Reducing interfacial resistance of a Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 solid electrolyte/electrode interface by polymer interlayer protection.

High interfacial resistance of an electrode/electrolyte interface is the most challenging barrier for the expanding application of all-solid-state lithium batteries (ASSLBs). To address this challenge, poly(propylene carbonate)-based solid polymer electrolytes (PPC-SPEs) were introduced as interlayers combined with a Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) solid state electrolyte (SSE), which successfully decreased the interfacial resistance of the SSE/electrolyte interface by suppressing the reduction reaction of Ge 4+ against the Li metal, as well as producing intimate contact between the cathode and electrolyte. This work provides a systematic analysis of the interfacial resistance of the cathode/SSE, Li/SSE and the polymer/LAGP interfaces. As a consequence, the interfacial resistance of the Li/SSE interface decreased about 35%, and the interfacial resistance of the cathode/SSE interface decreased from 3.2 × 10 4 to 543 Ω cm 2 . With a PPC-LAGP-PPC sandwich structure composite electrolyte (PLSSCE), the all-solid-state LiFePO 4 /Li cell showed a high capacity of 148.1 mA h g -1 at 0.1C and a great cycle performance over 90 cycles.