"Lithium battery" is a kind 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 Gilbert N. Lewis. In the 1970s, M.S. Whittingham proposed and started Research on 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 a long time. With the development of science and technology, lithium batteries have been became 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 Life



Lithium-ion batteries can only be charged and discharged 500 times?
I believe that most consumers have heard that the life of lithium batteries is "500 times", and 500 times of charging and discharging, beyond this number of times, the battery will "end of life", many friends in order to prolong the life of the battery, every time in 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 the battery is fully charged from full to empty, and then 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 it's still the same the next day, that's half of the charge, for a total of two charges, which 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 it's still the same the next day, that's half of the charge, for a total of two charges, which 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 life will eventually need to be replaced.



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 this: 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, is it necessary to deep 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.



If the lithium battery is used in an environment higher than the specified operating temperature, that is, above 35°C, the power of the battery will continue to decrease, that is, the battery will not last as long as usual. If the device is charged at such a temperature, the damage to the battery will be even greater. Even if the battery is stored in a hot environment, it will inevitably cause corresponding damage to the quality of the battery. Therefore, trying to maintain a suitable operating temperature is a good way to extend the life of lithium batteries.



If the lithium battery is used in a low temperature environment, that is, below 4°C, the battery life will also be reduced, and the original lithium battery of some mobile phones cannot even be charged in a low temperature environment. But don't worry too much, this is only a temporary situation, different from the use in a high temperature environment, once the temperature rises, the molecules in the battery are heated and immediately return to the previous power level.



To get the most out of a lithium-ion battery, you need to use it frequently so that the electrons in the lithium-ion battery are always in a state of flow. If you do not use the lithium battery often, please remember to complete a charging cycle for the lithium battery every month and do a power calibration, that is, deep discharge and deep charging.



The formal name is "charge-discharge cycle", which is not equal to "charge times". The cycle refers to the time when the battery is fully charged to run out. This is a cycle. If your battery is fully charged, one tenth is used. This is a tenth of a cycle, so 10 times of charging is basically a cycle. Similarly, from fully charged, half used and then fully charged, and then half used and then fully charged, this is also a cycle. At this time, you have charged twice. So, the cycle only depends on "how much power is discharged from the battery", and has no direct relationship with "number of charges".



Moreover, the nominal number of charge and discharge cycles does not mean that it cannot be used after it is used up, but after so many cycles, the ability of the battery to store electricity will drop to a certain extent.



For example, for a lithium battery, the nominal charge-discharge cycle is "not less than 60% of the nominal capacity after 500 cycles"



That is to say, after 500 cycles, the battery can only store as much as 60% of the power of the new battery, which means that the performance has dropped to a certain extent.



There is no fixed charge limit for lithium batteries. The batteries from regular manufacturers can generally be charged and discharged at least 500 times, and the capacity remains above 80% of the initial capacity. One charge a day can be used for 2 years. Usually, the mobile phone battery is charged 1000 times, which will cause the battery to be seriously insufferable.



Mobile phone battery maintenance method:



1. Use fully charged each time, reduce the number of charging times and improve the battery life.



2. Do not fully discharge the battery, usually it needs to be charged when the power is less than 10%.



3. Use the original charger to charge, do not use the universal charger to charge.



4. Do not use the phone while the phone is charging.



5. Do not overcharge, stop charging after the battery is fully charged.



Yes, according to the experimental results, the life of the lithium battery is continuously attenuated with the increase of the number of charging times. Generally, the number of charging times of the lithium battery is 2000-3000 times.



Cycle is use. We are using the battery, and we care about the time of use. In order to measure the performance of how long the rechargeable battery can be used, the definition of the number of cycles is specified. Actual user usage is ever-changing, because tests with different conditions are not comparable, and the definition of cycle life must be standardized if there is a comparison.



Lithium battery cycle life test conditions and requirements specified by the national standard: under the condition of ambient temperature of 20℃±5℃, charge at 1C, when the battery terminal voltage reaches the charging limit voltage of 4.2V, change to constant voltage charging until the charging current is less than or equal to 1/20C, stop charging, leave it for 0.5h~1h, then discharge with 1C current to the final voltage of 2.75V, after discharge, leave it for 0.5h~1h, and then proceed to the next charge-discharge cycle until two consecutive discharge times If it is less than 36min, it is considered that the life is terminated, and the number of cycles must be greater than 300 times.



Interpretation of the national standard regulations:



A. This definition stipulates that the test of cycle life is carried out in the way of deep charge and deep discharge



B. The cycle life of lithium batteries is stipulated. According to this mode, the capacity is still more than 60% after ≥300 cycles



However, the cycle times obtained by different cycle systems are completely different. For example, the above other conditions remain unchanged. Only change the constant voltage of 4.2V to the constant voltage of 4.1V to test the cycle life of the same type of battery. In this way, this battery is no longer a deep charge method, and the final test shows that the cycle life can be increased by nearly 60%. Then if the cut-off voltage is increased to 3.9V for testing, the number of cycles should be increased several times.



This statement about the cycle of charging and discharging once is one less life. What we should pay attention to is the definition of the charging cycle of lithium batteries: a charging cycle refers to all the power of the lithium battery from full to empty, and then from empty to full. the process of. And that doesn't equate to a single charge. In addition, when talking about the number of cycles, you can't ignore the conditions of the cycle. It is meaningless to talk about the number of cycles aside from the rules, because the number of cycles is a means to detect battery life, not an end!