How many times is the life cycle of NCM lithium battery?

1. NCM lithium battery

What is a NCM lithium battery? In nature, lithium is the lightest metal with the smallest atomic mass. Its atomic weight is 6.94g/mol, and ρ=0.53g/cm3. Lithium is chemically active and easily loses electrons and is oxidized to Li+. Therefore, the standard electrode potential * is negative, -3.045V, and the electrochemical equivalent * is 0.26g/Ah. These characteristics of lithium determine that it is a kind of Materials with very high specific energy. NCM lithium battery refers to a lithium secondary battery that uses three transition metal oxides of nickel, cobalt and manganese as the positive electrode material. It fully integrates the good cycle performance of lithium cobalt oxide, the high specific capacity of lithium nickelate and the high safety and low cost of lithium manganate. It uses molecular level mixing, doping, coating and surface modification methods to synthesize nickel. Cobalt and manganese and other multi-element synergistic composite lithium intercalation oxides. It is a lithium-ion rechargeable battery that is widely researched and applied.

2. The life of a NCM lithium battery. The so-called life of a lithium battery means that the capacity of the battery decays to 70% of the nominal capacity (the capacity of the battery at room temperature 25°C, standard atmospheric pressure, and discharged at 0.2C) after a period of time, that is It can be considered the end of life. In the industry, the cycle life of a lithium battery is generally calculated based on the number of cycles when a lithium battery is fully charged. In the process of use, an irreversible electrochemical reaction occurs inside the lithium battery, which leads to a decrease in capacity, such as the decomposition of electrolyte, the deactivation of active materials, the collapse of the positive and negative electrode structure, and the decrease in the number of lithium ions intercalation and deintercalation, etc. . Experiments have shown that a higher rate of discharge will lead to a faster attenuation of capacity. If the discharge current is lower, the battery voltage will be close to the equilibrium voltage, which can release more energy.

3. The theoretical life of NCM lithium battery is about 800 cycles, which is medium among commercial rechargeable lithium batteries. Lithium iron phosphate battery is about 2,000 cycles, while lithium titanate battery is said to be able to reach 10,000 cycles. At present, mainstream battery manufacturers promise more than 500 times (charge and discharge under standard conditions) in the specifications of their NCM batteries. However, after the batteries are assembled into a battery pack, due to consistency problems, the main voltage and internal The resistance cannot be exactly the same, and its cycle life is about 400 times. The manufacturer recommends that the SOC use window is 10%~90%. Deep charging and discharging is not recommended, otherwise it will cause irreversible damage to the positive and negative structure of the battery. If it is calculated by shallow charge and shallow discharge, the cycle life will be at least 1000 times. In addition, if lithium batteries are frequently discharged in high-rate and high-temperature environments, the battery life will be drastically reduced to less than 200 times.

The number of life cycles of lithium batteries is determined according to the battery quality and battery materials:

1. The cycle times of NCM materials are about 800 times.

2. The cycle times of lithium iron phosphate battery are about 2500 times.

3. There is a difference between the cycle times of genuine batteries and defective batteries. Genuine batteries are designed and produced according to the cycle number in the battery manufacturer's specification, while the cycle times of defective batteries may sometimes be less than 50 times.

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