Graphite material and preparation method and application thereof

Abstract

The invention provides a graphite material, the graphite material is a spheroidic first particle, the first particle comprises a plurality of second particles for forming a porous structure, and pores extend from the surface of the first particle to the interior of the first particle; the average pore size of pores in the surfaces of the first particles is 2-5nm; the specific surface area of the first particles is 800-1300m < 2 > / g; the first particles have proper specific surface area due to the proper average pore size of the pores, so that the loading amount of lithium ions or sodium ions is ensured, and the collapse risk of the first particles is effectively reduced; the condition that the service life of the prepared battery is shortened due to the fact that the supporting force of the first particles is reduced due to overlarge specific surface area of the first particles is avoided; meanwhile, the situation that the specific surface area of the first particles is too small, the loading amount of lithium ions or sodium ions is reduced, and then the performance of the prepared battery is reduced is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite materials, and particularly to a graphite material, a preparation method thereof, and an application thereof. Background Art

[0002] The negative electrode materials of commercial lithium / sodium batteries have been widely studied and evaluated. The carbon materials for preparing the negative electrode materials include graphite, hard carbon, etc. Among them, graphite has always been the mainstream negative electrode material for lithium-ion batteries, which benefits from its excellent electrical conductivity, low lithium intercalation potential, high specific capacity, and mature mass production process, etc. The graphite negative electrode material requires a flaky structure with high purity and high crystallinity, and can be manufactured by natural graphite and artificial graphite. The preparation process of natural graphite involves complex grinding and classification techniques. In order to achieve a high purity level, additional purification processes are required, such as chemical or thermochemical treatment, etc. Natural graphite is a non-renewable resource and cannot be continuously mined. The preparation process of artificial graphite usually involves calcination (800 - 1200 °C) treatment for adjusting the size, shape, and morphology of particles and calcination (2500 - 3000 °C) for graphitization. According to the design requirements, mechanical refining (grinding, classification, carbon coating) is carried out on graphite particles. Although artificial graphite can be produced from various amorphous carbon precursors, such as petroleum coke, coal tar pitch, etc., high-temperature calcination is required in the preparation process of graphite, with high energy consumption, which greatly increases the cost of artificial graphite. Therefore, it is urgently needed for those skilled in the art to prepare a negative electrode material with low cost and good performance. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide a solution that can overcome or at least partially solve the above problems.

[0004] In the solution of the present invention, a graphite material is provided. The graphite material includes spherical-like first particles, and the first particles have a number of second particles for forming a multi-porous structure. The pores extend from the surface of the first particles towards the inside thereof; the average pore diameter of the pores on the surface of the first particles is 2 - 5 nm; the specific surface area of the first particles is 800 - 1300 m 2 / g.

[0005] In the present invention, the first particles are spherical-like. The spherical-like shape means that the shape of the particles is somewhat similar to a sphere to a certain extent, but not exactly a standard sphere. The surface has a curvature that is close but not exactly equal in all directions, with a slightly uneven surface, particles with an irregular shape but approximately circular, etc. The first particles have a number of pores extending from the surface towards the interior. The extending paths of the pores are winding and irregular. The pores provide sites for lithium ions or sodium ions to be incorporated. The pores on the surface of the first particles have a suitable average pore diameter, ensuring that the first particles have sufficient supporting force; avoiding the pore diameter of the pores being too large, which may cause the first particles to collapse; at the same time, avoiding the pores being too small, which may prevent lithium ions or sodium ions from being incorporated, thereby reducing the performance of the lithium-ion battery or sodium-ion battery. In addition, the suitable average pore diameter of the pores enables the first particles to have a suitable specific surface area to ensure the incorporation amount of lithium ions or sodium ions, effectively reducing the risk of collapse of the first particles; avoiding the specific surface area of the first particles being too large, reducing the supporting force of the first particles, and thereby reducing the service life of the battery prepared therefrom; at the same time, avoiding the specific surface area of the first particles being too small, reducing the incorporation amount of lithium ions or sodium ions, and thereby reducing the performance of the battery prepared therefrom.

[0006] Preferably, the average difference between the maximum pore diameter and the minimum pore diameter of the pores on the surface of the first particles is 0.6 - 1.2 nm.

[0007] In the present invention, the first particles have a suitable average difference between the maximum pore diameter and the minimum pore diameter of the pores on the surface, ensuring that the amount of lithium ions or sodium ions incorporated into the first particles is relatively uniform; if the pore diameters of the pores in the first particles differ too much, uneven internal incorporation amounts may occur after ion incorporation, easily leading to the phenomenon of the first particles cracking.

[0008] Preferably, the average particle diameter of the second particles is 150 - 300 nm.

