Natural graphite composite negative electrode material and preparation method therefor, and lithium-ion battery

Abstract

A natural graphite composite negative electrode material and a preparation method therefor, and a lithium-ion battery. The natural graphite composite negative electrode material comprises natural graphite, a fluffy net-shaped three-dimensional carbon network that coats the natural graphite, and an amorphous carbon coating layer arranged outside the fluffy net-shaped three-dimensional carbon network, wherein magnesium ions and / or aluminum ions are dispersed in the fluffy net-shaped three-dimensional carbon network, and the amorphous carbon coating layer is doped with copper particles and / or silver particles. The natural graphite composite negative electrode material has a three-dimensional conductive network, is doped with metals, and has a good conductivity and electrochemical cycle performance.

Description

A natural graphite composite anode material, its preparation method, and a lithium-ion battery

[0001] This application claims priority to Chinese Patent Application No. 202411856618.8, filed on December 17, 2024, entitled "A Natural Graphite Composite Anode Material and Its Preparation Method and Lithium-ion Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a natural graphite composite anode material, its preparation method, and a lithium-ion battery, belonging to the field of materials technology, particularly electrode materials technology. Background Technology

[0003] Anode materials are a crucial component of lithium-ion batteries, playing a role in energy storage and release during battery cycling. Among them, graphite-based anode materials, which are currently widely used, generally suffer from numerous surface defects and solvent co-intercalation leading to structural collapse. Therefore, surface modification treatment is necessary to stabilize the material structure and improve performance.

[0004] For example, CN111354513A discloses a silver-doped polypyrrole-coated graphite composite material and its preparation method. This method uses silver nitrate as an oxidant to promote the in-situ polymerization of pyrrole monomers. Simultaneously, the silver nitrate is reduced to elemental silver and doped into the polypyrrole, resulting in a core-shell type silver-doped polypyrrole-coated graphite composite material, which effectively improves the material's conductivity. Although this preparation method meets environmental protection requirements, it suffers from uneven coating of silver-doped polypyrrole on the surface of natural spherical graphite, hindering the commercial application of natural graphite.

[0005] Therefore, providing a novel natural graphite composite anode material, its preparation method, and a lithium-ion battery has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned shortcomings and deficiencies, the present invention aims to provide a natural graphite composite anode material, its preparation method, and a lithium-ion battery. The natural graphite composite anode material provided by the present invention possesses a three-dimensional conductive network and is doped with metals, exhibiting good conductivity and excellent electrochemical cycling performance.

[0007] To achieve the above objectives, on the one hand, the present invention provides a natural graphite composite anode material, wherein the natural graphite composite anode material includes natural graphite, a loose three-dimensional carbon network covering the natural graphite, and an amorphous carbon coating layer disposed outside the loose three-dimensional carbon network; wherein magnesium ions and / or aluminum ions are dispersed in the loose three-dimensional carbon network, and copper particles and / or silver particles are doped in the amorphous carbon coating layer.

[0008] In the natural graphite composite anode material described above in this invention, magnesium ions and / or aluminum ions are uniformly dispersed in the loose, three-dimensional carbon network, and copper particles and / or silver particles are uniformly doped in the amorphous carbon coating layer. Here, copper particles and silver particles refer to elemental copper and silver.

[0009] As a specific embodiment of the natural graphite composite negative electrode material described above in this invention, the natural graphite is natural spherical graphite, etc.

[0010] On the other hand, the present invention also provides a method for preparing the above-mentioned natural graphite composite anode material, wherein the preparation method includes:

[0011] Step (1): Disperse pyrrole monomer, copper nitrate and / or silver nitrate, magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate and sodium alginate evenly in a solvent to obtain pyrrole monomer solution, copper nitrate and / or silver nitrate solution, magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate solution and sodium alginate solution.

[0012] Step (2): Add natural graphite to the solution of magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate and mix them evenly. The system is acidic.

[0013] Step (3): Add sodium alginate solution to the mixture obtained in step (2), and under the conditions of stirring and acidity at 20-30℃ (preferably room temperature), magnesium ions and / or aluminum ions in the solution replace sodium ions in sodium alginate through a displacement reaction to form and precipitate a hydrogel of magnesium alginate and / or aluminum alginate.

