Patent ID: 6746804
Filing Date: 2004-06-08
Classification: H01M,Y02E,Y10T

Abstract:
An electrochemical cell, which comprises:a) a negative electrode of a negative electrode active material which intercalates and deintercalates with an alkali metal; b) a positive electrode comprising an alkali metal intercalated electrode active material which intercalates and deintercalates with the alkali metal; c) an electrolyte solution activating the negative and positive electrodes, the electrolyte (including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1âˆ’a% of DEC and with the negative electrode deintercalated with the alkali metal and the positive electrode intercalated with the alkali metal before being activated with the electrolyte, the DMC, EMC and DEC are in an essentially equilibrated mixture, by molar percent, as determined by the formula: [EMC]2/([DMC][DEC]) equal to about 4.0Â±0.15 and wherein in the equilibrated molar mixture, the rate at which ethyl methyl carbonate is producible from dimethyl carbonate and diethyl carbonate by an ester exchange reaction is essentially equal to the rate at which ethyl methyl carbonate is disproportionable into dimethyl carbonate and diethyl carbonate such that the equilibrated molar mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate essentially does not change as the cell discharges.