Enhancing the electrochemical properties of composite solid electrolytes with Ga–Rb-doped Li_6.5Ga_0.2La_2.95Rb_0.05Zr₂O₁₂ through composition control

Despite their potential as next-generation energy storage devices, all-solid-state batteries (ASSBs) have not been widely developed because of the low ionic conductivity of solid electrolytes and the high interfacial impedance with electrodes. This study addressed these issues by enhancing the electrochemical properties through composition control. A composite solid electrolyte (CSE) was fabricated using Li_6.5Ga_0.2La_2.95Rb_0.05Zr₂O₁₂ (Ga–Rb-doped LLZO) and poly(ethylene oxide) (PEO) with various compositions. The results demonstrated high ionic conductivity and electrochemical stability when the weight ratio of Ga–Rb-doped LLZO to PEO was 6:4. These characteristics effectively mitigated Li dendrite formation and ensured excellent interfacial stability. Notably, LiFePO₄/CSEs/Li full cells retained 92.3% of their initial capacity after 100 cycles at a 0.3 C rate. This study will promote the research and development of practical ASSBs incorporating LLZO solid electrolytes.