[0014] Step (4): Add the solution of copper nitrate and / or silver nitrate to the mixture obtained in step (3) and mix them evenly;

[0015] Step (5): Add the pyrrole monomer solution to the mixture obtained in step (4), and carry out the reaction under stirring and constant temperature conditions. After the reaction is completed, the product is aged.

[0016] Step (6): The aged product is sequentially cleaned, filtered, dried and carbonized to obtain the natural graphite composite anode material.

[0017] In a specific embodiment of the preparation method described above in this invention, the mass ratio of natural graphite powder, pyrrole monomer, copper nitrate and / or silver nitrate, sodium alginate and magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate is 1000:5~80:30~100:0.00001~50:0.001~50.

[0018] As a specific embodiment of the preparation method described above in this invention, in step (1), the concentration of pyrrole monomer in the pyrrole monomer solution is 0.1-1.5 mol / L; the concentration of copper nitrate and / or silver nitrate in the copper nitrate and / or silver nitrate solution is 0.05-1.9 mol / L, preferably using only copper nitrate, more preferably using only copper nitrate, and more preferably using only aluminum trifluoromethanesulfonate ...

[0019] This invention does not impose specific requirements on the purity of raw materials such as copper nitrate and / or silver nitrate, pyrrole monomer, magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate, and sodium alginate used in the preparation methods described above; these can be selected reasonably as needed. Where possible, raw materials with higher purity should be selected. For example, in some embodiments of this invention, the purity of copper nitrate and silver nitrate is above 95%, the purity of pyrrole monomer is greater than 95%, the purity of magnesium trifluoromethanesulfonate and aluminum trifluoromethanesulfonate (both trifluoromethanesulfonates) is above 88%, and the purity of sodium alginate is above 90%.

[0020] As a specific embodiment of the preparation method described above in this invention, in step (1), the solvent includes deionized water and / or organic solvents, etc.

[0021] As a specific embodiment of the preparation method described above in this invention, in step (2), the pH value of the system is 1 to 5.

[0022] In steps (2) to (5) of the preparation method described above, uniform mixing can be achieved by stirring or other means, preferably by uniform stirring. In some embodiments of the present invention, the uniform stirring speed in steps (2), (3), (4) and (5) can be 200 to 1000 rpm; and the temperature of the stirring process can be reasonably adjusted as needed. For example, in some embodiments of the present invention, step (4) can be stirred at room temperature.

[0023] As a specific embodiment of the preparation method described above in this invention, in step (3), the displacement reaction time is 2 to 5 hours.

[0024] The insoluble substances precipitated in step (3) of the preparation method described above, namely the hydrogels of magnesium alginate and / or aluminum alginate, are then carbonized to form a fluffy three-dimensional carbon network covering the natural graphite; the polypyrrole formed by in-situ polymerization of pyrrole monomers in step (5) is then carbonized to form an amorphous carbon coating layer covering the fluffy three-dimensional carbon network.

[0025] As a specific embodiment of the preparation method described above in this invention, in step (5), the reaction temperature is from room temperature to 60°C, and the time is 2 to 5 hours.

[0026] And / or the aging process is carried out at room temperature to 60°C for no less than 12 hours.

[0027] In step (5) of the preparation method described above, the pyrrole monomer solution is added to the mixture obtained in step (4). Under the conditions of stirring, acidity of the system and constant temperature, the pyrrole monomer undergoes oxidative polymerization, accompanied by the reduction of copper ions and / or silver ions.

[0028] In step (6) of the preparation method described above, the cleaning is performed by washing with deionized water multiple times until the pH value of the cleaning solution is 6-7.

[0029] As a specific embodiment of the preparation method described above in this invention, in step (6), the drying is performed at 60-120°C for 12-24 hours;

[0030] And / or the carbonization treatment temperature is 800–1500°C.

[0031] Compared to the conventional solid-phase method for preparing the same type of natural graphite composite anode material, the liquid-phase method used in this invention can make the carbon coating layer on the surface of natural graphite more uniform, reduce the exposure of surface active sites, and result in fewer electrochemical side reactions when the natural graphite composite anode material is used in lithium-ion batteries.

