Negative electrode material, preparation method therefor, and use thereof

Abstract

The present application relates to the field of batteries, and in particular to a negative electrode material, a preparation method therefor, and a use thereof. The negative electrode material comprises: a substrate and a modification material layer provided on the surface of the substrate, wherein the substrate comprises hard carbon and graphite covering the hard carbon; the chemical formula of a modification material in the modification material layer is MoOx-MoyN, wherein the value of x is 2-3, and the value of y is 1-2. Compared with a conventional graphite negative electrode material, the negative electrode material has good fast charging performance and long-cycle interfacial electrochemical stability.

Description

A negative electrode material, its preparation method and application

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. CN202411219683.X, filed on September 2, 2024, entitled “A negative electrode material and its preparation method and application”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of batteries, and more specifically, to a negative electrode material, its preparation method, and its application. Background Technology

[0004] Since Sony first introduced lithium-ion batteries in the 1990s, graphite carbon (Gr) and its derived composite materials have been used as the mainstream anode material for lithium-ion batteries (LIBs), and it is generally believed that the anode material determines the fast-charging performance and power density of LIBs.

[0005] Theoretically, graphite (Gr) has a sufficiently high Li+ diffusion coefficient (D). Li+ >2×10 -10 cm 2 s -1 It supports full lithiation within 10 minutes (equivalent to charging at a rate of 6C). During charge / discharge, graphite operates at a low potential (relative to Li / Li). + Graphite exhibits a clear voltage plateau at <0.2V, along with relatively high initial and subsequent cycle coulombic efficiencies. These properties make graphite an attractive material for realizing high-energy-density lithium-ion batteries. While graphite's low redox potential promotes higher battery energy density, it also raises concerns when the graphite anode is subjected to fast-charging conditions. During fast charging, high current density leads to large anode polarization due to transport and kinetic limitations. These limitations can vary spatially across the entire anode thickness / volume, resulting in spatially non-uniform charging current. From a more microscopic perspective, in reality, at high charging rates, the presence of edge structural imperfections on the Gr surface, such as atomic-scale defects, lattice distortions, dangling bonds, and unintended chemical functionalizations, can block reversible Li+ diffusion into the bulk, thus affecting electrochemical performance. Meanwhile, in conventional vinyl carbonate electrolytes, Li... + Strong interaction with the solvent at the negative electrode / electrolyte interface leads to slow desolvation, and may even induce solvent co-intercalation into the Gr intermediate layer at high charge rates. Therefore, exfoliation along the (002) plane and parasitic solvent reduction reactions may occur on the Gr surface, which will lead to Li… +Transport path losses and the formation of a thick, organic-rich solid electrolyte interphase (SEI) hinder charge transfer at the Gr / electrolyte interface, significantly increasing interfacial resistance and voltage hysteresis. Furthermore, the significant negative electrode polarization during rapid charging of lithium-ion batteries can lead to lithium dendrite formation at the Gr negative electrode, causing short circuits and thermal runaway, thus reducing cycle life. Therefore, achieving high power density and long cycle life with Gr remains challenging.

[0006] In view of the above, this application is hereby submitted.

[0007] Application content

[0008] In view of this, in order to solve the problems of poor fast charging capability and poor interfacial electrochemical stability of traditional graphite anode materials, this application proposes an anode material, its preparation method and application. The anode material is an improvement on the traditional graphite anode material, and the obtained anode material has good fast charging capability and good interfacial electrochemical stability during long cycles.

[0009] In a first aspect, this application provides a negative electrode material, comprising: a matrix and a modifying material layer disposed on the surface of the matrix;

[0010] The matrix includes: hard carbon and graphite coating the hard carbon;

[0011] The chemical formula of the modifying material in the modifying material layer is MoO. x -Mo y N, where x takes values ​​from 2 to 3 and y takes values ​​from 1 to 2.

[0012] Beneficial effects: Compared with traditional graphite anode materials, the anode material described above has good fast charging performance and long-cycle interfacial electrochemical stability.

[0013] In one optional embodiment, the negative electrode material includes at least one of the following technical features:

[0014] (1) The mass ratio of the hard carbon to the graphite is (10-50):(50-90);

[0015] (2) The thickness of the modified material layer is 500 nm to 1 μm;

[0016] (3) The hard carbon includes at least one of phenolic resin, epoxy resin or o-aminophenol.

[0017] Secondly, this application provides a method for preparing a negative electrode material, comprising the following steps:

[0018] (a) The mixture containing ammonia, hard carbon and formaldehyde is subjected to a first reaction, and the precipitate is collected;

[0019] (b) The dispersion containing the precipitate and graphite is subjected to a first drying treatment and calcination to obtain the matrix;

[0020] (c) The mixture containing ammonium heptamolybdate and the matrix is ​​subjected to a second drying treatment and a first annealing treatment; the product obtained from the first annealing treatment is subjected to a second annealing treatment under an atmosphere of ammonia and hydrogen.

