The term "lithium-ion battery life" refers to the period when the battery capacity drops to 80% of its rated capacity, at which point the battery's lifespan ends. However, even when the charge capacity is below 80%, although the operating time is shortened, the battery can still provide usable power.
The degradation of lithium-ion battery cycle life is essentially the continuous decrease in the battery's current usable capacity relative to its original rated capacity. Generally, the lifespan of a lithium-ion battery is defined as the number of cycles required for its capacity to drop to 80% of its initial capacity.
Ideally, a lithium-ion battery's capacity balance should remain unchanged throughout its cycle, with a constant initial capacity in each cycle. However, the reality is far more complex. Any side reaction that generates or consumes lithium ions can alter the battery's capacity balance. Once this balance is changed, it is irreversible and can accumulate over multiple cycles, severely impacting the battery's cycle performance.
Regarding battery life, the lifespan of lithium-ion batteries in ordinary electronic products is approximately 5 to 20 years, with an average of 8 years. However, with current technology, the lifespan of lithium-ion batteries in electric vehicles is only about 3 to 5 years.
Many factors affect the cycle life of lithium-ion batteries, but the fundamental reason is the continuous decrease in the number of lithium ions involved in energy transfer. It's important to note that the total amount of lithium in the battery hasn't decreased; rather, fewer lithium ions are activated. These ions are either trapped elsewhere or their pathways are blocked, preventing them from freely participating in the charge-discharge cycle.
