A 3D fiber skeleton reinforced PEO-based polymer electrolyte for high rate and ultra-long cycle all-solid-state batteries

Abstract

Polyethylene oxide (PEO) polymer electrolytes are potential replacements as safer solid electrolytes for next-generation lithium metal batteries. However, the lower room temperature ionic conductivity and poor mechanical properties greatly hinder the practical application of solid polymer electrolytes (SPEs). In recent years, biomass materials have been sought for polymer reinforcement, but their role in SPEs has not been extensively studied. In this work, we report the loofah sponge anion exchange fiber (LS-AEF) as a modifier for PEO-based SPEs. First, the interaction between the quaternary amine cations on the material surface and the TFSI⁻ anion boosts the dissociation of LiTFSI and enhances the ion migration number (t_Li⁺ = 0.71). Moreover, the LiFePO₄/SPEs/Li full-cells assembled using 5% LS-AEF in PEO (PEO@5%LS-AEF SPEs) electrolytes can provide a capacity of 112.4 mA h g⁻¹ at 2C (60 °C), and after 150 cycles, the capacity retention rate is as high as 96.7%. At 160 °C and a 10C ultra-high rate, the battery still exhibits excellent cycle performance. More importantly, the soft pack battery assembled with PEO@5%LS-AEF SPE has a capacity retention rate of 98.9% after 1000 cycles at a current density of 0.2 A g⁻¹, which demonstrates unprecedented cycle stability.