Carbon negative electrode material, preparation method thereof, negative electrode sheet, sodium ion battery and electrical equipment

Abstract

The application provides a carbon negative electrode material, a preparation method thereof, a negative electrode sheet, a sodium ion battery and an electrical equipment. The carbon negative electrode material comprises hard carbon and a hetero-element dispersed in the interior of the hard carbon; and a hetero-element content distribution coefficient of the carbon negative electrode material is 25-175%. In the carbon negative electrode material, the hetero-element is fully and uniformly dispersed in the interior of the hard carbon, is uniformly distributed in the interior of the carbon material particle and is fully bonded with the carbon element, so that a large number of active sites are formed, the conductivity is improved, the hetero-element is in the interior of the carbon negative electrode material, the hard carbon physically separates the electrolyte, the side reaction of the hetero-element and the electrolyte is effectively reduced, and the capacity and the cycle performance of the negative electrode material are significantly improved.

Description

Technical Field

[0001] This invention relates to the technical field of sodium-ion batteries, and more particularly to a carbon anode material and its preparation method, anode sheet, sodium-ion battery, and electrical equipment. Background Technology

[0002] Sodium-ion batteries possess advantages such as low-temperature resistance, fast charging, high safety, low cost, and long lifespan. Their working principle is similar to that of lithium-ion batteries, making them a complementary or partial replacement for lithium-ion batteries. Furthermore, sodium resources are abundant on Earth, with the total amount of sodium salts being 500 times that of lithium salts, and their extraction costs are low. Therefore, sodium-ion battery systems have excellent development potential and market prospects for large-scale energy storage in the future. Hard carbon materials, due to their large interlayer spacing and advantages such as high capacity and low potential, are currently the main commercial anode material for sodium-ion batteries and a decisive factor in the large-scale application of sodium-ion batteries.

[0003] Currently, the core technological bottleneck in sodium-ion battery applications lies in the difficulty of increasing energy density, and one of the keys to improving energy density is enhancing the capacity performance of hard carbon materials. Hard carbon materials contain numerous defects and pores, resulting in low capacity performance for carbon anode materials. Furthermore, the disordered structure of hard carbon materials themselves causes deviations in electronic conductivity, affecting their fast-charging and power performance. Therefore, in some related technologies, the main technological bottleneck for using hard carbon in sodium-ion batteries is the difficulty in simultaneously achieving energy density and kinetic (fast charging, lifespan) performance. There are many methods to improve the performance of hard carbon materials, such as soft-hard carbon composites or heteroatom doping.

[0004] Soft and hard carbon composites combine the structural advantages of soft carbon (high order and good conductivity) and hard carbon (abundant closed pores and high plateau capacity) to achieve complementary performance. However, common soft and hard carbon composite methods directly use hard carbon sources and soft carbon sources. Hard carbon sources are limited to a few soluble or fusible carbon sources, the composite process is demanding and difficult to scale up, and the resulting carbon materials have small carbon layer spacing and low porosity, resulting in poor fast charging and lifespan performance of sodium-ion batteries made from them.

[0005] Heteroatom doping utilizes heteroatoms (such as N, P, S, etc.) to modify carbon materials, thereby increasing their defects and improving their capacity performance. However, conventional heteroatom doping methods involve directly mixing carbon materials and dopants in a solid state and sintering at high temperatures. The heteroatom elements are mainly doped onto the surface and open-pore regions of the carbon material, making it difficult for them to penetrate into the interior of the carbon particles. This results in a phenomenon where the carbon particles are "oversaturated with heteroatom elements on the surface and depleted in the inner layers" (e.g., ...). Figure 1 As shown in the figure, this limits the effect of "doping to improve capacity" of carbon materials, and impurities are prone to side reactions with electrolytes, leading to a decrease in the lifespan performance of carbon materials.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] This invention provides a carbon anode material and its preparation method, anode sheet, sodium-ion battery and electrical equipment, aiming to solve the technical problem that impurities are mainly doped on the surface and open area of ​​carbon materials and are difficult to penetrate into the interior of carbon particles, so that impurities can be fully and uniformly dispersed in the interior of the carbon anode material.

[0008] In a first aspect, the present invention provides a carbon anode material, the carbon anode material comprising hard carbon and heterogeneous elements dispersed within the hard carbon. Furthermore, the heterogeneous element content distribution coefficient of the carbon anode material is 25-175%.

[0009] Furthermore, the heteroelement content distribution coefficient of the carbon anode material is 50~150%.

[0010] Furthermore, the heteroelement content distribution coefficient of the carbon anode material is 75~125%.

[0011] Furthermore, the heteroelement includes any one or a combination of at least two of nitrogen, phosphorus, or sulfur.

[0012] Furthermore, the content of impurity elements in the carbon anode material is 0.4~5 wt%.

[0013] Furthermore, the carbon interlayer spacing of the carbon anode material is 0.37~0.39 nm.

[0014] Furthermore, the carbon anode material includes soft carbon dispersed within the hard carbon, and the soft carbon fills the pores of the hard carbon to form closed pores.

[0015] Furthermore, the closed pore volume of the carbon anode material is 0.04~0.3 cm³. 3 / g.

[0016] Furthermore, the compacted density of the 3T powder of the carbon anode material is 1.0~1.1 g / cm³. 3 .

[0017] Furthermore, the conductivity of the carbon anode material is 26~52 S / cm, preferably 42~50 S / cm.

[0018] Furthermore, the median particle size of the carbon anode material is 4~15 μm.

[0019] Furthermore, the true density of the carbon anode material is 1.56~2.06 g / cm³. 3 .

[0020] Furthermore, the specific surface area of ​​the carbon anode material is 1.5~8.0 m². 2 / g.

[0021] In a second aspect, the present invention provides a method for preparing a carbon anode material as described in the first aspect, the method comprising:

[0022] (1) The carbon source is pre-carbonized, crushed and pore-formed to obtain the first precursor;

[0023] (2) The first precursor is modified to obtain the second precursor;

[0024] (3) The second precursor and the asphalt doping solution are mixed and doped to obtain the third precursor; the asphalt doping solution includes a dopant and liquid asphalt.

[0025] (4) The third precursor is sintered to obtain the carbon anode material.

[0026] Further, in step (1), the carbon source includes any one or a combination of at least two of the following: plant-based carbon sources, sugar-based carbon sources, resin-based carbon sources, or polymer-based carbon sources.

[0027] Furthermore, the plant-based carbon source includes any one or a combination of at least two of the following: coconut shell, almond shell, pistachio shell, macadamia nut shell, jujube kernel shell, chestnut shell, hazelnut shell, peanut shell, walnut shell, peach kernel shell, cotton, wood, bamboo, sugarcane bagasse, straw, or lignin.

[0028] Furthermore, the carbohydrate carbon source includes any one or a combination of at least two of glucose, sucrose, maltose, lactose, fructose, starch, or cellulose.

[0029] Furthermore, the resin-based carbon source includes any one or a combination of at least two of phenolic resin, polyimide resin, polyester resin, polyaldehyde resin, polyolefin resin, or polyacrylic acid resin.

[0030] Furthermore, the polymeric carbon source includes any one or a combination of at least two of polyfurfuryl alcohol, polyaniline, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, natural rubber, or polyacrylonitrile.

[0031] Further, in step (1), the pre-carbonization temperature is 450~650℃, and the pre-carbonization holding time is 0.5~24 h.

[0032] Furthermore, in step (1), the pre-carbonization is carried out in an inert gas atmosphere.

[0033] Further, in step (1), the inert gas atmosphere in the pre-carbonization includes any one or a combination of at least two of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton atmosphere.

[0034] Furthermore, in step (1), the pre-carbonization is carried out in a carbonization furnace.

[0035] Further, in step (1), the carbonization furnace includes any one or a combination of at least two of the following: tube furnace, box furnace, pusher kiln or roller kiln.

[0036] Further, in step (1), the pulverization includes: pulverizing the pre-carbonized material to a median particle size of 3~15μm to obtain the pulverized pre-carbonized material.

[0037] Furthermore, in step (1), the equipment used for pulverization includes any one or a combination of at least two of the following: mechanical pulverizer, roller mill, air jet mill, or ball mill.

[0038] Further, in step (1), the pore-forming process includes: mixing the pulverized pre-carbonized material with a solid pore-forming agent and performing pore-forming treatment to obtain a solid pore-forming modified material.

[0039] Furthermore, the mass ratio of the pulverized pre-carbonized material to the solid pore-forming agent is 1:(0.5~3.0).

[0040] Furthermore, the solid pore-forming agent includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium oxide, or zinc chloride.

[0041] Further, in step (1), the temperature of the pore-forming treatment is 400~700℃, and the time of the pore-forming treatment is 0.25~24 h.

[0042] Furthermore, in step (1), the pore-forming process is carried out in an inert gas atmosphere and / or an oxygen-deficient atmosphere.

[0043] Further, in step (1), the inert gas atmosphere in the pore-forming process includes any one or a combination of at least two of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton atmosphere.

[0044] Further, in step (1), during the pore-forming process, the oxygen-deficient atmosphere is a gaseous atmosphere with an oxygen content ≤ 1 wt%;

[0045] Furthermore, in step (1), the pore-forming process further includes a purification process, which includes:

[0046] The solid-phase pore-forming modified material was washed with pure water until the pH was 8-10 to obtain purified product one; purified product one, acid and pure water were mixed and stirred to obtain purified product two; purified product two was washed with pure water until the pH was 4-8, and then solid-liquid separation and drying were performed to obtain the purified first precursor.

[0047] Further, in step (1), the acid in the purification process includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid or sulfuric acid.

[0048] Further, in step (2), the modification reaction includes: mixing the first precursor with an oxidizing acid solution to carry out a modification reaction to obtain a second precursor.

[0049] Further, in step (2), the mass ratio of the first precursor to the oxidizing acid solution is 1:(3~20).

[0050] Furthermore, in step (2), the oxidizing acid solution includes an oxidizing solute and an acid.

[0051] Further, in step (2), the oxidizing solute includes any one or a combination of at least two of potassium permanganate, potassium dichromate, potassium perchlorate, potassium hypochlorite, sodium permanganate, sodium dichromate, sodium perchlorate, sodium hypochlorite, or hydrogen peroxide.

[0052] Further, in step (2), the acid in the oxidizing acid solution includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, phosphoric acid, sulfuric acid or nitric acid; wherein the concentration of the acid is 30 to 95 wt%.

[0053] Furthermore, based on the total mass of the oxidizing acid solution as 100%, the oxidizing acid solution comprises, by mass percentage: 0.3-5% oxidizing solute, 3-10% acid, and the remainder is water.

[0054] Furthermore, in step (2), the temperature of the modification reaction is 50~100℃, and the time of the modification reaction is 0.5~24 h.

[0055] Further, in step (3), the doping treatment includes: mixing the second precursor and the asphalt dopant solution, first heating to 200~300℃ and holding for 3~10 h, then heating to 500~800℃ and holding for 0.5~5 h to obtain the third precursor.

[0056] Further, in step (3), the mass ratio of the second precursor to the asphalt dopant is (75~95):(25~5).

[0057] Further, in step (3), the mixing of the second precursor and the asphalt dopant liquid includes: adding the asphalt dopant liquid to the second precursor under low-speed stirring; wherein the speed of the low-speed stirring is 20~30 r / min.

[0058] Furthermore, in step (3), the heat preservation process is carried out under stirring; wherein the stirring speed is 100~500 r / min.

[0059] Furthermore, in step (3), the heat preservation process is carried out in an inert gas atmosphere.

[0060] Furthermore, in step (3), during the heat preservation process, the inert gas atmosphere includes any one or a combination of at least two of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton atmosphere.

