Composite Polymer Electrolytes Based on PVA/PAN for All-Solid-State Lithium Metal Batteries Operated at Room Temperature

In this study, we used a solution-casting technique to prepare all-solid-state composite polymer electrolytes (CPEs) based on poly(vinyl alcohol)/polyacrylonitrile blends, the ceramic filler Li1.4Al0.4Ti1.6(PO4)3 (LATP, NASICON-type structure), lithium bis(trifluoromethanesulfonyl)imide, and the solid plasticizer succinonitrile (SN) and then investigated their electrochemical stability, ionic transport properties, and interfacial behavior against lithium electrodes. The CPEs prepared with optimal concentrations of LATP (20 wt %) and SN (10 wt %) exhibited a maximum ionic conductivity of 1.13 × 10–4 S cm–1 at 25 °C, a Li+-ion transference number of 0.507, and an electrochemical stability window of 5.1 V (vs Li/Li+). This CPE was a free-standing membrane and highly flexible. An all-solid-state Li//LiFePO4 battery assembled with this CPE displayed excellent cycling stability and rate performance at room temperature. A maximum discharge capacity of 159.6 mA h g–1 was achieved at 0.1C. The full cell achieved a discharge capacity of 119.4 mA h g–1 at 0.5C and a capacity retention of 90.5% after 100 cycles at ambient temperature. Therefore, this as-prepared CPE shows great promise for use in all-solid-state lithium-metal batteries.