What is the mechanism of the influence of the number of lithium battery discharge and charging cycles on the performance degradation of lithium batteries?
Publish Time: 2024-08-22
As a widely used energy storage device, the performance of lithium batteries will gradually decline with the increase of the number of discharge and charging cycles. Understanding this mechanism is crucial to improving the service life and reliability of lithium batteries.
During the discharge process, lithium ions are released from the positive electrode material and migrate to the negative electrode through the electrolyte, while electrons flow from the positive electrode to the negative electrode through the external circuit to provide power for the device. As the number of discharge cycles increases, the structure of the positive electrode material may gradually change. For example, some positive electrode materials may experience lattice distortion and particle rupture during long-term discharge, making it difficult for lithium ions to be embedded and extracted, thereby reducing the capacity and performance of the battery.
During the charging process, lithium ions migrate from the negative electrode back to the positive electrode, and electrons flow from the external power source into the positive electrode. Frequent charging cycles will cause a solid electrolyte interface (SEI) film to form on the surface of the negative electrode material. Although the SEI film can protect the negative electrode to a certain extent, as the number of cycles increases, the SEI film will continue to thicken and become uneven, which will increase the resistance of lithium ions passing through and reduce the charging and discharging efficiency of the battery. At the same time, the overpotential during the charging process may also lead to problems such as electrolyte decomposition and electrode material oxidation, further accelerating the decline of battery performance.
In addition, temperature changes during the discharge and charging cycle will also affect the performance of lithium batteries. High temperature will accelerate the aging of electrode materials and the decomposition of electrolytes, while low temperature will reduce the migration speed of lithium ions and affect the performance of batteries.
In short, the number of lithium battery discharge and charging cycles has a multi-faceted impact on performance degradation. The interaction of factors such as changes in the structure of positive electrode materials, thickening of negative electrode SEI films, and temperature changes has led to performance degradation phenomena such as decreased capacity, increased internal resistance, and reduced charging and discharging efficiency of lithium batteries. In order to extend the service life of lithium batteries, it is necessary to optimize the charging and discharging strategy, control the operating temperature, and continuously develop new electrode materials and electrolytes to improve the cycle stability and reliability of lithium batteries.
