Preparation and Electrochemical Performance of Polyzwitterion Containing Intramolecular Salt as Solid Electrolytes for Lithium-ion Batteries

Polymer electrolytes are known to be more effective in enhancing the safety and energy density of lithium-ion batteries as compared to organic electrolytes. However, the practical application of polymer electrolytes is hindered due to their low ionic conductivity, narrow electrochemical window, and incompatibility with lithium metal anode. In this work, a polyzwitterion (P(AMPSLi-IL)) containing intramolecular lithium salt of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) was designed and synthesized through a radical copolymerization of acryloyloxyethyltrimethyl ammonium bis(trifluoromethanesulphonyl)imide (AETATFSI) and lithium 2-acrylamido-2-methylpropanesulfonic acid (AMPSLi). A series of nanofiber membranes composed of poly(vinyl alcohol) (PVA) and P(AMPSLi-IL) were prepared by electrospinning technology. The nanofiber membrane with optimized ratio of PVA to P(AMPSLi-IL) shows a high tensile strength of 13.8 MPa and thermal decomposition temperature of 280 degrees C. The nanofiber membranes were in situ gelated in a based electrolyte (1 mol/ L LiFSI in EC) with tri(propylene glycol) diacrylate (TPGDA) as a crosslinking agent, which was used as a polymeric solid electrolyte. The optimized electrolyte of PVA9-P(AMPSLi-IL)(1) exhibited a high ionic conductivity of 2.87x10(-3) S center dot cm(-1) at room-temperature, high lithium transference number of 0.85 and oxidation potential of 4.34 V (versus Li/Li+). The symmetric Li|Li cell with the PVA9-P(AMPSLi-IL)(1) electrolyte shows an excellent cycle stability for over 1800 h, demonstrating a great compatibility between Li anode and the PVA9-P(AMPSLi-IL)(1) electrolyte. The LFP|Li half cell with the PVA9-P(AMPSLi-IL)(1) electrolyte delivers an initial discharge capacity of 145.7 mAh center dot g(-1) at 0.5 C with a capacity retention of 79.0% after 200 cycles.