Carbon negative electrode material, preparation method and application thereof

Abstract

The application provides a carbon negative electrode material and a preparation method and application thereof. The carbon negative electrode material comprises a carbon base body, and a carbon layer of the carbon base body contains a doping element. The uniformity of the distribution of the doping element is greater than or equal to 35%. The carbon negative electrode material provided by the application improves the uniformity of the distribution of the doping element in the carbon layer of the carbon material, solves the problem of over-saturation of the surface layer doping element and lack of the inner layer doping element of the conventional doped carbon material, realizes sufficient and uniform combination of carbon atoms and the doping element, maximally plays the role of the doping element in improving the capacity performance of the carbon negative electrode material, and reduces the charge and discharge expansion rate of the carbon negative electrode material and improves the cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material preparation, in particular to a carbon negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] In recent years, with the rise of 3C electronics and electric vehicle industries, the installed capacity of lithium / sodium ion battery market presents explosive growth. The carbon negative electrode materials for lithium / sodium ion batteries mainly include graphite and amorphous carbon. Among them, graphite has the advantages of high initial efficiency, high compaction density and low cost, and is the mainstream carbon negative electrode material in the market. However, with the rising prices of raw materials, the preparation cost of graphite is continuously increasing, and it does not have the performances of fast charging, low temperature resistance and low expansion. Although amorphous carbon has the advantages of fast charging, low temperature resistance and low expansion, it has poor compaction density and initial efficiency, and its capacity is difficult to improve, which limits its commercial application process. Therefore, there is an urgent need to develop carbon negative electrode materials with high energy density.

[0003] In related technologies, a carbon source and a dopant are directly mixed at high temperature to prepare a doped carbon material. However, the conventional doped carbon material prepared by the above method has an oversaturation of surface layer doping elements and a lack of doping elements in the inner layer, which will cause the collapse of the carbon skeleton of the carbon negative electrode material in the long cycle process, and the cycle retention rate will decrease. On the other hand, it will increase the platform voltage of the carbon negative electrode material, resulting in a decrease in the proportion of available capacity (0-0.8V) and an increase in the proportion of harmful capacity (above 0.8V). SUMMARY

[0004] To solve the technical problems in the related technologies described above, the present application provides a carbon negative electrode material and a preparation method and application thereof, which aims to improve the uniformity of the distribution of doping elements between the carbon layers of the carbon material, solve the problem of oversaturation of surface layer doping elements and lack of doping elements in the inner layer of the conventional doped carbon material, realize the full and uniform combination of carbon atoms and doping elements, maximize the role of doping elements in improving the capacity performance of the carbon negative electrode material, and reduce the charge and discharge expansion rate of the carbon negative electrode material and improve the cycle performance. The specific content is as follows:

[0005] In a first aspect, the present application provides a carbon negative electrode material, which comprises a carbon matrix, and the carbon layers of the carbon matrix contain doping elements, and the uniformity of the distribution of the doping elements is greater than or equal to 35%.

[0006] Optionally, the carbon negative electrode material comprises at least one of the following features (1) to (8):

[0007] (1) The doping elements comprise at least one of boron, nitrogen, phosphorus and sulfur;

[0008] (2) The median particle size of the carbon negative electrode material is 1-40 μm;

[0009] (3) the specific surface area of the carbon negative electrode material is 0.5 m 2 / g-300 m 2 / g;

[0010] (4) the content of the doping element in the carbon negative electrode material is 0.05wt%-12wt%;

[0011] (5) the carbon layer spacing of the carbon matrix is 0.35nm-0.44nm;

[0012] (6) the uniformity of the distribution of the doping element in the carbon negative electrode material is greater than or equal to 50%;

[0013] (7) the carbon negative electrode material further comprises a carbon coating layer formed on the surface of the carbon matrix;

[0014] (8) the carbon negative electrode material further comprises a carbon coating layer formed on the surface of the carbon matrix, and the thickness of the carbon coating layer is 0μm-5μm.

[0015] In a second aspect, the present application provides a preparation method of a carbon negative electrode material, comprising the following steps:

[0016] pre-carbonizing a raw material containing a carbon source under the action of a mixed gas to obtain a first precursor with porosity and oxygen-rich carbon layer spacing; wherein the mixed gas comprises a protective gas and an oxidizing gas;

[0017] subjecting the first precursor to a modification and modification reaction with a modification and modification agent in a protective gas atmosphere, and subjecting the product obtained after the modification and modification reaction to a first purification treatment to obtain a second precursor containing intercalation in the carbon layer spacing; and

[0018] subjecting the second precursor containing intercalation in the carbon layer spacing to a doping reaction with a doping agent in a protective gas atmosphere, and subjecting the product obtained after the doping reaction to a second purification treatment to obtain the carbon negative electrode material.

