Meaning
Thermodynamic states where the concentration of atomic vacancies exceeds the equilibrium level for a given temperature drive structural changes in metal anodes. When lithium is removed from an electrode surface at a high rate, vacancy supersaturation occurs because the atoms cannot redistribute fast enough to fill the empty sites. This imbalance creates a high chemical potential that favors the formation of voids and the eventual detachment of the electrode from the separator.
Diffusion Limit
The maximum speed at which atoms can move through the metal lattice sets the boundary for stable operation. When the stripping current exceeds this limit, the concentration of vacancies at the surface rises quickly, leading to the unstable growth of surface defects.
Temperature Effect
Higher temperatures increase the mobility of atoms and allow for a faster redistribution of vacancies. This higher mobility reduces the likelihood of reaching a state of supersaturation, which allows the battery to operate at higher currents without forming voids at the interface.
Surface Stability
Maintaining a stable interface requires balancing the stripping rate with the self-diffusion of the metal. If the supersaturation is not controlled, the surface of the lithium becomes porous, which increases the risk of dendrite formation during the next charging cycle.