[0032] In another aspect, the present invention also provides a lithium-ion battery, wherein the negative electrode material of the lithium-ion battery is the natural graphite composite negative electrode material described above.

[0033] Compared with the prior art, the beneficial technical effects achieved by the technical solution provided by the present invention include at least the following:

[0034] The natural graphite composite anode material provided by this invention includes natural graphite, a loose, three-dimensional carbon network coating the natural graphite, and an amorphous carbon coating layer disposed outside the loose, three-dimensional carbon network. The loose, three-dimensional carbon network contains dispersed magnesium ions and / or aluminum ions, and the amorphous carbon coating layer is doped with copper and / or silver metal particles. The loose, three-dimensional carbon network is formed by carbonization treatment of insoluble substances precipitated during the preparation process, namely magnesium alginate and / or aluminum alginate hydrogels. These insoluble substances are obtained by carbonization treatment of metal ions (Mg...). 2+ and / or Al 3+ The amorphous carbon coating layer is formed by replacing sodium ions in sodium alginate and then carbonizing polypyrrole formed by in-situ polymerization of pyrrole monomers.

[0035] The metals doped in natural graphite composite anode materials can improve the conductivity of natural graphite composite anode materials. When magnesium ions and / or aluminum ions are dispersed in the loose three-dimensional carbon network and copper and / or silver metal particles are doped in the amorphous carbon coating layer, a three-dimensional conductive network can be formed on the surface of natural graphite, which can improve conductivity and effectively increase the diffusion channels of lithium ions.

[0036] The fluffy (soft) three-dimensional carbon network in the natural graphite composite anode material can effectively alleviate the volume change of natural graphite during charging and discharging. The amorphous carbon coating layer can reduce the defect concentration on the surface of the composite electrode material and prevent the co-intercalation of solvent ions. The synergistic effect of the two can improve the structural stability of the natural graphite composite anode material, and can effectively improve the specific capacity and cycle life of the natural graphite composite anode material.

[0037] In summary, the natural graphite composite anode material provided by this invention has superior electrochemical cycling performance. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figures 1a and 1b are scanning electron microscope images of the natural spherical graphite composite anode material provided in Example 1 of the present invention, with Mag values ​​of 0.5K and 1.5K, respectively.

[0040] Figures 1c and 1d are scanning electron microscope images of the natural spherical graphite composite anode material provided in Example 2 of the present invention, with Mag values ​​of 0.5K and 1.5K, respectively.

[0041] Figures 1e and 1f are scanning electron microscope images of the natural spherical graphite composite anode material provided in Example 3 of the present invention, with Mag values ​​of 0.5K and 1.5K, respectively.

[0042] Figure 1g and Figure 1h are elemental distribution diagrams of the natural spherical graphite anode materials provided in Example 1 and Comparative Example 1 of the present invention, respectively.

[0043] Figure 2 is a 1C / 1C electrochemical performance cycle diagram of the natural spherical graphite anode materials provided in Examples 1-3 and Comparative Example 1 of the present invention. Detailed Implementation

[0044] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0045] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0046] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0047] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0048] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0049] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0051] Example 1

[0052] This embodiment provides a natural spherical graphite composite anode material, which is prepared by a method including the following specific steps:

[0053] Step (1): Disperse pyrrole monomer, copper nitrate, magnesium trifluoromethanesulfonate, and sodium alginate evenly in water to obtain pyrrole monomer solution, copper nitrate solution, magnesium trifluoromethanesulfonate solution, and sodium alginate solution. The concentration of pyrrole monomer in the pyrrole monomer solution is 0.1 mol / L, the concentration of copper nitrate in the copper nitrate solution is 0.1 mol / L, the concentration of magnesium trifluoromethanesulfonate in the magnesium trifluoromethanesulfonate solution is 0.005 mol / L, and the concentration of sodium alginate in the sodium alginate solution is 0.05 mol / L. Ensure that the mass ratio of natural graphite powder, pyrrole monomer, copper nitrate, sodium alginate, and magnesium trifluoromethanesulfonate is 1000:20:40:0.05:0.005.

