Composite modification method for lithium ion battery positive electrode material

Abstract

The invention discloses a composite modification method for a positive electrode material. The method comprises the following steps: 1) removing impurities from a positive electrode material precursorto obtain a cleaned and impurity-removed positive electrode material precursor; 2) mixing the clean and impurity-removed positive electrode material precursor obtained in step 1) with a lithium source; 3) sintering the above obtained mixture to obtain a positive electrode material matrix; 4) dispersing and dissolving the source substance and the coating aid of a coating material in a solvent to obtain a dispersion system, adding the positive electrode material matrix obtained in step 3) to the dispersion system, performing stirring, then performing solid-liquid separation to obtain a coated solid substance, and finally performing heat treatment to obtain a material having a coating material layer; and 5) washing and drying the material obtained in step 4) to obtain a composite modified lithium ion battery positive electrode material. The high-nickel positive electrode material with a good stability is prepared through the method, and can be washed to effectively reduce residual alkaliwhile keeping the structure stable without causing deterioration of performances.

Description

technical field [0001] The invention relates to the field of lithium ion battery electrode materials (including positive electrode materials and negative electrode materials), in particular to a composite modification method for positive electrode materials, and in particular to a composite modification method for high-nickel positive electrode materials for lithium ion batteries. Background technique [0002] High-nickel-based layered oxide cathode materials have attracted extensive attention due to their advantages such as high specific capacity, low price, and good environmental friendliness, but their poor cycle stability, thermal stability, and storage performance. Air moisture is sensitive, resulting in high processing requirements and greatly limiting its application. Most of these shortcomings are the essential properties of high-nickel-based layered oxide cathode materials, which bring great challenges to overcome them. In recent years, researchers have tried a vari...

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Problems solved by technology

[0002] High-nickel-based layered oxide cathode materials have attracted extensive attention due to their advantages such as high specific capacity, low price, and good environmental friendliness, but their poor cycle stability, thermal stability, and storage performance. Air moisture is sensitive, resulting in high processing requirements and greatly limiting its application

Most of these shortcomings are the essential properties of high-nickel-based layered oxide cathode materials, which bring great challenges to overcome them. In recent years, researchers have tried a variety of methods to try to achieve both high specific capacity and high stability. , and the advantages of easy processing

[0003] At present, the investment in research and development of high nickel-based layered oxide cathode materials has been greatly enhanced, among which NCM811 or NCA is the most representative, and also includes other materials such as NC two-component. The common characteristics of this series of materials include: 1) High Ni content , generally greater than 0.6; 2) high capacity, generally above 180mAh / g; 3) poor stability, sensitive to air moisture, high lithium residue on the surface of fired products, and after contact with water and carbon dioxide, Surface residual alkali continues to rise

4) Severe side effects and poor safety

5) The structure of the material changes greatly during the charging and discharging process, and the cycle performance is poor

The ensuing problem is that the high-nickel material itself has poor structural stability. When it coexists with a strong polar solvent system, it is prone to Li-H exchange reaction, resulting in the loss of lithium. At the same time, there are transition metal elements Dissolution phenomenon

In literature reports and practical applications, it is generally used to adjust the water-material ratio and washing time, that is, to alleviate this problem by controlling the degree of erosion of the water system on the material. However, simply adjusting the water-material ratio and washing time cannot achieve good results.

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