EP-4741350-A1 - POSITIVE ELECTRODE ACTIVE MATERIAL AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

Abstract

The present invention relates to a positive electrode active material and a lithium secondary battery comprising the same, and more particularly, to a positive electrode active material comprising a mid-Ni type lithium transition metal oxide having a relatively low nickel content, wherein the c-axis length of unit particles constituting the lithium transition metal oxide is increased to enhance the efficiency of reversible intercalation/deintercalation of lithium ions, thereby improving electrochemical characteristics, which are relatively insufficient compared to those of a high-Ni type lithium transition metal oxide having a relatively high nickel content, and to a lithium secondary battery comprising the same.

Inventors

• SON, YU JIN
• PARK, JUNG BAE
• CHOI, WOO SEOK
• PARK, JUNG GYU
• SHIN, YO SEOP
• HEO, Jun Hee
• KIM, SEOK JO
• HWANG, DO YOUNG
• LEE, SANG DON

Assignees

• ECOPRO BM CO., LTD.

Dates

Publication Date

20260513

Application Date

20250930

Claims (12)

1. A positive electrode active material comprising a lithium transition metal oxide capable of intercalation/deintercalation of lithium, wherein the lithium transition metal oxide has at least one form selected from a form of a single particle consisting of a single unit particle and a form of a pseudo-single particle form consisting of 30 or less unit particles aggregated, wherein the lithium transition metal oxide comprises at least lithium and a transition metal, wherein a content of nickel among the transition metal is 40 mol% or more and 70 mol% or less, and wherein an average crystallite size of the lithium transition metal oxide is from 160 nm to 195 nm.
2. The positive electrode active material of claim 1, wherein a content of cobalt among the transition metal is 10 mol% or less.
3. The positive electrode active material of claims 1 or 2, wherein a content of manganese among the transition metal is 20 mol% or more and 50 mol% or less.
4. The positive electrode active material of any one of claims 1 to 3, wherein the lithium transition metal oxide further comprises cobalt and manganese, and wherein a content of manganese among the transition metal is greater than a content of cobalt.
5. The positive electrode active material of any one of claims 1 to 4, wherein an average particle diameter (D 50 ) of the lithium transition metal oxide present in the form of a single particle is from 0.5 µm to 10.0 µm.
6. The positive electrode active material of any one of claims 1 to 5, wherein an average particle diameter (D 50 ) of the lithium transition metal oxide present in the form of a pseudo-single particle form is from 3.0 µm to 15.0 µm.
7. The positive electrode active material of any one of claims 1 to 6, wherein a c-axis length obtained from Rietveld analysis of X-ray diffraction of the lithium transition metal oxide is 14.260 Å or more.
8. The positive electrode active material of any one of claims 1 to 7, wherein the lithium transition metal oxide has a layered crystal structure in which a lithium layer containing lithium and a transition metal layer containing a transition metal are alternately arranged, and calcium is doped in at least one of the lithium layer and the transition metal layer.
9. The positive electrode active material of any one of claims 1 to 8, wherein a content of calcium among all elements excluding lithium in the lithium transition metal oxide is from 0.01 mol% to 1.0 mol%.
10. The positive electrode active material of any one of claims 1 to 9, wherein the lithium transition metal oxide is represented by Chemical Formula 1 below, [Chemical Formula 1] Li a Ni 1-(b+c+d+e) Co b Mn c Ca d M1 e O 2 Wherein, in the above Chemical Formula 1, M1 comprises at least one selected from Na, K, 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, 0.0001 ≤ d ≤ 0.01, 0 ≤ e ≤ 0.10, and 0.4 ≤ 1-(b+c+d+e) ≤ 0.7.
11. A positive electrode comprising the positive electrode active material of any one of claims 1 to 10.
12. A lithium secondary battery comprising the positive electrode of claim 11.

Description

BACKGROUND 1. Field of the Invention The present invention relates to a positive electrode active material and a lithium secondary battery comprising the same, and more particularly, to a positive electrode active material comprising a mid-Ni type lithium transition metal oxide having a relatively low nickel content, wherein the c-axis length of unit particles constituting the lithium transition metal oxide is increased to enhance the efficiency of reversible intercalation/deintercalation of lithium ions, thereby improving electrochemical characteristics, which are relatively insufficient compared to those of a high-Ni type lithium transition metal oxide having a relatively high nickel content, and to a lithium secondary battery comprising the same. 2. Discussion of Related Art Batteries store power by using materials capable of undergoing electrochemical reactions at a positive electrode and a negative electrode. A representative example of batteries is a lithium secondary battery that stores electrical energy by the difference in chemical potential when lithium ions are intercalated/deintercalated into/from the positive electrode and the negative electrode. The lithium secondary battery is manufactured by using materials capable of reversible intercalation/deintercalation of lithium ions as positive and negative electrode active materials and filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes. A lithium transition metal oxide is used as a positive electrode active material for a lithium secondary battery, and as an example, composite oxides such as LiCoO2, LiMn2O4, LiNiO2, LiMnO2, and the like are being studied. Among the positive electrode active materials, LiCoO2 is the most widely used due to its excellent lifetime characteristics and charge/discharge efficiency, but it has limitations in price competitiveness because cobalt, which is used as a raw material, is expensive due to resource constraints. Lithium manganese oxides such as LiMnO2 and LiMn2O4 have advantages of excellent thermal safety and low price, but also have problems of low capacity and poor high-temperature characteristics. In addition, a LiNiO2-based positive electrode active material exhibits battery characteristics such as high discharge capacity, but it is difficult to synthesize the LiNiO2-based positive electrode active material due to cation mixing between Li and transition metals, thereby causing significant problems in rate characteristics. Therefore, in order to improve the low rate and cycle characteristics of LiNiO2 while maintaining its high reversible capacity, ternary lithium transition metal oxides such as the so-called NCM (Ni-Co-Mn) and NCA (Ni-Co-Al), in which part of the nickel is substituted with cobalt, manganese, and/or aluminum, or quaternary lithium transition metal oxides such as NCMA (Ni-Co-Mn-Al) have been developed. Since the reversible capacity is reduced as the nickel content in the ternary or quaternary lithium transition metal oxide decreases, research has been widely conducted to increase the nickel content in the lithium transition metal oxide. However, as the content of nickel in the lithium transition metal oxide increases, cation mixing increases in the crystal structure, thereby reducing stability or increasing 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 may be promoted in a lithium secondary battery using the lithium transition metal oxide as a positive electrode active material. As the content of lithium impurities remaining on the surface of the lithium transition metal oxide increases, a paste composition becomes gel-like due to lithium impurities when a paste for forming a positive electrode active material layer is prepared using the lithium transition metal oxide. Accordingly, a washing process needs to be performed in the manufacturing process of the positive electrode active material to remove lithium impurities remaining on the surface of the lithium transition metal oxide. However, as the surface of the lithium transition metal oxide is damaged through this washing process, the electrochemical properties and stability of the lithium secondary battery using the lithium transition metal oxide as a positive electrode active material are degraded, and in particular, the problem of premature degradation of lifetime may occur. In addition, as the demand for lithium secondary batteries has recently grown rapidly 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 positive electrode active material accounts for the largest proportion of the material cost in lithium secondary batteries, and the cost of the positive electrode active material inevitably increases as the nickel