Lithium battery cathode materials requirement

Battery cathode is one of the core component part of the battery,its advantages and disadvantages directly affect the battery performance. Generally speaking, cathode active substances are required as follows:

·Allow a large amount of Li+ embedding and ejecting (large capacity);

·High REDOX potential (high voltage);

·Good reversibility of embedding and ejection, small structural change (long cycle life);

·High lithium ion diffusion coefficient and electronic conductivity (low temperature, good multiplier characteristics);

·High chemical/thermal stability, good compatibility with electrolyte (good safety);

·Abundant resources, environment-friendly, cheap price (low cost, environmental protection).

Generally speaking, the key performance indexes of cathode electrode materials include chemical composition, crystal structure, particle size distribution, vibrational density, specific surface area, pH value, specific capacity of first discharge, efficiency of first charge and discharge, cycle life, etc.

Most of the cathode materials of the lithium battery is lithium oxide,generally the higher lithium content,the higher of the capacity.Like the Li content of the LMO is about 4.2%,and this value of LCO and LNO is about 7.1%.Lithium-manganese rich can be as high as about 10%.When material composition is fixed, the principal element content should be given in the form of actual test averages add tolerances to achieve the corresponding electrochemical activity and maintain stability between batches.

The size of cathode materials will directly affect the preparation of battery slurry and electrode sheet. Generally, the size of large-size materials has low viscosity, good fluidity, less solvent and high solid content.

The particle size of cathode electrode materials is usually measured by laser particle size analyzer.The equivalent diameter D50 of the largest particle when the cumulative distribution in the particle size distribution curve is 50% regard as average particle size.The particle size and distribution of positive electrode materials are closely related to the precursor, sintering and crushing process, and should be normally distributed under normal circumstances.Generally, lithium cobalt oxide and lithium carbonate are used as raw materials for the preparation of lithium cobalt oxide. Its sintering characteristics are very good, and it can be grown by controlling key factors such as Li/Co, sintering temperature and heating rate, so the requirements for raw materials are relatively low.Large abnormal-shaped particles are easy to appear in the powder materials grown and broken through sintering adhesion, and scratches and broken belts are easy to appear in the pulping coating and forming process. Therefore, the lithium cobalt oxide standard restricts the equivalent diameter Dmax of the largest particles in the particle size distribution curve.