Modified graphite negative electrode material, preparation method thereof and battery

Abstract

The invention provides a modified graphite negative electrode material, a preparation method thereof and a battery. The modified graphite negative electrode material comprises a graphite base material and a coating layer coating the surface of the graphite base material, and the coating layer comprises a carbon material and MoO3 particles dispersed in the carbon material and on the surface of the carbon material. According to the modified graphite negative electrode material provided by the invention, the MoO3 and the carbon material in the coating layer are synergistically matched, so that the modified graphite negative electrode material has excellent ionic conductivity and relatively low desolvation energy at the same time, the conduction performance of lithium ions can be remarkably improved, and the desolvation speed of solvated lithium ions is increased; the graphite negative electrode material prepared by the method is favorable for forming an efficient lithium ion transmission interface between a negative electrode and an electrolyte, and can effectively block migration of electrons and solvents, so that the rapid charging performance of the graphite negative electrode material is remarkably improved, and the overall performance of a battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a modified graphite negative electrode material, a preparation method thereof, and a battery, and particularly relates to a modified graphite negative electrode material more suitable for lithium-ion batteries, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] Graphite is a crucial negative electrode material in rechargeable lithium-ion batteries and is widely used due to its excellent electrochemical stability. However, there are still many challenges in achieving efficient charging in a short time. In previous studies, the surface of graphite was modified, such as using pyrolytic carbon materials, aiming to improve the uniformity of Li + flux and maintain an open edge structure to facilitate the rapid entry of lithium ions and improve the efficiency of the charge transfer interface. The above modification methods have improved the high-speed storage capacity of graphite to a certain extent. However, the surface modification of traditional pitch-derived carbon materials often faces some limitations. Specifically, traditional pitch-derived carbon materials usually cannot effectively isolate solvents from electrons, resulting in insufficient rate capabilities. This deficiency makes it difficult for the modified graphite negative electrode material to meet the performance requirements for rapid charging in practical applications. Therefore, developing modified materials that can effectively isolate solvents from electrons to improve the applicability and efficiency of graphite in the field of rapid charging will be an important direction for future research.

[0003] Improving the fast charging performance of graphite negative electrode materials is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a modified graphite negative electrode material, a preparation method thereof, and a battery. The modified graphite negative electrode material provided by the present invention has the synergistic cooperation of MoO3 and carbon materials in the coating layer, and simultaneously has excellent ionic conductivity and low desolvation energy, which can significantly improve the conduction performance of lithium ions and increase the desolvation speed of solvated lithium ions. This not only helps to form an efficient lithium ion transport interface between the negative electrode and the electrolyte, but also effectively blocks the migration of electrons and solvents, achieving a significant improvement in the fast charging performance of the graphite negative electrode material, thereby improving the overall performance of the battery.

[0005] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a modified graphite negative electrode material, which includes a graphite matrix material and a coating layer coated on the surface of the graphite matrix material. The coating layer includes a carbon material and MoO3 particles dispersed inside and on the surface of the carbon material.

[0007] The modified graphite anode material provided by the present invention is coated with MoO3 and carbon material synergistically on the surface of the graphite matrix. The MoO3 particles are evenly dispersed inside and on the surface of the carbon material, and it has both excellent ionic conductivity and low desolvation energy. MoO3 can achieve lithium storage through the conversion reaction with lithium, and due to the Li2O generated in the initial conversion reaction, the volume change is small, which can significantly improve the lithium ion conduction performance; the carbon material is evenly coated on the surface of the graphite matrix material, which not only provides an electron transfer path, but also improves the desolvation speed of solvated lithium ions, promotes the solvation adsorption rate of lithium ions, improves the diffusion ability of lithium ions, and realizes a significant improvement in the fast charging performance of the graphite anode material, thereby improving the overall performance of the battery.