[0009] In the present invention, the second particles are spherical-like and have a suitable average pore diameter, enabling them to always maintain the integrity of the structure of the first particles during the charging or discharging process of the battery; effectively avoiding, during the process of ion embedding, the pore walls breaking due to the ions filling the pores of the first particles and exerting a force on the pore walls, resulting in the loss of ion embedding sites and reducing the performance of the battery prepared from the first particles, while destroying the original structure of the first particles.

[0010] Preferably, the average difference between the maximum particle diameter and the minimum particle diameter of the second particles on the surface of the first particles is 50 - 100 nm.

[0011] In the present invention, the particle size of several second particles varies appropriately, avoiding the collapse of the first particles due to excessive difference in particle size between the second particles during the ion insertion and extraction processes, as well as the phenomenon of uneven ion loading inside and ion blockage in the deintercalation channels, effectively alleviating the volume expansion problem caused by ions during charge and discharge, and improving the stability and cycle life of the electrode material.

[0012] Preferably, the average particle size of the first particles is 3 - 10 μm.

[0013] In the present invention, the first particles have an appropriate average particle size, and thus have an appropriate specific surface area and ion loading capacity. Furthermore, the prepared negative electrode material has a large ion loading capacity, ensuring sufficient positions for ion insertion, avoiding the problem of capacity attenuation of the battery caused by ion channel blockage, and improving the stability and cycle life of the electrode material.

[0014] The preparation method of the above graphite material is as follows: S1: Ball-mill a biomass carbon source with a spherical particle template, a transition metal oxide, and deionized water to obtain a uniform mixture A, wherein the mass ratio of the biomass carbon source to the transition metal oxide material is 1:1 - 1:5, and the solid-liquid ratio is 0.1 - 0.5 kg / L;

[0015] S2: Calcinate the mixture A in an inert gas atmosphere to obtain substance B, wherein the calcination temperature is 350 - 850 °C, the calcination time is 0.5 - 4 h, and the flow rate of the inert gas is 1 - 10 L / min;

[0016] S3: Perform water leaching and filtration on substance B to obtain substance C; wherein the solid-liquid ratio of water leaching is 25 - 200 g / L, and the water leaching time is 0.5 - 4 h;

[0017] S4: Perform acid leaching and filtration on substance C to obtain substance D; wherein the acid concentration is 1 - 4 mol / L, and the acid leaching time is 1 - 6 h;

[0018] S5: Wash and dry substance D to obtain the graphite material described above.

[0019] In this application, a biomass carbon source with spherical particle templates, transition metal oxides, and deionized water are ball-milled in a ball mill. Among them, the mass ratio of the biomass carbon source to the transition metal oxide material is 1:1 - 1:5, and the solid-liquid ratio is 0.1 - 0.5 kg / L, so that the biomass carbon and the transition metal oxide are fully and evenly mixed to prepare first particles of appropriate size. By controlling the calcination temperature, time, and the flow rate of the inert gas, non-carbon atoms inside the biomass carbon source are detached from the inside of the biomass carbon source in the form of gas at high temperature, thereby forming a tortuous and irregular pore path, and the remaining carbon atoms form second particles in a spherical shape. Transition metals such as iron, cobalt, nickel, and their oxides can assist in catalyzing the graphitization process. Graphitization calcination requires a relatively high temperature. Therefore, the method of adding a transition metal catalyst can be used to improve the graphitization degree of the biomass carbon and reduce the carbonization temperature, improve the graphitization degree of the biomass carbon source, ensure the specific surface area and average pore diameter of the first particles, ensure the porosity of the first particles, and then ensure that the first particles have sufficient ion cavities, thereby improving the electrochemical performance of the battery.

[0020] Preferably, in step S1, the biomass carbon source is any one or more of kudzu powder, kudzu vine stem powder, and bagasse;

[0021] The transition metal oxide material includes one or more of nickel-rich layered oxides, lithium-rich manganese-based layered oxides, lithium nickel manganese spinel-type oxides, and lithium iron manganese spinel-type oxides.

[0022] In the present invention, kudzu powder, kudzu vine stem powder, and bagasse can provide spherical particle templates to ensure that they have a good spherical structure; the transition metal oxide material includes one or more of nickel-rich layered oxides, lithium-rich manganese-based layered oxides, lithium nickel manganese spinel-type oxides, and lithium iron manganese spinel-type oxides. The positive electrode materials of waste lithium / sodium batteries mainly include layered oxides, spinel-type oxides, etc. The transition metal oxides in this application are recovered from the positive electrode materials of waste batteries to realize the reuse of resources and reduce environmental pollution at the same time.

[0023] Preferably, in step S1, the mass ratio of the beads to the materials in the ball milling is 1:1 - 10:1, and the ball milling time is 1 - 12 h; in step S2, the inert gas is any one or two of argon and nitrogen.

