Promoted Li⁺ conduction in PEO-based all-solid-state electrolyte by hydroxyl-modified glass fiber fillers

In the polyoxyethylene (PEO)-based solid-state electrolytes, the low ionic conductivity of lithium ions limits its application in solid-state lithium batteries, so optimizing the conduction path of lithium ions is beneficial to improve the ionic conductivity. In this work, we report the use of hydrothermal carbon nano-sphere (HCS) modified glass fibers (GF) as a functional filler (GF@HCS) to improve the ionic conductivity of PEO composite solid-state electrolytes. The oxygen atoms in the hydroxyl groups on the surface of HCS can be complexed with Li ions as its transport sites, which means that it can promote the long-distance transport of Li ions along the glass fiber surface. With addition of 2 wt% GF@HCS fillers, the degree of crystallinity of PEO composite solid-state electrolyte is the smallest, and the ionic conductivity is significantly increased from 8.9 × 10^–5 to 4.4 × 10^–4  S·cm⁻¹ at 60 °C. Moreover, the PEO composite solid-state electrolyte exhibits better lithium–metal interface stability in symmetric lithium batteries and superior rate performance in LiFePO₄ solid-state batteries.