[0061] Further, in step (3), the preparation step of the asphalt dopant liquid includes: heating and melting asphalt to obtain liquid asphalt; adding dopant to the liquid asphalt and stirring until dissolved to obtain the asphalt dopant liquid.

[0062] Furthermore, the asphalt dopant liquid includes a dopant and liquid asphalt in a mass ratio of (0.1~1):1.

[0063] Furthermore, the dopant includes any one or a combination of at least two of nitrogen, phosphorus, or sulfur sources.

[0064] Furthermore, the nitrogen source includes any one or a combination of at least two of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acids, or ammonium bicarbonate.

[0065] Furthermore, the phosphorus source includes any one or a combination of at least two of phosphorus trichloride, phosphorus pentoxide, triammonium phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, or phosphate esters.

[0066] Furthermore, the sulfur source includes any one or a combination of at least two of sulfur powder, thiourea, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, or cysteine.

[0067] Furthermore, in step (4), the sintering temperature is 1100~1400℃ and the sintering time is 0.25~10 h.

[0068] Furthermore, in step (4), the sintering is carried out in an inert gas atmosphere.

[0069] Further, in step (4), during the sintering process, the inert gas atmosphere includes any one or a combination of at least two of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton atmosphere.

[0070] Furthermore, in step (4), the sintering is carried out in a sintering furnace.

[0071] Further, in step (4), the sintering furnace includes any one or a combination of at least two of the following: tube furnace, box furnace, roller kiln or rotary furnace.

[0072] Thirdly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising the carbon negative electrode material as described in the first aspect.

[0073] Fourthly, the present invention provides a sodium-ion battery, the sodium-ion battery comprising the negative electrode sheet as described in the third aspect.

[0074] Fifthly, the present invention provides an electrical device, characterized in that the electrical device includes a sodium-ion battery as described in the fourth aspect.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] (1) In the carbon anode material of the present invention, the impurity elements are fully and uniformly dispersed in the interior of the hard carbon. They are evenly distributed in the interior of the carbon material particles and fully bonded with the carbon elements, thereby forming a large number of uniformly distributed active sites, which improves the conductivity while ensuring the "doping capacity improvement" effect of the carbon material. Moreover, the impurity elements are located inside the carbon anode material, and the hard carbon physically isolates the electrolyte, effectively reducing the side reactions between the impurity elements and the electrolyte, and significantly improving the capacity and cycle performance of the anode material.

[0077] (2) In the carbon anode material of the present invention, soft carbon is dispersed inside hard carbon, and in the presence of impurity elements, the soft and hard carbons are fully and uniformly composited. At the same time, the soft carbon plays a "pore-blocking" role, filling the pores of the hard carbon to form closed pores. Therefore, the resulting carbon anode material has the advantages of large interlayer spacing, many closed pores, and dense structure, which in turn makes the anode material exhibit advantages such as high capacity, high rate, and high compaction.

[0078] (3) The preparation method of the carbon anode material of the present invention involves pre-carbonizing the hard carbon source to remove tar components, and constructing a pore structure through pore modification; the modification reaction improves the porosity and the number of cross-linking functional groups to provide sites for the doping reaction, thereby obtaining a second precursor; then, based on the thermoplasticity (good fluidity when heated) of the soft carbon source, it is embedded into the hard carbon particles (second precursor) under heating; finally, through high-temperature reaction, the hard carbon microcrystals, soft carbon source and dopant catalyze the cross-linking reaction, and the nano-scale soft carbon and heterogeneous elements are dispersed in the hard carbon, thereby achieving a full and uniform composite between the soft and hard carbons; wherein, the second precursor provides the carbon skeleton, the soft carbon source molecules play a "pore-blocking" role (converting "open pores" into "closed pores"), and the dopant plays a catalytic role in the cross-linking of the hard carbon microcrystals and the soft carbon source. Attached Figure Description

[0079] To more clearly illustrate the solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0080] Figure 1 This is a schematic diagram illustrating the mechanism of existing heteroatom doping modification methods for carbon materials in the background art.

[0081] Figure 2 This is a schematic diagram of the structure of the carbon anode material described in this invention.

[0082] In this context, 100 represents impurities and 200 represents closed pores.

[0083] Figure 3 This is a flowchart illustrating the preparation process of the carbon anode material described in this invention.

[0084] Figure 4 This is a schematic diagram illustrating the mechanism of the heteroatom doping modification method for the carbon anode material described in this invention.

[0085] Figure 5A This is a schematic diagram of the line scan path of the cross section of the carbon anode material during the test of the distribution coefficient of impurity element content.

[0086] Figure 5B The graph shows the mass concentration (y) of impurities versus the linear sweep displacement (x) during the test of the distribution coefficient of impurity content.

[0087] Figure 6 The image is a scanning electron microscope (SEM) image of the carbon anode material provided in Example 1.

[0088] Figure 7 Scanning electron microscope image of the carbon anode material provided for Comparative Example 1.

[0089] Figure 8 The XRD patterns of the carbon anode materials provided in Example 1, Comparative Example 5, and Comparative Example 8 are shown.

[0090] Figure 9 Comparative diagrams of the microstructures of the carbon anode materials provided in Example 1 and Comparative Example 2.

[0091] In this context, 100 represents impurities and 200 represents closed pores.

[0092] Figure 10 The first charge-discharge curves of the carbon anode materials provided in Example 1, Comparative Example 1, and Comparative Example 2 are shown. Detailed Implementation

[0093] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0094] To address the technical problem that impurities are mainly doped on the surface and open-pore areas of carbon materials but have difficulty penetrating into the interior of carbon particles, embodiments of the present invention provide a carbon anode material, the carbon anode material comprising hard carbon and impurities dispersed within the hard carbon.

[0095] like Figure 2 As shown, the impurity element 100 is fully and uniformly dispersed inside the carbon anode material. It is evenly distributed inside the carbon material particles and fully bonded to the carbon elements, forming a large number of uniformly distributed active sites inside, ensuring the "doping capacity improvement" effect of the carbon material. Moreover, the impurity element is located inside the carbon anode material, and the hard carbon physically isolates the electrolyte, effectively reducing the side reactions between the impurity element and the electrolyte, and significantly improving the capacity and cycle performance of the carbon material.

[0096] In one embodiment, the impurity element content distribution coefficient of the carbon anode material is 25-175%, for example, it can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, etc.

[0097] In one embodiment, the heteroelement content distribution coefficient of the carbon anode material is 50~150%.

[0098] In one embodiment, the heteroelement content distribution coefficient of the carbon anode material is 75-125%.

[0099] In one embodiment, the heteroelement includes any one or a combination of at least two of nitrogen (N), phosphorus (P), or sulfur (S).

[0100] In one embodiment, the content of impurity elements in the carbon anode material is 0.4~5 wt%, for example, it can be 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4 wt%, etc.

[0101] In one embodiment, the carbon interlayer spacing of the carbon anode material is 0.37~0.39 nm, for example, it can be 0.37 nm, 0.372 nm, 0.374 nm, 0.376 nm, 0.378 nm, 0.38 nm, 0.382 nm, 0.384 nm, 0.386 nm, 0.388 nm, 0.39 nm, etc.

[0102] In one embodiment, the carbon anode material includes soft carbon dispersed within the hard carbon, and the soft carbon fills the pores of the hard carbon to form closed pores.

[0103] like Figure 2As shown, the carbon anode material includes closed pores 200, which are formed by soft carbon dispersed inside the hard carbon filling the pores of the hard carbon. Specifically, during the preparation of the carbon anode material, based on the thermoplasticity (good flowability when heated) of the soft carbon source, it is embedded into the interior of the hard carbon particles under heating. The soft carbon source molecules play a "pore-blocking" role, transforming "open pores" into "closed pores." In addition, during the preparation process, dopants catalyze the cross-linking of hard carbon microcrystals and soft carbon source, achieving a full and uniform composite between the hard and soft carbons.

[0104] In one embodiment, the closed pore volume of the carbon anode material is 0.04~0.3 cm³. 3 / g, for example, could be 0.04 or 0.06 cm 3 / g, 0.08 cm 3 / g, 0.10 cm 3 / g, 0.12 cm 3 / g, 0.14 cm 3 / g, 0.16 cm 3 / g, 0.18cm 3 / g, 0.20 cm 3 / g, 0.22 cm 3 / g, 0.24 cm 3 / g, 0.26 cm 3 / g, 0.28 cm 3 / g, 0.30 cm 3 / g etc.

[0105] In one embodiment, the 3T powder compaction density of the carbon anode material is 1.0~1.1 g / cm³. 3 For example, it could be 1.0 g / cm³. 3 1.01 g / cm 3 1.02 g / cm 3 1.03 g / cm 3 1.04 g / cm 3 1.05 g / cm 3 1.06 g / cm 3 1.07 g / cm 3 1.08 g / cm 3 1.09 g / cm 3 1.1 g / cm 3 wait.

[0106] In one embodiment, the conductivity of the carbon anode material is 26~52 S / cm, for example, it can be 26 S / cm, 30 S / cm, 36 S / cm, 40 S / cm, 46 S / cm, 50 S / cm, 52 S / cm, etc.

[0107] In one embodiment, the conductivity of the carbon anode material is 42~52 S / cm, for example, it can be 42 S / cm, 42.2 S / cm, 42.4 S / cm, 42.6 S / cm, 42.8 S / cm, 43 S / cm, 43.2 S / cm, 43.4 S / cm, 43.6 S / cm, 43.8 S / cm, 44 S / cm, 44.2 S / cm, 44.4 S / cm, 44.6 S / cm, 44.8 S / cm, 45 S / cm, 45.2 S / cm, 45.4 S / cm, 45.6 S / cm, 45.8 S / cm, 46 S / cm, 46.2 S / cm, 46.4 S / cm, 46.6 S / cm, 46.8 S / cm, 47 S / cm, 47.2 S / cm, 47.4 S / cm, 47.6 S / cm. S / cm, 47.8 S / cm, 48 S / cm, 48.2 S / cm, 48.4S / cm, 48.6 S / cm, 48.8 S / cm, 49 S / cm, 49.2 S / cm, 49.4 S / cm, 49.6 S / cm, 49.8 S / cm, 50S / cm, etc.

[0108] In this invention, a large number of impurity elements are distributed in the closed pore region, which significantly increases the electron cloud density of the closed pore, thereby increasing the powder conductivity of the carbon anode material to more than 42 S / cm, thereby enhancing the sodium storage activity of the closed pore, suppressing electrochemical polarization, and further improving the capacity performance of the carbon material.

[0109] In one embodiment, the median particle size of the carbon anode material is 4~15 μm, for example, it can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, etc.

[0110] In one embodiment, the true density of the carbon anode material is 1.56~2.06 g / cm³. 3 For example, it could be 1.56 g / cm³ 3 1.58 g / cm 3 1.60 g / cm3 1.62 g / cm 3 1.64 g / cm 3 1.66 g / cm 3 1.68 g / cm 3 1.70 g / cm 3 1.72 g / cm 3 1.74 g / cm 3 1.76 g / cm 3 1.78 g / cm 3 1.80 g / cm 3 1.82 g / cm 3 1.84 g / cm 3 1.86 g / cm 3 1.88 g / cm 3 1.90 g / cm 3 1.92 g / cm 3 1.94 g / cm 3 1.96 g / cm 3 1.98 g / cm 3 2.00 g / cm 3 2.02 g / cm 3 2.04 g / cm 3 2.06 g / cm 3 wait.

[0111] In one embodiment, the specific surface area of ​​the carbon anode material is 1.5~8.0 m². 2 / g, for example, could be 1.5 m 2 / g, 2.0 m 2 / g, 2.5 m 2 / g, 3.0 m 2 / g, 3.5 m 2 / g, 4.0 m 2 / g, 4.5 m 2 / g, 5.0 m 2 / g, 5.5 m 2 / g, 6.0m 2 / g, 6.5 m 2 / g, 7.0 m 2 / g, 7.5 m 2 / g、8.0 m 2 / g etc.

