Perfluoropolyether-based block copolymer electrolytes enabling high-temperature-resistant solid-state lithium metal batteries

In recent years, the safety problems caused by thermal runaway during the operation of lithium-ion batteries (LIBs) are common. Therefore, fabrication of LIBs that can be used under high temperature is the current research focus. In this work, we designed a perfluoropolyether (PFPE)-based block copolymer electrolyte (PFPEBCPE). The PFPE blocks can improve the thermal stability of PFPEBCPE. The LiFePO4//Li cell assembled with PFPEBCPE exhibits excellent capacity retention (100 cycles, 90%), long-term charge-discharge stability (Coulomb efficiency, 99%) and rate performance (1 C, 137.7 mA h g−1) at 120 °C. The PFPE blocks can also improve the electrochemical stability window (5.0 V) and the lithium-ion transference number (0.56) of PFPEBCPE. In addition, PFPEBCPE can participate in the creation of stable fluorinated solid electrolyte interphase (SEI), enabling the Li//Li symmetric cell to cycle stably for up to 1500 h at a current density of 0.1 mA cm−2.