Boosting safety and performance of lithium-ion battery enabled by cooperation of thermotolerant fire-retardant composite membrane and nonflammable electrolyte

Abstract

• Thermotolerant and fire-retardant nano-CaCO 3 -based membrane was designed. • LIBs with nonflammable electrolyte-immersed membrane possess superior cyclability. • LIBs exhibit better safety by preventing short circuit and reducing heat release. • Lithium ion full battery shows good long cycling stability at 120 °C under 2C. Developing nonflammable electrolytes is regarded as a convenient strategy to solve the combustion problem of lithium-ion batteries (LIBs), but its influences are limited by the severe shrinkage and high combustibility of polyolefin separators at elevated temperatures. Herein, an intrinsically thermotolerant and fire-resistant nano-CaCO 3 -based composite membrane (CPVH) is designed rationally. The CPVH membrane presents superior thermal stability (barely visible shrinkage at 300 °C), excellent nonflammability and extremely low heat release (∼11% as much as PP). Moreover, the alkaline nano-CaCO 3 can neutralize hydrofluoric acid that inevitably exists in LiPF 6 -based electrolytes, guaranteeing the long-term stability of interfacial layers. Noticeably, LiFePO 4 /Li battery with CPVH membrane delivered a discharge capacity of 133.6 mAh g −1 at 0.5C, along with a capacity retention of 93.0% and a coulombic efficiency of 99.9% after 650 cycles. Additionally, harsh safety tests of the battery demonstrate stable circuit safety at a high temperature of 150 °C and a significantly low heat release during thermal runaway. Significantly, the LiFePO 4 /CPVH/graphite full battery showed good cycling stability with a capacity retention of 78.4% and an average coulombic efficiency of 98.0% at 120 °C and 2C after 100 cycles. By combining CPVH composite membrane and nonflammable electrolyte, both safety and cycling performance of LIBs were improved completely.