[0019] Optionally, the method comprises at least one of the following features (1)-(10):

[0020] (1) the oxidizing gas comprises at least one of air, oxygen, ozone, ammonia, chlorine, water vapor, carbon dioxide and carbon monoxide;

[0021] (2) the protective gas comprises at least one of nitrogen, argon, neon, helium, xenon and krypton;

[0022] (3) the content of the oxidizing gas in the mixed gas is 0.1wt%-2wt%;

[0023] (4) the carbon source comprises at least one of almond shell, coconut shell, walnut shell, jujube pit shell, peach pit shell, rice husk, peanut shell, melon seed shell, pistachio shell, hazelnut shell, straw, wood chips, vinasse, starch, sucrose, glucose, phenolic resin, epoxy resin, melamine resin, furfural resin, urea-formaldehyde resin, pitch, petroleum coke, needle coke, mesocarbon microbeads and anthracite;

[0024] (5) the carbon source-containing raw material further comprises a curing agent;

[0025] (6) the carbon source-containing raw material further comprises a curing agent, and the mass ratio of the carbon source to the curing agent is 5-95:95-5;

[0026] (7) the carbon source-containing raw material further comprises a curing agent, and the curing agent comprises at least one of melamine, hexamethylenetetramine, p-benzaldehyde, ammonium chloride, ammonium bromide, ammonium fluoride, ammonium iodide, ammonium sulfide, ammonium phosphate, dihydrogen ammonium phosphate, ammonium dihydrogen phosphate, ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium oxalate and ammonium acetate;

[0027] (8) the pre-carbonization reaction temperature is 300-800℃;

[0028] (9) the pre-carbonization reaction time is 0.1h-24h;

[0029] (10) the mass ratio of the first precursor to the modification modifier is 70-99:1-30.

[0030] Optionally, the method comprises at least one of the following features (1)-(4):

[0031] (1) the modification modifier is halogen and a compound thereof;

[0032] (2) the modification modifier is halogen and a compound thereof, and the halogen and the compound thereof comprise at least one of aluminum chloride, iron chloride, iron bromide, zinc chloride, zinc bromide, iodine, chlorine water, bromine water, iodine water and liquid bromine;

[0033] (3) the modification reaction temperature is 200-800℃;

[0034] (4) the modification reaction time is 0.1h-24h.

[0035] Optionally, the method comprises at least one of the following features (1)-(6):

[0036] (1) the modification modifier comprises a reaction additive and an alkali metal salt and / or an alkali metal oxide;

[0037] (2) the modification modifier comprises a reaction additive and an alkali metal salt and / or an alkali metal oxide, and the mass ratio of the reaction additive to the alkali metal salt and / or the alkali metal oxide is 1:0.5-5;

[0038] (3) the modification modifier comprises a reaction additive and an alkali metal salt and / or an alkali metal oxide, and the alkali metal salt and / or the alkali metal oxide comprises at least one of lithium oxide, lithium carbonate, lithium acetate, lithium oxalate, sodium oxide, sodium acetate, sodium oxalate, sodium peroxide, sodium carbonate, sodium bicarbonate, magnesium oxide, magnesium carbonate, potassium oxide, potassium carbonate and potassium bicarbonate;

[0039] (4) the modification modifier comprises a reaction additive and an alkali metal salt and / or an alkali metal oxide, and the reaction additive comprises at least one of glucose, fructose, sucrose, polystyrene, polyvinyl chloride, polyvinyl alcohol, phenolic resin, melamine resin, furfural resin, urea-formaldehyde resin and pitch;

[0040] (5) the reaction temperature of the modification modification reaction is 200-800℃;

[0041] (6) the reaction time of the modification modification reaction is 0.1-24h.

[0042] Optionally, the method comprises at least one of the following features (1)-(10):

[0043] (1) the mass ratio of the second precursor to the dopant is 70-99:1-30;

[0044] (2) the dopant comprises at least one of a boron source, a nitrogen source, a phosphorus source and a sulfur source;

[0045] (3) the dopant comprises at least one of a boron source, a nitrogen source, a phosphorus source and a sulfur source, and the boron source comprises at least one of boric acid, borax, boron trioxide, sodium borohydride, sodium borate, calcium borate, zinc borate, magnesium borate, iron borate, titanium boride and sodium tetraphenylborate;

[0046] (4) the dopant comprises at least one of a boron source, a nitrogen source, a phosphorus source and a sulfur source, and the phosphorus source comprises at least one of phosphorus trichloride, diphosphorus pentoxide, ammonium phosphate, dihydrogen ammonium phosphate, monohydrogen ammonium phosphate, phosphoric acid ester, red phosphorus and black phosphorus;

[0047] (5) the dopant comprises at least one of a boron source, a nitrogen source, a phosphorus source and a sulfur source, and the nitrogen source comprises at least one of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acid and ammonium bicarbonate;

[0048] (6) the dopant comprises at least one of a boron source, a nitrogen source, a phosphorus source and a sulfur source, and the sulfur source comprises at least one of sulfur powder, thiourea, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate and cysteine;

[0049] (7) the reaction temperature of the doping reaction is 800-1300℃;

[0050] (8) the reaction time of the doping reaction is 0.1-24h;

[0051] (9) the purification treatment is performed in an acidic reagent;

[0052] (10) the purification treatment is performed in an acidic reagent, and the acidic reagent comprises at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, acetic acid, oxalic acid, benzoic acid, hydrogen sulfide acid, hydrogen bromic acid and hydrogen iodic acid.

