How to avoid the safety issues of large-capacity lithium iron phosphate battery packs?

How to solve the safety problem of large-capacity lithium iron phosphate battery pack? Lithium battery packs need to solve the safety problem from the fundamental principle and technology. In the past, most people considered improving the safety of batteries from the technological perspective, such as designing safety valves, avoiding short circuits, and controlling the manufacturing process, but these tasks can only be said to minimize safety accidents, and it is impossible to completely avoid accidents. Safety can be improved by optimizing the structure and design of lithium iron phosphate batteries. For example, select positive electrode materials with high thermal stability, flame-resistant electrolyte, negative electrode materials that do not precipitate lithium, and high-performance separators. Choose safe cathode materials. Currently, there are two mass-produced material products of lithium cobalt oxide and lithium manganese oxide. Lithium cobalt oxide is a very mature system in terms of small batteries. Due to the characteristics of lithium cobalt oxide (LiCo) in terms of molecular structure: after fully charged, there are still a large amount of lithium ions left in the positive electrode, and when overcharged, it remains in the positive electrode. Lithium ions will rush to the negative electrode, and the formation of dendrites on the negative electrode is an inevitable result of the overcharge of the battery using lithium cobalt oxide material. Even in the normal charging and discharging process, there may be excess lithium ions free to form on the negative electrode. Dendrite. The choice of lithium manganate material ensures that in the fully charged state, the lithium ions of the positive electrode have been completely embedded in the carbon pores of the negative electrode in terms of molecular structure, which fundamentally avoids the generation of dendrites. At the same time, the stable structure of lithium manganese oxide makes its oxidation performance far lower than that of lithium cobalt oxide, and its decomposition temperature exceeds 100 degrees of lithium cobalt oxide. Avoid the danger of burning and explosion due to the precipitation of metallic lithium. The safety of lithium batteries is greatly improved in terms of the actual available theoretical specific energy compared with lithium cobalt manganese oxide ternary batteries. Compared with lithium cobalt oxide batteries, it can play a better role in high capacity, but from the material From the above point of view, the ternary battery uses lithium nickel cobalt manganese oxide and organic electrolyte, which has not yet fundamentally solved the safety problem. If the battery is short-circuited, excessive current will be generated, which will cause safety hazards. The theoretical capacity of the lithium iron phosphate battery is 170mAh/g, and the actual reachable capacity of the material is 160mAh/g. In terms of safety, lithium iron phosphate has high thermal stability, low electrolyte oxidation capacity, and therefore high safety; but the disadvantages are low conductivity, large volume, large electrolyte consumption, and poor battery consistency due to large capacity. The most important feature of lithium cobalt oxide batteries in preparation is that after fully charged, there are still a large amount of lithium ions left in the positive electrode, that is, the negative electrode cannot accommodate more lithium ions attached to the positive electrode, but the In the charged state, the excess lithium ions on the positive electrode will still swim to the negative electrode, because it cannot be fully contained and turned back to form metallic lithium on the negative electrode. Because metallic lithium is a dendritic crystal, it is called a dendrite. Once a dendrite is formed , It will provide an opportunity to pierce the diaphragm, and the puncture of the diaphragm will form an internal short circuit. Since the main component of the electrolyte is carbonate, the flash point and boiling point are low, and it will burn or even explode at higher temperatures. It is easier to control the formation of lithium dendrites on small-capacity lithium batteries. Therefore, lithium cobalt oxide batteries are currently limited to small-capacity batteries such as portable electronic devices and cannot be used for power batteries. Disclaimer: Some pictures and content of articles published on this site are from the Internet, please contact to delete if there is any infringement. Previous: Large-capacity solid-state power lithium-ion battery leads the industrial revolution