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

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. How-ever, 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 x 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.