Carbon negative electrode material and preparation method thereof, negative electrode plate, sodium ion battery and power-related equipment

Abstract

The invention provides a carbon negative electrode material and a preparation method thereof, a negative electrode plate, a sodium ion battery and electric equipment. The carbon negative electrode material comprises hard carbon and miscellaneous elements dispersed in the hard carbon, and the impurity element content distribution coefficient of the carbon negative electrode material is 25-175%. Mixed elements in the carbon negative electrode material are fully and uniformly dispersed in the hard carbon, are uniformly distributed in carbon material particles and are fully bonded with carbon elements, so that a large number of uniformly distributed active sites are formed, and the conductivity effect is improved; the mixed elements are located in the carbon negative electrode material, and the hard carbon physically isolates the electrolyte, so that the side reaction between the mixed elements and the electrolyte is effectively reduced, and the capacity and the cycle performance of the negative electrode material are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, and particularly relates to a carbon negative electrode material, a preparation method thereof, a negative electrode sheet, a sodium ion battery and an electrical equipment. BACKGROUND

[0002] Sodium ion batteries have the advantages of low-temperature resistance, fast charging, high safety, low cost, long service life and the like, and have similar working principles to lithium ion batteries, and can be used as complementary or partial replacement power supply devices of lithium ion batteries. Moreover, sodium resources are abundant on the earth, and the total amount of sodium salt is 500 times that of lithium salt, and the refining cost is low. Therefore, the sodium ion battery system has good development potential and market prospect in large-scale energy storage in the future. Hard carbon material has a large interlayer spacing and exhibits high capacity and low potential, and is a main commercial sodium ion battery negative electrode material, and is a decisive factor for large-scale application of sodium ion batteries.

[0003] Currently, the core technical bottleneck of the application of sodium ion batteries is difficult to improve the energy density, and one of the keys to improving the energy density is to improve the capacity performance of hard carbon material. A large number of defects and pores exist in the hard carbon material, which makes the capacity performance of the carbon negative electrode material low. In addition, the disordered structure of the hard carbon material itself also causes the electronic conductivity of the material to deviate, which affects the fast charging and power performance. Therefore, in some related technologies, the main technical bottleneck of hard carbon used in sodium ion batteries is difficult to balance the energy density and the kinetic (fast charging, service life) performance. There are many methods to improve the performance of hard carbon material, such as soft and hard carbon composite or heteroatom doping.

[0004] The soft and hard carbon composite is to combine the structural advantages of soft carbon (high order degree, good conductivity) and hard carbon (rich closed pores, high platform capacity) to realize performance complementation. However, the common soft and hard carbon composite method directly uses hard carbon source and soft carbon source for compounding, the hard carbon source is limited to a few soluble or meltable carbon sources, the compounding process is harsh, it is difficult to scale up, and the carbon interlayer spacing and porosity of the obtained carbon material are small and low, and then the fast charging and service life performance of the sodium ion battery prepared therefrom are poor.

[0005] Heteroatom doping is to use heteroatoms (such as N, P, S, etc.) to dope and modify to increase the defects of the carbon material, thereby improving the capacity performance. However, the conventional heteroatom doping method is to directly use carbon material and dopant for solid-phase mixing and high-temperature sintering, the heteroatoms are mainly doped on the surface and open pore area of the carbon material, and are difficult to penetrate into the interior of the carbon particles, resulting in the phenomenon of “surface heteroatom supersaturation and inner layer heteroatom deficiency” (as shown in Figure 1 The effect of “doping and increasing capacity” of the carbon material is limited, and the heteroatoms are prone to side reactions with the electrolyte, which causes the service life performance of the carbon material to decrease.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The present application provides a carbon negative electrode material, a preparation method thereof, a negative electrode sheet, a sodium ion battery and an electrical equipment, aiming to solve the technical problem that the impurity elements are mainly doped on the surface and open pore area of the carbon material, and are difficult to penetrate into the interior of the carbon particles, so that the impurity elements can be fully and uniformly dispersed in the interior of the carbon negative electrode material.

[0008] In a first aspect, the present application provides a carbon negative electrode material, which comprises hard carbon and impurity elements dispersed in the interior of the hard carbon, and the impurity element content distribution coefficient of the carbon negative electrode material is 25-175%.

[0009] Further, the impurity element content distribution coefficient of the carbon negative electrode material is 50-150%.

[0010] Further, the impurity element content distribution coefficient of the carbon negative electrode material is 75-125%.

[0011] Further, the impurity elements include any one or a combination of at least two of nitrogen, phosphorus or sulfur.

[0012] Further, the content of the impurity elements in the carbon negative electrode material is 0.4-5 wt%.

[0013] Further, the carbon layer spacing of the carbon negative electrode material is 0.37-0.39 nm.

[0014] Further, the carbon negative electrode material comprises soft carbon dispersed in the interior of the hard carbon, and the soft carbon is filled in the pores of the hard carbon to form closed pores.

[0015] Further, the closed pore volume of the carbon negative electrode material is 0.04-0.3 cm 3 / g.

[0016] Further, the 3T powder compaction density of the carbon negative electrode material is 1.0-1.1 g / cm 3 .

[0017] Further, the electrical conductivity of the carbon negative electrode material is 26-52 S / cm, preferably 42-50 S / cm.

[0018] Further, the median particle size of the carbon negative electrode material is 4-15 μm.

[0019] Further, the true density of the carbon negative electrode material is 1.56-2.06 g / cm 3 .

[0020] Further, the specific surface area of the carbon negative electrode material is 1.5-8.0 m 2 / g.

[0021] In a second aspect, the present application provides a preparation method of the carbon negative electrode material according to the first aspect, the preparation method comprising: (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; (3) mixing the second precursor and a pitch doping solution to perform doping treatment to obtain a third precursor; the pitch doping solution comprising a dopant and liquid pitch; (4) sintering the third precursor to obtain the carbon negative electrode material.

[0022] Further, in step (1), the carbon source comprises 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.

[0023] Further, the plant-based carbon source comprises any one or a combination of at least two of coconut shell, apricot kernel shell, pistachio shell, macadamia nut shell, jujube kernel shell, chestnut shell, hazelnut shell, peanut shell, walnut shell, peach kernel shell, cotton, wood, bamboo, bagasse, straw or lignin.

[0024] Further, the sugar-based carbon source comprises any one or a combination of at least two of glucose, sucrose, maltose, lactose, fructose, starch or cellulose.

[0025] Further, the resin-based carbon source comprises any one or a combination of at least two of phenolic resin, polyimide resin, polyester resin, polyaldehyde resin, polyolefin resin or polyacrylic acid resin.

[0026] Further, the polymer-based carbon source comprises any one or a combination of at least two of polyfurfuryl alcohol, polyaniline, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, natural rubber or polyacrylonitrile.

[0027] Further, in step (1), the pre-carbonization temperature is 450-650°C, and the pre-carbonization holding time is 0.5-24 h.

[0028] Further, in step (1), the pre-carbonization is performed under an inert gas atmosphere.

[0029] Further, in step (1), in the pre-carbonization, the inert gas atmosphere comprises any one or a combination of at least two of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton.

[0030] Further, in step (1), the pre-carbonization is performed in a carbonization furnace.

[0031] Further, in step (1), the carbonization furnace comprises any one or a combination of at least two of a tube furnace, a box furnace, a pusher kiln, or a roller kiln.

[0032] Further, in step (1), the pulverization comprises: pulverizing the pre-carbonized material to a median particle size of 3-15 μm to obtain a pulverized pre-carbonized material.

[0033] Further, in step (1), the pulverization employs a device comprising any one or a combination of at least two of a mechanical pulverizer, a roller mill, an air flow pulverizer, or a ball mill.

[0034] Further, in step (1), the pore formation comprises: mixing the pulverized pre-carbonized material and a solid-phase pore-forming agent, and performing a pore formation treatment to obtain a solid-phase pore-forming modified material.

[0035] Further, a mass ratio of the pulverized pre-carbonized material to the solid-phase pore-forming agent is 1:(0.5-3.0).

[0036] Further, the solid-phase 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.

[0037] Further, in step (1), the pore formation treatment is performed at a temperature of 400-700 °C and for a time of 0.25-24 h.

[0038] Further, in step (1), the pore formation treatment is performed under an inert gas atmosphere and / or an oxygen-poor atmosphere.

[0039] Further, in step (1), in the pore formation treatment, the inert gas atmosphere comprises any one or a combination of at least two of a nitrogen atmosphere, an argon atmosphere, a neon atmosphere, a helium atmosphere, a xenon atmosphere, or a krypton atmosphere.

[0040] Further, in step (1), in the pore formation treatment, the oxygen-poor atmosphere is a gas atmosphere with an oxygen content of ≤1 wt%. Further, in step (1), after the pore formation treatment, a purification treatment is further performed, which comprises: washing the solid-phase pore-forming modified material with pure water to a pH of 8-10 to obtain a purified product one; mixing the purified product one, an acid, and pure water to obtain a purified product two; washing the purified product two with pure water to a pH of 4-8, and then performing solid-liquid separation and drying to obtain a purified first precursor.

[0041] Further, in step (1), in the purification treatment, the acid comprises any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid or sulfuric acid.

[0042] Further, in step (2), the modification reaction comprises: mixing the first precursor with an oxidizing acid solution to perform a modification reaction to obtain a second precursor.

[0043] Further, in step (2), the mass ratio of the first precursor to the oxidizing acid solution is 1:(3-20).

[0044] Further, in step (2), the oxidizing acid solution comprises an oxidizing solute and an acid.

[0045] Further, in step (2), the oxidizing solute comprises 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.

[0046] Further, in step (2), in the oxidizing acid solution, the acid comprises 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 30-95 wt%.

[0047] Further, the oxidizing acid solution comprises, by mass percentage, based on the total mass of the oxidizing acid solution being 100%, 0.3-5% of the oxidizing solute, 3-10% of the acid, and the balance being water.

[0048] Further, in step (2), the temperature of the modification reaction is 50-100°C, and the time of the modification reaction is 0.5-24 h.