[0021] (d) The product obtained from the second annealing treatment is cooled and passivated under a nitrogen and oxygen atmosphere to obtain the negative electrode material.

[0022] In one optional embodiment, the method for preparing the negative electrode material includes at least one of the following technical features:

[0023] (1) The molar ratio of the ammonia water to the formaldehyde is 1:(1-3);

[0024] (2) The temperature of the first reaction is 75-85℃;

[0025] (3) The time for the first reaction is 4 to 6 hours.

[0026] In one optional embodiment, the method for preparing the negative electrode material includes at least one of the following technical features:

[0027] (1) The calcination temperature is 800-1300℃;

[0028] (2) The heating rate of the calcination is 1 to 3 °C / min;

[0029] (3) The calcination time is 2 to 5 hours.

[0030] In one optional embodiment, the method for preparing the negative electrode material includes at least one of the following technical features:

[0031] (1) The molar ratio of the ammonium heptamolybdate to the matrix is ​​1:(1-5);

[0032] (2) The temperature of the first annealing treatment is 250-400℃;

[0033] (3) The first annealing process takes 1 to 3 hours;

[0034] (4) The heating rate of the first annealing treatment is 4 to 6 °C / min.

[0035] In one optional embodiment, the method for preparing the negative electrode material includes at least one of the following technical features:

[0036] (1) The temperature of the second annealing treatment is 480-800℃;

[0037] (2) The second annealing process takes 1 to 3 hours;

[0038] (3) The heating rate of the second annealing treatment is 1 to 3 °C / min;

[0039] (4) When performing the second annealing treatment, the volume ratio of ammonia to hydrogen is (90-99):(1-10).

[0040] In one optional embodiment, the method for preparing the negative electrode material includes at least one of the following technical features:

[0041] (1) The passivation time is 1 to 3 hours;

[0042] (2) When the passivation is performed, the volume ratio of nitrogen to oxygen is (90-99):(1-10).

[0043] Thirdly, this application provides a negative electrode sheet, comprising the aforementioned negative electrode material or a negative electrode material prepared by the aforementioned method for preparing the negative electrode material.

[0044] Fourthly, this application provides a secondary battery, including the aforementioned negative electrode sheet.

[0045] Beneficial effects: (1) The negative electrode material provided in this application has a modified material layer that modifies a matrix of graphite and hard carbon. The mixing of graphite and hard carbon significantly improves the rate performance of the material, achieving a trade-off between energy density and power performance. The modified material layer has high ionic conductivity and low Li- content. + The diffusion barrier facilitates the formation of Li between graphite and electrolyte. + This modified layer exhibits rapid conduction and a low desolvation energy barrier, effectively preventing solvent molecule co-intercalation and mitigating failure issues such as electrolyte reduction side reactions, structural stripping, and lithium plating on the graphite surface during fast charging and long cycling. It also possesses a high Young's modulus, enabling it to withstand accumulated internal stress and volume expansion caused by the vigorous movement of lithium ions, significantly improving transport kinetics and achieving a balance between fast charging performance and long cycle life for the graphite anode. The modified material layer reduces parasitic solvent reduction reactions, effectively solving interfacial side reactions and lithium plating problems in the Gr anode under fast charging conditions, significantly improving the fast charging capability of the Gr anode while maintaining a long cycle life. Furthermore, the modified material layer exhibits a high electron work function, demonstrating its ability to alleviate electrolyte interface decomposition and fracture, as well as its superior electron blocking capability in fast charging mode.

[0046] (2) The preparation method of the negative electrode material provided in this application has a relatively simple production process, low raw material price, and can achieve large-scale production. The method can obtain a negative electrode material with excellent electrochemical performance. Moreover, the method is relatively simple and can be continuously produced, laying the foundation for the preparation of fast-charging graphite negative electrodes. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0048] One aspect of this application relates to a negative electrode material, comprising: a substrate and a modifying material layer disposed on the surface of the substrate;

[0049] The matrix includes: hard carbon and graphite coating the hard carbon;

[0050] The chemical formula of the modifying material in the modifying material layer is MoO. x -Mo y N, where x takes values ​​from 2 to 3 and y takes values ​​from 1 to 2.

[0051] The aforementioned anode material is an improvement on traditional anode materials. It uses a composite material in which graphite is coated on hard carbon as a matrix, and a modification material layer is formed on the surface of the matrix. Compared with traditional graphite anode materials, this anode material has good fast charging performance and long-cycle interfacial electrochemical stability.

[0052] This application blends hard carbon with graphite to achieve a trade-off between long cycle life and fast charging performance. The hard carbon material has a large interlayer spacing and a randomly arranged crystal structure, while Li... + The diffusion coefficient in hard carbon is significantly higher than that in graphite, making it suitable as a negative electrode material for fast-charging and high-power batteries. Furthermore, hard carbon possesses micropores and exhibits good compatibility with electrolytes, resulting in favorable reaction kinetics. As a fast-charging material, the voltage plateau of hard carbon is advantageous for Li... + It exhibits rapid embedding, is less prone to lithium plating, and offers good safety performance. Therefore, blending hard carbon with graphite is beneficial for improving the overall kinetic performance of the anode.

