Self-adaptable gel polymer electrolytes enable high-performance and all-round safety lithium ion batteries

High safety and electrochemical performance of lithium batteries are a pair of irreconcilable contradictions. Adding flame retardants to electrolytes or introducing the flame retarded structures to various polymeric matrices can attain the purpose of an improved fire-safety, but there is almost no positive contribution and even are many negative effects on the electrochemical performance of batteries due to chemical or/and physical incompatibility with electrolyte, electrode, etc.. Inspired by nature, we delicately design an intelligent self-adaptable gel polymer electrolyte (GPE) based on a novel copolymer with functional pendent groups, which can assist lithium ion migration, afford redox stability, promote cyclization reaction and suppress combustion by a synergy of the pendent groups. Using this copolymer-based GPE, not only deliver the various batteries superior long-term cycling performance at room temperature, but also a thermal shutdown function at high temperature and a flame retardancy exposed to fire can be achieved. Significantly, LiFePO4/GPE/graphite pouch battery with an initial capacity of 24.06 mAh possesses a capacity retention of 75.9% and a coulombic efficiency of 99.6% after 200 cycles at 0.5 C, and meanwhile presents excellent resistance to mechanical damage, high temperature and flame, demonstrating a proof of concept for extensively high safety of the practical LIBs.