[0049] Further, in step (3), the doping treatment comprises: mixing the second precursor and a pitch doping solution, then heating to 200-300°C for 3-10 h, and then heating to 500-800°C for 0.5-5 h to obtain a third precursor.

[0050] Further, in step (3), the mass ratio of the second precursor to the pitch doping solution is (75-95):(25-5).

[0051] Further, in step (3), the mixing of the second precursor and the pitch doping solution comprises: adding the pitch doping solution to the second precursor under low-speed stirring; wherein the rotation speed of the low-speed stirring is 20-30 r / min.

[0052] Further, in step (3), the process of the heat preservation is performed under stirring; wherein the stirring speed is 100-500 r / min.

[0053] Further, in step (3), the process of the heat preservation is performed under an inert gas atmosphere.

[0054] Further, in step (3), 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.

[0055] Further, in step (3), the preparation of the asphalt doping 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 doping solution.

[0056] Further, the asphalt doping solution includes a dopant and liquid asphalt in a mass ratio of (0.1-1):1.

[0057] Further, the dopant includes any one or a combination of at least two of a nitrogen source, a phosphorus source or a sulfur source.

[0058] Further, the nitrogen source includes any one or a combination of at least two of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acid or ammonium bicarbonate.

[0059] Further, the phosphorus source includes any one or a combination of at least two of phosphorus trichloride, phosphorus pentoxide, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate or phosphate ester.

[0060] Further, 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.

[0061] Further, in step (4), the sintering temperature is 1100-1400℃, and the sintering time is 0.25-10 h.

[0062] Further, in step (4), the sintering is performed under an inert gas atmosphere.

[0063] Further, in step (4), during the sintering, 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.

[0064] Further, in step (4), the sintering is performed in a sintering furnace.

[0065] Further, in step (4), the sintering furnace comprises any one or a combination of at least two of a tube furnace, a box furnace, a roller kiln, or a rotary furnace.

[0066] In a third aspect, the present application provides a negative electrode sheet, which comprises the carbon negative electrode material according to the first aspect.

[0067] In a fourth aspect, the present application provides a sodium ion battery, which comprises the negative electrode sheet according to the third aspect.

[0068] In a fifth aspect, the present application provides an electrical equipment, which comprises the sodium ion battery according to the fourth aspect.

[0069] Compared with the prior art, the present application has the following beneficial effects: (1) In the carbon negative electrode material, the impurity elements are fully and uniformly dispersed in the interior of the hard carbon, which are uniformly 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, improving the conductivity and ensuring the effect of "doping and increasing capacity" of the carbon material.

[0070] (2) In the carbon negative electrode material, the soft carbon is dispersed in the interior of the hard carbon, and in the presence of the impurity elements, the soft and hard carbons are fully and uniformly compounded, and at the same time, the soft carbon plays a "plugging hole" role and fills the pores of the hard carbon to form closed pores, so that the obtained carbon negative electrode material has the advantages of large interlayer spacing, many closed pores, and dense structure, thereby making the negative electrode material exhibit the advantages of high capacity, high rate, and high compaction.

[0071] (3) The preparation method of the carbon negative electrode material comprises the following steps: pre-carbonizing the hard carbon source to remove tar components and construct a connected pore structure; modifying the reaction to improve the porosity and the number of crosslinking functional groups to provide sites for doping reaction, to obtain a second precursor; embedding the soft carbon source into the interior of the hard carbon particles (second precursor) under heating according to the thermoplastic (good flowability under heating) characteristics of the soft carbon source; and finally, through high-temperature reaction, the hard carbon carbon microcrystal, the soft carbon source, and the doping agent are catalytically crosslinked, and the nanoscale soft carbon and the impurity elements are dispersed in the interior of the hard carbon, to realize the full and uniform compounding between the soft and hard carbons; wherein, the second precursor provides a carbon skeleton, the soft carbon source molecules play a "plugging hole" role (convert "open pores" into "closed pores"), and the doping agent plays a catalytic crosslinking role of the hard carbon carbon microcrystal and the soft carbon source. BRIEF DESCRIPTION OF DRAWINGS

[0072] In order to more clearly illustrate the solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0073] Figure 1 A schematic diagram of the mechanism of the heteroatom doping modification method of the existing carbon material in the background art.

[0074] Figure 2 A schematic diagram of the structure of the carbon negative electrode material.

[0075] In the figure, 100 represents a hetero element, and 200 represents a closed pore.

[0076] Figure 3 A flow chart of the preparation process of the carbon negative electrode material.

[0077] Figure 4 A schematic diagram of the mechanism of the heteroatom doping modification method of the carbon negative electrode material.

[0078] Figure 5A A schematic diagram of the line scanning path of the cross section of the carbon negative electrode material in the test of the hetero element content distribution coefficient.

[0079] Figure 5B A mass concentration (y) - line scanning displacement (x) curve of impurities in the test of the hetero element content distribution coefficient.

[0080] Figure 6 A scanning electron microscope image of the carbon negative electrode material provided in Example 1.

[0081] Figure 7 A scanning electron microscope image of the carbon negative electrode material provided in Comparative Example 1.

[0082] Figure 8 An XRD curve of the carbon negative electrode material provided in Example 1, Comparative Example 5 and Comparative Example 8.

[0083] Figure 9 A microstructure comparison diagram of the carbon negative electrode material provided in Example 1 and Comparative Example 2.

[0084] In the figure, 100 represents a hetero element, and 200 represents a closed pore.

[0085] Figure 10 A first charge-discharge curve of the carbon negative electrode material provided in Example 1, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0086] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0087] In order to solve the technical problem that the heteroelements are mainly doped on the surface and open hole area of the carbon material, but it is difficult to penetrate into the interior of the carbon particles, the present application provides a carbon negative electrode material, which comprises hard carbon and heteroelements dispersed in the interior of the hard carbon.

[0088] As shown in Figure 2 The heteroelements 100 are fully and uniformly dispersed in the interior of the carbon negative electrode material, are uniformly distributed in the interior of the carbon material particles, and are fully bonded with carbon elements, a large number of active sites are formed in the interior, the effect of "doping and increasing capacity" of the carbon material is ensured, the heteroelements are in the interior of the carbon negative electrode material, the hard carbon physically separates the electrolyte, effectively reduces the side reaction of the heteroelements and the electrolyte, and significantly improves the capacity and cycle performance of the carbon material.

[0089] In an embodiment, the content distribution coefficient of the heteroelements of the carbon negative electrode material is 25-175%, for example, 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.

[0090] In an embodiment, the content distribution coefficient of the heteroelements of the carbon negative electrode material is 50-150%.

[0091] In an embodiment, the content distribution coefficient of the heteroelements of the carbon negative electrode material is 75-125%.

[0092] In an embodiment, the heteroelements include any one or a combination of at least two of nitrogen (N), phosphorus (P) or sulfur (S).

[0093] 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.

[0094] 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.

[0095] 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.

[0096] like Figure 2 As 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.

[0097] 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.

[0098] In an embodiment, the 3T powder compaction density of the carbon negative electrode material is 1.0-1.1 g / cm 3 , for example, can be 1.0 g / cm 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 , etc.

[0099] In an embodiment, the electrical conductivity of the carbon negative electrode material is 26-52 S / cm, for example, can be 26 S / cm, 30 S / cm, 36 S / cm, 40 S / cm, 46 S / cm, 50 S / cm, 52 S / cm, etc.

[0100] In an embodiment, the electrical conductivity of the carbon negative electrode material is 42-52 S / cm, for example, 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, 47.8 S / cm, 48 S / cm, 48.2 S / cm, 48.4 S / 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, 50 S / cm, etc.

[0101] In the present application, a large number of heterogeneous elements are distributed in the closed pore region, significantly increasing the electron cloud density of the closed pores, thereby improving the powder conductivity of the carbon negative electrode material to more than 42 S / cm, and then improving the sodium storage activity of the closed pores, inhibiting electrochemical polarization, and further improving the capacity performance of the carbon material.

[0102] In an embodiment, the carbon negative electrode material has a median particle size of 4-15 μm, for example, 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.

[0103] In an embodiment, the carbon negative electrode material has a true density of 1.56-2.06 g / cm 3 , for example, 1.56 g / cm 3 , 1.58 g / cm 3 , 1.60 g / cm 3 , 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 , etc.

[0104] In an embodiment, the specific surface area of the carbon negative electrode material is 1.5-8.0 m 2 / g, for example, can 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, 6.0 m 2 / g, 6.5 m 2 / g, 7.0 m 2 / g, 7.5 m 2 / g, 8.0 m 2 / g, etc.

[0105] The present application also provides a preparation method of the carbon negative electrode material according to the first aspect, which comprises: (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; (3) mixing the second precursor and a pitch doping solution to perform doping treatment to obtain a third precursor; the pitch doping solution comprises a dopant and liquid pitch; (4) sintering the third precursor to obtain the carbon negative electrode material.

[0106] As Figure 3 shown in the preparation method of the carbon negative electrode material according to the present application: first, a first precursor with a porous structure and carbon microcrystals is prepared by pre-carbonizing and pore-forming; then, a second precursor is obtained by removing low-molecular-weight carbon chains in the first precursor through a modification reaction, increasing cross-linking functional groups and porosity; next, a third precursor is obtained by mixing the second precursor and a pitch doping solution and performing doping treatment under heating, so that soft carbon sources and dopants are fully adsorbed in the pore structure and matrix of the second precursor; finally, high-temperature sintering is performed to realize cross-linking reactions of soft carbon source molecules, dopants and "carbon microcrystals" of hard carbon, thereby obtaining the carbon negative electrode material.

[0107] 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.

[0108] Meanwhile, the carbon anode material of this invention employs a novel heteroatom doping method, such as... Figure 4 As 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] In an embodiment, the polymer-based carbon source comprises any one of polyfurfuryl alcohol, polyaniline, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, natural rubber, or polyacrylonitrile, or a combination of at least two thereof.

[0114] In an embodiment, in step (1), the pre-carbonization is performed at a temperature of 450-650°C, for example, at 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, or the like.

