What are the effects of temperature changes on the charging and discharging of lithium batteries

　　Most people in the battery industry know that the stability of the charging and discharging state of lithium batteries is greatly influenced by temperature changes. When lithium batteries are charged and discharged in high and low temperature environments, their capacity retention rate decreases. Among all environmental factors, temperature has the greatest impact on the charging and discharging performance of lithium batteries, and the electrochemical reaction at the electrode/electrolyte interface is related to environmental temperature, The electrode/electrolyte interface is considered the heart of the battery. If the temperature drops, the reaction rate of the electrode also decreases. Assuming that the battery voltage remains constant and the discharge current decreases, the power output of the lithium battery will also decrease. If the temperature rises, the opposite is true, that is, the output power of the battery will increase, and the temperature will also affect the transmission speed of the electrolyte. If the temperature rises, it will accelerate, the transmission temperature will decrease, and the transmission will slow down. The charging and discharging performance of the battery will also be affected. But the temperature is too high, exceeding 45 ℃. Lithium ion batteries are increasingly being used in people's production and life, which makes their temperature environment a key concern. Relatively speaking, lithium batteries are more prone to safety issues in high temperature environments. Therefore, it is necessary to test the high-temperature performance of lithium batteries and compare them with their room temperature test data.

　　The change in temperature directly affects the discharge performance and capacity of lithium batteries. As the temperature decreases, the internal resistance of the battery increases, the electrochemical reaction rate slows down, the polarization internal resistance rapidly increases, the discharge capacity and discharge platform of the battery decrease, affecting the power and energy output of the battery. For lithium-ion batteries, the discharge capacity drops sharply at low temperatures, but at high temperatures, the discharge capacity is not lower than at room temperature and sometimes slightly higher than at room temperature. This is mainly due to the accelerated migration rate of lithium ions at high temperatures. Unlike nickel electrodes and hydrogen storage electrodes, lithium electrodes do not decompose or form hydrogen gas at high temperatures, causing a decrease in capacity. When the battery module is discharged at low temperature, as the discharge proceeds, heat is generated due to resistance and other reasons, causing the battery temperature to rise, resulting in an increase in voltage. As the discharge proceeds, the voltage gradually decreases.

　　At present, there is no clear theoretical support for the internal resistance, discharge platform, lifespan, capacity, and other necessary connections of the lithium battery industry at various temperature performance levels. Relevant calculation formulas and mathematical models are still in the exploratory stage. In practical experiments, it has been proven that lithium batteries are not sensitive to the temperature range of 0-40 ℃. If the temperature changes below 0 ℃ or above 40 ℃ during charging and discharging, the cycle life and capacity of lithium batteries will be lower than normal values. The larger the temperature range, the less capacity and life there will be. For example, in winter, especially in colder regions in the north, the battery life of mobile phones is much shorter than in summer. This is related to temperature changes, not the reason why mobile phone batteries are not durable.

　　The low-temperature performance of lithium batteries made of different materials also varies. For example, lithium iron phosphate has the worst low-temperature performance. The lithium iron phosphate battery developed byour Battery has a capacity of 89% of its maximum capacity at -10 ℃, which should be relatively high in the industry; At 55 ℃, the capacity can reach 95%, and the attenuation at relatively low temperatures is relatively small. However, the low-temperature performance of lithium manganese oxide, lithium cobalt oxide, and ternary products is better, but also limited; And the sacrifice is high-temperature performance. Nowadays, the industry advocates that lithium iron phosphate has high safety performance and good high-temperature performance, but in fact, the battery activity is not as high as the above three, which is relatively safer. The overall performance is still not as good as manganese lithium or ternary. In winter, especially in colder regions in the north, the battery life of mobile phones is much shorter than in summer.

　　Lithium ion batteries are increasingly widely used in people's production and life, which makes their temperature environment a key concern. Relatively speaking, lithium batteries are more prone to safety issues in high-temperature environments. Therefore, it is necessary to test the high-temperature performance of lithium batteries and compare them with their room temperature test data.

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