Effects of SEI on the kinetics of lithium intercalation

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