[0115] In an embodiment, in step (1), the pre-carbonization is performed for a holding time of 0.5-24 h, for example, for 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, 22 h, 23 h, 24 h, or the like.

[0116] In an embodiment, in step (1), the pre-carbonization is performed under an inert gas atmosphere.

[0117] In an embodiment, in step (1), the inert gas atmosphere in the pre-carbonization comprises any one of a nitrogen atmosphere, an argon atmosphere, a neon atmosphere, a helium atmosphere, a xenon atmosphere, or krypton, or a combination of at least two thereof.

[0118] In an embodiment, in step (1), the pre-carbonization is performed in a carbonization furnace.

[0119] In an embodiment, in step (1), the carbonization furnace comprises any one of a tube furnace, a box furnace, a pusher kiln, or a roller kiln, or a combination of at least two thereof.

[0120] In an embodiment, in step (1), the pulverization comprises pulverizing the pre-carbonized material to a median particle size of 3-15 μm to obtain a pulverized pre-carbonized material.

[0121] In an embodiment, in step (1), the pulverization is performed using a device comprising any one of a mechanical pulverizer, a roller mill, an air jet pulverizer, or a ball mill, or a combination of at least two thereof.

[0122] In one embodiment, in step (1), the pore-forming includes: mixing the crushed pre-carbonized material and the solid-phase pore-forming agent, and performing a pore-forming treatment to obtain a solid-phase pore-forming modified material.

[0123] In one embodiment, the mass ratio of the crushed pre-carbonized material and the solid-phase 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.

[0124] In one embodiment, 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.

[0125] In one embodiment, in step (1), the pore-forming treatment is performed at a temperature of 400~700℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, etc.

[0126] In one embodiment, in step (1), the pore-forming treatment is performed for a time of 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, 22 h, 23 h, 24 h, etc.

[0127] In one embodiment, in step (1), the pore-forming treatment is performed under an inert gas atmosphere and / or an oxygen-poor atmosphere.

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

[0129] In one embodiment, in step (1), in the pore-forming treatment, the oxygen-poor atmosphere is a gas atmosphere with an oxygen content ≤1 wt%.

[0130] In one embodiment, in step (1), the pore-forming treatment further includes a purification treatment, and the purification treatment 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, 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.

[0131] In one embodiment, in the purification treatment in step (1), the acid includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid or sulfuric acid.

[0132] In one embodiment, in step (2), the modification reaction includes: mixing the first precursor with an oxidizing acid solution to perform a modification reaction to obtain a second precursor.

[0133] In the present application, in step (2), the first precursor is mixed with an oxidizing acid solution to perform a modification reaction, which improves the porosity and the number of cross-linking functional groups to provide sites for doping reaction, and obtains a second precursor.

[0134] In the modification reaction, the oxidizing solution can be immersed into the first precursor from the opening to react with groups (alkyl, alkenyl, alkynyl, aldehyde group, etc.) that lack cross-linking reaction activity and are connected to the carbon atoms at the edge of the carbon microcrystal, so that these groups are cracked to generate abundant new pores or increase the pore size of the existing pores, and / or are converted into cross-linking functional groups (functional groups with cross-linking activity, such as hydroxyl, carboxyl, nitro, sulfonic acid group). The pores generated by the modification reaction or the increase in the pore size of the existing pores can provide a channel for the soft carbon source and the dopant to enter the region near the edge of the carbon microcrystal, and the cross-linking functional groups provide reaction sites for the cross-linking reaction between the edge of the microcrystal of the first precursor and the soft carbon source and the dopant. The new pores generated by the cracking are mainly ultramicro-pores, which have the characteristics of small pore size (<1 nm) and do not significantly reduce the density performance of the obtained carbon negative electrode. The carbon material that has not undergone the modification reaction lacks channels for the pitch doping solution to enter the carbon matrix and cross-linking functional groups to react with the pitch doping solution, which leads to the fact that the doping and cross-linking reactions cannot occur in the region near the edge of the carbon material microcrystal, but occur on the surface of the carbon material and in some opening pore wall regions.

[0135] In one embodiment, in step (2), the mass ratio of the first precursor to the oxidizing acid solution is 1:(3-20), which 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.

[0136] In one embodiment, in step (2), the oxidizing acid solution includes an oxidizing solute and an acid.

[0137] 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.

[0138] In one embodiment, in step (2), in the oxidizing acid solution, the acid includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, phosphoric acid, sulfuric acid, or nitric acid.

[0139] In one embodiment, in step (2), in the oxidizing acid solution, the concentration of the acid is 30-95 wt%, for example, 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 here refers to the initial concentration of the acid itself, not the final concentration of the final acid in the oxidizing acid solution).

[0140] In one embodiment, the oxidizing acid solution includes, by mass percentage, based on the total mass of the oxidizing acid solution being 100%, the oxidizing solute 0.3-5% (for example, can be 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.), the acid 3-10% (for example, can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.), and the balance being water.

[0141] In one embodiment, in step (2), the temperature of the modification reaction is 50-100°C, for example, can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.

[0142] In one embodiment, in step (2), the time of the modification reaction is 0.5-24 h, for example, 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, 22 h, 23 h, 24 h, etc.

[0143] In an embodiment, in step (3), the doping treatment comprises: after mixing the second precursor and the pitch doping solution, first heating to 200-300°C (for example, it can be 200°C, 220°C, 240°C, 250°C, 260°C, 280°C, 300°C, etc.) and keeping for 3-10 hours (for example, it can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.), and then heating to 500-800°C (for example, it can be 500°C, 520°C, 540°C, 550°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 750°C, 760°C, 780°C, 800°C, etc.) and keeping for 0.5-5 hours (for example, it can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc.), to obtain a third precursor.

[0144] In the present application, the uniform distribution coefficient of the impurity elements is further improved by the specific heat preservation procedure described above. First, the pitch doping solution can maintain good fluidity and can be adsorbed into the connected pore structure and carbon matrix of the second precursor by keeping at a low temperature (250-300°C) for a long time (3-10 hours). Then, the purpose is to make the first precursor carbon microcrystal edge, soft carbon source, and dopant have a pre-crosslinking reaction at a high temperature (500-800°C) for 0.5-5 hours. The pre-crosslinking reaction speed at this temperature is moderate, which can ensure that the carbon microcrystal edge, soft carbon source, and dopant are fully bonded and solidified to form stable doping structures and bridging structures, inhibit the generation of defect structures, promote the connection of carbon microcrystals in a crosslinking manner, improve the porosity, and avoid the volatilization of the volatile components produced by the cracking of the pitch doping solution from the pores due to the too fast heating, which can cause the crosslinking reaction to fail. In addition, the excess pitch is pre-carbonized to avoid the adhesion of particles in the subsequent sintering stage due to the pitch as an adhesive. Thus, the crosslinking reaction between the carbon microcrystal, dopant, and pitch of the second precursor is fully carried out, the doping elements are uniformly distributed in the internal and closed pore regions of the carbon negative electrode particles, the sodium storage activity of the pores is improved, the polarization is reduced, and thus the capacity, initial efficiency, rate charge, and cycle performance are improved.

[0145] In an embodiment, in step (3), the mass ratio of the second precursor and the pitch doping solution is (75-95):(25-5), for example, it can be 75:25, 80:20, 85:15, 90:10, 95:5, etc.

[0146] In an embodiment, in step (3), the mixing of the second precursor and the pitch doping solution comprises: adding the pitch doping solution to the second precursor under low-speed stirring; wherein the low-speed stirring has a rotation speed of 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.

[0147] In an embodiment, in step (3), the holding process of the doping treatment is carried out under stirring; wherein the stirring has a rotation speed of 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.

[0148] In an embodiment, in step (3), the holding process is carried out in an inert gas atmosphere.

[0149] In an embodiment, in step (3), the inert gas atmosphere in the holding process comprises any one or a combination of at least two of a nitrogen atmosphere, an argon atmosphere, a neon atmosphere, a helium atmosphere, a xenon atmosphere, or a krypton atmosphere.

[0150] In an embodiment, in step (3), the preparation of the pitch doping solution comprises: heating and melting pitch to obtain liquid pitch; adding a dopant to the liquid pitch and stirring until dissolved to obtain the pitch doping solution.

[0151] In an embodiment, the pitch doping solution comprises a dopant and liquid pitch.

[0152] In an embodiment, the mass ratio of the dopant to liquid pitch 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.

[0153] In an embodiment, the dopant comprises any one or a combination of at least two of a nitrogen source, a phosphorus source, or a sulfur source.

[0154] In an embodiment, the nitrogen source comprises any one or a combination of at least two of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, an amino acid, or ammonium bicarbonate.

[0155] In an embodiment, the phosphorus source comprises any one of phosphorus trichloride, phosphorus pentoxide, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, or a phosphonate, or a combination of at least two thereof.

[0156] In an embodiment, the sulfur source comprises any one of sulfur powder, thiourea, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, or cysteine, or a combination of at least two thereof.

[0157] In an embodiment, in step (4), the sintering is performed at a temperature of 1100-1400℃, for example, can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, etc.

[0158] In an embodiment, in step (4), the sintering is performed for a time of 0.25-10 h, for example, 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.

[0159] In an embodiment, in step (4), the sintering is performed under an inert gas atmosphere.

[0160] In an embodiment, in step (4), during the sintering, the inert gas atmosphere comprises any one of a nitrogen atmosphere, an argon atmosphere, a neon atmosphere, a helium atmosphere, a xenon atmosphere, or krypton, or a combination of at least two thereof.

[0161] In an embodiment, in step (4), the sintering is performed in a sintering furnace.

[0162] In an embodiment, in step (4), the sintering furnace comprises any one of a tube furnace, a box furnace, a roller kiln, or a rotary furnace, or a combination of at least two thereof.

[0163] The present application also provides a negative electrode sheet, which comprises the carbon negative electrode material.

[0164] The present application also provides a sodium ion battery, which comprises the negative electrode sheet.

