"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 Gilbert N. 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 a 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 metallic lithium 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 superior to those of lithium-ion batteries. Due to its own high-tech requirements, only a few companies in a few countries are producing such lithium metal batteries.
Battery Life
Li-ion battery 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", 500 times of charge and discharge, beyond this number, the battery will "end of life", many friends in order to be able to extend the battery life, every time The battery is charged only when it is completely exhausted. Does this really extend the life of the battery? the answer is negative. The lifespan of a lithium battery is "500 times", which does not refer to the number of times of charging, but a cycle of charging and discharging.
A charging cycle means the process of using all the power of the battery from full to empty, and then from empty to full. This is not the same as charging once. For example, a lithium battery used only half of its power on the first day, and then it was fully charged. If the situation persists the next day, that is, use half of the charge and charge it twice in total. This can only be counted as one charging cycle, not two. Therefore, it may usually take several times to complete a cycle. Every time a charging cycle is completed, the battery capacity will decrease a bit. However, this reduction in power consumption is very small. A high-quality battery will still retain 80% of its original capacity after being charged for many cycles. Many lithium-powered products will still be 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 charging cycles at a constant depth of discharge (such as 80%), reaching 500 charging cycles.
(80%*625=500) (Ignore factors such as 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.
The correct statement: Lithium battery life is related to the number of completions of the charging cycle, not directly related to the number of charging cycles.
Simple understanding, for example, a lithium battery used only half of its power on the first day, and then fully charged it. If the situation persists the next day, that is, use half of the charge and charge it twice in total. This can only be counted as one charging cycle, not two. Therefore, it may usually take several times of charging to complete a cycle. Every time a charging cycle is completed, the power will decrease a bit. However, the reduction is very small. High-quality batteries will still retain 80% of the original power after being charged for multiple cycles. Many lithium-powered products are still used as usual after two or three years. This is the reason. Of course, the life of the lithium battery needs to be replaced in the end.
The life of a lithium battery is generally 300 to 500 charging cycles. Assuming that the power provided by a complete discharge is Q, if the reduction in power after each charging cycle is not considered, the lithium battery can provide or supplement 300Q-500Q of power in its life. From this we know that if you charge 1/2 each time, you can charge 600-1000 times; if you charge 1/3 each time, you can charge 900-1500 times. By analogy, if it is charged randomly, the number of times is variable. In short, no matter how it is charged, it is constant to add a total of 300Q to 500Q of power. Therefore, we can also understand it this way: the life of a lithium battery is related to the total charge capacity of the battery, and has nothing to do with the number of charges. Deep discharge and deep charge and shallow discharge and shallow charge have little difference in the impact on the life of the lithium battery.
In fact, shallow charging and shallow charging are more beneficial to lithium batteries. Only when the product's power module is calibrated for lithium batteries, it is necessary to deep discharge and deep charge. Therefore, products powered by lithium batteries do not need to be constrained by the process. Everything is convenient and can be charged at any time without worrying about affecting the lifespan.
If the lithium battery is used in an environment higher than the specified operating temperature, that is, 35°C or higher, the battery's power will continue to decrease, that is, the battery's power supply time will not be as long as usual. If you have to charge the device 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, keeping the operating temperature as suitable as possible is a good way to extend the life of the lithium battery.
If you use the lithium battery in a low temperature environment, that is, below 4°C, you will also find that the battery life is reduced. 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, which is different from the use in a high-temperature environment. Once the temperature rises, the molecules in the battery will be heated, and they will immediately restore the previous power.
If you want to maximize the effectiveness of lithium-ion batteries, you need to use them frequently, so that the electrons in the lithium battery are always in a flowing state. If you don't use the lithium battery often, please remember to complete a charging cycle for the lithium battery every month and do a battery calibration, that is, deep discharge and deep charge once.
The formal name is "charge-discharge cycle", which is not equal to "number of recharges". Cycle refers to the battery from fully charged to depleted. This is a cycle. If your battery is fully charged, it takes one tenth It’s a tenth cycle, so it’s basically a cycle when it’s charged 10 times. Similarly, from full power, half used and then full, then half used and then full again, this is also a cycle, at this time you are charging twice. Therefore, the cycle only depends on "how much electricity is discharged from the battery", and has no direct relationship with the "number of recharges".
Moreover, this 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 battery’s ability to store power will drop to a certain level.
For example, for a lithium battery, the nominal charge-discharge cycle is "not less than 60% of the nominal capacity after 500 times"
That is, after 500 cycles, this battery can only store as much as 60% of the time when a new battery was stored. This means that the performance has dropped to a certain level.
Lithium batteries do not have a fixed limit on the number of recharges. 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. It can be used for 2 years once a day is charged. Usually, if the mobile phone battery is charged 1,000 times, the battery will be severely unusable.
Cell phone battery maintenance method:
1. It is fully charged each time to reduce the number of charging and increase the battery life.
2. There is no need to completely discharge the battery, usually when the battery is less than 10%, it needs to be charged.
3. Use the original charger to charge, do not use the universal charger.
4. Do not use the mobile phone during the charging process.
5. Don't overcharge, stop charging after the battery is full.
Yes, according to the experimental results, the lifespan of lithium batteries decays as the number of recharges increases. Generally, the number of recharges of lithium batteries is 2000-3000.
Cycle is use. We are using batteries. What we care about is the time of use. In order to measure the performance of how long a rechargeable battery can be used, the definition of the number of cycles is stipulated. The 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 in the national standard: under the condition of an 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 the end of life, and the number of cycles must be greater than 300.
Explanation of international standards:
A. This definition stipulates that the cycle life test is carried out in a deep charge and deep discharge method
B. According to this mode, the cycle life of the lithium battery is specified, and the capacity is still more than 60% after ≥300 cycles
However, the number of cycles obtained by different cycle systems is completely different. For example, the other conditions above remain unchanged, and only the constant voltage voltage of 4.2V is changed to the constant voltage 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 charging method, and the cycle life can be increased by nearly 60% in the final test. Then if the cut-off voltage is increased to 3.9V for testing, the number of cycles should be increased several times.
This is about the statement that one cycle of charging and discharging will lose one life. We should pay attention to the definition of the charging cycle of lithium batteries: a charging cycle refers to the full use of all the power of the lithium battery from full to empty, and then from empty to full charge. the process of. This is not the same as charging once. In addition, when you talk about the number of cycles, you cannot 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 of detecting battery life, not an end!
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