Nickel-cobalt-manganese ternary positive electrode material precursor with double-gradient structure, preparation method thereof and ternary positive electrode material

Abstract

The invention discloses a preparation method of a nickel-cobalt-manganese ternary positive electrode material precursor with a double-gradient structure. The preparation method comprises the following steps: (1) preparing a solution S1, a solution S2 and a solution S3 which are different in nickel content and contain nickel, cobalt and manganese; (2) continuously adding the solution S2 into the solution S3, then adding into a reaction kettle, and continuously stirring for coprecipitation reaction until the solution S2 is completely consumed; (3) replacing the solution S2 with the solution S1, and continuing the step (2) to obtain a solution containing a precursor material; and (4) aging, filtering, washing and drying the solution containing the precursor material to obtain the precursor. The invention also provides a nickel-cobalt-manganese ternary positive electrode material precursor with the double-gradient structure and a ternary positive electrode material. The nickel-cobalt-manganese ternary positive electrode material precursor with the double-gradient structure is favorable for keeping the structural stability of the material in the charge-discharge cycle process, and shows excellent electrochemical properties such as cycle, rate, capacity retention ratio and coulombic efficiency.

Description

technical field [0001] The invention belongs to the field of battery materials, and in particular relates to a precursor material, a preparation method thereof, and a ternary positive electrode material. Background technique [0002] As one of the four core materials of the battery, the cathode material restricts the overall performance of the battery. The cathode material can inherit the morphology and structural characteristics of the precursor, so the structure and preparation process of the precursor have a crucial impact on the performance of the cathode material. The ternary precursor material, as the raw material of the cathode material, determines the performance of the final material. At present, the improvement direction of the structure design of the ternary precursor material mainly includes the quasi-single crystal structure, radial structure, core-shell structure and gradient structure. Especially in the improvement of core-shell structure and gradient structu...

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Problems solved by technology

Although this method improves the design of the ternary precursor in terms of structure, there is a sudden change in the interface between the hydroxide layer and the carbonate layer, the interface stability is not good, and voids will be generated after a long period of charging and discharging; The shell layer is easy to form a porous structure, and the compactness is poor. After a long cycle, the shell layer of the prepared positive electrode material is unstable, easy to fall off from the core layer, and the cycle performance is not good; and, when the composition and structure of the core material and shell material When the difference is large, the inner core gradually loses the channel for lithium ion migration, resulting in a sharp decrease in the specific capacity of the material

In addition, the patent fails to achieve precise control over the distribution of nickel content in the core-shell structure, the internal nickel content drops too fast and the surface nickel content is still relatively high, which may have defects such as low capacity, unstable surface structure, and poor thermal stability. thus affecting the electrochemical performance

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