[0165] The present application also provides an electrical equipment, which comprises the sodium ion battery.

[0166] The present application is further described below through specific embodiments. In the embodiments, the experimental materials used are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0167] Embodiment 1 The present embodiment provides a carbon negative electrode material, which is prepared by the following steps: (1) The washed and dried coconut shell is placed in a box furnace and heated to 500°C under a nitrogen atmosphere for 24 h. The obtained material is crushed by a crusher with a mesh size of 5 mm and pulverized to a median particle size of 5 μm to obtain a crushed material. The crushed material and potassium hydroxide are 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 for 1 h. After cooling, the mixture is washed with pure water until the pH value is 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 80°C pure water are added, stirred for 1 h, and washed with pure water until the pH value is 4-8. After solid-liquid separation and drying, a first precursor is obtained; (2) 0.5 parts of potassium permanganate and 9.5 parts of hydrochloric acid (31 wt%) are added to 90 parts of pure water to prepare a 0.5 wt% potassium permanganate hydrochloric acid solution. One time the mass of the first precursor obtained in step (1) is added to 3 times the mass of the 0.5 wt% potassium permanganate hydrochloric acid solution, and heated to 90°C in a water bath under stirring for 6 h. After cooling, a second precursor is obtained. (3) 2 parts of mass of high-temperature pitch is heated to about 250°C to melt, and 1 part of mass of phosphorus pentoxide is added under stirring. After 0.5 h of heat preservation, a liquid pitch doping liquid is obtained. The second precursor and the pitch doping liquid are mixed in a VC mixer at a mass ratio of 90:10. After the addition is completed, the speed is increased to 200 r / min, and the temperature is increased to 250°C under a nitrogen atmosphere. After 5 h of heat preservation, the temperature is further increased to 800°C, and heat preservation is performed for 3 h. After cooling, a third precursor is obtained. (4) The third precursor is placed in a tube furnace and sintered at 1300°C under a nitrogen atmosphere for 3 h. After cooling, 325 mesh screening is performed to obtain the carbon negative electrode material.

[0168] Example 2 The present embodiment provides a carbon negative electrode material prepared by the following steps: (1) The thermosetting phenolic resin is placed in a box furnace and heated to 600°C under a nitrogen atmosphere for 2 h. The obtained material is crushed by a crusher with a mesh size of 3 mm and pulverized to a median particle size of 3 μm to obtain a crushed material. The crushed material and potassium hydroxide are 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 for 24 h. After cooling, the mixture is washed with pure water until the pH value is 8-10. Then, 1 times the mass of the crushed material of hydrochloric acid (31 wt%) and 3 times the mass of the crushed material of 80°C pure water are added, stirred for 1 h, and washed with pure water until the pH value is 4-8. After solid-liquid separation and drying, a first precursor is obtained. (2) According to the mass ratio, 1 part of potassium dichromate, 9 parts of nitric acid (50 wt%) are added to 90 parts of pure water, stirred and dissolved to prepare 1 wt% of potassium dichromate nitric acid solution; 1 times mass of the first precursor obtained in step (1) is added to 20 times mass of 1 wt% of potassium dichromate nitric acid solution, heated to 50℃ in water bath under stirring, and incubated for 24 h, and then cooled to obtain the second precursor; (3) The medium temperature pitch is heated to about 200℃ to melt, and then melamine with the same mass as the medium temperature pitch is added under stirring, and incubated for 0.5 h under stirring to obtain a liquid pitch doping solution; according to the mass ratio of the second precursor and the pitch doping solution being 75:25, the second precursor is put into a VC mixer, and the pitch doping solution is slowly added at a rotation speed of 25 r / min; after the addition is completed, the rotation speed is increased to 500 r / min, and then the temperature is increased to 200℃ under nitrogen atmosphere, and incubated for 5 h, and then further increased to 750℃, and incubated for 5 h, and then cooled to obtain the third precursor.

[0169] (4) The third precursor is placed in a tube furnace and sintered at 1400℃ for 0.5 h under nitrogen atmosphere, and then cooled and sieved through a 325 mesh screen to obtain the carbon negative electrode material.

[0170] Example 3 The present embodiment provides a carbon negative electrode material prepared by the following steps: (1) Thermosetting phenolic resin and potato starch are mixed in a VC mixer according to a mass ratio of 1:1, placed in a box furnace, and then heated to 650℃ under argon atmosphere, and incubated for 3 h; the obtained material is crushed by a crusher with a screen mesh size of 5 mm, and then pulverized to a median particle size of 15 μm to obtain a crushed material; the crushed material and potassium oxide are mixed in a VC mixer according to a mass ratio of 1:1, and then placed in a box furnace, heated to 650℃ under helium atmosphere, and incubated for 2 h, and then cooled and washed with pure water until pH=8~10; 0.7 times mass of hydrochloric acid (31 wt%) and 5 times mass of 80℃ pure water are added, stirred for 1 h, and then washed with pure water until pH=4~8, and then solid-liquid separation, and dried to obtain the first precursor; (2) According to the mass ratio, 0.2 parts of sodium perchlorate, 9.8 parts of dilute sulfuric acid (30 wt%) are added to 90 parts of pure water, stirred and dissolved to prepare 0.2 wt% of sodium perchlorate sulfuric acid solution; 1 times mass of the first precursor obtained in step (1) is added to 10 times mass of 0.2 wt% of sodium perchlorate sulfuric acid solution, heated to 80℃ in water bath under stirring, and incubated for 10 h, and then cooled to obtain the second precursor; (3) high temperature pitch is heated to about 300°C to melt, and ammonium thiosulfate with the same mass as the medium temperature pitch is added under stirring, and the mixture is kept at 300°C for 0.5 h under stirring to obtain a liquid pitch doping solution; the second precursor is put into a VC mixer, and the pitch doping solution is slowly added at a rotation speed of 30 r / min; after the addition is completed, the rotation speed is increased to 100 r / min, the temperature is increased to 300°C under a nitrogen atmosphere, and the mixture is kept at 300°C for 4 h, and then the temperature is further increased to 500°C, and the mixture is kept at 500°C for 0.5 h, and then the mixture is cooled to obtain the third precursor; (4) the third precursor is placed in a tube furnace and sintered at 1200°C for 5 h under a nitrogen atmosphere, and then the third precursor is cooled and sieved through a 325 mesh screen to obtain the carbon negative electrode material.

[0171] Example 4 The present example provides a carbon negative electrode material, which is prepared by the following steps: (1) lignite is placed in a box furnace and heated to 450°C under a krypton atmosphere, and kept at 450°C for 6 h; the obtained material is crushed by a crusher with a mesh size of 4 mm, and then pulverized to a median particle size of 8 μm to obtain a crushed material; the crushed material and zinc chloride are mixed in a VC mixer at a mass ratio of 1:1, and then placed in a box furnace and heated to 650°C under a nitrogen atmosphere, and kept at 650°C for 2 h; the mixture is cooled and washed with pure water until the pH value is 8-10; 0.5 times the mass of the crushed material of hydrochloric acid (31 wt%) and 10 times the mass of the crushed material of 80°C pure water are added, and the mixture is stirred for 1 h; the mixture is washed with pure water until the pH value is 4-8, and then solid-liquid separation is performed, and the mixture is dried to obtain a first precursor; (2) 5 parts of hydrogen peroxide solution (30 wt%) and 5 parts of hydrochloric acid (31 wt%) are added to 90 parts of pure water under stirring to prepare a 5 wt% hydrogen peroxide hydrochloric acid solution; 1 times the mass of the first precursor obtained in step (1) is added to 10 times the mass of the 5 wt% hydrogen peroxide hydrochloric acid solution, and the mixture is heated to 75°C under stirring in a water bath, and kept at 75°C for 8 h; the mixture is cooled to obtain a second precursor.

[0172] (3) high temperature pitch is heated to about 255°C to melt, and sulfur powder with the same mass as the medium temperature pitch is added under stirring, and the mixture is kept at 255°C for 0.5 h under stirring to obtain a liquid pitch doping solution; the second precursor is put into a VC mixer, and the pitch doping solution is slowly added at a rotation speed of 28 r / min; after the addition is completed, the rotation speed is increased to 500 r / min, the temperature is increased to 255°C under a nitrogen atmosphere, and the mixture is kept at 255°C for 5 h, and then the temperature is further increased to 650°C, and the mixture is kept at 650°C for 4 h, and then the mixture is cooled to obtain the third precursor.

[0173] (4) The third precursor is sintered in a tube furnace at 1100°C for 10 h under a nitrogen atmosphere, cooled, and sieved through a 325 mesh screen to obtain the carbon negative electrode material.

[0174] Example 5 This example provides a carbon negative electrode material, which differs from Example 1 in that in step (3), the phosphorus source is diammonium hydrogen phosphate. The rest is the same as Example 1.

[0175] Example 6 This example provides a carbon negative electrode material, which differs from Example 1 in that in step (3), the phosphorus source is triethyl phosphate. The rest is the same as Example 1.

[0176] Example 7 This example provides a carbon negative electrode material, which differs from Example 1 in that in step (3), the high-temperature pitch is 2 parts and the phosphorus pentoxide is 0.2 parts. The rest is the same as Example 1.

[0177] Example 8 This example provides a carbon negative electrode material, which differs from Example 1 in that in step (3), the high-temperature pitch is 2 parts and the phosphorus pentoxide is 2 parts. The rest is the same as Example 1.

[0178] Example 9 This example provides a carbon negative electrode material, which differs from Example 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 h, then further raised to 500°C, held for 0.5 h, and cooled to obtain the third precursor. The rest is the same as Example 1.

[0179] Example 10 This example provides a carbon negative electrode material, which differs from Example 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, held for 5 h, and cooled to obtain the third precursor. The rest is the same as Example 1.

[0180] Example 11 This example provides a carbon negative electrode material, which has a heteroelement content distribution coefficient of 25% and a phosphorus element content of 3.14 wt%; the carbon negative electrode material is prepared by the following steps: (1) The same as step (1) of Example 1.

[0181] (2) The same as step (1) of Example 1.

