Negative active material, method for preparing the same, and use thereof

Abstract

This application provides a negative electrode active material, its preparation method, and its application. The negative electrode active material comprises a carbon material containing carbon-oxygen double bonds; and in the C1s spectrum measured by X-ray photoelectron spectroscopy of the carbon material, the area ratio of the carbon-oxygen double bonds in the C1s spectrum is ≥8%. The aforementioned carbon material possesses both high metal ion storage capacity and low powder resistivity.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to negative electrode active materials, their preparation methods, and applications. Background Technology

[0002] Carbon materials are commonly used anode active materials in rechargeable batteries, such as hard carbon and graphite. However, for sodium-ion batteries, the single graphite structure makes it difficult to store sodium, and sodium ions are difficult to intercalate / deintercalate between single graphite layers. Hard carbon is more mature in the application of anodes in sodium-ion batteries, and its sodium storage capacity is significantly higher than that of graphite, but hard carbon has poor rate performance. Summary of the Invention

[0003] Therefore, embodiments of this application provide a negative electrode active material, its preparation method, and its application. The negative electrode active material includes a carbon material with a high proportion of carbon-oxygen double bonds, which allows the carbon material to possess both high metal ion storage capacity and low powder resistivity.

[0004] The first aspect of this application provides a negative electrode active material, including a carbon material containing carbon-oxygen double bonds; and in the C1s spectrum of the carbon material measured by X-ray photoelectron spectroscopy, the area ratio of the carbon-oxygen double bonds in the C1s spectrum is ≥8%.

[0005] Among the above-mentioned anode active materials, carbon materials contain carbon-oxygen double bonds, and their area ratio in the C1s spectrum is ≥8%. The large amount of oxygen atom doping can expose more active sites in carbon materials to improve capacity, while also effectively improving the electronic conductivity of carbon materials, thereby improving the rate performance of carbon materials.

[0006] The second aspect of this application provides a method for preparing a negative electrode active material, including:

[0007] A first carbon source and a second carbon source are mixed and sintered under a protective atmosphere to form a carbon material, thereby obtaining a negative electrode active material. The first carbon source includes coal and / or bitumen; the second carbon source includes a solution or paste of biomass material with a glucose molecular configuration, and / or a resin material; the resin material is liquid at least at a temperature below or equal to 100°C; the biomass material with a glucose molecular configuration can undergo caramelization at 140°C-250°C.

[0008] The carbon material contains carbon-oxygen double bonds; in the C1s spectrum of the carbon material measured by X-ray photon energy dispersive spectroscopy, the area of ​​the carbon-oxygen double bonds in the C1s spectrum accounts for ≥8%.

[0009] The above preparation method has high reliability, high flexibility, and high production efficiency, making it suitable for large-scale industrial production.

[0010] A third aspect of this application provides a negative electrode sheet, comprising the negative electrode active material provided in the first aspect of this application, or comprising the negative electrode active material prepared by the preparation method provided in the second aspect of this application. By employing the negative electrode active material provided in this application, the negative electrode can be used to provide a secondary battery with both high capacity and superior rate performance.

[0011] A fourth aspect of this application provides a secondary battery, including the negative electrode provided in the third aspect of this application. Due to the inclusion of the negative electrode provided in this application, the secondary battery can achieve higher capacity and better rate performance.

[0012] A fifth aspect of this application provides an electrical device including the secondary battery provided in the fourth aspect of this application. Because it incorporates the secondary battery provided in this application, the electrical device has good market prospects. Attached Figure Description

[0013] Figure 1 The X-ray diffraction (XRD) spectra of the carbon materials in Example 1 and Comparative Example 2 of this application are shown.

[0014] Figure 2 The XRD spectra of the carbon materials in Example 4 and Comparative Example 3 of this application are shown.

[0015] Figure 3 The image shows a scanning electron microscope (SEM) image of the carbon material in Comparative Example 3.

[0016] Figure 4 Here is a SEM image of the carbon material in Example 4 of this application;

[0017] Figure 5A and Figure 5B The images show the isothermal adsorption-desorption curves and the NLDFT method differential-integral logarithmic pore volume and pore size distribution diagrams for Example 4.

[0018] Figure 5C and Figure 5D The images show the isothermal adsorption-desorption curves and the NLDFT method differential-integral logarithmic pore volume and pore size distribution diagrams for Example 5.

[0019] Figure 6A The peak fitting results are for the C1s spectrum of Comparative Example 3;

[0020] Figure 6B The peak fitting results are for the C1s spectrum of Example 4. Detailed Implementation

[0021] This application provides an anode active material, including a carbon material containing carbon-oxygen double bonds; and in the C1s spectrum of the carbon material obtained by X-ray photoelectron spectroscopy (XPS), the area ratio of the carbon-oxygen double bonds in the C1s spectrum is ≥8%.

[0022] The negative electrode active material provided in this application contains carbon-oxygen double bonds in its carbon material, and the area ratio of carbon-oxygen double bonds in the C1s spectrum is ≥10%. The large number of oxygen atoms doped into the carbon material exposes more active sites to increase capacity, while also effectively improving the electronic conductivity of the carbon material, thereby enhancing its rate performance. In some embodiments of this application, the powder resistivity of the carbon material at 25 MPa pressure is ≥15 S / cm.

[0023] In this embodiment of the application, when performing XPS testing on carbon materials, 10 mg or more of carbon materials are compressed into tablets to form 3 mm × 3 mm samples, which are then placed in an XPS analyzer for three fine scans (specific conditions include: pass energy of 40 eV, scan step size of 0.1 eV / step, and spectral reception time of 10 min) to obtain the C1s spectrum of the carbon materials. The C1s spectrum is then fitted with peaks according to Gaussian and Lorentz distributions. The peak position of the -C = O peak is 287.4 eV, and the area ratio of the -C = O peak in the C1s spectrum is calculated.

[0024] In the embodiments of this application, the area ratio of carbon-oxygen double bonds in the C1s spectrum can be, for example, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, etc. If the content of carbon-oxygen double bonds is too low, the doping amount of oxygen in the carbon material will be too low, resulting in insufficient doping sites and limited improvement on the capacity and electronic conductivity of the carbon material.

[0025] In some embodiments of this application, the area ratio of carbon-carbon single bonds in the C1s spectrum is ≥70%, for example, it can be 70%-85%. It is understood that carbon-carbon single bonds can represent the presence of amorphous carbon and graphitic carbon structures. Sufficient carbon-carbon single bonds indicate that the carbon material contains a sufficient amount of electrochemically active material, enabling the carbon material to exhibit its intrinsic electrochemical properties. This also limits the doping amount of heteroatoms (e.g., oxygen atoms), effectively avoiding further loss of electrochemical performance due to structural defects by restricting the doping amount of heteroatoms within a certain range. It should be noted that when performing peak segmentation on the C1s spectrum, the peak position of the carbon-carbon single bond is 284.8 eV.