[0053] This application involves constructing MoO. x -Mo y N-modified nanomaterial layers fundamentally solve the structural stability problem of graphite materials. The modified materials have low solvent adsorption energy (Ea), which can promote the growth of Li. +The desolvation process improves solvent repulsion and effectively mitigates Li + The continuous exfoliation of the Gr structure induced by solvent co-intercalation results in a high Young's modulus for the modified material layer. This robust modified material layer can withstand the accumulated internal stress and volume expansion caused by the intense movement of lithium ions, ensuring long-term cycle durability. Furthermore, the modified material possesses a high electron work function, which can alleviate the decomposition and fracture of the electrolyte interface under fast charging conditions and prevent electron leakage from the negative electrode to the electrolyte layer. This enables the construction of a fast-conducting Li-type lithium-ion battery. + Channeling, reducing internal stress, blocking solvent molecule co-intercalation, and preventing valence electron leakage are all crucial for establishing a stable electrode / electrolyte interface for long-life, fast-charging LIBs.

[0054] Furthermore, the mass ratio of the hard carbon to the graphite is (10-50):(50-90), including but not limited to 10:90, 20:80, 30:70, 40:60, or 50:50. A matrix composed of hard carbon and graphite in a certain proportion is beneficial for improving the cycle stability and fast-charging capability of the negative electrode material.

[0055] Furthermore, the thickness of the modified material layer is 500 nm to 1 μm, including but not limited to point values ​​or ranges between any one of 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 750 μm, 800 μm, 850 μm, 900 μm, 950 μm or 1 μm.

[0056] This application does not specifically limit the type of hard carbon fiber; any conventional hard carbon fiber in the art can be used to implement the technical solutions of this application. In some specific embodiments, the hard carbon fiber includes, but is not limited to, resin carbon fiber, which includes, but is not limited to, at least one of phenolic resin, epoxy resin, or o-aminophenol.

[0057] This anode material can be used not only in lithium-ion batteries, but also in sodium-ion batteries, potassium-ion batteries, and all-solid-state batteries, demonstrating a wide range of applications. Furthermore, the production process is relatively simple, and the raw material costs are low, making large-scale production a promising possibility.

[0058] Another aspect of this application relates to a method for preparing the aforementioned negative electrode material, comprising the following steps:

[0059] (a) The mixture containing ammonia, hard carbon and formaldehyde is subjected to a first reaction, and the precipitate is collected;

[0060] (b) The dispersion containing the precipitate and graphite is subjected to a first drying treatment and calcination to obtain the matrix;

[0061] (c) The mixture containing ammonium heptamolybdate and the matrix is ​​subjected to a second drying treatment and a first annealing treatment; the product obtained from the first annealing treatment is subjected to a second annealing treatment under an atmosphere of ammonia and hydrogen.

[0062] (d) The product obtained from the second annealing treatment is cooled and passivated under a nitrogen and oxygen atmosphere to obtain the negative electrode material.

[0063] The method for preparing the negative electrode material involves forming MoO on the surface of a graphite and hard carbon mixed material using a simple crystallization and partial topological nitriding method. x -Mo y The N-modified layer, with randomly embedded MoO2 and Mo2N nanocrystals, enables the graphite anode to achieve fast charging and long cycle performance.

[0064] The method for preparing the anode material provides a structural domain that is a mixture of hard carbon and graphite. This domain is a cross-linked region formed during the calcination process of graphite and hard carbon, increasing the interlayer spacing of graphite, reducing the edge effect of graphite, and improving the long-cycle performance of graphite. The hard carbon material has a large interlayer spacing and a randomly arranged crystal structure. + The diffusion coefficient in hard carbon is significantly higher than that in graphite, making it suitable as a negative electrode material for fast-charging and high-power batteries. Blending the two in a certain ratio can, to some extent, balance long cycle life and fast-charging performance. Furthermore, a novel biphase MoO₂ is coated onto the surface of the blended material through simple crystallization and topological nitridation. x -Mo y The N-modified layer fundamentally solves the structural stability problem of graphite materials. It not only promotes the desolvation process of Li+ and improves solvent repulsion, but also effectively mitigates the effects of Li+ oxidative stress. + The continuous exfoliation of the Gr structure caused by solvent co-intercalation can also withstand the accumulated internal stress and volume expansion caused by the violent movement of lithium ions, ensuring long-term cycle durability.

