Poly(vinylidene fluoride)-based dual-salt composite polymer electrolytes for superior room-temperature solid-state lithium batteries

Abstract

Polymer electrolytes are one of the most promising candidates for advancing the development of solid-state lithium metal batteries (SLMBs) due to their easy preparation process, high flexibility, and lightweight. However, the low ionic conductivity at room temperature limits their practical applications. In this study, we propose a strategy of dual-salt modification of polyvinylidene fluoride (PVDF)-based polymer electrolytes to enhance lithium ion transport channels, specifically through the introduction of Lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), lithium bis(oxalate)borate (LiBOB), and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) into polyvinylidene fluoride-polyvinyl acetate (PVDF-PVAC) polymer chain to form a dual-salt composite polymer electrolyte (DS-CPE), which effectively control the dehydrofluorination of the PVDF skeleton and eliminate the PVDF gel discoloration phenomenon. The newly developed DS-CPE shows high ionic conductivity at room temperature (4.96 × 10−4 S cm−1), sufficient Li+ transference number (tLi+ = 0.57), excellent oxidation resistance (5.4 V vs. Li/Li+), and favorable interfacial compatibility. Moreover, Li|DS-CPE|Li symmetric cell stably cycles 1300 h at 0.1 mA cm−1, and the Li|DS-CPE|LFP cell delivers excellent rate performance, maintaining a capacity retention of 91.4 % over 450 cycles.