Lithium plating

Lithium plating occurs when lithium deposits as metal on the anode surface instead of entering the graphite. It is most likely when charging at low temperature, high current or high SOC, and it can cause rapid, partly irreversible capacity loss.

What plating is

During charging, lithium ions normally slip in between the graphite layers of the anode. If they arrive faster than they can be absorbed, or the anode potential drops too low, some lithium deposits as metal on the surface instead. Part of this metal can later re-enter the graphite, but part reacts with the electrolyte or becomes electrically isolated and is lost for good.

Lost lithium means lost capacity, and plating can also accelerate other degradation. In severe cases plating is associated with safety concerns, which is one reason battery management systems control charging conditions carefully.

The three risk factors

Reviews of the plating literature consistently identify three conditions that raise the risk. Their effects compound, so the combination matters more than any single factor.

Low-temperature studies show that charging in the cold can produce substantial plating-related ageing. Research on fast charging describes plating as the central obstacle to combining high energy density, fast charging and long cycle life.

Low temperature: slower diffusion and reaction kinetics in the anode.
High charging current: more lithium arriving per second than the graphite can absorb.
High SOC: the anode is already well filled and its potential is closer to the plating threshold.

Warmth as a countermeasure

Raising the cell temperature during fast charging can suppress plating, because diffusion speeds up and the anode can absorb lithium more quickly. This is the scientific basis for preconditioning the battery before fast charging. The trade-off is that sustained high temperatures accelerate SEI growth, so the goal is a suitable charging temperature, not maximum heat.

What it means in practice

Vehicle BMS software limits charging current when the pack is cold or nearly full, precisely to manage plating risk. The margins each manufacturer chooses differ, however, and are not public. Voltgevity treats cold, high-current and high-SOC charging as higher battery stress, and approximates plating-related risk from estimated pack temperature, effective C-rate and SOC during charging. Because plating is hard to observe directly in a vehicle, these estimates carry substantial uncertainty.

Key takeaways

Lithium plating is metallic lithium deposited on the anode, causing partly irreversible capacity loss.
Cold cells, high current and high SOC raise the risk, and their effects compound.
Warming the pack before fast charging reduces plating risk, which is why preconditioning helps.
The BMS manages plating risk, but its margins are vehicle-specific and undisclosed.