[0065] The method for preparing the negative electrode material involves heating and uniformly mixing a certain volume of NH3·H2O in water and ethanol. Then, a solution of hard carbon and formaldehyde is added to the mixed solvent, and the mixture is stirred under heating conditions. The precipitate is separated by centrifugation, washed, and dried to obtain a brownish-yellow polymer powder. Next, the polymer powder and graphite are dispersed in water and mixed with ethanol, and stirred under heating conditions until the solvent is completely evaporated. The dried sample is then transferred to a high-temperature tube furnace for calcination to obtain a graphite and hard carbon blend, Gr@HC. Subsequently, a certain proportion of (NH4)6Mo7O is added using simple crystallization and induced nitridation topology techniques. 24• 4H₂O powder was dissolved in deionized water, and Gr@HC powder was added and mixed with the solution under continuous stirring. The resulting mixture was dried to form AMT@Gr@HC powder. MoO₂ was obtained by annealing under an Ar atmosphere. x @Gr@HC powder. Subsequently, an NH3 / H2 mixed gas was introduced into a tube furnace for secondary annealing. After cooling the powder obtained from the secondary annealing to room temperature, it was passivated in an N2 / O2 mixed gas to obtain MoO. x -Mo y A three-dimensional structure of N-modified graphite and hard carbon-doped anode. This structural design enables the formation of Li between the doped carbon material / electrolyte. + By rapidly conducting and blocking the co-intercalation of solvent molecules, the material / charge transport dynamics are improved, and the graphite anode is cleverly designed to achieve both fast charging performance and long cycle life.

[0066] The first annealing treatment forms MoO2 on the substrate surface, the second annealing treatment forms MoO2 and Mo2N on the substrate surface, and the passivation treatment forms MoO2 on the substrate surface. x -Mo y N.

[0067] Furthermore, the temperature of the first reaction is 75 to 85°C, including but not limited to a point value of any one of 75°C, 77°C, 79°C, 81°C, 83°C or 85°C, or a range between any two.

[0068] Furthermore, the time for the first reaction is 4 to 6 hours, including but not limited to a point value of any one of 4 hours, 5 hours, or 6 hours, or a range of values ​​between any two.

[0069] Furthermore, the temperature of the first drying treatment is 70 to 80°C, including but not limited to a point value of any one of 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, or a range between any two.

[0070] Furthermore, the calcination temperature is 800–1300℃, including but not limited to any one of 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, or 1300℃, or a range between any two. Calcination at a certain temperature results in a matrix material with good stability.

[0071] Furthermore, the heating rate of the calcination is 1 to 3 °C / min, including but not limited to a point value of any one of 1 °C / min, 2 °C / min or 3 °C / min or a range between any two.

[0072] Furthermore, the calcination time is 2 to 5 hours, including but not limited to the point value of any one of 2 hours, 3 hours, 4 hours or 5 hours or the range value between any two.

[0073] Furthermore, the calcination is carried out under an inert atmosphere. The inert atmosphere includes, but is not limited to, argon.

[0074] Furthermore, the molar ratio of the ammonia water to the formaldehyde is 1:(1 to 3), including but not limited to 1:1, 1:2 or 1:3.

[0075] Furthermore, the molar ratio of the ammonium heptamolybdate to the matrix is ​​1:(1 to 5), including but not limited to 1:1, 1:2, 1:3, 1:4 or 1:5.

[0076] Furthermore, the temperature of the second drying process is 75 to 85°C, including but not limited to a point value of any one of 75°C, 77°C, 79°C, 81°C, 83°C or 85°C or a range between any two.

[0077] Furthermore, the second drying process takes 10 to 14 hours, including but not limited to a point value of any one of 10 hours, 11 hours, 12 hours, 13 hours, or 14 hours, or a range between any two.

[0078] Furthermore, the temperature of the first annealing treatment is 250 to 400°C, including but not limited to a point value or a range between any two of 250°C, 280°C, 300°C, 330°C, 350°C, 380°C, or 400°C.

[0079] Furthermore, the first annealing process takes 1 to 3 hours, including but not limited to a point value of 1 hour, 2 hours, or 3 hours, or a range of values ​​between any two.

[0080] Furthermore, the heating rate of the first annealing treatment is 4 to 6 °C / min, including but not limited to a point value of any one of 4 °C / min, 5 °C / min or 6 °C / min or a range between any two.

[0081] Furthermore, the first annealing process is carried out under an inert atmosphere.

[0082] Furthermore, the temperature of the second annealing treatment is 480 to 800°C, including but not limited to any one of 480°C, 490°C, 500°C, 510°C, 520°C, 550°C, 580°C, 600°C, 630°C, 650°C, 680°C, 700°C, 730°C, 750°C, 780°C or 800°C, or a range between any two.

[0083] Furthermore, the second annealing process takes 1 to 3 hours, including but not limited to a point value of 1 hour, 2 hours, or 3 hours, or a range of values ​​between any two.

[0084] Furthermore, the heating rate of the second annealing treatment is 1 to 3 °C / min, including but not limited to a point value of any one of 1 °C / min, 2 °C / min or 3 °C / min or a range between any two.

[0085] Furthermore, during the second annealing process, the volume ratio of ammonia to hydrogen is (90-99):(1-10), including but not limited to 90:10, 93:7, 95:5, 97:3 or 99:1.

