Composite sodium ion cathode material with core-shell structure and preparation method thereof

Abstract

The invention provides a composite sodium ion battery cathode material and a preparation method. The material has a shell-core structure, the inside of the material is a layered structure, and the surface of the material has a tunnel-like structure. The invention adopts a simple secondary sintering method, disperses the raw materials on the surface of the layered material through wet mixing or dry mixing, and generates a layer of tunnel-like structure with stable structure on the surface of the layered material in situ, and obtains a structure with a layer-tunnel A sodium ion composite cathode material with a core-shell structure. The composite sodium ion battery positive electrode material of the present invention has the advantages of high capacity of layered materials and good tunnel structure stability, can be stored stably in the air, and has better cycle stability and high-power performance than single layered materials or Tunnel-like structural material. Moreover, the preparation method is simple and the cost is low, which can effectively reduce the production and storage costs of the layered material, and has great commercial application prospects.

Description

technical field [0001] The invention relates to a battery cathode material and a preparation method, in particular to a sodium ion battery cathode material and a preparation method. Background technique [0002] Sodium, which has similar chemical properties to lithium, is abundant in the earth's crust and widely distributed, so sodium-ion batteries are considered to be the most promising secondary batteries to replace lithium-ion batteries in the field of large-scale energy storage. Currently layered transition metal oxides Na x TMO 2 (TM: one or more transition metal elements) is an important cathode material for sodium-ion batteries, which has attracted people's attention due to its high specific capacity, simple preparation method, and low price. However, layered cathode materials with two-dimensional sodium ion diffusion channels are sensitive to water and carbon dioxide in the air, and exposure to air will cause sodium ions to diffuse from the interlayer to the surfac...

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Problems solved by technology

However, layered cathode materials with two-dimensional sodium ion diffusion channels are sensitive to water and carbon dioxide in the air, and exposure to air will cause sodium ions to diffuse from the interlayer to the surface and react with water and carbon dioxide in the air to generate damage to the material. Sodium hydroxide and sodium carbonate with unfavorable electrochemical properties, at the same time, due to the loss of sodium ions, the structure of the layered material will be degraded, and the electrochemical performance will deteriorate; in addition, after the sodium ions are released during the charge and discharge process, the sodium interlayer spacing becomes larger, Part of the solvent molecules enter the layered material, resulting in a decrease in the structural stability of the material and poor cycle stability. These shortcomings have brought a lot of inconvenience to the production, transportation and storage of the layered sodium ion battery cathode material, limiting its use. Industrial application promotion

Another kind of positive electrode material is the positive electrode material of sodium ion battery with a tunnel-like structure. Although it has a three-dimensional sodium ion diffusion channel, its structure is stable, and it is not easy to react with water and oxygen in the air, but this structure is not conducive to the flow of solvent molecules into the material. Diffusion, therefore lower specific capacity

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