Insights into the Crossover Effects in Cells with High-Nickel Layered Oxide Cathodes and Silicon/Graphite Composite Anodes

摘要

Silicon anodes are regarded as one of the most promising alternatives to graphite (Gr) anodes due to their ultrahigh capacity, abundance, and low cost. Coupling Si-based anodes with high-nickel layered oxide cathodes LiNixMnyCo1-x-yO2 (NMC, x = 0.8) can enhance the driving range for electric vehicles. Transition-metal (TM) ion dissolution and deposition has been a long-known failure mode for Gr-based lithium-ion batteries. However, the mechanistic insight associated with TM ion deposition on Si-based anodes has rarely been reported. Herein, the impact of in situ deposited TM ions on SiOx/Gr composite anodes and the individual influences of Ni, Mn, and Co on the structural and electrochemical stability along with the underlying degradation mechanisms are presented. TM ion dissolution causes a greater deleterious impact on Si than on Gr, with different TM ions exhibiting different influences on anode-electrolyte interphase formation. Specifically, Ni deposit induces more aggressive salt decomposition; Co deposit has negligible effect on salt decomposition, but significantly accelerates solvent decomposition; and Mn deposit aggravates both salt and solvent decompositions, resulting in worse full cell performance. The extent of degradation decreases in the order Mn2+ Ni2+ Co2+. The systematic comparisons presented can guide further development of high energy systems.