[0008] In the present invention, MoO3 and the carbon material cooperate synergistically and are indispensable. If only MoO3 is coated, there will be problems of insufficient diffusion ability and poor electronic conductivity. The conductivity of MoO3 in the lithium ion insertion and conversion reaction is relatively low, and relying solely on MoO3 cannot effectively provide enough electron conduction paths, resulting in the inability to fully exert the battery performance. Especially under fast charging conditions, the ideal performance may not be achieved; if it is coated with pure carbon material, the problems of lithium ion storage and its volume change control cannot be solved. Although pure carbon material can provide an electron conduction path, it lacks the ability of lithium ion storage and conversion reaction, so it cannot effectively improve the capacity and stability. In addition, the carbon material cannot alleviate the volume expansion caused by the insertion or extraction of lithium ions, and still cannot optimize the long-cycle stability of the battery. And if it is coated with a mixture of other molybdenum oxides and carbon materials, such as molybdenum dioxide, the same synergistic effect as MoO3 cannot be achieved. The conversion reaction process of molybdenum dioxide is more complex than that of MoO3, and the volume change is larger, resulting in poor mechanical stability of the material. In addition, the conductivity and lithium ion conversion ability of molybdenum dioxide are also inferior to MoO3, resulting in limited effects in improving the overall performance and fast charging ability of the battery.

[0009] The following are the preferred technical solutions of the present invention, but they do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0010] Preferably, the MoO3 particles include nano-MoO3 particles.

[0011] In the present invention, the MoO3 particles are selected from nano-MoO3 particles, which can be more uniformly dispersed in the carbon material, and the coating is more uniform, which is more conducive to improving the surface activity and ion diffusion rate of the material. The nano-scale MoO3 particles can provide more reactive sites, and through the synergistic effect with the carbon material, significantly enhance the lithium ion conversion reaction performance and electrical conductivity. This uniformly dispersed structure can effectively reduce particle aggregation and optimize the conduction paths of electrons and ions, thereby improving the cycle stability and fast charging performance of the battery.

[0012] Preferably, the carbon source of the carbon material includes a surfactant.

[0013] In the present invention, a surfactant is selected as the carbon source, and the carbon layer structure obtained by its carbonization can better play the synergistic cooperation with MoO3, not only providing an electron transfer path, but also promoting the + solvation adsorption of Li, improving the + diffusion ability of Li and optimizing the electrochemical performance.

[0014] In a second aspect, the present invention provides a method for preparing the modified graphite anode material as described in the first aspect, and the preparation method includes the following steps:

[0015] Carry out liquid-phase mixing and coating of the graphite material to be modified with a molybdenum source solution to obtain a coated product, and heat-treat the coated product in a protective atmosphere to obtain the modified graphite anode material;

[0016] Wherein, the molybdenum source solution includes a molybdenum source, a surfactant and a solvent; the valence of molybdenum in the molybdenum source is +6.

[0017] The preparation method provided by the present invention can effectively disperse the molybdenum source particles by introducing a surfactant, prevent their agglomeration, reduce the mutual attraction between particles, and increase the contact area between reactants, which is crucial for subsequent heat treatment; at the same time, during the heat treatment process in a protective atmosphere, the surfactant not only plays a dispersing role, but also can regulate the nucleation process of MoO3, and under the action of heat treatment, pyrolyzes to form a carbon layer, so that the MoO3 particles are uniformly dispersed in the carbon layer; a modified graphite anode material with excellent performance is obtained; and this method is simple and feasible, has good industrial potential, and is suitable for large-scale production.

[0018] In the present invention, the addition of the surfactant is essential, and the atmosphere of subsequent heat treatment and the valence of molybdenum are also crucial. If there is no surfactant, or the valence of molybdenum is not +6 or other atmospheres, such as air atmosphere or reducing atmosphere, etc., a specific MoO3 product cannot be obtained.

[0019] Preferably, the molybdenum source includes molybdate, and the molybdate includes ammonium molybdate.

[0020] For the type of molybdenum source selected in the present invention, during the subsequent heat treatment process, it can be decomposed to obtain MoO3 products. In addition to molybdates, other molybdenum source types of molybdenum with a +6 valence having the same effect are also applicable to the present invention.

