What are the requirements for cathode materials of lithium ion batteries
The performance of lithium ion battery cathode material directly affects the performance of lithium ion battery, and its cost also directly determines the battery cost. At present, the cathode materials successfully developed and applied include lithium cobalate, lithium iron phosphate, lithium manganate, ternary materials lithium nickel cobalt manganate (NCM) and lithium nickel cobalt aluminate (NCA).
This is the basic requirement for cathode materials of lithium ion batteries:
First, the potential of the material itself is high, so that a large potential difference can be formed between the material and the negative electrode material, resulting in a high energy density cell design; At the same time, the embedding and stripping of charged ions have little impact on the electrode potential, so there will be no excessive voltage fluctuation during the charging and discharging process, which will not bring adverse effects to other electrical devices in the system.
Second, the lithium content of the material is high, and the insertion and de insertion of the lithium ion battery are reversible. This is a prerequisite for high capacity. Some cathode materials have high theoretical capacity, but half of lithium ions lose their activity after being embedded for the first time. Such materials cannot be put into commercial use.
Third, the lithium ion diffusion coefficient is large, the lithium ion moves more quickly in the material, and the ability to embed and de embed is strong. It is the factor that affects the internal resistance of the electric core and the power characteristics.
Fourth, the material has a large specific surface area and a large number of lithium intercalation sites. With large surface area and relatively short intercalation channel of lithium ion, it is easier to embed and de embed. While the channel is shallow, the lithium insertion position should be sufficient.
Fifth, good compatibility and thermal stability with electrolyte are due to safety considerations.
Sixth, the materials are easy to obtain and have good processing performance. Low cost materials are easy to be processed into electrodes, and the electrode structure is stable, which is a favorable condition for the promotion and application of cathode materials of ion batteries.