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CN-121983528-A - Positive electrode active material and lithium secondary battery including the same

CN121983528ACN 121983528 ACN121983528 ACN 121983528ACN-121983528-A

Abstract

The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a positive electrode active material capable of exhibiting improved driving characteristics under a high voltage operating environment by modifying the surface of a medium nickel (Mid-Ni) lithium transition metal oxide having a relatively low nickel content, and a lithium secondary battery including the same.

Inventors

  • SUN WEIZHEN
  • XU JUNXI
  • LI XIANGDUN
  • Pu Zhengpei
  • Shen Yaoxie
  • Huang Duyong
  • Jin Xizuo
  • Cui Daishuo
  • Pu Zhongkui

Assignees

  • 艾可普罗BM有限公司

Dates

Publication Date
20260505
Application Date
20251029
Priority Date
20241030

Claims (14)

  1. 1. A positive electrode active material, comprising: A lithium transition metal oxide having a crystal structure belonging to the R-3m space group and containing nickel in an amount of 40 to 70 mol% inclusive, and A tungsten-containing coating layer located on the surface of the lithium transition metal oxide; the lattice strain calculated by Rietveld refinement of the diffraction spectrum obtained by X-ray diffraction analysis of the positive electrode active material using cu—kα rays was 0.00025 or less.
  2. 2. The positive electrode active material according to claim 1, wherein the cobalt content in the transition metal is 10 mol% or less.
  3. 3. The positive electrode active material according to claim 1, wherein the content of manganese in the transition metal is 20 mol% or more and 50 mol% or less.
  4. 4. The positive electrode active material according to claim 1, wherein the lithium transition metal oxide further comprises cobalt and manganese, and wherein the content of manganese in the transition metal is greater than the content of cobalt.
  5. 5. The positive electrode active material according to claim 1, wherein, The lithium transition metal oxide is represented by the following chemical formula 1: [ chemical formula 1] Li a Ni 1-(b+c+d) Co b Mn c M1 d O 2 In the above-mentioned 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, 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. 6. The positive electrode active material according to claim 1, wherein, The lithium transition metal oxide has at least one form selected from a single particle form composed of one unit particle and a pseudo single particle form composed of 30 or less unit particles aggregated.
  7. 7. The positive electrode active material according to claim 1, wherein, The average particle diameter D 50 of the lithium transition metal oxide existing in the form of single particles is 1.0 μm or more and 8.0 μm or less.
  8. 8. The positive electrode active material according to claim 1, wherein, The average particle diameter D 50 of the lithium transition metal oxide existing in the pseudo-single particle form is 3.0 μm or more and 12.0 μm or less.
  9. 9. The positive electrode active material according to claim 1, wherein, The above coating includes a lithium tungsten oxide represented by the following chemical formula 2: [ chemical formula 2] Li e W f O g In the above-mentioned chemical formula 2, 0<e is less than or equal to 8,0< f is less than or equal to 15, and 0< g is less than or equal to 20.
  10. 10. The positive electrode active material according to claim 1, wherein, The average Ni occupancy in the Li 3a site calculated by Rietveld refinement was lower than 3.5% for the diffraction spectrum obtained by X-ray diffraction analysis of the positive electrode active material using cu—kα rays.
  11. 11. The positive electrode active material according to claim 1, wherein, For a diffraction spectrum obtained by subjecting the positive electrode active material to X-ray diffraction analysis using cu—kα rays, the average crystal grain size of the lithium transition metal oxide calculated by Rietveld refinement is 160nm to 200nm.
  12. 12. The positive electrode active material according to claim 1, wherein, The coating layer is formed in an island shape discontinuously occupying the surface of the lithium transition metal oxide.
  13. 13. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 12.
  14. 14. A lithium secondary battery, characterized in that the positive electrode according to claim 13 is used.

Description

Positive electrode active material and lithium secondary battery including the same Technical Field The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a positive electrode active material capable of exhibiting improved driving characteristics under a high voltage operating environment by modifying the surface of a medium nickel (Mid-Ni) lithium transition metal oxide having a relatively low nickel content, and a lithium secondary battery including the same. Background Batteries store electrical energy using substances capable of undergoing electrochemical reactions at the positive and negative electrodes. As a representative example of the above-mentioned battery, there is a lithium secondary battery that stores electric energy by a difference in chemical potential (chemical potential) when lithium ions are intercalated into and deintercalated from the positive electrode and the negative electrode. The lithium secondary battery is produced by using a substance capable of reversibly intercalating/deintercalating lithium ions as a positive electrode active material and as a negative electrode active material, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode. As a positive electrode active material of a lithium secondary battery, for example, a composite oxide of LiCoO 2、LiMn2O4、LiNiO2、LiMnO2 or the like is currently being studied. Among the above positive electrode active materials, liCoO 2 has excellent life characteristics and charge and discharge efficiency and is most widely used, but cobalt used as a raw material is expensive and thus has a disadvantage of limited price competitiveness. The lithium manganese-based oxide such as LiMnO 2、LiMn2O4 has the advantages of excellent thermal stability and low cost, but has the problems of small capacity and poor high temperature characteristics. Further, liNiO 2 -type positive electrode active materials exhibit battery characteristics of high discharge capacity, but have problems that not only synthesis is difficult due to active cation mixing (cation mixing) between lithium and nickel, but also the rate characteristics and lifetime characteristics of the synthesized positive electrode active materials are low. Accordingly, in order to improve low-rate characteristics and lifetime characteristics while maintaining a high reversible capacity of LiNiO 2, so-called ternary type lithium composite oxides have been developed in which a part of nickel is replaced with cobalt, manganese and/or aluminum, so-called ternary type lithium composite oxides such as NCM (Ni-Co-Mn) and NCA (Ni-Co-Al), or quaternary type lithium composite oxides such as NCMA (Ni-Co-Mn-Al). Since the reversible capacity is lower as the nickel content in the ternary or quaternary lithium composite oxide is lower as described above, recently, active research has been conducted to increase the nickel content in the lithium composite oxide. However, as the nickel content in the lithium composite oxide increases, the cation mixing phenomenon in the crystal structure increases, resulting in a decrease in stability, or there is a problem in that the content of unreacted lithium impurities such as LiOH and Li 2CO3 increases in the surface. As the content of lithium impurities remaining on the surface of the lithium composite oxide increases, gas generation and swelling phenomena in a lithium secondary battery using the lithium composite oxide as a positive electrode active material may be exacerbated. As the content of lithium impurities remaining on the surface of the above lithium composite oxide increases, there is a problem in that a paste composition gels (gel) due to lithium impurities when the paste for forming a positive electrode active material layer is prepared using the above lithium composite oxide. Therefore, in the process for producing the positive electrode active material, a water washing process is necessary to remove lithium impurities remaining on the surface of the lithium composite oxide. However, since the surface of the lithium composite oxide is damaged by such a water washing process, electrochemical characteristics and stability of a lithium secondary battery using the lithium composite oxide as a positive electrode active material are lowered, and particularly, there is a possibility that a problem of premature life failure may occur. In addition, in recent years, as the demand for lithium secondary batteries has rapidly increased, the cost of raw materials has also increased, and the market for lithium secondary batteries has been faced with a strong demand for cost reduction. In particular, the positive electrode active material occupies the highest cost specific gravity in the lithium secondary battery, wherein the higher the content of nickel, which is an essential element in the ternary or quaternary type lith