subtracting the crystalline phase from the total polymer mass, and found the normalized values essentially flat across all filler loadings, with experimental errors below three percent. The mobile amorphous fraction of the polymer, in other words, was preserved intact. The titanium dioxide neither restricted chain motion nor unlocked additional mobility, suggesting it never meaningfully penetrated or perturbed the amorphous regions where ion transport takes place.

Polarized optical microscopy told the same story visually. At room temperature, well below the melting point of PEO at about 65 degrees Celsius, the films displayed the familiar bright spherulitic crystals embedded in dark amorphous regions. Adding even a small amount of filler, at a mass fraction near 0.0089, coarsened the spherulites and increased the apparent nucleation sites, yet the fibrillose architecture of the spherulites remained largely undisturbed. At higher loadings, around 0.043, dark agglomerated patches of titanium dioxide appeared in the matrix, but these micro-scale clusters sat within the polymer without disrupting its crystalline superstructure. The morphology confirmed what the calorimetry implied: an immiscible, phase-separated composite in which the filler and the polymer coexist without meaningful dialogue.

Electrochemical impedance spectroscopy, measured at 25 degrees Celsius from 50 hertz to 1 megahertz with stainless steel blocking electrodes, completed the picture. The Nyquist plots showed the characteristic depressed semicircle and low-frequency spike of a polymer electrolyte dominated by electrode polarization, and equivalent circuit fitting extracted bulk resistance, bulk capacitance, double-layer capacitance, and Warburg impedance elements. The bulk resistance shifted only marginally with increasing filler content, producing conductivities in the same order of magnitude, from 10⁻⁶ to 10⁻⁷ S cm⁻¹, as the filler-free PEO-lithium perchlorate baseline. Bode analysis of the characteristic frequencies of minimum and maximum impedance, along with the crossover frequency marking the onset of dipole percolation, revealed relaxation behavior that stayed within experimental error regardless of loading, reinforcing the conclusion that the nanofiller left the ion transport pathways untouched.

The dielectric analysis added mechanistic depth. The real part of the complex permittivity, which reflects energy storage through dipole polarization, rose steeply at low frequencies due to interfacial polarization at the electrodes, but the addition of titanium dioxide did not promote this polarization. At high frequencies near 10⁶ hertz, the dielectric constant settled to values that showed insignificant variation across all filler fractions. The exponent extracted from the power-law decay of dielectric loss, which distinguishes ideal Debye relaxation with a single time constant from the distributed relaxation typical of heterogeneous systems, remained constant within error. The loss tangent peaks diminished slightly in magnitude and shifted marginally to lower frequencies as filler content increased, indicating a modest reduction in the number of relaxing dipoles, but the overall relaxation landscape was essentially unchanged. Charge transport, the authors conclude, is governed by the molecular interactions among the charged entities of the PEO-lithium perchlorate complex itself, not by any polymer-filler interfacial chemistry.

Why does this matter, and why does it contradict so much of the published literature? Many studies have reported conductivity enhancements from titanium dioxide in PEO electrolytes, typically attributed to Lewis acid-base interactions between surface groups on the nanoparticles and the polymer or salt, which reduce crystallinity and promote ion dissociation. But those outcomes depend critically on nanoparticle surface chemistry, loading, salt type and concentration, polymer molecular weight, preparation route, and dispersion quality. In this study, untreated rutile particles with weak interfacial interaction and a tendency to agglomerate offered little effective surface area for such chemistry to occur. The result is a sobering reference point: nanofiller addition does not inherently guarantee improved electrolyte performance, and the field’s enthusiasm for ceramic additives must be tempered by a clear-eyed assessment of whether genuine polymer-filler interactions actually form.

