A negative electrode material, a preparation method thereof and a lithium ion battery negative electrode sheet

Abstract

The application provides a negative electrode material, a preparation method of the negative electrode material and a lithium ion battery negative electrode sheet, and the negative electrode material has high orientation. The preparation method of the negative electrode material comprises the following steps: (1) subjecting petroleum coke raw material to hydrothermal treatment, and then performing separation and drying to obtain material A; (2) performing first heat treatment on the material A obtained in the step (1), and obtaining material B after the treatment; and (3) performing second heat treatment on the material B obtained in the step (2), and obtaining the negative electrode material after the treatment. The negative electrode material has high orientation, the preparation method is simple and easy to implement, and the problem that the existing preparation of the negative electrode material with high orientation reduces the energy density of the battery is avoided.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a lithium battery anode material and its preparation method. Background Technology

[0002] Since their commercialization in the 1990s, lithium-ion batteries have revolutionized lifestyles and become one of the most outstanding technological inventions in human history. From portable electronic devices to electric vehicles, lithium-ion batteries dominate the energy storage market due to their high energy and power density, long cycle life, and reasonable cost. Graphite is widely used as the anode material in lithium-ion batteries because of its layered structure that facilitates lithium-ion intercalation, good dimensional stability, and low operating potential. Among graphite anode materials for lithium-ion batteries, artificial graphite anode materials occupy a dominant position.

[0003] Graphite orientation is a parameter describing the degree of ordered arrangement of graphite sheets in a graphite material. Highly oriented graphite materials typically exhibit better electrical conductivity and thermal stability, effectively improving the performance of lithium-ion batteries. To enhance the orientation of artificial graphite anode materials, additives can be introduced to improve the crystal structure and graphitization degree of the graphite anode; however, this also introduces inactive substances, reducing the battery's energy density. Therefore, the preparation of highly oriented artificial graphite anode materials is urgently needed to maximize electrochemical performance such as specific capacity.

[0004] Patent CN116005297A discloses a high-strength flexible graphene fiber and its preparation method. The method involves adding sodium alginate to graphene oxide to prepare a graphene oxide / sodium alginate nematic liquid crystal, which is then vacuum-filtered to form a film. Next, it is chemically cross-linked and fixed in a coagulation bath, followed by filtration. The film is then cut into strips of equal width, dry-wound, and reduced by immersion in a hydroiodic acid solution, thereby obtaining the high-strength flexible graphene fiber. This invention improves the electrical and mechanical properties of graphene fibers.

[0005] Patent CN110387601A discloses an ultra-strong and tough graphene fiber and its preparation method. The method involves preparing a graphene oxide spinning solution and a chitosan solution. One drop of the graphene oxide spinning solution is placed in a petri dish, and another drop of the chitosan solution is placed next to it. The two gripping parts of tweezers are inserted into the two droplets respectively, and then the two gripping parts are brought together to bring the graphene oxide spinning solution and chitosan solution into contact, forming a polyelectrolyte complex interface. The tweezers are then pulled upwards, and the graphene sheets and chitosan molecules spontaneously self-assemble into continuous fibers under the influence of intermolecular ionic and hydrogen bonds. The fibers are dried to obtain graphene oxide fibers, and finally reduced, washed, and dried to obtain graphene fibers. This invention uses a polyelectrolyte complex spinning process, and the traction and stretching effect helps the graphene and chitosan molecules to oriented assemblies, resulting in graphene fibers with high orientation, which is beneficial for the high strength and toughness of the fibers. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a negative electrode material, its preparation method, and a negative electrode sheet for lithium-ion batteries. In particular, it provides a negative electrode material prepared from petroleum coke as a raw material and its preparation method. The resulting negative electrode material has high orientation, and the preparation method is simple and easy to implement. This avoids the problem that existing methods for preparing highly oriented negative electrode materials require the introduction of additional additives, which leads to the introduction of impurities and reduces the energy density of the battery.

