Lithium batteries all have a lifespan of only two to three years. The life of lithium-ion batteries under the international harmonized standards is not expressed by time, but by the number of cycles. The average lithium-ion battery is between 500 and 800 times. In our daily life, we often hear the statement that lithium-ion batteries have a longer life than conventional batteries, with a cycle life of up to 500 cycles. So usually we will take this 500 times for granted that it is the number of charging times, but in fact this 500 times refers to the charging and discharging cycles.
A charging cycle, refers to the lithium-ion battery charge from full to empty, and then from empty to full process, which is not the same as a charge. For example, a lithium-ion battery is only half-used on one day, and then it is fully charged. If it does the same the next day, charging it when it’s half-used, for a total of two charges down the line, this only counts as one charging cycle, not two. Therefore, it may usually take several charges to complete one cycle instead of two.
Many people may wonder, is not the lithium-ion battery charge and discharge more than 500 cycles, it is necessary to replace the new lithium-ion battery? Many friends in order to be able to extend the life of the battery, each time when the battery is completely depleted before charging, this can really extend the life of lithium-ion batteries?
In fact, the battery capacity is relatively reduced a little bit for each completed charging cycle. However, this battery capacity reduction is very small and does not affect the normal performance of the battery. It is understood that nowadays, high-quality lithium-ion batteries after many cycles of charging and discharging, the battery capacity can still reach more than 80%. So many lithium-ion products can still continue to use after two to three years. Of course, the life of lithium-ion batteries after use is still to be replaced. The so-called 500 times, refers to the manufacturer in the stable depth of discharge (such as 80%) at the end of the number of times about 625 times the number of times the charging to reach 500 charging cycles (80% * 625 = 500) (ignoring factors such as lithium-ion battery capacity reduction). However, due to various influences in real life, especially the unstable depth of discharge during charging, the 500 charging cycles can only be used as a reference battery life.
In fact, the number of cycles obtained by different cycle systems is very different just change the 4.2V constant voltage to 4.1V constant voltage on the same type of battery cycle life test, so that the battery is not a deep charging method, the final test cycle life can be increased by nearly 60%. If the cut-off voltage is increased to 3.9V, the number of cycles should increase several times.
In addition, lithium-ion battery life varies depending on the type of battery. Specifically, there are the following two kinds:
1, soft pack lithium-ion battery life
(1) Soft-packed polymer lithium-ion battery theoretical life of 500 cycles or more, used in 3C products, life expectancy of 3 to 5 years;
(2) soft pack lithium iron phosphate battery theoretical service life of about 1500 cycles, small current charging and discharging, battery life of more than 10 years, high current discharge, life of about 5 years;
2, steel shell lithium-ion battery life
(1) Steel shell lithium ion battery theoretical life of 300 to 500 cycles, small current discharge, 2 to 3 years;
(2) Steel shell lithium iron phosphate battery theoretical life of about 1000 cycles, small current discharge, about 3 years;
People also often based on the rechargeable battery quality and lithium battery materials, clear lithium-ion battery life cycle times:
1. ternary material lithium-ion battery can cycle about 800 times.
2. lithium iron phosphate battery cycle system frequency is about 2500 times.
The rechargeable battery cycle system frequency and shoddy rechargeable batteries are different, shoddy rechargeable batteries are based on the rechargeable battery manufacturer’s instructions on the frequency of the cycle system design and production production and manufacturing, and shoddy rechargeable batteries are sometimes very likely not easy to appear in the side within 50 times the frequency of the cycle system.
The basic theoretical service life of lithium ternary batteries is about 800 cycles, which is moderate to high in the commercialized rechargeable lithium batteries. Lithium iron phosphate batteries have roughly 2,000 cycles, while lithium titanate can accomplish 10,000 cycle systems. Today’s popular producers of lithium batteries in their ternary core specifications in the service commitment to exceed 500 times, but lithium battery core in the formation of lithium battery packs, due to the consistency of the problem, it is very important that the operating voltage and internal resistance can not be exactly the same, the service life of the cycle system is about 400 times.
In general, the ternary lithium battery cycle system frequency in 500 ~ 1000 times up and down, assuming that the new energy vehicle in a detailed cycle system traveling 300km, that also represents 15 ~ 300,000km later, rechargeable batteries will run out of cycle system frequency.
There are many elements that jeopardize the cycle system life of lithium batteries, but one of the direct causes is the continuous decrease in the total number of lithium iron phosphate participating in kinetic energy transmission. It is important to emphasize that the total production of lithium in rechargeable batteries is not decreasing, but only the activity of less and less lithium iron phosphate, which is confined elsewhere or in the safe passage of the subject activity, and can not participate in the whole process of charging the battery of the circulatory system at will. Therefore, we only need to figure out the movement of this lithium iron phosphate should participate in the redox reaction reflection, we can figure out the principle of volume reduction, but also can purposefully take certain effective measures to slow down the development trend of lithium battery volume reduction, increase the service life of its circulatory system.
