While the Solid Electrolyte Interphase (SEI) provides a necessary and stabilizing boundary layer, anomalous chemical behaviors like lithium plating represent a severe degradation mechanism that rapidly accelerates battery aging and introduces critical functional safety risks. Plating fundamentally occurs when the applied charge current outpaces the kinetic ability of lithium ions (Li+) to successfully intercalate into the layers of the graphite anode. Instead of safely embedding within the carbon lattice, the ions receive electrons at the anode surface and reduce into solid metallic lithium. Visually representing this tipping point at the chemical level during the charging phase is highly effective for battery engineers, as understanding the exact moment standard intercalation breaks down is crucial for designing safe fast-charge limits. If left unmanaged by the Battery Management System (BMS), chronic plating permanently bottlenecks the pack’s State of Health (SoH) and sharply increases internal DC resistance (DCIR).

Key engineering and chemical dynamics of lithium plating:

• The Intercalation vs. Deposition Threshold: Plating is an overpotential phenomenon. It strictly occurs when the localized electrochemical potential of the graphite anode drops below $0\text{V}$ relative to the standard Li/Li+reference electrode. This is most frequently triggered by high C-rate fast charging, where ions pile up at the anode-electrolyte interface faster than diffusion kinetics can pull them into the graphite structure.

• Cold Weather Exacerbation: Temperature is the primary operational catalyst for lithium plating. At sub-zero temperatures, the solid-state diffusion of lithium ions within the graphite lattice slows to a crawl, and the viscosity of the bulk electrolyte increases. Applying high charge currents in these cold states almost guarantees surface metallization, making cold-weather charge derating a mandatory safety requirement in EV engineering.

• Dead Lithium and Irreversible Capacity Fade: During the subsequent discharge cycle, some of the plated metallic lithium can be stripped back into ionic form. However, a significant portion chemically reacts with the electrolyte or becomes physically disconnected from the electron-conducting matrix. This orphaned material is termed “dead lithium,” permanently locking away active charge carriers and immediately driving down the total usable capacity of the battery.

• Dendrite Formation and BMS Modeling: Plated lithium rarely forms a smooth, uniform layer; it tends to precipitate as sharp, needle-like structures called dendrites. Over repeated cycles, these dendrites can physically pierce the porous polymer separator, leading to catastrophic internal short circuits and thermal runaway. To prevent this, engineers often deploy complex, object-oriented state estimators—commonly developed in environments like MATLAB and Simulink—to model localized anode potentials in real-time, allowing the BMS to dynamically choke back the charging current before the plating threshold is ever breached.