Overcharge Effect on Morphology and Structure of Carbon Electrodes for Lithium-Ion Batteries

Lithium metal plating on graphite anodes of Li-ion batteries is one of the causes of capacity fading and failure. An overcharge experiment on the graphite anode was conducted and the morphology and structure of graphite were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the failure mechanism of graphite during overcharge is similar to that of the lithium metal electrode. The deposited lithium will react with the electrolyte to form a new solid electrolyte interface (SEI) layer, which will prevent further accessibility during the following cycles. According to SEM and TEM images, this SEI layer shares the same morphologies of the lithium metal electrode during cycling.