What effect does the overcharge of lithium batteries have on performance?

1) In the polarization phase, the voltage of the battery rises rapidly after the current is applied due to the existence of polarization, and the temperature of the battery decreases at this time;

2) After 240s, the battery enters the stage of stable temperature rise, in which the battery temperature rises at the rate of 0.05 ℃ /min;

3) During the temperature stabilization phase, the battery temperature will continue to rise, but the battery temperature will not rise.

Once the battery enters overcharge, the temperature of the battery first remains constant, then suddenly begins to rise, and finally reaches the peak temperature.

The declining trend of battery capacity during the overcharge cycle (2.75-5v) test of the lithium-ion battery at different cycle rates can be seen in the figure. The decline of battery capacity during the overcharge cycle at lower cycle rates is more serious. The decline rate of battery at 2C overcharge cycle is 0.12%/cycle, and the decline rate of battery capacity at 3C overcharge cycle is only 0.05%/cycle, The decline rate of 0.5c and 1C cycle batteries is much faster than that of 2C and 3C cycle batteries.

The temperature change of the T2 temperature sampling point of the battery at the 1st, 5th, 10th, and 15th cycles when overcharging cycles are carried out at different rates. It can be seen from the figure that the impact of the charging rate on the battery temperature is very obvious. The battery temperature rises faster when charging at large rates, and the temperature peak caused by overcharge is less obvious. At the same time, it can be noted from the figure below that the overcharge cycle also has a significant impact on the temperature characteristics of the battery. The peak temperature of the battery is significantly higher at the first overcharge, while the peak temperature of the battery becomes significantly milder in the subsequent overcharge cycle, indicating that the side effects caused by overcharge are more serious at the first overcharge.

The change of battery voltage curve during the overcharge cycle. From the figure, we can see that the overcharge cycle will have a significant impact on the battery charge and discharge voltage curve at low magnification. First, we can see that the battery voltage rises when charging begins, indicating that the battery polarization increases. There are three possible reasons:

One is the addition of battery internal resistance;

One is the reduction of battery active substances;