Densely Imidazolium Functionalized Water Soluble Poly(Ionic Liquid) Binder for Enhanced Performance of Carbon Anode in Lithium/Sodium‐Ion Batteries

Abstract The binder's choice holds immense significance in the quest for robust electrochemical performances of lithium/sodium‐ion battery's (LIB/SIB) electrodes. Conventional PVDF binder is a passive polymer lacking the ability to transport Li + /Na + and facilitate ion kinetics. This limitation poses constraints in achieving high specific capacity, fast charging, and long cycle life. Herein, a novel water‐soluble concentrated imidazolium functionalized poly(ionic liquid), poly(oxycarbonylmethylene 1‐allyl‐3‐methyimidazolium) (PMAI) is synthesized, and evaluated it as binder in LIB/SIB. PMAI‐based anodic‐half cell exhibits excellent electrochemical performance, achieving higher capacities (297 mAhg −1 at 1C for LIBs and 250 mAhg −1 at 60 mAg −1 for SIBs) and good cycle stability (80 % capacity retention after 750 cycles for LIBs; 96% capacity retention after 200 cycles for SIBs), compared to PVDF binder. In addition, PMAI/Gr delivers a higher discharge capacity of 85 mAhg −1 than PVDF/Gr with 47 mAhg −1 at 5C. PMAI‐containing electrodes show better rate capability at different current densities than PVDF binder in LIB/SIB. The enhanced ion diffusion coefficient, lower resistance and decreased activation energy of desolvation, are ascribed to densely polar ionic liquid groups along the polymer and formation of a functionalized SEI via binder reduction. The novel PMAI binder's design and full‐cell examination confirm its potential in secondary‐ion battery applications.