Many factors affect the capacity of lithium-ion batteries, such as operating temperature, charging and discharging current, and charging and discharging cutoff voltage. These factors all influence the rate of capacity degradation in lithium-ion batteries. The mechanisms causing capacity degradation in lithium-ion batteries can be divided into three categories: increased internal resistance and polarization, loss of active materials at the positive and negative electrodes, and lithium loss.
Different external factors have varying effects on these three components. For example, lithium-ion batteries made of LiFePO4 material have excellent cycle performance, but different usage conditions have a significant impact on the cycle life of lithium-ion batteries.
Tests have shown that 15C pulse discharge and 15C continuous discharge have completely different effects on 26650 lithium-ion batteries. The capacity of a 26650 lithium-ion battery undergoing 15C pulse discharge decreases very rapidly; after 40 charge-discharge cycles, it can no longer be discharged at 15C, but it can still be discharged at 1C. In contrast, the capacity of a battery undergoing 15C continuous discharge decreases more slowly; after 60 cycles, it can still be discharged at 15C, but the capacity degradation rate at 1C is faster than that at 15C pulse discharge.
Lithium-ion battery processing and customization
Research on the impact of charging strategies on the lifespan degradation of lithium-ion batteries can better guide our lithium-ion battery design. The following study investigates the effects of different charging control strategies on the lifespan degradation of lithium-ion batteries, explores their application mechanisms, and proposes a lifespan degradation model for lithium-ion batteries.
Mechanism analysis concludes that the 15C pulse discharge battery produces more LiF in the SEI film of the negative electrode. LiF further hinders lithium ion diffusion, causing a rapid increase in the battery's Li+ diffusion resistance and charge exchange resistance. This results in excessive polarization voltage during charging and discharging, leading to a rapid decrease in the high-current discharge capability of LiFePO4.