[0024] In this application, before the biomass carbon source, the transition metal oxide, and the deionized water are ball-milled, beads need to be added to the ball mill tank. The mass ratio of the beads to the materials in the ball milling is 1:1 - 10:1, and the ball milling time is 1 - 12 h to ensure that the biomass carbon source and the transition metal oxide are evenly mixed and at the same time make the biomass carbon source have an appropriate size.

[0025] Preferably, in step S4, any one or both of hydrochloric acid and nitric acid are used for acid leaching; in step S5, the drying temperature is 120°C and the drying time is 12 h.

[0026] The above-mentioned graphite material is used to prepare the negative electrode material of a lithium-ion battery or a sodium-ion battery; this negative electrode material can be composed of first particles or can be composed of first particles and a carbon source with other structures.

[0027] Beneficial effects: By virtue of the inherent porous structure of biomass and in combination with the catalytic effect of waste transition metal oxides, the present invention prepares graphite particles with a porous structure. The particles have a sufficient specific surface area, and the pores have a suitable average pore diameter, increasing the active sites of the negative electrode material, improving the electrochemical performance, reusing the transition metal, and reducing the production cost of the graphite material.

[0028] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented in accordance with the content of the description. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are given below. Description of the Drawings

[0029] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0030] In the drawings:

[0031] Figure 1 is the SEM image of a first particle provided by the present application;

[0032] Figure 2 is the performance of a battery prepared from the negative electrode material composed of the first particles provided by the present application. Detailed Embodiments

[0033] The exemplary embodiments of the present invention will be described in more detail below with reference to the drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0034] Example 1

[0035] Put 5 g of kudzu vine stem powder and 10 g of waste lithium nickel cobalt manganese oxide (LiNi 0.3 Co 0.3 Mn0.3 (O2), 100 ml of industrial water, and 30 g of ball milling beads were added to a ball milling tank, and mechanically ball milled for 8 h to obtain a homogeneous mixture; the above mixture was transferred to an alumina crucible, and under an argon atmosphere with a gas flow rate of 1 L / min, it was heated to 750 °C at a rate of 5 °C / min and held at this temperature for 2 h; the heat-treated product obtained above was transferred to a stirring reaction kettle, 500 ml of industrial water was added, and stirred for 2 h to leach Li2CO3. The water-leached sample and 1 L of dilute hydrochloric acid (1 mol / L) were added to the stirring reaction kettle, stirred for 2 h, then filtered, washed, and dried at 120 °C for 12 h to obtain graphite.

[0036] Example 2

[0037] 5 g of kudzu starch, 10 g of waste lithium nickel cobalt manganese oxide (LiNi 0.3 Co 0.3 Mn 0.3 (O2), 100 ml of industrial water, and 30 g of ball milling beads were added to a ball milling tank, and mechanically ball milled for 8 h to obtain a homogeneous mixture; the above mixture was transferred to an alumina crucible, and under an argon atmosphere with a gas flow rate of 1 L / min, it was heated to 750 °C at a rate of 5 °C / min and held at this temperature for 2 h; the heat-treated product obtained above was transferred to a stirring reaction kettle, 500 ml of industrial water was added, and stirred for 2 h to leach Li2CO3. The water-leached sample and 1 L of dilute hydrochloric acid (1 mol / L) were added to the stirring reaction kettle, stirred for 2 h, then filtered, washed, and dried at 120 °C for 12 h to obtain graphite.

[0038] Comparative Example 1

[0039] 15 g of kudzu starch, 10 g of waste lithium nickel cobalt manganese oxide (LiNi 0.3 Co 0.3 Mn 0.3 (O2), 100 ml of industrial water, and 70 g of ball milling beads were added to a ball milling tank, and mechanically ball milled for 8 h to obtain a homogeneous mixture; the above mixture was transferred to an alumina crucible, and under an argon atmosphere with a gas flow rate of 1 L / min, it was heated to 500 °C at a rate of 9 °C / min and held at this temperature for 3 h; the heat-treated product obtained above was transferred to a stirring reaction kettle, 500 ml of industrial water was added, and stirred for 2 h to leach Li2CO3. The water-leached sample and 1 L of dilute hydrochloric acid (1 mol / L) were added to the stirring reaction kettle, stirred for 2 h, then filtered, washed, and dried at 190 °C for 12 h to obtain graphite.

[0040] The specific surface area of the first particles of the present application was measured by a specific surface area tester;

[0041] The average particle size of the first particles of the present application was measured by a particle size analyzer;

[0042] The pore sizes of the surface pores of the first particles and the particle sizes of the second particles of this application are both measured by a scanning electron microscope;

[0043] The specific capacity of the lithium-ion battery prepared in this application is obtained through testing by a Land battery testing system.

