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KR-20260065116-A - positive electrode active material for sodium secondary battery, method for preparing the same and sodium secondary battery including the same

KR20260065116AKR 20260065116 AKR20260065116 AKR 20260065116AKR-20260065116-A

Abstract

One embodiment of the present invention provides a positive electrode active material for a sodium secondary battery, comprising: a composite particle; and a coating layer covering at least a portion of the surface of the composite particle; wherein the composite particle comprises at least one transition metal selected from nickel, iron, and manganese, sodium, and a doping metal, and the coating layer comprises an oxide of the doping metal and the coating transition metal.

Inventors

  • 김다모아
  • 이동욱
  • 박아람
  • 전예진

Assignees

  • 주식회사 에코프로비엠

Dates

Publication Date
20260508
Application Date
20241031

Claims (14)

  1. Composite particles; and a coating layer covering at least a portion of the surface of the composite particles; comprising, The above composite particles comprise at least one transition metal selected from nickel, iron, and manganese, sodium, and a doping metal, and The above coating layer comprises an oxide of the doping metal and the coating transition metal, a positive electrode active material for a sodium secondary battery.
  2. In paragraph 1, A positive electrode active material for a sodium secondary battery, wherein the oxides of the above-mentioned doping metal and coating transition metal are compounds represented by the following chemical formula 1: [Chemical Formula 1] (Ca 3-x ·A x )(Co 4-y ·B y )O 9 In the above chemical formula 1, A is Na, B is at least one transition metal element selected from Fe, Ni, and Mn, and 0≤x≤1, 0≤y≤1.
  3. In paragraph 1, The above coating layer further comprises an oxide (C2) of the coated transition metal and a carbonate (C3) of the doping metal, wherein The oxide (C1) of the above doping metal and coating transition metal has a monoclinic crystal structure of the P2 space group, and The oxide (C2) of the above-mentioned coating transition metal has a cubic crystal structure of the Fd-3m space group, and The carbonate (C3) of the above-mentioned doping metal is a positive electrode active material for a sodium secondary battery having a trigonal crystal structure of the 32/m space group.
  4. In paragraph 1, The above coating layer further comprises an oxide of the coated transition metal and a carbonate of the doping metal, wherein A positive electrode active material for a sodium secondary battery having a peak area ratio B/A of 0.7 to 1.3 according to X-ray diffraction analysis. (A above is the peak area of the oxide of the doping metal and coating transition metal located at 2θ=37.34±0.5° in X-ray diffraction analysis, and B above is the peak area of the oxide of the coating transition metal located at 2θ=36.82±0.5° in X-ray diffraction analysis)
  5. In paragraph 1, The above coating layer further comprises an oxide of the coated transition metal and a carbonate of the doping metal, wherein A positive electrode active material for a sodium secondary battery having a peak area ratio C/A of 0.5 to 1.0 according to X-ray diffraction analysis. (A above is the peak area of the oxide of the doping metal and coated transition metal located at 2θ=37.34±0.5° in X-ray diffraction analysis, and C above is the peak area of the carbonate of the doping metal located at 2θ=29.40±0.5° in X-ray diffraction analysis)
  6. In paragraph 1, The above doping metal is calcium and is substituted into the sodium layer of the above composite particle, and A positive electrode active material for a sodium secondary battery, wherein the above-mentioned coating transition metal is cobalt and does not substantially diffuse into the interior of the above-mentioned composite particle.
  7. In paragraph 1, The above-mentioned doping metal is, Provided to the entire body including the center of the above composite particle and to the coating layer, having a maximum concentration in the coating layer, A positive electrode active material for a sodium secondary battery having substantially the same concentration throughout, including the center of the above-mentioned composite particle.
  8. In paragraph 1, A positive electrode active material for a sodium secondary battery, wherein the doping metal is included in the coating layer at 10 to 30 weight% and in the composite particle at 70 to 90 weight% based on the total weight of the doping metal.
  9. In paragraph 1, The above coating layer is a positive electrode active material for a sodium secondary battery, having a thickness of 0.05 to 1.5 μm.
  10. In paragraph 1, A positive electrode active material for a sodium secondary battery, characterized in that the above composite particles are represented by the following chemical formula 2: [Chemical Formula 2] Na a-2x Ca x [(M y TM 1-y )]O 2 In the above chemical formula 2, TM is at least one selected from Ni, Mn, and Fe, and M is at least one selected from P, Sr, Ba, Ti, Zr, Al, W, Ce, Hf, Ta, Cr, F, Mg, Cr, V, Fe, Zn, Si, Y, Ga, Sn, Mo, Ge, Nd, B, Nb, Gd and Cu, and 0.80<a<1.20, 0.001≤x≤0.1, 0≤y≤0.1, 0.9≤1-y≤1.
  11. A step of preparing composite particles by mixing a precursor of the composite particles, a doping metal compound, and a sodium compound, and then heat-treating the mixture; and The method includes the step of forming a coating layer by mixing the above-manufactured composite particles with a coating transition metal compound and then heat-treating the mixture. A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein the coating layer comprises an oxide of the doping metal and the coating transition metal.
  12. In Paragraph 11, A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein, in the step of forming the coating layer, the heat treatment is performed at 300 to 500°C for 2 to 10 hours.
  13. A cathode for a sodium secondary battery comprising a cathode active material according to any one of claims 1 to 10.
  14. Sodium secondary battery using a positive electrode according to Paragraph 13.