[0182] (3) 1 part by mass of high temperature pitch is heated to about 250°C to melt, 1 part by mass of phosphorus pentoxide is added under stirring, and the mixture is kept under stirring for 3 h to obtain a liquid pitch doping solution; the second precursor is put into a VC mixer, and the pitch doping solution is slowly added at a rotation speed of 30 r / min; after the addition is completed, the rotation speed is increased to 450 r / min, the temperature is increased to 250°C under a nitrogen atmosphere, and the mixture is kept for 3 h, and then the temperature is further increased to 750°C, and the mixture is kept for 3 h, and then the mixture is cooled to obtain the third precursor.

[0183] (4) The same as in Example 1.

[0184] Example 12 The present example provides a carbon negative electrode material, the content distribution coefficient of the hetero-element of the carbon negative electrode material is 175%, and the content of phosphorus element is 0.41 wt%; the carbon negative electrode material is prepared by the following steps: (1) The same as in step (1) of Example 1; (2) The same as in step (2) of Example 1; (3) 1 part by mass of high temperature pitch is heated to about 250°C to melt, 0.2 parts by mass of phosphorus pentoxide is added under stirring, and the mixture is kept under stirring for 1 h to obtain a liquid pitch doping solution; the second precursor is put into a VC mixer, and the pitch doping solution is slowly added at a rotation speed of 20 r / min; after the addition is completed, the rotation speed is increased to 300 r / min, the temperature is increased to 265°C under a nitrogen atmosphere, and the mixture is kept for 3 h, and then the temperature is further increased to 780°C, and the mixture is kept for 2 h, and then the mixture is cooled to obtain the third precursor; (4) The same as in step (4) of Example 1.

[0185] Example 13 The present example provides a carbon negative electrode material, which is different from Example 1 in that in step (4), the third precursor is placed in a tube furnace and sintered at 1450°C for 3 h under a nitrogen atmosphere, and then the mixture is cooled and sieved through a 325 mesh screen to obtain the carbon negative electrode material.

[0186] Example 14 The present example provides a carbon negative electrode material, which is different from Example 1 in that in step (4), the third precursor is placed in a tube furnace and sintered at 1100°C for 3 h under a nitrogen atmosphere, and then the mixture is cooled and sieved through a 325 mesh screen to obtain the carbon negative electrode material.

[0187] Comparative Example 1 The present example provides a carbon negative electrode material, which is prepared by the following steps: (1) The washed and dried coconut shell is mechanically crushed (100 mesh), VC mixed according to a mass ratio of 100:1 of the coconut shell crushed material and phosphorus pentoxide, profiled, and placed in a box furnace and heated to 500°C under a nitrogen atmosphere for 24 h; the obtained material is crushed by a crusher with a screen mesh size of 5 mm to a median particle size of 5 μm to obtain a crushed material; the crushed material and potassium hydroxide are VC mixed according to a mass ratio of 1:0.5, then placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 1 h, cooled, and washed with pure water until pH=8-10; 0.5 times the mass of the crushed material of hydrochloric acid (31 wt%) and 2 times the mass of the crushed material of 80°C pure water are added, stirred for 1 h, washed with pure water until pH=4-8, and solid-liquid separated to obtain a first precursor; (2) The same as step (2) of Example 1; (3) 7.4 parts by mass of high-temperature pitch is heated to about 250°C to melt, and kept at 250°C for 0.5 h with stirring to obtain a liquid pitch liquid; 100 parts by mass of the second precursor is put into a VC mixer, and the pitch liquid is slowly added at a rotation speed of 25 r / min; after the addition is completed, the rotation speed is increased to 300 r / min, and the temperature is increased to 250°C under a nitrogen atmosphere, and kept for 5 h, and then further increased to 800°C, and kept for 3 h, and cooled to obtain a third precursor; (4) The same as step (4) of Example 1.

[0188] Comparative Example 2 The present comparative example provides a carbon negative electrode material prepared by the following steps: (1) The washed and dried coconut shell is placed in a box furnace and heated to 500°C under a nitrogen atmosphere for 24 h, and the obtained material is crushed by a crusher with a screen mesh size of 5 mm to a median particle size of 5 μm to obtain a crushed material. The crushed material and phosphorus pentoxide are VC mixed according to a mass ratio of 100:2.5, placed in a box furnace and heated to 600°C under a nitrogen atmosphere for 3 h, and cooled to obtain a doped material; then the doped material and potassium hydroxide are VC mixed according to a mass ratio of 1:0.5, placed in a box furnace and heated to 700°C under a nitrogen atmosphere for 1 h, and cooled, and washed with pure water until pH=8-10. 0.5 times the mass of the crushed material of hydrochloric acid and 2 times the mass of the crushed material of 80°C pure water are added, stirred for 1 h, washed with pure water until pH=4-8, and solid-liquid separated to obtain a first precursor; (2) The same as step (2) of Example 1; (3) 7.4 parts by mass of high temperature pitch was heated to about 250°C to melt, and was kept at 250°C for 0.5 h with stirring to obtain a liquid pitch; 100 parts by mass of the second precursor was put into a VC mixer, and the pitch liquid was slowly added thereto at a rotation speed of 25 r / min, and after the addition was completed, the rotation speed was increased to 300 r / min, and the temperature was increased to 250°C under a nitrogen atmosphere, and was kept at 250°C for 5 h, and then was further increased to 800°C, and was kept at 800°C for 3 h, and was cooled to obtain a third precursor; (4) The same as step (4) of Example 1.

[0189] Comparative Example 3 This comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The washed and dried coconut shell was placed in a box furnace, and was heated to 500°C under a nitrogen atmosphere, and was kept at 500°C for 24 h, and the obtained material was crushed by a crusher with a screen mesh size of 5 mm, and was pulverized to a median particle size of 5 μm to obtain a crushed material; the crushed material, hydrochloric acid (31 wt%), hydrofluoric acid (55 wt%) and pure water at 80°C were stirred at a mass ratio of 1:0.5:0.3:3 for 6 h, and were washed with pure water until pH=4-8, and were solid-liquid separated, and were dried to obtain a first precursor; (2) The same as step (2) of Example 1. (3) The same as step (3) of Example 1. (4) The same as step (4) of Example 1.

[0190] Comparative Example 4 This comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The washed and dried coconut shell was placed in a box furnace, and was heated to 500°C under a nitrogen atmosphere, and was kept at 500°C for 24 h, and the obtained material was crushed by a crusher with a screen mesh size of 5 mm, and was pulverized to a median particle size of 5 μm to obtain a crushed material; the crushed material, phosphorus pentoxide and potassium hydroxide were VC mixed at a mass ratio of 100:2.5:50, and were placed in a box furnace, and were heated to 700°C under a nitrogen atmosphere, and were kept at 700°C for 1 h, and were cooled, and were washed with pure water until pH=8-10; 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, and were stirred for 1 h, and were washed with pure water until pH=4-8, and were solid-liquid separated, and were dried to obtain a first precursor; (2) The same as step (2) of Example 1. (3) 7.4 parts by mass of high temperature pitch was heated to about 250°C to melt, and was kept for 0.5 h under stirring to obtain a liquid pitch; 100 parts by mass of the second precursor was put into a VC mixer, and the pitch was slowly added under stirring at a rotation speed of 25 r / min; after the addition was completed, the rotation speed was increased to 300 r / min, and the temperature was increased to 250°C under nitrogen atmosphere, and was kept for 5 h, and then was further increased to 800°C, and was kept for 3 h, and was cooled to obtain a third precursor; (4) The same as step (4) of Example 1.

[0191] Comparative Example 5 The comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) Coconut shell after washing and drying was placed in a box furnace, and was heated to 500°C under nitrogen atmosphere, and was kept for 24 h; the obtained material was crushed by a crusher with a mesh size of 5 mm, and was crushed to a median particle size of 5 μm to obtain a crushed material; the crushed material and potassium hydroxide were mixed in a VC mixer according to a mass ratio of 1:0.5, and were placed in a box furnace, and were heated to 700°C under nitrogen atmosphere, and were kept for 1 h, and were cooled; pure water was used for washing until pH=8-10; 0.5 times the mass of the crushed material of hydrochloric acid (31 wt%) and 2 times the mass of the crushed material of 80°C pure water were added, and were stirred for 1 h; pure water was used for washing until pH=4-8, and was solid-liquid separated, and was dried; the obtained material and phosphorus pentoxide were mixed in a VC mixer according to a mass ratio of 100:2.5, and were placed in a box furnace, and were heated to 800°C under nitrogen atmosphere, and were kept for 3 h, and were cooled to obtain a first precursor; (2) The same as step (2) of Example 1. (3) 7.4 parts by mass of high temperature pitch was heated to about 250°C to melt, and was kept for 0.5 h under stirring to obtain a liquid pitch; 100 parts by mass of the second precursor was put into a VC mixer, and the pitch was slowly added under stirring at a rotation speed of 25 r / min; after the addition was completed, the rotation speed was increased to 300 r / min, and the temperature was increased to 250°C under nitrogen atmosphere, and was kept for 5 h, and then was further increased to 800°C, and was kept for 3 h, and was cooled to obtain a third precursor; (4) The same as step (4) of Example 1.

[0192] Comparative Example 6 The comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The same as step (1) of Example 1. (2) According to the mass ratio, 9.5 parts of industrial hydrochloric acid (mass concentration of 31 wt%) is added to 90 parts of pure water, stirred and dissolved to prepare a dilute hydrochloric acid solution; 1 times mass of the first precursor obtained in step (1) is added to 3 times mass of the dilute hydrochloric acid solution, and heated to 90°C in a water bath under stirring, and kept for 6 h, and then cooled to obtain a second precursor; (3) The same as step (3) of Example 1; (4) The same as step (4) of Example 1.

[0193] Comparative Example 7 The present comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The same as step (1) of Example 1; (2) The same as step (2) of Example 1; (3) According to the mass ratio of the second precursor and phosphorus pentoxide of 90:3.33, the two are put into a VC mixer, the rotating speed is increased to 300 r / min, and then the temperature is increased to 250°C under nitrogen atmosphere, and kept for 5 h, and then further increased to 800°C, and kept for 3 h, and then cooled to obtain a third precursor; (4) The same as step (4) of Example 1.

