The performance of cathode material of Li-ion battery directly affects the performance of Li-ion battery, and its cost also directly determines the cost of battery. At present, the main cathode materials successfully developed and applied are lithium cobaltate, lithium iron phosphate, lithium manganate, ternary materials lithium nickel-cobalt-manganate (NCM) and lithium nickel-cobalt-aluminate (NCA), etc.
Basic requirements for cathode materials of lithium ion battery:
First, the material itself has a high potential, so that a large potential difference can be formed between the material and the negative electrode, resulting in a high energy density cell design; At the same time, the impact of charged ions embedding and exiting on electrode potential is small, so there will not be too large voltage fluctuations in the charging and discharging process, and will not bring adverse effects to other electrical systems.
Secondly, the material contains high lithium content and the lithium ion battery is reversible. This is a high capacity premise. Some cathode materials, which have a very high theoretical capacity, have up to half of the lithium ions, which are deactivated after the first insertion. Such materials are not commercially viable.
Third, the diffusion coefficient of lithium ions is large, lithium ions move more rapidly inside the material, and the ability of embedding and deembedding is strong. It is a factor that affects the internal resistance of the cell and also the power characteristics.
Fourthly, the specific surface area of the material is large and there are a large number of lithium embedded sites. The large surface area and the relatively short embedding channel of lithium ion make it easier to embed and deembed. While the channel is shallow, the lithium insertion position should be sufficient.
Fifth, good compatibility and thermal stability with electrolyte, this is for safety considerations.
Sixth, the material is easy to obtain, and the processing property is good. Low cost, easy to be processed into electrodes and stable electrode structure are favorable conditions for the popularization and application of cathode materials for lithium-ion batteries.
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