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March 11, 2022
"Lithium battery" is a type of battery that uses lithium metal or lithium alloy as the negative electrode material and uses a non-aqueous electrolyte solution. In 1912, the lithium metal battery was first proposed and studied by GilbertN.Lewis. In the 1970s, M.S.Whittingham proposed and began to study lithium-ion batteries. Due to the very active chemical properties of lithium metal, the processing, storage and use of lithium metal have very high environmental requirements. Therefore, lithium batteries have not been used for long time. With the development of science and technology, lithium batteries have now become the mainstream.
Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium-ion batteries do not contain lithium in the metallic state and are rechargeable. The fifth generation of rechargeable batteries, lithium metal batteries, was born in 1996, and its safety, specific capacity, self-discharge rate and performance-price ratio are better than lithium-ion batteries. Due to its own high technical requirements, only companies in a few countries are now producing such lithium metal batteries.
Battery cycle life
Lithium-ion batteries can only be charged and discharged 500 times?
I believe that most consumers have heard that the life of a lithium battery is "500 times", and 500 times of charge and discharge. After this number of times, the battery will "end of life". In order to prolong the life of the battery, many friends always use Does it really prolong the life of the battery by charging it when the battery is completely depleted? the answer is negative. The life of a lithium battery is "500 times", which refers not to the number of times of charging, but a cycle of charging and discharging.
A charging cycle means that all the power of the battery is fully charged from full to empty, and then charged from empty to full, which is not equivalent to charging once. For example, a lithium battery is only half charged on the first day, and then fully charged. If the next day is still the same, that is, half of the charge, a total of two charges down, this only counts as one charge cycle, not two. Therefore, it may usually take several charges to complete a cycle. Each time a charge cycle is completed, the battery capacity decreases a little. However, this reduction in power is very small. High-quality batteries will still retain 80% of their original capacity after being charged for many cycles. Many lithium-ion battery-powered products are still used as usual after two or three years. Of course, the lithium battery still needs to be replaced after the end of its life.
The so-called 500 times means that the manufacturer has achieved about 625 rechargeable times at a constant depth of discharge (such as 80%), reaching 500 charging cycles.
(80%*625=500) (ignoring factors such as the reduction of lithium battery capacity)
However, due to various influences in real life, especially the depth of discharge during charging is not constant, "500 charging cycles" can only be used as a reference battery life.
Correct statement: Lithium battery life is related to the number of completed charging cycles, not directly related to the number of charging cycles.
Simple understanding, for example, a lithium battery is only half charged on the first day, and then it is fully charged. If the next day is still the same, that is, half of the charge, a total of two charges down, this only counts as one charge cycle, not two. Therefore, it may usually take several charges to complete a cycle. Each time a charge cycle is completed, the charge decreases a bit. However, the reduction is very small. High-quality batteries will still retain 80% of the original power after being charged for many cycles. Many lithium-ion battery-powered products are still used as usual after two or three years. This is the reason. Of course, the lithium battery will eventually need to be replaced when the life of battery ends.
The life of lithium batteries is generally 300 to 500 charging cycles. Assuming that the power provided by a complete discharge is Q, if the reduction of power after each charging cycle is not considered, the lithium battery can provide or supplement a total of 300Q-500Q of power during its life. From this, we know that if you charge 1/2 every time, you can charge 600-1000 times; if you charge 1/3 every time, you can charge 900-1500 times. And so on, if charging randomly, the number of times is not fixed. In short, no matter how you charge it, a total of 300Q to 500Q of power is added to the battery. Therefore, we can also understand it this way: the life of lithium batteries is related to the total charging capacity of the battery, and has nothing to do with the number of charging times. Deep discharge and deep charge and shallow discharge and shallow charge have little difference in the impact of lithium battery life.
In fact, shallow discharge and shallow charge are more beneficial for lithium batteries. Only when the power module of the product is calibrated for lithium batteries, it is necessary to conduct discharge and charge deeply. Therefore, products powered by lithium batteries do not have to stick to the process, everything is convenient, and they can be charged at any time without worrying about affecting their lifespan.
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