NCA ternary material Al element gradient doping technology has achieved a breakthrough?

　　NCA ternary material Al element gradient doping technology has achieved a breakthrough?

　　Among high-nickel materials, NCA has become a very potential cathode material for lithium-ion batteries due to its relatively high capacity (up to more than 190mAh/g) and good cycle life. It has been used in mobile electronic devices, electric Applications in automotive and other fields. However, the main production technology of high-performance NCA materials is currently in the hands of Japanese and Korean manufacturers. Domestic production technology is not yet very mature, and the stability of products needs to be continuously improved.

　　Although the content of Al element in the material is very low and it has no electrochemical activity, the Al element is of great significance to the cycle stability of the material. Therefore, the research on the doping technology of Al element is particularly important.

　　Since the conditions for synthesizing α-LiAlO2 and LiNiO2 are similar, and the two can also form a stable solid solution structure, this provides the possibility of gradient doping of Al element. Generally speaking, NCA materials need to first synthesize the precursor Ni1-x-yCoxAly(OH)2 using a co-precipitation method. However, Al element hydrolyzes poorly in a strong alkaline environment, which inhibits the growth of particles. Therefore, the higher the concentration of Al element in the solution, the worse the crystallinity of the precursor material. Therefore, it is particularly important to develop a method that can control the growth of precursors and the gradient distribution of Al elements.

　　JianguoDuan et al. from Central South University developed a new co-precipitation method that prevents the chaotic nucleation of Al3+ during the co-precipitation process and obtains a gradient Al-doped precursor material. The synthesis method is as follows: Ni and Co sulfates are first dissolved in deionized water according to the molar ratio to form a bimetallic ion solution. The concentration of the solution is 2mol/L. The preparation of [Al(OH)x]3-x solution is slightly more complicated. First, you need to dissolve the Al nitrate in distilled water, then slowly add 32% NaOH until a stable solution is formed, and then add deionized water. , the molar concentration of the solution is 1mol/L. The solution is the high [Al(OH)x]3-x concentration solution AS1, and the other low [Al(OH)x]3-x concentration solution is AS2. The AS2 solution The initial concentration is set to 0mol/L. The AS1 solution will be continuously pumped into the AS2 solution through the pump to gradually increase the concentration of the AS2 solution. The synthesis process is relatively simple. Put the AS2 solution and Ni-Co double ion solution in N2 At the same time, pump it into a stirring container containing NH3·H2O solution under the protection of Control it at around 11, the NH3·H2O solution concentration at 0.5mol/L, the reaction temperature at 60°C, and the stirring speed at 500r/min. During the synthesis process, the concentration of Al element gradually increases with time. After 48 hours of reaction, the precipitate was filtered, washed with deionized water, and vacuum dried at 120°C for 24 hours. The obtained precursor was mixed with LiOH and roasted at 550°C for 4 hours and 750°C for 12 hours under a continuous flow of oxygen to obtain Al gradient doped NCA material.

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