Lithium supplement additive for lithium ion cathode material and preparation method thereof

Abstract

The invention discloses a lithium supplement additive for a lithium ion cathode material. The lithium supplement additive comprises a Li5FeO4 matrix and a coating layer positioned on the surface of the Li5FeO4 matrix, wherein the coating layer comprises a first coating layer carbon layer positioned on the surface of the Li5FeO4 matrix and a second coating layer transition metal oxide layer positioned on the surface of the first coating layer. The invention also discloses a preparation method of the lithium supplement additive, which comprises the following steps: preparing carbon layer coatediron oxide, carrying out wet mixing to prepare surface carbon coated Li5FeO4, mixing with a transition metal ion salt solution and an ammonium hydroxide solution, and carrying out high-temperature sintering to obtain the lithium supplement additive. According to the double-layer coated Li5FeO4 lithium supplementing additive disclosed by the invention, the Li5FeO4 matrix is micron-scale or nano-scale particles, and the particles are uniform and controllable, so that the migration path of electrons and ions is shortened, the lithium supplementing performance of the Li5FeO4 material can be exerted, and the service life of a lithium ion battery is prolonged.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a lithium-supplementing additive for a high-stability lithium-ion positive electrode material and a preparation method thereof. Background technique [0002] During the charging process of the lithium-ion battery in the first week, a solid electrolyte film (SEI film) will be formed on the surface of the negative electrode, which will consume the active lithium in the positive electrode, resulting in the first specific capacity loss (Initial Capacity Loss, ICL) of the lithium-ion battery. The irreversible capacity loss of graphite anode, which is the most widely used at present, can reach 10%, while for silicon-based and tin-based anodes with high specific capacity, the irreversible capacity loss is even as high as more than 30%, which greatly reduces the energy density of lithium-ion batteries. Therefore, the irreversible capacity loss of lithium-ion bat...

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Problems solved by technology

[0004] Patent No. CN108878849A mentions that an appropriate molar ratio of lithium source, iron source and organic carbon source are dissolved in water to form a gel, which is then spray-dried into a precursor powder, calcined at high temperature for a period of time under an inert gas atmosphere, and synthesized Li out of the core-shell structure 5 FeO 4 C; although in Li 5 FeO 4 Surface coating is used on the material, which can make Li 5 FeO 4 / C can effectively isolate water and carbon dioxide in the air, but due to the limitations of the preparation method, it is difficult to uniformly control the distribution of coating elements and coating thickness, especially the uneven coating makes the film layer fall off easily, and the coating effect is great discounted, it is difficult to effectively prevent water and carbon dioxide in the air from 5 FeO 4 material erosion

[0005] Patent No. CN109428067A mentioned in the patent of Li 5 FeO 4 The surface is double-coated with carbon and Mo 2 C, however, implements Mo 2 C coating, the carbon source is mainly sucrose, glucose, fructose, epoxy resin, etc., and the inert gas usually needs to be mixed with hydrogen to improve the Mo reduction effect, and the coating process is complicated; Mo 2 C as the main material coated Li 5 FeO 4 , can isolate the water in the air to Li 5 FeO 4 material erosion, but this kind of coating is still a combination of two substances, no solid solution is formed, and the effect of isolating erosion is limited; at the same time, the current synthesis of Mo 2 C needs to be carried out at a higher temperature, and its reaction needs to be at 700-900 ° C. When the reaction temperature is low, it will lead to incomplete carbonization

Higher synthesis temperature will inevitably lead to Mo 2 The sintering and agglomeration of C, when the temperature is low, will cause incomplete reaction, which will affect the coating effect to a certain extent; therefore, it is necessary to propose a controllable lithium supplement additive and its preparation method to prepare a smooth film , and the coated Li with uniform thickness and composition 5 FeO 4 Material

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