Lithium-Salt-Rich PEO/Li_0.3La_0.557TiO₃ Interpenetrating Composite Electrolyte with Three-Dimensional Ceramic Nano-Backbone for All-Solid-State Lithium-Ion Batteries

Solid electrolytes with high ionic conductivity and good mechanical properties are required for solid-state lithium-ion batteries. In this work, we synthesized composite polymer electrolytes (CPEs) with a three-dimensional (3D) Li_0.33La_0.557TiO₃ (LLTO) network as a nano-backbone in poly(ethylene oxide) matrix by hot-pressing and quenching. Self-standing 3D-CPE membranes were obtained with the support of the LLTO nano-backbone. These membranes had much better thermal stability and enhanced mechanical strength in comparison with solid polymer electrolytes. The influence of lithium (Li) salt concentration on the conductivity of 3D-CPEs was systematically studied, and an ionic conductivity as high as 1.8 × 10^-4 S·cm^-1 was achieved at room temperature. The electrochemical window of the 3D-CPEs was 4.5 V vs Li/Li⁺. More importantly, the 3D-CPE membranes could suppress the growth of Li dendrite and reduce polarization; therefore, a symmetric Li|3D-CPE|Li cell with these membranes was cycled at a current density of 0.1 mA·cm^-2 for over 800 h. All of the superior properties above made the 3D-CPEs with the LLTO nano-backbone a promising electrolyte candidate for flexible solid-state lithium-ion batteries.