LiNO 3 regulated rigid-flexible-synergistic polymer electrolyte boosting high-performance Li metal batteries

Conventional polymer electrolytes suffer from low ionic conductivity, poor interface compatibility, low mechanical strength and certain flammability. Herein, a rigid-flexible synergistic ultrastrong nonflammable polymer electrolyte (LiNO 3 -PPT@PI) regulated by LiNO 3 is developed, which consists of rigid polyimide (PI) fiber skeleton and flexible poly pentaerythritol tetraacrylate (PPT) plasticized with LiNO 3 /triethyl phosphate (TEP)/fluoroethylene carbonate (FEC). PI fiber skeleton enhances tensile strength of LiNO 3 -PPT@PI to 21.8 MPa. TEP effectively enhances ionic conductivity to 7.57 × 10 −4 S cm −1 at 30 °C and improves flame retardancy. LiNO 3 is creatively utilized as the only lithium salt for LiNO 3 -PPT@PI to construct Li 3 N-rich solid electrolyte interphases (SEIs) and promote FEC to form LiF-rich SEIs/cathode-electrolyte interphases (CEIs) to improve interface stability, thereby enabling high-efficiency, long-term and dendrite-free cycling of LiFePO 4 (LFP)||Li cells and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NCM811)||Li cells, which is superior to the LiPF 6 -based polymer electrolytes. LFP||Li cells with LiNO 3 -PPT@PI exhibit excellent cycle performance over 650 cycles with 81.8 % capacity retention. This work presents a promising design strategy of safe and efficient polymer electrolytes for Li metal batteries.