[0026] In some embodiments of this application, an energy dispersive spectroscopy (EDS) coupled with a scanning electron microscope (SEM) is used to test the carbon material. Within any 50 μm × 50 μm area of ​​the carbon material, the mass content of carbon is ≥92.4%, and the mass content of nitrogen is ≥0.5%. This allows the carbon material to exhibit its intrinsic electrochemical properties; furthermore, appropriate nitrogen doping also helps to improve the capacity and electronic conductivity of the carbon material. Specifically, within any 50 μm × 50 μm area of ​​the carbon material, the mass content of carbon can be, for example, 92.4%-98%, and the mass content of nitrogen can be, for example, 0.5%-1%.

[0027] In some embodiments of this application, the mass ratio of carbon to oxygen is ≥17:1. In some specific embodiments, the mass ratio of carbon to oxygen is (17-33):1, specifically, for example, 17:1, 18:1, 20:1, 22:1, 25:1, 28:1, 30:1, 32:1, 33:1, etc. Since electrochemically active carbon materials are generally obtained by high-temperature sintering under a protective atmosphere, the carbon-to-oxygen ratio is largely inherited from the oxygen content in the system during high-temperature sintering. Controlling the ratio within the above-mentioned range also controls the oxygen content during high-temperature sintering within a suitable range, which can maintain the structural stability of the material during high-temperature sintering (e.g., the structural stability of the formed carbon rings). Thus, under the same high-temperature sintering conditions, a relatively better heteroatom doping level can be maintained, which is beneficial to improving the electronic conductivity and capacity of the final carbon material. In this embodiment, EDS-SEM can be used to test the mass content of carbon and oxygen elements within any 50μm×50μm area of ​​the carbon material, and then the ratio of their mass contents can be calculated.

[0028] In some embodiments of this application, the carbon material includes amorphous carbon and graphite-like domain crystallites. Amorphous carbon can provide storage sites for metal ions (e.g., sodium ions), while graphite-like domain crystallites can achieve interlayer sodium intercalation to a certain extent, thus enabling the carbon material to have a higher capacity. Unlike the structure of graphite crystallites, graphite domain crystallites refer to structures formed by stacking many two or more graphite layers under a transmission electron microscope (TEM), exhibiting short-range order but long-range disorder, and forming a structure with disordered stacking or twisted arrangement within the field of view. It should be noted that the carbon material in the embodiments of this application is doped with oxygen atoms. Oxygen atoms can be doped in graphite-like domain crystallites or in amorphous carbon; all graphite-like domain crystallites may be doped with oxygen atoms, or only some graphite-like domain crystallites may be doped with oxygen atoms. In some specific embodiments of this application, the carbon material includes a mixture of oxygen-doped graphite-like domain crystallites and oxygen-doped amorphous carbon.

[0029] In some embodiments of this application, the interplanar spacing of the (002) crystal planes of the carbon material is 0.352 nm to 0.415 nm. A relatively large (002) crystal plane spacing makes the carbon material with the above parameters more conducive to interlayer metal ion storage and metal ion insertion / extraction, thereby improving capacity. Specifically, the (002) crystal plane spacing of the carbon material can be, for example, 0.352 nm, 0.355 nm, 0.360 nm, 0.365 nm, 0.370 nm, 0.375 nm, 0.380 nm, 0.385 nm, 0.390 nm, 0.395 nm, 0.400 nm, 0.405 nm, 0.410 nm, 0.415 nm, etc. In this embodiment, X-ray diffraction can be used to test the X-ray diffraction curve of carbon material, and then Bragg's formula can be used to calculate the interplanar spacing of the (002) crystal plane of carbon material, d(002)=nλ / 2sinθ, where θ represents the angle (diffraction angle) between the incident X-ray and the (002) crystal plane, λ represents the wavelength of the X-ray, and n represents the diffraction order, where n=1. If a copper target (λ = 0.154056 nm) is used for XRD, then the 2θ corresponding to the (002) crystal plane is 21.4°-25.3°; specifically, the value of 2θ can be, for example, 25.3°, 25.1°, 24.7°, 24.3°, 24°, 23.7°, 23.3°, 23.1°, 22.8°, 22.5°, 22.2°, 21.9°, 21.6°, or 21.4°. If a molybdenum target is used, those skilled in the art can perform the conversion based on Bragg's formula and the wavelength of the radiation from the molybdenum target.

[0030] In some embodiments of this application, the La value of the graphite-like domain crystallites is 2 nm-2.8 nm, and the Lc value is 2.9 nm-4 nm. La is the average width of the graphite-like domain crystallites along the a-axis, and Lc is the thickness of the graphite-like domain crystallites stacked along the c-axis. La (nm) = 1.84λ / (β1cosθ1), Lc (nm) = 0.89λ / (β2cosθ2); where λ is the wavelength of the incident X-rays; β1 and θ1 are the half-width at half-maximum (WHM) and diffraction angle of the (002) diffraction peak in the XRD pattern of the carbon material, respectively; β2 and θ2 are the half-width at half-maximum (WHM) and diffraction angle of the (100) diffraction peak in the XRD pattern of the carbon material, respectively. Controlling the La and Lc values ​​of the graphite-like domain crystallites within the above ranges is beneficial for further improving the capacity performance and electrochemical kinetics of the carbon material.

[0031] In some embodiments of this application, the carbon material is in particulate form.

[0032] In some embodiments of this application, the carbon material includes primary particles and secondary particles. It is understood that secondary particles refer to aggregates of secondary particles. The primary particles of the carbon material include amorphous carbon and graphite-like domain microcrystals, and in the secondary particles, at least some adjacent primary particles are connected by amorphous carbon. Thus, the primary particles themselves can exhibit high capacity and high electronic conductivity. Furthermore, the secondary particles also possess a conductive network composed of primary particles and the amorphous carbon between them, which can further enhance the electronic conductivity of the carbon material, specifically manifested as lower powder resistivity and better rate performance. In the embodiments of this application, the structure of the aforementioned secondary particles can be characterized using SEM.

[0033] In some embodiments of this application, the particle size distribution of the particulate carbon material is in the range of 0.8 μm to 82 μm. In some specific embodiments, the particle size D50 of the particulate carbon material is 2 μm to 7 μm. This allows the length of the sodium ion insertion / extraction particle to be controlled within a small range, facilitating rapid insertion / extraction of active ions. Furthermore, it allows the specific surface area of ​​the carbon material to be controlled within a suitable range. In the embodiments of this application, particle size D50 refers to the particle size corresponding to a cumulative volume percentage of 50% for the carbon material particles, which can be measured using a laser particle size analyzer. Similarly, the particle size distribution of the carbon material particles can also be obtained using a laser particle size analyzer.