[0021] Preferably, the addition amount of the molybdenum source is 0.5% - 1.5% of the mass of the graphite material to be modified, such as 0.5%, 0.75%, 1%, 1.25% or 1.5%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] In the present invention, by controlling the addition amount of the molybdenum source to be 0.5% - 1.5% of the mass of the graphite material to be modified, the dispersion effect of MoO3 particles is more excellent, and the synergistic cooperation effect with the carbon material is more outstanding, and the capacity, cycle and fast charging performance of the obtained modified graphite anode material can be further improved.

[0023] Preferably, the median particle size of the graphite material to be modified is 5 - 15 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Preferably, the addition amount of the surfactant is 20% - 40% of the mass of the molybdenum source, such as 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] In the present invention, the addition amount of the surfactant can control the size and morphology of MoO3 particles, thereby promoting the formation of more uniform particles. Further, the addition amount is limited to 20% - 40% of the mass of the molybdenum source, which helps to improve the dispersion and stability of MoO3 particles and prevent particle aggregation; an appropriate amount of surfactant can precisely control the size of MoO3 particles, making them maintain a small and uniform morphology, thereby optimizing the binding effect with the carbon material.

[0026] Preferably, the surfactant includes any one or a combination of at least two of cetyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride or octadecyldimethylhydroxyethylammonium.

[0027] The surfactant provided by the present invention, on the one hand, serves as a carbon source and pyrolyzes to form a carbon layer during the heat treatment process. On the other hand, it also realizes the dispersion of the molybdenum source and controls the particle size and morphology of MoO3 during the subsequent heat treatment process.

[0028] Preferably, the solid content of the molybdenum source solution is 30% - 50%, such as 30%, 35%, 40%, 45% or 50%, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0029] It should be noted that adjusting the solid content of the molybdenum source solution of the present invention to 30% - 50% is more conducive to the dispersion of the molybdenum source and better plays the role of the surfactant. And the solvent in the molybdenum source solution is selected by conventional techniques. The present invention is applicable to the types of solvents that can disperse the molybdenum source and dissolve the surfactant. For example, the solvent can be selected from water.

[0030] Preferably, the product after liquid-phase mixing and coating is dried to obtain a coating.

[0031] In the present invention, the purpose of drying is to remove the solvent in the system for subsequent heat treatment.

[0032] Preferably, the temperature of the heat treatment is 400 - 600 °C, such as 400 °C, 425 °C, 450 °C, 475 °C, 500 °C, 525 °C, 550 °C, 575 °C or 600 °C, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0033] In the present invention, by adjusting the temperature of the heat treatment to 400 - 600 °C, the decomposition reaction of the molybdenum source to obtain MoO3 is more complete, and the pyrolytic carbonization of the surfactant can also be realized, which better improves the crystallinity and dispersion of MoO3 particles. An appropriate heat treatment temperature helps to ensure that the molybdenum source is completely converted into MoO3, and at the same time promotes the carbonization of the surfactant to form a carbon-based material. This not only optimizes the combination of MoO3 and the carbon material, but also enhances its conductivity, further improving the overall performance of the battery. Preferably, the time of the heat treatment is 1 - 5 h, such as 1 h, 2 h, 3 h, 4 h or 5 h, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0034] As a preferred technical solution, the preparation method includes the following steps:

[0035] The graphite material to be modified is subjected to liquid-phase mixing and coating with a molybdenum source solution having a solid content of 30% - 50%. The addition amount of the molybdenum source is 0.5% - 1.5% of the mass of the graphite material to be modified. After drying, a coating is obtained. The coating is heat-treated at 400 - 600 °C for 1 - 5 h in a protective atmosphere to obtain the modified graphite anode material;

[0036] Among them, the molybdenum source solution includes a molybdenum source, a surfactant and a solvent, and the addition amount of the surfactant is 20% to 40% of the mass of the molybdenum source; the valence of molybdenum in the molybdenum source is +6 valence.

[0037] It should also be noted that:

[0038] The present invention does not make special limitations on the specific source of the graphite material to be modified. Those skilled in the art can directly purchase the required graphite material, such as commercially available natural graphite or artificial graphite, etc.; it can also be directly prepared by conventional technical solutions and can be adaptively selected according to actual needs.

[0039] In addition, the present invention does not make special limitations on the gas in the protective atmosphere. Any gas type that can avoid other decomposition of the molybdenum source is applicable to the present invention. For example, nitrogen and / or inert gas, etc., and the inert gas includes argon or helium, etc.