[0007] The first aspect of the present invention provides a negative electrode material, wherein the orientation of the negative electrode material is I height(002) / I height(110) =10~400, preferred I height(002) / I height(110) =20~200; I height(004) / I height(110) =0.5~20, preferred I height(004) / I height(110) =2~10; where, I height(002) It is the peak intensity of the (002) peak in the XRD spectrum of the negative electrode material, I height(004) It is the peak intensity of the (004) peak in the XRD spectrum of the negative electrode material, I height(110) It is the peak intensity of peak (110) in the XRD spectrum of the negative electrode material.

[0008] Furthermore, according to some specific embodiments of the present invention, the specific surface area of ​​the negative electrode material is 0.5–30 m². 2 / g.

[0009] Furthermore, according to some specific embodiments of the present invention, the negative electrode material I D / I G The ratio is 0.001 to 1.5, preferably 0.001 to 0.5; wherein I DThe Raman spectrum of the negative electrode material at 1350 cm⁻¹ -1 The peak intensity of the nearby D peak, I G The Raman spectrum of the negative electrode material at 1580 cm⁻¹ -1 Peak intensity of the nearby G peak.

[0010] Furthermore, according to some specific embodiments of the present invention, the degree of graphitization of the negative electrode material is 70-100%, preferably 92-100%.

[0011] Furthermore, according to some specific embodiments of the present invention, the interlayer spacing of the negative electrode material is 0.3354–0.3379 nm.

[0012] Furthermore, according to some specific embodiments of the present invention, the D of the negative electrode material 50 The particle size is 10–20 μm, preferably 10–15 μm.

[0013] A second aspect of the present invention provides a method for preparing a negative electrode material, the method comprising the following steps:

[0014] (1) Under closed conditions, the petroleum coke raw material is subjected to hydrothermal treatment, and then separated and dried to obtain material A;

[0015] (2) Perform a first heat treatment on material A obtained in step (1) to obtain material B;

[0016] (3) Perform a second heat treatment on material B obtained in step (2) to obtain a negative electrode material.

[0017] Furthermore, according to some specific embodiments of the present invention, the hydrothermal treatment temperature in step (1) is 100℃~240℃, the hydrothermal treatment pressure is 1MPa~10MPa, preferably 2MPa~5MPa, and the treatment time is 0.1~10h. The applicant has found that treating petroleum coke raw materials under hydrothermal conditions can promote the removal of impurities and promote the pre-growth of petroleum coke crystal structure, providing support for improving the orientation of the anode material in the future.

[0018] Furthermore, according to some specific embodiments of the present invention, the separation in step (1) can be performed by filtering.

[0019] Furthermore, according to some specific embodiments of the present invention, the purpose of drying in step (1) is to remove the water remaining on the surface of the petroleum coke during the hydrothermal treatment process. In the preferred case, vacuum drying is used, with a drying temperature of 50 to 100°C and a drying time of 0.5 to 100 h.

[0020] Furthermore, according to some specific embodiments of the present invention, the D of the petroleum coke feedstock in step (1) 50 The particle size is controlled within 10–20 μm, preferably 10–15 μm. Specifically, the particle size of the petroleum coke raw material can be controlled by methods such as air jet milling and mechanical milling.

[0021] Furthermore, according to some specific embodiments of the present invention, the petroleum coke raw material in step (1) is preferably pretreated by contacting a solvent before hydrothermal treatment (the mass ratio of petroleum coke raw material to solvent is 1:50 to 5:1), the solvent is water and / or alcohol, preferably water and alcohol, wherein the alcohol is at least one of ethanol and propanol; wherein the volume ratio of water and alcohol is 1:10 to 10:1; the pretreatment is preferably carried out under ultrasonic conditions, and the ultrasonic cleaning process lasts for 1 to 100 hours.

[0022] Furthermore, according to some specific embodiments of the present invention, the first heat treatment temperature in step (2) is 1100-1600°C, preferably 1200-1400°C, and the first heat treatment time is 1-10h.

