Recent advances in PEO-based polymer all-solid-state batteries (ASSBs), including optimized composite cathode formulations, are bringing this technology closer to practical deployment. However, temperature remains a limiting factor, as PEO-based SPEs typically require around 70 °C to ensure adequate ionic transport, while operation at higher temperatures may introduce mechanical, interfacial and long-term stability limitations. Since real applications involve dynamic temperature profiles differing from nominal conditions, quantifying the cell response beyond thermal activation becomes essential for the design of any application from an engineering perspective. With this aim, three lab-scale monolayer pouch cells incorporating a previously optimized 700 kg mol−1 PEO-based LiFePO4 composite cathode are characterized through galvanostatic discharge experiments at different temperatures and currents. The analysis provides engineering-relevant parameters, including storage capacity, limiting discharge current, open-circuit voltage (OCV), and area-specific effective full-cell conductance (Y). The thermal dependence of equilibrium and charge-transport properties is interpreted through Seebeck-type and Vogel–Tammann–Fulcher (VTF) relationships, enabling an experimental estimation of the OCV temperature coefficient (dOCV/dT) and temperature-dependent charge transport response. In addition, the cathode electronic conductivity is also measured as a function of temperature. These results provide electro–physical parameters for electrochemical modelling, thermal management design, and operating strategy assessment of PEO-based ASSBs under non-isothermal operating conditions.
Polyethylene oxide (PEO)-based composite solid electrolytes containing electrospun lithium aluminum titanium phosphate (LATP) and poly(vinylidene fluoride) (PVDF) nanofibers were fabricated to investigate the influence of LATP filler morphology on ionic conduction. LATP precursor nanofibers with the nominal composition Li1.3Al0.3Ti1.7(PO4)3 were prepared by electrospinning followed by calcination, whereas PVDF nanofibers were incorporated as a fibrous structural component without heat treatment. TGA/DTG analysis showed multistep removal of residual solvents and precursor-derived organic species, and XRD confirmed crystallization of NASICON-type LATP. A weak AlPO4 secondary-phase peak was already detectable at 800 °C and became more evident at 900 and 1000 °C; therefore, 700 °C was selected as the calcination temperature. DSC analysis showed a composition-dependent effect of filler morphology on PEO crystallinity; notably, at 25 wt% LATP the nanofiber-containing membrane exhibited a lower PEO crystallinity (17.4%) than the corresponding particle-containing membrane (43.7%). Electrochemical impedance spectroscopy showed that the ionic conductivity varied strongly with LATP filler morphology and composition, reaching 1.19 × 10−4 S cm−1 at room temperature for the 25 wt% sample, whereas the corresponding particle-filled membrane exhibited 5.15 × 10−6 S cm−1. Because LATP and PVDF fractions were varied simultaneously, the conductivity trend is interpreted as a combined compositional, morphological, and interfacial effect rather than as an isolated LATP-content effect.
Layered perovskite Sr1.1La0.9AlO4-δ with the Ruddlesden-Popper structure was synthesized by the combustion method (glycine-nitrate soft-chemistry technique) and investigated as potential oxide-ion conductor for intermediate-temperature devices for electrochemical applications. X-ray diffraction analysis confirmed the formation of single-phase material with tetragonal symmetry (space group I4/mmm). The introduction of Sr2+ cation in the position of La3+ leads to the creation of oxygen vacancies and a significant increase in oxide-ion conductivity. At 600 °C, the conductivity increased by factors of 110 compared to the parent sample SrLaAlO4 and reaches 2.8 · 10−4 S cm−1; the activation energy decreased from 1.51 eV for SrLaAlO4 compound to 0.81 eV for the Sr2+-substituted phase, as a result of the best balance between structural parameters (unit cell volume and free cell volume). The studied phase was stable over a wide range of PO2(10−20 –0.68 atm) at 400–900 °C and in CO2-containing atmosphere (50% CO2:50% air). The present result endorses that the RP compounds based on aluminates are low-cost promising candidates for electrochemical devices.
A sustainable biopolymer-based polymer electrolyte (BBPE) was developed by incorporating sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) into a guar gum (GG) matrix using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as a functional ionic-liquid medium. FTIR and SEM results indicated changes in the local chemical environment and a relatively uniform surface morphology, although these techniques do not directly establish crystallinity, bulk salt homogeneity, or molecular-level ion distribution. The optimized S3 electrolyte exhibited an ionic conductivity of 2.84 × 10−3 S cm−1 at ambient temperature, an apparent Arrhenius activation energy of 0.2177 eV, and a reduced Tgof 83.2 °C. The apparent Na+ transference number was 0.55, indicating significant Na+related cationic transport in the multicomponent electrolyte. LSV identified an anodic oxidation onset at approximately 1.75 V under the specified conditions, rather than a complete electrochemical stability window. An EDLC fabricated with S3 showed stable cycling over 1000 cycles, although the specific capacitance was modest at approximately 2.03 mF g−1. These results demonstrate the potential of GG–NaTFSI–[Bmim]Cl as a sustainable gel polymer electrolyte for low-voltage EDLC applications.
Sulfide-based all-solid-state lithium batteries (ASSLBs) are promising candidates for high-energy-density energy-storage systems, but their practical implementation is strongly limited by interfacial instability between lithium metal and sulfide solid electrolytes. Here, we report a simple ex situ surface treatment of lithium metal using zinc nitrate to construct a biphasic protective interphase for sulfide-based ASSLBs. Multi-scale structural and chemical analyses using SEM-EDS, XRD, XPS, and ToF-SIMS show that the modified interphase is compositionally differentiated, consisting of an N-rich outer region containing reduced LiN species and a LiZn-rich inner region adjacent to the Li substrate. Symmetric-cell measurements reveal that the treated Li exhibits more stable plating/stripping behavior and lowers interfacial resistance growth compared with bare Li, indicating mitigation of continuous interfacial degradation. Post-cycling analysis on the electrolyte side further confirms that the treated Li markedly suppresses sulfide-electrolyte decomposition. When applied to Li6PS5Cl-based full cells with a high-loading Ni-rich layered oxide cathode (4 mAh cm−2), the treated Li anode delivers stable rate capability and markedly improved cycling durability under demanding conditions. In particular, the interface-treated full cell retains more than 98% of its capacity over 100 cycles at 1C, whereas the bare-Li counterpart shows abnormal charge-capacity inflation and early shorting. These results demonstrate that a chemically simple yet functionally differentiated biphasic interphase can effectively stabilize the Li/sulfide-electrolyte interface and provide a practical interfacial-engineering strategy for sulfide-based lithium-metal ASSLBs.
