Lithium Deposition on Graphite and Silicon: Mechanism, Morphology and Reversibility

Abstract

Graphite and silicon are respectively the state-of-the-art and the next-generation anode materials for Li-ion batteries. Li plating is a side reaction that competes with Li insertion when the battery is charged under high rate or low temperature. Li plating is usually regarded as undesirable because of its adverse effect on battery's capacity and safety. Dead lithium can consume the lithium inventory in the Li ion batteries and cause performance degradation. More importantly, Li plating has the tendency to develop into dendrite, short the battery and cause severe safety hazard. Despite of the challenge, there is an emerging trend to intentionally deposit Li in graphite and silicon anode to furthur enhance the anode capacity, therefore increase the energy density of full cells. The key to the success of this new idea is to control the morphology of the Li deposits to achieve desired reversibility and safety. This goal can not be realized without a comprehensive understanding of the mechanism of Li plating on graphite and silicon. In this talk, I will share our latest discovery in elucidating the physics governing the onset of Li plating, the nucleation and growth pf lithium on graphite and silicon.