LiNO3 regulated rigid-flexible-synergistic polymer electrolyte boosting high-performance Li metal batteries

Abstract

Conventional polymer electrolytes suffer from low ionic conductivity, poor interface compatibility, low mechanical strength and flammability. Herein, a rigid-flexible synergistic ultrastrong nonflammable polymer electrolytes (LiNO₃-PPT@PI) regulated by LiNO₃ is developed, which consists of rigid polyimide (PI) fiber skeleton and flexible poly pentaerythritol tetraacrylate (PPT) plasticized with LiNO₃/triethyl phosphate (TEP)/fluoroethylene carbonate (FEC). PI fiber skeleton enhances tensile strength of LiNO₃-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. LiNO₃ is creatively utilized as the only lithium salt for LiNO₃-PPT@PI to construct Li₃N-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 LiFePO₄ (LFP)||Li cells and LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811)||Li cells, which is superior to the LiPF₆-based polymer electrolytes. LFP||Li cells with LiNO₃-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.