What are normal Lithium-ion cell ageing process

*Ageing Process: cell performance gradually deteriorates due to unwanted chemical reaction physical change to the active chemical. (Desired chemical reaction where lithium exits one electrode and enter into electrolytes and then into other electrode)

1. Corrosion: (undesired chemical reaction with environment) consume some active chemical in cell leading to increase impendence and capacity fade.
2. Crystal formation: Electrode particles evolve as larger crystal are formed. This reduce the effective surface area of the electrode and hence their current carrying and energy storage capacity.
3. Dendrites growth: Formation of treelike structure on electrode, which can ultimately pierce separator and cause short circuit.

This is similar way crystal formation but in crystal formation, Active material themselves some how merging together and forming larger crystal. when we are taking about dendrites (undesirable crystal that are not the active materials)

4. Chemical loss through evaporation: Gaseous product resulting from over-charging are lost to atmosphere causing capacity loss .

(Lithium-ion if cell over-charge and over-discharge the electrolyte can break down and form gases including hydrogen gas and methane gas and other.)

5. Passivation: Growth of resistance film layer that build up on the electrodes, impeding the chemical action of cell.

(which is the formation of SEI film layer, this film layer is known as passivation layer because when it form on surface of negative electrode particles.)