R03 Carbon battery.Brief analysis of the preparation process of ternary material precursor for lithium batteries

　　After more than 20 years of development, lithium-ion batteries have made great progress in terms of reliability and battery performance. A variety of cathodes have also been developed during this process, such as lithium cobalt oxide, which has the longest history, as well as lithium iron phosphate, lithium manganate, etc. However, as the performance requirements for lithium-ion batteries have further improved, these materials can no longer meet the requirements, and ternary materials have been born.

　　Ternary materials mainly refer to nickel cobalt manganese lithium materials (NCM). Its biggest advantage is its high capacity. For example, the capacity of NCM811 material can reach about 220mAh/g, which is significantly better than lithium cobalt oxide (140mAh/g). Improvement, and NCM materials also have high-voltage potential and can be charged to 4.35V. At the same time, the addition of manganese also reduces the cost of the material. However, NCM materials (especially high-nickel 811, 532, etc.) generally have problems with synthesis difficulties and unstable cycle performance. This requires improvements in the synthesis process and roasting process. Today, the editor will take you to familiarize yourself with the preparation process of NCM precursor.

　　The electrochemical performance of NCM materials depends largely on the morphology of the precursor and the uniformity of particle distribution. The main method currently used in industry is the co-precipitation method. The main raw materials are cobalt sulfate, nickel sulfate, nickel sulfate and sodium bicarbonate. Make ammonium bicarbonate into a solution, dissolve manganese sulfate, cobalt sulfate, and nickel sulfate in deionized water at a mass ratio of 0.54:0.13:0.13, and slowly add the ammonium bicarbonate solution while stirring continuously. The pH value of ammonium bicarbonate solution is 7.78. At this pH value, Ni2+, Co2+, and Mn2+ will all generate carbonates, but no hydroxide and basic carbonate will be generated. The specific reaction equation is as follows:

　　Filter the precipitate obtained from the reaction and wash it with deionized water until no sulfate residue remains (use BaCl2 solution for detection until the filtrate no longer appears white precipitate). Put the obtained precipitate into a vacuum oven and dry it at 80°C. The precursor of ternary materials - ternary carbonate is obtained. In actual production, the conversion rate of sulfate is closely related to the concentration of reactants, the ratio between reactants and the temperature of the reaction.

　　When the concentration of ammonium bicarbonate gradually increases from low to high, the color of the solution changes from dark to light, to colorless, and then dark. The color of the solution represents the remaining metal ions in the solution. Therefore, there is an optimal value for the concentration of ammonium bicarbonate. Near this concentration, the metal ion precipitation effect is best. When the concentration is less than this concentration or greater than this concentration, metal ion precipitation will occur. Insufficient, resulting in waste and environmental pollution. Secondly, the concentration ratio of ternary metal salt and ammonium bicarbonate will also affect the precipitation effect of metal ions. After fixing the concentration of ammonium bicarbonate, adjust the amount of ammonium bicarbonate solution. It is found that with the addition of ammonium bicarbonate solution, the color of the solution gradually becomes lighter. When the ratio reaches 1:5, the solution is basically colorless. Calculate The conversion efficiency at this time is 91.2%. Increasing the amount of ammonium bicarbonate will have little effect on the conversion efficiency. For lithium-ion battery materials, the morphology also has a decisive influence on the electrical performance. In production, the precursor is generally required to be uniform spherical particles. In actual production, it was found that as the amount of ammonium bicarbonate increases, the spherical particle size of the precursor slightly decreases. increase, so the size of the precursor can be purposefully controlled according to requirements.

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