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EP-4742306-A1 - METHOD FOR ANALYZING CATHODE ACTIVE MATERIAL, CATHODE ACTIVE MATERIAL, CATHODE COMPRISING SAME, AND LITHIUM SECONDARY BATTERY

EP4742306A1EP 4742306 A1EP4742306 A1EP 4742306A1EP-4742306-A1

Abstract

The present invention relates to a method for analyzing a cathode active material, a cathode active material, a cathode and a lithium secondary battery, and, to: a method for analyzing a cathode active material; a cathode active material having a slope, obtained through the analysis method, of 0.00110-0.00130; a cathode comprising same; and a lithium secondary battery, the method comprising the steps of: (S1) preparing a cathode active material that comprises a layer-structured lithium-rich manganese-based oxide, which comprises both a Li 2 MnO 3 phase and a LiMO 2 (here, M is an element comprising at least one selected from Ni and Mn) phase, and manufacturing a lithium secondary battery that comprises a cathode comprising a cathode active material layer comprising 80 wt% or more of the cathode active material on the basis of the total weight of the cathode active material layer; (S2) obtaining a specific capacity-voltage graph (x-axis: specific capacity (mAh/g), and y-axis: voltage (V)) by activating the lithium secondary battery at a 0.1C-rate at 45°C ; and (S3) obtaining a slope by linearly fitting, in a section of the graph, data in which a voltage is 4.40-4.65 V.

Inventors

  • JEONG, MYEONG SANG
  • YOON, JU HAN
  • LEE, SEONG NAM
  • KIM, WON TAE
  • LIM, YOUNG GEUN

Assignees

  • LG Chem, Ltd.

Dates

Publication Date
20260513
Application Date
20240819

Claims (15)

  1. A method for analyzing a positive electrode active material, the method comprising: (S1) preparing a positive electrode active material comprising a lithium-rich manganese oxide having a layered structure comprising both a Li 2 MnO 3 phase and a LiMO 2 phase (where M is an element comprising at least one selected from Ni and Mn), and manufacturing a lithium secondary battery comprising a positive electrode comprising a positive electrode active material layer comprising the positive electrode active material in an amount of at least 80 wt% with respect to a total weight of the positive electrode active material layer; (S2) obtaining a specific capacity-voltage graph (X-axis: specific capacity (mAh/g), Y-axis: voltage (V)) obtained by activating the lithium secondary battery at 45 °C with a 0.1 C-rate; and (S3) in the graph, applying linear fitting to data in a voltage range of 4.40 to 4.65 V to obtain a slope.
  2. The method of claim 1, wherein the lithium-rich manganese oxide exhibits a Li/Me (lithium (Li) to total metals excluding lithium (Me)) molar ratio of greater than 1.00 and 2.00 or less.
  3. The method of claim 1, wherein the lithium-rich manganese oxide exhibits a Li/Me (lithium (Li) to total metals excluding lithium (Me)) molar ratio of 1.24 to 1.36.
  4. The method of claim 1, wherein the lithium-rich manganese oxide contains at least 50 mol% of Mn with respect to total metals excluding lithium.
  5. The method of claim 1, wherein the lithium-rich manganese oxide has a composition represented by Formula 1 below: [Formula 1] Li 1+x Ni a Mn b M c O 2 wherein, in Formula 1 above, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.10.
  6. The method of claim 1, wherein the linear fitting involves performing linear regression analysis using weighted least squares in a program of Origin.
  7. A positive electrode active material comprising a lithium-rich manganese oxide having a layered structure comprising both a Li 2 MnO 3 phase and a LiMO 2 phase (where M is an element comprising at least one selected from Ni and Mn), wherein in a specific capacity-voltage graph (X-axis: specific capacity (mAh/g), Y-axis: voltage (V)) obtained by activating a lithium secondary battery comprising a positive electrode comprising a positive electrode active material layer comprising the positive electrode active material in an amount of at least 80 wt% with respect to a total weight of the positive electrode active material layer at 45 °C with a 0.1 C-rate, a slope of the graph obtained by applying linear fitting to data in a voltage range of 4.40 to 4.65 V is 0.00115 to 0.00150.
  8. The positive electrode active material of claim 7, wherein the lithium-rich manganese oxide exhibits a Li/Me (lithium (Li) to total metals excluding lithium (Me)) molar ratio of greater than 1.00 and 2.00 or less.
  9. The positive electrode active material of claim 7, wherein the lithium-rich manganese oxide exhibits a Li/Me (lithium (Li) to total metals excluding lithium (Me)) molar ratio of 1.24 to 1.36.
  10. The positive electrode active material of claim 7, wherein the lithium-rich manganese oxide contains at least 50 mol% of Mn with respect to total metals excluding lithium.
  11. The positive electrode active material of claim 7, wherein the lithium-rich manganese oxide has a composition represented by Formula 1 below: [Formula 1] Li 1+x Ni a Mn b M c O 2 wherein, in Formula 1 above, M is at least one selected from W, Al, B, Mo, Ti, Co, V, P, Mg, Fe, K, Ca, Na, Y, and Nb, and 0.10 ≤ x ≤ 0.20, 0 < a ≤ 0.50, 0.50 ≤ b < 1.0, and 0 ≤ c ≤ 0.10.
  12. The positive electrode active material of claim 7, wherein the lithium-rich manganese oxide has a tap density of 1.5 g/cm 3 to 2.5 g/cm 3 .
  13. The positive electrode active material of claim 7, wherein the lithium-rich manganese oxide has an average particle size (D 50 ) of 2.0 µm to 20.0 µm.
  14. A positive electrode comprising the positive electrode active material according to any one of claims 7 to 13.
  15. A lithium secondary battery comprising the positive electrode according to claim 14.