Description

Positive electrode active material for sodium secondary battery, method for preparing the same and sodium secondary battery including the same The present invention relates to a positive electrode active material for a sodium secondary battery, a method for manufacturing the same, and a sodium secondary battery comprising the same. With the surging demand for lithium-ion rechargeable batteries, which are widely used as energy storage devices in various electronic technology fields, sodium-ion rechargeable batteries are attracting attention as a replacement for lithium, an expensive metal. Sodium-ion secondary batteries are one of the next-generation materials with high potential for application as secondary batteries because they have an insertion/extraction reaction operating principle similar to that of lithium-ion secondary batteries. However, they show lower performance in terms of capacity, lifespan, and rate characteristics compared to lithium-ion secondary batteries, making commercialization difficult. Therefore, the development of high-performance cathode active materials is required for commercialization. Layered transition metal oxides are typically used as cathode active materials for sodium-ion secondary batteries because they possess a simple structure, excellent electrochemical performance, and are easy to synthesize. Layered transition metal oxides are generally classified into O3-type and P2-type based on their crystal structure; cathode active materials based on the O3-type structure exhibit a composition such as Na x (TM) O2 (2/3 < x < 1.2), while cathode active materials based on the P2-type structure have a composition of Na x (TM) O2 (x ≤ 2/3). Although O3-type layered oxides possess higher energy density compared to P2-type layered oxide particles, they have disadvantages such as reduced cycle stability due to larger structural changes during the charge-discharge process, which makes commercial application difficult. Specifically, when O3-type layered oxide cathode active materials are used at high voltages, capacity and lifespan characteristics may deteriorate due to phase changes, and when used at low voltages, there is a problem of low capacity. To address the aforementioned problems, active research is being conducted on doping the cathode active material with inert metals or coating the surface of the active material particles with transition metals. Figure 1a shows the particle surface and cross-sectional SEM-EDS (Scanning electron microscope-energy dispersive x-ray spectroscopy) analysis results for the sodium composite transition metal oxide prepared in Example 1. Figure 1b is the result of X-ray diffraction (XRD) analysis of the sodium composite transition metal oxide prepared in Example 1, showing the peak intensity analysis originating from the (003) plane. Figures 2 and 3 are the results of SEM-EDS analysis of the surface of the cathode active material prepared in Examples 1 and 3. Figure 4 is the cross-sectional EDS Line scan Co analysis result of the positive electrode active material prepared in Example 1. The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Furthermore, the singular form includes the plural form unless specifically stated otherwise in the text. One embodiment of the present invention provides a positive electrode active material for a sodium secondary battery. The positive electrode active material comprises: a composite particle; and a coating layer covering at least a portion of the surface of the composite particle; wherein the composite particle comprises at least one transition metal selected from nickel, iron, and manganese, sodium, and a doping metal, and the coating layer comprises oxides of the doping metal and the coating transition metal. The above-mentioned coating transition metal may be a metal different from the transition metal of the above-mentioned composite particle. In the present invention, different coated transition metals are coated onto composite particles subst