[0034] In some embodiments of this application, the carbon material has a porous structure. In some specific embodiments, the carbon material is a porous particle. The total pore volume of the carbon material is 0.01 mL / g-0.05 mL / g, and the pore size distribution is in the range of 0.5 nm-200 nm. Macropores (pore size > 50 nm) and mesopores (pore size 2 nm-50 nm) facilitate the intercalation / deintercalation of metal ions, especially sodium ions, and also facilitate the transport of metal ions within the carbon material. Micropores (pore size < 2 nm) facilitate the storage of metal ions. A suitable pore size distribution can simultaneously optimize the storage of metal ions (e.g., sodium ions), the transport of metal ions within the carbon material particles, and the intercalation / deintercalation of metal ions, thereby optimizing the electrochemical performance of the carbon material. Furthermore, a suitable total pore volume can provide sufficient storage space and channels for metal ion transport, deintercalation / intercalation, and also control the specific surface area of ​​the carbon material within a suitable range. When used in batteries, this reduces the risk of side reactions with other substances in the battery (e.g., electrolytes), facilitating capacity utilization and improving first-cycle efficiency. Specifically, the total pore volume of the carbon material can be, but is not limited to, 0.01 mL / g, 0.02 mL / g, 0.03 mL / g, 0.04 mL / g, 0.05 mL / g, etc. In the embodiments of this application, the gas adsorption-desorption curve of the carbon material is tested. The NLDFT method is used to differentiate and integrate the gas adsorption curve of the carbon material to obtain its total pore volume and pore size distribution. Specifically, the carbon material is placed in a gas adsorption-desorption tester, such as a nitrogen adsorption-desorption test, and the degassing time is maintained at ≥120 min and the degassing temperature at ≥200℃ during the test to obtain the adsorption-desorption curve of the carbon material, thereby obtaining the total pore volume and pore size distribution of the carbon material.

[0035] In some embodiments of this application, the total volume of pores (micropores) with a pore size ≤ 2 nm in the carbon material accounts for 10%-70% of the total pore volume of the carbon material. This provides ample storage space for metal ions and reserves suitable metal ion transport channels, thus ensuring a high capacity of the carbon material. Specifically, the total volume of pores with a pore size ≤ 2 nm can account for 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., of the total pore volume of the carbon material.

[0036] In some specific embodiments of this application, the total pore volume of the carbon material is 0.01 mL / g-0.05 mL / g, the pore size is distributed in the range of 0.5 nm-200 nm, and the sum of the volumes of pores with a pore size ≤ 2 nm accounts for 10%-70% of the total pore volume of the carbon material.

[0037] In some embodiments of this application, the specific surface area of ​​the carbon material is 1.08 m². 2 / g-35m 2 / g. In some specific embodiments, the specific surface area of ​​the carbon material is 2m². 2 / g-8m 2 / g. This facilitates the deintercalation / intercalation of metal ions in carbon materials, especially sodium ions, and also helps reduce side reactions, improving the capacity and initial coulombic efficiency of the carbon material. In the embodiments of this application, the specific surface area of ​​the carbon material can be calculated based on its gas adsorption-desorption curve and combined with the BET model. Specifically, the specific surface area of ​​the carbon material can be, for example, 2m². 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g, 10m 2 / g、12m 2 / g, 15m 2 / g、18m 2 / g、20m 2 / g、25m 2 / g、30m 2 / g、35m 2 / g etc.

[0038] In some embodiments of this application, the compaction density of the carbon material is 0.8 g / cm³. 3 -1.2g / cm 3 In some specific embodiments, the carbon material is in granular form, and the compacted density of the carbon material is 0.8 g / cm³. 3 -1.2g / cm 3 In other words, the risk of breakage or other defects in particulate carbon materials is relatively small or nonexistent at the aforementioned compaction density, which is beneficial for providing a battery with higher energy density. Specifically, the compaction density of the carbon material can be, but is not limited to, 0.8 g / cm³. 3 0.9g / cm 3 1.0g / cm 3 1.1g / cm 3 1.2g / cm 3 .

[0039] In some embodiments of this application, the Raman spectrum of carbon materials is I D / I G The value is 0.9-1.84; where, the I D / I G The peak intensity ratio of the D peak and the G peak in the Raman spectrum of the carbon material is given, wherein the Raman shift of the D peak is at 1300 cm⁻¹. -1 -1360cm -1 Within the range, the Raman shift of the G peak is at 1580 cm⁻¹.-1 -1600cm -1 Within the range. In this embodiment, the Raman test is performed using a laser light source with a wavelength of 532 nm or 785 nm. The carbon material I... D / I G A value controlled within the above range indicates that the carbon material has a relatively higher degree of disorder and more defect sites for storing metal ions, which is beneficial to ensuring a high capacity of the carbon material. Specifically, the I value of carbon materials... D / I G Values ​​can be, for example, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, etc.

[0040] This application also provides a method for preparing a carbon material, which can be used to prepare the aforementioned carbon material provided in this application embodiment. The preparation method includes:

[0041] S01. A first carbon source and a second carbon source are mixed and sintered under a protective atmosphere to form a carbon material, thereby obtaining a negative electrode active material; wherein, the first carbon source includes coal and / or pitch; the second carbon source includes a solution or paste of biomass material with a glucose molecular configuration, and / or, a resin material; the resin material is liquid at least at a temperature below or equal to 100°C; the biomass material with a glucose molecular configuration can undergo caramelization at 140°C-250°C; in the embodiments of this application, the mass content of carbon in the pitch is 80%-90%, the mass content of hydrogen is 10%-15%, and the mass content of high molecular weight hydrocarbons and other non-metallic derivatives (oxygen, sulfur, nitrogen) is <1%; coal includes major elements such as carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, with the total mass content of carbon, hydrogen, and oxygen being approximately 95%, and the carbon content accounting for 50%-90% of the coal mass.

[0042] Carbon materials contain carbon-oxygen double bonds; in the C1s spectrum of carbon materials measured by X-ray photon energy dispersive spectroscopy, the area of ​​carbon-oxygen double bonds in the C1s spectrum is ≥8%.

[0043] In some embodiments of this application, the solvent in the solution of the above-mentioned biomass material includes, but is not limited to, solvents containing nitrogen (e.g., acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, etc.) and solvents containing oxygen (e.g., water, alcohol, ester, ketone, etc.).

[0044] Sintering the first and second carbon sources under a protective atmosphere can form a carbon material with an electrochemically active structure. More importantly, the second carbon source is liquid and, due to its raw material properties, also has a certain degree of viscosity. Therefore, the mixture of the first and second carbon sources has good homogeneity and stability, resulting in a more uniform structure of the carbon material. Furthermore, during subsequent sintering, the second carbon source can crosslink with the first carbon source to form a better conductive network. In addition, coal, asphalt, and biomass materials with glucose molecular configurations all contain oxygen. When the resin is an oxygen-containing resin, it can also provide a large amount of oxygen. Due to the adhesion, curing, or crosslinking between the first and second carbon sources, the raw materials can increase the oxygen content of the system. Moreover, oxygen is not completely removed during sintering. Therefore, oxygen can be doped into the carbon material (e.g., doped into carbon rings), thereby forming an appropriate amount of carbon-oxygen double bonds in the final carbon material to improve its capacity and electronic conductivity.

