Meaning
Protective layers applied to the exterior of electrode particles act as a barrier against acidic attacks and secondary electrolyte decomposition. Chemical reactions at the interface are suppressed when cathode surface passivation creates a stable artificial interphase. This layer prevents the leaching of transition metals into the electrolyte, which otherwise leads to the degradation of the anode.
The coating must be thin enough to allow lithium ions to pass through while blocking electrons.
Degradation Control
Hydrofluoric acid generated by moisture in the electrolyte often erodes the active material surface. Effective cathode surface passivation neutralizes these acidic species or provides a sacrificial layer that preserves the underlying crystal structure. Longevity improves because the active sites remain available for reversible lithium storage.
Safety Margin
Thermal stability is enhanced when the reactive surface area of the oxide is isolated from the organic solvent. By reducing the heat generated from exothermic side reactions, cathode surface passivation raises the temperature at which thermal runaway begins. Protection is improved for high nickel chemistries which are inherently more reactive.
Commercial Viability
Coating processes like atomic layer deposition or chemical vapor deposition add cost but reduce the need for expensive electrolyte additives. Selecting the right cathode surface passivation technique allows manufacturers to use higher voltages without compromising the safety of the cell.
