Theoretical study of the reductive decomposition of ethylene sulfite: a film-forming electrolyte additive in lithium ion batteries.

The role of ethylene sulfite (ES) as an electrolyte additive for lithium ion batteries is explained by investigating the one- and two-electron reductive decomposition of ES and (ES)Li(+)(PC)(n) (n = 0-2), both in vacuum and solvent, with the aid of high-level density functional theory calculations. The open-chain radical, which is formed as a result of reduction of ES in solvent without first being coordinated with Li(+), is further stabilized by a dissolved lithium ion. The resulting more stable intermediate releases a somewhat large amount of energy, which is utilized in the formation of a subsequent radical anion. On the basis of the study on the reductive decomposition of ES, (ES)Li(+)(PC), and (ES)Li(+)(PC)(2), the major products that are responsible for the formation of a protective solid electrolyte interphase film are Li(2)SO(3), (CH(2)OSO(2)Li)(2), CH(3)CH(OSO(2)Li)CH(2)OCO(2)Li, and ROSO(2)Li.