Introduction to the charging and discharging characteristics of 502030 battery

Through research, it was found that when x is 0.5, the structure of Li1-xCoO2 is extremely unstable, and the crystal collapse will occur, which is manifested externally as the collapse of the battery cell. Therefore, the x value in Li1-xCoO2 should be controlled by limiting the charging voltage during the use of the battery cell. Generally, if the charging voltage is not greater than 4.2V, then x is less than 0.5, and the crystal form of Li1-xCoO2 is still stable.

The negative electrode C6 itself has its own characteristics. After the first formation, the Li in the positive electrode LiCoO2 is charged into the negative electrode C6, and when discharging, Li returns to the positive electrode LiCoO2. However, after the formation, a part of Li must remain in the center of the negative electrode C6 to ensure the normal embedding of Li in the next charge and discharge, otherwise the collapse of the battery cell is very short. In order to ensure that a part of Li remains in the negative electrode C6, it is generally achieved by limiting the lower limit voltage of discharge: the upper limit voltage of safe charging is ≤4.2V, and the lower limit voltage of discharge is ≥2.5V.

The principle of memory effect is crystallization, which almost never occurs in 502030 battery. However, the capacity of 502030 battery will still decrease after multiple charging and discharging, and the reasons are complex and varied. The most important thing is the change of the positive and negative electrode materials themselves. From a molecular level, the hole structure that accommodates lithium on the positive and negative electrodes will gradually collapse and block; from a chemical point of view, it is the active passivation of the positive and negative electrode materials, and side reactions will occur to generate other stable compounds. Physically, there will also be gradual peeling of the positive electrode material, which ultimately reduces the number of lithium that can move freely in the battery during charging and discharging.

Overcharging and over-discharging will cause permanent damage to the positive and negative electrodes of 502030 battery. From a molecular level, it can be intuitively understood that over-discharging will cause the negative electrode carbon to release excessive lithium and cause its sheet structure to collapse, and over-charging will force too much lithium into the negative electrode carbon structure, making some of the lithium no longer released.

Unsuitable temperature will trigger other chemical reactions inside the lithium-ion battery to generate compounds that we do not want to see, so a protective temperature-controlled diaphragm or electrolyte additive is installed between the positive and negative electrodes of many 502030 battery. When the battery temperature rises to a certain level, the pores of the composite membrane close or the electrolyte denatures, the internal resistance of the battery increases until it is short-circuited, and the battery no longer heats up, ensuring that the battery charging temperature is normal.

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