A cellulose reinforced polymer composite electrolyte for the wide-temperature-range solid lithium batteries

The lightweight solid electrolyte design in replacement of the flammable liquid electrolyte and polyolefin separator is the key of the energy-dense all-solid-state batteries (ASSBs) construction. However, the technological barriers of scalable manufacturing, retarded ionic conductivity at room temperature as well as the mechanical fragility upon the high-temperature operation restrict the ASSB deployment of practical relevance. In this study, an ultra-lightweight (1.67 mg cm⁻²), thin (25 μm), high strength and thermally robust (stability up to 180 °C) composite solid electrolyte (CSE) has been designed to address the dilemma by the rational integration of polyethylene glycol monomethyl ethers coated Li_6.4La₃Zr_1.4Ta_0.6O₁₂ nanofillers (MPEG@LLZTO) with lightweight nanocellulose scaffold. The MPEG coating layer enhances the interfacial compatibility and homogeneous dispersibility of LLZTO nanofiller within the poly (ethylene oxide) (PEO) matrix, while the mechanically flexible and thermally stable nanocellulose scaffold guarantees the formation of the high-temperature endurance and structural robustness for the as-formed CSE layer. Upon the solvent-free, layer stacked-up assembly of the PEO/MPEG@LLZTO-Nanocellulose (PLCN) CSE film with the high-mass-loading LiFePO₄ cathode and thin-layer lithium anode, the ASSB prototype could simultaneously realize the high gravimetric energy density (323 Wh kg⁻¹), cycling stability as well as operation reliability within a wider temperature range (25 °C ∼ 130 °C).