US-12620584-B2 - Negative electrode material, preparation method thereof, and lithium ion battery

US12620584B2US 12620584 B2US12620584 B2US 12620584B2US-12620584-B2

Abstract

The present disclosure relates to the field of negative electrode materials, and provides a negative electrode material and a preparation method therefor, and a lithium ion battery. The negative electrode material comprises an aggregate, the aggregate comprising an active substance and a carbon material. The mass percentage of the active substance in the aggregate gradually decreases from the center to the surface of the aggregate. The negative electrode material provided by the present disclosure can effectively suppress volume expansion of the negative electrode material and improve battery cycle performance.

Inventors

Chengmao XIAO
Peng He
Eming Guo
JIANGUO REN
Xueqin HE

Assignees

BTR NEW MATERIAL GROUP CO., LTD.
DINGYUAN NEW ENERGY TECHNOLOGY CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20220601
Priority Date: 20210630

Claims (7)

1 . A negative electrode material, comprising an aggregate, wherein the aggregate comprises a negative active material and a carbon material, wherein a mass percent content of the negative active material in the aggregate is gradually reduced from a center to a surface of the aggregate; a mass ratio of the negative active material to the carbon material is gradually reduced from the center to the surface of the aggregate; a maximum value of a mass ratio of the negative active material to the carbon material in the aggregate the is denoted as E, a minimum value thereof is denoted as F, wherein E−F≥0.5; and an EDS point scan test is performed on any region from an edge to a center of a SEM section of the aggregate with a spectrometer, a mass ratio of the negative active material to the carbon material is defined as T, and N tests are performed within the region, wherein N≥10, wherein A represents a minimum value of T in the results of the N tests, B represents a maximum value of T in the results of the N tests, a distance from any point of the surface to a center of the aggregate is L 0 μm, a distance of a center of a test region to the center of the aggregate is L 1 μm, a T value of the center position of the test region is defined as T 0 , wherein T 0 satisfies a relationship: T 0 ≤B−(B−A) L 1 /L 0 .
2 . The negative electrode material according to claim 1 , comprising at least one of the following features (1) to (4): (1) a total mass ratio of the negative active material to the carbon material is 0.5 to 8; (2) the negative active material has a mass percent content of 5% to 90%, based on 100% by mass of the aggregate; (3) the negative active material has a mass percent content of 5% to 80%, based on 100% by mass of the aggregate; (4) the negative active material has a mass percent content of 2% to 55% on the surface of the aggregate.
3 . The negative electrode material according to claim 1 , comprising at least one of the following features (1) to (6): (1) the negative active material comprises at least one of Li Na, K, Sn, Ge, Si, Sio x , Fe, Mg, Ti, Zn, Al, Ni, P, and Cu, wherein 0<x<2; (2) the negative active material has a median particle size ranging from 1 nm to 300 nm; (3) the carbon material comprises a graphite based carbon material and/or a non-graphite based carbon material; (4) the carbon material comprises a graphite based carbon material, and the graphite based carbon material comprises natural graphite and/or artificial graphite; (5) the carbon material comprises a graphite based carbon material, the graphite based carbon material comprises artificial graphite, and the artificial graphite comprises mesocarbon microbeads; (6) the carbon material comprises a non-graphite based carbon material, and the non-graphite based carbon material comprises at least one amorphous carbon, crystalline carbon, hard carbon, and soft carbon.
4 . The negative electrode material according to claim 1 , comprising at least one of the following features (1) to (12): (1) the aggregate further comprises at least one of a metal oxide and a conductive enhancer; (2) the aggregate further comprises a metal oxide, the metal oxide has a chemical formula of M x O y , wherein 0.2≤y/x≤3, and m comprises at least one of Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca, and Zn; (3) the aggregate further comprises a metal oxide, and the metal oxide is in a form of a sheet and/or a long strip; (4) the aggregate further comprises a metal oxide, and the metal oxide has an aspect ratio greater than 2; (5) the aggregate further comprises a conductive enhancer, and the conductivity enhancer has a conductivity of 10 0 s/m to 10 8 s/m; (6) the aggregate further comprises a conductive enhancer, and the conductive enhancer is in a form of a sheet and/or a long strip; (7) the aggregate further comprises a conductive enhancer, and the conductivity enhancer has an aspect ratio of 2 to 5000; (8) the aggregate further comprises a conductive enhancer, the conductive enhancer comprises at least one of an alloy material and a conductive carbon; (9) the aggregate further comprises a metal oxide, and a mass ratio of the metal oxide to the negative active material is 1 to 20:100; (10) the aggregate further comprises a conductive enhancer, and a mass ratio of the conductive enhancer to the negative active material ranges from 0.01 to 20:100; (11) the aggregate further comprises a conductive enhancer, and the conductive enhancer comprises an alloy material, and the alloy material comprises at least one of a zinc alloy, an aluminum alloy, a copper alloy, a silicon alloy, a nickel alloy, and a titanium alloy; (12) the aggregate further comprises a conductive enhancer, and the conductive enhancer comprises a conductive carbon, and the conductive carbon comprises one of graphite fibers, carbon nanotubes, graphite sheets, conductive carbon fibers, and graphene.
5 . The negative electrode material according to claim 1 , comprising at least one of the following features (1) to (8): (1) the negative electrode material further comprises a carbon layer coated on at least part of the surface of the aggregate; (2) the negative electrode material further comprises a carbon layer coated on at least part of the surface of the aggregate, and a material of the carbon layer comprises graphite and/or amorphous carbon; (3) the negative electrode material further comprises a carbon layer coated on at least part of the surface of the aggregate, and the carbon layer has a thickness of 10 nm to 2000 nm; (4) the negative electrode material has a median particle size of 0.5 μm to 30 μm; (5) the negative electrode material has a specific surface area of ≤10 m 2 /g; (6) the aggregate has a porosity of ≤10%; (7) the aggregate has a compressive hardness of ≥100 Mpa; (8) the aggregate density satisfies the following relationship: (ρ2−ρ1)/ρ2≤5%, wherein ρ1 is a test density of the aggregate, ρ2 is a theoretical density of the aggregate; and ρ2 is a sum of a value of multiplying a mass percent content of each component in the aggregate and a theoretical density of the each component.
6 . A negative electrode material, comprising an aggregate, wherein the aggregate comprises a negative active material and a carbon material, the carbon material is dispersed in the negative active material and based on 100% by mass of the aggregate, and a mass percent content of the negative active material on a surface of the aggregate is less than a mass percent content of the negative active material in the aggregate; a mass ratio of the negative active material to the carbon material is gradually reduced from the center to the surface of the aggregate; a maximum value of a mass ratio of the negative active material to the carbon material in the aggregate the is denoted as E, a minimum value thereof is denoted as F, wherein E−F≥0.5; and an EDS point scan test is performed on any region from an edge to a center of a SEM section of the aggregate with a spectrometer, a mass ratio of the negative active material to the carbon material is defined as T, and N tests are performed within the region, wherein N≥10, wherein A represents a minimum value of T in the results of the N tests, B represents a maximum value of T in the results of the N tests, a distance from any point of the surface to a center of the aggregate is L 0 μm, a distance of a center of a test region to the center of the aggregate is L 1 μm, a T value of the center position of the test region is defined as T 0 , wherein T 0 satisfies a relationship: T 0 ≤B−(B−A) L 1 /L 0 .
7 . A lithium ion battery, comprising the negative electrode material according to claim 1 .

