New Insight on Graphite Anode Degradation Induced by Li-Plating

Graphite is the dominant anode material for lithium-ion batteries; however, it still suffers from Li-plating when charging fast or at low temperature, and Li-plating is associated with performance fading and safety concerns. Herein, we clarify the mechanism of lithium evolution from graphite particles by over-lithiation cycle test, in-situ XRD, and titration gas chromatography. We observe that the graphite intercalation compounds (GICs, LiC₁₂ and LiC₆ e.g.) gradually become inactive and wrapped by dead lithium or side reaction sediments, while the rate of this degradation will be accelerated as the overpotential of Li-plating is decreased after initial Li metal nucleation. This understanding is contradictory to the popular one that the degradation of graphite anode after Li plating is mainly caused by the inferior SEI and dead Li induced hindering of Li-ion intercalation. The isolation of lithiated graphite particles leading to the fast vanishing of Li insertion/deintercalation process in graphite anodes. We further study the insertion/deintercalation vanishing process at low temperature and high rates, respectively. This work provides a insight on graphite anode degradation induced by Li-plating, and the new understanding can be used to guide the design of advanced materials and electrodes to avoid Li-plating and achieve extreme fast while safe charging.