Organic carbonate additives for nonaqueous electrolyte rechargeable electrochemical cells

Abstract From the Canadian patent

A lithium ion electrochemical cell having high charge/discharge capacity, long cycle life and exhibiting a reduced first cycle irreversible capacity is described. The, stated benefits are realized by the addition of at least one carbonate additive to an electrolyte comprising an alkali metal salt dissolved in a solvent mixture that includes ethylene carbonate and an equilibrated mixture of dimethyl carbonate ethylmethyl carbonate and diethyl carbonate. The preferred additive is either a linear or cyclic carbonate containing covalent O-X and O-Y bonds on opposite sides of a carbonyl group wherein at least one of the O-X and the O-Y bonds has a dissociation energy less than about 80 kcal/mole.