Electrolyte additive for protecting lithium cell from overcharge and overdischarge

The invention provides an electrolyte additive for protecting a lithium cell from overcharge and overdischarge.The electrolyte additive is selected from tert-butyl benzene, tert-amylbenzene or a mixture of the tert-butyl benzene and the tert-amylbenzene. When a cell is regularly charged, the electrolyte additive is participated in to form an SEI film so as to exert an effect of a normal film forming agent and also exert an effect of improving the electric performance; and when the cell is in an overcharge state, the electrolyte additive generates polymerization reaction in the cell, and a diaphragm is closed in advanced due to the heat generated by the polymerization reaction, thus the internal resistance of the cell is increased so that the voltage of the cell is quickly increased, the oxidation of an electrolyte is avoided, and the purpose of preventing the overcharge is realized.