KR-20260065739-A - positive electrode active material and lithium secondary battery containing the same

Abstract

The present invention relates to a positive electrode active material and a lithium secondary battery including the same. More specifically, the present invention relates to a positive electrode active material and a lithium secondary battery including the same, wherein the growth of primary particles and crystallites is controlled by using a dopant during the synthesis of a precursor of the positive electrode active material and synthesizing the positive electrode active material using a precursor in which the dopant obtained therefrom is uniformly distributed, thereby improving the lifespan characteristics and storage stability at high temperatures.

Inventors

• 전재우
• 김광운
• 이지용
• 김희영
• 배민기
• 박승철
• 박중훈
• 신세영
• 최규연
• 권정희
• 박도윤

Assignees

• 주식회사 에코프로비엠

Dates

Publication Date

20260511

Application Date

20250922

Priority Date

20241029

Claims (14)

1. A positive electrode active material comprising a lithium transition metal oxide having a layered crystal structure belonging to the R-3m space group, At least one dopant selected from Al, Zr, Na, S, Mg, Ti, and B exists in a doped state within the crystal lattice of the lithium transition metal oxide, and The average crystallite size obtained from Rietveld analysis of the diffraction spectrum obtained from X-ray diffraction analysis using Cu-Kα rays for the above-mentioned positive electrode active material is greater than 57 nm and less than 95 nm, and The average aspect ratio of the primary particles calculated from the cross-sectional SEM image of the above lithium transition metal oxide is 1.9 or greater and less than 2.6, Positive active material.
2. In paragraph 1, Among the lithium transition metal oxides, at least one dopant selected from Al, Zr, Na, S, Mg, Ti, and B is present in an amount of 0.1 mol% or more and 1 mol% or less with respect to all elements excluding lithium. Positive active material.
3. In paragraph 1 or 2, The above lithium transition metal oxide comprises at least one selected from nickel, cobalt, manganese, and aluminum, Positive active material.
4. In any one of paragraphs 1 through 3, The above lithium transition metal oxide includes nickel, cobalt, and manganese, Positive active material.
5. In any one of paragraphs 1 through 4, The above lithium transition metal oxide contains 75 mol% or more of nickel with respect to all elements excluding lithium, Positive active material.
6. In any one of paragraphs 1 through 5, The above lithium transition metal oxide is a positive electrode active material having an average composition represented by the following chemical formula 1: [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 at least one selected from Al, Zr, Na, S, Mg, Ti, and B, and M2 is at least one selected from K, Ca, Sr, Ba, Rb, Ce, Hf, Ta, Cr, F, V, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and 0.95≤a≤1.15, 0≤b≤0.20, 0≤c≤0.20, 0.001≤d≤0.01, 0≤e≤0.05, 0.75≤1-(b+c+d+e).
7. In any one of paragraphs 1 through 6, A crystallite size calculated by Scherrer's equation from the diffraction peak corresponding to the (003) plane in the diffraction spectrum obtained from X-ray diffraction analysis using Cu-Kα rays for the above positive active material, which is 40 nm or more and less than 80 nm Positive active material.
8. In any one of paragraphs 1 through 7, A ratio of the crystallite size calculated by Scherrer's formula from the diffraction peak corresponding to the (104) plane to the crystallite size calculated by Scherrer's formula from the diffraction peak corresponding to the (003) plane in the diffraction spectrum obtained from X-ray diffraction analysis using Cu-Kα rays for the above positive active material is 0.55 or greater and 0.80 or less, Positive active material.
9. In any one of paragraphs 1 through 8, It includes a coating layer formed on at least a portion of the surface of the lithium transition metal oxide, and The coating layer comprises at least one selected from Ti, Al, Cr, Zr, B, Na, and Ca, Positive active material.
10. In Paragraph 9, The above lithium transition metal oxide is a secondary particle formed by the aggregation of a plurality of primary particles, and The coating layer has an island shape formed on a part of at least one of the surface of the primary particle, the interface between the primary particles, and the surface of the secondary particle, or has a shape that surrounds at least one of the surface of the primary particle, the interface between the primary particles, and the surface of the secondary particle. Positive active material.
11. In Article 9 or Article 10, The above coating layer comprises at least one metal oxide represented by the following chemical formula 2, Cathode active material: [Chemical Formula 2] Li f M3 g O h In the above chemical formula 2, M3 is at least one selected from Ti, Al, Cr, Zr, B, Na, and Ca, and 0≤f≤10, 0<g≤8, 0<h≤15.
12. In any one of paragraphs 9 through 11, The above coating layer further comprises at least one metal oxide represented by the following chemical formula 3, Positive active material: [Chemical Formula 3] Li i M4 j O k In the above chemical formula 3, M4 is at least one selected from Ni, Mn, Co, S, Mg, Ca, Sr, Ba, Rb, Ce, Hf, Ta, F, V, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and 0≤i≤10, 0<j≤8, 0<k≤15.
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

Cathode active material and lithium secondary battery containing the same Cathode active material and lithium secondary battery containing the same The present invention relates to a positive electrode active material and a lithium secondary battery including the same. More specifically, the present invention relates to a positive electrode active material and a lithium secondary battery including the same, wherein the growth of primary particles and crystallites is controlled by using a dopant during the synthesis of a precursor of the positive electrode active material and synthesizing the positive electrode active material using a precursor in which the dopant obtained therefrom is uniformly distributed, thereby improving the lifespan characteristics and storage stability at high temperatures. 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 lithium transition metal oxides increases , there is a problem in that the mixing of cations within the crystal structure increases, leading to reduced 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 promoted in a lithium secondary battery using the lithium transition metal oxide as a positive electrode active material. In addition, as the content of lithium impurities remaining on the surface of the lithium transition metal oxide increases, there is a problem that the paste composition becomes gelled due to the lithium impurities when manufacturing a paste for forming a positive electrode active material layer using the lithium transition metal oxide. Nevertheless, high-Ni type cathode active materials with a high nickel content are attracting attention for the manufacture of higher-performance lithium secondary batteries. However, as mentioned above, high-Ni type cathode active materials exhibit low lifespan characteristics (especially at high temperatures) and storage stability due to issues such as reduced crystallinity and gas generation caused by cation mixing; therefore, there is a need to develop cathode active materials to improve these characteristics. For convenience, specific terms are defined herein to facilitate a better understanding of the present invention. Unless otherwise defined herein, scientific and technical terms used in this invention shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form,