[0112] The present invention also provides a method for preparing a carbon anode material as described in the first aspect, the method comprising:

[0113] (1) The carbon source is pre-carbonized, crushed and pore-formed to obtain the first precursor;

[0114] (2) The first precursor is modified to obtain the second precursor;

[0115] (3) The second precursor and the asphalt doping solution are mixed and doped to obtain the third precursor; the asphalt doping solution includes a dopant and liquid asphalt.

[0116] (4) The third precursor is sintered to obtain the carbon anode material.

[0117] like Figure 3 As shown, the preparation method of the carbon anode material of the present invention involves: firstly, a first precursor with a porous structure and carbon microcrystals is prepared by pre-carbonization and pore-forming; then, low molecular weight carbon chains in the first precursor are removed by a modification reaction to increase cross-linking functional groups and porosity, resulting in a second precursor; next, the second precursor is mixed with asphalt dopant and doped under heating conditions to allow the soft carbon source and dopant to be fully adsorbed into the porous structure and matrix of the second precursor, resulting in a third precursor; finally, the material is sintered at high temperature to achieve a cross-linking reaction between the soft carbon source molecules, dopant, and hard carbon "carbon microcrystals", thus obtaining the carbon anode material.

[0118] In the preparation method described in this invention, based on the thermoplasticity (good flowability when heated) of the soft carbon source, the soft carbon source is embedded into the interior of hard carbon particles (a pre-treated, porous second precursor rich in cross-linking functional groups) through a synergistic process of pore-forming modification, modification reaction, and heating doping. The hard carbon microcrystals, soft carbon source, and dopants undergo a cross-linking reaction, and nanoscale soft carbon and heterogeneous elements are dispersed within the hard carbon, achieving a thorough and uniform composite between the soft and hard carbons. Specifically, the second precursor of this invention provides the carbon framework, the soft carbon source molecules play a "pore-blocking" role (converting "open pores" into "closed pores"), and the dopants enhance the cross-linking degree of the carbon microcrystals, catalyze and participate in the conversion of "open pores" into "closed pores," and improve the conductivity of the pore region. The resulting carbon anode material has advantages such as large interlayer spacing, numerous closed pores, and dense structure, exhibiting advantages such as high capacity, high rate capability, and high compaction.

[0119] Meanwhile, the carbon anode material of this invention employs a novel heteroatom doping method, such as... Figure 4As shown, the present invention uses molten soft carbon as a carrier during the heating process of doping treatment to transport the dopant into the interior of the carbon material particles. Through high-temperature doping, the impurity elements are uniformly distributed within the carbon material particles and fully bonded to the carbon elements, reducing side reactions between the impurity elements and the electrolyte, thereby significantly improving the capacity and cycle performance of the carbon material. Therefore, the preparation method described in this invention enables the dopant elements to fully undergo cross-linking reactions with the carbon microcrystals and soft carbon source, catalyzing the transformation from "open pores" to "closed pores," and allowing a large number of impurity elements to be distributed in the closed pore region to increase the electron cloud density of the closed pores. This effectively improves the powder conductivity of the carbon anode material, enhances the sodium storage activity of the closed pores, suppresses electrochemical polarization, and further improves the capacity performance of the carbon anode material.

[0120] In one embodiment, in step (1), the carbon source includes any one or a combination of at least two of plant-based carbon sources, sugar-based carbon sources, resin-based carbon sources, or polymer-based carbon sources.

[0121] In one embodiment, the plant-based carbon source includes any one or a combination of at least two of the following: coconut shell, almond shell, pistachio shell, macadamia nut shell, jujube kernel shell, chestnut shell, hazelnut shell, peanut shell, walnut shell, peach kernel shell, cotton, wood, bamboo, sugarcane bagasse, straw, or lignin.

[0122] In one embodiment, the carbohydrate carbon source includes any one or a combination of at least two of glucose, sucrose, maltose, lactose, fructose, starch, or cellulose.

[0123] In one embodiment, the resin-based carbon source includes any one or a combination of at least two of phenolic resin, polyimide resin, polyester resin, polyaldehyde resin, polyolefin resin, or polyacrylic acid resin.

[0124] In one embodiment, the polymeric carbon source includes any one or a combination of at least two of polyfurfuryl alcohol, polyaniline, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, natural rubber, or polyacrylonitrile.

[0125] In one embodiment, in step (1), the pre-carbonization temperature is 450~650℃, for example, it can be 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, etc.

[0126] In one embodiment, in step (1), the heat preservation time for pre-carbonization is 0.5~24 h, for example, it can be 0.5h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 222 h, 23 h, 24 h, etc.

[0127] In one embodiment, in step (1), the pre-carbonization is carried out in an inert gas atmosphere.

[0128] In one embodiment, in step (1), during the pre-carbonization, the inert gas atmosphere includes any one or a combination of at least two of nitrogen, argon, neon, helium, xenon, or krypton.

[0129] In one embodiment, in step (1), the pre-carbonization is carried out in a carbonization furnace.

[0130] In one embodiment, in step (1), the carbonization furnace includes any one or a combination of at least two of the following: tube furnace, box furnace, pusher kiln or roller kiln.

[0131] In one embodiment, step (1) includes pulverizing the pre-carbonized material to a median particle size of 3-15 μm to obtain the pulverized pre-carbonized material.

[0132] In one embodiment, in step (1), the equipment used for pulverization includes any one or a combination of at least two of the following: a mechanical pulverizer, a roller mill, an air jet mill, or a ball mill.

[0133] In one embodiment, step (1) includes: mixing the pulverized pre-carbonized material with a solid pore-forming agent and performing pore-forming treatment to obtain a solid pore-forming modified material.

[0134] In one embodiment, the mass ratio of the pulverized pre-carbonized material to the solid pore-forming agent is 1:(0.5~3.0), for example, it can be 1:0.5, 1:0.6, 1:0.8, 1:1.0, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0, etc.

[0135] In one embodiment, the solid pore-forming agent comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium oxide, or zinc chloride.

[0136] In one embodiment, in step (1), the temperature of the hole-forming process is 400~700℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, etc.

[0137] In one embodiment, in step (1), the time for the hole-forming process is 0.25~24 h, for example, it can be 0.25 h, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 222 h, 23 h, 24 h, etc.

[0138] In one embodiment, in step (1), the pore-forming process is performed in an inert gas atmosphere and / or an oxygen-deficient atmosphere.

[0139] In one embodiment, in step (1), the inert gas atmosphere in the pore-forming process includes any one or a combination of at least two of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton atmosphere.

[0140] In one embodiment, in step (1), during the pore-forming process, the oxygen-deficient atmosphere is a gaseous atmosphere with an oxygen content ≤ 1 wt%.

[0141] In one embodiment, step (1) further includes a purification process after the pore-forming treatment, the purification process comprising:

[0142] The solid-phase pore-forming modified material was washed with pure water until the pH was 8-10 to obtain purified product one; purified product one, acid and pure water were mixed and stirred to obtain purified product two; purified product two was washed with pure water until the pH was 4-8, and then solid-liquid separation and drying were performed to obtain the purified first precursor.

[0143] In one embodiment, in step (1), the acid in the purification process includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid or sulfuric acid.

[0144] In one embodiment, step (2) includes: mixing the first precursor with an oxidizing acid solution to carry out a modification reaction to obtain a second precursor.

[0145] In this invention, in step (2), the first precursor is mixed with an oxidizing acid solution to carry out a modification reaction, thereby increasing the porosity and the number of cross-linked functional groups to provide sites for the doping reaction and obtaining the second precursor.

[0146] In the modification reaction, the oxidizing solution can penetrate into the interior of the first precursor through the pores, reacting with the non-crosslinking reactive groups (alkyl, alkenyl, alkynyl, aldehyde, etc.) attached to the carbon atoms at the carbon microcrystal edges. This causes these groups to cleave, generating abundant new pores or increasing the pore size of existing pores, and / or transforming into crosslinking functional groups (crosslinking-active functional groups, such as hydroxyl, carboxyl, nitro, and sulfonic acid groups). The pores generated by the modification reaction or the increased pore size of existing pores provide channels for subsequent soft carbon sources and dopants to enter the region near the carbon microcrystal edges. The crosslinking functional groups provide reaction sites for the crosslinking reaction between the microcrystal edges of the first precursor and the soft carbon source and dopants. The new pores generated by this cleavage are mainly ultramicropores, characterized by small pore size (<1 nm), and do not significantly reduce the density performance of the resulting carbon anode. Unmodified carbon materials lack channels for the asphalt dopant to enter the carbon matrix and cross-linking functional groups to react with it. As a result, the doping and cross-linking reactions cannot occur near the edges of carbon crystals, but instead occur on the surface of the carbon material and in the pore walls of some open pores.

[0147] In one embodiment, in step (2), the mass ratio of the first precursor to the oxidizing acid solution is 1:(3~20), for example, it can be 1:3, 1:4, 1:5, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, etc.

[0148] In one embodiment, in step (2), the oxidizing acid solution includes an oxidizing solute and an acid.

[0149] In one embodiment, in step (2), the oxidizing solute includes any one or a combination of at least two of potassium permanganate, potassium dichromate, potassium perchlorate, potassium hypochlorite, sodium permanganate, sodium dichromate, sodium perchlorate, sodium hypochlorite, or hydrogen peroxide.

[0150] In one embodiment, in step (2), the acid in the oxidizing acid solution includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, phosphoric acid, sulfuric acid or nitric acid.

[0151] In one embodiment, in step (2), the concentration of the acid in the oxidizing acid solution is 30~95 wt%, for example, it can be 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, etc. (It should be noted that the concentration of the acid mentioned here refers to the initial concentration of the corresponding acid itself, rather than the final concentration of the oxidizing acid solution).

[0152] In one embodiment, based on the total mass of the oxidizing acid solution as 100%, the oxidizing acid solution comprises, by mass percentage: 0.3-5% oxidizing solute (e.g., 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.), 3-10% acid (e.g., 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.), and the balance being water.

[0153] In one embodiment, in step (2), the temperature of the modification reaction is 50~100℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, etc.

[0154] In one embodiment, in step (2), the modification reaction time is 0.5 to 24 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 222 h, 23 h, 24 h, etc.

[0155] In one embodiment, step (3) includes the following doping treatment: mixing the second precursor and the asphalt dopant solution, first heating to 200-300℃ (e.g., 200℃, 220℃, 240℃, 250℃, 260℃, 280℃, 300℃, etc.) and holding at that temperature for 3-10 h (e.g., 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc.), then heating to 500-800℃ (e.g., 500℃, 520℃, 540℃, 550℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 750℃, 760℃, 780℃, 800℃, etc.) and holding at that temperature for 0.5-5 h (e.g., 0.5 h, 1 h, 1.5 h, 2 h, etc.). (h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc.) to obtain the third precursor.

[0156] In this invention, the uniform distribution coefficient of impurity elements is further improved through the specific heat preservation procedure described above. First, the asphalt dopant is kept at a low temperature (250~300℃) for a long time (3~10 h), allowing it to maintain good fluidity and adsorb into the interconnected pore structure and carbon matrix of the second precursor. Then, it is kept at a high temperature (500~800℃) for 0.5~5 h. The purpose of this is to induce a pre-crosslinking reaction between the carbon microcrystal edges, soft carbon source, and dopant of the first precursor. At this temperature, the pre-crosslinking reaction rate is moderate, ensuring sufficient bonding and solidification between the carbon microcrystal edges, soft carbon source, and dopant, forming a stable doped and bridging structure, suppressing defect formation, promoting crosslinking of carbon microcrystals, and improving porosity. Simultaneously, it avoids excessively rapid heating that could cause the volatile components generated by the cracking of the asphalt dopant to be carried out of the pores, leading to the failure of the crosslinking reaction. Furthermore, it pre-carbonizes excess asphalt, preventing it from acting as a binder and causing particle adhesion during the subsequent sintering stage. This ensures that the cross-linking reaction between the carbon microcrystals, dopant, and pitch in the second precursor is fully carried out, resulting in a more uniform distribution of dopant elements inside the carbon anode particles and in the closed pore region. This enhances the sodium storage activity in the pores, reduces polarization, and thus improves capacity, first-time efficiency, rate charging, and cycle performance.

