Basic requirements for cathode materials in lithium-ion batteries:
First, the material itself has a high potential, which allows for a larger potential difference between it and the negative electrode material, resulting in a high-energy-density cell design. At the same time, the insertion and extraction of charged ions have little impact on the electrode potential, so the charging and discharging process will not have excessive voltage fluctuations and will not adversely affect other electrical components in the system.
Second, the material must have a high lithium content and the lithium-ion battery must have reversible insertion and extraction capabilities. This is a prerequisite for high capacity. Some cathode materials have a theoretically high capacity, but half of the lithium ions lose their activity after the first insertion. Such materials cannot be commercially viable.
Third, lithium-ion diffusion coefficient is large, allowing lithium ions to move more rapidly within the material and exhibiting strong insertion and extraction capabilities. This is a factor affecting the internal resistance of the battery cell and also influences its power characteristics.
Fourth, the material has a large specific surface area, providing numerous lithium insertion sites. A large surface area means relatively short lithium-ion insertion channels, making insertion and extraction easier. In addition to shallow channels, there must be sufficient lithium insertion sites.
Fifth, it has good compatibility with electrolytes and good thermal stability, which is for safety reasons.
Sixth, the materials are readily available and have good processing performance. Low cost, easy processing of the materials into electrodes, and stable electrode structure are favorable conditions for the widespread application of lithium-ion battery cathode materials.