[0086] Furthermore, the passivation time is 1 to 3 hours, including but not limited to a point value of any one of 1 hour, 2 hours, or 3 hours, or a range of values ​​between any two.

[0087] Furthermore, during the passivation process, the volume ratio of nitrogen to oxygen is (90-99):(1-10), including but not limited to 90:10, 93:7, 95:5, 97:3 or 99:1.

[0088] Another aspect of this application relates to a negative electrode sheet, comprising the aforementioned negative electrode material or a negative electrode material prepared by the method for preparing the aforementioned negative electrode material.

[0089] Another aspect of this application relates to a secondary battery, including the aforementioned negative electrode.

[0090] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0091] Example 1

[0092] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0093] (1) Dissolve 0.6 mL of NH3·H2O in water and mix it with ethanol at a volume ratio of 1:1. Stir at 40°C for 30 minutes.

[0094] (2) Add phenolic resin and 37wt% formaldehyde solution to the mixed solvent and stir at 80℃ for 5 hours; the molar ratio of ammonia to formaldehyde is 1:1;

[0095] (3) The precipitate was separated by centrifugation, washed three times with water and ethanol, and then dried at 80°C for 12 hours to obtain a brownish-yellow polymer powder.

[0096] (4) Disperse phenolic resin powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of phenolic resin to graphite is 10:90. Stir at 75°C until the solvent is completely evaporated.

[0097] (5) Transfer the dried sample to a high-temperature tube furnace, heat the sample to 800°C at a heating rate of 1°C min-1, and hold for 2 hours to obtain the carbon material Gr@HC under the protection of argon.

[0098] (6) (NH4)6Mo7O 24 • 4H₂O powder is dissolved in deionized water, and Gr@HC is added and mixed with the above solution under continuous stirring. (NH₄)₆Mo₇O 24 The molar ratio of 4H2O and Gr@HC is 1:3. The resulting mixed solution is dried at 80°C for 12 hours to form AMT@Gr@HC powder.

[0099] (7) The prepared powder was heated under an argon flow at 5°C for 1 minute. -1 The heating rate was annealed in a tube furnace for 1 hour at an annealing temperature of 370°C to form MoO. x @Gr@HC powder;

[0100] (8) A mixed gas of NH3 and H2 with a volume ratio of 95:5 was introduced into a tube furnace and annealed at 500℃ for 1.5h at a heating rate of 2℃ / min. -1 MoO is formed at this time. x -Mo y N@Gr@HC powder;

[0101] (9) After cooling the obtained powder to room temperature, passivate it in a mixture of N2 and O2 with a volume ratio of 95:5 for 2 hours.

[0102] Example 2

[0103] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0104] (1)~(4) are the same as in Example 1;

[0105] (5) Transfer the dried sample to a high-temperature tube furnace, heat the sample to 900°C at a heating rate of 1°C min-1, and hold for 3 hours to obtain the carbon material Gr@HC under the protection of argon.

[0106] (6)~(9) Same as Example 1.

[0107] Example 3

[0108] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0109] (1) Same as Example 1;

[0110] (2) Add o-aminophenol and 37% formaldehyde solution to the mixed solvent and stir at 80°C for 5 hours; the molar ratio of ammonia to formaldehyde is 1:2;

[0111] (3) Same as Example 1;

[0112] (4) Disperse o-aminophenol powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of o-aminophenol to graphite is 20:80. Stir at 75°C until the solvent is completely evaporated.

[0113] (5) Transfer the dried sample to a high-temperature tube furnace and heat the sample to 1000℃ at a heating rate of 1℃ / min. -1 The process was carried out for 4 hours to obtain the carbon material Gr@HC under the protection of argon.

[0114] (6)~(9) Same as Example 1.

[0115] Example 4

[0116] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0117] (1) Same as Example 1;

[0118] (2) Add o-aminophenol and 37wt% formaldehyde solution to the mixed solvent and stir at 80℃ for 5 hours; the molar ratio of ammonia to formaldehyde is 1:3;

[0119] (3) Same as Example 1;

[0120] (4) Disperse o-aminophenol powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of o-aminophenol to graphite is 30:70. Stir at 75°C until the solvent is completely evaporated.

[0121] (5) Transfer the dried sample to a high-temperature tube furnace and heat the sample to 1100℃ at a heating rate of 1℃ / min. -1 The process was carried out for 4 hours to obtain the carbon material Gr@HC under the protection of argon.

[0122] (6)~(9) Same as Example 1.

[0123] Example 5

[0124] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0125] (1) Same as Example 1;

[0126] (2) Add epoxy resin and 37wt% formaldehyde solution to the mixed solvent and stir at 80℃ for 5 hours; the molar ratio of ammonia to formaldehyde is 1:1.5;

[0127] (3) Same as Example 1;

[0128] (4) Disperse epoxy resin powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of epoxy resin to graphite is 40:60. Stir at 75°C until the solvent is completely evaporated.