[0157] In one embodiment, in step (3), the mass ratio of the second precursor to the asphalt dopant is (75~95):(25~5), for example, it can be 75:25, 80:20, 85:15, 90:10, 95:5, etc.

[0158] In one embodiment, step (3) involves mixing the second precursor and the asphalt dopant solution by adding the asphalt dopant solution to the second precursor under low-speed stirring. The low-speed stirring speed is 20-30 r / min, for example, it can be 20 r / min, 21 r / min, 22 r / min, 23 r / min, 24 r / min, 25 r / min, 26 r / min, 27 r / min, 28 r / min, 29 r / min, 30 r / min, etc.

[0159] In one embodiment, in step (3), the heat preservation process of the doping treatment is carried out under stirring; wherein the stirring speed is 100~500 r / min, for example, it can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, etc.

[0160] In one embodiment, in step (3), the heat preservation process is carried out in an inert gas atmosphere.

[0161] In one embodiment, during step (3), the inert gas atmosphere includes any one or a combination of at least two of the following: nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere, or krypton atmosphere.

[0162] In one embodiment, step (3) of preparing the asphalt dopant solution includes: heating and melting asphalt to obtain liquid asphalt; adding a dopant to the liquid asphalt and stirring until dissolved to obtain the asphalt dopant solution.

[0163] In one embodiment, the asphalt doping solution includes a dopant and liquid asphalt.

[0164] In one embodiment, the mass ratio of the dopant to the liquid asphalt is (0.1~1):1, for example, it can be 0.1:1, 0.2:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, 1:1, etc.

[0165] In one embodiment, the dopant includes any one or a combination of at least two of a nitrogen source, a phosphorus source, or a sulfur source.

[0166] In one embodiment, the nitrogen source includes any one or a combination of at least two of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acids, or ammonium bicarbonate.

[0167] In one embodiment, the phosphorus source includes any one or a combination of at least two of phosphorus trichloride, phosphorus pentoxide, triammonium phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, or phosphate esters.

[0168] In one embodiment, the sulfur source includes any one or a combination of at least two of sulfur powder, thiourea, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, or cysteine.

[0169] In one embodiment, in step (4), the sintering temperature is 1100~1400℃, for example, it can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, etc.

[0170] In one embodiment, the sintering time in step (4) is 0.25~10 h, for example, it can be 0.25 h, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc.

[0171] In one embodiment, in step (4), the sintering is carried out in an inert gas atmosphere.

[0172] In one embodiment, during step (4) of the sintering process, the inert gas atmosphere includes any one or a combination of at least two of nitrogen, argon, neon, helium, xenon, or krypton.

[0173] In one embodiment, in step (4), the sintering is carried out in a sintering furnace.

[0174] In one embodiment, in step (4), the sintering furnace includes any one or a combination of at least two of the following: tube furnace, box furnace, roller kiln or rotary furnace.

[0175] The present invention also provides a negative electrode sheet, the negative electrode sheet comprising the aforementioned carbon negative electrode material.

[0176] The present invention also provides a sodium-ion battery, wherein the sodium-ion battery includes the aforementioned negative electrode sheet.

[0177] The present invention also provides an electrical device, the electrical device including the aforementioned sodium-ion battery.

[0178] The present application will be further described below through specific embodiments. Unless otherwise specified, the experimental materials used in the embodiments can be purchased from conventional biochemical reagent companies.

[0179] Example 1

[0180] This embodiment provides a carbon anode material, which is prepared by the following steps:

[0181] (1) The washed and dried coconut shells were placed in a box furnace and heated to 500°C under a nitrogen atmosphere and kept at that temperature for 24 h. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and crushed to a median particle size of 5 μm to obtain the crushed material. The crushed material and potassium hydroxide were mixed in a VC mixer at a mass ratio of 1:0.5 and then placed in a box furnace and heated to 700°C under a nitrogen atmosphere and kept at that temperature for 1 h. After cooling, the mixture was washed with pure water until the pH reached 8~10. Then, 0.5 times the mass of the crushed material of hydrochloric acid (31wt%) and 2 times the mass of the crushed material of pure water at 80°C were added, stirred for 1 h, washed with pure water until the pH reached 4~8, the solid and liquid were separated, and the mixture was dried to obtain the first precursor.

[0182] (2) According to the mass ratio, 0.5 parts of potassium permanganate and 9.5 parts of hydrochloric acid (31 wt%) were added to 90 parts of pure water, stirred and dissolved to prepare a 0.5 wt% potassium permanganate hydrochloric acid solution; 1 times the mass of the first precursor obtained in step (1) was added to 3 times the mass of the 0.5 wt% potassium permanganate hydrochloric acid solution, heated to 90°C in a water bath under stirring, kept warm for 6 h, and cooled to obtain the second precursor;

[0183] (3) Heat 2 parts by weight of high-temperature asphalt to about 250°C until it melts, add 1 part by weight of phosphorus pentoxide while stirring, and keep it at the temperature for 0.5 h while stirring to obtain liquid asphalt dopant; according to the mass ratio of the second precursor to the asphalt dopant is 90:10, put the second precursor into a VC mixer, and slowly add the asphalt dopant at a speed of 20 r / min. After the addition is complete, increase the speed to 200 r / min, raise the temperature to 250°C under a nitrogen atmosphere, keep it at the temperature for 5 h, and then further raise the temperature to 800°C, keep it at the temperature for 3 h, and cool to obtain the third precursor;

[0184] (4) The third precursor was placed in a tube furnace and sintered at 1300°C for 3 h in a nitrogen atmosphere. After cooling, it was sieved through a 325-mesh sieve to obtain the carbon anode material.

[0185] Example 2

[0186] This embodiment provides a carbon anode material, which is prepared by the following steps:

[0187] (1) The thermosetting phenolic resin was placed in a box furnace and heated to 600°C under a nitrogen atmosphere and kept at that temperature for 2 h. The resulting material was crushed with a crusher with a screen mesh size of 3 mm and crushed to a median particle size of 3 μm to obtain a pulverized material. The pulverized material and potassium hydroxide were mixed in a VC mixer at a mass ratio of 1:3 and then placed in a box furnace and heated to 400°C under a nitrogen atmosphere and kept at that temperature for 24 h. After cooling, the mixture was washed with pure water until the pH reached 8~10. Then, hydrochloric acid (31 wt%) with 1 times the mass of the pulverized material and pure water at 80°C with 3 times the mass of the pulverized material were added, stirred for 1 h, washed with pure water until the pH reached 4~8, the solid and liquid were separated, and the mixture was dried to obtain the first precursor.

[0188] (2) According to the mass ratio, add 1 part potassium dichromate and 9 parts nitric acid (50 wt%) to 90 parts pure water, stir to dissolve, and prepare a 1 wt% potassium dichromate nitric acid solution; add 1 times the mass of the first precursor obtained in step (1) to 20 times the mass of the 1 wt% potassium dichromate nitric acid solution, heat to 50°C in a water bath with stirring, keep warm for 24 h, cool, and obtain the second precursor;

[0189] (3) Heat the medium-temperature asphalt to about 200°C until it melts, add melamine of the same mass as the medium-temperature asphalt while stirring, and keep it at the temperature for 0.5 h while stirring to obtain liquid asphalt dopant. The second precursor and the asphalt dopant are added to a VC mixer at a mass ratio of 75:25, and the asphalt dopant is slowly added at a speed of 25 r / min. After the addition is completed, the speed is increased to 500 r / min, the temperature is raised to 200°C under a nitrogen atmosphere, and kept at the temperature for 5 h. Then the temperature is further raised to 750°C and kept at the temperature for 5 h. After cooling, the third precursor is obtained.

[0190] (4) The third precursor was placed in a tube furnace and sintered at 1400°C for 0.5 h in a nitrogen atmosphere. After cooling, it was sieved through a 325-mesh sieve to obtain the carbon anode material.

[0191] Example 3

[0192] This embodiment provides a carbon anode material, which is prepared by the following steps:

[0193] (1) Thermosetting phenolic resin and potato starch were mixed in a VC mixer at a mass ratio of 1:1, placed in a box furnace, heated to 650°C under an argon atmosphere, and kept at that temperature for 3 h. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and pulverized to a median particle size of 15 μm to obtain pulverized material. The pulverized material and potassium oxide were mixed in a VC mixer at a mass ratio of 1:1, placed in a box furnace, heated to 650°C under a helium atmosphere, and kept at that temperature for 2 h. After cooling, the mixture was washed with pure water until pH=8~10. Then, 0.7 times the mass of the pulverized material of hydrochloric acid (31 wt%) and 5 times the mass of the pulverized material of pure water at 80°C were added, stirred for 1 h, washed with pure water until pH=4~8, solid-liquid separation was performed, and the mixture was dried to obtain the first precursor.

[0194] (2) According to the mass ratio, 0.2 parts of sodium perchlorate and 9.8 parts of dilute sulfuric acid (30 wt%) were added to 90 parts of pure water, stirred and dissolved to prepare a 0.2 wt% sodium perchlorate sulfuric acid solution; 1 times the mass of the first precursor obtained in step (1) was added to 10 times the mass of the 0.2 wt% sodium perchlorate sulfuric acid solution, heated to 80°C in a water bath under stirring, kept warm for 10 h, and cooled to obtain the second precursor;

[0195] (3) Heat the high-temperature asphalt to about 300℃ until it melts, and add ammonium thiosulfate of the same mass as the medium-temperature asphalt while stirring. Keep it at this temperature for 0.5 h while stirring to obtain a liquid asphalt dopant solution. The second precursor and the asphalt dopant solution are added to a VC mixer at a mass ratio of 85:15. The asphalt dopant solution is added slowly at a speed of 30 r / min. After the addition is complete, the speed is increased to 100 r / min, and the temperature is raised to 300℃ under a nitrogen atmosphere and kept at this temperature for 4 h. Then the temperature is further raised to 500℃ and kept at this temperature for 0.5 h. After cooling, the third precursor is obtained.

[0196] (4) The third precursor was placed in a tube furnace and sintered at 1200°C for 5 h in a nitrogen atmosphere. After cooling, it was sieved through a 325-mesh sieve to obtain the carbon anode material.

[0197] Example 4

[0198] This embodiment provides a carbon anode material, which is prepared by the following steps:

[0199] (1) Place lignite in a box furnace and heat it to 450°C under a krypton atmosphere. Hold it at 6 K. Crush the resulting material with a screen mesh size of 4 mm and grind it to a median particle size of 8 μm to obtain pulverized material. Mix the pulverized material and zinc chloride in a VC mixer at a mass ratio of 1:1. Place the mixture in a box furnace and heat it to 650°C under a nitrogen atmosphere. Hold it at 2 h. Cool it and wash it with pure water until pH=8~10. Add 0.5 times the mass of the pulverized material of hydrochloric acid (31 wt%) and 10 times the mass of the pulverized material of pure water at 80°C. Stir for 1 h and wash with pure water until pH=4~8. Separate the solid and liquid, dry it, and obtain the first precursor.