[0053] Optionally, the method further comprises a step of carbon coating on the surface of the carbon negative electrode material or carbon coating after secondary granulation of the carbon negative electrode material.

[0054] Optionally, the method comprises at least one of the following features (1)-(4):

[0055] (1) the carbon coating method comprises at least one of solid-phase coating, liquid-phase coating, VC heating coating and gas-phase coating;

[0056] (2) the carbon coating method comprises at least one of solid-phase coating, liquid-phase coating, VC heating coating and gas-phase coating, and the coating carbon source of the solid-phase coating, liquid-phase coating and VC heating coating comprises at least one of pitch, sucrose, glucose, phenol formaldehyde resin, epoxy resin, melamine resin, furfural resin and urea formaldehyde resin;

[0057] (3) the carbon coating method comprises at least one of solid-phase coating, liquid-phase coating, VC heating coating and gas-phase coating, and the coating carbon source of the gas-phase coating comprises at least one of ethanol, methane, ethane, propane, acetone, ethylene, acetylene, benzene, toluene and xylene;

[0058] (4) the secondary granulation method comprises spray drying granulation or VC heating granulation.

[0059] In a third aspect, the present application provides an application of the carbon negative electrode material. The carbon negative electrode material provided in the first aspect or prepared by the preparation method provided in the second aspect is applied to a battery.

[0060] Compared with the related art, the carbon negative electrode material, the preparation method and the application thereof provided in the present application have at least the following advantages:

[0061] 1. The carbon negative electrode material provided by the application, the carbon atoms between the carbon layers of the carbon matrix are fully and uniformly combined with the doping elements, the uniformity of the distribution of the doping elements is greater than or equal to 35%, which is higher than the uniformity of the distribution of the doping elements of the existing doped carbon materials, can improve the available capacity (below 0.8V), maximize the role of the doping elements in improving the capacity performance of the carbon material, reduce the charge and discharge expansion rate of the carbon material, and improve the cycle performance.

[0062] 2. In the preparation method of the carbon negative electrode material provided by the application, the carbon source or the mixture containing the carbon source is subjected to pre-carbonization treatment under the action of the mixed gas containing a trace amount of oxidizing gas, to obtain a porous first precursor with oxygen enrichment between the carbon layers. The porous structure of the first precursor is beneficial to the diffusion of the modification modifier in the interior of the first precursor particles; the oxygen enrichment between the carbon layers provides a large number of reaction sites for the modification reaction, reduces the energy barrier of the modification reaction, and is beneficial to the full implementation of the modification reaction; and the modification modifier is used to modify the first precursor, so that the intercalation material is embedded between the carbon layers, and the intercalation material entering the carbon layers is easily replaced by the doping elements and removed in the subsequent doping reaction, so that the doping elements are fully doped between the carbon layers, the uniformity of the distribution of the doping elements between the carbon layers of the carbon material is improved, and the problems of over-saturation of the doping elements on the surface and lack of the doping elements in the inner layer of the conventional doped carbon material (the carbon material not modified and mixed with the doping agent, and the doped carbon prepared at a high temperature) are solved. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0064] Figure 1 A flowchart of the preparation method of the carbon negative electrode material provided by the embodiments of the present application is shown;

[0065] Figure 2 A flowchart of another preparation method of the carbon negative electrode material provided by the embodiments of the present application is shown;

[0066] Figure 3 A structural schematic diagram of the carbon negative electrode material provided by the embodiments of the present application is shown;

[0067] Figure 4 An SEM diagram of the carbon negative electrode material provided by the embodiments of the present application is shown;

[0068] Figure 5 A cross-sectional schematic diagram of the carbon negative electrode material provided by the embodiments of the present application is shown;

[0069] Figure 6 A schematic diagram of the doping element distribution of the carbon negative electrode material provided in an embodiment of the present application is shown;

[0070] Figure 7 The first charge and discharge curve of the carbon negative electrode material provided in the embodiment of the present application is shown. DETAILED DESCRIPTION

[0071] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0072] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the prior art. The reagents and other instruments used, if the manufacturers are not specified, are all commercially available conventional reagents.

[0073] In order to maximize the capacity performance of carbon negative electrode materials, reduce the charge and discharge expansion rate of carbon negative electrode materials, and improve the cycle performance, the technical concept proposed in this application is: by optimizing the doping method, more doping elements are allowed to enter the interior of the carbon layers of the carbon negative electrode materials, thereby obtaining a carbon negative electrode material with a uniformity of doping element distribution between the carbon layers of at least greater than or equal to 35%, solving the problem of oversaturation of doping elements on the surface and lack of doping elements in the inner layer of conventional doped carbon materials, realizing full and uniform combination of carbon atoms and doping elements, and maximizing the role of doping elements in improving the capacity performance of carbon negative electrode materials.

[0074] Based on the above technical concept, the embodiments of the present application provide a carbon negative electrode material and a preparation method and application thereof.

[0075] In a first aspect, the present application provides a carbon negative electrode material, which includes a carbon matrix, wherein the carbon matrix contains doping elements between carbon layers, and the doping elements have a distribution uniformity greater than or equal to 35%.

