Reinforced Anti-Oxidative Degradation and Interface Stabilization in Bimetal Oxide Filler-Based PEO Electrolytes for Lithium Metal Batteries

Abstract

Polyethylene oxide (PEO) electrolytes hold significant potential for the next-generation all-solid-state lithium metal batteries. However, their practical application is limited by low ionic conductivity, unstable solid electrolyte interphase (SEI) and, especially, poor oxidative stability under high voltages. Herein, a filler-modified PEO is proposed to address these challenges. The filler, TIO (SnO₂ doped with In₂O₃), is rich in oxygen vacancies, acting as Lewis acids to interact with TFSI⁻, which releases more Li⁺ and achieves a higher ionic conductivity and Li⁺ transference number. Moreover, Sn⁴⁺/In³⁺ in the TIO can form alloy phases with lithium metal to facilitate Li⁺ deposition and transport across the SEI. Consequently, Li//LiFePO₄ cells using the filler-modified PEO exhibit a reversible capacity of ∼140 mAh g⁻¹ and excellent capacity retention of 92% over 800 cycles at 0.2 C. Importantly, the TIO interacts with hydroxy groups and H atom on α-C in PEO, reducing PEO's reactivity and extending its decomposition potential to 4.75 V. Owing to the inhibited oxidative decomposition upon high-voltage cycling, the filler-modified PEO enables Li//LiNi_0.8Co_0.1Mn_0.1O₂ cells to achieve an outstanding initial capacity of 170 mAh g⁻¹ and maintain 70% capacity retention over 200 cycles at 0.5 C at a high cut-off voltage of 4.3 V.