[0129] (5) Transfer the dried sample to a high-temperature tube furnace and heat the sample to 1200℃ at a heating rate of 1℃ / min. -1 The process was carried out for 4 hours to obtain the carbon material Gr@HC under the protection of argon.

[0130] (6)~(9) Same as Example 1.

[0131] Example 6

[0132] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0133] (1) Same as Example 1;

[0134] (2) Add epoxy resin and 37wt% formaldehyde solution to the mixed solvent and stir at 80℃ for 5 hours; the molar ratio of ammonia to formaldehyde is 1:2.5;

[0135] (3) Same as Example 1;

[0136] (4) Disperse epoxy resin powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of epoxy resin to graphite is 50:50. Stir at 75°C until the solvent is completely evaporated.

[0137] (5) Transfer the dried sample to a high-temperature tube furnace and heat the sample to 1300℃ at a heating rate of 1℃ / min. -1 The process was carried out for 4 hours to obtain the carbon material Gr@HC under the protection of argon.

[0138] (6)~(9) Same as Example 1.

[0139] Example 7

[0140] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0141] (1) Same as Example 1;

[0142] (2) Add phenolic resin and 37wt% formaldehyde solution to the mixed solvent and stir at 85℃ for 4 hours; the molar ratio of ammonia to formaldehyde is 1:2;

[0143] (3) The precipitate was separated by centrifugation, washed three times with water and ethanol, and then dried at 80°C for 12 hours to obtain a brownish-yellow polymer powder.

[0144] (4) Disperse phenolic resin powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of phenolic resin to graphite is 10:90. Stir at 75°C until the solvent is completely evaporated.

[0145] (5) Transfer the dried sample to a high-temperature tube furnace and heat the sample to 1300℃ at a heating rate of 2℃ / min. -1 The process was carried out for 5 hours to obtain the carbon material Gr@HC under argon protection.

[0146] (6) (NH4)6Mo7O 24 • 4H₂O powder is dissolved in deionized water, and Gr@HC is added and mixed with the above solution under continuous stirring. (NH₄)₆Mo₇O 24 The molar ratio of 4H2O and Gr@HC is 1:5. The resulting mixed solution is dried at 80°C for 12 hours to form AMT@Gr@HC powder.

[0147] (7) The prepared powder was heated under an argon flow at 4°C for 1 minute. -1 The heating rate was annealed in a tube furnace for 3 hours at an annealing temperature of 400℃ to form MoO. x @Gr@HC powder;

[0148] (8) A mixed gas of NH3 and H2 with a volume ratio of 99:1 was introduced into a tube furnace and annealed at 520℃ for 1 hour at a heating rate of 3℃ / min. -1 MoO is formed at this time. x -Mo y N@Gr@HC powder;

[0149] (9) After cooling the obtained powder to room temperature, passivate it in a mixture of N2 and O2 with a volume ratio of 90:10 for 1 hour.

[0150] Example 8

[0151] The method for preparing the negative electrode material provided in this embodiment includes the following steps:

[0152] (1) Same as Example 1;

[0153] (2) Add phenolic resin and 37wt% formaldehyde solution to the mixed solvent and stir at 75°C for 6 hours; the molar ratio of ammonia to formaldehyde is 1:3;

[0154] (3) The precipitate was separated by centrifugation, washed three times with water and ethanol, and then dried at 80°C for 12 hours to obtain a brownish-yellow polymer powder.

[0155] (4) Disperse phenolic resin powder and graphite in water and mix with ethanol at a volume ratio of 1:1. The mass ratio of phenolic resin to graphite is 10:90. Stir at 75°C until the solvent is completely evaporated.

[0156] (5) Transfer the dried sample to a high-temperature tube furnace and heat the sample to 1250°C at a heating rate of 3°C / min. -1 The process was carried out for 4 hours to obtain the carbon material Gr@HC under the protection of argon.

[0157] (6) (NH4)6Mo7O 24 • 4H₂O powder is dissolved in deionized water, and Gr@HC is added and mixed with the above solution under continuous stirring. (NH₄)₆Mo₇O 24 The molar ratio of 4H2O and Gr@HC is 1:1. The resulting mixed solution is dried at 80°C for 12 hours to form AMT@Gr@HC powder.

[0158] (7) The prepared powder was heated under an argon flow at 6°C for 6 min. -1 The heating rate was annealed in a tube furnace for 2 hours at an annealing temperature of 250°C to form MoO. x @Gr@HC powder;

[0159] (8) A mixed gas of NH3 and H2 with a volume ratio of 90:10 was introduced into a tube furnace and annealed at 480℃ for 3 hours at a heating rate of 1℃ / min. -1 MoO is formed at this time. x -Mo y N@Gr@HC powder;

[0160] (9) After cooling the obtained powder to room temperature, passivate it in a mixture of N2 and O2 with a volume ratio of 99:1 for 3 hours.

[0161] Example 9

[0162] The only difference between this embodiment and Embodiment 1 is that the mass ratio of phenolic resin to graphite is 5:95.