[0044] Table 1 Structural dimensions of each example

[0045]

[0046] Figure 1 is the structural diagram of the first particles prepared in Example 1. As can be seen from Figure 2 Among them, for the first particles of Example 1, Example 2, and Comparative Example 1 respectively, when they are made into negative electrode materials and the same positive electrode materials are used, lithium-ion batteries are prepared. It can be seen that the battery performances of Example 1 and Example 2 are far higher than that of Comparative Example 1, and Example 1 and Example 2 have good battery performances.

[0047] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0048] It is easy for those skilled in the art to think that any combination application of the above-mentioned various embodiments is feasible. Therefore, any combination among the above-mentioned various embodiments is an implementation scheme of the present invention. However, due to space limitations, this specification will not elaborate on each of them here.

[0049] In the specification provided here, a large number of specific details are described. However, it can be understood that the embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0050] Similarly, it should be understood that, in order to streamline the present invention and help understand one or more of the various aspects of the invention, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected by the claims, the aspects of the invention lie in less than all the features of the single embodiment disclosed above. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, where each claim itself serves as a separate embodiment of the present invention.

[0051] Those skilled in the art can understand that the modules in the devices in the embodiments can be adaptively changed and set in one or more devices different from the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and in addition, they can be divided into multiple sub-modules or sub-units or sub-components. Except that at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all the features disclosed in this specification (including the accompanying claims, abstract and drawings) and all the processes or units of any method or device so disclosed. Unless otherwise explicitly stated, each feature disclosed in this specification (including the accompanying claims, abstract and drawings) can be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0052] Although the preferred embodiments of the embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

[0053] Finally, it should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or terminal device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or terminal device comprising the element.

[0054] The above has introduced in detail a photovoltaic power generation system provided by the present invention. Specific examples are used in this article to illustrate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A graphite material, characterized in that, The graphite material includes spherical first particles, and the first particles have a number of second particles for forming a porous structure, and the pores extend from the surface of the first particles to the inside thereof; the average pore diameter of the pores on the surface of the first particles is 2-5 nm; the specific surface area of the first particles is 800-1300 m 2 / g.

2. The graphite material according to claim 1, characterized in that, The average difference between the maximum pore diameter and the minimum pore diameter of the pores on the surface of the first particles is 0.6 - 1.2 nm.

3. The graphite material according to claim 1, characterized in that, The average particle size of the second particles is 150 - 300 nm.

4. The graphite material according to claim 1, characterized in that, The average difference between the maximum particle size and the minimum particle size of the second particles on the surface of the first particles is 50 - 100 nm.

5. The graphite material according to claim 1, characterized in that, The average particle size of the first particles is 3 - 10 μm.

6. A method for preparing a graphite material according to any one of claims 1 - 5, characterized in that S1: Ball-mill a biomass carbon source with spherical particle templates, a transition metal oxide, and deionized water to obtain a uniform mixture A, wherein the mass ratio of the biomass carbon source to the transition metal oxide material is 1:1 - 1:5, and the solid-liquid ratio is 0.1 - 0.5 kg / L; S2: Calcinate the mixture A in an inert gas atmosphere to obtain a substance B, wherein the calcination temperature is 350 - 850 °C, the calcination time is 0.5 - 4 h, and the flow rate of the inert gas is 1 - 10 L / min; S3: Perform water leaching and filtration on the substance B to obtain a substance C; wherein the solid-liquid ratio of the water leaching is 25 - 200 g / L, and the water leaching time is 0.5 - 4 h; S4: Perform acid leaching and filtration on the substance C to obtain a substance D; wherein the acid concentration is 1 - 4 mol / L, and the acid leaching time is 1 - 6 h; S5: Wash and dry the substance D to obtain the graphite material.

7. The preparation method of the graphite material according to claim 6, characterized in that, In step S1, The biomass carbon source is any one or several of kudzu starch, kudzu vine stem powder, and bagasse; The transition metal oxide material includes one or more of nickel-rich layered oxides, lithium-rich manganese-based layered oxides, lithium nickel manganese spinel oxides, and lithium iron manganese spinel oxides.

8. The preparation method of the graphite material according to claim 6, wherein In step S1, the mass ratio of the beads to the material in the ball-milling is 1:1 - 10:1, and the ball-milling time is 1 - 12 h. In step S2, the inert gas is any one or two of argon and nitrogen.

9. The preparation method of the graphite material according to claim 6, characterized in that, In step S4, the acid leaching uses any one or two of hydrochloric acid and nitric acid; in step S5, the drying temperature is 120 °C, and the drying time is 12 h.

10. Use of the graphite material according to any one of claims 1-5, characterized in that, The graphite material is used for preparing the negative electrode material of a lithium-ion battery or a sodium-ion battery.

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