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-lL))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 ℃.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 2.87× 10-3 S·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·g-1 at 0.5 C with a capacity retention of 79.0％after 200 cycles.
Lithium metal batteryPolymer electrolytePolyzwitterionPoly(vinyl alcohol)
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