USE OF CHLOROETHYLENE CARBONATE AS ON ELECTROLYTE SOLVENT FOR A GRAPHITE ANODE IN A LITHIUM-ION BATTERY

The electrolyte decomposition during the first lithiation of graphite is reduced to 90 mAh/g in an electrolyte containing equal volumes of c hloroethylene carbonate and a cosolvent of propylene carbonate, dimeth yl carbonate, or diethyl carbonate. The Volume fraction of chloroethyl ene carbonate can be further reduced to 0.05 in a trisolvent system wi th a cosolvent containing equal volumes of ethylene carbonate and prop ylene carbonate. A lithium-ion cell containing chloroethylene carbonat e and propylene carbonate shows a long cycle life. The capacity decrea ses by 20% from the initial value in over 800 cycles. The charging eff iciency is 80 to 90%, is rate dependent, and is accompanied by a self- discharge mechanism. A hypothesis of a chemical shuttle is suggested t o explain the low charge efficiency and self-discharge.