[0194] Comparative Example 8 The present comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The same as step (1) of Example 1; (2) The same as step (2) of Example 1; (3) The second precursor, phosphorus pentoxide and high-temperature pitch (median particle size of 2.5 μm) are put into a VC mixer according to the mass ratio of 90:3.33:6.67, the rotating speed is increased to 300 r / min, and then mixed for 0.5 h, and then the mixed material is placed in a box furnace, and the temperature is increased to 800°C, and kept for 3 h, and then cooled to obtain a third precursor; (4) The same as step (4) of Example 1.

[0195] Comparative Example 9 The present comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The same as step (1) of Example 1; (2) The same as step (2) of Example 1; (3) 7.4 parts by mass of high temperature pitch was heated to about 250°C to melt, and was kept for 0.5 h with stirring to obtain a liquid pitch solution; 100 parts by mass of the second precursor was put into a VC mixer, and the pitch solution was slowly added at a rotation speed of 25 r / min; after the addition was completed, the rotation speed was increased to 300 r / min, and the temperature was increased to 250°C under a nitrogen atmosphere, and was kept for 5 h, and then was further increased to 800°C, and was kept for 3 h, and was cooled to obtain the third precursor; (4) The same as step (4) of Example 1.

[0196] Comparative Example 10 The present comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The same as step (1) of Example 1; (2) The same as step (2) of Example 1; (3) 2 parts by mass of high temperature pitch was heated to about 250°C to melt, and 1 part by mass of phosphorus pentoxide was added with stirring, and was kept for 0.5 h to obtain a liquid pitch doping solution; according to the mass ratio of the second precursor to the pitch doping solution being 90:10, the second precursor was put into a VC mixer, and the pitch doping solution was slowly added at a rotation speed of 25 r / min; after the addition was completed, the rotation speed was increased to 300 r / min, and the temperature was increased to 250°C under a nitrogen atmosphere, and was kept for 8 h, and was cooled to obtain the third precursor; (4) The same as step (4) of Example 1.

[0197] Comparative Example 11 The present comparative example provides a carbon negative electrode material, which is prepared by the following steps: (1) The same as step (1) of Example 1; (2) The same as step (2) of Example 1; (3) 2 parts by mass of high temperature pitch was heated to about 250°C to melt, and 1 part by mass of phosphorus pentoxide was added with stirring, and was kept for 0.5 h to obtain a liquid pitch doping solution; according to the mass ratio of the second precursor to the pitch doping solution being 90:10, the second precursor was put into a VC mixer, and the pitch doping solution was slowly added at a rotation speed of 25 r / min; after the addition was completed, the rotation speed was increased to 300 r / min, and the temperature was increased to 250°C under a nitrogen atmosphere, and was kept for 8 h, and was cooled to obtain the third precursor; (4) The same as step (4) of Example 1.

[0198] Test Example 1 Test sample: the carbon negative electrode materials provided in Examples 1-14, and the carbon negative electrode materials provided in Comparative Examples 1-11.

[0199] Test method: (1) SEM photos and impurity element content, impurity element content distribution coefficient test: The sample is scanned by German Zeiss GEMINI 460 scanning electron microscope to obtain SEM photos; the scanning electron microscope is combined with X-ray energy spectrum (EDS) to test the content of impurity elements (N, P, S) at 1000 times. The carbon negative electrode material is placed on a certain carrier, and the cross-section sample is obtained by cutting with high-energy argon ion beam, and analyzed by SEM combined with EDS. A cross-sectional area of a random particle is selected, and the impurity element content distribution coefficient (such as shown in Figure 5A and Figure 5B The calculation formula is as follows: Impurity element content distribution coefficient (%)

[0200] Wherein, AB is the longest line segment (A, B is the line segment end point located on the periphery of the cross section) distributed in the cross section of the carbon negative electrode material, S is the integral area of the impurity element mass concentration along AB displacement tested by EDS, unit wt% x μm; a, b are the impurity element mass concentrations of A point and B point respectively, wt%; R is the distance between AB, unit μm; the meaning of impurity element content distribution coefficient: when the curve of impurity element mass concentration (y) along displacement x is completely coincided with line segment FE, the impurity element mass concentration along AB direction is linearly distributed, and it can be considered that the impurity element concentration is close to ideal distribution, at this time S is the area of right triangle CDEF, and the impurity element content distribution coefficient is 100%; when the curve of impurity element mass concentration along displacement x deviates from line segment FE, the impurity element content distribution coefficient deviates from 100%, and the deviation value is positively correlated with the uneven degree of impurity element distribution. Randomly take 3 cross-sectional areas of carbon negative electrode material particles to calculate the impurity element content distribution coefficient, and calculate the average value, which is the impurity element content distribution coefficient of the carbon negative electrode material. The closer the impurity element content distribution coefficient of the carbon negative electrode material to 100%, the higher the uniformity of the impurity element distribution; the farther the impurity element content distribution coefficient deviates from 100%, the more uneven the impurity element content distribution of the carbon negative electrode material.

[0201] (2) Test of median particle size: MASTERSIZER3000 is used for testing. The particle refractive index is 2.42, the absorption rate is 1.0, the dispersing agent is water, and the dispersing agent refractive index is 1.33. The method is: weigh about 0.1 g of sample in a 100 mL beaker, add water to 50 mL, ultrasonic for 1 min, add sample to 8~12% of light shielding degree, and open internal ultrasonic test.

[0202] (3) Test of true density and closed pore pore volume: 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: The volume of the closed hole = (1 / ρ -1 / ρ 参 ) in, ρ The true density of the sample (g / cm³) 3 ), ρ 参 True density (g / cm³) of the reference sample 3 ).

[0203] 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).

[0204] (4) Compacted density of 3T powder (g / cm³) 3 ): 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 ).

[0205] (5) Specific surface area test: 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).

[0206] (6) Carbon interlayer content test: The XRD data were obtained by using a Panalytical X'Pert PRO MPD tester, using Cu target Kα ray (wavelength λ=0.1541 nm) as a light source, in the range of 2 Theta 10°-90°. The carbon interlayer spacing was calculated by the diffraction angle (002) of XRD, by using the Scherrer formula (unit: nm).

[0207] (7) Powder conductivity test: The conductivity data were obtained by using a Mitsubishi Chemical MCP-PD51 tester, by adding the sample and testing under 20 kN.

[0208] The specific test results are shown in Table 1 below: Table 1

[0209] As shown in Table 1, the content of the impurity element in the carbon negative electrode material is 0.4-5 wt%; the distribution coefficient of the impurity element content in the carbon negative electrode material is 25.0-175.0%; thus, it is illustrated that the impurity element can penetrate into the carbon particle inside the carbon negative electrode material, the impurity element is uniformly distributed in the carbon material particle and is fully bonded with the carbon element. The conductivity of the carbon negative electrode material is 26.8-50.3 S / cm, preferably 42.0-50.3 S / cm; thus, it is illustrated that a large amount of impurity elements are distributed in the closed pore area, thereby preferably increasing the closed pore electron cloud density and improving the powder conductivity of the carbon negative electrode material. In addition, the carbon interlayer spacing of the carbon negative electrode material is 0.37-0.39 nm, the closed pore volume is 0.04-0.3 cm 3 / g, the 3T powder compaction density is 1.0-1.1 g / cm 3 , and the true density is 1.56-2.06 g / cm 3 , the specific surface area of the carbon negative electrode material is 1.5-8.0 m 2 / g; thus, it is illustrated that the carbon negative electrode material has the advantages of large interlayer spacing, many closed pores, and dense structure.

[0210] As can be seen from the comparison data of Example 1 and Example 13, Example 14 in Table 1, the 3T compaction density of the carbon negative electrode material of Example 13 and Example 14 is poorer than that of the carbon negative electrode material of Example 1, the sintering temperature of step (4) of Example 13 is higher, and the sintering temperature of step (4) of Example 14 is lower. The sintering temperature has an important influence on the formation of closed pores and the change of carbon layers. When the sintering temperature is too high, the chemical bond between the heteroatom and the carbon atom is broken, the closed pore volume increases significantly, the effective volume ratio of the carbon negative electrode for storing sodium decreases, the carbon layer 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 crosslinked, the content of carbon and hydrogen components is high, the closed pore volume is small, the conductivity of the carbon matrix is low, and the electrochemical polarization increases, so the compaction density performance decreases.

[0211] As can be seen from the comparison data of Example 1 and Comparative Example 1 in Table 1, and Figure 6 and Figure 7 As can be seen from the comparison data of Example 1 and Comparative Example 1 in Table 1, and Figure 9 As can be seen from the comparison data of Example 1 and Comparative Example 1 in Table 1, and

[0212] As can be seen from the comparison data of Example 1 and Comparative Example 2, Comparative Example 4, and Comparative Example 5 in Table 1, and Figure 8The comparison of the comparative examples 2, 4 and 5 can show that the comparative example 2 is doped by mixing the hard carbon pre-carbonized material with the dopant and heating; the comparative example 4 is doped by mixing the hard carbon pre-carbonized material, the pore-forming agent and the dopant and heating; and the comparative example 5 is doped by first modifying the hard carbon pre-carbonized material and then mixing the modified hard carbon pre-carbonized material with the dopant and heating. The comparative examples 2, 4 and 5 are respectively modified by the hard carbon pre-carbonized material and the dopant, the hard carbon pre-carbonized material, the pore-forming agent and the dopant, and the hard carbon pre-carbonized material and the dopant. The doping elements of these methods are mainly concentrated on the surface of the carbon negative electrode material particles, the distribution coefficient of the heteroatoms and the powder conductivity are low, the doping elements cannot be fully bonded with the carbon components of the hard carbon, and the heteroatoms cannot improve the cross-linking degree of the microcrystals, catalyze the "open pores" to "closed pores", and improve the conductivity of the pore area. The carbon negative electrode preparation method of the example 1 first pre-carbonizes, pores, and modifies the hard carbon, and then embeds the pitch doping liquid into the second precursor particles under the heating of VC. The hard carbon microcrystal, the soft carbon source and the dopant are cross-linked under high temperature conditions to achieve doping, which can improve the uniformity of the doping elements in the carbon negative electrode particles, improve the cross-linking degree of the carbon microcrystals, increase the number of closed pores of the carbon negative electrode material, and improve the sodium storage activity of the closed pore area.