The practical message for battery designers is twofold. First, establishing strong, deliberate polymer-nanofiller interactions, through surface functionalization or carefully matched chemistry, is essential if fillers are to do real work in solid polymer electrolytes; simply mixing in nanoparticles is not enough. Second, the combined DSC, microscopy, and impedance methodology demonstrated here offers a rigorous template for verifying whether a given filler is an active modifier or an inert bystander in any candidate electrolyte system. As solid-state batteries edge closer to commercial reality, distinguishing the fillers that genuinely enhance ion transport from those that merely add mass will be crucial for rational materials design. This study, by carefully documenting a case of near-perfect inertness, provides exactly the kind of negative result that helps the field calibrate its expectations and redirect its efforts toward interfaces that truly matter.

Subject of Research: The role of titanium dioxide nanofillers in PEO-lithium perchlorate solid polymer electrolytes

Article Title: Inertness of titanium dioxide nanofillers in polyethylene oxide and lithium perchlorate polymer electrolytes

Article References: Inertness of titanium dioxide nanofillers in polyethylene oxide and lithium perchlorate polymer electrolytes. (n.d.). https://doi.org/10.1007/s44508-026-00024-9

Image Credits: AI Generated

DOI: 10.1007/s44508-026-00024-9

Keywords: solid polymer electrolytes, poly(ethylene oxide), titanium dioxide, nanofillers, lithium perchlorate, ionic conductivity, differential scanning calorimetry, electrochemical impedance spectroscopy, dielectric relaxation, glass transition, crystallinity, lithium batteries

The research team, led by Huixin Wang and Hui Ren of Nanjing University of Science and Technology, tackled a long-standing dilemma in the field of controllable solid propellants, or CSPs. These materials are designed for non-self-sustaining combustion: they burn only while external energy is applied, and they extinguish the moment that energy is withdrawn. The catch is that external energy input steals from a satellite’s limited power budget. The ideal propellant would release plenty of chemical heat of its own while still refusing to burn uncontrollably, a balance that has proven difficult to strike. Formulations that store too much chemical energy tend to slip into self-sustaining combustion, defeating the purpose of control.

The team’s formulation centers on lithium perchlorate trihydrate as the oxidizer, polyvinyl alcohol as the binder, and boron in place of the aluminum powder traditionally used as a high-calorific-value fuel. Each choice solves a specific problem. Lithium perchlorate is less toxic and more thermally stable than hydroxylamine nitrate, a common alternative oxidizer, and its crystalline water stores much of the liquid water that CSPs need as a conductive medium, locking it safely inside crystals rather than leaving it free to freeze or evaporate in vacuum. Its decomposition is endothermic, absorbing 158.275 kilojoules per mole, which helps keep the combustion non-self-sustaining.

Boron brings two decisive advantages over aluminum. First, it packs a higher calorific value and, crucially, does not react with water, eliminating the compatibility problems that plague aluminum in the wet, ionic-salt environment of electrically controlled propellants. Second, the boron oxide layer on each particle dissolves in water to form boric acid, which cross-links the polyvinyl alcohol into a stronger three-dimensional network. That structural reinforcement proved vital in cold conditions: at minus 40 degrees Celsius, the boron-containing propellant showed a 10.7 percent higher compressive strength and a 48.5 percent higher elastic modulus than the boron-free control. The dark, rough boron powder also slashed the material’s reflectance to an 808-nanometer laser from 69.5 percent down to just 17.8 percent, meaning the propellant absorbs laser energy efficiently without any added carbon black.

Pure boron burns incompletely, leaving residues that can clog electrodes and block laser beams, so the researchers blended it with molybdenum powder in a 9-to-1 mass ratio, drawing on their earlier work showing that molybdenum promotes boron combustion by generating oxygen vacancies. Thermal analysis confirmed the benefit: under argon, the boron-containing formulation released 24 percent more heat, at 2555.4 joules per gram versus 2060.9, and its decomposition activation energy dropped by roughly 56 kilojoules per mole. Time-resolved flame spectra showed lithium emission lines appearing first, confirming that oxidizer decomposition initiates ignition, followed by the characteristic BO2 signature of burning boron and the green flame that gives boron propellants their visual trademark.