[0054] Step (2): Add 1 kg of natural spherical graphite powder to the magnesium trifluoromethanesulfonate solution and stir at room temperature to mix it evenly, ensuring that the pH value of the system is 2.5;

[0055] Step (3): Add sodium alginate solution to the mixture obtained in step (3), and stir at a constant speed of 600 rpm at room temperature. Under acidic conditions, magnesium ions in the solution replace sodium ions in sodium alginate through a displacement reaction to form and precipitate insoluble substances, namely magnesium alginate hydrogel.

[0056] The displacement reaction can take 3 hours.

[0057] Step (4): Add copper nitrate solution to the mixture obtained in step (3) and stir at room temperature to make the system uniformly mixed;

[0058] Step (5): Add the pyrrole monomer solution to the mixture obtained in step (4). During the experiment, maintain the temperature at room temperature and stir at a speed of 600 rpm. Under these conditions, react for 2 hours. After the reaction is completed, age the product at 60℃ for 24 hours.

[0059] Step (6): The aged product is cleaned, filtered, dried and carbonized. The cleaning process uses deionized water to clean multiple times until the pH value of the final cleaning solution is 7. The product drying temperature is 80℃ and the time is 24 hours. The calcination temperature is 850℃. Finally, a black powder material is obtained, which is the natural spherical graphite composite negative electrode material.

[0060] Example 2

[0061] This embodiment provides a natural spherical graphite composite anode material, which is prepared by a method including the following specific steps:

[0062] Step (1): Disperse pyrrole monomer, copper nitrate, magnesium trifluoromethanesulfonate, and sodium alginate evenly in water to obtain pyrrole monomer solution, copper nitrate solution, magnesium trifluoromethanesulfonate solution, and sodium alginate solution. The concentration of pyrrole monomer in the pyrrole monomer solution is 0.1 mol / L, the concentration of copper nitrate in the copper nitrate solution is 0.1 mol / L, the concentration of magnesium trifluoromethanesulfonate in the magnesium trifluoromethanesulfonate solution is 0.005 mol / L, and the concentration of sodium alginate in the sodium alginate solution is 0.05 mol / L. Ensure that the mass ratio of natural graphite powder, pyrrole monomer, copper nitrate, sodium alginate, and magnesium trifluoromethanesulfonate is 1000:20:40:0.05:0.0034.

[0063] Step (2): Add 1 kg of natural spherical graphite powder to the magnesium trifluoromethanesulfonate solution and stir at room temperature to mix it evenly, ensuring that the pH value of the system is 4;

[0064] Step (3): Add sodium alginate solution to the mixture obtained in step (3), and stir at a constant speed of 600 rpm at room temperature. Under acidic conditions, magnesium ions in the solution replace sodium ions in sodium alginate through a displacement reaction to form and precipitate insoluble substances, namely magnesium alginate hydrogel.

[0065] The displacement reaction can take 3 hours.

[0066] Step (4): Add copper nitrate solution to the mixture obtained in step (3) and stir at room temperature to make the system uniformly mixed;

[0067] Step (5): Add the pyrrole monomer solution to the mixture obtained in step (4). During the experiment, maintain the temperature at room temperature and stir at a speed of 600 rpm. Under these conditions, react for 2 hours. After the reaction is completed, age the product at 60℃ for 24 hours.

[0068] Step (6): The aged product is cleaned, filtered, dried and carbonized. The cleaning process uses deionized water to clean multiple times until the pH value of the final cleaning solution is 7. The product drying temperature is 80℃ and the time is 24 hours. The calcination temperature is 850℃. Finally, a black powder material is obtained, which is the natural spherical graphite composite negative electrode material.