[0040] In a third aspect, the present invention also provides a battery, and the battery includes the modified graphite negative electrode material as described in the first aspect or the modified graphite negative electrode material prepared by the preparation method as described in the second aspect.

[0041] Preferably, the battery includes a lithium-ion battery.

[0042] It can be understood that the modified graphite material provided by the present invention is not only limited to being used in lithium-ion batteries. For other battery types that can use graphite as the negative electrode, the present invention is also applicable. For example, sodium-ion batteries; while it is preferably used in lithium-ion batteries, the modification effect is more excellent.

[0043] In addition, the modified graphite negative electrode material in the present invention can be used alone as the negative electrode material and directly used in lithium-ion batteries; it can also be mixed with other negative electrode materials (such as silicon materials, etc.) and jointly used in lithium-ion batteries.

[0044] In the lithium-ion battery, except for the modified graphite negative electrode material defined by the present invention, its preparation raw materials, preparation methods and specific structures are all conventional technical solutions, and the existing technical content that can be known within a reasonable range by those skilled in the art is applicable to the present invention.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The modified graphite anode material provided by the present invention has a synergistic coating of MoO3 and carbon material on the surface of the graphite matrix. It simultaneously has excellent ionic conductivity and a low desolvation energy. MoO3 can achieve lithium storage through a conversion reaction with lithium, and due to the small volume change of Li2O generated in the initial conversion reaction, it can significantly improve the conduction performance of lithium ions. The carbon material is uniformly coated on the surface of the graphite matrix material, which not only provides an electron transfer path but also enhances the desolvation speed of solvated lithium ions, promotes the solvation adsorption rate of lithium ions, improves the diffusion ability of lithium ions, and significantly enhances the fast charging performance of the graphite anode material, thereby improving the overall performance of the battery.

[0047] (2) The preparation method provided by the present invention can effectively disperse molybdenum source particles by introducing surfactants, prevent their agglomeration, reduce the mutual attraction between particles, increase the contact area between reactants, which is crucial for subsequent heat treatment. At the same time, during the heat treatment in a protective atmosphere, the surfactant not only plays a role in dispersion but also can regulate the nucleation process of MoO3, and under the action of heat treatment, it pyrolyzes to form a carbon layer, making MoO3 particles uniformly dispersed in the carbon layer, obtaining a modified graphite anode material with excellent performance. Moreover, this method is simple and feasible, has good industrial potential, and is suitable for large-scale production. Brief Description of the Drawings

[0048] Figure 1 SEM image of the modified graphite anode material provided in Example 1 of the present invention.

[0049] Figure 2 XPS full spectrum of the modified graphite anode material provided in Example 1 of the present invention.

[0050] Figure 3 High-resolution spectrum of the Mo 3d peak in the XPS full spectrum of the modified graphite anode material provided in Example 1 of the present invention. Detailed Description of the Embodiments

[0051] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0053] In the description of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary and secondary relationship of the indicated technical features.

[0054] Example 1

[0055] The present embodiment provides a modified graphite negative electrode material, which includes an artificial graphite matrix material and a coating layer coated on the surface of the artificial graphite matrix material, wherein the coating layer includes a carbon material and nano-MoO3 particles dispersed inside and on the surface of the carbon material.

[0056] The preparation method of the modified graphite negative electrode material is as follows:

[0057] Ammonium molybdate ((NH4)6Mo7O 24 ·4H2O) and cetyltrimethylammonium bromide (CTAB) are mixed in a mass ratio of 100:30 (the amount of CTAB added is 30% of the mass of ammonium molybdate), and stirred evenly in an appropriate amount of deionized water until a uniform solution is formed to obtain a molybdenum source solution with a solid content of 50%;

[0058] Subsequently, 500 g of artificial graphite with a median particle size of 12.5 μm (the amount of ammonium molybdate added was 0.5% of the artificial graphite) was added to the above solution and stirred thoroughly to ensure uniform dispersion. Next, the mixture was placed in a kneading pot (non-sealed environment) and stirred at 150° C. for 4 hours for drying to obtain a coating of dry powder;

[0059] The dried powder was transferred to a tube furnace and subjected to a heat treatment at 550° C. for 1 h in an argon atmosphere to obtain the modified graphite negative electrode material.