[0023] Furthermore, according to some specific embodiments of the present invention, the first heat treatment in step (2) is carried out under an inert atmosphere protection condition, wherein the inert atmosphere can be nitrogen and / or an inert gas, wherein the inert gas can be at least one of helium, neon, argon, krypton, and xenon.

[0024] Furthermore, according to some specific embodiments of the present invention, the second heat treatment temperature in step (3) is 2500-3200°C, preferably 2900-3100°C, and the second heat treatment time is 1-10h.

[0025] Furthermore, according to some specific embodiments of the present invention, the second heat treatment in step (3) is carried out under an inert atmosphere protection condition, wherein the inert atmosphere can be nitrogen and / or an inert gas, wherein the inert gas can be at least one of helium, neon, argon, krypton, and xenon.

[0026] A third aspect of the present invention provides a negative electrode material obtained by the above preparation method.

[0027] The fourth aspect of the present invention provides a negative electrode sheet for a lithium-ion battery, wherein the active material of the negative electrode sheet is the negative electrode material described in the first aspect of the present invention and / or the negative electrode material obtained by the preparation method described in the second aspect.

[0028] Compared with the prior art, the negative electrode material and its preparation method provided by the present invention have one or more of the following technical effects:

[0029] 1. This invention provides a method for preparing negative electrode materials using petroleum coke as raw material, which provides a high-value utilization method for low-cost and widely available low-value petroleum coke, resulting in considerable economic benefits and providing technical support for production enterprises to reduce costs and increase efficiency.

[0030] 2. The negative electrode material provided by this invention has high orientation, and the lithium-ion battery assembled with it has high coulombic efficiency and charge / discharge specific capacity, excellent electrochemical performance, and broad application prospects.

[0031] 3. The method for preparing the negative electrode material provided in this aspect can improve the orientation of the negative electrode material without the use of additional additives, and at the same time avoids the introduction of other impurities into the negative electrode material. The active material content is high, which effectively solves the problem of reduced battery energy density caused by the introduction of additives. Attached Figure Description

[0032] Figure 1 This is an X-ray diffraction pattern of the negative electrode material prepared in Example 1 of the present invention.

[0033] Figure 2 The image shows the Raman spectrum of the negative electrode material prepared in Example 1 of this invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention.

[0035] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0036] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0037] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0038] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0039] In the context of this invention, "substantially" means that deviations that are acceptable or considered reasonable to those skilled in the art are permitted, such as deviations within ±5%, ±2%, ±1%, ±0.5%, or ±0.1%.

[0040] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0041] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0042] In the context of this specification, the orientation of the negative electrode material was determined using the GB / T 24533-2019 method on a Panak X-ray powder diffractometer. The orientation described herein is I. height(002) / I height(110) and I height(004) / I height(110) Among them, I height(002) It is the peak intensity of the (002) peak in the XRD spectrum of the negative electrode material, I height(004) It is the peak intensity of the (004) peak in the XRD spectrum of the negative electrode material, I height(110) It is the peak intensity of peak (110) in the XRD spectrum of the negative electrode material.

[0043] In the context of this specification, the specific surface area of ​​the samples was obtained using nitrogen adsorption-desorption curves on a Micromeritics ASAP 2425 adsorption instrument at an operating temperature of -196°C (liquid nitrogen temperature). The samples were pretreated for dehydration at 300°C under nitrogen protection prior to testing. The specific surface area was calculated using the BET method.

[0044] In the context of this specification, the Raman analysis of the samples was performed using an HR-800 Raman spectrometer manufactured by HORIBA JobinYvon, France.

[0045] In the context of this specification, when assembling coin cells for electrochemical performance testing of the negative electrode material, the current collector of the negative electrode material is copper foil, the conductive agent is Super-P, the binder is SBR, and the thickener is CMC. The working electrode of the lithium-ion battery is prepared with a mass ratio of active material, conductive agent, binder, and thickener of 90:3:4:3. Lithium metal is used as the counter electrode and reference electrode. 1M LiPF6 EC / DMC (vol 1:1) is used as the electrolyte, and a Celgard 2400 porous polypropylene membrane is used as the separator. The CR 2032 type coin cell is assembled in an argon-filled glove box for electrochemical performance testing.