Description

TECHNICAL FIELD Cross-reference to Related Applications The present application claims the benefit of the priority of Korean Patent Application No. 10-2023-0108534, filed on August 18, 2023, which is hereby incorporated by reference in its entirety. Technical Field The present invention relates to a method for analyzing a positive electrode active material, a positive electrode active material, and a positive electrode and a lithium secondary battery which include the same. BACKGROUND ART Lithium secondary batteries are composed of four key components: a positive electrode, a negative electrode, a separator, and an electrolyte. In particular, a positive electrode active material included in the positive electrode is a critical factor in determining the capacity, power output, and lifespan of batteries. To achieve high energy density, power output, and lifespan in lithium secondary batteries, it is essential to improve the performance of the positive electrode active material, and for this reason, extensive research has been conducted lately to develop high-performance positive electrode active materials. A Li- and Mn-rich layered oxide (LMRO), a type of positive electrode active material, is a mixed phase composed of Li2MnO3 and LiMO2 (M=Ni, Mn, Co) phases, and offers high energy density and enhanced stability, making it suitable as a next-generation positive electrode active material. In addition, the high Mn content in LMRO, a relatively inexpensive element, makes it a more cost-effective option compared to typical high-Ni NCM positive electrode materials. However, the LMRO undergoes irreversible capacity loss during a first formation process at high voltages, resulting in reduced efficiency compared to NCM-based positive electrode materials, and undergoes structural changes from a layered structure to a spinel structure and eventually to rock-salt structure, resulting in voltage fading and the release of O2 gas caused by crystal structure degradation. To address these issues, research for achieving enhanced additives or structures is underway, only to fail commercialization yet. Meanwhile, to evaluate the LMRO capacity characteristics, charge-discharge cycles need to be performed after a cell activation process, making capacity characteristic analysis time-consuming. Consequently, it is necessary not only to develop an analytical method for predicting the LMRO capacity characteristics but also to develop LMRO exhibiting further improved battery performance. DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM A task to be solved in the present invention provides a method for analyzing a positive electrode active material, capable of predicting LMRO capacity characteristics by using a slope obtained from data of a graph obtained from a process of high-temperature activation (45 °C, 0.1 C-rate) of a lithium secondary battery. In addition, the present invention provides a positive electrode active material in which the slope obtained from the data of a graph obtained through the method for analyzing a positive electrode active material satisfies a specific range. In addition, the present invention provides a positive electrode and a lithium secondary battery which include the positive electrode active material. TECHNICAL SOLUTION In order to address the tasks described above, the present invention provides a method for analyzing a positive electrode active material, a positive electrode active material, and a positive electrode and a lithium secondary battery which include the same. (1) The present invention provides a method for analyzing a positive electrode active material, including (S1) preparing a positive electrode active material including a lithium-rich manganese oxide having a layered structure including both a Li2MnO3 phase and a LiMO2 phase (where M is an element including at least one selected from Ni and Mn), and manufacturing a lithium secondary battery including a positive electrode including a positive electrode active material layer including the positive electrode active material in an amount of at least 80 wt% with respect to a total weight of the positive electrode active material layer, (S2) obtaining a specific capacity-voltage graph (X-axis: specific capacity (mAh/g), Y-axis: voltage (V)) obtained by activating the lithium secondary battery at 45 °C with a 0.1 C-rate, and (S3) in the graph, applying linear fitting to data in a voltage range of 4.40 to 4.65 V to obtain a slope.(2) The present invention provides the method according to (1) above, wherein the lithium-rich manganese oxide exhibits a Li/Me (lithium (Li) to total metals excluding lithium (Me)) molar ratio of greater than 1.00 and 2.00 or less.(3) The present invention provides the method according to (1) or (2) above, wherein the lithium-rich manganese oxide exhibits a Li/Me (lithium (Li) to total metals excluding lithium (Me)) molar ratio of 1.24 to 1.36.(4) The present invention provides the method according to any one of (1) t