CN-115579473-B - Lithium ion battery

Abstract

The invention provides a lithium ion battery, which comprises a positive electrode active material, wherein the positive electrode active material comprises lithium cobaltate particles doped with one or more elements of Al, mg, ti, zr, ni, mn, Y, la, sr, W, sc, the molar ratio of lithium element to cobalt element in the positive electrode active material is A under 0% of SOC, and the molar ratio of lithium element to cobalt element in the positive electrode active material is B under 100% of SOC, and A-B is more than or equal to 0.62 and less than or equal to 0.655. The lithium ion battery provided by the invention has better cycle performance under high voltage.

Inventors

• FAN YANAN
• Zeng Jiajiang
• YU LIQIU
• TONG ZHIQIANG
• LI SULI

Assignees

• 珠海冠宇电池股份有限公司

Dates

Publication Date

20260505

Application Date

20210621

Claims (8)

1. 1. The lithium ion battery is characterized by comprising a positive electrode active material, wherein the positive electrode active material comprises lithium cobaltate particles doped with Al, mg and Ti, the lithium cobaltate particles are doped with one or more elements of Zr, ni, mn, Y, la, sr, W, sc, the positive electrode active material further comprises a coating layer which is coated on at least part of the outer surface of the lithium cobaltate particles, the thickness of the coating layer is not more than 50nm, the average particle size of the positive electrode active material is 8.0-15.0 mu m, the positive electrode active material comprises Al element, the content of the Al element is not less than 3500ppm, the molar ratio of the lithium element to the cobalt element in the positive electrode active material is A under 0% SOC, the molar ratio of the lithium element to the cobalt element in the positive electrode active material is B under 100% SOC, and the molar ratio of the lithium element to the cobalt element in the positive electrode active material is B under 0.62-B0.655; the lithium ion battery further comprises a negative electrode active material, wherein the negative electrode active material comprises artificial graphite, and the negative electrode active material further comprises one or more of natural graphite, hard carbon, mesophase carbon microspheres, lithium titanate, silicon carbon and silicon oxide, and the artificial graphite is formed by mixing secondary particles with single particles.
2. 2. The lithium ion battery of claim 1, wherein the coating comprises one or more of a metal fluoride, a metal oxide, a metal borate compound, a metal phosphate compound.
3. 3. The lithium ion battery of claim 2, wherein the metal fluoride is selected from one or more of AlF 3 、Li 3 F, mgF; And/or the metal oxide is selected from one or more of Al 2 O 3 、TiO 2 、ZrO 2 and MgO; and/or, the metal borate compound is AlBO 3 ; and/or the metal phosphate compound is selected from one or two of AlPO 4 、Li 3 PO 4 .
4. 4. The lithium ion battery according to claim 2, wherein the mass of the coating layer is not more than 1% of the total mass of the positive electrode active material.
5. 5. The lithium ion battery according to claim 2, wherein the positive electrode active material is prepared by a preparation method comprising: Doping the lithium cobaltate particles with M element, wherein the M element is one or more of Al, mg, ti, zr, ni, mn, Y, la, sr, W, sc; and coating one or more of metal fluoride, metal oxide, metal borate compound and metal phosphate compound on at least part of the surface of the lithium cobaltate particles doped with the M element to form a coating layer, so as to obtain the positive electrode active material.
6. 6. The lithium-ion battery of any of claims 1-5, wherein the charge cutoff voltage of the lithium-ion battery is less than 4.5V.
7. 7. The lithium ion battery of any of claims 1-5, wherein the charge cutoff current of the lithium ion battery is not less than 0.02C.
8. 8. The lithium-ion battery of any of claims 1-5, wherein the charge-discharge temperature of the lithium-ion battery is less than 45 ℃.

Description

Lithium ion battery Technical Field The invention relates to a lithium ion battery, and relates to the technical field of secondary batteries. Background Since commercialization, lithium ion batteries have been widely used in the digital fields of notebooks, mobile phones, and the like due to their high specific energy and good cycle performance. However, along with the continuous increase of the demands of human beings on electronic equipment, higher demands are also put forward on the energy density of the lithium ion battery, and the energy density of the lithium ion battery has a great relationship with the volume, the discharge voltage platform and the discharge capacity of the lithium ion battery, so that the improvement of the discharge voltage platform of the lithium ion battery becomes one of effective means for improving the energy density. However, when the lithium ion battery is charged to 4.2V or more, lithium ions in the positive active material LiCoO 2 are extracted and form Li 1-xCoO2 (0 is less than or equal to 0.5) and when the charging voltage is increased to 4.4V or more, more lithium ions are extracted from the positive active material, the extracted lithium ion LiCoO 2 is also continuously transformed from a hexagonal system to a monoclinic system, the transformed monoclinic system LiCoO 2 does not have reversible lithium ion extracting capability any more, and meanwhile, when the charging voltage of the lithium ion battery reaches 4.4V or more, the side reaction between the positive active material and the electrolyte is also gradually increased, so as to continuously increase the charging voltage, the reversible capacity of the positive active material is continuously reduced, the cycle performance of the lithium ion battery is deteriorated, the application of the lithium ion battery is limited, the reversible capacity of the positive active material lithium cobaltate used commercially is far less than one of the theoretical capacities (274 h/g) of the lithium ion battery, and the technical problem of how to be solved in the field of improving the cycle performance of the lithium ion battery is solved. Disclosure of Invention The invention provides a lithium ion battery which is used for improving the cycle performance of the lithium ion battery under high voltage. The invention provides a lithium ion battery, which comprises a positive electrode active material, wherein the positive electrode active material comprises lithium cobaltate particles doped with one or more elements of Al, mg, ti, zr, ni, mn, Y, la, sr, W, sc, the molar ratio of lithium element to cobalt element in the positive electrode active material is A under 0% of SOC, and the molar ratio of lithium element to cobalt element in the positive electrode active material is B under 100% of SOC, and A-B is more than or equal to 0.62 and less than or equal to 0.655. The invention provides a lithium ion battery, which comprises a positive electrode active material, wherein the positive electrode active material comprises lithium cobaltate particles doped with one or more elements in Al, mg, ti, zr, ni, mn, Y, la, sr, W, sc, the element doping of the lithium cobaltate particles is beneficial to improving the structural stability of the positive electrode active material, meanwhile, the structural stability of the positive electrode active material is also influenced by a charge-discharge system, when the lithium ion battery comprising the positive electrode active material is charged and discharged by using a certain charge-discharge system, the molar ratio of lithium element to cobalt element in the positive electrode active material is marked as A under 0% SOC, the molar ratio of lithium element to cobalt element in the positive electrode active material is marked as B under 100% SOC, when the molar ratio of the lithium element to the cobalt element in the positive electrode active material is less than or equal to 0.655, the positive electrode active material has better structural stability under the charge-discharge system, the lithium ion battery comprising the positive electrode active material has better cycle performance, otherwise the cycle performance of the lithium ion battery cannot meet the use requirement, and the corresponding charge-discharge voltage of the positive electrode active material is required to be adjusted to be less than or equal to 0.655 to or less than 0.62V. In summary, the invention provides a lithium ion battery, when the molar ratio of lithium element to cobalt element in the positive electrode active material is A under 0% SOC, and when the molar ratio of lithium element to cobalt element in the positive electrode active material is B under 100% SOC, the molar ratio of lithium element to cobalt element in the positive electrode active material is 0.62-A-B-0.655, the lithium ion battery has better cycle performance under high voltage. In a specific embodiment, in order to improve structural