[0045] Specifically, when the second carbon source is a solution or paste of biomass material with a glucose molecular configuration, it has a certain viscosity (e.g., 100 cP-330 cP) and can bind the first carbon source, resulting in good homogeneity and high stability in the mixture of the first and second carbon sources. Furthermore, during the subsequent sintering process, the biomass material with the glucose molecular configuration can undergo caramelization and cross-linking with the molecules of the first carbon source, ensuring that the sintered material maintains a relatively uniform state and completes oxygen doping, forming a conductive network in the final carbon material. In some embodiments of this application, the second carbon source is selected from an aqueous solution of biomass material with a glucose molecular configuration or a paste formed with water. It is understood that the sintering temperature of the carbon material is higher than 100°C. At this temperature, as the temperature increases, the water vapor released can form pores in the sintered material, resulting in more uniform heating and optimizing the electrochemical performance of the final carbon material. In some embodiments of this application, biomass materials having a glucose molecular configuration include, but are not limited to, at least one of starch, glucose, sucrose and maltose. These materials can not only be sintered to obtain amorphous carbon, but they can also decompose and gasify during the sintering process. They can also play a role in creating pores in the sintered material, further optimizing the uniformity of heating of the sintered material.

[0046] In some specific embodiments, the biomass material with a specific glucose molecular configuration is starch, such as corn starch, wheat starch, rice starch, potato starch, cassava starch, etc. Starch itself has a relatively high degree of disorder, which can play a better role in oxygen doping and the construction of conductive networks in carbon materials during subsequent sintering. In this case, the second carbon source can be a non-Newtonian fluid of starch or a paste obtained by heat treatment. In the embodiments of this application, starch and water can be mixed at a relatively low temperature (e.g., 25℃-30℃) to obtain a non-Newtonian fluid; or they can be mixed at 50℃-80℃ to obtain a paste. In this case, the mass ratio of starch to water in the above-mentioned non-Newtonian fluid or paste is 1:(0.5-20).

[0047] In some embodiments of this application, the biomass material with a glucose molecular configuration accounts for 5%-60% of its mass in the solution. In some specific embodiments, the biomass material with a glucose molecular configuration accounts for 10%-20% of its mass in the solution. Thus, the solution has a suitable viscosity, which is beneficial for both uniform mixing with the first carbon source and for the adhesion and solidification of the first carbon source. Specifically, the mass percentage of the biomass material with a glucose molecular configuration in its solution can be, but is not limited to, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, and 60%.

[0048] When the second carbon source is a resin material, as the temperature rises, the molecular chains of the resin cross-link with the molecules in the first carbon source, achieving a similar effect of fixing the first carbon source. This results in a mixture of the first and second carbon sources with good homogeneity and high stability. Furthermore, during subsequent sintering, the cross-linking between the resin and the first carbon source molecules maintains a relatively uniform state, and a conductive network can be formed in the final carbon material. In this embodiment, the aforementioned liquid resin material can be the resin material itself in a liquid state, or it can be a resin composition comprising a solvent and resin dissolved in the solvent. Carbon dioxide is also generated during resin carbonization, which creates pores in the sintered material. It is understood that the solvent is generally an organic solvent, which can vaporize during sintering. In this case, the solvent can also play a role in creating pores in the sintered material.

[0049] In some embodiments of this application, the resin material includes, but is not limited to, at least one of phenolic resin, epoxy resin, polyester resin, polyamide resin, phenolic resin, and polyacrylonitrile. In some specific embodiments, the oxygen-containing resin material includes phenolic resin, which is beneficial for improving the yield of carbon materials and reducing their cost.

[0050] In some embodiments of this application, the resin material that is liquid at a temperature at least below or equal to 100°C is a resin composition, the resin composition comprising a resin and a solvent, wherein the resin accounts for 10%-80% of the resin composition by mass. In some specific embodiments, the resin accounts for 10%-30% of the resin composition by mass. Similarly, the second carbon source has a suitable viscosity, which is conducive to uniform mixing with the first carbon source, and also has a certain viscosity, which is conducive to cross-linking and curing of its molecules with the molecules in the first carbon source. The mass percentage of the oxygen-containing resin in the resin composition may be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%. In some embodiments of this application, the second carbon source is a solution or paste of the biomass material having a glucose molecular configuration, and the mass ratio of the first carbon source to the biomass material having a glucose molecular configuration is (1-10):1. This helps to ensure the content of carbon-oxygen double bonds in the carbon material. Specifically, the mass ratio of the first carbon source to the biomass material with the glucose molecular configuration can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc. In other embodiments of this application, the second carbon source is the resin material, and the mass ratio of the first carbon source to the resin is (1-10):1. In some specific embodiments, the mass ratio of the first carbon source to the resin is (5-10):1, more preferably (7-10):1. This helps to ensure the content of carbon-oxygen double bonds in the carbon material. Specifically, the mass ratio of the first carbon source to the resin can be, but is not limited to, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc. In some embodiments of this application, the second carbon source is a mixture of a solution or paste of the biomass material with a glucose molecular configuration and the resin material, wherein the mass ratio of the first carbon source to the sum of the masses of the biomass material with a glucose molecular configuration and the resin is (1-10):1. During the sintering process in step S01, the first carbon source is conducive to the formation of graphite-like domain crystallites, and the second carbon source is conducive to the formation of amorphous carbon. In some embodiments of this application, controlling the mass ratio of the first carbon source and the second carbon source within the above-mentioned range facilitates the obtaining of a carbon material with a mixed and dispersed distribution of amorphous carbon and graphite-like domain crystallites. Furthermore, the uniform mixing of the first carbon source and the second carbon source can effectively suppress the size growth of the graphite-like domain crystallites, thereby facilitating the obtaining of graphite-like crystallites with La values ​​of 2nm-2.8nm and Lc values ​​of 2.9nm-4nm.

[0051] In some specific embodiments of this application, primary and secondary particles of carbon material formed by graphite-like domain microcrystals and amorphous carbon are obtained by sintering, and at least some of the adjacent primary particles in the secondary particles are connected by amorphous carbon. In this way, a conductive network can be constructed in the secondary particles to improve the electronic conductivity of the carbon material.

[0052] In this embodiment, the mixing process of the first carbon source and the second carbon source is not limited; for example, it can be mechanical stirring.