Manufacturing was its own challenge. Conventional CSP production requires pouring a dilute aqueous solution into a mold and waiting five to seven days for water to evaporate and cross-linking to complete, during which dense additives like metal powders settle under gravity and bubbles and shrinkage mar the final bulk. The team’s rapid process instead mixes solids with minimal water, heats the sealed mixture at 70 degrees Celsius for one hour to form a pliable gel, extrudes it, dries it exposed for 24 hours, then softens and re-extrudes it into a regular cylinder. Total curing time: one day. X-ray tomography showed dense, defect-free bulks with no gravity-driven density gradients, and the process can produce columns with a length-to-diameter ratio of 4 to 1, something the old pouring method could not manage.

Electrically controlled testing revealed the propellant’s throttle behavior in detail. As applied voltage rose from 100 to 200 volts, ignition delay shortened, burning rate climbed, and ignition energy consumption fell, because stronger current heats the bulk faster and accelerates oxidizer decomposition. The boron-containing propellant burned 31 percent faster than the boron-free version at 100 volts and 11 percent faster at 200 volts. The researchers also untangled a puzzling current surge seen during ignition: by substituting inert lithium chloride for the oxidizer and observing the same surge, they showed it stems purely from water detaching from the polymer grid and dissolving ionic salts to form a conductive path, not from any chemical decomposition.

Environmental testing is where the new formulation truly separates itself. Across temperatures from minus 30 to plus 55 degrees Celsius and pressures from 3 kilopascals to 0.85 megapascals, the boron-containing propellant ignited reliably and extinguished on command without structural damage. The boron-free control, by contrast, cracked apart at minus 30 degrees as freezing water expanded inside it, and at 55 degrees it softened so badly that it deformed into the electrode holes and self-extinguished. At 0.85 megapascals the control even slipped into uncontrolled self-sustaining combustion. In low-pressure tests at 200 volts, the boron propellant burned 43.3 percent faster than the control, retaining its energy advantage where satellites actually operate.

Repeated start-stop cycles worked smoothly in both control modes. Under 200-volt electrical stimulation, four ignition-extinguishment cycles drove ignition delay down from 1.80 to 0.52 seconds and ignition energy from 1214 to 314 joules as residual heat and established ion pathways sped each restart. The team also demonstrated an energy-saving operating mode of high-voltage ignition followed by low-voltage maintenance, finding the minimum maintenance power for the boron propellant was 117 watts, 30.3 percent lower than the control’s 168 watts, thanks to its greater self-generated heat. Under a 25-watt 808-nanometer laser, ignition delays reached millisecond scale, and five rapid laser cycles cut ignition delay from 130 to 48.75 milliseconds. Laser mode offers faster response but lower energy output, since only the irradiated end heats up, while electrical mode heats the whole bulk and delivers higher burning rates.

The authors acknowledge that response times remain longer than ideal and that smoke interferes with laser ignition at high pressure, but they see clear paths forward: optimizing grain geometry to cut resistance and reformulating to reduce condensed products. For the rapidly growing constellation of small satellites needing simple, restartable, throttleable propulsion, a solid propellant that answers to both a wire and a beam of light, survives deep cold and near-vacuum, and cures in a single day could mark a genuine shift in how spacecraft maneuver.

Subject of Research: Boron-containing combustion-controllable solid propellants with dual electric and laser response for satellite propulsion

Article Title: Boron containing combustion controllable solid propellant with multi-modal response to voltage & laser

Article References: Wang, H., Ren, H., Xu, J., Xiao, G., & Yu, L. (2026). Boron containing combustion controllable solid propellant with multi-modal response to voltage & laser. Results in Engineering, 32, Article 113322. https://doi.org/10.1016/j.rineng.2026.113322

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113322

Keywords: controllable solid propellant, boron fuel, lithium perchlorate, electrically controlled propellant, laser ignition, space propulsion, low Earth orbit satellites, polyvinyl alcohol binder, non-self-sustaining combustion, burning rate control, thermal decomposition, multiple start-stop