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present application is a U.S. National Phase of International Application No. PCT/CN2022/096668 entitled “NEGATIVE ELECTRODE MATERIAL AND PREPARATION METHOD THEREFOR, AND LITHIUM ION BATTERY,” and filed on Jun. 1, 2022. International Application No. PCT/CN2022/096668 claims priority to Chinese Patent Application No. 202110736759.6 filed on Jun. 30, 2021. The entire contents of each of the above-listed applications are hereby incorporated by reference for all purposes. TECHNICAL FIELD The present disclosure relates to the field of negative electrode materials of the lithium ion battery, and the present disclosure relates to a negative electrode material a preparation method thereof, and a lithium ion battery. BACKGROUND Lithium ion batteries are widely used in electric vehicles and consumer electronics products due to advantages of high energy density, high output power, long cycle life, and less environmental pollution. To increase battery energy density, research and development on addition of active materials in negative electrode material, such as silicon negative electrode material is maturing over time. However, a volume of negative electrode material is greatly expanded after addition of the active material during lithium intercalation/deintercalatio, in particular the volume of the silicon negative electrode material may expand more than 300%, such that the material may be pulverized and fall off from the current collector during a charging and discharging process, and electrical connection broken between the negative active material and the current collector, resulting in poor electrochemical performance of the negative electrode material, such as capacity fading, decreased cycling stability, and leading to difficulty in commercial applications of such negative electrode material. Therefore, how to suppress the volumetric expansion of negative electrode material, improve the cycling stability of the negative electrode material is a problem that is now urgently to be solved. SUMMARY The present disclosure provides a negative electrode material including an aggregate, the aggregate includes an active material and a carbon material, the mass percent content of the active material in the aggregate is gradually reduced from a center to a surface of the aggregate. In the above technical solution, the negative electrode material includes an aggregate, and the aggregate include an active material and a carbon material, and the active material component located at the center of the aggregate core accounts for a major proportion of the aggregate, the carbon material component accounts for a minor proportion of the aggregate, while the proportion of the active material component away from the center of the core is gradually decreasing, and the proportion of the carbon material component the is increasing. The concentration change of the active material facilitates to enrich the active material at a center location of the negative electrode material in high concentration, therefore, the expansion of the active material can be controlled inside the aggregate, thereby avoiding disruption of to the carbon layer of the surface due to an expansion effect of the active material, increasing the stability of the SEI film on a surface of the negative electrode material, providing good interfacial stability, reducing a volume expansion rate of the negative electrode material having the added active material, and finally improving the cycle stability performance of the negative electrode material, and improving battery cycle performance. In some embodiments, a mass ratio of the active material to the carbon material is gradually reduced from the center to the surface of the aggregate. In some embodiments, a total mass ratio of the active material to the carbon material is from 0.5 to 8. In some embodiments, the active material has a mass percent content of 5% to 90%, based on 100% by mass of the aggregate. In some embodiments, the active material has a mass percent content of 5% to 80%, based on 100% by mass of the aggregate. In some embodiments, the active material has a mass percent content of 2% to 55% on the surface of the aggregate. In some embodiments, a maximum value of a mass ratio of the active material to the carbon material in the aggregate the is denoted as E, a minimum value thereof is denoted as F, wherein E−F≥0.5. In some embodiments, an EDS point scan test is performed on a SEM section of the aggregate from any region on the surface to the center with a spectrometer, a mass ratio of the active material to the carbon material is defined as T, and N tests are performed within the region, wherein N≥10. A represents a minimum value of T in the results of the N tests, B represents a maximum value of T in the results of the N tests, a distance from any point to a center of the surface of the aggregate is L0 μm, a distance of a center of a test region to the center of t