Li⁺ -Containing, Continuous Silica Nanofibers for High Li⁺ Conductivity in Composite Polymer Electrolyte

Solid-state electrolytes have recently attracted significant attention toward safe and high-energy lithium chemistries. In particular, polyethylene oxide (PEO)-based composite polymer electrolytes (CPEs) have shown outstanding mechanical flexibility and manufacturing feasibility. However, their limited ionic conductivity, poor electrochemical stability, and insufficient mechanical strength are yet to be addressed. In this work, a novel CPE supported by Li⁺ -containing SiO₂ nanofibers is developed. The nanofibers are obtained via sol-gel electrospinning, during which lithium sulfate is in situ introduced into the nanofibers. The uniform doping of Li₂ SO₄ in SiO₂ nanofibers increases the Li⁺ conductivity of SiO₂ , generates mesopores on the surface of SiO₂ nanofibers, and improves the wettability between SiO₂ and PEO. As a result, the obtained SiO₂ /Li₂ SO₄ /PEO CPE yields high Li⁺ conductivity (1.3 × 10^-4 S cm^-1 at 60 °C, ≈4.9 times the Li₂ SO₄ -free CPE) and electrochemical stability. Furthermore, the all-solid-state LiFePO₄ -Li full cell demonstrates stable cycling with high capacities (over 80 mAh g^-1 , 50 cycles at C/2 at 60 °C). The Li⁺ -containing mesoporous SiO₂ nanofibers show great potential as the filler for CPEs. Similar methods can be used to incorporate Li salts into other filler materials for CPEs.