Abstract
Electrochemical degradation on Si anodes prevents them from being successfully used in
lithium-ion full cells. Unlike the case of graphite anodes, natural solid electrolyte interphase (SEI)
films generated from carbonate electrolyte do not self-passivate on Si and causes continuous
electrolyte decomposition. In this work we aim at solving the issue of electrochemical
degradation by fabricating artificial SEI films using a solid electrolyte material, lithium phosphor
oxynitride (Lipon), that conducts Li ions and blocks electrons. For Si anodes coated with Lipon
of 50 nm or thicker, significant effect is observed in suppressing the electrolyte decomposition,
while Lipon of thinner than 40 nm has little effect. Ionic and electronic conductivity
measurement reveals that the artificial SEI is effective when it is a pure ionic conductor, and the
electrolyte decomposition is not suppressed when the artificial SEI is a mixed electronic-ionic
conductor. The critical thickness for this transition in conducting behavior is found to be 40~50
nm. This work provides guidance for designing artificial SEI for high capacity lithium-ion
battery electrodes using solid electrolyte materials.