[0213] The comparison data of the example 1 and the comparative examples 3, 6 in Table 1 can show that the carbon negative electrode material of the comparative example 3 is not subjected to pore-forming after pre-carbonization in step (1), and the carbon negative electrode material of the comparative example 6 is not subjected to modification reaction in step (2). The role of the pore-forming is to construct a connected pore structure in the hard carbon particles, to provide a channel for the dopant and the soft carbon source to enter the hard carbon particles, and the role of the modification reaction is to improve the porosity of the carbon matrix and increase the cross-linking functional groups on the basis of the pore-forming, to provide a reaction site for the soft and hard carbon composite and the heteroatom doping. The content of the heteroatoms, the distribution coefficient of the heteroatoms and the conductivity of the carbon negative electrode material of the comparative example 3 are low, and the content of the heteroatoms, the distribution coefficient of the heteroatoms and the conductivity of the carbon negative electrode material of the comparative example 6 are better than those of the comparative example 3, but due to the lack of modification, the activity of the soft and hard carbon composite and the heteroatom doping reaction is not strong, the closed pore volume and the conductivity are not much different from those of the comparative example 3, and both of them are worse than those of the example 1. This shows that the combination of the pore-forming and the modification has a significant technical advantage in improving the content and the distribution uniformity coefficient of the heteroatoms, the closed pore volume and the conductivity.

[0214] The comparison data of the example 1 and the comparative examples 7, 8 and 9 in Table 1 can show that Figure 8The comparison of the examples and the comparative examples can show that, in step (3) of the comparative example 7, the dopant and the pitch are not heated to prepare a pitch doping solution, and the doping reaction is directly performed by using the dopant and the second precursor; in step (3) of the comparative example 8, the second precursor and the pitch doping solution are directly mixed, and then heated for doping, without VC heating; and in the comparative example 9, the pitch melting solution is used to replace the pitch doping solution to perform the doping reaction with the second precursor based on the example 1. In the comparative examples 7 and 8, there is no cross-linking reaction among the carbon microcrystals of the second precursor, the dopant and the pitch, and the soft and hard carbon complex and the doping modification cannot effectively occur in the carbon matrix, the doping elements cannot be uniformly distributed in the closed pore vicinity, the sodium storage activity of the closed pore is low, and the polarization is large. The closed pore volume, the carbon layer spacing and the powder conductivity of the comparative example 9 are all lower than those of the example 1, because the dopant in the pitch doping solution in the present application plays a role of catalyzing the cross-linking of the hard carbon carbon microcrystals and the soft carbon source, promoting the conversion of the “open pore” into the “closed pore”, and improving the conductivity of the closed pore region. Therefore, the combination of the pitch doping solution (soft carbon source, dopant) and the VC heating in step (3) has a significant technical advantage.

[0215] The comparison data of the example 1 and the comparative examples 10-11 in Table 1 can show that, only the low-temperature doping reaction or only the high-temperature doping reaction will lead to uneven doping reaction, and the combination of the low-temperature doping reaction and the high-temperature doping reaction is necessary to ensure the uniform doping reaction. Therefore, in the doping process of the hetero elements, the specific heat preservation procedure can further improve the uniform distribution coefficient of the hetero elements; first, long-time heat preservation (3-10 h) at a low temperature (200-300℃) can make the pitch doping solution maintain good fluidity and repeatedly adsorb into the connected pore structure of the second precursor and the carbon matrix; and then, heat preservation for 0.5-5 h at a high temperature (500-800℃) can make the carbon microcrystals of the first precursor, the soft carbon source and the dopant have a pre-cross-linking reaction and a pre-doping reaction at the temperature. The pre-cross-linking reaction and the pre-doping reaction at the temperature have a moderate speed, which can ensure the sufficient bonding, solidification, stable doping structure and bridging structure among the “carbon microcrystal edge, soft carbon source and dopant”, inhibit the generation of defects, promote the connection of the carbon microcrystals in the form of cross-linking, improve the porosity, and avoid the volatilized components from the pores due to the too fast heating, which can cause the cross-linking reaction to fail. In addition, the excess pitch is pre-carbonized, which can avoid the adhesion of the particles in the subsequent sintering stage due to the pitch as an adhesive. Therefore, the cross-linking reaction among the carbon microcrystals of the second precursor, the dopant and the pitch can be fully performed, the doping elements can be uniformly distributed in the carbon negative electrode particles and the closed pore region, the sodium storage activity of the pores can be improved, and the polarization can be reduced.

[0216] Test Example 2 Test sample: carbon negative electrode material provided by Examples 1~14, carbon negative electrode material provided by Comparative Examples 1~11.

[0217] Test method: (1) Test of specific capacity and first efficiency: The carbon negative electrode material, conductive agent and binder obtained from each example and comparative example were mixed in a mass percentage of 91:3:6, the mixture was adjusted to a solid content of 50% with deionized water, and was coated on a copper foil current collector on one side, dried at 130°C for 2 h, rolled, and the surface density was 5.5±0.5 mg / cm 2 , and the electrode sheet was prepared by cutting into a 14 mm diameter disc; a glass fiber GD-120 was used as a separator, a 16 mm diameter sodium sheet was used as a counter electrode, 1M NaPF6 in EC:DMC:EMC=1:1:1 (volume ratio) was used as an electrolyte, a CR2032 battery shell was used, and a button cell was assembled. The button cell was tested on a blue cell test system at room temperature (about 25°C), the nominal specific capacity was set to 300 mAh / g, first 0.1 C constant current discharge to 1 mV, then 50 μA constant current discharge to 1 mV, then 10 μA constant current discharge to 1 mV, and the discharge cutoff; after standing, then 0.1 C charging, cutoff voltage 2 V. The specific capacity (mAh / g) is the first charge capacity divided by the weight of the carbon negative electrode material contained in the negative electrode sheet, and the first efficiency is the ratio of the first charge capacity to the first discharge capacity.

[0218] (2) Test of rate charge performance and room temperature cycle performance: A BETTERAY layered oxide BNH-O3A was used as a positive electrode, and the mixture was mixed according to a mass percentage of positive electrode material: conductive agent: binder mass ratio of 96%:2%:2%, and the mixture was adjusted to a solid content of 50% with N -methylpyrrolidone, coated on an aluminum foil current collector on both sides, dried, rolled, and the surface density was controlled to be about 300 g / m 2 , to obtain a positive electrode sheet.

[0219] The carbon negative electrode material, conductive agent and binder obtained from each example and comparative example were mixed in a mass percentage of 91:3:6, the mixture was adjusted to a solid content of 50% with deionized water, and was coated on a copper foil current collector on both sides, dried, rolled, and the surface density was about 150 g / m 2 , to obtain a negative electrode sheet; The positive and negative electrodes were assembled into a 554065 type soft package battery according to an NP excess ratio of 20%, a PP separator, 1M NaPF6 in EC:DMC:EMC=1:1:1 (volume ratio) as an electrolyte, and the test voltage range was 2~4V.

[0220] (2-1) 6C / 1C rate charge retention rate (%) test: at room temperature, constant current charge and discharge test was carried out at different rates of 1C / 1C and 6C / 6C in turn, and the 6C charge capacity was divided by the 1C charge capacity to obtain the 6C / 1C rate charge retention rate; (2-2) 1C / 1C@500 cycle retention rate (%) test: at room temperature, 1C / 1C constant current charge and discharge cycle test was carried out, and the discharge capacity at the 500th cycle was divided by the discharge capacity at the first cycle to obtain the 1C / 1C cycle 500 cycle retention rate.

[0221] The specific test results are shown in Table 2 below: Table 2

[0222] As shown in Table 2 and Figure 10 , the specific capacity of the sodium ion battery containing the carbon negative electrode material of the present application is 275 mAh / g or more, the initial efficiency is 85% or more, the 6C / 1C charge capacity retention rate is 54% or more, and the 1C / 1C@500 cycle retention rate at room temperature is 83% or more; among them, the specific capacity of the sodium ion battery containing the carbon negative electrode material provided in Examples 1-6 as a preferred scheme is 325-385 mAh / g, the initial efficiency is 85.6-92.5%, the 6C / 1C charge capacity retention rate is as high as 79.3-84.1%, and the 1C / 1C@500 cycle retention rate at room temperature is as high as 91.7-96.4%. Thus, it is shown that the sodium ion battery containing the carbon negative electrode material of the present application has the advantages of high capacity, high rate charge and high cycle performance.

[0223] From the comparison of Examples 1 and Examples 13 and 14, it can be seen that the capacity, initial efficiency, 6C / 1C charge capacity retention rate and 1C / 1C@500 cycle retention rate of the carbon negative electrode material provided in Examples 13-14 are all worse than those of the carbon negative electrode material obtained in Example 1. When the sintering temperature is too high, the sodium storage capacity does not increase but decreases, and the electrochemical polarization increases, so the capacity, rate charge, cycle and compaction density performance all decrease. When the sintering temperature is too low, the electrochemical polarization increases, so the capacity, rate charge, cycle and compaction density performance all decrease.

