Polymeric ionic liquid enhanced all-solid-state electrolyte membrane for high-performance lithium-ion batteries

Polymeric ionic liquid electrolytes have received great attention for use in next-generation solid lithium-ion batteries. However, most polymeric ionic liquid electrolytes require a high proportion of organic liquid plasticizer to improve the room temperature ionic conductivity . This comes at the expense of sacrificing the mechanical strength of the electrolytes. In addition, it is also difficult to establish a clear relationship between polymeric ionic liquid segments and properties of the electrolyte. Here, a copolymeric ionic liquid poly(N-(1-vinylimidazolium-3-butyl)-ammonium bis(trifluoromethanesulfonyl)imide)- co -poly(poly(ethylene glycol) methyl ether methacrylate) is synthesized and the corresponding self-standing flexible all-solid electrolyte (PVIMTFSI- co -PPEGMA/LiTFSI) is prepared via a solution-casting method. The effect of the polymeric ionic liquid segments on comprehensive properties of the electrolyte is investigated in detail by comparing the performance of PVIMTFSI- co -PPEGMA/LiTFSI with PVIM- co -PPEGMA/LiTFSI (poly(N-vinlyimidazole)- co -poly(poly(ethylene glycol) methyl ether methacrylate) based electrolyte) which contains un-ionized imidazole groups. As a result, the electrochemical window slightly decreases from 5.5 V to 5.3 V, but the ionic conductivity and interfacial behavior are both greatly improved. In Particular, the polymeric ionic liquid segments can restrain the formation of lithium dendrites . Moreover, a discharge capacity of 136 mAh g −1 at 0.1 C can be realized for the PVIMTFSI- co -PPEGMA/LiTFSI-based LiFePO 4 /Li battery that is maintained at approximately 70 mAh g −1 at 1 C at 60 °C, which is superior to that obtained for the PVIM- co -PPEGMA/LiTFSI electrolyte.