Enhanced electrochemical performance of PEO/Li_6.4Ga_0.2La₃Zr₂O₁₂ composite polymer electrolytes

All-solid-state lithium batteries (ASSLBs) are regarded as the most promising alternative to traditional liquid lithium-ion batteries due to their high-energy density and excellent safety. As an important part of ASSLBs, composite polymer electrolytes (CPEs) with excellent comprehensive performance have attracted wide attention from researchers. Herein, a series of CPEs were prepared by employing Li_6.4Ga_0.2La₃Zr₂O₁₂ (LGLZO) submicron particles with cubic phase as fillers in polyethylene oxide (PEO) matrix. The tape-casting method was employed to prepare PEO-LiTFSI-x% LGLZO (CPE-x, where x = 0–80). In these CPE-x, the CPE-40 exhibits elevated ionic conductivity (6.20 × 10⁻⁵ S cm⁻¹ at 20 °C and 1.88 × 10⁻⁴ S cm⁻¹ at 60 °C), attractive Li⁺ transference number (0.31 at 60 °C), low activation energy barrier of lithium-ion migration, wide electrochemical window, and high critical current density of 1.3 mA cm⁻². Furthermore, the LiFePO₄ | CPE-40 | Li batteries deliver outstanding cycle performance (capacity retention of 85.43% after 225 cycles at 0.2C and 60 °C) and rate performance. These results show that the PEO-base solid-state electrolytes filled with submicron LGLZO particles possess a broad application prospect.