[0060] Figure 1 The SEM image of the modified graphite negative electrode material in Example 1 of the present invention is shown. Figure 1 It can be seen that the surface of the artificial graphite matrix material has a uniformly coated coating layer, and in the coating layer, molybdenum trioxide particles (white particles) are uniformly distributed inside and on the surface of the carbon material.

[0061] Figure 2 The XPS full spectrum of the modified graphite negative electrode material in Example 1 of the present invention is shown.

[0062] Figure 3 The high-resolution spectrum of the Mo3d peak in XPS of the modified graphite negative electrode material in Example 1 of the present invention is shown.

[0063] from Figure 2 and Figure 3It can be seen that the 3d peak of Mo appears in the full spectrum, and in the high-resolution spectrum of the 3d peak of Mo, Mo appears 6+ 3d 5 / 2 and 3D 3 / 2 The two characteristic peaks of MoO3 indicate that MoO3 is successfully coated on the graphite surface.

[0064] Example 2

[0065] The present embodiment provides a modified graphite negative electrode material, which includes an artificial graphite matrix material and a coating layer coated on the surface of the artificial graphite matrix material, wherein the coating layer includes a carbon material and nano-MoO3 particles dispersed inside and on the surface of the carbon material.

[0066] The preparation method of the modified graphite negative electrode material is as follows:

[0067] Ammonium molybdate ((NH4)6Mo7O 24 4H2O) and cetyltrimethylammonium bromide (CTAB) are mixed in a mass ratio of 100:20 (the amount of CTAB added is 20% of the mass of ammonium molybdate), and stirred evenly in an appropriate amount of deionized water until a uniform solution is formed to obtain a molybdenum source solution with a solid content of 50%;

[0068] Subsequently, 500 g of artificial graphite with a median particle size of 12.5 μm (the amount of ammonium molybdate added was 1% of the artificial graphite) was added to the above solution and stirred thoroughly to ensure uniform dispersion. Next, the mixture was placed in a kneading pot (non-sealed environment) and stirred at 150° C. for 4 hours for drying to obtain a coating of dry powder;

[0069] The dried powder was transferred to a tube furnace and subjected to a heat treatment at 400° C. for 5 h in an argon atmosphere to obtain the modified graphite negative electrode material.

[0070] Example 3

[0071] The present embodiment provides a modified graphite negative electrode material, which includes an artificial graphite matrix material and a coating layer coated on the surface of the artificial graphite matrix material, wherein the coating layer includes a carbon material and nano-MoO3 particles dispersed inside and on the surface of the carbon material.

[0072] The preparation method of the modified graphite negative electrode material is as follows:

[0073] Ammonium molybdate ((NH4)6Mo7O 24·4H2O) and cetyltrimethylammonium bromide (CTAB) are mixed in a mass ratio of 100:40 (the amount of CTAB added is 40% of the mass of ammonium molybdate), and stirred evenly in an appropriate amount of deionized water until a uniform solution is formed to obtain a molybdenum source solution with a solid content of 30%;

[0074] Subsequently, 500 g of artificial graphite with a median particle size of 10 μm (the amount of ammonium molybdate added was 1.5% of the artificial graphite) was added to the above solution and stirred thoroughly to ensure uniform dispersion. Next, the mixture was placed in a kneading pot (non-sealed environment) and stirred at 150° C. for 4 hours for drying to obtain a dry powder coating;

[0075] The dried powder was transferred to a tube furnace and heat treated at 600° C. for 1 h in an argon atmosphere to obtain the modified graphite negative electrode material.

[0076] Example 4

[0077] The difference between this embodiment and embodiment 1 is that the graphite material to be modified in this embodiment is natural spherical graphite, and the surfactant is octadecyl dimethyl hydroxyethyl ammonium.

[0078] The rest of the preparation methods and parameters were the same as those in Example 1.

[0079] Example 5

[0080] The difference between this embodiment and embodiment 1 is that the amount of CTAB added in this embodiment is 15% of the mass of ammonium molybdate.

