Preparation And Electrochemical Preformance Of Imidazole-based Polyionic Liquid Electrolyte

Ionic liquids(ILS)is one of the most promising electrolyte materials for lithium-ion batteries due to their negligible vapor pressure reduction,excellent electrochemical performance and environmental protection.In this paper,imidazole based polyionic liquids were used as the research object.Functional groups were introduced through quaternary ammonium salt reaction,and double network polyionic liquids were prepared by cross-linking and polymerization.The electrochemical performance of the device was investigated and the main research is as follows.(1)The two-step method was used to synthesize 1-vinyl-3-epoxypropylimidazolium bis(trifluoromethylsulfonyl)imide(VEIM-TFSI)monomer,which was copolymerized with polyethyleneimine(PEI)and polyethylene glycol diacrylate(PEGDA)to synthesize double network polyionic liquid(PIL-PEI).At room temperature,the ionic conductivity of PIL-PEI can reach 1.03 m S cm^-1,and the lithium ion migration number is 0.47;the cycling performance discharge capacity is 160 mAh g^-1 after200 cycles at 0.1C;when the PIL-PEI is assembled into a soft pack cell,it can still supply power for the LED lamp under the damaged condition.(2)The VEIM-TFSI were partially cross-linked with PEI,and then added to PVDF-HFP for polymerization to form a poly(ionic liquid)with double network structure.Then a new flexible dual network ionic gel electrolyte(DN-Ionogel)was prepared by added the 1-ethyl-3-methyimidazolium bis(trifluoromethyl)imide(EMIm-TFSI)to the cross-linked network.The DN-Ionogel has high ionic conductivity(1.8m S cm^-1)and electrochemical window(above 5.0 V)at room temperature.The DN-Ionogel-cell also shows excellent rate performance(discharge capacity up to 115.6 mAh g^-1 at 4C current density)and stable cycle performance(capacity retention of 98%after 200 cycles).Assembling DN ionogel into a soft package cell,it can work continuously more than 7days and still power the LED under bending and cutting conditions.(3)The two-step method was used to synthesize 1-vinyl-3-aminoimidazole bis(trifluoromethylsulfonyl)imide salt(VAIM-TFSI)monomer.And then,a novel double crosslinked network polyionic liquid hydrolysate(CPIL)was prepared by VAIM-TFSI,EP-POSS,butyl acrylate(BA),PEGDA and EMIM TFSI.The thermal decomposition temperature of the CPIL is 260?,and the electrochemical window is higher than 5 V.At room temperature,CPIL has excellent ionic conductivity and lithium ion mobility,which are 2.5 m S cm^-1 and 0.52,respectively.When it was assembled into Li Fe PO₄/Li cell for charge discharge test,it shows excellent cycle performance(160 mAh g^-1 after200 cycles)and ratio performance(100 mAh g^-1 at 4.0C).