Ternary lithium-ion batteries are the fastest-growing type of rechargeable battery after nickel-cadmium and nickel-metal hydride batteries. The application of lithium-ion batteries largely depends on the stability of their charge-discharge cycles. Like other rechargeable batteries, capacity decay during cycling is unavoidable.
High-rate charging and discharging can also cause capacity loss in ternary lithium-ion batteries. This is because the positive and negative electrodes will shrink and expand in volume during the charging and discharging process. The larger the charging and discharging current, the more violent the shrinkage and expansion, and the greater the stress. As a result, the particles of the positive and negative electrodes are more likely to break or peel off from the current collector during rapid volume changes, leading to faster cycle decay.
Temperature is definitely one of the key factors affecting the lifespan of ternary lithium-ion batteries. Excessively high or low temperatures will reduce the content of active lithium ions, thereby reducing the lifespan of lithium-ion batteries.
The essence of capacity decay in ternary lithium-ion batteries is the reduction in the content of lithium ions that can be intercalated or deintercalated. Key factors include structural damage or deactivation of the positive and negative electrode materials, electrolyte decomposition, and misuse of lithium-ion batteries. The charging and discharging process of a battery is a complex electrochemical process, and the factors leading to capacity decay are not singular. Furthermore, deterioration in one aspect may trigger other factors that collectively affect the battery's capacity, cycle performance, energy density, and other parameters.
The theoretical lifespan of ternary lithium-ion batteries is approximately 800 cycles, which is moderate among commercially available rechargeable lithium-ion batteries. Lithium iron phosphate batteries have a lifespan of about 2000 cycles, while lithium titanate batteries are said to reach 10,000 cycles. Currently, mainstream battery manufacturers promise more than 500 cycles (standard charge/discharge conditions) in their ternary cell specifications. However, after cells are assembled into lithium-ion battery packs, due to consistency issues—importantly, voltage and internal resistance cannot be completely identical—the cycle life is approximately 400 cycles. Manufacturers recommend a SOC (State of Charge) window of 10% to 90% and discourage deep charge/discharge, as this can cause irreversible damage to the positive and negative electrode structures. If calculated using shallow charge/discharge, the cycle life is at least 1000 cycles.
Based on current ternary lithium-ion battery technology, if used properly, it can last at least 5 years in electric vehicles. However, if used improperly, the battery's lifespan will be exhausted in 2-3 years. Proper use depends on adhering to the principle of shallow charging and discharging, avoiding overuse.
Theoretically, the lifespan of a ternary lithium-ion battery is 2000 charge-discharge cycles. Even assuming one charge per day, it can last for more than 5 years. However, actual usage differs from the theoretical estimate. After 1000 charge-discharge cycles, the ternary lithium-ion battery will have already degraded by 50%, meaning that a full charge will only allow it to travel half the original range.