[0081] The rest of the preparation methods and parameters were the same as those in Example 1.

[0082] Example 6

[0083] The difference between this embodiment and embodiment 1 is that the amount of CTAB added in this embodiment is 45% of the mass of ammonium molybdate.

[0084] The rest of the preparation methods and parameters were the same as those in Example 1.

[0085] Example 7

[0086] The difference between this embodiment and embodiment 1 is that in this embodiment, the amount of ammonium molybdate added is 0.1% of the artificial graphite.

[0087] The rest of the preparation methods and parameters were the same as those in Example 1.

[0088] Example 8

[0089] The difference between this embodiment and embodiment 1 is that in this embodiment, the amount of ammonium molybdate added is 2% of the artificial graphite.

[0090] The remaining preparation methods and parameters are the same as those in Example 1.

[0091] Example 9

[0092] The difference between this example and Example 1 is that the heat treatment temperature in this example is 300 °C.

[0093] The remaining preparation methods and parameters are the same as those in Example 1.

[0094] Example 10

[0095] The difference between this example and Example 1 is that the heat treatment temperature in this example is 700 °C.

[0096] The remaining preparation methods and parameters are the same as those in Example 1.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 is that the modified graphite anode material in this comparative example is coated with pure MoO3 particles.

[0099] In the preparation method, no surfactant is added.

[0100] The remaining preparation methods and parameters are the same as those in Example 1.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that in the modified graphite anode material of this comparative example, the coating layer includes a carbon material and nano-MoO2 particles dispersed in the carbon material.

[0103] In the preparation method, ammonium molybdate is replaced with molybdenum dioxide.

[0104] The remaining preparation methods and parameters are the same as those in Example 1.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 1 is that in the preparation method of this example, no molybdenum source is added, and an equal amount of cetyltrimethylammonium bromide (CTAB) is dissolved in water and mixed with graphite for coating.

[0107] The remaining preparation methods and parameters are the same as those in Example 1.

[0108] Control Group

[0109] The difference between this control group and Example 1 is that the anode material in this comparison group is artificial graphite material without any modification treatment of ammonium molybdate and surfactant in the example.

[0110] The graphite anode materials provided by Examples 1-10, Comparative Examples 1-3, and the control group were used to prepare batteries and conduct performance tests.

[0111] [I] Battery Preparation

[0112] The graphite anode materials obtained from each of the examples, comparative examples, and the control were used as the negative active material, and were mixed according to the mass ratio of negative active material: conductive carbon black: CMC: SBR = 95.3: 1.5: 1.4: 1.8. Using deionized water as the solvent, after mixing the slurry, it was coated on a copper foil, and the coating surface density was 6.5 ± 0.1 mg / cm 2 , and after vacuum drying at 90 °C, a negative electrode sheet was obtained, and the negative electrode sheet was roll-pressed to a compaction density of 1.65 ± 0.02 g / cc; a lithium sheet was used as the counter electrode.

[0113] The negative electrode sheet, lithium sheet, electrolyte (1 mol / L LiPF6, EC: EMC = 1: 1), and Celgard 2400 separator were assembled into a button cell.

[0114] [II] Performance Test

[0115] The obtained batteries were subjected to capacity and rate tests at 25 ± 2 °C.

[0116] a) Capacity test: At 25 ± 2 °C, the voltage range was 0.005 V to 2 V, and the capacity test was carried out at a charge-discharge rate of 0.05 C.

[0117] b) Rate test; At 25 ± 2 °C, ① discharge at 0.05 C to 0.005 V, stand for 30 min; charge at 0.05 C to 2 V, stand for 30 min; ② discharge at 0.5 C to 0.005 V, stand for 30 min; charge at 0.5 C to 2 V, stand for 30 min; ③ discharge at 1.2 C to 0.005 V, stand for 30 min; charge at 1.2 C to 2 V, stand for 30 min.