[0069] Example 3

[0070] This embodiment provides a natural spherical graphite composite anode material, which is prepared by a method including the following specific steps:

[0071] Step (1): Disperse pyrrole monomer, copper nitrate, aluminum trifluoromethanesulfonate, and sodium alginate evenly in water to obtain pyrrole monomer solution, copper nitrate solution, aluminum trifluoromethanesulfonate solution, and sodium alginate solution. The concentration of pyrrole monomer in the pyrrole monomer solution is 0.1 mol / L, the concentration of copper nitrate in the copper nitrate solution is 0.1 mol / L, the concentration of aluminum trifluoromethanesulfonate in the aluminum trifluoromethanesulfonate solution is 0.005 mol / L, and the concentration of sodium alginate in the sodium alginate solution is 0.05 mol / L. Ensure that the mass ratio of natural graphite powder, pyrrole monomer, copper nitrate, sodium alginate, and aluminum trifluoromethanesulfonate is 1000:20:40:0.05:0.0033.

[0072] Step (2): Add 1 kg of natural spherical graphite powder to the aluminum trifluoromethanesulfonate solution and stir at room temperature to mix it evenly, ensuring that the pH value of the system is 2.5;

[0073] Step (3): Add sodium alginate solution to the mixture obtained in step (3), and stir at a constant speed of 600 rpm at room temperature. Under acidic conditions, aluminum ions in the solution replace sodium ions in sodium alginate through a displacement reaction to form and precipitate insoluble substances, namely aluminum alginate hydrogel.

[0074] The displacement reaction can take 3 hours.

[0075] Step (4): Add copper nitrate solution to the mixture obtained in step (3) and stir at room temperature to make the system uniformly mixed;

[0076] Step (5): Add the pyrrole monomer solution to the mixture obtained in step (4). During the experiment, maintain the temperature at room temperature and stir at a speed of 600 rpm. Under these conditions, react for 2 hours. After the reaction is completed, age the product at 60℃ for 24 hours.

[0077] Step (6): The aged product is cleaned, filtered, dried and carbonized. The cleaning process uses deionized water to clean multiple times until the pH value of the final cleaning solution is 7. The product drying temperature is 80℃ and the time is 24 hours. The calcination temperature is 850℃. Finally, a black powder material is obtained, which is the natural spherical graphite composite negative electrode material.

[0078] Comparative Example 1

[0079] This comparative example provides a natural spherical graphite composite anode material. The difference between this and Example 1 lies solely in that this comparative example does not use metal ion-substituted doped alginate hydrogel to coat the natural spherical graphite anode material. This natural spherical graphite composite anode material is prepared using a method comprising the following specific steps:

[0080] Step (1): Disperse pyrrole monomer, copper nitrate and magnesium trifluoromethanesulfonate evenly in water to obtain pyrrole monomer solution, copper nitrate solution and magnesium trifluoromethanesulfonate solution. The concentration of pyrrole monomer in the pyrrole monomer solution is 0.1 mol / L, the concentration of copper nitrate in the copper nitrate solution is 0.1 mol / L, and the concentration of magnesium trifluoromethanesulfonate in the magnesium trifluoromethanesulfonate solution is 0.005 mol / L. Ensure that the mass ratio of natural graphite powder, pyrrole monomer, copper nitrate and magnesium trifluoromethanesulfonate is 1000:20:40:0.005.

[0081] Step (2): Add 1 kg of natural spherical graphite powder to the magnesium trifluoromethanesulfonate solution and stir at room temperature to mix it evenly, ensuring that the pH value of the system is 2.5;

[0082] Step (3): Add copper nitrate solution to the mixture obtained in step (2) and stir at room temperature to make the system uniformly mixed;

[0083] Step (4): Add the pyrrole monomer solution to the mixture obtained in step (3). During the experiment, maintain the temperature at room temperature and stir at a speed of 600 rpm. Under these conditions, react for 2 hours. After the reaction is completed, age the product at 60°C for 24 hours.

[0084] Step (5): The aged product is cleaned, filtered, dried and carbonized. The cleaning process uses deionized water to clean the product multiple times until the pH of the final cleaning solution is 7. The product drying process is carried out at a temperature of 80°C for 24 hours and at a calcination temperature of 850°C. Finally, a black powder material is obtained, which is the natural spherical graphite composite negative electrode material.

[0085] Test Example 1

[0086] In this test example, a Hitachi S-4800 scanning electron microscope was used to perform field emission scanning electron microscopy analysis on the natural graphite composite anode materials provided in Examples 1-3 of this invention under normal test conditions. The obtained scanning electron microscope images and elemental distribution maps obtained by SEM+mapping are shown in Figures 1a-1h.

