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KR-20260062227-A - Cathode active material for sodium secondary battery, manufacturing method thereof, and sodium secondary battery comprising the same

KR20260062227AKR 20260062227 AKR20260062227 AKR 20260062227AKR-20260062227-A

Abstract

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 including the same. Specifically, it proposes a positive electrode active material for a sodium secondary battery comprising a sodium-containing raw material, a transition metal oxide, and a single-particle sodium composite transition metal oxide comprising a dopant for forming a single particle, a method for manufacturing the same, and a sodium secondary battery including the same. According to the present invention, through the dopant, single particles can be synthesized even at a relatively low calcination temperature, the synthesis process cost can be reduced, and structural stability and excellent thermal stability can be achieved.

Inventors

  • 황장연
  • 강효경
  • 류성제

Assignees

  • 한양대학교 산학협력단

Dates

Publication Date
20260507
Application Date
20241028

Claims (20)

  1. It is a sodium complex transition metal oxide in the form of a single particle mixed with a sodium-containing raw material, a transition metal oxide, and a dopant, and The above dopant is a positive electrode active material for a sodium secondary battery, which is barium (Ba) or an oxide containing barium (Ba).
  2. In claim 1, The above dopant A positive electrode active material for a sodium secondary battery, comprising 0.3% to 2% by weight of a total of 100% by weight of a sodium complex transition metal oxide.
  3. In claim 1, A positive electrode active material for a sodium secondary battery, mixed in a molar ratio of the above sodium-containing raw material : transition metal oxide = 1~1.2 : 1.
  4. In claim 1, The above sodium-containing raw material is A positive electrode active material for a sodium secondary battery, comprising one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.
  5. In claim 1, The above transition metal oxide is A positive electrode active material for a sodium secondary battery comprising one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.
  6. In claim 1, The above-mentioned sodium complex transition metal oxide in single-particle form is A positive electrode active material for a sodium secondary battery represented by the following chemical formula 1. [Chemical Formula 1] Ba-doped Na a [Ni b M 1 c Mn d M 2 e ]O 2 M 1 is one or more selected from Co and Fe, and M₂ is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.4.
  7. In claim 6, a is 0.8 to 1, and b, c, d, and e are positive electrode active materials for sodium secondary batteries, the sum of which remains 1.
  8. In claim 6, b, c, and d are positive electrode active materials for sodium secondary batteries, each having a value of 0.2 to 0.6.
  9. In claim 6, A positive electrode active material for a sodium secondary battery, in which e is 0.01 to 0.2.
  10. In claim 1, The above-mentioned positive electrode active material for a sodium secondary battery is A positive electrode active material for a sodium secondary battery having a layered crystal structure (P2) or an O3 structure.
  11. In claim 1, The above-mentioned positive electrode active material for a sodium secondary battery is A positive electrode active material for a sodium secondary battery, having a particle size of 3㎛ to 10㎛ and a single particle form.
  12. A step of mixing a sodium-containing raw material with a transition metal oxide and a dopant; and A method for manufacturing a cathode active material for a sodium secondary battery, comprising the step of heat-treating the above mixture at a temperature of 900°C to 1000°C for 10 to 20 hours to obtain a cathode active material for a sodium secondary battery in the form of a single particle.
  13. In claim 12, The above dopant A method for manufacturing a positive electrode active material for a sodium secondary battery, which is barium (Ba) or an oxide containing barium (Ba).
  14. In claim 12, The above dopant A method for manufacturing a positive electrode active material for a sodium secondary battery, comprising 0.3% to 2% by weight of the total 100% by weight of the above mixture.
  15. In claim 12, A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein the above sodium-containing raw material : transition metal oxide is mixed in a molar ratio of 1 to 1.2 : 1.
  16. In claim 12, The above sodium-containing raw material is A method for manufacturing a positive electrode active material for a sodium secondary battery, comprising one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.
  17. In claim 12, The above transition metal oxide is A method for manufacturing a positive electrode active material for a sodium secondary battery comprising one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.
  18. In claim 12, A method for manufacturing a cathode active material for a sodium secondary battery, wherein the cathode active material in the form of a single particle obtained through the above heat treatment is composed of the following chemical formula 1. [Chemical Formula 1] Ba-doped Na a [Ni b M 1 c Mn d M 2 e ]O 2 M 1 is one or more selected from Co and Fe, and M₂ is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.4.
  19. In claim 12, The above-mentioned single-particle cathode active material for a sodium secondary battery is A method for manufacturing a positive electrode active material for a sodium secondary battery having a layered crystal structure (P2) or an O3 structure.
  20. In claim 12, The above-mentioned single-particle cathode active material for a sodium secondary battery is Method for manufacturing a positive electrode active material for a sodium secondary battery, having a particle size of 3㎛ to 10㎛.

