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KR-20260065024-A - positive electrode active material for sodium secondary battery, method for preparing the same and sodium secondary battery including the same

KR20260065024AKR 20260065024 AKR20260065024 AKR 20260065024AKR-20260065024-A

Abstract

One embodiment of the present invention provides a positive electrode active material for a sodium secondary battery comprising at least sodium, nickel, manganese, M1, and a doping metal, wherein M1 is iron or cobalt, and the doping metal is composed of calcium and copper, satisfying Equation 1A.

Inventors

  • 전예진
  • 박아람
  • 이명주
  • 이동욱

Assignees

  • 주식회사 에코프로비엠

Dates

Publication Date
20260508
Application Date
20241031

Claims (16)

  1. It comprises a sodium complex transition metal oxide comprising at least sodium, nickel, manganese, M1, and a doping metal, and The above M1 is iron or cobalt, and The above doping metal is composed of calcium and copper, and is a positive electrode active material for a sodium secondary battery satisfying the following relationship 1A: [Relation 1A] 80 ≤ A1(Cu)/At (%) ≤ 99 In the above relationship 1A, At is the total cross-sectional area of the above sodium composite transition metal oxide particles, and A1(Cu) is the area of the region in which copper is within ±10% of the average content (Cu, average at mol%) for 100 at mol% of all metals excluding sodium and calcium among the total cross-sectional area above.
  2. In paragraph 1, A positive electrode active material for a sodium secondary battery satisfying the following relationship 1B: [Relationship 1B] 80 ≤ B1(Cu)/Bt (%) ≤ 99 In the above relationship 1B, Bt is the total surface area of the sodium complex transition metal oxide particles, and B1(Cu) is the area of the region in which copper is within ±10% of the average content (Cu, average at mol%) for 100 at mol% of all metals excluding sodium and calcium among the total surface area above.
  3. In paragraph 1, A positive electrode active material for a sodium secondary battery satisfying the following relationship 2A: [Relationship 2A] 80 ≤ A2(Ca)/At (%) ≤ 99 In the above relationship 2A, At is the total cross-sectional area of the above sodium composite transition metal oxide particles, and A2(Ca) is the area of the region in which, among the total cross-sectional area, the calcium content is within ±10% of the average content (Ca, average at mol%) for a total of 100 at mol% of sodium and calcium.
  4. In paragraph 1, A positive electrode active material for a sodium secondary battery satisfying the following relationship 2B: [Relationship 2B] 80 ≤ B2(Ca)/Bt (%) ≤ 99 In the above relationship 2B, Bt is the total surface area of the sodium complex transition metal oxide particles, and B2(Ca) is the area of the region in which, among the total surface area, calcium is within ±10% of the average content (Ca, average at mol%) for a total of 100 at mol% of sodium and calcium.
  5. In paragraph 1, The above sodium composite transition metal oxide is a positive electrode active material for a sodium secondary battery comprising the doping metal such that the molar ratio of copper to calcium (Cu/Ca) is 1.5 to 4.5.
  6. In paragraph 1, The above sodium complex transition metal oxide contains copper in an amount greater than 3 at mol% and less than 10 at mol% with respect to 100 at mol% of total metals excluding sodium and calcium, and A positive electrode active material for a sodium secondary battery containing more than 0.5 at mol% and less than 3 at mol% of calcium, based on a total of 100 at mol% of sodium and calcium.
  7. In paragraph 1, The above sodium complex transition metal oxide is a positive electrode active material for a sodium secondary battery comprising a compound represented by Chemical Formula 1-1: [Chemical Formula 1-1] Na a-2v Ca v [(Ni x Mn y M1 z Cu w )]O 2 In the above chemical formula 1-1, M1 is Co or Fe, and 0.8<a<1.2, 0.005<v<0.03, 0.1≤x≤0.9, 0.1≤y≤0.9, 0.1≤z≤0.9, 0.03<w<0.1, x+y+z+w=1.
  8. In paragraph 1, The above sodium complex transition metal oxide is a positive electrode active material for a sodium secondary battery comprising a compound represented by Chemical Formula 1-2: [Chemical Formula 1-2] Na a-2v Ca v [(Ni x Mn y M1 z Cu w )]O 2 In the above chemical formula 1-2, M1 is Fe, and 0.9<a<1.1, 0.01<v<0.02, 0.27≤x≤0.37, 0.27≤y≤0.37, 0.27≤z≤0.37, 0.04<w<0.06, x+y+z+w=1.
  9. In paragraph 1, The above sodium composite transition metal oxide is a positive electrode active material for a sodium secondary battery in which the calcium is substituted in the sodium layer of the composite transition metal oxide and the copper is substituted in the transition metal layer of the composite transition metal oxide.
  10. In paragraph 1, The above sodium complex transition metal oxide has an O3 crystal structure in X-ray diffraction analysis, and the full width at half maximum (FWHM) of the (003) peak located at 2θ=15 to 17.5° is 0.1699 to 0.2599, and A positive electrode active material for sodium secondary batteries in which the NiO peak is substantially absent.
  11. A complex transition metal hydroxide precursor comprising at least nickel, manganese, and M1 (Co and/or Fe) is mixed with a copper compound and subjected to a first heat treatment, A coating process for coating at least a portion of the surface of the above-mentioned composite transition metal hydroxide precursor particles with copper; and The above copper-coated transition metal hydroxide precursor, calcium compound, and sodium compound are mixed and subjected to a second heat treatment, A method for manufacturing a positive electrode active material for a sodium secondary battery, comprising a doping process of substituting the surface and interior of sodium composite transition metal oxide particles with copper and calcium.
  12. In Paragraph 11, A method for manufacturing a positive electrode active material for a secondary battery, wherein in the above coating process (1) and doping process (2), the ratio of the heat treatment temperature (°C) (T2/T1) is 1.2 to 2 and the ratio of the heat treatment time (h) (H2/H1) is 1.5 to 2.5.
  13. In Paragraph 11, A method for manufacturing a positive electrode active material for a secondary battery, wherein, in the above coating and doping processes, the copper compound and the calcium compound are mixed such that the molar ratio of copper to calcium (Cu/Ca) is 1.5 to 4.
  14. In Paragraph 11, The above coating process (1) and doping process (2) are, The above-mentioned complex transition metal hydroxide precursor and sodium complex transition metal oxide are each secondary particles formed by the aggregation of at least one primary particle, wherein A method for manufacturing a positive electrode active material for a secondary battery, wherein the ratio (D/C) of the average particle size (D50) of the sodium composite transition metal oxide secondary particle (D) to the composite transition metal hydroxide precursor secondary particle (C) is 1.2 to 2.
  15. A cathode for a sodium secondary battery comprising a cathode active material according to any one of claims 1 to 10.
  16. A sodium secondary battery comprising a positive electrode according to paragraph 15; and a negative electrode.

