Fluorinated polyamide-based ion-solvating membranes for long-cycle quasi-solid-state lithium batteries

Membrane-based solid polymer electrolytes (SPEs) have emerged as promising candidates for enhancing the energy density and safety of lithium metal battery (LMBs), owing to their superior Li-salt dissociation capability, excellent lithium metal anode compatibility, and cost-effectiveness. However, conventional SPEs often suffer from limited thermal stability, low ionic conductivity, and inadequate mechanical strength. In this study, we developed a novel polymeric membrane incorporating CF 3 and amide functional groups, which was subsequently imbibed with lithium salt and solvents to form a homogeneous ternary electrolyte system of polymer/solvent/lithium-ion solvated membranes (ISMs). The resulting ion solvated membranes exhibit remarkable mechanical properties, high ionic conductivity and high security. The amide groups effectively anchor anions and coordinate with Li + , while the strong electron-withdrawing effect of -CF 3 groups facilitates the formation of efficient Li + transport channels. Density functional theory (DFT) calculations confirmed that lithium ions preferentially bind to the amide and -CF 3 groups rather than solvent molecules, The binding energy between co-FPA and Li + was calculated to be -3.40 eV, indicating a strong interaction. ISMs demonstrate outstanding electrochemical performance, achieving an ionic conductivity of 1.845 × 10 -4 S cm -1 and a high Li + transference number of 0.66. When assembled into Li/co-FPA-50/LFP cells, the system maintains 93% capacity retention after 200 cycles at 0.5 C (initial capacity: 158.6 mAh g -1 ). The ISM-based quasi-solid-state lithium batteries exhibit exceptional long-term cycling stability over 1000 cycles. This work presents an innovative approach for designing high-performance ion solvated membranes, addressing critical challenges in the development of safe and stable lithium metal batteries.