[0076] In particular implementation, due to the problem of surface layer supersaturation of the doping elements in the conventional doped carbon material, the uneven distribution of the doping elements leads to limited overall improvement of the capacity performance of the carbon negative electrode material. Further, the surface layer supersaturation of the doping elements in the doped carbon material also causes the carbon skeleton of the surface layer of the carbon negative electrode material to be loose and rich in oxygen components, which on the one hand leads to collapse of the carbon skeleton of the surface layer in the long cycle process and a decrease in cycle retention rate, and on the other hand, the oxygen components of the surface layer are prone to side reactions with electrolyte ions, leading to cycle performance degradation. In view of this, the carbon negative electrode material provided in the present application has more doping elements distributed in the interior of the carbon layers of the carbon matrix, so that the carbon atoms in the carbon matrix and the doping elements are more fully and uniformly combined, the uniformity of the distribution of the doping elements is at least greater than or equal to 35%, and the doping elements are maximally used to improve the capacity performance of the carbon negative electrode material. The surface layer doping of the conventional doped carbon material is solved.

[0077] In some embodiments, the doping elements include at least one of boron, nitrogen, phosphorus, and sulfur.

[0078] In some embodiments, the carbon negative electrode material has a median particle size of 1 μm-40 μm.

[0079] In some embodiments, the carbon negative electrode material has a specific surface area of 0.5 m 2 / g-300 m 2 / g.

[0080] In some embodiments, the carbon negative electrode material has a doping element content of 0.05wt%-12wt%.

[0081] In some embodiments, the carbon matrix has a carbon layer spacing of 0.35 nm-0.44 nm.

[0082] In some embodiments, the carbon negative electrode material has a doping element distribution uniformity of greater than or equal to 50%.

[0083] In some embodiments, the carbon negative electrode material further includes a carbon coating layer formed on the surface of the carbon matrix.

[0084] In some embodiments, the carbon coating layer has a thickness of 0 μm-5 μm.

[0085] In particular implementation, the carbon negative electrode material provided in the present application can include a first carbon negative electrode material, a second carbon negative electrode material, a third carbon negative electrode material, or a fourth carbon negative electrode material, and the carbon layers of the carbon negative electrode material contain doping elements, wherein the first carbon negative electrode material is obtained by pre-carbonization, modification, doping, and purification treatment of a raw material containing a carbon source, and the parameter characteristics thereof include but are not limited to the following values:

[0086] a median particle size of 1 μm-30 μm;

[0087] The specific surface area is 1.0 m 2 / g-300 m 2 / g;

[0088] The content of the doping element is 0.1wt%-12wt%;

[0089] The carbon layer spacing is 0.35nm-0.44nm;

[0090] The uniformity of the doping element distribution is greater than or equal to 35%;

[0091] The second carbon negative electrode material is obtained by secondary granulation of the first carbon negative electrode material, and the parameter characteristics include but are not limited to the following numerical values:

[0092] The median particle size is 4μm-40μm;

[0093] The specific surface area is 0.5 m 2 / g-100 m 2 / g;

[0094] The content of the doping element is 0.05wt%-10wt%;

[0095] The uniformity of the doping element distribution is greater than or equal to 50%;

[0096] The third carbon negative electrode material is obtained by secondary granulation and carbon coating of the first carbon negative electrode material, and the parameter characteristics include but are not limited to the following numerical values:

[0097] The coating layer thickness is 0μm-5μm;

[0098] The median particle size is 4μm-40μm;

[0099] The specific surface area is 0.5 m 2 / g-100 m 2 / g;

[0100] The content of the doping element is 0.05wt%-10wt%;

[0101] The uniformity of the doping element distribution is greater than or equal to 50%;

[0102] The fourth carbon negative electrode material is obtained by directly carbon coating the first carbon negative electrode material without secondary granulation, and the parameter characteristics include but are not limited to the following numerical values:

[0103] The carbon coating layer thickness is 0μm-5μm;

[0104] The median particle size is 1μm-30μm;

[0105] The specific surface area is 1.0 m 2 / g-300 m 2 / g;

[0106] the doping element content is 0.1wt%-12wt%;

[0107] the carbon layer spacing is 0.35nm-0.44nm;

[0108] the doping element distribution uniformity is greater than or equal to 35%.

[0109] The carbon negative electrode material provided in the application is subjected to carbon coating treatment after secondary granulation of the carbon negative electrode material, and a carbon negative electrode material with a carbon coating layer is obtained, the doping uniformity of the doping element is further improved due to the granulation. In addition, the carbon coating layer can effectively prevent the doping element in the carbon negative electrode material from directly contacting the electrolyte in the battery, and avoid the occurrence of an electrochemical side reaction between the doping element and the electrolyte to be consumed. Therefore, the cycle performance of the carbon negative electrode material can be effectively improved.