[0046] Example 1

[0047] Petroleum coke raw material (D) 50 A mixture of petroleum coke (particle size 11.5 μm) and a water-ethanol mixture (volume ratio 1:1) was ultrasonically treated for 30 min at a mass ratio of 1:10, followed by filtration and drying. The ultrasonically treated petroleum coke was then placed in a hydrothermal reactor for a hydrothermal reaction at 200℃ and 3 MPa for 2 h. After filtration and drying, a first heat treatment was performed under an argon atmosphere at 1300℃ for 2 h. A second heat treatment was then performed at 2900℃ for 2 h to obtain the anode material. The anode material was characterized by X-ray diffraction and Raman spectroscopy. The X-ray diffraction pattern of the anode material is shown below. Figure 1 As shown, the carbon interlayer spacing of the negative electrode material is 0.336 nm, the degree of graphitization is 92.5%, and the orientation is I. height(002) / I height(110) It is 27.8, orientation I height(004) / I height(110) The value is 2.6. The Raman spectrum of the negative electrode material is as follows: Figure 2 As shown, the intensity of the scattering peak is greater than I. D / I G The value was 0.02. The CR 2032 coin cell was assembled and its electrochemical performance was tested. The initial discharge specific capacity was 370.2 mAh / g, the initial charge specific capacity was 358.1 mAh / g, and the coulombic efficiency was 96.7%.

[0048] Example 2

[0049] Petroleum coke raw material (D) 50A mixture of petroleum coke (particle size 11.5 μm) and water / ethanol (volume ratio 1:1) was ultrasonically treated at a mass ratio of 1:10 for 30 min, followed by filtration and drying. The ultrasonically treated petroleum coke was then placed in a hydrothermal reactor for hydrothermal reaction at 240℃ and 3 MPa for 5 h. After filtration and drying, a first heat treatment was performed under an argon atmosphere at 1400℃ for 3 h; followed by a second heat treatment at 3000℃ for 3 h to obtain the anode material. The anode material was characterized by X-ray diffraction and Raman spectroscopy. The carbon interlayer spacing was 0.3359 nm, the graphitization degree was 94.2%, and the orientation was I. height(002) / I height(110) It is 65.8, orientation I height(004) / I height(110) The intensity is 6.9. The intensity of the Raman scattering peak is higher than that of I. D / I G The value was 0.01. The CR 2032 coin cell was assembled and its electrochemical performance was tested. The initial discharge specific capacity was 371.3 mAh / g, the initial charge specific capacity was 360.8 mAh / g, and the coulombic efficiency was 97.2%.

[0050] Example 3

[0051] Petroleum coke raw material (D) 50 A mixture of petroleum coke (particle size 11.5 μm) and water / ethanol (volume ratio 1:1) was ultrasonically treated at a mass ratio of 1:10 for 2 hours, followed by filtration and drying. The ultrasonically treated petroleum coke was then placed in a hydrothermal reactor for hydrothermal reaction at 240℃ and 5 MPa for 8 hours. After filtration and drying, a first heat treatment was performed under an argon atmosphere at 1400℃ for 8 hours. A second heat treatment was then performed at 3100℃ for 8 hours to obtain the anode material. The anode material was characterized by X-ray diffraction and Raman spectroscopy. The carbon interlayer spacing was 0.3356 nm, the graphitization degree was 97.7%, and the orientation was I. height(002) / I height(110) It is 180.6, orientation I height(004) / I height(110) The intensity of the Raman scattering peak is 9.2. D / I G The value was 0.001. The CR 2032 coin cell was assembled and its electrochemical performance was tested. The initial discharge specific capacity was 374.8 mAh / g, the initial charge specific capacity was 365.3 mAh / g, and the coulombic efficiency was 97.5%.