The motivation stems from a well-known weakness of conventional lithium-ion batteries. Since their commercial debut in 1991, these devices have relied on flammable liquid organic carbonate electrolytes that permit uneven lithium flux and the growth of metallic dendrites, structures that can pierce the separator, trigger internal short circuits, thermal runaway, and in extreme cases fire or explosion. Solid-state electrolytes act as a physical barrier to dendrite growth and are widely regarded as the safest long-term solution. Inorganic ceramic conductors achieve superb conductivities between 10⁻³ and 10⁻² S cm⁻¹ but are brittle, hard to process at scale, and suffer from high interfacial impedance. Polymer electrolytes, by contrast, are flexible and electrode-compatible but typically conduct at a sluggish 10⁻⁷ S cm⁻¹, a gap the new work sets out to narrow using sustainable materials.

Composite polymer electrolytes, which disperse a secondary filler into a polymer host, have long been used to push conductivity upward. Fillers suppress polymer recrystallization, create amorphous regions and grain boundaries, and promote salt dissociation through Lewis acid-base interactions. Yet most polymer hosts studied to date, including polyethylene oxide, poly(methyl methacrylate), PVDF, polyacrylonitrile and poly(vinyl alcohol), derive from fossil feedstocks and are not biodegradable. Biopolymers offer a striking alternative: cellulose, chitosan, lignin and starch are abundant, renewable, nontoxic and richly decorated with polar hydroxyl and ether groups that can coordinate lithium ions and host high salt loadings. Corn starch in particular, composed of roughly 20 to 30 percent linear amylose and 70 to 80 percent branched amylopectin linked by alpha glycosidic bonds, is cheap, lightweight and compatible with ionic salts, making it an attractive host for solid electrolyte research.

The researchers fabricated their films by solution casting. Corn starch was dispersed in a dilute acetic acid solution at 80 °C, lithium perchlorate was added in concentrations from 20 to 50 weight percent, and the mixtures were stirred, cast onto Teflon dishes and dried under vacuum to yield free-standing membranes roughly 140 micrometers thick. Electrochemical impedance spectroscopy identified 40 weight percent salt as the optimum: below that limit, conductivity rose with charge carrier concentration, while above it undissociated salt accumulated and impeded ion motion. Building on that baseline, the team introduced Pluronic, a PEG-PPG-PEG triblock copolymer, at 10 to 30 weight percent, and finally dispersed graphene oxide, synthesized by the modified Hummers method, at loadings of 0.1 to 0.7 weight percent into the best plasticized formulation.

Fourier transform infrared spectroscopy revealed exactly what each additive does to the starch structure. The ratio of the crystalline band at 993 cm⁻¹ to the amorphous band at 1015 cm⁻¹, a standard order parameter, fell from 1.24 for neat starch to 0.98 with salt, then to 0.69 after Pluronic addition and to 0.65 once graphene oxide was incorporated. Peak shifts and broadening across the fingerprint region confirmed complexation between lithium ions and the starch oxygen atoms, while the gradual disappearance of the band at 1366 cm⁻¹ signaled progressive disruption of crystalline order. The result is a predominantly amorphous matrix in which polymer chain segments can move freely, a prerequisite for fast ion hopping through the electrolyte.

Perhaps the most elegant finding involves the perchlorate anion band near 623 cm⁻¹. By deconvoluting the overlapping peaks corresponding to free perchlorate and contact ion pairs, the authors quantified the fraction of dissociated salt in each film. That fraction climbed steadily as Pluronic and then graphene oxide were added, providing direct spectroscopic evidence that both additives actively break lithium-perchlorate ion pairs. Pluronic is no ordinary diluent: because its PEG and PPG segments contain ether oxygens that coordinate lithium ions, it participates directly in conduction pathways while also softening the film. Graphene oxide, with its dense surface population of hydroxyl and carboxyl groups, interacts with the salt through Lewis acid-base chemistry and creates low-energy percolation channels at the polymer-filler interface. Both effects multiply the population of mobile charge carriers.

