Analysis of the causes of the capacity degradation of lithium batteries

What is the reason for the capacity degradation of lithium batteries? 1. Misuse of lithium batteries When the charging share of lithium batteries is less than 120%, there is no significant capacity loss. When the charge share of the lithium battery is greater than 120%, lithium deposition appears at the beginning of the negative electrode. Due to the formation of a thick SEI film, the impedance increases, resulting in the loss of active lithium. If the overcharge continues, it will cause heat loss of the lithium battery. When the charging rate of the lithium battery is too high, the differentiation rate of the electrolyte will be faster, and the thicker deposited layer formed by the negative electrode graphite contains lithium deposits. In addition, a large proportion will also cause the loss of charging and discharging capacity of lithium batteries. This is because the negative volume will attack shortening and swelling during the process of charging and discharging. The greater the charging and discharging current, the more intense the shortening and the greater the pressure. As the particles of the cathode are more likely to attack the rapidly changing volume to break or collect from a fluid, the cycle decays faster. 2. The temperature coefficient should point out that the working environment and conditions of the lithium battery damage its capacity. Temperature is definitely one of the key factors affecting the life of lithium batteries. Too high or too low temperature will cause the active lithium ion content to decrease, destroy the electrode data structure, dissolve metal ions, and cause serious capacity degradation. The working temperature of conventional lithium battery: -20℃~60℃, but generally below 0℃, the function of the lithium battery will decrease, and the discharge will also decrease, so the working temperature of the complete function of the lithium battery is generally 0~40℃ . Some special environments require different temperatures for lithium batteries, and some can even operate in an environment of several hundred degrees Celsius. At low temperatures, the viscosity of the electrolyte increases, the ion conduction speed slows down, the electron removal speed of the external circuit does not match, the battery polarization is serious, and the charge and discharge capacity drops sharply. In particular, when charging at low temperatures, Li + from the anode will not be able to be inserted into the carbon layer lattice of the negative electrode, forming a metal lithium crystal at the negative end, resulting in a decrease in battery capacity.Charging at low temperature for a long time will cause lithium dendrites to pierce the separator. Cause a short circuit. Important factors affecting the capacity degradation of lithium batteries are structural damage or deactivation of positive and negative data, differentiation of electrolyte, and misuse of lithium batteries. The charging and discharging process of the battery is a chaotic electrochemical process, and the factor that causes the battery capacity to decline is not a single factor. One aspect of the deterioration may cause other factors to affect the battery capacity, cycle function, energy density, etc. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: What are the advantages of using lithium batteries in medical equipment?