Interface Strategies for Enhancing the Lithium-Ion Transport of Composite Polymer Electrolytes toward High-Performance Solid-State Batteries

Composite polymer electrolytes (CPEs) have received much attention for improving the safety performance of lithium-ion batteries significantly, among which introducing a polymer matrix with Li7La3Zr2O12 (LLZO) ceramics has become a research focus. However, poor interface contact, a big obstacle for the application of solid-state batteries, exists not only between electrodes and CPEs but also between the polymer and ceramic. Herein, two strategies are taken to address the interface issues. In the first, an ionic liquid (IL) is introduced to the CPE to modify the interfacial contact between electrodes and electrolytes. The prepared electrolyte delivers an excellent ionic conductivity (2.43 × 10–4 S cm–1 at room temperature), arising from the reduced energy barrier of Li+ diffusion, and a high Li+ migration number (0.687). In the second, the interface region between polymer chains and ceramic fillers is improved by eliminating the resistive surface layers of LLZO nanoparticles with crotonic acid. After modification, the ionic conductivity of the composite electrolytes was enhanced, and the rate performance of the LFP/Li cell with the modified CPE was improved notably. The results indicate that interface improvement, between electrodes and electrolytes as well as between the polymer and ceramic, was conducive to the Li+ migration in composite polymer electrolytes.