[0110] In a second aspect, the application provides a preparation method of the carbon negative electrode material provided in the first aspect, Figure 1 a flowchart of the preparation method of the carbon negative electrode material provided in the embodiments of the application is shown. Referring to Figure 1 The preparation method of the carbon negative electrode material includes the following steps:

[0111] S11, under the action of a mixed gas, pre-carbonizing a raw material containing a carbon source to obtain a first precursor with porosity and oxygen-rich carbon layers; wherein the mixed gas includes a protective gas and an oxidizing gas;

[0112] S12, in a protective gas atmosphere, modifying and modifying the first precursor with a modifying modifier to obtain a second precursor containing intercalation in the carbon layer; and performing first purification treatment on the product obtained after the modifying and modifying reaction ends;

[0113] S13, in a protective gas atmosphere, doping the second precursor containing intercalation in the carbon layer with a dopant to obtain a carbon negative electrode material, and performing second purification treatment on the product obtained after the doping reaction ends.

[0114] In specific implementation, in order to enable more doping elements to enter the carbon material inside and further improve the capacity performance of the carbon negative electrode material, the application improves the pre-carbonization conditions of the carbon source, provides a large number of reaction sites for the subsequent modifying and modifying reaction, and uses the modifying modifier to modify the intercalation of the precursor obtained after pre-carbonization, provides a large number of reaction sites for the subsequent doping reaction, reduces the energy barrier of the subsequent doping reaction, and enables more doping elements to enter the carbon material inside through the doping reaction.

[0115] In particular, the embodiment is to pre-carbonize the carbon source under the action of trace oxidative gas to obtain a pre-carbonized product, and then crush the pre-carbonized product to obtain a porous and oxygen-rich interlayer carbon powder-shaped first precursor. The porous first precursor is beneficial to the diffusion of the subsequent modification modifier in the first precursor particle. The oxygen-rich interlayer carbon provides a large number of reaction sites for the modification reaction, reduces the energy barrier of the modification reaction, and is beneficial to the full implementation of the subsequent modification reaction.

[0116] In some embodiments, the oxidative gas is at least one of air, oxygen, ozone, ammonia, chlorine, water vapor, carbon dioxide, and carbon monoxide.

[0117] In some embodiments, the protective gas includes at least one of nitrogen, argon, neon, helium, xenon, and krypton.

[0118] In some embodiments, the content of the oxidative gas is 0.1wt%-2wt%.

[0119] In some embodiments, the carbon source includes at least one of almond shell, coconut shell, walnut shell, jujube kernel shell, peach kernel shell, rice husk, peanut shell, melon seed shell, pistachio shell, hazelnut shell, straw, wood chips, vinasse, starch, sucrose, glucose, phenolic resin, epoxy resin, melamine resin, furfural resin, urea-formaldehyde resin, pitch, petroleum coke, needle coke, mesocarbon microbeads, and anthracite.

[0120] In particular, as an optional embodiment, the addition of a curing agent to the above-mentioned carbon source can improve the cross-linking degree between the structural units (graphite microcrystals) of the carbon material in the pre-carbonization process, thereby improving the disorder degree of the arrangement of the structural units (graphite microcrystals), which is more conducive to the enrichment of oxygen between the carbon layers to obtain a porous and oxygen-rich interlayer carbon first precursor. In addition, the curing agent can be introduced as an active energy storage site to improve the capacity performance of the obtained target carbon negative electrode material.

[0121] Therefore, in some embodiments, a curing agent can also be added to the carbon source, and the mass ratio of the carbon source to the curing agent is 5-95:95-5.

[0122] In some embodiments, the curing agent can include at least one of melamine, hexamethylenetetramine, p-benzaldehyde, ammonium chloride, ammonium bromide, ammonium fluoride, ammonium iodide, ammonium sulfide, ammonium phosphate, dihydrogen ammonium phosphate, ammonium dihydrogen phosphate, ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium oxalate, and ammonium acetate.

[0123] In some embodiments, the reaction temperature for pre-carbonization is 300°C-800°C.

[0124] In some embodiments, the reaction time is 0.1h-24h.

[0125] In some embodiments, the mass ratio of the first precursor to the modification modifier is 70-99:1-30.

[0126] In specific implementation, the first precursor and the modification modifier obtained are further subjected to a modification reaction, so that the intercalation is inserted between the carbon layers to obtain a second precursor; after the second precursor obtained is subjected to a doping reaction, the intercalation between the carbon layers is replaced by the doping element to obtain a carbon negative electrode material with the doping element between the carbon layers. The modification modifier is a kind of reagent with carburizing characteristics, which can incorporate the effective component (intercalation) into the interior and between the carbon layers of the carbon material and increase the carbon layer spacing at a certain temperature. In addition, the modification reaction reduces the energy barrier of the doping reaction in the subsequent step, so that the intercalation inserted into the carbon layer is more easily replaced by the doping element and removed in the doping reaction, thereby realizing sufficient doping of the doping element between the carbon layers and improving the doping uniformity of the doping element of the carbon material and the capacity performance of the carbon negative electrode material.

[0127] In specific implementation, the modification modifier is a kind of reagent with carburizing characteristics, which can incorporate the effective component (intercalation) into the interior and between the carbon layers of the first precursor with porosity and oxygen-rich carbon layers and increase the carbon layer spacing at a certain temperature, and affect the type of doping reaction of the doping element in the subsequent step. That is, the intercalation inserted into the carbon layer is more easily replaced by the doping element and removed in the subsequent doping reaction, effectively reducing the energy barrier of the doping reaction and realizing sufficient doping of the doping element between the carbon layers.

