Preparation And Properties Of Ionic Gel Quasi-solid Electrolytes Based On Different Lithium Salts

At present,lithium ion batteries have a broad development prospect in the fields of new energy electric vehicles,electronic products or clean energy storage equipment,but the performance and safety of electrolytes are gradually becoming a shackle affecting the development of lithium ion batteries.Therefore,it is urgent to develop new electrolytes to solve the above problems.Ionogel electrolytes,as a new kind of quasi-solid electrolyte,combine the properties of ionic liquids and solid matrix,which not only overcomes the fluidity of liquid electrolytes,but also shows the high mechanical strength of solid matrix.More importantly,ionogel electrolytes can improve the electrochemical properties of the electrolyte to some extent,such as the electrochemical window and so on.Hence,ionogel electrolytes have attracted more and more attention in the scientific community.In this article,the preparation methods of iongel quasi-solid electrolytes containing different lithium salts were explored.In addition,the structure characterization and performance testing were analyzed by using scanning electron microscope(SEM),thermogravimetric analyzer(TG),electrochemical workstation and other instruments,aims to explore the optimum comprehensive properties of ionogel quasi-solid electrolyte.The main research contents and results are as follows:(1)At first,lithium salts such as lithium bis(trifluoromethanesulfonyl)imide(LiTFSI),lithium bis(fluorosulfonyl)imide(LiFSI),lithium oxalyldifluoroborate(LiDFOB),lithium tetrafluoroborate(LiBF₄),lithium hexafluorophosphate(LiPF₆)and ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([Emim][TFSI])were prepared as electrolyte.Then,electrolyte and MCM-41 molecular sieve used as solid matrix were prepared by impregnation method as the inorganic nano ionogel electrolytes,which were referred to as IGE quasi-solid electrolytes.The experimental results show that the inorganic nano ionogel electrolyte containing LiDFOB(IGE-LiDFOB)has the best comprehensive performance.Firstly,the thermal stability of the electrolyte is good,and the thermal decomposition temperature can reach 340?.Secondly,the electrochemical properties of the electrolyte are good,the ionic conductivity can reach 1.558×10^-3 S·cm^-1,the electrochemical stability window can reach 5.492 V(vs.Li/Li⁺),the cycle reversible,lithium dendrite resistance and aluminum corrosion resistance are good.Thirdly,the prepared half cell can cycle 1200 times stably,the specific capacity is close to 137 m Ah·g^-1,and the coulombie efficiency is close to 100%.Besides,the prepared half cell also have good cycling rate capability.(2)Using polyvinylidene fluoride(PVDF-HFP)as polymer matrix,ionic liquid[Emim][TFSI]as plasticizer,MCM-41 molecular sieve as filler,and adding lithium salts such as lithium bis(trifluoromethanesulfonyl)imide(LiTFSI),lithium bis(fluorosulfonyl)imide(LiFSI),lithium oxalyldifluoroborate(LiDFOB),lithium tetrafluoroborate(LiBF₄),lithium hexafluorophosphate(LiPF₆),the inorganic-organic composite ionogel electrolytes were prepared by solution casting,which is referred to as IGPE quasi-solid electrolytes.The experimental results show that the inorganic-organic composite ionogel electrolyte containing LiDFOB(IGPE-LiDFOB)has the best comprehensive performance.Firstly,the thermal stability of the electrolyte is good,and the thermal decomposition temperature can reach 200?.Secondly,the electrochemical properties of the electrolyte are good,the ionic conductivity can reach 6.652×10^-3 S·cm^-1,the electrochemical stability window can reach 4.585 V(vs.Li/Li⁺),the cycle reversible,lithium dendrite resistance and aluminum corrosion resistance are good.Thirdly,the specific capacity of the prepared half cell is 123 m Ah·g^-1 after 2262 cycles,which maintains 81%of the initial specific capacity and coulombie efficiency is close to 100%.Besides,the prepared half cell also have good cycling rate capability.