[0087] As can be seen from Figures 1a-1f, the natural graphite composite negative electrode material particles provided in Examples 1-3 of the present invention are nearly spherical, with a relatively smooth surface and no obvious damage.

[0088] As can be seen from Figures 1g-1h, compared to the natural graphite composite anode material provided in Comparative Example 1, the natural graphite composite anode material provided in Example 1 of this invention has magnesium ions uniformly dispersed on the surface of the particles, while sodium ions are basically absent (as shown in Figure 1g). This proves that under acidic conditions, magnesium ions do indeed replace sodium ions in sodium alginate, forming magnesium alginate hydrogel. This magnesium alginate hydrogel forms a loose, three-dimensional carbon network after carbonization. Meanwhile, Figures 1g-1h also show that copper is dispersed on the surface of the natural graphite composite anode material particles provided in Example 1 and Comparative Example 1, indicating that copper is indeed doped into the amorphous carbon coating layer.

[0089] Test Example 2

[0090] This test example also tested the electrochemical performance of the natural graphite composite anode materials provided in each embodiment and comparative example, including the following specific steps:

[0091] Step 1): The natural graphite composite negative electrode materials provided in each embodiment and comparative example are used as negative electrode active materials. The three materials are mixed evenly according to the mass ratio of negative electrode active material: LA133: SuperP = 94:3:3 and then coated on the copper foil current collector. After drying, cutting and rolling, the negative electrode sheet is obtained.

[0092] Step 2): Assemble the obtained negative electrode sheets into 2025 coin cells and conduct initial charge capacity and first-week coulombic efficiency tests. The counter electrode is a lithium sheet, the electrolyte solute is LiPF6, the solvent is a mixture of DEC, DMC and EC in a 1:1:1 volume ratio, the concentration of LiPF6 is 1 mol / L, and the separator is commercially available Celgard 2320. The tests were conducted on a battery testing instrument CT300A1U, with a charge / discharge voltage of 0.005-1.5V. The first week was conducted with deep discharge (0.1C-0.01C) and 0.1C charge. The electrochemical performance is shown in Figure 2 and Table 1.

[0093] Table 1

[0094] As can be seen from Figure 2 and Table 1, compared with the natural graphite composite anode material provided in Comparative Example 1, the natural graphite composite anode materials provided in Examples 1-3 of this invention all exhibit better cycling performance. Especially after 100 cycles, the natural graphite composite anode material provided in Comparative Example 1 shows significant capacity decay, while the natural graphite composite anode materials provided in Examples 1-3 of this invention exhibit smaller capacity fluctuations, with their first-cycle discharge specific capacity generally above 400 mAh / g and their first-cycle coulombic efficiency all above 91%. These experimental results are sufficient to demonstrate that the natural graphite composite anode materials provided in these embodiments of the invention possess excellent structural stability and electrochemical cycling performance.

[0095] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A natural graphite composite anode material, characterized in that, The natural graphite composite anode material includes natural graphite, a loose three-dimensional carbon network covering the natural graphite, and an amorphous carbon coating layer disposed outside the loose three-dimensional carbon network; wherein, magnesium ions and / or aluminum ions are dispersed in the loose three-dimensional carbon network, and copper particles and / or silver particles are doped in the amorphous carbon coating layer.

2. The natural graphite composite anode material according to claim 1, characterized in that, Magnesium ions and / or aluminum ions are uniformly dispersed in the fluffy three-dimensional carbon network.

3. The natural graphite composite anode material according to claim 1 or 2, characterized in that, Copper particles and / or silver particles are uniformly doped into the amorphous carbon coating layer.

4. The natural graphite composite anode material according to claim 3, characterized in that, Copper particles are elemental copper, and silver particles are elemental silver.

5. The natural graphite composite anode material according to claim 1 or 2, characterized in that, The natural graphite is natural spherical graphite.