[0128] In some embodiments, the modification modifier includes halogen and compounds thereof.

[0129] In some embodiments, the modification modifier is halogen and compounds thereof, and the halogen and compounds thereof include at least one of aluminum chloride, iron chloride, iron bromide, zinc chloride, zinc bromide, iodine, chlorine water, bromine water, iodine water, and liquid bromine.

[0130] In some embodiments, the reaction temperature of the modification reaction is 200°C-800°C.

[0131] In some embodiments, the reaction time is 0.1h-24h.

[0132] In specific implementation, halogen and compounds thereof are used as the modification modifier, and the intercalation can be inserted into the carbon layer of the first precursor through heat treatment, thereby achieving the modification purpose of the first precursor.

[0133] In some embodiments, the modification modifier can also include a mixture of a reaction additive and an alkali metal salt and / or an alkali metal oxide.

[0134] In some embodiments, the modification modifier can further include a mixture of a reaction additive and an alkali metal salt and / or an alkali metal oxide, wherein the mass ratio of the reaction additive to the alkali metal salt and / or the alkali metal oxide is 1:0.5-5.

[0135] In some embodiments, the alkali metal salt and / or the alkali metal oxide includes at least one of lithium oxide, lithium carbonate, lithium acetate, lithium oxalate, sodium oxide, sodium acetate, sodium oxalate, sodium peroxide, sodium carbonate, sodium bicarbonate, magnesium oxide, magnesium carbonate, potassium oxide, potassium carbonate, and potassium bicarbonate.

[0136] In some embodiments, the reaction additive includes at least one of glucose, fructose, sucrose, polystyrene, polyvinyl chloride, polyvinyl alcohol, phenolic resin, melamine resin, furfural resin, urea-formaldehyde resin, and asphalt.

[0137] In particular implementation, when the alkali metal salt and / or the alkali metal oxide is used as the modification modifier, it is required to be reacted with the reaction additive under heating to generate alkali metal or alkaline earth metal elements, and then the alkali metal or alkaline earth metal elements are inserted into the carbon layers of the first precursor through self-discharge reaction, so as to achieve the purpose of modification and modification of the first precursor.

[0138] In some embodiments, the reaction temperature of the modification and modification reaction is 200-800°C.

[0139] In some embodiments, the reaction time of the modification and modification reaction is 0.1-24h.

[0140] In some embodiments, the mass ratio of the second precursor to the dopant is 70-99:1-30.

[0141] In some embodiments, the dopant includes at least one of a boron source, a nitrogen source, a phosphorus source, and a sulfur source.

[0142] The boron source includes at least one of boric acid, borax, boron trioxide, sodium borohydride, sodium borate, calcium borate, zinc borate, magnesium borate, iron borate, titanium boride, and sodium tetraphenylborate.

[0143] The phosphorus source includes at least one of phosphorus trichloride, diphosphorus pentoxide, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, phosphate ester, red phosphorus, and black phosphorus.

[0144] The nitrogen source includes at least one of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acid, and ammonium bicarbonate.

[0145] The sulfur source includes at least one of sulfur powder, thiourea, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, and cysteine.

[0146] In some embodiments, the reaction temperature of the doping reaction is 800-1300°C.

[0147] In some embodiments, the reaction time is 0.1-24h.

[0148] In actual implementation, the modification and modification reaction of the first precursor with the modification modifier is accompanied by the generation of useless reaction byproducts; therefore, to eliminate the influence of the reaction byproducts and the modification modifier not involved in the reaction on the subsequent reaction, the product obtained after the modification and modification reaction is required to be subjected to first purification treatment with an acidic reagent in the embodiments of the present application.

[0149] In actual implementation, the doping reaction of the second precursor with the dopant is also accompanied by the generation of useless reaction byproducts; therefore, to eliminate the influence of the reaction byproducts and the dopant not involved in the reaction on the subsequent reaction, the product obtained after the doping reaction is required to be subjected to second purification treatment with an acidic reagent in the embodiments of the present application.

[0150] In some embodiments, the purification treatment is performed in an acidic reagent.

[0151] In some embodiments, the acidic reagent can be at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, acetic acid, oxalic acid, benzoic acid, hydrogen sulfide acid, hydrogen bromide acid and hydrogen iodide acid.

[0152] For example, the first purification treatment process can be as follows: the mixture of the first precursor and the modification modifier after the second high-temperature treatment is mixed with acid and deionized water in a mass ratio of 1:0.3-2:3-10 and stirred for more than 0.5h, then solid-liquid separation is performed, the obtained solid is washed with deionized water or pure water until PH=4-7, and drying is performed to obtain the second precursor without impurities.