The electrical measurements tell a consistent story. Room-temperature conductivity climbed from the salt-only baseline to 1.33 × 10⁻⁵ S cm⁻¹ at the optimal 20 weight percent Pluronic loading, and then to 3.55 × 10⁻⁵ S cm⁻¹ with 0.5 weight percent graphene oxide, roughly triple the plasticized value. Beyond 0.5 percent, graphene oxide sheets aggregate into insulating barriers that disrupt the conduction network, a phenomenon the group had documented previously in PVDF-HFP/Pluronic blend systems. Temperature-dependent impedance from 20 to 80 °C showed classic Arrhenius behavior, with conductivity reaching 6.45 × 10⁻⁴ S cm⁻¹ at 80 °C and the activation energy falling stepwise from 0.69 eV for the salt-only film to 0.67 eV with plasticizer and 0.59 eV with the nanofiller, confirming that the additives smooth the energetic landscape for lithium-ion hopping.

Direct-current polarization measurements using ion-blocking electrodes added a crucial safety metric. The ion transference number rose from 0.58 at 20 weight percent salt to 0.76 at 40 weight percent, then to 0.82 with Pluronic and finally to 0.90 in the fully optimized composite, indicating that ionic conduction overwhelmingly dominates over electronic leakage. Dielectric analysis reinforced the picture: both the dielectric constant and dielectric loss surged in the low-frequency regime as Pluronic and graphene oxide were added, a hallmark of increased free-ion density and enhanced electrode polarization. According to Bjerrum theory, the elevated dielectric constant also shortens the critical distance for ion-pair formation, further favoring salt dissociation, while the higher permittivity exponentially boosts charge carrier density. Electric modulus formalism, which suppresses electrode polarization, showed no relaxation peak within the measured frequency window, implying ion hopping times shorter than 1.6 × 10⁻⁷ seconds, fast dynamics for a biopolymer electrolyte.

Thermal data close the loop on practicality. Differential scanning calorimetry showed that the onset of chain fragmentation shifts downward as salt, plasticizer and filler are added, from 272 °C for the 20 weight percent salt film to about 253 °C for the optimized composite, but all samples remain comfortably above the operating temperatures of real batteries. The optimized conductivity is comparable to other reported systems such as starch/PEGMA (3.8 × 10⁻⁵ S cm⁻¹) and PEO/sepiolite nanoribbon composites (9.22 × 10⁻⁵ S cm⁻¹), though it trails ionic-liquid and chemically modified electrolytes in the 10⁻⁴ to 10⁻³ S cm⁻¹ range. The authors caution that their study was limited to structural characterization, impedance and dielectric analysis; validating the electrolyte in actual cells will require linear sweep and cyclic voltammetry to establish the electrochemical stability window, along with full-cell testing. If those trials succeed, tomorrow’s batteries could draw part of their backbone not from petrochemicals but from a crop grown on farms worldwide, a small but meaningful step toward truly sustainable energy storage.

Subject of Research: Biodegradable corn starch-based solid polymer electrolytes enhanced with lithium perchlorate, Pluronic plasticizer, and graphene oxide nanofiller for sustainable lithium-ion battery applications.

Article Title: Pluronic and graphene oxide influence the structural properties as well as the ionic conductivity and dielectric behavior of corn starch based solid electrolytes

Article References: Numan, M., Arwish, S., Khan, K. H., Shah, S. M., & Hussain, H. (2026). Pluronic and graphene oxide influence the structural properties as well as the ionic conductivity and dielectric behavior of corn starch based solid electrolytes. Discover Electrochemistry, 3(1), Article 69. https://doi.org/10.1007/s44373-026-00157-8

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00157-8

Keywords: solid polymer electrolyte, corn starch, graphene oxide, Pluronic plasticizer, ionic conductivity, lithium perchlorate, dielectric behavior, biopolymer, lithium-ion batteries, FTIR spectroscopy, electrochemical impedance spectroscopy, sustainable energy storage