[0052] Comparative Example 1

[0053] The process is essentially the same as in Example 1, except that the petroleum coke feedstock was not subjected to hydrothermal treatment. The carbon interlayer spacing of the negative electrode material is 0.3362 nm, the degree of graphitization is 90.7%, and the orientation is I. height(002) / I height(110) It is 8, and the orientation is I. height(004) / I height(110) The intensity of the Raman scattering peak is 0.4. D / I G The 1-cell CR 2032 coin cell was assembled and its electrochemical performance was tested. The initial charge specific capacity was 338.9 mAh / g, and the coulombic efficiency was 87.6%.

[0054] Comparative Example 2

[0055] The process is essentially the same as in Example 1, except that a first heat treatment was not performed. The carbon interlayer spacing of the negative electrode material is 0.3363 nm, the degree of graphitization is 89.4%, and the orientation is I. height(002) / I height(110) It is 6.3, orientation I height(004) / I height(110) The intensity of the Raman scattering peak is 0.39. D / I G The specific capacity was 1.2. The cells were assembled into CR 2032 coin cells for electrochemical performance testing. The initial charge specific capacity was 323.2 mAh / g, and the coulombic efficiency was 84.2%.

[0056] Comparative Example 3

[0057] The process is essentially the same as in Example 1, except that the first heat treatment temperature is 900°C. The carbon interlayer spacing of the negative electrode material is 0.3361 nm, the degree of graphitization is 91.6%, and the orientation is I. height(002) / I height(110) It is 11.6, orientation I height(004) / I height(110) The intensity of the Raman scattering peak is 0.92. D / I G The specific capacity was 0.8. The cells were assembled into CR 2032 coin cells for electrochemical performance testing. The initial charge specific capacity was 344.6 mAh / g, and the coulombic efficiency was 89.2%.

[0058] Comparative Example 4

[0059] The process is essentially the same as in Example 1, except that the second heat treatment temperature is 2000℃. The carbon interlayer spacing of the negative electrode material is 0.3384 nm, the degree of graphitization is 65.1%, and the orientation is I. height(002) / I height(110) It is 5.2, orientation Iheight(004) / I height(110) The intensity of the Raman scattering peak is 0.31 compared to I. D / I G The specific capacity was 1.3. The cells were assembled into CR 2032 coin cells for electrochemical performance testing. The initial charge specific capacity was 265.2 mAh / g, and the coulombic efficiency was 74.7%.

[0060] Comparative Example 5

[0061] The process is essentially the same as in Example 1, except that the petroleum coke feedstock was not subjected to hydrothermal treatment, but rather to atmospheric pressure treatment using steam at a reaction temperature of 200°C. The carbon interlayer spacing of the negative electrode material is 0.3363 nm, the degree of graphitization is 89.5%, and the orientation is I. height(002) / I height(110) It is 9.7, orientation I height(004) / I height(110) The intensity of the Raman scattering peak is 0.43. D / I G The specific capacity was 0.9. The cells were assembled into CR 2032 coin cells for electrochemical performance testing. The initial charge specific capacity was 341.7 mAh / g, and the coulombic efficiency was 88.3%.

[0062] The embodiments described above are merely detailed descriptions of the technical solutions of the present invention, but the present invention is not limited to the above embodiments, that is, the present invention does not depend on the steps described in the above embodiments to be implemented. In summary, any improvements made to the present invention by those skilled in the art, as long as they do not depart from the content of the technical solutions of the present invention, and any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention, shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A negative electrode material, wherein the orientation of the negative electrode material is I height(002) / I height(110) =10~400; I height(004) / I height(110) =0.5~20; where, I height(002) It is the peak intensity of the (002) peak in the XRD spectrum of the negative electrode material, I height(004) It is the peak intensity of peak (004) in the XRD spectrum of the negative electrode material, I height(110) It is the peak intensity of peak (110) in the XRD spectrum of the negative electrode material.

