Effects of SEI on the kinetics of lithium intercalation

The electrochemical stability of electrolytes at lithium, or lithium-interc alating anodes, is achieved via ionically conducting surface films termed a s solid electrolyte interphase (SEI). Since the lithium deposition or inter calation process occurs on the electrode covered with the SEI, the characte ristics of the SEI determine the kinetics of lithiation/delithiation, stabi lity of the interface, and thus, the overall cell performance, especially a t low temperatures. In this paper, we have reiterated the significance of t he SEI characteristics over the solution properties, using a few illustrati ve examples from our research on low temperature Li ion battery electrolyte s at JPL. The examples specifically include the beneficial aspects of a ter nary carbonate mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) compared to the binary mixtures (of EC and eit her DMC or DEC) and quaternary solutions with appropriate co-solvents, such as alkyl esters. Published by Elsevier Science B.V.