What is the reason for the decay of lithium battery capacity?

1. Lithium battery abuse. When the SOC of the lithium battery is below 120%, there is no obvious capacity loss; when the SOC is greater than 120%, the negative electrode begins to deposit lithium, and due to the formation of a thicker SEI film, the impedance becomes larger and causes the active lithium If you continue to overcharge, it will cause thermal runaway of the lithium battery. At an excessively high SOC, the decomposition rate of the electrolyte will become faster, and a thick deposition layer will be formed on the graphite negative electrode, and the lithium contained in the deposition layer will be precipitated. In addition, high-rate charging and discharging will also cause the loss of lithium battery capacity. This is because the volume of the positive and negative electrodes will shrink and expand during the charging and discharging process. The greater the charge and discharge current, the greater the contraction and expansion, and the greater the stress. Extreme particles are more likely to rupture or peel off from the current collector during rapid changes in volume, resulting in faster cycle decay. 2. The temperature factor must be mentioned is the use environment and conditions of the lithium battery damage its capacity. Temperature is definitely one of the key factors affecting the life of a lithium battery. Too high or too low temperature will cause the reduction of active lithium ion content, the destruction of electrode material structure, the dissolution of metal ions, and the serious capacity degradation. Conventional lithium battery operating temperature: -20℃~60℃, but generally below 0℃, the performance of the lithium battery will decrease, and the discharge capacity will be reduced accordingly. Therefore, the operating temperature for the full performance of the lithium battery is usually 0~40℃ . The temperature of lithium batteries required by some special environments is different, and some can even run normally in an environment of hundreds of degrees Celsius. Under low temperature conditions, the viscosity of the electrolyte increases, the ion conduction speed slows down, and the electron migration speed of the external circuit does not match, the battery appears severely polarized, and the charge and discharge capacity decreases sharply. Especially in the case of low-temperature charging, it may happen that Li+ migrated from the positive electrode is too late to be embedded in the carbon layer lattice of the negative electrode, forming lithium metal crystals at the negative electrode end, resulting in a decrease in battery capacity, and long-term low-temperature charging will cause lithium branches. The crystal pierces the diaphragm and causes a short circuit. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.