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KR-20260065121-A - positive electrode active material for sodium secondary battery, method for preparing the same and sodium secondary battery including the same

KR20260065121AKR 20260065121 AKR20260065121 AKR 20260065121AKR-20260065121-A

Abstract

One embodiment of the present invention provides a positive electrode active material for a sodium secondary battery comprising a sodium composite transition metal oxide containing at least sodium, a transition metal, a first doping metal, and a second doping metal, wherein the ratio of the ionic radius (R M1 ) of the first doping metal to the ionic radius (R) of the sodium (R M1 /R) is 0.8 to 1.2 and the ratio of the ionic radius (R M2 ) of the second doping metal (R M2 /R) is 0.5 to 0.7.

Inventors

  • 전예진
  • 이동욱
  • 박아람

Assignees

  • 주식회사 에코프로비엠

Dates

Publication Date
20260508
Application Date
20241031

Claims (15)

  1. It comprises a sodium complex transition metal oxide containing at least sodium, a transition metal, a first doping metal, and a second doping metal, and The ratio (R M1 / R) of the ionic radius (R) of the first doping metal to the ionic radius (R) of the sodium is 0.8 to 1.2, and A positive electrode active material for a sodium secondary battery, wherein the ratio (R M2 / R) of the ionic radius (R) of the second doping metal to the ionic radius (R) of the sodium is 0.5 to 0.7.
  2. In paragraph 1, A positive electrode active material for a sodium secondary battery, wherein the ratio of the ionic radius (R M2 ) of the second doping metal to the ionic radius (R Ni3+ ) of trivalent nickel (Ni 3+ ) (R M2 / R Ni3+ ) is 1.0 to 1.2.
  3. In paragraph 1, The first doping metal is a divalent cation, and The above second doping metal is a positive electrode active material for a sodium secondary battery, wherein the second doping metal is a 4 to 6 valent cation.
  4. In paragraph 3, The first doping metal mentioned above is Ca, and The above second doping metal is at least one selected from the group consisting of V, Mo, W, and Nb, a positive active material for a sodium secondary battery.
  5. In paragraph 1, The first doping metal is included in an amount of 0.5 to 2 at mol% with respect to the total amount of sodium (Na) and the first doping metal of the sodium complex transition metal oxide, and A positive electrode active material for a sodium secondary battery, wherein the second doping metal is included in an amount of 0.01 to 0.2 at mol% with respect to the total amount of metals excluding sodium (Na) and the first doping metal of the sodium composite transition metal oxide.
  6. In paragraph 1, The ratio (M2-O/M1-O) of the second doping metal-oxygen bonding force (M2-O) to the first doping metal-oxygen bonding force (M1-O) is 1.1 to 2, and A positive electrode active material for a sodium secondary battery, wherein the ratio (M2/M1) of the content (at mol) of the second doping metal (M2) to the content (at mol) of the first doping metal (M1) is 0.03 to 15%.
  7. In paragraph 1, The above sodium complex transition metal oxide is a positive electrode active material for a sodium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Na a M1 b [TM x M2 1-x ]O 2+w In the above chemical formula 1, TM is at least one selected from Ni and Fe, Mn and Co, M1 is Ca, M2 is at least one selected from W, V, Mo, and Nb, 0.8≤a≤1.1, 0.005≤b≤0.02, 0.8≤x≤0.9998, 0.0001≤1-x≤0.002, -0.1≤w≤0.1.
  8. In paragraph 1, The above sodium complex transition metal oxide comprises secondary particles formed by the aggregation of a plurality of primary particles, and A positive electrode active material for a sodium secondary battery, wherein the first doping metal and the second doping metal are located on the surface of the secondary particle, on the surface of the primary particle and/or inside the primary particle.
  9. In paragraph 1, The above sodium composite transition metal oxide is a positive electrode active material for a sodium secondary battery having an O3-type crystal structure.
  10. A method for manufacturing a positive electrode active material for a sodium secondary battery according to claim 1, comprising a process of dry mixing (a) a transition metal hydroxide precursor, a first doping metal compound, a second doping metal compound, and a sodium compound, and a process of calcining (b).
  11. In Paragraph 10, The above dry mixing involves mixing an equal amount of a sodium compound with a Na/M (total metal excluding Na) ratio greater than 0.8 and less than 1, and The above-mentioned first doping metal is mixed in an amount of 0.5 to 2 at mol% with respect to the total amount of Na and the first doping metal, and A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein the second doping metal is mixed at a concentration of 0.01 to 0.2 at mol% relative to the total amount of metals excluding Na and the first doping metal.
  12. In Paragraph 10, The first doping metal compound is an acetate compound, sulfide, nitride, phosphide, oxide, oxyhydroxide, hydroxide, or a combination thereof of Ca, and A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein the second doping metal compound is at least one acetate compound selected from W, V, Mo and Nb, sulfide, nitride, phosphide, oxide, oxyhydroxide, hydroxide, or a combination thereof.
  13. In Paragraph 10, A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein the above calcination is carried out at a temperature of 700 to 1,100°C for 5 to 40 hours.
  14. A cathode for a sodium secondary battery comprising a positive active material according to any one of claims 1 to 9.
  15. A sodium secondary battery comprising a positive electrode according to paragraph 14; a negative electrode; and an electrolyte.

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. In this case, 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 a surface/cross-sectional SEM-EDS mapping analysis image of the cathode active material particles prepared in Examples 1 to 4 and Comparative Example 1. Figures 2a, 2b, and 2c are a s