[0053] In some embodiments of this application, after mixing the first carbon source and the second carbon source, the mixture is further subjected to a heat treatment at a temperature of 40℃-350℃ for a duration of 2h-48h. Stirring may also be performed during the heat treatment. Specifically, when the second carbon source is a solution or paste of biomass material with a glucose molecular configuration, the preferred heating temperature is 40℃-240℃, and the preferred holding time is 10h-28h. This promotes mixing and improves the uniformity of the mixture. In some specific embodiments, the heating temperature is further limited to 140℃-240℃. This allows for caramelization of the biomass material with a glucose molecular configuration and water evaporation, further improving the stability of the mixture and creating pores, which is more conducive to subsequent sintering.

[0054] When the second carbon source is a resin material, the preferred heating temperature is 290℃-310℃, and the preferred holding time is 10h-28h. This not only facilitates mixing of the two materials, resulting in a more homogeneous mixture, but also introduces oxygen vacancies into the mixture, further hindering the excessive graphitization of the first carbon source and ensuring superior electrochemical performance of the final carbon material. It should be noted that when the second carbon source includes a material with high oxygen content (e.g., oxygen-containing resin, the aforementioned biomass material), the above heat treatment can be carried out in an oxygen-free environment; when the second carbon source is a material with low oxygen content (e.g., non-oxygen-containing resins such as polyacrylonitrile), the above heat treatment can be carried out in an oxygen-containing atmosphere to introduce more oxygen.

[0055] In some embodiments of this application, the softening temperature of the asphalt is 27℃-280℃. This facilitates the uniform mixing of the first and second carbon sources. In some specific embodiments, the softening temperature of the asphalt is 70℃-100℃. In this case, when the second carbon source is an aqueous solution of biomass material with a glucose molecular configuration or a paste formed with water, the asphalt, whose softening point is close to the boiling point of water, can rapidly melt and crosslink with the water vapor after it evaporates, further improving the homogeneity of the mixture. The above process can occur during sintering or during the heat treatment after mixing.

[0056] In some embodiments of this application, the coal includes, but is not limited to, lignite, coking coal, and anthracite, with coking coal being preferred. Coking coal has a moderate carbon content and impurities are easily removed. Alternatively, in some specific embodiments, the coal is selected from anthracite with an ash content of <10%, and more preferably, anthracite with an ash content of <2%.

[0057] In some embodiments of this application, the particle size of the asphalt and coal is in the range of 1 μm to 30 μm. This facilitates the uniform dispersion of the first and second carbon sources.

[0058] In some embodiments of this application, the sintering temperature under a protective atmosphere is 900℃-1600℃, and the holding time is 1h-12h. In some specific embodiments, the sintering temperature is 1000℃-1300℃, and the holding time is 4h-6h. This temperature is conducive to the formation of graphite-like domain microcrystals and also to the formation of amorphous carbon. In the embodiments of this application, the protective atmosphere may be, but is not limited to, a nitrogen atmosphere, an argon atmosphere, etc.

[0059] In some embodiments of this application, the temperature is increased to 900℃-1600℃ at a rate of 1℃ / min-15℃ / min under a protective atmosphere. In some specific embodiments, the heating rate is 1℃ / min-5℃ / min. This helps to reduce defect structures in graphite-like domain crystallites, thereby improving the first cycle efficiency of the negative electrode active material.

[0060] In some embodiments of this application, after step S01, the material to be sintered is cooled and then crushed to obtain carbon material. The crushing process described above can be a process well known to those skilled in the art, and this application does not limit it.

[0061] This application also provides a negative electrode sheet, comprising the carbon material provided in this application embodiment, or the carbon material prepared by the preparation method provided in this application embodiment. Because it uses the carbon material provided in this application embodiment, the negative electrode can be used to provide a material with both high capacity and superior rate performance.

[0062] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector, wherein the negative active material layer includes the aforementioned negative active material and a binder.

[0063] In some embodiments of this application, the aforementioned negative electrode active material also includes silicon-based negative electrode materials, phosphorus-based negative electrode materials, and any other carbon materials known in the art capable of de-intercalating / intercalating metal ions, etc., and this application does not impose any restrictions on these.

[0064] In some specific embodiments, the aforementioned negative electrode material layer also contains a conductive agent. In the embodiments of this application, the aforementioned negative electrode current collector can be any current collector known in the art suitable for negative electrodes. Exemplarily, the aforementioned current collector can be, but is not limited to, aluminum foil, carbon-coated aluminum foil, etc.

[0065] In this embodiment, the adhesive can be any adhesive known in the art suitable for the negative electrode. For example, the adhesive includes, but is not limited to, styrene-butadiene rubber (SBR).

[0066] In the embodiments of this application, the conductive agent described above can be any conductive agent known in the art. Exemplarily, the conductive agent includes, but is not limited to, at least one of Super P, acetylene black, graphene, and carbon nanotubes.

[0067] This application also provides a secondary battery, including the negative electrode provided in this application embodiment. Due to the inclusion of the negative electrode provided in this application embodiment, the secondary battery can achieve higher capacity and better rate performance.

[0068] In some embodiments of this application, the secondary battery is a sodium-ion battery. The secondary battery can be a liquid battery using a liquid electrolyte, a solid battery using a solid electrolyte, or a semi-solid battery.

[0069] In some embodiments of this application, the aforementioned secondary battery includes a positive electrode, a negative electrode, and an electrolyte and a separator disposed between the positive and negative electrode.

[0070] In this embodiment of the application, the positive electrode can be any positive electrode known in the art.

[0071] This application also provides an electrical device, including the secondary battery provided in this application embodiment. Because it incorporates the secondary battery provided in this application embodiment, this electrical device has good market prospects.

[0072] In some embodiments of this application, the aforementioned electrical equipment includes, but is not limited to, vehicles and consumer electronics. Among these, the aforementioned vehicles include, but are not limited to, new energy vehicles and electric bicycles.

[0073] The technical solution of this application will be further described in detail below with reference to several embodiments.

[0074] Example 1

[0075] Dissolve 10 parts by weight of starch in 5 parts by weight of water and stir evenly at 60°C. Add 10 parts by weight of medium-temperature asphalt (softening point is 180°C) and mix for 30 minutes. Collect the mixture and place it in a tube furnace under a protective atmosphere (specifically N2 atmosphere) for sintering. Specifically, raise the temperature to 1250°C at a heating rate of 2°C / min and hold for 4 hours. After cooling, crush to obtain carbon material.

[0076] Example 2

[0077] Dissolve 10 parts by weight of starch in 50 parts by weight of water and stir evenly in water at 80°C to form a viscous rice paste. Add 20 parts by weight of high-temperature asphalt (softening point of 250°C) and mix for 30 minutes. Collect the mixture and place it in an Ar atmosphere tube furnace for sintering. Specifically, raise the temperature to 1050°C at a heating rate of 0.5°C / min and hold for 6 hours. After cooling, crush to obtain carbon material.

