KR-20260063405-A - POSITIVE ELECTRODE ACTIVE MATERIAL AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

Abstract

The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more specifically, the present invention relates to a positive electrode active material with a polycrystalline structure in which stability is improved through shape control of primary particles and a lithium secondary battery including the same.

Inventors

• 이슬기
• 배진호
• 최진혁
• 신세희
• 김진규

Assignees

• 주식회사 에코프로비엠

Dates

Publication Date

20260507

Application Date

20241030

Claims (14)

1. As a positive electrode active material comprising a lithium transition metal oxide capable of lithium intercalation/deintercalation, The above lithium transition metal oxide has a secondary particle form in which a plurality of primary particles are aggregated, and The above lithium transition metal oxide is co-doped with aluminum and boron, and When r is the distance from the center of the secondary particle to the surface of the secondary particle, the average aspect ratio of the primary particles existing within the surface portion of the secondary particle, where the distance (d) from the center of the secondary particle is (1/3)r < d ≤ r, is 2.5 or greater and less than 5.0, Positive active material.
2. In paragraph 1, The average aspect ratio of the primary particles existing within the center of the secondary particles, where the distance (d) from the center of the secondary particles is 0 ≤ d ≤ (1/3)r, is smaller than the average aspect ratio of the primary particles existing within the surface of the secondary particles, where the distance (d) from the center of the secondary particles is (1/3)r < d ≤ r. Positive active material.
3. In paragraph 2, The average aspect ratio of the primary particles present within the center of the secondary particles is 1.5 or less, Positive active material.
4. In paragraph 1, The aspect ratio of the primary particle above exhibits a gradient that increases in the direction from the center of the secondary particle toward the surface of the secondary particle, Positive active material.
5. In paragraph 1, The above lithium transition metal oxide is represented by the following chemical formula 1, Positive active material: [Chemical Formula 1] Li a Ni 1-(b+c+d+e) Co b Mn c M1 d M2 e O 2 In the above chemical formula 1, M1 is Al and B, M2 is at least one selected from Na, K, Mg, Ca, Sr, Ba, Rb, Ce, Hf, Ta, Cr, F, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and 0.85≤a≤1.15, 0≤b≤0.20, 0≤c≤0.20, 0<d≤0.10, 0≤e≤0.10, 0<b+c≤0.40.
6. In paragraph 1, The average crystallite size of the above lithium transition metal oxide is 75 nm or more and less than 100 nm, Positive active material.
7. In paragraph 1, The full width at half-maximum (FWHM) of the peak corresponding to the (104) crystal plane, calculated from the diffraction spectrum obtained through X-ray diffraction (XRD) analysis using Cu-kα rays for the above positive active material, is 0.170° to 0.190°, Positive active material.
8. In paragraph 1, The average particle size of the primary particles is 0.1 μm to 1.0 μm, Positive active material.
9. In paragraph 1, The average particle size of the above secondary particles is 2.0 μm to 16.0 μm, Positive active material.
10. In paragraph 1, The sum of the concentrations (mol%) of aluminum and boron present at the interface between the primary particles located inside the secondary particles is greater than the sum of the concentrations (mol%) of aluminum and boron present inside the primary particles. Positive active material.
11. In paragraph 1, A coating layer containing aluminum and boron existing on the surface of the above secondary particles, Positive active material.
12. In paragraph 1, A coating layer containing aluminum and boron existing at the interface or gap between the primary particles located inside the secondary particles, Positive active material.
13. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 12.
14. A lithium secondary battery using a positive electrode according to Paragraph 13.

Description

Positive electric active material and lithium secondary battery comprising the same The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more specifically, the present invention relates to a positive electrode active material with a polycrystalline structure in which stability is improved through shape control of primary particles and a lithium secondary battery including the same. A battery stores electrical power by using materials capable of electrochemical reactions at the positive and negative electrodes. A representative example of such a battery is the lithium secondary battery, which stores electrical energy based on the difference in chemical potential when lithium ions intercalate or deintercalate at the positive and negative electrodes. The above lithium secondary battery is manufactured by using materials capable of reversible intercalation/deintercalation of lithium ions as positive and negative active materials, and by filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes. Lithium transition metal oxides are used as positive electrode active materials for lithium secondary batteries, and examples of such composite oxides are being studied include LiCoO2 , LiMn2O4 , LiNiO2 , and LiMnO2 . Among the above-mentioned cathode active materials, LiCoO2 is the most widely used due to its excellent lifespan characteristics and charge/discharge efficiency, but it has the disadvantage of having limited price competitiveness because it is expensive due to the resource limitations of cobalt used as a raw material. Lithium manganese oxides such as LiMnO2andLiMn2O4 have the advantages of excellent thermal stability and low cost, but they have the problem of low capacity and poor high-temperature characteristics. In addition, LiNiO2 -based cathode active materials have the advantage of exhibiting high discharge capacity, but they are difficult to synthesize due to active cation mixing of Li and Ni, and the rate characteristics and lifespan characteristics of the synthesized cathode active materials are very low. Accordingly, in order to improve low rate and lifetime characteristics while maintaining the high reversible capacity of LiNiO2 , lithium transition metal oxides of the ternary type, such as NCM (Ni-Co-Mn) and NCA (Ni-Co-Al), or the quaternary type, such as NCMA (Ni-Co-Mn-Al), in which some of the nickel is substituted with cobalt, manganese, and/or aluminum, have been developed. Since the reversible capacity decreases as the nickel content in these ternary or quaternary type lithium transition metal oxides decreases, research to increase the nickel content in lithium transition metal oxides has been actively conducted recently. However, as the nickel content in the lithium transition metal oxide increases , the mixing of cations within the crystal structure increases, leading to a decrease in stability or an increase in the content of unreacted lithium impurities such as LiOH and Li₂CO₃ on the surface. As the content of lithium impurities remaining on the surface of the lithium transition metal oxide increases, gas generation and swelling phenomena may be accelerated in a lithium secondary battery using the lithium transition metal oxide as a positive electrode active material. Furthermore, as the content of lithium impurities remaining on the surface of the lithium transition metal oxide increases, there is a problem in that the paste composition becomes gelled due to the lithium impurities when preparing a paste for forming a positive electrode active material layer using the lithium transition metal oxide. Accordingly, there are various attempts to reduce the content of lithium impurities remaining on the surface of the lithium transition metal oxide and to reduce side reactions between the surface of the lithium transition metal oxide and the electrolyte through surface coating of the lithium transition metal oxide. In addition, when a conductive coating layer is formed on the surface of the lithium transition metal oxide, it can contribute to improving rate capability by enhancing the ion or electron transport capacity mediated by the lithium transition metal oxide compared to when a non-conductive coating layer is formed on the surface of the lithium transition metal oxide. However, unlike a non-conductive coating layer, the electrochemical properties of a conductive coating layer change significantly due to the continuity and/or thickness of the coating layer. Therefore, if a non-uniform coating layer is formed on the surface of the lithium transition metal oxide, or if the coating material exists in the form of fine particles on the surface of the lithium transition metal oxide, it may be difficult to exhibit stable electrochemical properties for a long time due to the conductivity variation between particles. Meanwhile, most lithium transition metal oxides have a polycrystal