7.png     The so-called lithium battery life refers to the end of the life after the battery has been used for a period of time, and the capacity at which the battery attenuates to 70% of the nominal capacity (room temperature 25℃, standard atmospheric pressure, and discharged at 0.2C). In the industry, the cycle life is generally calculated based on the number of cycles when the lithium battery is fully charged. During use, irreversible electrochemical reactions will occur inside the lithium battery, resulting in a decrease in capacity, such as the decomposition of the electrolyte, the inactivation of the active material, the collapse of the positive and negative electrode structure, resulting in a decrease in the number of lithium ions embedded and deintercalation, etc. Experiments show that higher magnification discharge will cause faster attenuation of capacity. If the discharge current is low, the battery voltage will approach the equilibrium voltage and can release more energy. The theoretical life of ternary lithium batteries is about 800 cycles, which is medium among commercial rechargeable lithium batteries. Lithium iron phosphate is about 2,000 times, while lithium titanate is said to reach 10,000 cycles. Currently, mainstream battery manufacturers promise to exceed 500 times in the specifications of the ternary battery cell they produce (charge and discharge under standard conditions). However, after the battery cell is equipped with a battery pack, due to consistency, the voltage and internal resistance cannot be exactly the same, and its cycle life is about 400 times. The manufacturer recommends that the SOC usage window is 10%~90%. It is not recommended to perform deep charging and discharging, otherwise it will cause irreversible damage to the positive and negative electrode structure of the battery. If calculated based on shallow charging and discharging, the cycle life will be at least 1,000 times. In addition, if lithium batteries are often discharged under high-speed and high-temperature environments, the battery life will drop significantly to less than 200 times.

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