Preparation method of modified high-nickel ternary positive electrode material

Abstract

The invention discloses a preparation method of a modified high-nickel ternary positive electrode material, which comprises the steps of uniformly mixing a nickel-cobalt-manganese hydroxide precursor with a lithium source and a magnesium source, and carrying out two-stage sintering to obtain a magnesium-doped ternary high-nickel positive electrode material; and dispersing the magnesium-doped ternary high-nickel positive electrode material in an organic solvent, then adding a vanadium source and a lithium source, uniformly stirring, heating, evaporating to dryness, drying, and sintering at high temperature to obtain the lithium vanadate-coated magnesium-doped high-nickel ternary positive electrode material. According to the modified high-nickel ternary positive electrode material disclosed by the invention, the cycle performance and the rate capability of the material can be synergistically improved due to the high-nickel ternary positive electrode material is subjected to double modification treatment of magnesium ion doping and fast ion conductor coating.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a preparation method of a modified high-nickel ternary positive electrode material. Background technique [0002] High nickel ternary cathode material Li(Ni x co y mn 1-x-y )O 2 (NCM) has the advantages of high specific capacity, good rate performance, and relatively low cost, and is considered to be one of the most promising cathode materials for power lithium-ion batteries. However, high-nickel ternary cathode materials have problems such as high surface activity, poor cycle performance, and unstable structure. Element doping and surface modification can improve the stability of high-nickel ternary cathode materials to a certain extent, and further improve Electrochemical properties of materials. [0003] Patent document CN103794753A discloses a lithium-ion battery composite cathode material and its preparation method. The method is to coat a layer of unifo...

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Problems solved by technology

However, this method is synthesized by a solid-state method, and the synthesized nickel-manganese oxide precursor is unevenly distributed, the particle size is different, and there is no obvious regular shape, which has a serious impact on the electrochemical performance of the later-synthesized positive electrode material.

And this method is to sinter the precursor with lithium and vanadium source at high temperature at the same time. However, the coating temperature of vanadium oxide and the sintering temperature of precursor with lithium cannot completely match, and the structure of the matrix material may be destroyed under the same sintering system. This sintering step is prone to deep diffusion of the material and cannot achieve uniform coating of the surface layer

In addition, this method uses PFG as a dispersant. During the high-temperature sintering process, PEG will form gas and discharge, which may form holes in the coating layer, making the formed coating layer loose and porous, and the electrolyte is easy to infiltrate during the cycle. , a side reaction occurs in contact with the positive electrode material, which affects the electrochemical performance of the material

[0005] CN112349905A discloses a method for co-coating lithium-ion battery anode materials with a nano-flaky fast ion conductor layer and an aluminum compound layer, and double-layer coating may make the coating layer too thick, which will reduce the power of lithium ion deintercalation Physical performance, thereby reducing the discharge specific capacity of the material

In addition, this method uses a solid-phase method to prepare the aluminum compound coating layer, which is not directly sintered into a lithium vanadate coating layer with a stable structure after coating, but continues to coat the aluminum outer layer with a solid-phase method. The coating process may also cause some damage to the structure of the dry nanosheet coating

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