6. The method for preparing the natural graphite composite anode material according to any one of claims 1-5, characterized in that, The preparation method includes: Step (1): Disperse pyrrole monomer, copper nitrate and / or silver nitrate, magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate and sodium alginate evenly in a solvent to obtain pyrrole monomer solution, copper nitrate and / or silver nitrate solution, magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate solution and sodium alginate solution. Step (2): Add natural graphite to the solution of magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate and mix them evenly. The system is acidic. Step (3): Add sodium alginate solution to the mixture obtained in step (2). Under the conditions of stirring and acidity at 20-30℃, magnesium ions and / or aluminum ions in the solution replace sodium ions in sodium alginate through a displacement reaction to form and precipitate a hydrogel of magnesium alginate and / or aluminum alginate. Step (4): Add the solution of copper nitrate and / or silver nitrate to the mixture obtained in step (3) and mix them evenly; Step (5): Add the pyrrole monomer solution to the mixture obtained in step (4), and carry out the reaction under stirring and constant temperature conditions. After the reaction is completed, the product is aged. Step (6): The aged product is sequentially cleaned, filtered, dried and carbonized to obtain the natural graphite composite anode material.

7. The preparation method according to claim 6, characterized in that, The mass ratio of natural graphite powder, pyrrole monomer, copper nitrate and / or silver nitrate, sodium alginate and magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate is 1000:5~80:30~100:0.00001~50:0.001~50.

8. The preparation method according to claim 6 or 7, characterized in that, In step (1), the concentration of pyrrole monomer in the pyrrole monomer solution is 0.1-1.5 mol / L, the concentration of copper nitrate and / or silver nitrate in the copper nitrate and / or silver nitrate solution is 0.05-1.9 mol / L, the concentration of sodium alginate in the sodium alginate solution is 0.001-1 mol / L, and the concentration of magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate in the magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate solution is 0.0001-5 mol / L.

9. The preparation method according to claim 8, characterized in that, In step (1), pyrrole monomer, copper nitrate, magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate and sodium alginate are uniformly dispersed in a solvent to obtain a pyrrole monomer solution, a copper nitrate solution, a magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate solution and a sodium alginate solution, wherein the concentration of copper nitrate is 0.05-1.5 mol / L.

10. The preparation method according to claim 8, characterized in that, In step (1), pyrrole monomer, copper nitrate and / or silver nitrate, aluminum trifluoromethanesulfonate and sodium alginate are uniformly dispersed in a solvent to obtain a pyrrole monomer solution, a copper nitrate and / or silver nitrate solution, an aluminum trifluoromethanesulfonate solution and a sodium alginate solution, wherein the concentration of aluminum trifluoromethanesulfonate is 0.0001 to 0.2 mol / L.

11. The preparation method according to claim 6 or 7, characterized in that, In step (1), pyrrole monomer, copper nitrate and / or silver nitrate, and magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate are uniformly dispersed in a solvent to obtain a pyrrole monomer solution, a copper nitrate and / or silver nitrate solution, and a magnesium trifluoromethanesulfonate and / or aluminum trifluoromethanesulfonate solution; wherein the solvent includes deionized water and / or an organic solvent. Sodium alginate was uniformly dispersed in deionized water to obtain a sodium alginate solution.

12. The preparation method according to claim 6 or 7, characterized in that, In step (2), the pH value of the system is 1 to 5.

13. The preparation method according to claim 6 or 7, characterized in that, In step (3), the displacement reaction takes 2 to 5 hours.

14. The preparation method according to claim 6 or 7, characterized in that, In step (5), the reaction temperature is from room temperature to 60°C, and the time is 2 to 5 hours.

15. The preparation method according to claim 6 or 7, characterized in that, In step (5), the aging process is carried out at room temperature to 60°C for no less than 12 hours.

16. The preparation method according to claim 6 or 7, characterized in that, In step (6), the drying process involves drying at 60–120°C for 12–24 hours.

17. The preparation method according to claim 6 or 7, characterized in that, In step (6), the carbonization temperature is 800-1500℃.

18. A lithium-ion battery, characterized in that, The negative electrode material of the lithium-ion battery is the natural graphite composite negative electrode material as described in any one of claims 1-5.

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