[0224] It can be seen from the comparison of Example 1 and Comparative Example 1 that the capacity, initial efficiency, 6C / 1C charge capacity retention rate and 1C / 1C@500 cycle retention rate of the carbon negative electrode material obtained by Comparative Example 1 are all poorer than those of the carbon negative electrode material obtained by Example 1. Comparative Example 1 directly compounding a hard carbon carbon source and a dopant, then pre-carbonizing to prepare a carbon negative electrode material, the dopant cannot be doped into the interior of the hard carbon particles during the pre-carbonization process, and the dopant reacts with the tar components cracked from the hard carbon carbon source, inhibiting the removal of the tar components, the tar components occupying sodium storage sites, inhibiting the porosity of the hard carbon and reducing the carbon layer spacing, etc., the heteroatom distribution coefficient and the closed pore volume are both small, thereby leading to the decrease of the specific capacity, rate charge and cycle performance of the obtained carbon negative electrode material. Thus, it is shown that directly using a dopant to compound with a hard carbon carbon source and then high-temperature treatment, pre-carbonization and doping are simultaneously performed is not feasible.

[0225] It can be seen from the comparison of Example 1 and Comparative Example 2, Comparative Example 4 and Comparative Example 5 that the capacity, initial efficiency, 6C / 1C charge capacity retention rate and 1C / 1C@500 cycle retention rate of the carbon negative electrode materials obtained by Comparative Example 2, Comparative Example 4 and Comparative Example 5 are all poorer than those of the carbon negative electrode material obtained by Example 1. The doping elements in these methods are mainly concentrated on the surface of the carbon negative electrode material particles, the heteroatom distribution coefficient and the powder conductivity are low, the doping elements cannot be fully bonded with the hard carbon components, and the heteroelements cannot improve the microcrystal crosslinking degree, catalyze the “open pore” to “closed pore” and improve the conductivity of the pore area, so the effect of the doping on improving the capacity, rate and cycle performance is poor. However, the present application can improve the uniformity of the distribution of the doping elements in the carbon negative electrode particles, improve the carbon microcrystal crosslinking degree, increase the number of closed pores and the sodium storage activity of the closed pore area of the carbon negative electrode material, thereby improving the capacity, initial efficiency, rate charge and cycle performance of the hard carbon.

[0226] It can be seen from the comparison of Example 1 and Comparative Example 3 and Comparative Example 6 that the capacity, initial efficiency, 6C / 1C charge capacity retention rate and 1C / 1C@500 cycle retention rate of the carbon negative electrode materials obtained by Comparative Example 3 and Comparative Example 6 are all poorer than those of the carbon negative electrode material obtained by Example 1. Thus, it is shown that combining pore making and modification can improve the content and distribution uniformity coefficient of the heteroelements, the closed pore volume and the conductivity, improve the capacity, initial efficiency, rate charge and cycle performance of the hard carbon, and the present application has a significant technical advantage by combining pore making and modification.

[0227] As can be seen from the comparison of Example 1 and Comparative Example 7, Comparative Example 8 and Comparative Example 9, the capacity, initial efficiency, 6C / 1C charge capacity retention and 1C / 1C@500 cycle retention of the carbon negative electrode material of Comparative Example 7, Comparative Example 8 and Comparative Example 9 are all poorer than those of the carbon negative electrode material obtained in Example 1. In Comparative Example 7 and Comparative Example 8, the doping elements cannot be uniformly distributed in the vicinity of the closed pores, resulting in low sodium storage activity of the closed pores, large polarization, and the capacity, initial efficiency, rate charge and cycle performance of the obtained carbon negative electrode material are all poorer than those of Example 1. In Comparative Example 9, on the basis of Example 1, the pitch melt liquid is used instead of the pitch doping liquid to react with the second precursor, and the electrochemical performance is poorer than that of Example 1, because in the present application, the dopant in the pitch doping liquid plays a role of catalyzing the crosslinking of hard carbon carbon microcrystals and soft carbon source, promoting the conversion of "open pores" to "closed pores", and improving the electrical conductivity and sodium storage activity of the closed pore region. The reaction of the second precursor and the pitch melt liquid cannot achieve the same effect as the reaction of the pitch doping liquid. Therefore, it is shown that the combination of the pitch doping liquid (soft carbon source, dopant) and VC heating in step (3) has a significant technical advantage.

[0228] It can be seen from the comparison of Example 1 and Comparative Example 10, Comparative Example 11 that the capacity, initial efficiency, 6C / 1C charge capacity retention and 1C / 1C@500 cycle retention of the carbon negative electrode material of Comparative Example 10 and Comparative Example 11 are all poorer than those of the carbon negative electrode material obtained in Example 1. In the VC heating and doping stage of step (3), Comparative Example 10 only performs the low-temperature doping (250 DEG C for 8 h) step without performing the high-temperature (500-800 DEG C) doping; in the VC heating and doping stage of step (3), Comparative Example 11 only performs the high-temperature doping (800 DEG C for 8 h) step without performing the low-temperature (200-300 DEG C) doping step; thus, it is illustrated that the uniform distribution coefficient of the doping of the hetero-element is further improved by the specific holding procedure; wherein, first, long-time holding (3-10 h) at low temperature (200-300 DEG C) enables the pitch doping liquid to maintain good fluidity and repeatedly adsorb into the connected pore structure of the second precursor and the carbon matrix; and then, holding for 0.5-5 h at high temperature (500-800 DEG C) to make the carbon microcrystal edge of the first precursor, the soft carbon source and the dopant undergo pre-crosslinking reaction and pre-doping reaction at the temperature, the pre-crosslinking reaction and pre-doping reaction speed at the temperature is moderate, which ensures that the "carbon microcrystal edge, soft carbon source and dopant" are fully bonded and solidified to form stable doping structure and bridging structure, inhibits the generation of defects, promotes the connection of the carbon microcrystals in the form of crosslinking and improves the porosity. Thus, the crosslinking reaction among the carbon microcrystal, the dopant and the pitch of the second precursor is fully performed, the doping elements are evenly distributed in the interior of the carbon negative electrode particle and the closed pore area, the sodium storage activity of the pores is improved, the polarization is reduced, the capacity, rate and cycle performance are improved. Therefore, the specific holding procedure for the doping reaction has significant technical advantages.

[0229] The above detailed the embodiments of the present application, and the principles and implementation manners of the present application are described by applying specific examples; the above embodiment descriptions are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the present application; in conclusion, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A carbon anode material, characterized in that, The carbon anode material includes hard carbon and heterogeneous elements dispersed within the hard carbon; and the heterogeneous element content distribution coefficient of the carbon anode material is 25~175%.

2. The carbon anode material according to claim 1, characterized in that, The carbon anode material must satisfy at least one of the following conditions: (a) The impurity element content distribution coefficient of the carbon anode material is 50~150%; (b) The heteroelement includes any one or a combination of at least two of nitrogen, phosphorus, or sulfur; (c) The content of impurity elements in the carbon anode material is 0.4~5 wt%; (d) The carbon interlayer spacing of the carbon anode material is 0.37~0.39 nm; (e) The carbon anode material includes soft carbon dispersed inside the hard carbon, and the soft carbon fills the pores of the hard carbon to form closed pores; (f) The closed pore volume of the carbon anode material is 0.04~0.3 cm³. 3 / g; (g) The compacted density of the 3T powder of the carbon anode material is 1.0~1.1 g / cm³. 3 ; (h) The conductivity of the carbon anode material is 26~52 S / cm; (i) The median particle size of the carbon anode material is 4~15 μm; (j) The true density of the carbon anode material is 1.56~2.06 g / cm³. 3 ; (k) The specific surface area of ​​the carbon anode material is 1.5~8.0 m². 2 / g.

3. A method for preparing a carbon anode material according to claim 1 or 2, characterized in that, The preparation method includes: (1) The carbon source is pre-carbonized, crushed and pore-formed to obtain the first precursor; (2) The first precursor is modified to obtain the second precursor; (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. (4) The third precursor is sintered to obtain the carbon anode material.

4. The method for preparing the carbon anode material according to claim 3, characterized in that, 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. And / or, in step (1), the pre-carbonization temperature is 450~650℃, and the pre-carbonization holding time is 0.5~24h; And / or, in step (1), the pulverization includes: pulverizing the pre-carbonized material to a median particle size of 3~15 μm to obtain the pulverized pre-carbonized material; And / or, 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; And / or, the mass ratio of the pulverized pre-carbonized material to the solid pore-forming agent is 1:(0.5~3.0); And / or, 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; And / or, the temperature of the pore-forming treatment is 400~700℃, and the time of the pore-forming treatment is 0.25~24 h; And / or, the pore-forming process further includes a purification process, the purification process comprising: 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; And / or, the acid includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid, phosphoric acid, or sulfuric acid.

5. The method for preparing the carbon anode material according to claim 4, characterized in that, 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; And / or, the mass ratio of the first precursor to the oxidizing acid solution is 1:(3~20); And / or, the oxidizing acid solution comprises an oxidizing solute and an acid; And / or, 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; And / or, the acid includes any one or a combination of at least two of hydrochloric acid, hydrofluoric acid, phosphoric acid, sulfuric acid or nitric acid; And / or, 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 being water; And / or, the temperature of the modification reaction is 50~100℃, and the time of the modification reaction is 0.5~24 h.

6. The method for preparing the carbon anode material according to claim 4, characterized in that, 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; And / or, the mass ratio of the second precursor to the asphalt dopant is (75~95):(25~5); And / or, 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 low-speed stirring speed is 20~30 r / min; And / or, the heat preservation process is carried out under stirring; wherein the stirring speed is 100~500 r / min; And / or, the preparation steps of the asphalt doping solution include: heating and melting asphalt to obtain liquid asphalt; adding a dopant to the liquid asphalt and stirring until dissolved to obtain the asphalt doping solution; And / or, the asphalt doping solution comprises a dopant and liquid asphalt in a mass ratio of (0.1~1):1; And / or, the dopant includes any one or a combination of at least two of nitrogen, phosphorus or sulfur sources.

7. The method for preparing the carbon anode material according to claim 4, characterized in that, In step (4), the sintering temperature is 1100~1400℃ and the sintering time is 0.25~10 h.

8. A negative electrode sheet, characterized in that, The negative electrode sheet comprises the carbon negative electrode material as described in claim 1 or 2.

9. A sodium-ion battery, characterized in that, The sodium-ion battery includes the negative electrode as described in claim 8.

10. An electrical-related device, characterized in that, The electrical equipment includes the sodium-ion battery as described in claim 9.

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