Description

Cathode active material for sodium secondary battery, manufacturing method thereof, and sodium secondary battery comprising 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 including the same. Currently, demand for lithium-ion batteries is increasing as they can be used for large-scale applications such as high-capacity energy storage systems (ESS) and electric vehicles (EVs). However, since lithium-ion batteries utilize large amounts of rare metals like lithium and cobalt, there are concerns regarding the supply of raw materials to meet the growing demand. Sodium secondary batteries are being researched as a solution to the disadvantages of this raw material supply, and sodium secondary batteries have the advantage of being environmentally friendly and having excellent price competitiveness compared to lithium secondary batteries. However, due to the large ionic radius of sodium ions, sodium secondary batteries need to improve lifespan characteristics, namely the low capacity retention rate and thermal stability issues that occur during repeated charging and discharging. Currently, cathode active materials used in sodium secondary batteries are mainly synthesized using precursors synthesized via the coprecipitation method. As such, cathode active materials for sodium secondary batteries synthesized via the coprecipitation method exist in the form of secondary particles formed by the aggregation of nano-sized primary particles. However, in the case of cathode active materials in the form of secondary particles, aggregated primary particles separate during the charging process, and microcracks occur in the secondary particles. Consequently, the newly exposed surfaces accelerate side reactions in the electrolyte, causing degradation of battery characteristics such as gas generation and electrolyte depletion. Here, the coprecipitation method is a method of manufacturing aggregated secondary spherical particles by precipitating a solution of complex metal components in a reactor; however, due to the complex process, it incurs high processing costs and presents environmental issues such as wastewater. In order to solve the aforementioned problems regarding the cathode active material for sodium secondary batteries in the form of secondary particles synthesized through such co-precipitation methods, a single-particle cathode active material is being developed through a simple solid-state method in which a transition metal oxide is mixed with a sodium source and then calcined without using a precursor. Single particles refer to micro-sized single particles. Because these particles consist of a single grain boundary, they possess strong resistance to volume expansion during the charge-discharge process, thereby suppressing microcracks. Additionally, single particles can improve material stability by minimizing side reactions due to their small reaction electrode/electrolyte specific surface area. Single particles offer the advantage of high tap density (g/cc) and excellent mechanical strength, which can improve energy density per unit volume during post-processing. However, when manufacturing cathode active materials for sodium secondary batteries, calcination at a higher temperature compared to polycrystalline materials is required to form single particles. However, when particle growth is promoted through high-temperature calcination, particle aggregation is severe, and NiO impurity phases may be formed due to the dissolution limit of nickel (Ni). Therefore, high-temperature calcination methods often involve additional grinding, washing, and annealing steps after initial calcination, which can be said to add complexity to the synthesis process. Figure 1 is SEM data for the cathode active materials of Preparation Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, 4, and 5. Figure 2 is XRD data for the cathode active materials of Preparation Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, and 5. Figure 3 is data showing the discharge capacity and Coulomb efficiency according to the number of cycles of half-cells using the cathode active materials of Preparation Examples 1, 2, and 3 and Comparative Examples 4 and 5. Figure 4 is SEM-EDS data for a cross-section of the cathode active material of Preparation Example 1. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 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 described herein and may be embodied in different forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and com