[0200] (2) According to the mass ratio, 5 parts of hydrogen peroxide solution (30 wt%) and 5 parts of hydrochloric acid (31 wt%) were added to 90 parts of pure water, stirred and dissolved to prepare a 5 wt% hydrogen peroxide hydrochloric acid solution; 1 mass of the first precursor obtained in step (1) was added to 10 times the mass of the 5 wt% hydrogen peroxide hydrochloric acid solution, heated to 75°C in a water bath under stirring, kept warm for 8 h, and cooled to obtain the second precursor.

[0201] (3) Heat the high-temperature asphalt to about 255°C until it melts. Add sulfur powder of the same mass as the medium-temperature asphalt while stirring. Keep the mixture at this temperature for 0.5 h while stirring to obtain a liquid asphalt dopant solution. Add the second precursor to the VC mixer at a mass ratio of 95:5. Slowly add the asphalt dopant solution at a speed of 28 r / min. After the addition is complete, increase the speed to 500 r / min and heat the mixture to 255°C under a nitrogen atmosphere. Keep the mixture at this temperature for 5 h. Then, further heat the mixture to 650°C and keep it at this temperature for 4 h. Cool the mixture to obtain the third precursor.

[0202] (4) The third precursor was placed in a tube furnace and sintered at 1100°C for 10 h in a nitrogen atmosphere. After cooling, it was sieved through a 325-mesh sieve to obtain the carbon anode material.

[0203] Example 5

[0204] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (3), the phosphorus source is diammonium hydrogen phosphate. The rest is the same as in Embodiment 1.

[0205] Example 6

[0206] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (3), the phosphorus source is triethyl phosphate. The rest is the same as in Embodiment 1.

[0207] Example 7

[0208] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (3), the high-temperature asphalt is 2 parts and phosphorus pentoxide is 0.2 parts. The rest is the same as in Embodiment 1.

[0209] Example 8

[0210] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (3), the high-temperature asphalt is 2 parts and phosphorus pentoxide is 2 parts. The rest is the same as in Embodiment 1.

[0211] Example 9

[0212] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (3), after the addition is complete, the temperature is raised to 200°C under a nitrogen atmosphere and held for 3 hours, then further raised to 500°C and held for 0.5 hours, and then cooled to obtain the third precursor. The rest is the same as in Embodiment 1.

[0213] Example 10

[0214] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (3), after the addition is complete, the temperature is raised to 300°C under a nitrogen atmosphere and held for 10 h, then further raised to 800°C and held for 5 h, and then cooled to obtain the third precursor. The rest is the same as in Embodiment 1.

[0215] Example 11

[0216] This embodiment provides a carbon anode material, wherein the impurity element content distribution coefficient of the carbon anode material is 25%, and the phosphorus content is 3.14 wt%; the carbon anode material is prepared by the following steps:

[0217] (1) Same as step (1) in Example 1.

[0218] (2) Same as step (1) in Example 1.

[0219] (3) Heat 1 part of high-temperature asphalt to about 250°C until it melts, add 1 part of phosphorus pentoxide under stirring, and keep it at the temperature for 3 hours under stirring to obtain liquid asphalt dopant; according to the mass ratio of the second precursor to the asphalt dopant of 85:15, put the second precursor into the VC mixer and slowly add the asphalt dopant at a speed of 30 r / min; after the addition is completed, increase the speed to 450 r / min, heat to 250°C under a nitrogen atmosphere, keep it at the temperature for 3 hours, then further heat to 750°C, keep it at the temperature for 3 hours, and cool to obtain the third precursor.

[0220] (4) Same as Example 1.

[0221] Example 12

[0222] This embodiment provides a carbon anode material, wherein the impurity element content distribution coefficient of the carbon anode material is 175%, and the phosphorus content is 0.41 wt%; the carbon anode material is prepared by the following steps:

[0223] (1) Same as step (1) in Example 1;

[0224] (2) Same as step (2) in Example 1;

[0225] (3) Heat 1 part of high-temperature asphalt to about 250°C until it melts, add 0.2 parts of phosphorus pentoxide under stirring, and keep it at the temperature for 1 h under stirring to obtain liquid asphalt dopant; according to the mass ratio of the second precursor to the asphalt dopant of 95:5, put the second precursor into the VC mixer, and slowly add the asphalt dopant at a speed of 20 r / min; after the addition is completed, increase the speed to 300 r / min, raise the temperature to 265°C under nitrogen atmosphere, keep it at the temperature for 3 h, and then further raise the temperature to 780°C, keep it at the temperature for 2 h, and cool to obtain the third precursor;

[0226] (4) is the same as step (4) in Example 1.

[0227] Example 13

[0228] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (4), the third precursor is placed in a tube furnace and sintered at 1450°C for 3 h in a nitrogen atmosphere, cooled, and sieved through a 325-mesh sieve to obtain the carbon anode material.

[0229] Example 14

[0230] This embodiment provides a carbon anode material, which differs from Embodiment 1 in that: in step (4), the third precursor is placed in a tube furnace and sintered at 1100°C for 3 h in a nitrogen atmosphere, cooled, and sieved through a 325-mesh sieve to obtain the carbon anode material.

[0231] Comparative Example 1

[0232] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0233] (1) The washed and dried coconut shells were mechanically crushed (100 mesh), and VC was mixed with the coconut shell crushed material and phosphorus pentoxide in a mass ratio of 100:1. The mixture was pressed and placed in a box furnace. The temperature was raised to 500℃ under a nitrogen atmosphere and kept for 24 hours. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and crushed to a median particle size of 5 μm to obtain the crushed material. The crushed material and potassium hydroxide were mixed with VC in a mass ratio of 1:0.5 and placed in a box furnace. The temperature was raised to 700℃ under a nitrogen atmosphere and kept for 1 hour. The mixture was cooled and washed with pure water until the pH reached 8~10. Then, 0.5 times the mass of the crushed material of hydrochloric acid (31 wt%) and 2 times the mass of the crushed material of pure water at 80℃ were added. The mixture was stirred for 1 hour and washed with pure water until the pH reached 4~8. The solid and liquid were separated to obtain the first precursor.

[0234] (2) Same as step (2) in Example 1;

[0235] (3) Heat 7.4 parts by mass of high-temperature asphalt to about 250°C until it melts, and keep it at that temperature for 0.5 h with stirring to obtain liquid asphalt liquid; put 100 parts by mass of the second precursor into a VC mixer, slowly add the asphalt liquid at a speed of 25 r / min, after the addition is complete, increase the speed to 300 r / min, heat to 250°C in a nitrogen atmosphere, keep it at that temperature for 5 h, then further heat to 800°C, keep it at that temperature for 3 h, cool to obtain the third precursor;

[0236] (4) is the same as step (4) in Example 1.

[0237] Comparative Example 2

[0238] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0239] (1) The washed and dried coconut shells were placed in a box furnace and heated to 500°C under a nitrogen atmosphere. The temperature was maintained for 24 h. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and pulverized to a median particle size of 5 μm to obtain pulverized material. The pulverized material and phosphorus pentoxide were mixed with VC at a mass ratio of 100:2.5 and placed in a box furnace. The temperature was raised to 600°C under a nitrogen atmosphere and maintained for 3 h. After cooling, the dopant was obtained. Then, the dopant and potassium hydroxide were mixed with VC at a mass ratio of 1:0.5 and placed in a box furnace. The temperature was raised to 700°C under a nitrogen atmosphere and maintained for 1 h. After cooling, the mixture was washed with pure water until the pH reached 8~10. Hydrochloric acid of 0.5 times the mass of the pulverized material and pure water at 80°C of 2 times the mass of the pulverized material were added and stirred for 1 h. The mixture was washed with pure water until the pH reached 4~8. Solid-liquid separation was performed to obtain the first precursor.

[0240] (2) Same as step (2) in Example 1;

[0241] (3) Heat 7.4 parts by mass of high-temperature asphalt to about 250°C until it melts, and keep it at that temperature for 0.5 h with stirring to obtain liquid asphalt liquid; put 100 parts by mass of the second precursor into a VC mixer, slowly add the asphalt liquid at a speed of 25 r / min, after the addition is complete, increase the speed to 300 r / min, heat to 250°C in a nitrogen atmosphere, keep it at that temperature for 5 h, then further heat to 800°C, keep it at that temperature for 3 h, cool to obtain the third precursor;

[0242] (4) is the same as step (4) in Example 1.

[0243] Comparative Example 3

[0244] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0245] (1) The washed and dried coconut shells were placed in a box furnace and heated to 500°C under a nitrogen atmosphere. The temperature was maintained for 24 h. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and crushed to a median particle size of 5 μm to obtain the crushed material. The crushed material, hydrochloric acid (31 wt%), hydrofluoric acid (55 wt%) and 80°C pure water were mixed in a mass ratio of 1:0.5:0.3:3 and stirred for 6 h. The mixture was washed with pure water until the pH reached 4~8. The solid and liquid were separated and dried to obtain the first precursor.

[0246] (2) Same as step (2) in Example 1;

[0247] (3) Same as step (3) in Example 1;

[0248] (4) is the same as step (4) in Example 1.

[0249] Comparative Example 4

[0250] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0251] (1) The washed and dried coconut shells were placed in a box furnace and heated to 500°C under a nitrogen atmosphere. The temperature was maintained for 24 h. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and crushed to a median particle size of 5 μm to obtain the crushed material. The crushed material, phosphorus pentoxide and potassium hydroxide were mixed in a mass ratio of 100:2.5:50 and placed in a box furnace. The temperature was raised to 700°C under a nitrogen atmosphere and maintained for 1 h. The mixture was cooled and washed with pure water until the pH reached 8~10. Then, 0.5 times the mass of the crushed material of hydrochloric acid (31 wt%) and 2 times the mass of the crushed material of pure water at 80°C were added. The mixture was stirred for 1 h and washed with pure water until the pH reached 4~8. The solid and liquid were separated and dried to obtain the first precursor.

[0252] (2) Same as step (2) in Example 1;

[0253] (3) Heat 7.4 parts by mass of high-temperature asphalt to about 250°C until it melts, and keep it at that temperature for 0.5 h with stirring to obtain liquid asphalt liquid; put 100 parts by mass of the second precursor into a VC mixer, slowly add the asphalt liquid at a speed of 25 r / min, after the addition is complete, increase the speed to 300 r / min, heat to 250°C in a nitrogen atmosphere, keep it at that temperature for 5 h, then further heat to 800°C, keep it at that temperature for 3 h, cool to obtain the third precursor;

[0254] (4) is the same as step (4) in Example 1.

[0255] Comparative Example 5

[0256] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0257] (1) The washed and dried coconut shells were placed in a box furnace and heated to 500°C under a nitrogen atmosphere and kept at that temperature for 24 h. The resulting material was crushed with a crusher with a screen mesh size of 5 mm and crushed to a median particle size of 5 μm to obtain the crushed material. The crushed material and potassium hydroxide were mixed in a mass ratio of 1:0.5 for VC and placed in a box furnace. The temperature was raised to 700°C under a nitrogen atmosphere and kept at that temperature for 1 h. The mixture was then cooled and washed with pure water until the pH reached 8~10. Hydrochloric acid (31 wt%) of 0.5 times the mass of the crushed material and pure water at 80°C of 2 times the mass of the crushed material were added and stirred for 1 h. The mixture was then washed with pure water until the pH reached 4~8. The solid and liquid were separated and dried. The resulting material and phosphorus pentoxide were mixed in a mass ratio of 100:2.5 for VC and placed in a box furnace. The temperature was raised to 800°C under a nitrogen atmosphere and kept at that temperature for 3 h. The mixture was then cooled to obtain the first precursor.

[0258] (2) Same as step (2) in Example 1;

[0259] (3) Heat 7.4 parts by mass of high-temperature asphalt to about 250°C until it melts, and keep it at that temperature for 0.5 h with stirring to obtain liquid asphalt liquid; put 100 parts by mass of the second precursor into a VC mixer, slowly add the asphalt liquid at a speed of 25 r / min, after the addition is complete, increase the speed to 300 r / min, heat to 250°C in a nitrogen atmosphere, keep it at that temperature for 5 h, then further heat to 800°C, keep it at that temperature for 3 h, cool to obtain the third precursor;

[0260] (4) is the same as step (4) in Example 1.

