Core-shell structure high nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material and preparation method thereof

Abstract

The invention provides a core-shell structure high nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material and a preparation method thereof. The quaternary positive electrode material is spherical particles with an average particle size of 8-10 microns, the diameter of the inner core is 4-6 microns, the thickness of the shell layer is 2-3 microns and the surface ofthe shell layer is sheet-shaped. The nickel content gradually decreases from the center of the core to the surface of the shell structure, the manganese content gradually increases from the center ofthe core to the surface of the shell structure, the cobalt content is uniformly distributed and the aluminum content is uniformly or gradient distributed. The preparation method comprises the follow steps: a low nickel solution I is continuously added into a high nickel solution so that the nickel content in the high nickel solution is continuously reduced, and then the low nickel solution I is continuously pumped into an ammonia aqueous solution to form a continuous reaction system with reduced nickel content, and further hydroxide and carbonate are successively used as precipitants and ammonia water is used as a complexing agent to successively coprecipitate to generate a precursor with a core-shell structure; and then the precursor is sintered with lithium so as to prepare the core-shell structure high nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material. The battery assembled by the positive electrode prepared by the core-shell structure high nickel gradient nickel cobalt manganese aluminum quaternary positive electrode material has high capacity, excellent cycle and rate performance and highly reversible charge-discharge reaction.

Description

technical field [0001] The invention relates to a lithium battery cathode material and a preparation method thereof, in particular to a gradient nickel-cobalt-manganese-aluminum quaternary cathode material with a core-shell structure 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 nickel content is constantly increasing, but excessive nickel enrichment will lead to a decrease in the capacity retention and 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 addition, sinc...

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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.

[0004] 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 to generate The coprecipitation reaction obtains a kind of cobalt-aluminum co-doping modified ternary precursor precursor based on high-nickel material, because the material prepared by this method takes lithium nickelate as the leading material, and 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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