[0078] Example 3

[0079] Dissolve 10 parts by weight of starch in 10 parts by weight of water and stir evenly at 90°C to form a viscous rice paste. Add 30 parts by weight of anthracite with ash content <2% and stir for 30 minutes. Collect the mixture and place it in an Ar atmosphere tube furnace for sintering. Specifically, heat the temperature to 1350°C at a rate of 1°C / min and hold for 2 hours. After cooling, crush the mixture to obtain carbon material.

[0080] Example 4

[0081] 90 parts by weight of asphalt with a softening point of 280℃ and 10 parts by weight of phenolic resin solution (solid content of 10 wt.%) were placed in a stirrer and stirred for 30 min. The mixture was collected and heated in a muffle furnace at 280℃ for 24 h in an air atmosphere. After cooling and crushing, a precursor was obtained. The precursor was then placed in a tube furnace in an N2 atmosphere for high-temperature sintering. The temperature was increased to 1250℃ at a heating rate of 2℃ / min and held for 4 h. After cooling, the precursor was crushed to obtain carbon material.

[0082] Example 5

[0083] 80 kg of asphalt with a softening point of 40°C was melted at 60°C. 20 kg of an adsorbed phenol resin solution (solid content 20 wt.%) was added and stirred for 30 min. The mixture was collected and heated in a muffle furnace at 180°C for 10 h in an air atmosphere. After cooling and crushing, a precursor was obtained. The precursor was then placed in an Ar atmosphere tube furnace for sintering, with the temperature increased to 1050°C at a heating rate of 0.5°C / min and held for 6 h. After cooling, the precursor was crushed to obtain carbon material.

[0084] Example 6

[0085] 90 parts by weight of medium-temperature asphalt with a softening point of 80℃ were added to 10 parts by weight of phenolic resin solution (solid content 10 wt.%) and mixed evenly. The mixture was collected and heated in a muffle furnace at 300℃ for 6 hours in air atmosphere. After cooling and crushing, a precursor was obtained. The precursor was then placed in a tube furnace in N2 atmosphere for high-temperature sintering. The temperature was increased to 1350℃ at a heating rate of 1℃ / min and held for 2 hours. After cooling, the precursor was crushed to obtain carbon material.

[0086] Example 7

[0087] The difference from Example 1 is that the mass ratio of starch to medium-temperature asphalt is 12:1. No solvent was added. After the powder was mixed and stirred evenly, it was heat-treated in an air atmosphere in a muffle furnace at 150°C for 6 hours. The mixture was collected after heating and placed in a tube furnace under a protective atmosphere (specifically N2 atmosphere) for sintering. Specifically, the temperature was increased to 1250°C at a rate of 2°C / min and held for 4 hours. After cooling, it was crushed to obtain carbon material.

[0088] Example 8

[0089] Dissolve 10 parts by weight of starch in 5 parts by weight of water and stir evenly at 60°C. Add 10 parts by weight of medium-temperature asphalt (softening point 180°C) and mix for 30 minutes. Collect the mixture and heat-treat it in an air atmosphere in a muffle furnace at 200°C for 3 hours. Then, place it in a tube furnace under a protective atmosphere (specifically N2 atmosphere) for sintering. Specifically, raise the temperature to 1250°C at a heating rate of 2°C / min and hold for 4 hours. After cooling, crush it to obtain carbon material.

[0090] Example 9

[0091] Dissolve 10 parts by weight of starch in 5 parts by weight of water and stir evenly at 60°C. Add 10 parts by weight of medium-temperature asphalt (softening point of 180°C) and mix for 30 minutes. Collect the mixture and heat-treat it in an air atmosphere in a muffle furnace at 250°C for 3 hours. Then, place it in a tube furnace under a protective atmosphere (specifically N2 atmosphere) for sintering. Specifically, raise the temperature to 1250°C at a heating rate of 2°C / min and hold for 4 hours. After cooling, crush it to obtain carbon material.

[0092] To highlight the beneficial effects of the embodiments of this application, the following comparative examples are provided.

[0093] Comparative Example 1

[0094] The tea seed shells were washed with pure water, filtered, and vacuum dried to obtain tea seed shells. The tea seed shells were then placed in a tube furnace and calcined for 2 hours at 3°C / min from room temperature to 600°C under an argon atmosphere. After grinding, the shells were passed through a 200-mesh sieve to obtain 200-mesh preliminary biomass carbon material. The preliminary biomass carbon material obtained in step (1) was placed in a 6 mol / L HCl solution and acid-treated for 5 hours under stirring. After filtration and drying, it was placed in a 30 wt% KOH solution and alkali-treated for 8 hours under stirring. After filtration and washing with deionized water until neutral, it was transferred to a vacuum drying oven and dried at 60°C for 12 hours to obtain pretreated biomass carbon material. The pretreated biomass carbon material obtained in step (2) was placed in a high-temperature tube furnace and calcined for 2 hours at 5°C / min from room temperature to 1100°C under an argon atmosphere to obtain second-calcined biomass carbon material. The obtained secondary calcined biomass carbon material was mixed with alkali at a mass ratio of 1:2 and then transferred to a tube furnace for a third calcination at 800°C from room temperature to 5°C / min for 1.5 hours to regulate and reorganize the pore structure of the material, resulting in modified biomass hard carbon material. The alkali used in the alkali mixing was K2CO3. The modified biomass hard carbon material was then poured into an asphalt coating solution, with the amount of asphalt controlled at 20 wt% of the total material mass. After mechanical stirring at 60°C for 6 hours (stirring speed of 300 rpm), it was dried for a second time at 80°C in a vacuum drying oven for 6 hours to obtain the precursor material. The asphalt coating solution was prepared by adding asphalt to tetrahydrofuran and mechanically stirring to ensure complete dissolution. The obtained precursor material was placed in a tube furnace and pre-carbonized at 350°C for 2 hours under an argon atmosphere at a temperature of 5°C / min, followed by carbonization at 1150°C for 6 hours at a temperature of 10°C / min to obtain the carbon material.

[0095] Comparative Example 2

[0096] 10g of strongly basic styrene cation exchange resin powder and 20g of asphalt powder were mixed to obtain a mixture. This mixture was then melt-blended at 280℃ for 6 hours to obtain a molten blend. The strongly basic styrene cation exchange resin powder had an average particle size of 12μm, and the asphalt powder had an average particle size of 15μm. The softening point of the asphalt powder was 250℃. Both the strongly basic styrene cation exchange resin and the asphalt were in powder form. Melting and blending them at 280℃ for 6 hours resulted in a strong... Basic styrene cation exchange resin is uniformly compounded with asphalt to form a network-like, structurally stable, and elastic molten mixture. The molten mixture is cooled and ball-milled to obtain a mixed powder with an average particle size of 15 μm. The mixed powder is then placed in a tube furnace under N2 atmosphere and heated to carbonize it by heating at a rate of 5 °C / min to 1500 °C and holding at 1500 °C for 2 hours to obtain a high-temperature carbide. The high-temperature carbide is then cooled to room temperature to obtain the carbon material.