[0261] Comparative Example 6

[0262] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0263] (1) Same as step (1) in Example 1;

[0264] (2) According to the mass ratio, 9.5 parts of industrial hydrochloric acid (mass concentration of 31 wt%) were added to 90 parts of pure water, stirred and dissolved to prepare a dilute hydrochloric acid solution; 1 mass of the first precursor obtained in step (1) was added to 3 times the mass of the dilute hydrochloric acid solution, heated to 90°C in a water bath under stirring, kept warm for 6 h, and cooled to obtain the second precursor;

[0265] (3) Same as step (3) in Example 1;

[0266] (4) is the same as step (4) in Example 1.

[0267] Comparative Example 7

[0268] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0269] (1) Same as step (1) in Example 1;

[0270] (2) Same as step (2) in Example 1;

[0271] (3) The second precursor and phosphorus pentoxide were fed into a VC mixer at a mass ratio of 90:3.33. The speed was increased to 300 r / min, the temperature was raised to 250℃ under a nitrogen atmosphere, and the temperature was held for 5 h. Then the temperature was further raised to 800℃ and held for 3 h. After cooling, the third precursor was obtained.

[0272] (4) is the same as step (4) in Example 1.

[0273] Comparative Example 8

[0274] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0275] (1) Same as step (1) in Example 1;

[0276] (2) Same as step (2) in Example 1;

[0277] (3) The second precursor, phosphorus pentoxide, and high-temperature asphalt (median particle size 2.5 μm) were added to the VC mixer in a mass ratio of 90:3.33:6.67, the speed was increased to 300 r / min, and the mixture was mixed for 0.5 h. Then the mixture was placed in a box furnace, heated to 800℃, kept at the temperature for 3 h, and cooled to obtain the third precursor.

[0278] (4) is the same as step (4) in Example 1.

[0279] Comparative Example 9

[0280] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0281] (1) Same as step (1) in Example 1;

[0282] (2) Same as step (2) in Example 1;

[0283] (3) Heat 7.4 parts by mass of high-temperature asphalt to about 250°C until it melts, and keep it at that temperature for 0.5 h with stirring to obtain liquid asphalt liquid; put 100 parts by mass of the second precursor into a VC mixer, slowly add the asphalt liquid at a speed of 25 r / min, after the addition is complete, increase the speed to 300 r / min, heat to 250°C in a nitrogen atmosphere, keep it at that temperature for 5 h, then further heat to 800°C, keep it at that temperature for 3 h, cool to obtain the third precursor;

[0284] (4) is the same as step (4) in Example 1.

[0285] Comparative Example 10

[0286] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0287] (1) Same as step (1) in Example 1;

[0288] (2) Same as step (2) in Example 1;

[0289] (3) Heat 2 parts by weight of high-temperature asphalt to about 250°C until it melts, add 1 part by weight of phosphorus pentoxide while stirring, and keep it at this temperature for 0.5 h while stirring to obtain a liquid asphalt dopant solution; according to the mass ratio of the second precursor to the asphalt dopant solution of 90:10, put the second precursor into a VC mixer, and slowly add the asphalt dopant solution at a speed of 50 r / min. After the addition is complete, increase the speed to 300 r / min, heat to 250°C under a nitrogen atmosphere, keep it at this temperature for 8 h, and cool to obtain the third precursor;

[0290] (4) is the same as step (4) in Example 1.

[0291] Comparative Example 11

[0292] This comparative example provides a carbon anode material, which is prepared by the following steps:

[0293] (1) Same as step (1) in Example 1;

[0294] (2) Same as step (2) in Example 1;

[0295] (3) Heat 2 parts by weight of high-temperature asphalt to about 250°C until it melts, add 1 part by weight of phosphorus pentoxide while stirring, and keep it at this temperature for 0.5 h while stirring to obtain a liquid asphalt dopant solution; according to the mass ratio of the second precursor to the asphalt dopant solution of 90:10, put the second precursor into a VC mixer, and slowly add the asphalt dopant solution at a speed of 25 r / min. After the addition is complete, increase the speed to 300 r / min, heat to 800°C under a nitrogen atmosphere, keep it at this temperature for 8 h, and cool to obtain the third precursor;

[0296] (4) is the same as step (4) in Example 1.

[0297] Test Example 1

[0298] Test samples: carbon anode materials provided in Examples 1-14 and carbon anode materials provided in Comparative Examples 1-11.

[0299] Test method:

[0300] (1) SEM images and tests on impurity element content and distribution coefficient:

[0301] The samples were scanned using a Zeiss GEMINI 460 scanning electron microscope (SEM) to obtain SEM images. The content of impurity elements (N, P, S) was tested using SEM combined with energy dispersive X-ray spectroscopy (EDS) at 1000x magnification. The carbon anode material was placed on a support, and cross-sectional samples were obtained by cutting with a high-energy argon ion beam. SEM combined with EDS was used for analysis. The impurity element content distribution coefficient (e.g., ...) of a randomly selected cross-sectional region of a particle was analyzed. Figure 5A and Figure 5B The calculation formula (as shown) is as follows:

[0302] Distribution coefficient of impurity element content (%)

[0303] Where AB is the longest line segment in the cross-section of the carbon anode material particle (A and B are the endpoints of the line segments around the cross-section), S is the integral area of ​​the impurity element mass concentration along the displacement AB measured by EDS, in wt% × μm; a and b are the impurity element mass concentrations at points A and B, respectively, in wt%; R is the distance between points AB, in μm; the significance of the impurity element content distribution coefficient: when the impurity element mass concentration (y) curve along the displacement x completely coincides with the line segment FE, the impurity element mass concentration along the AB direction is linearly distributed, and the impurity element concentration can be considered close to the ideal distribution. At this time, S is the area of ​​the right trapezoid CDEF, and the impurity element content distribution coefficient is 100%; when the impurity element mass concentration curve along the displacement x deviates from the line segment FE, the impurity element content distribution coefficient deviates from 100%, and the magnitude of the deviation is positively correlated with the degree of uneven distribution of impurity elements. The impurity element content distribution coefficient is calculated by randomly selecting three cross-sectional areas of the carbon anode material particles, and the average value is the impurity element content distribution coefficient of the carbon anode material. The closer the impurity element content distribution coefficient of a carbon anode material is to 100%, the higher the uniformity of its impurity element distribution; the further the impurity element content distribution coefficient deviates from 100%, the more uneven the impurity element content distribution of the carbon anode material.

[0304] (2) Testing of median particle size:

[0305] The test was conducted using a MasterSizer 3000. The particle refractive index was 2.42, the absorptivity was 1.0, and the dispersant was water with a refractive index of 1.33. The method was as follows: approximately 0.1 g of sample was weighed into a 100 mL beaker, water was added to a final volume of 50 mL, and the mixture was sonicated for 1 min. The sample was then added until the opacity was 8-12%, and the mixture was sonicated internally.

[0306] (3) True density and pore volume of closed pores:

[0307] The true density was measured using a Bestech 3H-2000TD true density meter based on the gas (helium) expansion displacement method: approximately 3 / 4 volume of the sample was weighed into the sample cell, and the sample was displaced with helium 30 times, followed by helium measurement of the true density value. The pore volume of the closed pore (cm³) was also measured. 3 / g) is obtained through theoretical calculations, and the formula is:

[0308] The volume of the closed hole = (1 / ρ -1 / ρ 参 )

[0309] in, ρ The true density of the sample (g / cm³) 3 ), ρ 参 True density (g / cm³) of the reference sample 3 ).

[0310] Graphite is generally considered a non-porous carbon material; therefore, artificial graphite (D50 = 8 μm) is used as a reference. ρ 参 =2.25 g / cm 3 . In the formula, ρ 参 The physical meaning of "pore volume of closed pores" is the density of the carbon matrix in the non-porous regions of the sample. Therefore, the physical meaning of "pore volume of closed pores" is the pore volume (cm³) of the closed pores contained in 1 g of sample. 3 / g).

[0311] (4) Compacted density of 3T powder (g / cm³) 3 ):

[0312] The Shenzhen Sansi Zongheng Battery Powder Compacted Density Tester UTM7305 was used for testing. A sample of specified mass was placed in a mold, a pressure of 3T was applied, and the pressure was held for 30 seconds before being released to 20N to measure its thickness. The thickness was then determined according to the formula... ρ =10×(m / S×H), the compaction density (unit: g / cm³) is automatically output by the instrument's software. 3 ).

[0313] (5) Specific surface area test:

[0314] The specific surface area was obtained by nitrogen adsorption testing at 77 K using a McMeter specific surface area meter (model ASAP2460). The specific surface area was calculated using the BET formula (unit: m³). 2 / g).

[0315] (6) Carbon interlayer content test:

[0316] XRD data were obtained using a Panalytical X'Pert PRO MPD instrument with Kα rays (wavelength λ = 0.1541 nm) from a Cu target as the light source, within the 2 Theta range of 10° to 90°. The carbon interlayer spacing was calculated (in nm) by substituting the (002) diffraction angle of the XRD into the Scherrer formula.

[0317] (7) Powder conductivity test:

[0318] The conductivity data (unit: S / cm) was obtained by adding the sample to a Mitsubishi Chemical MCP-PD51 tester and testing at 20 kN.

[0319] The specific test results are shown in Table 1 below:

[0320] Table 1

[0321]

[0322] As shown in Table 1, the content of impurity elements in the carbon anode material of the present invention is 0.4~5 wt%; the impurity element content distribution coefficient of the carbon anode material is 25.0~175.0%. This indicates that the impurity elements can penetrate into the interior of the carbon particles of the carbon anode material, and the impurity elements are uniformly distributed inside the carbon particles and fully bonded with the carbon elements. Furthermore, the conductivity of the carbon anode material is 26.8~50.3 S / cm, preferably 42.0~50.3 S / cm; this indicates that a large number of impurity elements are distributed in the closed pore region, thereby preferably increasing the electron cloud density of the closed pores and improving the powder conductivity of the carbon anode material. In addition, the carbon interlayer spacing of the carbon anode material is 0.37~0.39 nm, and the closed pore volume is 0.04~0.3 cm³. 3 The compacted density of 3T powder is 1.0~1.1 g / cm³. 3 The true density is 1.56~2.06 g / cm³. 3 The specific surface area of ​​the carbon anode material is 1.5~8.0 m². 2 / g; This demonstrates that the carbon anode material of the present invention has advantages such as large interlayer spacing, numerous closed pores, and dense structure.

[0323] The comparison data of Examples 1, 13, and 14 in Table 1 show that the 3T compaction density of the carbon anode materials in Examples 13 and 14 is worse than that of the carbon anode material obtained in Example 1. The sintering temperature of step (4) in Example 13 is higher, while the sintering temperature of step (4) in Example 14 is lower. Sintering temperature has a significant impact on the formation of closed pores and the changes in carbon interlayers. When the sintering temperature is too high, the chemical bonds between heteroatoms and carbon atoms break, the volume of closed pores increases significantly, the effective volume ratio of closed pores for sodium storage in the carbon anode decreases, the carbon interlayer spacing decreases, resulting in a decrease in sodium storage capacity instead of an increase, and an increase in electrochemical polarization. When the sintering temperature is too low, the carbon microcrystals cannot be fully cross-linked, the hydrocarbon content is high, resulting in a smaller closed pore volume, lower conductivity of the carbon matrix, and increased electrochemical polarization. Therefore, the compaction density performance decreases.

