Introduce the charging and discharging characteristics of Li-ion battery

Through research, it is found that when x>0.5, the structure of Li1-xCoO2 is extremely unstable, the crystal form collapses, and its external appearance is the overwhelming end of the battery cell. Therefore, during use of the battery cell, the value of x in Li1-xCoO2 should be controlled by limiting the charging voltage. Generally, the charging voltage is not greater than 4.2V and x is less than 0.5. At this time, the crystal form of Li1-xCoO2 is still stable. The negative electrode C6 has its own characteristics. After the first formation, the Li in the positive electrode LiCoO2 is charged into the negative electrode C6. When discharging, Li returns to the positive electrode LiCoO2, but a part of Li must remain in the center of the negative electrode C6 after the formation. In order to ensure the normal insertion of Li in the next charge and discharge, otherwise the battery cell will be overwhelmed 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 discharge voltage: safe charging upper voltage ≤ 4.2V, lower discharge limit Voltage ≥2.5V. The principle of the memory effect is crystallization, and this reaction hardly occurs in lithium ion batteries. However, the capacity of a lithium-ion battery will still decrease after multiple charging and discharging, and the reasons are complex and diverse. The important thing is the change of the positive and negative materials themselves. From the molecular level, the lithium-containing hole structure 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 materials, and side reactions will generate stable others. Compound. Physically, the positive electrode material will gradually peel off. In short, the amount of lithium that can move freely in the battery during charging and discharging will eventually be reduced. Overcharge and overdischarge will cause permanent damage to the positive and negative electrodes of lithium ion batteries. From the molecular level, it can be intuitively understood that overdischarge will cause the negative electrode carbon to excessively release lithium and cause its sheet structure to collapse. Charging will hardly squeeze too much lithium into the carbon structure of the negative electrode, making some of the lithium unable to be released anymore. Unsuitable temperature will trigger other chemical reactions inside the lithium-ion battery to generate compounds that we do not want to see. Therefore, a protective temperature-controlled diaphragm or electrolyte additive is installed between the positive and negative electrodes of many lithium-ion batteries. When the battery heats up to a certain level, the membrane pores of the composite membrane are closed or the electrolyte is denatured, the internal resistance of the battery increases until it opens, and the battery no longer heats up to ensure that the battery charging temperature is normal. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: What are the disadvantages of all-solid-state batteries