Research And Application Of Lithium Ion Battery Electrolyte System With High Security

Electrolyte plays an important role in lithium ion battery, determines the battery’s lifespan, operation temperature range&safety. It can improve the safety performance of lithiumion battery by reducing the vapor pressure and improving the flame retardant property ofelectrolyte. Compared with the linear carbonate, cyclic carbonate possesses high dielectricconstant and high flash point, so increasing the ratio of cyclic carbonate can improve theflammability of the electrolyte. Ionic liquid possesses the advantages of non-flammability,low vapor pressure, good electrochemical stability and its application in lithium ion batteryhas become the focus of research.This paper combined the advantage and disadvantage of PC and ionic liquid, contactedthe function of lithium salt in lithium ion battery and improved the security of the electrolyte.First of all, we discussed the problem when PC is used in electrolyte. Through analyzing themechanism of the problems, we proposed the solutions and studied the suppression effect tothe decomposition of the PC when lithium salt, ionic liquid and solvent is added. Thenstudied the influence by lithium salt to the electrolyte’s combustion properties, charging anddischarging of LiFePO4half-cell&graphite half-cell under normal temperature and hightemperature. On the basis of preliminary experiment, through optimizing the ratio of PCsolvent, ionic liquid and linear carbonate, we got the electrolyte which met the needs of fullbattery charge and discharge for a long time. In the end, we made contrast experiments thatthe corrosion situation of aluminum foil by ionic liquids and lithium salt which is made ofanion TFSI-&FSI-, analyzed aluminum foil’s corrosion state which caused by theconcentration of corrosion component in ionic liquids and organic solvents.The experiment revealed that it can reduce the flammability of electrolyte by using PCas the main solvent, mixing with ionic liquids and increasing the concentration of lithiumsalt, it was also benefit for inhibiting corrosion of aluminum foil by corrosion component inthe electrolyte, and improved the stability of aluminum foil under high temperature, combined with electrochemical properties test of lithium ion battery, we obtained the bestlithium salt concentration of high flashing point solvent. Through research and comparison,we discovered that the high flashing point solvent system based on PC as the main solventhas a good application prospect and development value.