Highly conductive composite cathode prepared by dry process using Nafion-Li ionomer for sulfide-based all-solid-state lithium batteries

Abstract

All-solid-state lithium batteries (ASSLBs) offer safe operation and high energy density, making them potential alternatives to liquid-electrolyte-based lithium-ion batteries. Sheet-type composite cathodes for sulfide-based ASSLBs are typically fabricated using a nonconducting polytetrafluoroethylene (PTFE) binder by a solvent-free dry process, resulting in poor cycling stability and low rate capability. We demonstrate a strategy for using a Li+-incorporated Nafion (Nafion-Li) binder to fabricate a composite cathode via a dry process for improving cycling performance of ASSLBs. The solid-state cell assembled with Li6PS5Cl and LiNi0.7Co0.15Mn0.15O2 cathode using an optimal amount of Nafion-Li delivers a discharge capacity of 177.8 mAh g−1 (4.1 mAh cm−2) at 25 °C and exhibits a high capacity retention of 97% after 200 cycles at 0.5C. The improved cycling performance results from enhanced electrical conductivity (ionic and electron conductivity) and better interfacial contacts between cathode active material, solid electrolyte, and conducting carbon in the composite cathode, provided by Nafion-Li binder.