[0163] Example 10

[0164] The only difference between this embodiment and Embodiment 1 is that in step 5, the sample is heated to 1400°C.

[0165] Example 11

[0166] The only difference between this embodiment and Embodiment 1 is that the heating rate in step 5 is 5°C / min.

[0167] Example 12

[0168] The only difference between this embodiment and Embodiment 1 is that in step 6, (NH4)6Mo7O 24 The molar ratio of 4H2O to Gr@HC is 1:8.

[0169] Example 13

[0170] The only difference between this embodiment and Embodiment 1 is that the heating rate in step 7 is 2°C / min. -1 .

[0171] Example 14

[0172] The only difference between this embodiment and Embodiment 1 is that the annealing temperature in step 7 is 200°C.

[0173] Example 15

[0174] The only difference between this embodiment and Embodiment 1 is that the annealing temperature in step 8 is 450°C.

[0175] Example 16

[0176] The only difference between this embodiment and Embodiment 1 is that in step 8, the volume ratio of NH3 to H2 is 50:50.

[0177] Comparative Example 1

[0178] The method for preparing the negative electrode material provided in this comparative example includes the following steps:

[0179] (NH4)6Mo7O 24 • 4H₂O powder is dissolved in deionized water, and Gr is added and mixed with the above solution under continuous stirring, (NH₄)₆Mo₇O 24 The molar ratio of 4H₂O and Gr was 1:3; the resulting mixed solution was dried at 80 °C for 12 hours to form AMT@Gr powder. Next, the prepared powder was dried under an argon flow at 5 °C for 1 minute. -1 The heating rate was annealed in a tube furnace for 1 hour at an annealing temperature of 370°C to form MoO. x @Gr powder. Subsequently, an NH3 / H2 (95:5) mixed gas was introduced into a tube furnace and annealed at 500°C for 1.5 h at a heating rate of 2°C / min. -1MoON@Gr powder is formed at this point. After cooling the obtained powder to room temperature, it is passivated in a N2 / O2 (95:5) mixed gas for 2 hours.

[0180] Comparative Example 2

[0181] The method for preparing the negative electrode material provided in this comparative example includes the following steps:

[0182] (NH4)6Mo7O 24 • 4H₂O powder is dissolved in deionized water, and HC is added and mixed with the above solution under continuous stirring. (NH₄)₆Mo₇O 24 The molar ratio of 4H₂O and HC was 1:3. The resulting mixed solution was dried at 80°C for 12 hours to form AMT@HC powder. Next, the prepared powder was heated under an argon stream at 5°C for [time missing]. -1 The heating rate was annealed in a tube furnace for 1 hour at an annealing temperature of 370°C to form MoO. x @HC powder. Subsequently, an NH3 / H2 (95:5) mixed gas was introduced into a tube furnace and annealed at 500°C for 1.5 h at a heating rate of 2°C / min. -1 MoON@HC powder is formed at this point. After cooling the obtained powder to room temperature, it is passivated in a N2 / O2 (95:5) mixed gas for 2 hours.

[0183] Comparative Example 3

[0184] The method for preparing the negative electrode material provided in this comparative example includes the following steps:

[0185] 0.6 mL of NH3·H2O was dissolved in water and mixed with ethanol at a 1:1 volume ratio, and stirred at 40 °C for 30 min. Then, o-aminophenol and 37% formaldehyde solution were added to the mixed solvent, and stirred at 80 °C for 5 h. The precipitate was separated by centrifugation, washed three times with water and ethanol, and then dried at 80 °C for 12 h to obtain a brownish-yellow powder. Next, the polymer powder and 70% asphalt were dispersed in water and mixed with ethanol at a specific volume ratio, and stirred at 75 °C until the solvent was completely evaporated. The dried sample was then transferred to a high-temperature tube furnace. The sample was then heated to 1300 °C at a heating rate of 1 °C / min. -1 The process was carried out for 4 hours to obtain the carbon material Gr@HC. The entire process was conducted under an Ar atmosphere.

[0186] Comparative Example 4

[0187] The method for preparing the negative electrode material provided in this comparative example differs from that in Example 1 only in that step 9 is omitted.

[0188] Experimental Example

[0189] The negative electrode materials, conductive carbon (carbon black), and binder PVDF prepared in each embodiment and comparative example were mixed at a weight ratio of 80:10:10. The resulting slurry was stirred for 12 hours and then coated onto copper foil. The coated copper foil was heated under vacuum at 80°C for 12 hours. The resulting electrode was cut into circular sheets with a diameter of 12 mm. The mass loading of the half-cell negative electrode was controlled at 0.32-0.54 mg / cm³. -2 The negative electrode area capacity of the half-cell is controlled at 0.95 mAh cm⁻¹. -2 .