Users use lithium-ion batteries in a myriad of ways, because of the different conditions of use, lithium-ion batteries will end up with different actual service life.
The service life of lithium-ion batteries is generally 300 to 500 charge cycles. Assuming that the power provided by a complete discharge is 1Q, if we do not take into account the decline in power after each charging cycle, lithium-ion batteries can provide or replenish the power of 300Q-500Q during its life. So we understand that if we use 1/2 charge each time, we can charge 600-1000 times; if we use 1/3 power each time, we can charge 900-1500 times. As an analogy, if we charge randomly, the number of times is variable. Anyway, no matter how to charge, there is always 300Q to 500Q of power into this point is stable. Therefore, we can also understand that the life of a Li-ion battery is related to the total charge of the battery, not the amount of charge. There is no difference between deep discharge and shallow discharge on lithium life.
So shallow discharge and shallow charging are more favorable to lithium-ion batteries, and deep discharge and deep charging are only necessary if the lithium-ion batteries are done on time in the power module of the product. Therefore, do not get stuck in the process of using lithium power products, everything is convenient first, charge at any time, do not worry about the impact on life.
If a lithium-ion battery is used in a high temperature environment, such as temperatures above 35 degrees Celsius, the battery’s stored charge will continue to diminish, resulting in a battery that will not last as long as if it were operated in a normal temperature environment. Charging the battery at such high temperatures will damage the battery to a great extent, thus affecting the life of the battery. Even charging in a hot environment can cause varying degrees of damage to the battery, so you should try to prevent charging the battery in a hot environment. If the battery is charged at low temperatures, for example, below 4 degrees Celsius, the battery will also be damaged. You may find that the battery life is shortened at low temperatures, and some cell phones’ original lithium-ion batteries will even charge at low temperatures. But don’t worry too much, this is only a temporary situation, unlike when used at high temperatures, once the temperature rises, the molecules in the battery are heated up and the original charge is restored.
In order to fully utilize lithium-ion batteries, they usually have to keep the electrons flowing. If you don’t use lithium-ion batteries often, always remember to end the charging cycle of your lithium-ion batteries once a month by doing a power calibration, a deep charge.
Moisture is one of the reasons affecting the cycle times and life of lithium-ion batteries, too much water will have side reactions with the positive and negative active substances, destroying their structure and thus affecting the cycle, and at the same time too much water is not conducive to the formation of the SEI film, but at the same time when it is difficult to remove the trace water, the trace water can also ensure the performance of the electric cell to a certain extent.
Positive and negative compaction will also directly affect the lithium-ion battery cycle times and life, because the positive and negative compaction is too high, although it can improve the energy density of the battery cell, but it will also reduce the cycling performance of the material to a certain extent, from the theoretical analysis, the greater the compaction is equivalent to the greater the destruction of the structure of the material, which is to ensure that the lithium-ion battery can be recycled based on the structure; in addition, the positive and negative compaction of the higher battery cells It is difficult to ensure a higher liquid retention, and the liquid retention is the basis for the battery cell to complete a normal cycle or more cycles.
Objective conditions of testing, in the process of lithium-ion battery cycle times testing, the charging and discharging multiplier, cut-off voltage, charging cut-off current, overcharging and over-discharging in the test, the temperature of the test room, sudden interruption of the testing process, the contact between the test point and the core of the internal resistance of the external factors, will more or less affect the results of the cycling performance test, and in addition, the sensitivity of different materials to the above objective factors are different, unified testing standards and understand the commonalities and importance of the test. The standardization of test criteria and understanding of common and important material characteristics should be sufficient for daily work.
Negative electrode excess will affect the battery cycle times and life, the reason for negative electrode excess should be considered in addition to the impact of the first irreversible capacity and coating film density deviation, the impact on the cycling performance is also a consideration, on the lithium cobalt cobalt acid and graphite system, the negative electrode graphite becomes the “short board” side of the cycling process is more common, if the negative electrode excess is not enough, the battery cell may not be lithium precipitation before cycling, but after several hundred cycles, the structure of the positive electrode changes. However, after several hundred times of cycling, the positive electrode structure changes little, but the negative electrode structure is seriously damaged, and cannot fully receive the lithium ions supplied by the positive electrode, thus precipitating lithium, resulting in a premature decline in capacity.
Coating film density is also one of the factors, the battery house meeting to explore the single variable to consider the impact of film density on the cycle is almost an impossible task, film density inconsistency either bring capacity differences, or differences in the number of layers of winding or stacking of the core, for the same type of the same capacity of the same material of the core, reduce the density of the film is equivalent to adding a new layer or layers of winding or stacking of the number of layers, corresponding to the addition of the diaphragm can be Considering that the thinner film density can increase the multiplication performance of the cell, the baking and de-watering of the pole piece and bare cell will be easier, of course, it may be more difficult to control the error when coating with too thin film density, and the large particles in the active substance may also have a negative impact on the coating and rolling, and more layers means more foils and diaphragms, which in turn means higher cost and lower energy density, so it is also necessary to evaluate the difference in the number of layers. energy density, so the evaluation should also be a balanced consideration.