[0324] The comparison data of Example 1 and Comparative Example 1 in Table 1, and Figure 6 and Figure 7 The comparison shows that, in Comparative Example 1, carbon anode materials were prepared by directly combining hard carbon source and dopant and then pre-carbonizing them. During the pre-carbonization process, the dopant could not be incorporated into the interior of the hard carbon particles (e.g., Figure 9 As shown in the figure, the dopant reacts with the tar components from the cracking of the hard carbon source, inhibiting the removal of tar components. The tar components occupy sodium storage sites, inhibiting the porosity of hard carbon and reducing its carbon interlayer, etc. The heteroatom distribution coefficient and the closed pore volume are both small.

[0325] As can be seen from the comparison data of Example 1 and Comparative Examples 2, 4, and 5 in Table 1, and... Figure 8 The comparison shows that Comparative Example 2 involves a combined heating doping method using hard carbon precarburized material and dopant; Comparative Example 4 involves simultaneous heating and doping using hard carbon precarburized material, pore-forming agent, and dopant; and Comparative Example 5 first modifies the hard carbon precarburized material to create pores before heating and doping with the dopant. In Comparative Examples 2, 4, and 5, the doping modification involved separate reactions of hard carbon precarburized material and dopant, and simultaneous reactions of hard carbon precarburized material, pore-forming agent, and dopant, respectively. The hard carbon precarburized material was first activated with an alkaline solution before being heated and reacted with the dopant. These methods result in dopant elements primarily concentrated on the surface of the carbon anode material particles, leading to low heteroatom distribution coefficients and powder conductivity. The dopant elements cannot fully bond with the hard carbon components, and they cannot improve the degree of microcrystalline cross-linking, catalyze the conversion of "open pores" to "closed pores," or enhance the conductivity of the pore region. In the carbon anode preparation method of Example 1, hard carbon is first pre-carbonized, pore-forming, and modified. Then, asphalt doping solution is embedded into the second precursor particles under VC heating. Hard carbon microcrystals, soft carbon source, and dopant undergo cross-linking reaction under high temperature to achieve doping. This can improve the uniformity of dopant element distribution inside the carbon anode particles, increase the degree of cross-linking of carbon microcrystals, and increase the number of closed pores and sodium storage activity in the closed pore area of ​​the carbon anode material.

[0326] The comparison data between Example 1 and Comparative Examples 3 and 6 in Table 1 show that the carbon anode material of Comparative Example 3 was not subjected to pore-forming after pre-carbonization in step (1), while Comparative Example 6 was not subjected to modification reaction in step (2). The purpose of pore-forming is to construct a connected pore structure inside the hard carbon particles, providing channels for dopants and soft carbon sources to enter the hard carbon particles. The purpose of modification reaction is to improve the porosity of the carbon matrix and increase the amount of cross-linking functional groups based on pore-forming, providing reaction sites for soft and hard carbon composite and heteroatom doping. The impurity content, impurity distribution coefficient and conductivity of the carbon anode material of Comparative Example 3 are relatively low. Although the impurity content, impurity distribution coefficient and conductivity of the carbon anode material of Comparative Example 6 are better than those of Comparative Example 3, the activity of soft and hard carbon composite and heteroatom doping reaction is not strong due to the lack of modification. The closed pore volume and conductivity are not much different from those of Comparative Example 3, and both are worse than Example 1. This demonstrates that combining pore formation and modification, with their synergistic effect, offers significant technical advantages in improving the content of impurities and their distribution uniformity, as well as the volume of closed pores and electrical conductivity.

[0327] As can be seen from the comparison data of Example 1 and Comparative Examples 7, 8 and 9 in Table 1, and... Figure 8The comparison shows that in Comparative Example 7, step (3) did not first heat the dopant and asphalt to prepare the asphalt doping solution, but directly used the dopant and the second precursor for the doping reaction; in Comparative Example 8, step (3) directly mixed the second precursor and the asphalt doping solution and then heated the solution for doping without heating with VC; in Comparative Example 9, based on Example 1, the asphalt melt was used instead of the asphalt doping solution to carry out the doping reaction with the second precursor. In Comparative Examples 7 and 8, there was no cross-linking reaction between the carbon microcrystals of the second precursor, the dopant, and the asphalt, so the soft and hard carbon composite and doping modification could not occur effectively inside the carbon matrix, and the doping elements could not be evenly distributed in the area near the closed pores, resulting in low sodium storage activity and high polarization of the closed pores. The closed pore volume, carbon layer spacing, and powder conductivity of Comparative Example 9 were not as good as those of Example 1. This is because in this invention, the dopant in the asphalt doping solution played a role in catalyzing the cross-linking of hard carbon microcrystals and soft carbon sources, promoting the transformation of "open pores" into "closed pores", and improving the conductivity of the closed pore area. This demonstrates that the present invention has significant technical advantages in combining asphalt doping liquid (soft carbon source, dopant) and VC heating in step (3).

[0328] The comparative data from Example 1 and Comparative Examples 10-11 in Table 1 show that performing only low-temperature doping or only high-temperature doping will result in uneven doping. A combination of low-temperature and high-temperature doping is necessary to ensure uniform doping. This indicates that the present invention further improves the uniformity of heterogeneous element distribution through a specific heat preservation procedure during the doping process. Specifically, by first heat preservation at a low temperature (200-300°C) for a long time (3-10 h), the asphalt dopant solution maintains good fluidity and can repeatedly adsorb into the interconnected pore structure of the second precursor and the carbon matrix; then, by heat preservation at a high temperature (500-800°C) for 0.5-5 h... The purpose of this method is to induce pre-crosslinking and pre-doping reactions between the carbon microcrystal edges, soft carbon source, and dopant of the first precursor at high temperatures. The moderate rates of these reactions at this temperature ensure sufficient bonding and solidification between the carbon microcrystal edges, soft carbon source, and dopant, forming stable doped and bridging structures, suppressing defect generation, promoting crosslinking of carbon microcrystals, and improving porosity. Simultaneously, it avoids excessively rapid heating that could cause the volatile components generated by the cracking of the asphalt dopant solution to be carried out of the pores, leading to crosslinking reaction failure. Furthermore, it pre-carbonizes excess asphalt, preventing it from acting as a binder and causing particle adhesion during subsequent sintering. This ensures sufficient crosslinking reactions among the carbon microcrystals, dopant, and asphalt in the second precursor, resulting in a more uniform distribution of dopant elements within the carbon anode particles and the closed pore region, improving sodium storage activity and reducing polarization.

[0329] Test Example 2

[0330] Test samples: carbon anode materials provided in Examples 1-14 and carbon anode materials provided in Comparative Examples 1-11.

[0331] Test method:

[0332] (1) Testing of specific capacity and initial efficiency:

[0333] The carbon anode material, conductive agent, and binder obtained in each embodiment and comparative example were mixed at a mass ratio of 91:3:6. The mixture was adjusted to a solid content of 50% with deionized water, coated on one side of a copper foil current collector, dried at 130°C for 2 hours, and rolled to a surface density of 5.5 ± 0.5 mg / cm³. 2 The electrode is made by cutting the material into 14 mm diameter circular pieces; glass fiber GD-120 is used as the separator, sodium sheet with a diameter of 16 mm is used as the counter electrode, 1M NaPF6 in EC:DMC:EMC=1:1:1 (volume ratio) is used as the electrolyte, and CR2032 battery case is used to assemble it into a button cell.

[0334] At room temperature (around 25°C), the coin cells were tested using the Blue Battery Testing System. The nominal specific capacity was set to 300 mAh / g. The cells were first discharged at a constant current of 0.1 C to 1 mV, then discharged at a constant current of 50 μA to 1 mV, and then discharged at a constant current of 10 μA to 1 mV, at which point the discharge was stopped. After resting, the cells were charged again at 0.1 C, with a cutoff voltage of 2 V. Specific capacity (mAh / g) is the initial charge capacity divided by the weight of the carbon anode material contained in the anode sheet. The initial efficiency is the ratio of the initial charge capacity to the initial discharge capacity.

[0335] (2) Rate charging performance and room temperature cycling performance test:

[0336] BTR layered oxide BNH-O3A was used as the positive electrode. The positive electrode material, conductive agent, and binder were mixed in a mass percentage ratio of 96%:2%:2%. The mixture was then... N methylpyrrolidone was adjusted to a solid content of 50%, double-sided coated onto an aluminum foil current collector, dried, and rolled to control the areal density at 300 g / m². 2 Left and right, to obtain the positive electrode sheet.

[0337] The carbon anode material, conductive agent, and binder obtained in each embodiment and comparative example were mixed at a mass percentage of 91:3:6. The mixture was adjusted to a solid content of 50% with deionized water, coated on both sides onto a copper foil current collector, dried, and rolled to a surface density of 150 g / m². 2 Left and right, to obtain the negative electrode sheet;

[0338] The positive and negative electrodes were assembled into a 554065 type soft pack battery with a 20% NP excess ratio, a PP separator, and 1M NaPF6 in EC:DMC:EMC = 1:1:1 (volume ratio) as the electrolyte. The test voltage range was 2~4V.

[0339] (2-1) 6C / 1C rate charging retention rate (%) test: At room temperature, constant current charge and discharge tests were performed sequentially at different rates of 1C / 1C and 6C / 6C. The 6C charging capacity was divided by the 1C charging capacity to obtain the 6C / 1C rate charging retention rate.

[0340] (2-2) 1C / 1C@500-cycle retention rate (%) test: At room temperature, the 1C / 1C constant current charge-discharge cycle test was used. The discharge capacity of the 500th cycle was divided by the discharge capacity of the first cycle to obtain the 1C / 1C cycle 500-cycle retention rate.

[0341] The specific test results are shown in Table 2 below:

[0342] Table 2

[0343]

[0344] From Table 2 and Figure 10 As shown, the sodium-ion battery containing the carbon anode material described in this invention has a specific capacity of 275 mAh / g or higher, an initial efficiency of 85% or higher, a 6C / 1C charging capacity retention rate of 54% or higher, and a cycle retention rate of 1C / 1C@500 cycles at room temperature of 83% or higher. Specifically, the sodium-ion battery containing the carbon anode material provided in Examples 1-6, as a preferred embodiment, has a specific capacity of 325-385 mAh / g, an initial efficiency of 85.6-92.5%, a 6C / 1C charging capacity retention rate as high as 79.3-84.1%, and a cycle retention rate of 1C / 1C@500 cycles at room temperature as high as 91.7-96.4%. This demonstrates that the sodium-ion battery containing the carbon anode material described in this invention possesses advantages such as high capacity, high charging rate, and high cycle performance.

[0345] A comparison of Examples 1, 13, and 14 shows that the carbon anode materials provided in Examples 13-14 have inferior capacity, first-cycle efficiency, 6C / 1C charge capacity retention, and 1C / 1C@500-cycle capacity retention compared to the carbon anode material obtained in Example 1. When the sintering temperature is too high, the sodium storage capacity decreases instead of increasing, and electrochemical polarization increases; therefore, capacity, rate charging, cycling, and compaction density performance all decline. When the sintering temperature is too low, electrochemical polarization increases; therefore, capacity, rate charging, cycling, and compaction density performance all decline.

[0346] A comparison between Example 1 and Comparative Example 1 shows that the capacity, first-time efficiency, 6C / 1C charging capacity retention rate, and 1C / 1C@500-cycle retention rate of the carbon anode material obtained in Comparative Example 1 are all inferior to those of the carbon anode material obtained in Example 1. Comparative Example 1 prepared the carbon anode material by directly combining a hard carbon source and a dopant followed by pre-carbonization. During the pre-carbonization process, the dopant could not be incorporated into the hard carbon particles, and the dopant reacted with the tar components from the cracking of the hard carbon source, inhibiting the removal of tar components. The tar components occupied sodium storage sites, suppressing the porosity of the hard carbon and reducing its interlayer density, resulting in a smaller heteroatom distribution coefficient and closed pore volume. This led to a decrease in the specific capacity, rate charging, and cycle performance of the obtained carbon anode material. Therefore, it is not feasible to directly combine the dopant with the hard carbon source and then simultaneously perform high-temperature treatment, pre-carbonization, and doping.

