From the inside of lithium ions, the reasons for the battery aging are as follows. Lithium-ion numbers decrease due to the occurrence of side reactions. The active material in the electrode changes the battery's internal structure and active material quantity decreases due to the continuous cycling of the battery. And continuous internal resistance increases. Explain the causes of battery aging from a perspective outside of Li-ion. Factors such as high temperature, low temperature, long charging time and use time, and high current during charging are all reasons for the aging of lithium batteries.
During battery charging, when the charging current exceeds the range that itself can withstand, a gas evolution reaction occurs inside the battery. At the same time, a large amount of heat is generated, causing serious damage to the chemical materials inside the battery, which in turn leads to a shortened battery life. The maximum charging current value that the battery can withstand in different charging stages is also different. The impact of charging piles on the life of electric lithium batteries under different charging currents is shown in the figure.
The capacity of electric vehicle lithium batteries shows a certain downward trend with the increase of the charging rate of the charging pile. Especially after 300 charge-discharge cycles of the electric battery. When the electric vehicle is charged at a large rate, the battery capacity shows a downward trend. This result shows that a large charging current will have a certain impact on the capacity of the lithium battery.
During the charging process, the excessive temperature will accelerate the aging of the lithium battery. The maximum usable capacity Qmax of the battery is affected by factors such as the temperature and charging rate of the battery during operation and is a variable that cannot be directly measured. The influence of these factors must be considered when estimating. There is a nonlinear relationship between Qmax and the number of cycles of the battery and cell. As the number of cycles increases, the capacity will decrease significantly. Under different temperature conditions, the Qmax value is also different, showing a downward trend. But at the same time, with the continuous increase of the number of cycles, its value also showed a serious downward trend. It can be seen from the experimental results that the battery is in the optimal state when the temperature is 25°C.
