Detailed explanation of lithium ion battery cathode materials

Cathode material is one of the key materials that determine the performance of lithium-ion batteries, and is also an important source of lithium in current commercial lithium-ion batteries. Its performance and valence have a greater impact on lithium-ion batteries. At present, the positive electrode materials successfully developed and applied mainly include lithium cobalt oxide, lithium iron phosphate, lithium manganate, ternary materials such as lithium nickel cobalt manganate (NCM) and lithium nickel cobalt aluminate (NCA). Lithium Cobalt Oxide (LCO): Suitable for small batteries, the actual capacity is not high. Lithium Cobalt Oxide is the first-generation commercial cathode material. It has been gradually modified and improved in decades of development and can be considered the most mature lithium ion. Battery cathode material. Lithium cobalt oxide has the advantages of high discharge platform, high specific capacity, good cycle performance, and simple synthesis process. However, the material contains more cobalt, and the cost is higher. Lithium cobalt oxide is still the best choice for small lithium-ion batteries. At present, most of 3C electronic batteries still use lithium cobalt oxide ions instead of ternary materials with higher specific capacity. The reason is that the compaction density of lithium cobalt oxide materials is greater than that of ternary materials, that is, the cobalt that can be contained in a unit volume. The amount of lithium ions is more. In small batteries that pay more attention to volume density, lithium cobalt oxide occupies a place. The theoretical capacity of lithium cobalt oxide is high, but the actual capacity is only half of the theoretical capacity. The reason is that lithium must be extracted from the lithium cobalt oxide ion material during the charging process, but when the amount of extraction is less than 50%, the morphology and crystal form of the material can remain stable. As the amount of lithium extracted increases to 50%, the lithium cobalt oxide material will undergo a phase change. If the charge continues at this time, the cobalt will dissolve in the electrolyte and oxygen will appear, which will seriously affect the cycle stability and safety performance of the battery. The general charging cut-off voltage of lithium cobalt oxide is 4.2V. Lithium Iron Phosphate (LFP): Low energy density and outstanding safety. Lithium iron phosphate is currently one of the most popular cathode materials. The theoretical specific capacity is 170mAh/g, and the actual specific capacity can reach more than 150mAh/g. Its important characteristics are low cost, very good safety, and high cycle life. These characteristics make lithium iron phosphate materials quickly become a research hotspot, and lithium iron phosphate batteries have also been widely used in the field of electric vehicles. The shortcomings of lithium iron phosphate are also more obvious, that is, low energy density. There are two reasons: one is that the voltage of lithium iron phosphate material is only about 3.3V, which is lower than other positive electrode materials, which makes the storage energy of lithium iron phosphate batteries lower; the other is that the conductivity of lithium iron phosphate is poor. Nanoization and coating can obtain good electrochemical performance, which makes the material fluffy and the compaction density is low. The combined use of the two makes the energy density of lithium iron phosphate batteries lower than that of lithium cobalt oxide and ternary batteries. Therefore, lithium iron phosphate batteries are mainly used in electric buses and a small number of passenger cars. Will iron phosphate be eliminated in the near future? Recently, new energy vehicle safety accidents have occurred frequently, and lithium iron phosphate ions, which are believed to be quickly replaced by ternary materials, have once again entered people’s field of vision. People hope to improve them by modifying lithium iron phosphate ions. Its capacity. At present, scholars have added Mn element to lithium iron phosphate to make it have higher voltage and higher energy density. There are also related studies that mix lithium iron phosphate with NCM ternary materials through composite technology to maintain The higher energy density of the three-element battery can effectively improve its safety performance. Ternary materials (NCM, NCA): performance can be adjusted, how to choose the road? Ternary materials are the common name of lithium ion nickel cobalt manganese oxide (LiNixCoyMn1-x-y02), which is very similar to the structure of lithium cobalt oxide. It can be balanced and regulated in terms of specific energy, circulation, safety and cost. The different configurations of the three elements of nickel, cobalt and manganese will bring different properties to the material: the increase in nickel content will increase the capacity of the material, but will make the cycle performance worse; the presence of cobalt can make the material structure more stable, but the content is too high. High will reduce the capacity; the presence of manganese can reduce costs and improve safety performance, but too high content will destroy the layered structure of the material, so finding the proportional relationship between the three materials to achieve the optimization of overall performance is a ternary material research and development the key of. Common ratios are NCM111, 523, 622, 811, etc. NCA (LiNio.8C0015Ah0502) replaces the manganese element with aluminum element, which improves the structural stability of the material to a certain extent, but its aluminum content is less, which can be approximately regarded as a binary material. 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: How to ensure the service life of lithium-ion large-capacity lithium-ion batteries?