KR-20260063360-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 containing the same. More specifically, the present invention relates to a positive electrode active material capable of exhibiting improved operating characteristics in a high-voltage operating environment through surface modification of a Mid-Ni type lithium transition metal oxide having a relatively low nickel content, and a lithium secondary battery containing the same.

Inventors

• 손유진
• 허준희
• 이상돈
• 박정배
• 신요섭
• 황도영
• 김석조
• 최우석
• 박중규

Assignees

• 주식회사 에코프로비엠

Dates

Publication Date

20260507

Application Date

20241030

Claims (14)

1. A lithium transition metal oxide having a crystal structure belonging to the R-3m space group and having a nickel content of 40 mol% or more and 70 mol% or less among the transition metals; and A tungsten-containing coating layer located on the surface of the above lithium transition metal oxide; Includes, The lattice strain calculated through Rietveld Refinement on the diffraction spectrum obtained through X-ray diffraction (XRD) analysis using Cu-kα rays for the above-mentioned positive electrode active material is 0.00025 or less, Positive active material.
2. In paragraph 1, The content of cobalt among the above transition metals is 10 mol% or less, Positive active material.
3. In paragraph 1, The content of manganese among the above transition metals is 20 mol% or more and 50 mol% or less, Positive active material.
4. In paragraph 1, The above lithium transition metal oxide further includes cobalt and manganese, and Among the above transition metals, the manganese content is greater than the cobalt content, 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) Co b Mn c M1 d O 2 In the above chemical formula 1, M1 is at least one selected from Na, K, Mg, Ca, Sr, Ba, Rb, B, Ce, Hf, Ta, Cr, F, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and 0.95≤a≤1.15, 0≤b≤0.10, 0.20≤c≤0.50, 0≤d≤0.10, 0.4≤1-(b+c+d)≤0.7.
6. In paragraph 1, The lithium transition metal oxide has at least one form selected from a single-particle form consisting of one unit particle and a pseudo-single-particle form in which 30 or fewer unit particles are aggregated. Positive active material.
7. In paragraph 1, The average particle size (D 50 ) of the lithium transition metal oxide existing in the above single particle form is 1.0 μm or more and 8.0 μm or less, Positive active material.
8. In paragraph 1, The average particle size (D 50 ) of the lithium transition metal oxide existing in the above-mentioned pseudo-mono-particle form is 3.0 μm or more and 12.0 μm or less, Positive active material.
9. In paragraph 1, The above coating layer comprises lithium-tungsten oxide represented by the following chemical formula 2, Positive active material: [Chemical Formula 2] Li e W f O g In the above chemical formula 2, 0<e≤8, 0<f≤15, and 0<g≤20.
10. In paragraph 1, The average Ni occupancy within the Li 3a sites calculated by Rietveld Refinement on the diffraction spectrum obtained through X-ray diffraction (XRD) analysis using Cu-kα rays for the above-mentioned cathode active material is less than 3.5%, Positive active material.
11. In paragraph 1, The average crystallite size of the lithium transition metal oxide calculated by Rietveld Refinement on the diffraction spectrum obtained through X-ray diffraction (XRD) analysis using Cu-kα rays for the above-mentioned positive electrode active material is 160 nm to 200 nm, Positive active material.
12. In paragraph 1, The coating layer is formed in the form of islands that discontinuously occupy the surface of the lithium transition metal oxide. 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 containing the same. More specifically, the present invention relates to a positive electrode active material capable of exhibiting improved operating characteristics in a high-voltage operating environment through surface modification of a Mid-Ni type lithium transition metal oxide having a relatively low nickel content, and a lithium secondary battery containing 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 the cobalt used as a raw material is expensive. 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, a washing process to remove lithium impurities remaining on the surface of the lithium transition metal oxide must be necessarily included during the manufacturing process of the cathode active material. However, as damage is caused to the surface of the lithium transition metal oxide through this washing process, the electrochemical characteristics and stability of the lithium secondary battery using the lithium transition metal oxide as the cathode active material are degraded, and in particular, a problem of premature degradation of lifespan may occur. In addition, as the demand for lithium secondary batteries has grown rapidly in recent years and the cost of raw materials has also increased, the lithium secondary battery market has faced a strong demand for cost reduction. In particular, the cathode active material accounts for the largest share of the cost of lithium secondary batteries, and among them, the cost of the cathode active material inevitably increases as the content of nickel, an essential element of ternary or quaternary type lithium transition metal oxides, increases. In other words, while increasing the nickel content in the cathode active material improves reversible capacity