With the development of science and technology and the maturity of technology, the application of lithium-ion batteries has become more and more extensive. At present, the life test method widely used in the development, inspection and selection of lithium-ion batteries is to perform cyclic testing under certain working conditions.
The attenuation of the cycle life of a lithium-ion battery is actually a changing trend of the current actual available capacity of the battery, relative to its rated capacity when it leaves the factory. There are many factors that affect the cycle life of lithium-ion batteries. The fundamental reason is that the number of lithium ions involved in energy transfer is constantly decreasing. It should be noted that the total amount of lithium in the battery has not decreased, but the “activated” lithium ions are less, they are imprisoned in other places or the channels of activity are blocked, and they cannot freely participate in the cycle of charging and discharging. process.
Cycle life refers to the number of times a battery can be fully discharged and charged within a specified temperature range before it must be replaced. Once the fully charged battery capacity is less than 80% of its nameplate capacity, the battery cannot be used for the application and should be replaced.
For traditional sealed lead-acid batteries, the cycle life is between 200 and 400 cycles, and typical lithium-ion batteries used in UPS applications can survive more than 1,000 cycles. The number depends on several factors, including the specific chemistry used in the design. At present, some lithium-ion batteries can be used for more than 5000 cycles.
Table : Comparison of various Li-ion batteries with different chemistry types.
|Specific energy||Specific power||Safety*||Performance||Lifespan||Cost|
Note*: Safety refers to how resistant the chemistry is to entering an uncontrolled state or “thermal runaway” situation.