Tailoring Intermolecular Chemistry and Interphases via F, N-Functionalized Polymer Matrix in High-Flash-Point...

In situ polymerized quasi-solid-state electrolytes (QSEs) are promising for lithium metal batteries (LMBs) yet face challenges regarding high-voltage stability and kinetics. Herein, a novel ether-ester hybrid QSE is achieved through the in situ copolymerization of 2,2,2-trifluoroethyl acrylate (TFEA) and 2-isocyanatoethyl methacrylate (IEM) within a tetraethylene glycol dimethyl ether (G4)/fluoroethylene carbonate (FEC) solvent system. This design leverages synergistic interactions between the functionalized polymer matrix (─CF₃ and ─N═C═O) and liquid components. The incorporation of FEC and the regulatory effect of the polymer backbone tailor the Li⁺ solvation structure toward an anion-rich configuration, which gives rise to a robust, antioxidative, and inorganic-rich interphase. Furthermore, hydrogen bonding interactions effectively immobilize PF₆ ^- anions and free G4 molecules, thereby elevating the Li⁺ transference number and enabling the electrochemical stability window over 4.8 V (vs. Li⁺/Li). The QSE exhibited a high room-temperature ionic conductivity of 2.2 × 10^-3 S cm^-1. Consequently, 4.2 V Li|| LiFePO₄ (LFP) cells demonstrate 93% capacity retention over 1,000 cycles, while 4.5 V Li||NCM811 (NCM811) cells retain 80% over 300 cycles. A specific energy of 302.64 Wh kg^-1 is attained in a 2 Ah Li||NCM811 pouch-type cell. These findings highlight tailored molecular design and controlled interactions as a viable route for advancing high-energy-density quasi-solid-state batteries.