2. The negative electrode material according to claim 1, wherein, Orientation of negative electrode material I height(002) / I height(110) =20~200; I height(004) / I height(110) = 2~10; where, I height(002) It is the peak intensity of the (002) peak in the XRD spectrum of the negative electrode material, I height(004) It is the peak intensity of peak (004) in the XRD spectrum of the negative electrode material, I height(110) It is the peak intensity of peak (110) in the XRD spectrum of the negative electrode material.

3. The negative electrode material according to claim 1, wherein, The specific surface area of ​​the negative electrode material is 0.5–30 m². 2 / g.

4. The negative electrode material according to claim 1, wherein, I of negative electrode material D / I G The ratio is 0.001 to 1.5, preferably 0.001 to 0.5; wherein I D The Raman spectrum of the negative electrode material at 1350 cm⁻¹ -1 The peak intensity of the nearby D peak, I G The Raman spectrum of the negative electrode material at 1580 cm⁻¹ -1 Peak intensity of the nearby G peak.

5. The negative electrode material according to claim 1, wherein, The graphitization degree of the negative electrode material is 70-100%, preferably 92-100%.

6. The negative electrode material according to claim 1, wherein, The interlayer spacing of the negative electrode material is 0.3354–0.3379 nm.

7. The negative electrode material according to claim 1, wherein, D of negative electrode material 50 The particle size is 10~20 μm, preferably 10~15 μm.

8. A method for preparing a negative electrode material, the method comprising the following steps: (1) Under closed conditions, the petroleum coke raw material is subjected to hydrothermal treatment, and then separated and dried to obtain material A; (2) Perform a first heat treatment on material A obtained in step (1) to obtain material B; (3) Perform a second heat treatment on material B obtained in step (2) to obtain a negative electrode material.

9. The method for preparing the negative electrode material according to claim 8, wherein, The hydrothermal treatment temperature in step (1) is 100℃~240℃, the hydrothermal treatment pressure is 1 MPa~10 MPa, preferably 2 MPa~5 MPa, and the treatment time is 0.1~10h.

10. The method for preparing the negative electrode material according to claim 8, wherein, The purpose of drying in step (1) is to remove the water remaining on the surface of the petroleum coke during the hydrothermal treatment. In the preferred case, vacuum drying is used, with a drying temperature of 50 to 100 °C and a drying time of 0.5 to 100 h.

11. The method for preparing the negative electrode material according to claim 8, wherein, The D of the petroleum coke feedstock in step (1) 50 The particle size is controlled at 10~20 μm, preferably 10~15 μm.

12. The method for preparing the negative electrode material according to claim 8, wherein, In step (1), the petroleum coke raw material is pretreated by contacting a solvent before hydrothermal treatment. The solvent is water and / or alcohol, wherein the alcohol is at least one of ethanol and propanol. The pretreatment is preferably carried out under ultrasonic conditions.

13. The method for preparing the negative electrode material according to claim 8, wherein, The first heat treatment temperature in step (2) is 1100-1600 ℃, preferably 1200-1400 ℃, and the first heat treatment time is 1-10 h.

14. The method for preparing the negative electrode material according to claim 8, wherein, The first heat treatment in step (2) is carried out under an inert atmosphere, wherein the inert atmosphere is nitrogen and / or an inert gas, wherein the inert gas is at least one of helium, neon, argon, krypton and xenon.

15. The method for preparing the negative electrode material according to claim 8, wherein, The second heat treatment temperature in step (3) is 2500-3200℃, preferably 2900-3100℃, and the second heat treatment time is 1-10 h.

16. The method for preparing the negative electrode material according to claim 8, wherein, The second heat treatment in step (3) is carried out under an inert atmosphere, wherein the inert atmosphere is nitrogen and / or an inert gas, wherein the inert gas is at least one of helium, neon, argon, krypton, and xenon.

17. A negative electrode material obtained by the preparation method according to any one of claims 8-16.

18. A negative electrode sheet for a lithium-ion battery, wherein the active material of the negative electrode sheet is the negative electrode material according to any one of claims 1-7 and / or the negative electrode material obtained by the preparation method according to any one of claims 8-16.

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