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US-20260128307-A1 - POSITIVE ELECTRODE MATERIAL AND PREPARATION METHOD THEREOF, AND LITHIUM-ION BATTERY

US20260128307A1US 20260128307 A1US20260128307 A1US 20260128307A1US-20260128307-A1

Abstract

A positive electrode material and a preparation method thereof, and a lithium-ion battery. The positive electrode material includes: a core layer including Li, Fe, Mn, PO 4 − ions, and doping element A; a shell layer, where at least a surface portion of the shell layer is coated on an outer surface of the core layer and the shell layer includes a first carbon particle and a second carbon particle; where the doping element A includes at least one element of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y; a distance difference between the highest point and the lowest point in a single surface of the positive electrode material is not more than 1 nm, and the surface roughness of the positive electrode material is 0.8 μm to 1.6 μm.

Inventors

  • Huaiyuan TIAN
  • Haiyang Chen
  • Yi Liu
  • Yusheng Wang
  • Xufeng YAN
  • Xueying Wang

Assignees

  • NINGBO RONBAY NEW ENERGY TECHNOLOGY Co.,Ltd.

Dates

Publication Date
20260507
Application Date
20251218
Priority Date
20231016

Claims (20)

  1. 1 . A positive electrode material, comprising: a core layer comprising Li, Fe, Mn, PO 4 − ions, doping element A; a shell layer, wherein at least a surface portion of the shell layer is coated on an outer surface of the core layer, and the shell layer comprises a first carbon particle and a second carbon particle; wherein the doping element A comprises at least one element of A1, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y; a distance difference between a highest point and a lowest point in a single surface of the positive electrode material is not more than 1 nm, and a surface roughness of the positive electrode material is 0.8 μm to 1.6 μm.
  2. 2 . The positive electrode material according to claim 1 , wherein an average diameter of the first carbon particle is 1 μm to 5 μm.
  3. 3 . The positive electrode material according to claim 1 , wherein an average diameter of the second carbon particle is 0.5 μm to 1 μm.
  4. 4 . The positive electrode material according to claim 1 , wherein the positive electrode material has a composition as shown in formula (I): wherein, value ranges of a, x, y, and b are respectively as follows: −0.1≤a≤0.4, 0.5≤x≤0.7, 0.005≤y≤0.05, 0<b≤0.3.
  5. 5 . The positive electrode material according to claim 1 , wherein a specific surface area of the positive electrode material is 10 m 2 /g to 25 m 2 /g.
  6. 6 . The positive electrode material according to claim 1 , wherein a diameter of the core layer is 200 nm to 400 nm.
  7. 7 . The positive electrode material according to claim 1 , wherein a thickness of the shell layer is 1 nm to 5 nm.
  8. 8 . The positive electrode material according to claim 1 , wherein a lightness of the positive electrode material is 0 to 25.
  9. 9 . The positive electrode material according to claim 1 , wherein a chroma of the positive electrode material is 0 to 3.6.
  10. 10 . The positive electrode material according to claim 1 , wherein the positive electrode material has a first discharge specific capacity of not less than 160 mAh/g at 0.1 C within a range of 2.0 V to 4.3 V.
  11. 11 . The positive electrode material according to claim 1 , wherein a volumetric specific energy density of the positive electrode material is not less than 80 mAh/cm 3 .
  12. 12 . The positive electrode material according to claim 1 , wherein a cycle retention rate of 200 cycles of the positive electrode material reaches 95.62%.
  13. 13 . A preparation method for a positive electrode material, wherein the preparation method comprises the following steps: S100: mixing a Li source, a Mn source, a Fe source, a P source, and a dopant containing a doping element A, sequentially performing a preheating treatment, a pulverization treatment, and a drying treatment, and performing a primary sintering treatment under a reducing atmosphere to obtain a first positive electrode material; S200: subjecting the first positive electrode material and a first carbon particle to a secondary sintering treatment under the reducing atmosphere to obtain a second positive electrode material; S300: adding the second positive electrode material, a second carbon particle and a binder in sequence for premixing treatment, and then performing a tertiary sintering treatment under the reducing atmosphere to obtain the positive electrode material; wherein the first carbon particle has an average diameter of 1 μm to 5 μm; the second carbon particle has an average diameter of 0.5 μm to 1 μm.
  14. 14 . The preparation method according to claim 13 , wherein in S100, a molar ratio of the Li source, the Mn source+the Fe source, the P source, and the dopant is (1.01-1.04):(0.98-1):1:(0.05-0.1).
  15. 15 . The preparation method according to claim 13 , wherein in S200, a molar ratio of the first positive electrode material to the first carbon particle is 100:(0.5-1); wherein in S300, a molar ratio of the second positive electrode material, the second carbon particle and the binder is 100:(0.5-0.8):(0.2-0.5).
  16. 16 . The preparation method according to claim 13 , wherein in S100: the pulverization treatment is sequentially performed by ball milling treatment and sand milling treatment; wherein, when a median particle size of a mixed material for the ball milling treatment is not more than 1 μm, the mixed material is transferred to the sand milling treatment; a medium for the ball milling treatment has a diameter of not more than 0.8 μm; wherein in S100: a medium of the sand milling treatment has a diameter of not more than 0.3 μm.
  17. 17 . The preparation method according to claim 13 , wherein in S100, a median particle size of a particulate matter after the pulverization treatment is not more than 6 μm; wherein in S100, a median particle size of a particulate matter after the drying treatment is not more than 4 μm; wherein in S200, the first carbon particle has an average particle size of 1 μm to 5 μm; wherein in S200, a powder compaction density of the first carbon particle at 2 T pressure is 3.00 g/cm 3 to 3.20 g/cm 3 .
