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As the range of new energy vehicles is limited, how to improve the endurance has affected the whole market. In the battery industry, ternary lithium battery with many advantages quickly occupied the 3C, automobile and other markets, and gradually replaced the traditional lead-acid battery. For the traditional battery, the ternary lithium battery has the advantages of long life, energy conservation, environmental protection and pollution-free, low maintenance cost, complete charging and discharging, light weight and so on. In some publicity materials, some people think that the ternary lithium battery has a long life, is that true? How many times does it have a life cycle? Let's uncover the truth.
In nature, lithium is the lightest metal with the lowest atomic mass. Its chemical properties are active. It is easy to lose electrons and be oxidized to Li +, the standard electrode potential is - 3.045v, and the electrochemical equivalent is 0.26g/ah. These characteristics of lithium determine that it is a material with high specific energy. Ternary lithium battery is a kind of lithium secondary battery which uses three kinds of transition metal oxides of nickel cobalt manganese as positive materials. It is a kind of lithium-ion rechargeable battery which has been widely studied and applied at present. It fully integrates the good cycle performance of lithium cobalt oxide, the high specific capacity of lithium nickel oxide, the high safety and low cost of lithium manganese oxide, and uses the methods of molecular level mixing, doping, coating and surface modification to synthesize the composite lithium-ion intercalation oxides.
The service life of ternary lithium battery is calculated by the proportion of capacity attenuation degree when it is used to a certain extent, and it ends directly when the capacity life is zero. The algorithm in the industry is to discharge the ternary lithium battery once after it is fully charged, which is called cycle life. In the process of use, irreversible chemical reactions inside the lithium battery will cause the battery capacity to decline, such as improper use, or extremely high or low temperature use. For example, the decomposition of electrolyte, the deactivation of active materials, and the collapse of positive and negative electrode structure lead to the decrease of the number of lithium ion embedding and deblocking. Experiments show that a higher rate of discharge will lead to a faster capacity attenuation. If the discharge current is low, the battery voltage will be close to the balance voltage, which can release more energy.
The theoretical life of the ternary lithium battery is 1200 times of complete charge and discharge, that is, the complete cycle life. According to the use frequency, one time of complete charge and discharge in three days, 120 times of complete charge and discharge in one year, the service life of the ternary lithium battery can reach ten years, even if there is loss in the use process or the number of days of charge and discharge is reduced, it can reach eight years. Note that the capacity life here is eight years later The capacity of ternary lithium battery will be more than 60%, which is the standard.
The theoretical life of ternary lithium battery is medium in commercial rechargeable lithium battery. Lithium iron phosphate is about 2000 times, while lithium titanate is said to be able to achieve 10000 cycles. At present, the mainstream battery manufacturers promise more than 500 times (charging and discharging under standard conditions) in their specifications of ternary cell, but after the cell is assembled into a battery pack, due to the consistency problem, the main reason is that the voltage and internal resistance cannot be exactly the same, and the cycle life is about 400 times. The manufacturer recommends 10% - 90% SOC service window. It is not recommended to conduct deep charging and discharging, otherwise it will cause irreversible damage to the positive and negative pole structure of the battery. If the calculation is based on shallow charging and shallow discharging, the cycle life will be at least 1000 times. In addition, if the lithium battery is often discharged in high rate and high temperature environment, the battery life will be greatly reduced to less than 200 times.