Reducing interfacial resistance of a Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte/electrode interface by polymer interlayer protection

Abstract

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_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) solid state electrolyte (SSE), which successfully decreased the interfacial resistance of the SSE/electrolyte interface by suppressing the reduction reaction of Ge⁴⁺ 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 × 10⁴ to 543 Ω cm². With a PPC–LAGP–PPC sandwich structure composite electrolyte (PLSSCE), the all-solid-state LiFePO₄/Li cell showed a high capacity of 148.1 mA h g⁻¹ at 0.1C and a great cycle performance over 90 cycles.