[0347] A comparison of Example 1 with Comparative Examples 2, 4, and 5 shows that the capacity, initial efficiency, 6C / 1C charging capacity retention, and 1C / 1C@500-cycle retention of the carbon anode materials in Comparative Examples 2, 4, and 5 are all inferior to those of the carbon anode material obtained in Example 1. In these methods, the doping elements are mainly concentrated on the surface of the carbon anode material particles, resulting in low heteroatom distribution coefficients and powder conductivity. The doping elements cannot fully bond with the hard carbon components, and they cannot improve the degree of microcrystalline cross-linking, catalyze the conversion of "open pores" to "closed pores," or enhance the conductivity of the pore region. Therefore, the effect of doping on improving capacity, rate capability, and cycle performance is poor. In contrast, this invention can improve the uniformity of doping element distribution within the carbon anode particles, increase the degree of carbon microcrystalline cross-linking, increase the number of closed pores in the carbon anode material, and enhance the sodium storage activity in the closed pore region, thereby improving the capacity, initial efficiency, rate charging, and cycle performance of hard carbon.

[0348] A comparison of Example 1 with Comparative Examples 3 and 6 shows that the capacity, initial efficiency, 6C / 1C charging capacity retention, and 1C / 1C@500-cycle retention of the carbon anode materials in Comparative Examples 3 and 6 are all inferior to those of the carbon anode material obtained in Example 1. This indicates that combining pore formation and modification can improve the content and distribution uniformity of impurity elements, the closed pore volume, and conductivity, thereby enhancing the capacity, initial efficiency, rate charging, and cycle performance of hard carbon anodes. This invention, by combining pore formation and modification, possesses significant technical advantages.

[0349] A comparison of Example 1 with Comparative Examples 7, 8, and 9 shows that the capacity, initial efficiency, 6C / 1C charge capacity retention, and 1C / 1C@500 cycle retention of the carbon anode materials in Comparative Examples 7, 8, and 9 are all inferior to those of the carbon anode material obtained in Example 1. Comparative Examples 7 and 8 fail to achieve uniform distribution of dopant elements near the closed pores, resulting in low sodium storage activity and high polarization in the closed pores. Consequently, the capacity, initial efficiency, rate charging, and cycle performance of the resulting carbon anode materials are inferior to those of Example 1. Comparative Example 9, based on Example 1, uses asphalt melt instead of asphalt dopant to react with the second precursor. Its electrochemical performance is inferior to that of Example 1 because the dopant in the asphalt dopant in this invention catalyzes the crosslinking of hard carbon microcrystals and soft carbon sources, promoting the transformation of "open pores" into "closed pores," and improving the conductivity and sodium storage activity of the closed pore region. The reaction between the second precursor and the asphalt melt cannot achieve the same effect as the reaction with the asphalt dopant. This demonstrates that the present invention has significant technical advantages in combining asphalt doping liquid (soft carbon source, dopant) and VC heating in step (3).

[0350] The comparison between Example 1 and Comparative Examples 10 and 11 shows that the capacity, first efficiency, 6C / 1C charging capacity retention rate, and 1C / 1C@500 cycle retention rate of the carbon anode materials of Comparative Examples 10 and 11 are all worse than those of the carbon anode material obtained in Example 1. Comparative Example 10 only performed low-temperature doping (250℃ for 8 h) in the VC heating doping stage of step (3), without high-temperature (500~800℃) doping; Comparative Example 11 only performed high-temperature doping (800℃ for 8 h) in the VC heating doping stage of step (3), without low-temperature (200~300℃) doping; This shows that the doping process of the hetero-elements in this invention further improves the uniform distribution coefficient of hetero-elements through a specific heat preservation procedure; wherein, firstly, the asphalt dopant is kept at a low temperature (200~300℃) for a long time (3~10 h), which allows it to maintain good fluidity and repeatedly adsorb into the interconnected pore structure and carbon matrix of the second precursor; then, it is kept at a high temperature (500~800℃) for 0.5~5 h. h, by using high temperature, pre-crosslinking and pre-doping reactions occur between the carbon microcrystal edges, soft carbon source, and dopant of the first precursor. At this temperature, the rates of these pre-crosslinking and pre-doping reactions are moderate, ensuring sufficient bonding and solidification between the carbon microcrystal edges, soft carbon source, and dopant, forming a stable doped and bridging structure, suppressing defect generation, promoting the interconnection of carbon microcrystals through crosslinking, and improving porosity. This ensures sufficient crosslinking reactions among the carbon microcrystals, dopant, and pitch in the second precursor, resulting in a more uniform distribution of doped elements within the carbon anode particles and the closed pore region, improving sodium storage activity, reducing polarization, and enhancing capacity, rate capability, and cycle performance. Therefore, this application's doping reaction using a specific temperature-controlled procedure has significant technical advantages.

[0351] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A carbon negative electrode material, characterized by, The carbon negative electrode material includes hard carbon and a hetero-element dispersed in the interior of the hard carbon; and the hetero-element content distribution coefficient of the carbon negative electrode material is 25-175%; The calculation formula of the hetero-element content distribution coefficient of the carbon negative electrode material is as follows: Distribution coefficient of hetero-element content (%) ; Wherein, S is the integral area of the mass concentration of the hetero-element along AB displacement in EDS testing, AB is the longest line segment distributed in the cross section of the carbon negative electrode material particle; a and b are the mass concentrations of the hetero-element at points A and B, respectively; R is the distance between points AB; The carbon negative electrode material includes a closed pore. The closed pore volume of the carbon negative electrode material is 0.04-0.3 cm3 / g 3 / g; The hetero-element is distributed at least in the closed pore region. The hetero-element includes any one or a combination of at least two of nitrogen, phosphorus or sulfur. The content of the hetero-element in the carbon negative electrode material is 0.4-5 wt%. The electrical conductivity of the carbon negative electrode material is 42-50 S / cm.

2. The carbon negative electrode material according to claim 1, characterized in that, The carbon negative electrode material at least meets one of the following conditions: (a) The hetero-element content distribution coefficient of the carbon negative electrode material is 50-150%; (d) The carbon layer spacing of the carbon negative electrode material is 0.37-0.39 nm; (e) The carbon negative electrode material includes soft carbon dispersed in the interior of the hard carbon, and the soft carbon fills the pores of the hard carbon to form a closed pore; (g) the 3T powder compaction density of the carbon negative electrode material is 1.0-1.1 g / cm 3 ; (i) The median particle size of the carbon negative electrode material is 4-15 μm; (j) the true density of the carbon negative electrode material is 1.56 ~ 2.06 g / cm 3 ; (k) the carbon negative electrode material has a specific surface area of 1.5 to 8.0 m 2 / g.

3. A method of producing the carbon negative electrode material according to claim 1 or 2, characterized by, The preparation method includes: (1) Pre-carbonizing, crushing and pore-forming a carbon source to obtain a first precursor; (2) Modifying the first precursor to obtain a second precursor; wherein the modification reaction includes mixing the first precursor with an oxidizing acid solution to perform a modification reaction to obtain a second precursor; (3) Mixing the second precursor and a pitch doping solution to perform doping treatment to obtain a third precursor; the pitch doping solution includes a dopant and liquid pitch; wherein the doping treatment includes mixing the second precursor and the pitch doping solution, then first heating to 200-300℃ for 3-10 h, and then heating to 500-800℃ for 0.5-5 h to obtain the third precursor; the dopant includes any one or a combination of at least two of a nitrogen source, a phosphorus source or a sulfur source; (4) Sintering the third precursor to obtain the carbon negative electrode material; wherein the sintering temperature is 1150-1400℃, and the sintering time is 0.25-10 h.

4. The method of claim 3, wherein the carbon negative electrode material is prepared by a process comprising: In step (1), the carbon source includes any one or a combination of at least two of a plant-based carbon source, a sugar-based carbon source, a resin-based carbon source or a polymer-based carbon source. ​ 5. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (1), the pre-carbonization temperature is 450-650℃, and the pre-carbonization holding time is 0.5-24 h.

6. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (1), the crushing includes crushing the pre-carbonized material to a median particle size of 3-15 μm to obtain a crushed pre-carbonized material.

7. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (1), the pore-forming includes mixing the crushed pre-carbonized material and a solid pore-forming agent, and performing pore-forming treatment to obtain a solid pore-forming modified material.

8. The method for preparing the carbon anode material according to claim 7, characterized in that, The mass ratio of the pulverized pre-carbonized material to the solid-phase pore-forming agent is 1:(0.5-3.0).

9. The method of claim 7, wherein the carbon negative electrode material is prepared by a process comprising: The solid-phase pore-forming agent includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium oxide, or zinc chloride. ​ 10. The method of claim 7, wherein the carbon negative electrode material is prepared by a process comprising: The pore-forming treatment has a temperature of 400-700°C and a time of 0.25-24 h. ​ 11. The method of claim 7, wherein the carbon negative electrode material is prepared by a process comprising: The pore-forming treatment further includes a purification treatment, which includes: ​ The solid-phase pore-forming modification material is washed with pure water until the pH is 8-10 to obtain a purified product one; the purified product one, an acid, and pure water are mixed and stirred to obtain a purified product two; the purified product two is washed with pure water until the pH is 4-8, and then solid-liquid separation and drying are performed to obtain a purified first precursor.

12. The method of claim 11, wherein the carbon negative electrode material is prepared by a process comprising: The acid includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid, or sulfuric acid. ​ 13. The method for preparing the carbon anode material according to claim 3, characterized in that, The mass ratio of the first precursor to the oxidizing acid solution is 1:(3-20).

14. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (2), the oxidizing acid solution includes an oxidizing solute and an acid.

15. The method for preparing the carbon anode material according to claim 14, characterized in that, The oxidizing solute includes any one or a combination of at least two of potassium permanganate, potassium dichromate, potassium perchlorate, potassium hypochlorite, sodium permanganate, sodium dichromate, sodium perchlorate, sodium hypochlorite, or hydrogen peroxide.

16. The method of claim 14, wherein the carbon negative electrode material is prepared by a process comprising: The acid includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, phosphoric acid, sulfuric acid, or nitric acid.

17. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (2), the oxidizing acid solution includes, based on the total mass of the oxidizing acid solution being 100%, by mass percentage: 0.3-5% of the oxidizing solute, 3-10% of the acid, and the balance being water.

18. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (2), the modification reaction has a temperature of 50-100°C and a time of 0.5-24 h.

19. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (3), the mass ratio of the second precursor to the pitch doping solution is (75-95):(25-5).

20. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (3), the mixing of the second precursor and the pitch doping solution includes: The pitch doping solution is added to the second precursor under low-speed stirring; wherein the low-speed stirring has a speed of 20-30 r / min.

21. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (3), the process of the heat preservation is performed under stirring; wherein the stirring has a speed of 100-500 r / min.

22. The method for preparing the carbon anode material according to claim 3, characterized in that, In step (3), the preparation of the pitch doping solution includes: The pitch is heated and melted to obtain a liquid pitch; a dopant is added to the liquid pitch and stirred until dissolved to obtain the pitch doping solution.

23. The method for preparing the carbon anode material according to claim 22, characterized in that, The pitch doping solution includes a dopant and liquid pitch in a mass ratio of (0.1-1):

1.

24. A negative electrode sheet characterized by comprising: The negative electrode sheet includes the carbon negative electrode material of claim 1 or 2.

25. A sodium-ion battery, characterized in that, The sodium ion battery includes the negative electrode sheet of claim 24.

26. An electrical device, comprising: The electrical equipment includes the sodium ion battery of claim 25.

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