[0153] For example, the second purification treatment process can be as follows: the mixture of the second precursor and the dopant after the third high-temperature treatment is mixed with acid and deionized water in a mass ratio of 1:0.3-2:3-10 and stirred for more than 0.5h, then solid-liquid separation is performed, the obtained solid is washed with deionized water or pure water until PH=4-7, and drying is performed to obtain the carbon negative electrode material without impurities. The solid-liquid separation method can be centrifugation or filtration; and the drying equipment can be an oven, a double-cone dryer, a push plate kiln, or a box furnace.

[0154] In specific implementation, to obtain a carbon negative electrode material with higher uniformity of doping element distribution, the present embodiment performs carbon coating on the surface of the carbon negative electrode material or performs carbon coating after secondary granulation of the carbon negative electrode material, wherein the secondary granulation further improves the uniformity of doping of the doping element in the amorphous carbon material. Thus, the doping of the doping element to improve the capacity performance of the carbon material is maximized. Carbon coating can reduce direct contact between the doping element in the carbon negative electrode material and the electrolyte in the battery, thereby reducing the consumption of the doping element due to electrochemical side reactions between the doping element and the electrolyte, and further reducing the cycle performance of the carbon negative electrode material.

[0155] In some embodiments, the granulation process can be spray drying granulation or VC heating granulation.

[0156] For example, the spray drying granulation process can be performed according to the following steps: uniformly mixing the carbon negative electrode material, the binder and the solvent according to a certain mass ratio, performing spray drying, then transferring to a certain sealed container, and pyrolyzing in an inert atmosphere at 500-1300°C, VC dispersing, and cooling to room temperature. The binder can be at least one of pitch, sucrose, glucose, phenolic resin, epoxy resin, melamine resin, furfural resin and urea-formaldehyde resin; the solvent can be at least one of deionized water, ethanol, diethyl ether, isopropyl alcohol, acetone and tetrahydrofuran; the mass ratio of the carbon negative electrode material and the binder can be 60-80:20-40, and the mass ratio of (carbon negative electrode material+binder) and the solvent can be 1-40:60-99; the spray drying inlet temperature can be 300°C, the outlet temperature can be 110°C, and the feeding rate can be 10-40 mL / min.

[0157] For example, the VC heating granulation process can be performed according to the following steps: putting the mixture of the carbon negative electrode material and the binder (the same binder as used in the spray drying granulation) into a VC heating machine, and under the conditions of inert atmosphere protection and stirring speed of 30-120 rpm / min, heating to 250-300°C, holding for 0.1-24 h, then heating to 500-700°C, holding for 0.1-24 h, and finally cooling to room temperature. The mass ratio of the carbon negative electrode material and the binder can be 60-80:20-40.

[0158] In some embodiments, the carbon coating process can include any one of solid phase coating, liquid phase coating, VC heating coating and gas phase coating; wherein the coating carbon source of the solid phase coating, the liquid phase coating and the VC heating coating is at least one of pitch, sucrose, glucose, phenolic resin, epoxy resin, melamine resin, furfural resin and urea-formaldehyde resin.

[0159] In some embodiments, the gas-phase coating carbon source includes at least one of ethanol, methane, ethane, propane, acetone, ethylene, acetylene, benzene, toluene, and xylene.

[0160] For example, the solid-phase coating process can be performed according to the following steps: carbonizing the mixture of the granulated material and the coating carbon source at 900-1300°C, wherein the mass ratio of the granulated material to the coating carbon source is 85-99:1-15, and the coating carbon source is at least one of pitch, sucrose, glucose, phenol formaldehyde resin, epoxy resin, melamine resin, furfural resin, urea formaldehyde resin, polystyrene, polyvinyl alcohol, polyvinyl chloride, and polytetrafluoroethylene.

[0161] For example, the liquid-phase coating process can be performed according to the following steps: adding the granulated material and the coating carbon source (the same as the coating carbon source used in the solid-phase coating process) into a solvent, stirring to obtain a slurry, performing spray drying and carbonization treatment. The solvent can be at least one of water, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, and ethyl acetate; the mass ratio of the granulated material to the coating carbon source can be 85-99:1-15, and the mass ratio of (the granulated material + the coating carbon source) to the solvent can be 1-40:60-99; the inlet temperature of the spray drying can be 300°C, the outlet temperature can be 110°C, and the feeding rate can be 10-40 mL / min; and the carbonization temperature can be 900-1300°C.

[0162] For example, the VC heating coating process can be performed according to the following steps: uniformly mixing the granulated material and the coating carbon source (the same as the coating carbon source used in the solid-phase coating process) at a mass ratio of 85-99:1-15, and then putting the mixture into a VC heating machine, heating to 250-300°C under an inert gas atmosphere and at a stirring speed of 30-120 rpm / min, and keeping the temperature for 0.1-24 h, and then cooling to room temperature.

[0163] For example, the gas-phase coating process can be performed according to the following steps: putting the granulated material into a rotary furnace at a rotating speed of 0.5-3 rpm / min, heating to 750-1000°C under an inert gas atmosphere, introducing an organic carbon source (in gaseous form) for 1-10 h, stopping the introduction of the organic carbon source, cooling to room temperature, and then performing carbonization treatment at 900-1300°C. The organic carbon source can be at least one of methane, ethane, propane, ethylene, acetylene, benzene, toluene, xylene, ethanol, and acetone.

