Gradient trilayer solid-state electrolyte with excellent interface compatibility for high-voltage lithium batteries

Solid-state electrolytes (SSEs) are considered as promising alternatives for liquid electrolytes to achieve high energy density and safe lithium metal batteries. However, their practical utilization is limited owing to low ionic conductivity and insufficient interface stability. Here, a unique gradient trilayer SSE (20 µm) is designed to improve compatibility of anode/electrolyte/cathode interfaces and enhance structural integration to provide continuous Li+ transport channels. One side anti-oxidation polymer layer improves the high-voltage tolerance for electrolyte/cathode interface, and the other side anti-reduction polymer layer provides soft interfacial contact and compatibility with Li-metal anode. Remarkably, the ultrathin porous membrane as host allows the fully penetration of two different polymers to form a gradient middle layer, providing excellent structural integration and fast Li+ transport. Thus, the Li||Li symmetric cells with gradient trilayer electrolyte can stably operate over 2500 h under 0.1 mA cm−2. The LiNi0.8Co0.1Mn0.1O2||Li solid-state batteries with gradient trilayer electrolyte deliver over 107 mAh g−1 capacity after 1000 cycles at 0.5C. This work provides a novel strategy to significantly enhance multilayer SSE with gradient interface in solid-state lithium-metal batteries.