The positive electrode material of lithium ion battery is usually composed of lithium active compound, and the negative electrode is carbon with special molecular structure. The most important component of common positive electrode material is LiCoO2. When charging, the electric potential at the two poles of the electrode forces the compound of the positive electrode to release lithium ions and intercalate The negative electrode molecules are arranged in a sheet structure of carbon, and lithium ions are precipitated from the sheet structure of carbon during discharge, and recombine with the positive electrode compound, and the movement of lithium ions causes a current.

Factors affecting cathode materials for lithium-ion batteries

1. Crystallinity

If the crystal structure is well developed, the crystallinity will be high, which is conducive to the diffusion of Li+, and the electrochemical performance of the material will be good; otherwise, the electrochemical performance will be poor.

2. Synthesis time and synthesis temperature

The synthesis time affects the degree of crystallinity development and reaction. The synthesis time is short, the reaction is incomplete, the crystallinity is not well developed, and there are impurity phases; if the time is too long, the prepared crystal structure may change greatly.

The synthesis temperature affects the performance, structure and degree of reaction of the material. Although low-temperature synthesis can obtain smaller particles and large specific surface area, but at the same time, the reaction time is too long, the crystallization performance is poor, the reaction is incomplete, the impurity phase is large, and the electrochemical performance of the material is not good; the high-temperature synthesis reaction time is short, and the crystallization performance is better. The reaction is complete, but the particle size of the material is large, the specific surface area is small, and the electrochemical performance of the material is poor.

3. Granularity

The particle size affects the specific surface area of the material. The particle size is too large, the specific surface area is small, and the adsorption of the particles is relatively poor. The positive electrode active material may be separated from the matrix and free in the electrolyte. Once in contact with the negative electrode material, it will cause a local battery short circuit.

If the particle size is too small, the specific surface area is too large, the powder is very easy to agglomerate, it is difficult to disperse in the organic solvent, the active material of the electrode sheet is unevenly distributed, and the battery performance does not decrease; at the same time, the particle size is too fine, which easily causes surface defects and induces battery electrodes. To reduce the electrochemical energy of the positive electrode.

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