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 Li1·2Sn0·9Zr0·9Al0·2(PO4)3 ceramic filler in a P(VDF-HFP) matrix (CPSE15) showed the highest room temperature conductivity of ∼1.1 × 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.