Briefly describe the cycle life of lithium-ion batteries
Regarding an ideal lithium-ion battery, the balance of content in its cycle will not change, and the initial capacity in each cycle should be a certain value, but the situation is actually much more complicated. Any side reaction that can occur or consume lithium ions may lead to a change in the battery capacity balance. Once the battery capacity balance changes, this change is irreversible and can be accumulated through multiple cycles, which will seriously affect the battery cycle performance. influences.
The life of a lithium ion battery means that the capacity of the battery decays to 70% of the nominal capacity after a period of use, and the life is considered to be terminated. During use, an irreversible electrochemical reaction occurs inside the lithium-ion battery, which leads to a decrease in capacity. Experiments show that a higher rate discharge will cause a faster capacity decay. If the discharge current is low, the battery voltage will be close to the equilibrium voltage. Can release more energy.
The theoretical life of lithium ion batteries is about 800 cycles, which is medium among commercial rechargeable lithium ion batteries. Lithium iron phosphate is about 2,000 cycles, while lithium titanate is said to be able to reach 10,000 cycles. At present, mainstream battery manufacturers promise more than 500 times in their battery cell specifications, but after the cells are assembled into a battery pack, due to consistency issues, it is important that the voltage and internal resistance cannot be exactly the same, and its cycle life About 400 times.
At this stage, my country’s automobile industry is developing rapidly, and even consumers of fuel vehicles may not use them for more than 10 years. The same principle applies to electric vehicles. There are car companies’ warranty commitments for problems with normal use, and the cycle life of power lithium batteries is far Beyond the service life. This principle also applies to the purchase of second-hand electric vehicles, so in the entire life cycle of electric vehicles, the matter of replacing the battery is far less bad than imagined.
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