Lithium-ion batteries are constantly degrading—even when they’re not in use—simply as a consequence of time and thermodynamics. This is referred to as calendar aging Battery calendar aging is the effects of time on battery health.
State of Charge In lithium-ion batteries, battery degradation due to SOC is the result of keeping the battery at a certain charge level for lengthy periods of time, either high or low. This causes the general health of battery to gradually deteriorate.
Since this is a known phenomenon, many lithium-ion battery manufacturers will give their batteries a rating according to their cycling-based degradation. For example, a battery may be rated as being able to complete 1,000 full cycles before it degrades from full capacity to 80% capacity.
Lithium-ion batteries unavoidably degrade over time, beginning from the very first charge and continuing thereafter. However, while lithium-ion battery degradation is unavoidable, it is not unalterable. Rather, the rate at which lithium-ion batteries degrade during each cycle can vary significantly depending on the operating conditions.
And aging will cause short circuit which generates heat and gas. However, there are many factors will cause this kind of phenomenon. The swollen of lithium battery is mainly related to battery quality, battery using methods, environment and many other factors. The following are some reasons which cause batteries swell from three aspects.
The cycle of charging and discharging plays a large role in lithium-ion battery degradation, since the act of charging and discharging accelerates SEI growth and LLI beyond the rate at which it would occur in a cell that only experiences calendar aging. This is called cycling-based degradation.