[0097] Comparative Example 3

[0098] 90 parts by weight of asphalt with a softening point of 280℃ and 10 parts by weight of phenolic resin were placed in a mixer and stirred for 30 minutes. The mixture was collected and heated in a muffle furnace at 280℃ for 24 hours in an air atmosphere. After cooling and crushing, a precursor was obtained. The precursor was then placed in a tube furnace in an N2 atmosphere for high-temperature sintering. The temperature was increased to 1250℃ at a heating rate of 2℃ / min and held for 4 hours. After cooling, the precursor was crushed to obtain carbon material.

[0099] Result characterization

[0100] (1) XPS test: 10 mg or more of carbon material was compressed into tablets to form 3 mm × 3 mm samples. These tablets were then placed in an XPS analyzer for three fine scans (specific conditions included: pass energy of 40 eV, scan step size of 0.1 eV / step, and acquisition time of 10 min). The C1s spectrum of the carbon material was obtained. The C1s spectrum was then fitted with peaks according to Gaussian and Lorentz distributions. The area ratios of the -C=O peak and the C-C bond peak in the C1s spectrum were calculated. The results are summarized in Table 1. For some illustrations, please refer to Table 1. Figure 6A , Figure 6B .

[0101] (2) EDS-SEM Testing: Carbon materials from each embodiment and comparative example were prepared and subjected to area scanning EDS-SEM testing. The mass content of carbon, nitrogen, and the carbon-to-oxygen ratio within a 50μm × 50μm area were measured. The results are summarized in Table 2. SEM images of some carbon materials are shown below. Figure 3 , Figure 4 As shown.

[0102] (3) XRD testing: The carbon materials of each embodiment and comparative example were tested using an X-ray diffractometer. The working conditions were: tube voltage 40 kV, tube current 20 mA, Cu Kα target, λ = 0.154056 nm, graphite monochromator, step width 0.02°, and residence time 0.2 s. The results are summarized in Table 3. For some spectra, please refer to Table 3. Figure 1 , Figure 2 .

[0103] (4) Raman test: The Raman spectrum of carbon materials was tested using a laser with a wavelength of 532 nm. The results are summarized in Table 5.

[0104] (5) Nitrogen adsorption-desorption test: The carbon material was placed in a nitrogen adsorption-desorption tester. During the test, the degassing time was maintained at ≥120 min, the degassing temperature at ≥200℃, the saturated vapor pressure at 1.0396 bar, the equilibrium time at 120 s, the real-time equilibrium pressure percentage at 1%, the high-pressure equilibrium time extension factor at 5, and the low-pressure equilibrium time extension factor at 5. The adsorption-desorption curves of the carbon material were obtained. The pore size distribution results are summarized in Table 4. For some of the figures, please refer to Table 4. Figures 5A-5D .

[0105] (6) Electrochemical performance testing

[0106] Powder resistivity test: Under a pressure of 25 MPa, the four-probe method is used for testing. The excitation current is used to collect the voltage signal, and the thickness of the powder sample is measured at the same time. The data is then transmitted to the software segment to calculate the powder resistivity.

[0107] The carbon materials prepared in each embodiment and comparative example were used as the negative electrode active material, acetylene black as the conductive agent, and sodium carboxymethyl cellulose (CMC) and SBR as binders. They were mixed evenly in a mass ratio of negative electrode active material: acetylene black: CMC: SBR = 100:1:3.6:1.6, dried and pressed into negative electrode sheets to prepare the test battery negative electrode sheets. Each negative electrode sheet was dried in an oven at 80°C for 24 hours. The test battery was prepared using a sodium metal sheet as the negative electrode, glass fiber as the separator, and a mixed solution of 1 mol / L NaPF6 ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio = 1:1) as the electrolyte. The test battery was assembled in an argon-filled glove box to obtain the test batteries of each embodiment and comparative example.

[0108] Each test battery was set to the charging state with a charging current density of 0.1C (theoretical specific capacity set to 300mAh / g). After discharging to 0.005V, the initial discharge specific capacity was calculated: Initial discharge specific capacity (mAh / g) = Initial discharge capacity / Mass of active material. After resting for 10 minutes, the battery was charged to the cutoff voltage of 2V and then the operation was stopped. The initial charge specific capacity was then calculated: Initial charge specific capacity (mAh / g) = Initial charge capacity / Mass of active material. The initial coulombic efficiency = Initial discharge capacity / Initial charge capacity × 100%. The results are summarized in Table 6.

[0109] Table 1

[0110] Case carbon-carbon single bond carbon-oxygen double bond Example 1 75.3％ 10.3％ Example 2 82.28％ 10.8％ Example 3 82.61％ 11.4％ Example 4 81.76％ 10.9％ Example 5 83.46％ 12.3％ Example 6 84.1％ 10.1％ Example 7 84.93％ 8.07％ Example 8 80.41％ 10.9％ Example 9 81.33％ 10.5％ Comparative Example 1 87.23％ 4.35％ Comparative Example 2 89.61％ 4.67％ Comparative Example 3 88.94％ 4.78％

[0111] Table 2

[0112]

[0113] Table 3

[0114] Case d(002) / nm La / nm Lc / nm Example 1 0.408 2.071 3.035 Example 2 0.395 2.273 2.933 Example 3 0.388 2.052 3.168 Example 4 0.378 2.343 4.017 Example 5 0.381 2.328 3.713 Example 6 0.383 2.179 3.709 Example 7 0.391 2.773 3.395 Example 8 0.385 2.114 3.157 Example 9 0.384 2.244 3.477 Comparative Example 1 0.372 2.407 3.331

[0115] Table 4

[0116] Case Micropore percentage (%) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 16.83 2.43 Example 2 39.90 1.49 Example 3 15.53 2.51 Example 4 14.45 7.81 Example 5 10.71 5.04 Example 6 11.79 3.93 Example 7 15.74 3.53 Example 8 14.41 5.14 Example 9 14.56 6.07

[0117] Table 5

[0118] Sample number <![CDATA[I D / I G value]]> Example 1 1.84 Example 2 1.54 Example 3 1.33 Example 4 1.31 Example 5 1.45 Example 6 1.66 Example 7 1.51 Example 8 1.77 Example 9 1.74 Comparative Example 1 1.04 Comparative Example 2 1.01 Comparative Example 3 1.02

[0119] Table 6

[0120] Battery number First charge capacity mAh / g First Coulomb efficiency % Powder resistivity S / cm Example 1 341.5 89.8 16.5 Example 2 314.2 90.8 16.8 Example 3 338.8 91.2 16.9 Example 4 320.1 92.4 16.7 Example 5 314.2 90.8 17.7 Example 6 327.6 90.7 17.0 Example 7 312.9 90.9 17.2 Example 8 346.7 89.7 16.1 Example 9 342.4 90.1 16.4 Comparative Example 1 310.5 92.5 17.4 Comparative Example 2 308.2 91.7 18.2 Comparative Example 3 270.8 85.4 18.9

[0121] As can be seen from the data in Table 6, the negative electrode active material prepared in the embodiments of this application can simultaneously possess high initial charge capacity, high initial coulombic efficiency, and relatively low powder resistivity. Furthermore, comparing the data between the embodiments reveals that when the parameters during preparation are controlled within the range further suggested in this application, the structural parameters of the resulting carbon material are also within the range further suggested in this application. In this case, the electrochemical performance of the carbon material is relatively superior.

