Stability of Solid Electrolyte Interphase Components on Lithium Metal and Reactive Anode Material Surfaces

摘要

Lithium ion batteries (LIB) can feature reactive anodes that operate at lowpotentials, such as lithium metal or silicon, passivated by solid electrolyteinterphase (SEI) films. SEI is known to evolve over time as cycling proceeds.In this modeling work, we focus on the stability of two main SEI components,lithium carbonate (Li2CO3) and lithium ethylene dicarbonate (LEDC). Bothcomponents are electrochemically stable but thermodynamically unstable near theequilibrium Li+/Li(s) potential. Interfacial reactions represent one way totrigger the intrinsic thermodynamic instability. Both Li(2)CO(3) and LEDC arepredicted to exhibit exothermic reactions on lithium metal surfaces, and thebarriers are sufficiently low to permit reactions on battery operation timescales. LEDC also readily decomposes on high Li-content Li(x)Si surfaces. Ourstudies suggest that the innermost SEI layer on lithium metal surfaces shouldbe a thin layer of Li(2)O -- the only thermodynamically and kinetically stablecomponent (in the absence of a fluoride source). This work should also berelevant to inadvertant lithium plating during battery cycling, and SEIevolution on Li(x)Si surfaces.