Development of an In-Situ Diagnostic to Detect Lithium Plating in Commercial Automotive Battery Cells

Lithium plating refers to the phenomenon where lithium metal is deposited onto the surface of the anode instead of being intercalated into the carbon sites of the graphite. The lithium metal will cover a portion of the surface area of the anode, which blocks intercalation sites and increases charge gradients. Lithium plating most often occurs when charging the battery at low ambient temperatures or at a high current rate, but lithium plating formation has also been linked to solid electrolyte interface (SEI) growth towards the later stages of life. Lithium plating may significantly reduce a battery cell’s performance in terms of charge capacity, and if severe enough, the lithium metal may form a bridge across the separator of the cell, leading to short circuits and potential safety concerns. The internal research performed by Southwest Research Institute explored how to create a battery model to detect the formation of lithium plating in real time. In conjunction with the battery model, a controller was developed to help define a safe and fast charge profile. The controller used a cost function to balance the coulombic efficiency versus lithium plating to ‘learn’ an optimized charge profile for a nickel manganese cobalt (NMC) pouch cell used in a passenger vehicle. Results have indicated the optimized charge profile is capable of reducing the overall charge time by approximately 37% when compared to the original equipment manufacturer (OEM) Level 3 fast charge profile, and it showed significantly improved capacity retention when compared to a constant current constant voltage (CCCV) baseline cycle.