Lithium plating is a Cell capacity fade (i. e., a Cell degradation) mechanism, through the Loss of lithium inventory. Instead of intercalating into anode, Lithium forms metal compound on the surface of the anode (below the SEI layer on anode).
Lithium plating affects four key characteristics of cells: life-time, low-temperature performance, how fast they can be charged, and the safety. [2]
A physical precondition of Lithium plating is that the standard electrode potential of Lithium intercalating into graphite anode (–2.84) is close to the potential of Lithium metal formation (–3.04).
The insertion potential of Lithium ions in graphite is in the range of 200 to 65 mV vs. Li/Li+ [metal deposition]. [2]
The potential of Lithium intercalation decreases, and, hence, the risk of Lithium plating increases when charging either 1) at low temperature (esp. below zero), 2) with strong current, 3) at high State-of-charge level (esp. overcharging). These lead to increased concentration of Lithium close to the surface of the anode.
Lithium plating reduces the Lithium inventory in the electrolyte. It can also crack the SEI layer and grow into dendrites.
Lithium plating is one of the reasons why cells have Coulombic efficiency less than 1.0.
On some cell, Lithium plating happens at some part of the cell (closer to the separator) at 1C charge rate when the state-of-charge is 70% of higher (the chart below is for 1C charge rate):
Thinner anode is less susceptible to Lithium plating because of the smaller overall difference in Lithium concentration surrounding anode particles near the current collector (lowest concentration) and particles near the separator (highest concentration). Anode particles which are close to the separator also reach high state-of-charge sooner than the particles which are close to the current collector. This will also contribute to uneven Lithium plating.
**Frequent rest recovers capacity and prolongs a cell's life because Lithium plating is a self-reinforcing process**, therefore, preventing it early leads to compounding benefits.
This effect is pronounced when a cell is cycled non-stop:
