Stabilizing Capacity Retention of Li-Ion Battery in Fast-Charge by Reducing Particle Size of Graphite

Abstract

Li plating at the graphite anode and the resultant reaction with electrolyte solvents is a mainstream mechanism for the performance degradation of Li-ion batteries in fast-charge. In this work, we assemble two-electrode and three-electrode graphite/LiNi0.8Co0.1Mn0.1O2 Li-ion cells with a relatively low cathode-to-anode capacity ratio to avoid Li plating, finding that the breakage of solid electrolyte interphase on the surface of the graphite anode and the resultant structural exfoliation of graphite and progressive decomposition of electrolyte solvents play a critical role in the performance degradation. Such breakage is suppressed by reducing the particle size of graphite. However, the reduction in the particle size of graphite does not show significant improvement on the charging rate capability of Li-ion cells because the LiNi0.8Co0.1Mn0.1O2 cathode is the rate-determining component. Owing to the weak Van der Waals forces between the layered graphene stacks of graphite, the large particle size of graphite can be easily reduced by increasing the milling time in the slurry-making process of the graphite electrode. The results of this work shed new insight into the performance degradation of Li-ion batteries in fast-charge, and suggest a direction for stabilization of capacity retention.