Enhancing room temperature performance of solid-state lithium cell via a facile solid electrolyte-cathode interface design

Herein, we report the enhanced electrochemical performance of a solid-state cell realized through an engineered solid electrolyte-cathode interface via a simple casting technique. The ceramic-in-polymer solid electrolyte sample with 15 wt% NASICON-type Li1 & sdot;2Sn0 & sdot;9Zr0 & sdot;9Al0 & sdot;2(PO4)3 ceramic filler in a P(VDF-HFP) matrix (CPSE15) showed the highest room temperature conductivity of -1.1 x 10-4 S cm-1 and lithium-ion transference number of -0.60. The symmetric Li|CPSE15|Li cell showed a consistent voltage profile with an over-potential of -45 mV for 750 h at a current density of 0.1 mA cm-2. CPSE15 slurry was directly cast onto the LiFePO4 (LFP) cathode layer using a doctor-blade coating method to obtain a cathode-electrolyte assembly. Subsequently, a full cell fabricated using this assembly and lithium metal delivered an initial discharge capacity of -157 mAh g-1 at 0.2C. Further, the cell exhibited -90 mAh g-1 discharge capacity at 1C and sustained 500 charge-discharge cycles at room temperature. The engineered interface in cathode-electrolyte assembly enabled this cell to outperform its conventionally fabricated counterpart with a stacked LFP cathode sheet and freestanding CPSE15 electrolyte membrane, which was attributed to a lower interfacial resistance (-51%) of the former.