[0122] The above description is an exemplary embodiment of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A negative electrode active material, characterized in that, For use in secondary batteries, including carbon materials containing carbon-oxygen double bonds; and in the C1s spectrum of the carbon material measured by X-ray photoelectron spectroscopy, the area of ​​the carbon-oxygen double bonds in the C1s spectrum is ≥8%; The La of the graphite-like domain crystallite is 2 nm-2.8 nm, and the Lc of the graphite-like domain crystallite is 2.9 nm-4 nm; La is the average width of the graphite-like domain crystallite along the a-axis direction, and Lc is the thickness of the graphite-like domain crystallite stacked along the c-axis direction. The carbon material has a porous structure, and the sum of the volumes of pores with a diameter ≤2nm accounts for 10%-70% of the total pore volume of the carbon material. The carbon material was tested using an energy dispersive spectroscopy-scanning electron microscope. Within any 50μm×50μm area of ​​the carbon material, the mass content of carbon element was ≥92.4%, the mass content of nitrogen element was 0.5%-1%, and the mass content ratio of carbon element to oxygen element was (17-33):

1. The carbon material includes primary particles and secondary particles. The primary particles include amorphous carbon and graphite-like domain microcrystals. In the secondary particles, at least some adjacent primary particles are connected by amorphous carbon.

2. The negative electrode active material according to claim 1, characterized in that, The interplanar spacing of the (002) crystal plane of the carbon material is 0.352 nm to 0.415 nm.

3. The negative electrode active material according to claim 1 or 2, characterized in that, The carbon material has a porous structure; the total pore volume of the carbon material is 0.01 mL / g-0.05 mL / g, and the pore size is distributed in the range of 0.5 nm-200 nm.

4. The negative electrode active material according to claim 1 or 2, characterized in that, The specific surface area of ​​the carbon material is 1.08 m². 2 / g-35 m 2 / g; the compacted density of the carbon material is 0.8 g / cm³. 3 -1.2 g / cm 3 .

5. The negative electrode active material according to claim 1 or 2, characterized in that, The Raman spectrum of the carbon material I D / I G The value is 0.9-1.84; where, the I D / I G The peak intensity ratio of the D peak and the G peak in the Raman spectrum of the carbon material is given, wherein the Raman shift of the D peak is at 1300 cm⁻¹. -1 -1360cm -1 Within the range, the Raman shift of the G peak is at 1580 cm⁻¹. -1 -1600cm -1 Within the range.

6. A method for preparing a negative electrode active material, characterized in that, include: A first carbon source and a second carbon source are mixed, and the mixture is heated at a temperature of 40℃-350℃ for 2h-48h. Then, sintering is performed under a protective atmosphere to form a carbon material, yielding a negative electrode active material. The first carbon source includes coal and / or bitumen; the second carbon source includes a solution or paste of biomass material with a glucose molecular configuration, and / or a resin material; the resin material is liquid at a temperature below or equal to 100℃; the biomass material with a glucose molecular configuration can undergo caramelization at 140℃-250℃. Wherein, the second carbon source is a solution or paste of the biomass material having a glucose molecular configuration, and the mass ratio of the first carbon source to the biomass material having a glucose molecular configuration is (1-10):1; or, The second carbon source is the resin material, and the mass ratio of the first carbon source to the resin is (1-10):1; or, The second carbon source is a mixture of the solution or paste of the biomass material with glucose molecular configuration and the resin material, and the mass ratio of the first carbon source to the sum of the masses of the biomass material with glucose molecular configuration and the resin is (1-10):

1. The carbon material contains carbon-oxygen double bonds; in the C1s spectrum of the carbon material measured by X-ray photon energy dispersive spectroscopy, the area of ​​the carbon-oxygen double bonds in the C1s spectrum is ≥8%; The La of the graphite-like domain crystallite is 2 nm-2.8 nm, and the Lc of the graphite-like domain crystallite is 2.9 nm-4 nm; La is the average width of the graphite-like domain crystallite along the a-axis direction, and Lc is the thickness of the graphite-like domain crystallite stacked along the c-axis direction. The carbon material has a porous structure, and the sum of the volumes of pores with a diameter ≤2nm accounts for 10%-70% of the total pore volume of the carbon material. The carbon material was tested using an energy dispersive spectroscopy-scanning electron microscope. Within any 50μm × 50μm area of ​​the carbon material, the mass content of carbon was ≥92.4%, the mass content of nitrogen was 0.5%-1%, and the mass ratio of carbon to oxygen was (17-33):

1. The carbon material comprised primary particles and secondary particles. The primary particles included amorphous carbon and graphite-like domain microcrystals. In the secondary particles, at least some adjacent primary particles were connected by amorphous carbon. The negative electrode active material is used in secondary batteries.

7. The preparation method according to claim 6, characterized in that, The biomass material having a glucose molecular configuration includes at least one of starch, glucose, sucrose, and maltose; The resin material includes at least one of phenolic resin, epoxy resin, polyester resin, polyamide resin, phenolic resin, and polyacrylonitrile.

8. The preparation method according to claim 6 or 7, characterized in that, The biomass material with a glucose molecular configuration accounts for 5%-60% of its mass in the solution; And / or, A resin material that is liquid at a temperature at least below or equal to 100°C is a resin composition, the resin composition comprising an oxygen-containing resin and a solvent, wherein the oxygen-containing resin comprises 10%-80% by mass in the resin composition.

9. The preparation method according to claim 6 or 7, characterized in that, The softening temperature of the asphalt is 27℃-280℃.

10. The preparation method according to claim 6 or 7, characterized in that, The sintering temperature is 900℃-1600℃, and the holding time is 1h-12h.

11. A negative electrode sheet, characterized in that, It includes the negative electrode active material as described in any one of claims 1-5, or the negative electrode active material prepared by the preparation method according to any one of claims 6-10.

12. A secondary battery, characterized in that, Includes the negative electrode sheet as described in claim 11.

13. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 12.

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