The Research Of The Ionic Liquid.based Mixed Lithium-ion Battery Electrolytes

Lithium ion battery(LIB)is thought as a promising power source for its light weight,high voltage,high energy densities and high cycle performance.Current LIB is implemented in the large.scale high.power system such as the plug.in hybrid electric vehicle or plug.in electric vehicle.However,the vast majority of commercial LIB use an organic carbonates(e.g.Diethyl carbonate,dimethyl carbonate,ethylene carbonate)as electrolyte.The use of these organic solvent electrolyte allows the realization of high performance LIB,but since they are flammable,their use also poses serious safety risks and strongly reduces the battery operative temperature range.So a safety electrolyte needs to be designed in LIB.The electrolyte optimum composition consists of 0.75 mol/L LiTFSI in the[EMIM]TFSI mixed with EC and DMC in weight ratio of 60:20:20.The LiFePO4/Li cell using 0.75 mol/L LiTFSI/([EMIM]TFSI/EC/DMC)as electrolyte show that the first coulomb efficiency was 90%and the first discharge capacity was 168 mAh/g.The 30 th reversible capacities were maintain 155 mAh/g at 0.2 C.And finding the optimum balance between ionic liquid and organic solvents is crucial.Physical properties including conductivity,thermal stability and flammability along with electrochemical performances like cyclic voltammetry and cyclic performance of the mixed electrolyte were discussed.Besides,in order to break restriction on the application of lithium ion battery technology,high temperature performance was tested to detect the high temperature extremes.In mixed electrolyte,safety and stability of the electrolyte were greatly improved by the adding of IL,no flame was observed at the concentration of 60%IL.Meanwhile higher conductivity(14.78 mS/cm)was obtained at the concentration of 60%IL.The electrolyte possess exellent compatibility with cathode.Compared with traditional electrolyte and pure IL electrolyte,IL.based mixed electrolyte have good efficiencies and higher charge and discharge performances.The tLi+ of IL.based mixed electrolyte at room temperature are 0.72.Thermal stability of IL.based mixed electrolyte higher than traditional electrolyte,and show almost non.flammability by the burning tests...