Analysis of the safety performance of lithium battery materials

Lithium nickel cobalt manganese oxide (ternary) battery: The actual available theoretical specific energy has been greatly improved. As far as the lithium cobalt oxide battery is concerned, it can better play high-capacity applications, but from the point of view of materials, The ternary battery uses lithium nickel cobalt manganese oxide and organic electrolyte, and has not yet fundamentally dealt with the safety problem. If the battery is short-circuited, there will be excessive current, 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 the lithium cobalt oxide battery in the preparation is that after the overflow, there is still a large amount of lithium ions left in the positive electrode, that is to say, the negative electrode cannot accommodate more lithium ions attached to the positive electrode. 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 give the opportunity to pierce the diaphragm, and the puncture of the diaphragm will form an internal short circuit. Since the key 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 lithium-ion batteries. The material of lithium manganese oxide battery has certain advantages. It can ensure that the lithium ion of the positive electrode can be completely embedded in the carbon pores of the negative electrode in the fully charged state, instead of a certain residue in the positive electrode like lithium cobalt oxide. This fundamentally guards against the emergence of dendrites. In theory, this is the case. In fact, if lithium manganate batteries encounter strong external forces or cut corners during the preparation process, they may cause the battery to form lithium ions instantly during the charge and discharge cycle. mobile. Dendrites are formed when the negative electrode has no time to fully receive lithium ions. Beware of this consequence should be ensured from the detection of the battery when it leaves the factory. In short, the tested lithium manganate battery generally does not have safety accidents. The stable structure of lithium manganate makes its oxidation performance much lower than that of lithium cobalt oxide. Even if an external short circuit, it can basically be wary of combustion and explosion caused by the precipitation of lithium metal. 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 post: Analysis of the advantages and disadvantages of the square, cylindrical and soft packs of lithium iron batteries