How to improve the high-rate performance of lithium-ion batteries?

Generally speaking, it is important to improve the rate performance of power lithium-ion batteries to start with the choice of materials. At a normal temperature of 20 ℃, the minimum electronic conductivity of LCO materials is only 5x10-8S/cm, while the electronic conductivity of NCM111 materials can reach 2.2x10- 6S/cm, with the further increase of nickel content, the electronic conductivity of the ternary material has also increased significantly. The electronic conductivity of the NCM8111 material has reached 4.1x10-3S/cm, and the ionic conductivity has also shown the same trend. , LCO material at 20 ℃, the ion conductivity is only 2.3x10-7S/cm, while the ion conductivity of NCM111 material is 3.2x10-6S/cm, NCM532 position 1.7x10-3S/cm, NCM622 position 3.4x10-3S/ cm, NCM811 material has reached 6.3x10-3S/cm. Therefore, ternary materials, especially high-nickel ternary materials or NCA materials, are more suitable for high-rate lithium-ion batteries from the perspective of electronic conductivity or ionic conductivity. Of course, in addition to these intrinsic characteristics of the material, its rate performance is also affected by multiple factors such as morphology. For example, the surface area of u200bu200bsmall particles is larger, and the diffusion distance of Li+ inside the particles is shorter, so theoretically it will have better Magnification performance. There are many types of anode materials to choose from. For example, graphite materials with small particles of mesophase have better performance in rate performance. Lithium titanate battery materials are often made into nanometers because of their low electrical conductivity. Therefore, the active area is further increased and the diffusion distance of Li+ is reduced. The lithium titanate battery therefore has very excellent rate performance and can realize fast charging. The new niobium-titanium-oxygen compound NTO anode material developed by Toshiba Corporation of Japan has a reversible capacity of 341mAh/g, which is much higher than that of LTO material and close to graphite material, but with the advantage of high-pressure compaction density, the volume energy density can reach It’s twice that of the graphite negative electrode, while the material also retains the characteristics of fast charging. ②Formulation optimization determines the rate performance of lithium-ion batteries. Another key to the battery’s formulation design. There are two forms of conduction in lithium-ion batteries, ion conduction and electronic conduction. Among them, ion conduction mainly includes Li+ in the electrolyte, the internal pores and activity of the electrode. Diffusion within the substance, electronic conduction is important for the conduction between active material particles. The high rate performance of lithium ion batteries is a comprehensive manifestation of several forms of conductivity. When the compaction density is too high, the electrode porosity will drop sharply, resulting in an increase in ion diffusion resistance, and when the compaction density is low, it will lead to contact resistance. Therefore, only a suitable compaction density can ensure the excellent rate performance of lithium-ion batteries while also taking into account the characteristics of high energy density. ③The choice of battery structure is also a very important issue on how to control the temperature of the rate battery during the discharge process. During the high current discharge process, the lithium ion battery will produce a lot of heat, and the accumulation of heat inside the lithium ion battery will cause the temperature As the temperature rises, a large temperature gradient appears, so the inconsistency of the internal degradation of the lithium-ion battery affects the life of the lithium-ion battery. How to choose a suitable structure becomes particularly important. ④Improve the ionic conductivity of the electrolyte. Lithium ions need to shuttle back and forth between the positive and negative electrodes, just like swimming in a swimming pool formed by the electrolyte and the battery case. The ionic conductivity of the electrolyte is the same as the resistance of water. Speed u200bu200bhas a very big impact. At present, the organic electrolytes used in lithium-ion batteries, whether liquid electrolytes or solid electrolytes, have low ionic conductivity. The resistance of the electrolyte has become an important part of the overall battery resistance, and its impact on the high-rate performance of lithium-ion batteries cannot be ignored. By selecting appropriate materials, formulas and structures, the internal impedance and polarization of the lithium-ion battery during high-rate discharge can be reduced, the temperature unevenness can be reduced, and the rate performance of the battery can be effectively improved. Improving the magnification performance is a comprehensive project. It must be considered from multiple factors. The author of Cunneng Electric is only a drop in the bucket. It is inevitable that there will be omissions due to limited knowledge. I hope that all friends will criticize and correct them and put forward their own opinions. ⑤Reducing the internal resistance of the battery Generally, a conductive agent is added to the positive electrode active material to reduce the contact resistance between the active material, the active material and the positive electrode matrix/current collector, and improve the electrical conductivity (ionic and electronic conductivity) of the positive electrode material. Improve magnification performance. Conductive agents of different materials and shapes will all have an impact on the internal resistance of the lithium-ion battery, thereby affecting its rate performance. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: What are the favorable factors for the development of the power lithium battery industry in recent years