  18. 18 . The preparation method according to claim 13 , wherein in S300, the binder comprises any one of polyvinylidene fluoride, polyamide, polyimide, polyacrylic acid, polyvinyl alcohol, and styrene butadiene rubber, or a combination of two or more thereof.
  19. 19 . The preparation method according to claim 13 , wherein in S100, a temperature of the preheating treatment is 120° C. to 180° C.; in S100, a time of the preheating treatment is 0.1 h to 1 h; in S100, a temperature of the primary sintering treatment is 500° C. to 650° C.; in S100, a time of the primary sintering treatment is 8 h to 12 h; in S200, a temperature of the secondary sintering treatment is 600° C. to 700° C.; in S200, a time of the secondary sintering treatment is 6 h to 10 h; in S300, a time of the premixing treatment is 1 h to 1.5 h; in S300, a temperature of the tertiary sintering treatment is 650° C. to 750° C.; in S300, a time of the tertiary sintering treatment is 6 h to 10 h.
  20. 20 . A lithium-ion battery, comprising the positive electrode material according to claim 1 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Application No. PCT/CN2023/142530, filed on Dec. 27, 2023, which claims priority to a Chinese patent application No. 202311329054.8, filed on Oct. 16, 2023, both of which are hereby incorporated by reference in their entireties. TECHNICAL FIELD The present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode active material and a preparation method thereof and a lithium-ion battery. BACKGROUND With the booming development of electronic products today, there is an increasing demand for portable and reusable secondary batteries. Among the existing secondary battery types, olivine-type positive electrode material has significant potential for application in power lithium-ion batteries due to its numerous advantages. However, the inherent drawbacks of olivine-structured phosphate compounds themselves, such as low electronic conductivity and slow one-dimensional lithium-ion diffusion rates, severely affect the exertion of electrochemical performance of lithium iron manganese phosphate materials, hindering their further large-scale application. To enhance energy density, the proportion of manganese content is typically increased. However, as the manganese proportion rises, manganese leaching inevitably occurs during material cycling. Currently, carbon coating is commonly used to reduce manganese leaching during material cycling, which not only improves cycling performance but also enhances the conductivity of the material. However, the existing carbon coating process based on solid-phase dry technology cannot uniformly coat a layer of carbon material onto the material surface. A non-uniform and uneven carbon coating not only fails to address manganese leaching issue but may even impair the material's electrical conductivity. SUMMARY The present application aims to solve at least one of the above-mentioned technical problems. Therefore, a first objective of the present application is to provide a positive electrode material. A second objective of the present application is to provide a preparation method for a positive electrode material. A third objective of the present application is to provide a lithium-ion battery. In order to achieve the first objective of the present application, the present application provides a positive electrode material including: a core layer including Li, Fe, Mn, PO4− ions, doping element A; a shell layer, where at least a surface portion of the shell layer is coated on an outer surface of the core layer and the shell layer includes a first carbon particle and a second carbon particle; where, the doping element A includes at least one element of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y; a distance difference between the highest point and the lowest point in a single surface of the positive electrode material is not more than 1 nm, and the surface roughness of the positive electrode material is 0.8 μm to 1.6 μm. Compared to the prior art, the technical effects achieved by this technical solution are as follows. The core layer includes Li, Fe, Mn, PO4− ions, and doping element A. By doping manganese into lithium iron phosphate to replace part of the Fe element, lithium manganese iron phosphate material is prepared, which can increase voltage, enhance energy density per unit mass, and offer good compatibility with the voltage of current lithium-ion batteries, thereby reducing the difficulty of mutual substitution. Furthermore, the doping element A includes at least one element of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y By doping element A into lithium iron phosphate, it not only coordinates the elements within the core layer but also modifies the positive electrode material, thereby enhancing the performance of the positive electrode material. The doping element A can result in Li-site or M-site defects in the lattice of manganese iron phosphate, creating vacancies or altering interatomic bond lengths in the lattice of material, which facilitates Li-ion movement in the lattice and can improve electrochemical performance. As for the shell layer, at least a surface portion of the shell layer is coated on an outer surface of the core layer, and the shell layer is composed of element C. As the proportion of manganese increases, manganese leaching will be inevitably occurred during the material's cycling process. Coating the surface of the core layer with carbon particles can reduce manganese leaching. However, it is currently impossible to uniformly coat the material surface with a layer of carbon material. An uneven and rough carbon coating not only fails to improve manganese leaching issue, but may even impair the conductivity of the material. The distance difference between the highest point and the lowest point in the single surface of the positive electrode material is not more than 1 nm, and the surface ro