What is the current status of cathode material?
The combination of a positive electrode material in which lithium ions are reversibly intercalated and deintercalated and a carbon negative electrode material can make the operating voltage of the lithium ion battery exceed 3.5V. This electrochemical reaction is carried out when the positive electrode pair Li/Li+ is 4V and the negative electrode pair Li/Li+ is approximately 0V. Because the energy of a battery depends on the product of its voltage and capacity, batteries with high energy density must be obtained from higher voltage and higher capacity materials. Therefore, when the same negative electrode material is used, the higher the capacity and potential of the positive electrode material, the higher the energy of the battery.
Because the positive and negative electrodes are put into a container of a certain size, the volume ratio capacity is more important than the mass ratio capacity. LiCoO2 has a volumetric specific capacity of 808mA·h/cm³, which is sufficient as a cathode material to meet the requirements, while nickel-based materials can provide a higher volumetric capacity of 870~970mA·h/cm³, but it needs to be doped with aluminum at the same time. To overcome its safety issues. SAFT company has adopted LiNi0.8Co0.15Al0.05O2 provided by Toda Kogyo company “formerly Fuji Chemical Industry Co., Ltd.) as the positive electrode material of lithium ion batteries for electric vehicles (EV), and similar compounds have also been applied in Japan. According to related reports, the specific capacity of this material is 20% higher than that of LiCoO2, and it is safer than LiCoO2 in terms of overcharging. The nickel-based cathode material battery has been used in Toyota Motors, and it has achieved no idling operation.
Although the performance of the spinel lithium manganate cathode material is worse than that of the layered compound, its price is reasonable and the earth is abundant, so it is very suitable for use as a cathode material in large-scale lithium-ion batteries. Batteries using this solid crystal structure compound have been used in mobile phones produced by NEC Corporation and EVs and HEVs produced by Nissan. However, the share of this material in the cathode material market is still relatively small. Since 2003, electric bicycles and electric power-assisted bicycles have been commercialized. The positive electrode materials for this type of application contain spinel manganese compounds. This trend may promote the large-scale acquisition of lithium-ion batteries using spinel compound positive electrode materials. application.
LiCoO2, the main cathode material of lithium-ion batteries, has been greatly improved in terms of rate performance and capacity. The improvement of the rate performance is mainly obtained by controlling the morphology of the particles, and the increase of the capacity is obtained by increasing the battery voltage, but at the same time, it is necessary to solve the corresponding safety issues.
The above is the status quo of cathode material.