KR-20260062571-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. More specifically, the present invention relates to a positive electrode active material and a lithium secondary battery including the same, which reduces conductivity deviation between unit particles due to the formation of an uneven coating layer and improves electrochemical properties including capacity characteristics and rate characteristics by forming a cobalt-rich region with a concentrated distribution of cobalt on the surface of unit particles instead of coating the surface of unit particles constituting a lithium transition metal oxide.

Inventors

• 조민수
• 곽환욱
• 공보현
• 최문호
• 배진호
• 남유진
• 이재균
• 선영회

Assignees

• 주식회사 에코프로비엠

Dates

Publication Date

20260507

Application Date

20241029

Claims (13)

1. As a positive electrode active material comprising a lithium transition metal oxide containing lithium, nickel, and cobalt, The above lithium transition metal oxide has a secondary particle form in which a plurality of unit particles are aggregated, and On the surface of one or more of the above-mentioned unit particles, there exists a cobalt-rich region in which the distribution of cobalt is skewed, and The thickness of the above cobalt-rich region is 1 nm to 100 nm, and The ratio (I2/I1) of the average intensity (I2) of the peak existing within the 2θ=45.25±0.25° region to the maximum intensity (I1) of the peak existing within the 2θ=44.5±0.5° region in the diffraction spectrum obtained through X-ray diffraction (XRD) analysis using Cu-kα rays for the above-mentioned positive electrode active material is greater than 0.001 and less than 0.015. Positive active material.
2. In paragraph 1, The average mole fraction of cobalt measured within the above cobalt-rich region is greater than the average mole fraction of cobalt within the above unit particle, Positive active material.
3. In paragraph 1, The average mole fraction of cobalt measured within the above cobalt-rich region is 1.35 times or more and less than 10 times the mole fraction of cobalt measured at the center of the unit particle, Positive active material.
4. In paragraph 1, The above lithium transition metal oxide is represented by the following chemical formula 1, Positive active material: [Chemical Formula 1] Li w Ni 1-(x+y+z) Co x Mn y M1 z O 2 In the above chemical formula 1, M1 is at least one selected from Na, K, Mg, Ba, B, Ce, Hf, Ta, Cr, F, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, P, Sr, Ge, Nd, Gd and Cu, and 0.95≤w≤1.15, 0<x≤0.20, 0≤y≤0.20, 0<z≤0.20.
5. In paragraph 1, The average particle size of the above unit particles is 0.1 μm to 1.0 μm, Positive active material.
6. In paragraph 1, The average particle size of the above secondary particles is 2.0 μm to 16.0 μm, Positive active material.
7. In paragraph 1, Cobalt-containing oxides are not present on the surface of the above secondary particles, Positive active material.
8. In paragraph 1, In which cobalt-containing oxides are not present in the gaps between adjacent unit particles or in the grain boundaries formed by contact between adjacent unit particles, Positive active material.
9. In paragraph 8, The average mole fraction of cobalt measured within the above cobalt-rich region is greater than the mole fraction of cobalt measured at the grain boundaries formed by contact between adjacent unit particles, Positive active material.
10. In paragraph 1, The peak intensity ratio (I(003)/I(104)) of the peak corresponding to the (003) crystal plane to 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 1.5 to 2.0. Positive active material.
11. In paragraph 1, The difference between 2θ (110), where a peak corresponding to the (110) crystal plane is observed and 2θ (108), where a peak corresponding to the (108) crystal plane is observed, calculated from the diffraction spectrum obtained through X-ray diffraction (XRD) analysis using Cu-kα rays for the above positive active material, is 0.3° to 0.5°. Positive active material.
12. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 11.
13. A lithium secondary battery using a positive electrode according to Paragraph 12.

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. More specifically, the present invention relates to a positive electrode active material and a lithium secondary battery including the same, which reduces conductivity deviation between unit particles due to the formation of an uneven coating layer and improves electrochemical properties including capacity characteristics and rate characteristics by forming a cobalt-rich region with a concentrated distribution of cobalt on the surface of unit particles instead of coating the surface of unit particles constituting a lithium transition metal oxide. 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 problems such as low capacity and poor high-temperature characteristics. In addition, LiNiO2 -based cathode active materials exhibit high discharge capacity battery characteristics, but synthesis is difficult due to cation mixing between Li and transition metals, and consequently, there are significant problems with rate characteristics. 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 medi