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. Rechargeable batteries have been widely used as energy storage devices in various fields of electronic technology. Recently, with the surge in demand for lithium-ion rechargeable batteries, 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 essential for the commercialization of sodium-ion secondary batteries. Layered transition metal oxides, which have a simple structure, excellent electrochemical performance, and are easy to synthesize, are typically used as positive electrode active materials for sodium-ion secondary batteries. Layered transition metal oxides are typically classified into O3-type and P2-type depending on their crystal structure. Positive electrode active materials based on the O3-type structure exhibit a composition such as Na x (TM) O2 (2/3 < x ≤ 1), while positive electrode active materials based on the P2-type structure have a composition such as Na x (TM) O2 (x ≤ 2/3). P2-type layered oxides have relatively excellent cycle stability, but their commercial application is difficult due to disadvantages such as relatively degraded capacity characteristics resulting from a low sodium content. O3-type layered oxides have a higher energy density than P2-type layered oxide particles, but they have the disadvantage of reduced cycle stability due to greater structural changes during the charge-discharge process. Specifically, they have poor air and water stability, and during storage and processing, they react with surrounding H₂O and CO₂ to form sodium byproducts on the particle surface in the form of Na₂CO₃ and NaOH , causing structural degradation. As one of the various methods for doping cathode active materials to enhance properties, the introduction of mono- and multi-valence cations as doping elements is being studied. Since the doping elements are positioned within the lattice of the cathode active material, they can provide an effect that improves the physical and electrochemical properties of the cathode active material according to the unique characteristics of each doping element, such as binding energy and oxidation state. These doping elements can be selected from a variety of elements and adjusted to optimal concentrations depending on the desired effect. However, since the doping effect can vary depending on various internal and external factors, such as size, diffusivity, and the manufacturing environment of the cathode active material, complex doping combining multiple elements may be more advantageous for improving the characteristics of the cathode active material than single doping substituting a single element, taking these variables into account. Specifically, complex doping has the advantage of selectively and combinedly providing various effects that are available for each doping element, such as structural stability, thermal stability, changes in cation mixing, and capacity changes of the cathode active material. However, even in the case of such complex doping, the potential effects of the doping elements must be considered, along with the characteristics of the sodium and transition metal elements in the cathode active material into which the doping elements are introduced, and the correlations between the doping elements. If complex doping elements are formulated without such consideration, problems may arise where doping efficiency decreases or, conversely, the characteristics of the cathode active material are degraded. Therefore, there is a high need for technology capable of optimizing the composition and content of doping elements to more efficiently improve the characteristics of the cathode active material. In this invention, a composite doping technology capable of optimizing the composition and content of doping elements is developed to improve the structural stability of O3-type cathode active materials and to realize high capacity and excellent lifespan characteristics. Figure 1 is the result of surface SEM-EDS (Scanning electron microscopy and energy dispersive X-ray spectroscopy) mapping analysis of the surface copper-coated precursor particles prepared in Example 1. Figure