Solid-state polymer electrolytes with polypropylene separator-reinforced sandwich structure for room-temperature lithium ion batteries

Abstract Solid-state polymer electrolytes (SSPEs) for room-temperature lithium ion batteries (LIBs) usually suffer from the uncontrollable lithium dendrite propagation due to the mechanical weakness. Herein, through a facile double-side coating strategy, novel sandwich-like poly (vinylidene fluoride) (PVDF)-based electrolyte membranes that are mechanically reinforced by polypropylene (PP) separator are successfully developed for high-performance room-temperature solid-state LIBs. With a small amount of bound dimethylformamide (DMF) to serve as a plasticizer for the PVDF polymer host, the as-prepared PVDF/PP SSPEs achieve a high ionic conductivity of 1.53 × 10−4 S cm−1. The robust commercial PP separator can significantly improve the mechanical properties of the sandwich SSPEs, and more importantly it functions as physical obstacle here to restrain lithium dendrite growth during the repeated charge-discharge cycling. The solid-state batteries assembled with the PVDF/PP SSPEs, LiFePO4 (LFP) cathode and lithium anode thus exhibit dramatically enhanced cycling performance compared with the batteries based on blank PVDF SSPEs, delivering a high specific capacitance of 134 mAh g−1 and 97% capacity retention over 180 cycles under 0.3C at room temperature. Such high-performance PVDF/PP SSPEs with the facile and scalable fabrication, together with the low-cost and widely available raw materials, are highly promising electrolytes for room-temperature solid-state LIBs.