[0118] c) Cycle test: At 25 ± 2 °C, ① charge at a constant current of 1 C to the charge cut-off voltage of 4.2 V, then charge at a constant voltage until the current is 0.05 C, and stand for 10 minutes, ② then discharge at a constant current of 1 C to the discharge cut-off voltage of 3 V, and record its initial capacity as C0. Then repeat ①-②, record the discharge capacity Cn of each cycle until the cycle capacity retention rate (Cn / C0 × 100%) is 80%, and record the number of cycles.

[0119] The test results of the above tests are shown in Table 1.

[0120] Table 1

[0121]

[0122]

[0123] In summary, for the modified graphite anode material provided by the present invention, the synergistic cooperation between MoO3 and the carbon material in the coating layer has both excellent ionic conductivity and low desolvation energy, which can significantly improve the conduction performance of lithium ions and increase the desolvation rate of solvated lithium ions. This not only helps to form an efficient lithium ion transport interface between the anode and the electrolyte, but also effectively blocks the migration of electrons and solvents, thereby improving the overall performance of the battery. In the modification preparation method, the introduction of the surfactant can effectively disperse the molybdenum source particles, prevent their agglomeration, reduce the mutual attraction between the particles, and increase the contact area between the reactants, which is crucial for the subsequent heat treatment. At the same time, during the heat treatment in a protective atmosphere, the surfactant not only plays a dispersing role, but also can regulate the nucleation process of MoO3, and under the action of heat treatment, pyrolyzes to form a carbon layer, so that the MoO3 particles are uniformly dispersed inside and on the surface of the carbon material.

[0124] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A modified graphite anode material, characterized in that, The modified graphite anode material includes a graphite matrix material and a coating layer coated on the surface of the graphite matrix material. The coating layer includes a carbon material and MoO3 particles dispersed inside and on the surface of the carbon material.

2. The modified graphite negative electrode material according to claim 1, wherein The MoO3 particles include nano-MoO3 particles.

3. A preparation method of the modified graphite anode material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: Carry out liquid-phase mixing and coating of the graphite material to be modified with a molybdenum source solution to obtain a coated product, and heat-treat the coated product in a protective atmosphere to obtain the modified graphite anode material; Wherein, the molybdenum source solution includes a molybdenum source, a surfactant and a solvent; the valence of molybdenum in the molybdenum source is +6.

4. The preparation method according to claim 3, wherein The molybdenum source includes molybdate, and the molybdate includes ammonium molybdate.

5. The preparation method according to claim 3, characterized in that, The addition amount of the molybdenum source is 0.5% - 1.5% of the mass of the graphite material to be modified; Preferably, the median particle size of the graphite material to be modified is 5 - 15 μm.

6. The preparation method according to claim 3 or 5, characterized in that, The addition amount of the surfactant is 20% - 40% of the mass of the molybdenum source; Preferably, the surfactant includes any one or a combination of at least two of cetyltrimethylammonium bromide, dodecyl dimethyl benzyl ammonium chloride or octadecyldimethyl hydroxyethyl ammonium.

7. The preparation method according to claim 3, characterized in that, The solid content of the molybdenum source solution is 30% - 50%.

8. The preparation method according to claim 3, characterized in that, Dry the product after liquid-phase mixing and coating to obtain a coated product; Preferably, the temperature of the heat treatment is 400 - 600 °C, and the time of the heat treatment is 1 - 5 h.

9. The preparation method according to claim 3, characterized in that The preparation method includes the following steps: Carry out liquid-phase mixing and coating of the graphite material to be modified with a molybdenum source solution with a solid content of 30% - 50%, the addition amount of the molybdenum source is 0.5% - 1.5% of the mass of the graphite material to be modified, dry to obtain a coated product, and heat-treat the coated product in a protective atmosphere at 400 - 600 °C for 1 - 5 h to obtain the modified graphite anode material; Wherein, the molybdenum source solution includes a molybdenum source, a surfactant and a solvent, and the addition amount of the surfactant is 20% - 40% of the mass of the molybdenum source; the valence of molybdenum in the molybdenum source is +6.

10. A battery, characterized in that, The battery includes the modified graphite anode material as described in Claim 1 or 2 or the modified graphite anode material prepared by the preparation method as described in any one of Claims 3 - 9; Preferably, the battery includes a lithium-ion battery.

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