As a battery is used and recharged, it gradually loses its original capacity. Its life cycle refers to the number of charge and discharge cycles it can complete before performance declines.
Does cycling lithium-ion batteries cause capacity degradation?
Cycling lithium-ion batteries causes capacity degradation and changes in the open-circuit voltage curve due to the loss of LAM and LLI. Karger et al. devised an empirical calendar aging model addressing capacity degradation and open-circuit voltage curve changes in cycling lithium-ion batteries.
In 2003 it was reported the typical range of capacity loss in lithium-ion batteries after 500 charging and discharging cycles varied from 12.4% to 24.1%, giving an average capacity loss per cycle range of 0.025β0.048% per cycle.
Wang et al. uncovered a power law correlation between battery capacity loss and charge throughput and developed a cycle life model based on it. Their equation shows that capacity loss follows a power law relationship with time or load flow, while an Arrhenius correlation accounts for temperature effects.
How do you describe battery degradation?
Battery degradation can be described using three tiers of detail. Degradation mechanisms describe the physical and chemical changes that have occurred within the cell. Mechanisms are the most detailed viewpoint of degradation but are also typically the most difficult to observe during battery operation.
Hoog et al. documented a lifetime model for an NMC cell for the automotive industry. The paper highlights that capacity loss was notably affected by a 100% DoD and temperature in cycling aging experiments. Wu et al. studied the impact of low temperatures and cycling charging on battery degradation using 5 Ah LFP batteries.
How does C-rate affect capacity loss in a lithium ion battery?
Capacity loss is C-rate sensitive and higher C-rates lead to a faster capacity loss on a per cycle. Chemical mechanisms of degradation in a Li-ion battery dominate capacity loss at low C-rates, whereas, mechanical degradation dominates at high C-rates.