Material type, the choice of materials is the first element that affects the performance of lithium-ion batteries, the choice of materials with poor cycling performance, the process is more reasonable, made more perfect, the cycle of the battery cell is bound to be unable to guarantee; choose a better material, even if the subsequent made a little problem, cycling performance may not be too poor too far, from the point of view of the lithium-ion battery manufacturers in the selection of materials or formulations towards the point of view of an all-ion battery cycle performance is determined by the positive pole, the battery’s cycling performance is the result of the positive pole, the battery’s cycle performance is the result of the positive pole.
The cycling performance of the battery is determined by the cycling performance of the positive electrode after matching with the electrolyte and the cycling performance of the negative electrode after matching with the electrolyte, which is the worse of the two, the poorer cycling performance of the material, on the one hand, it may be that in the cycling process, the crystal structure changes too fast and thus can’t continue to complete the embedded lithium and delithium, on the one hand, it may be due to the active substance and the corresponding electrolyte can’t generate a dense and uniform SEI film.
On the other hand, it may be due to the inability of the active substance and the corresponding electrolyte to generate a dense and uniform SEI film, resulting in the premature side reaction between the active substance and the electrolyte and the electrolyte is consumed too quickly, thus affecting the cycle. In the design of the battery cell, if one pole is confirmed to choose a material with poor cycling performance, the other pole does not need to choose a material with good cycling performance to waste.
The amount of electrolyte is one of the most important reasons affecting the number of cycles and life of lithium-ion batteries, such as insufficient liquid injection that the performance of the impact is relatively large or even made out of the battery is not qualified, if the liquid injection is sufficient, but the aging time is not enough or the positive and negative electrodes due to the compaction of too many reasons caused by the immersion of liquid is not sufficient, with the cycle of the electrolyte inside the cell is consumed.
Positive and negative electrode, especially the negative electrode and electrolyte matching the microscopic performance of the formation of dense and stable SEI, and the right eye visible performance, both for the cycle process of electrolyte consumption rate, incomplete SEI film on the one hand, can not effectively prevent the negative electrode and the electrolyte side reaction and thus consume electrolyte, on the one hand, in the defective part of the SEI film will be with the cycle to regenerate the SEI film thus On the other hand, the defective parts of SEI film will regenerate SEI film as the cycle progresses, thus consuming reversible lithium source and electrolyte. Whether it is for a cell that has been cycled hundreds or even thousands of times or for a cell that has been jumped dozens of times, if the electrolyte is sufficient before cycling and has been consumed after cycling, it is likely that the new electrolyte retention will be able to improve the cycling performance to a certain extent.
How to extend the life of lithium-ion battery?
1. When using for the first time, it is best to fill the lithium-ion battery, important because lithium-ion batteries from the moment they leave the factory, they begin to be in a self-discharge process, self-discharge will make lithium-ion batteries with a reduced amount of electricity.
2. Note that lithium-ion batteries can not be over-discharged, over-discharge will cause irreversible loss of capacity. If the battery is not used for a long time, the battery should be taken out of the instrument and stored in a dry and cool place, and should be charged within 60~90 days, so as not to store for too long, the battery due to self-discharge caused by low power, resulting in irreversible capacity loss, because the best storage state of lithium-ion battery is half-electric storage.Since lithium-ion chemistry does not have a “memory”, you do not harm the battery pack with a partial discharge. If the voltage of a lithium-ion cell drops below a certain level, it’s ruined.
3. Never overcharge, and stop charging when the charging completion indicator is on.
4.Try to use the original lithium-ion battery charger charging, the original charger supporting strong performance, charging times moderate, to prevent damage to the internal structure of the battery due to excessive current charging.Using “fast chargers” is convenient but will degrade a lithium-ion battery more quickly than standard charging. For cellphones and laptops, lowering screen brightness, turning off location services and quitting high-power-use applications can help slow the discharge rate.
5.Lithium-ion batteries age. They only last two to three years, even if they are sitting on a shelf unused. So do not “avoid using” the battery with the thought that the battery pack will last five years. It won’t. Also, if you are buying a new battery pack, you want to make sure it really is new. If it has been sitting on a shelf in the store for a year, it won’t last very long. Manufacturing dates are important.
6.Avoid heat, which degrades the batteries.Avoid temperature extremes, both high and low, when using or storing lithium-ion batteries.
7.Avoid use or storage of lithium-ion batteries in high-moisture environments, and avoid mechanical damage such as puncturing.
8.Extending battery lifetime decreases costs and environmental burdens associated with the production of new batteries, including material consumption, mining impacts and greenhouse gas emissions as well as the disposal of used batteries.
In short, although the life of lithium-ion batteries is limited, we can relatively extend the life of lithium-ion batteries through the usual standardized use of lithium-ion batteries and regular maintenance!
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