High-nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material and preparation method thereof

Abstract

The invention provides a high-nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material and a preparation method thereof. The positive electrode material is spherical particles with an average particle size of 5-8 microns, the nickel content of the positive electrode material gradually decreases from the center to the surface of the spherical particles, the manganesecontent gradually increases from the center to the surface of the spherical particles, the cobalt content is uniformly distributed in the spherical particles and the aluminum content is uniformly or gradiently distributed in the spherical particles. The preparation method comprises the steps: the solution I with low nickel content is continuously added into the solution II with high nickel content, then the solution II with gradually decreasing nickel content is continuously pumped into the ammonia aqueous solution to form a continuous reaction system with decreasing nickel content, and then the precursor with gradient change of nickel, cobalt, manganese and aluminum content is precipitated in an inert gas environment by taking hydroxide as the precipitant and ammonia water as the complexing agent; and then the nickel cobalt manganese aluminum hydroxide precursor is sintered with lithium so as to prepare the high-nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material. The quaternary positive electrode material obtained by the preparation method has high capacity, excellent cycle and rate performance and highly reversible charge-discharge reaction.

Description

technical field [0001] The invention relates to the field of positive electrode materials for lithium batteries, in particular to a high-nickel gradient nickel-cobalt-manganese-aluminum quaternary positive electrode material and a preparation method thereof. Background technique [0002] Li[Ni 1−x−y co x mn y ]O 2 (NCM) has become the most promising cathode material due to its high reversible capacity, long cycle life, and high operating voltage. In order to further improve the capacity of existing NCMs, the content of nickel is continuously increased, but excessive nickel enrichment will lead to a decrease in capacity retention and deterioration of thermal stability of the material. In order to eliminate the negative impact of high nickel, NCM is doped with metal ions to improve structural stability. Among various doping metals, aluminum is the most widely used dopant because it plays a role in stabilizing the crystal structure in the host layered structure. In additi...

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Problems solved by technology

This method does not clearly indicate the electrochemical performance of the positive electrode material before coating, and the improvement of the material by adding aluminum cannot be reflected after coating and modification with graphene, and the hydrothermal reaction conditions are relatively high, difficult to control, and the synthesis process is relatively complicated.

[0005] CN 108550822 A discloses a lanthanum, aluminum co-doped high-nickel ternary lithium battery positive electrode material, uniformly mixes nickel source, cobalt source, manganese source, lanthanum source and aluminum salt, and then adds precipitant and chelating agent to prepare NCM precursor Bulk slurry, lanthanum-doped high-nickel ternary cathode material Li by pre-firing and sintering 1.05-x Mg x Ni 1-2y-z co y mn y La z o 2 , although the present invention overcomes the shortcoming of poor cycle stability of traditional high-nickel ternary positive electrode materials, since the synthesis of the material occurs in the precursor co-precipitation step, this has a great influence on the growth process of the precursor, and the synthesis The condition control relationship of the process is complex

[0006] CN 106920934 A discloses a method for preparing cobalt-aluminum co-doped modified ternary precursor and positive electrode material based on high-nickel material, mixing nickel-cobalt-aluminum mixed solution, ammonia water and sodium hydroxide solution in a heating reaction kettle A coprecipitation reaction occurs to obtain a cobalt-aluminum co-doped modified ternary precursor precursor based on a high-nickel material. Since the material prepared by this method is dominated by lithium nickelate, it is inevitable that the nickel content is often higher than the lithium content. (Li 1-x Ni 1+x o 2 ), so divalent nickel will always appear in the lithium layer, resulting in a decrease in the lithium ion diffusion coefficient of the material

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