[0190] For the half-cell (CR2025) assembly, the negative electrode prepared above was used as the working electrode, while the lithium metal electrode was used as the counter electrode. The battery was assembled in an argon-filled glove box (H2O, O2 < 0.1 ppm). The electrolyte was 50 μL of 1 M LiPF6 dissolved in EC, DMC, and EMC in a 1:1:1 volume ratio.

[0191] The electrochemical performance of the half-cell was tested, and the results are shown in Table 1.

[0192] Table 1 Electrochemical performance of the negative electrode material

[0193] As can be seen from Table 1, the negative electrode material provided in this application has cycle stability and fast charging performance.

[0194] Although this application has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of this application; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application; therefore, this means that all such substitutions and modifications that fall within the scope of this application are included in the appended claims. Industrial applicability

[0195] The negative electrode material provided in this application has a modified material layer on a graphite and hard carbon blended matrix. The blending of graphite and hard carbon significantly improves the rate performance of the material, achieving a trade-off between energy density and power performance. The modified material layer possesses high ionic conductivity and low Li- content. + The diffusion barrier facilitates the formation of Li between graphite and electrolyte. +This modified layer exhibits rapid conduction and a low desolvation energy barrier, effectively preventing solvent molecule co-intercalation and mitigating failure issues such as electrolyte reduction side reactions, structural stripping, and lithium plating on the graphite surface during fast charging and long cycling. It also possesses a high Young's modulus, enabling it to withstand the accumulated internal stress and volume expansion caused by the vigorous movement of lithium ions, significantly improving transport kinetics and achieving a balance between fast charging performance and long cycle life for the graphite anode. Furthermore, the modified material layer reduces parasitic solvent reduction reactions, effectively solving interfacial side reactions and lithium plating problems in Gr anodes under fast charging conditions, significantly improving the fast charging capability of Gr anodes while maintaining a long cycle life.

Claims

1. A negative electrode material, characterized in that, include: The substrate and the decorative material layer disposed on the surface of the substrate; The matrix includes: hard carbon and graphite coating the hard carbon; The chemical formula of the modifying material in the modifying material layer is MoO. x -Mo y N, where x takes values ​​from 2 to 3 and y takes values ​​from 1 to 2.

2. The negative electrode material according to claim 1, characterized in that, Includes at least one of the following technical features: (1) The mass ratio of the hard carbon to the graphite is (10-50):(50-90); (2) The thickness of the modified material layer is 500 nm to 1 μm; (3) The hard carbon includes at least one of phenolic resin, epoxy resin or o-aminophenol.

3. The method for preparing the negative electrode material as described in claim 1 or 2, characterized in that, Includes the following steps: (a) The mixture containing ammonia, hard carbon and formaldehyde is subjected to a first reaction, and the precipitate is collected; (b) The dispersion containing the precipitate and graphite is subjected to a first drying treatment and calcination to obtain the matrix; (c) The mixture containing ammonium heptamolybdate and the matrix is ​​subjected to a second drying treatment and a first annealing treatment; the product obtained from the first annealing treatment is subjected to a second annealing treatment under an atmosphere of ammonia and hydrogen. (d) The product obtained from the second annealing treatment is cooled and passivated under a nitrogen and oxygen atmosphere to obtain the negative electrode material.

4. The method for preparing the negative electrode material according to claim 3, characterized in that, Includes at least one of the following technical features: (1) The molar ratio of the ammonia water to the formaldehyde is 1:(1-3); (2) The temperature of the first reaction is 75-85℃; (3) The time for the first reaction is 4 to 6 hours.

5. The method for preparing the negative electrode material according to claim 3, characterized in that, Includes at least one of the following technical features: (1) The calcination temperature is 800-1300℃; (2) The heating rate of the calcination is 1 to 3 °C / min; (3) The calcination time is 2 to 5 hours.

6. The method for preparing the negative electrode material according to claim 3, characterized in that, Includes at least one of the following technical features: (1) The molar ratio of the ammonium heptamolybdate to the matrix is ​​1:(1-5); (2) The temperature of the first annealing treatment is 250-400℃; (3) The first annealing process takes 1 to 3 hours; (4) The heating rate of the first annealing treatment is 4 to 6 °C / min.

7. The method for preparing the negative electrode material according to claim 3, characterized in that, Includes at least one of the following technical features: (1) The temperature of the second annealing treatment is 480-800℃; (2) The second annealing process takes 1 to 3 hours; (3) The heating rate of the second annealing treatment is 1 to 3 °C / min; (4) When performing the second annealing treatment, the volume ratio of ammonia to hydrogen is (90-99):(1-10).

8. The method for preparing the negative electrode material according to claim 3, characterized in that, Includes at least one of the following technical features: (1) The passivation time is 1 to 3 hours; (2) When the passivation is performed, the volume ratio of nitrogen to oxygen is (90-99):(1-10).

9. A negative electrode sheet, characterized in that, The negative electrode material includes the negative electrode material according to claim 1 or 2, or the negative electrode material according to any one of claims 3 to 8.

10. A secondary battery, characterized in that, Includes the negative electrode sheet as described in claim 9.

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