[0164] Figure 2 A flowchart of a method for preparing a carbon negative electrode material is shown in FIG. 1. Figure 2As shown, in the embodiment of the present application, the carbon negative electrode material (first carbon negative electrode material) obtained after pre-carbonization, modification and doping reaction of the carbon source is subjected to secondary granulation and carbon coating to obtain a secondary granulated and carbon-coated carbon negative electrode material (third carbon negative electrode material). Among them, the carbon negative electrode material with a carbon coating layer can effectively reduce the direct contact between the doping elements in the carbon negative electrode material and the electrolyte in the battery, avoiding the electrochemical side reaction between the doping elements and the electrolyte and consumption, thereby ensuring that the carbon negative electrode material provided in the embodiment of the present application has good cycle performance.

[0165] Figure 3 The schematic diagram of the structure of the carbon negative electrode material provided in the embodiment of the present application is shown in FIG. Figure 3 As shown in the figure, in the carbon negative electrode materials provided in the embodiments of the present application, 1 represents the secondary granulated carbon negative electrode material (second carbon negative electrode material); 2 represents the carbon coating layer. The carbon coating layer on the surface can effectively reduce direct contact between the electrolyte and the doping element, preventing the doping element from being consumed by electrochemical side reactions with the electrolyte, effectively reducing the charge and discharge expansion rate of the carbon material, and thus improving the cycle performance of the carbon negative electrode material.

[0166] In a third aspect, the present application provides an application of a carbon negative electrode material, wherein the carbon negative electrode material provided in the first aspect is applied to a battery by using the carbon negative electrode material prepared by the preparation method provided in the second aspect.

[0167] In order to enable those skilled in the art to understand the present application more clearly, the preparation method of the carbon negative electrode material described in the present application is now described in detail through the following examples.

[0168] Example 1

[0169] S1: Thermoplastic phenolic resin and hexamethylenetetramine were mixed in a mass ratio of 90:10, pre-carbonized at 630°C for 1 hour under an oxygen-containing atmosphere (oxygen and nitrogen mass ratio of 2:98), crushed using a crusher with a 3 mm mesh, and ball-milled to a median particle size of about 4.5 μm to obtain a first precursor;

[0170] S2: Mix the first precursor and ferric chloride in a mass ratio of 9:1, heat to 300°C under a nitrogen atmosphere, hold for 1 hour, and cool. Mix the resulting material, hydrochloric acid, and deionized water in a mass ratio of 1:0.5:5, stir for 2 hours, filter, and wash the resulting solid with deionized water to a pH of 4-7, and dry to obtain the second precursor.

[0171] S3: The second precursor and phosphorus pentoxide are mixed in a mass ratio of 95:5, transferred to a box furnace, heated to 1000 DEG C under a nitrogen atmosphere for 1h, and cooled. The obtained material, hydrochloric acid, and deionized water are mixed in a mass ratio of 1:1:10, stirred for 2h, filtered, and the obtained solid is washed with deionized water until PH = 4-7, centrifuged and dried, VC mixed, and 325 mesh sieved to obtain the first carbon negative electrode material;

[0172] S4: The first carbon negative electrode material and glucose are mixed in a mass ratio of 80:20, added to deionized water with a solid content of 30%, stirred for 2h, spray dried and granulated, and the obtained material is transferred to a box furnace, heated to 600 DEG C under a helium atmosphere for 2h to obtain the second carbon negative electrode material.

[0173]

[0174] Figure 4 The SEM diagram of the carbon negative electrode material provided by the embodiment of the application is shown in FIG. 1, and the SEM diagram of the third carbon negative electrode material provided by the embodiment of the application is shown in FIG. 2. Figure 4 As shown in FIG. 2, the third carbon negative electrode material provided by the embodiment of the application is uniform in size and has a relatively dense surface coating.

[0175] Embodiment 2

[0176] S1: Starch and ammonium bicarbonate are mixed in a mass ratio of 90:10, pre-carbonized at 600 DEG C for 24h under an oxygen-containing atmosphere (carbon dioxide and helium in a mass ratio of 2:98), broken, wet ball milled and pulverized to a median particle size of about 5um to obtain a first precursor;

[0177] S2: The first precursor, lithium carbonate, and polyvinyl alcohol are mixed in a mass ratio of 9:1:2, heated to 500 DEG C under a krypton atmosphere for 1h, and cooled. The obtained material, nitric acid, and deionized water are mixed in a mass ratio of 1:0.3:3, stirred for 2h, centrifuged, and the obtained solid is washed with deionized water until PH = 4-7, dried, and a second precursor is obtained;

[0178] S3: The second precursor and melamine are mixed in a mass ratio of 85:15, transferred to a box furnace, heated to 800 DEG C under a nitrogen atmosphere for 2h, and cooled. The obtained material, benzoic acid, and deionized water are mixed in a mass ratio of 1:1:10, stirred for 24h, centrifuged, and the obtained solid is washed with deionized water until PH = 4-7, centrifuged and dried, VC mixed, and 325 mesh sieved to obtain the first carbon negative electrode material;​

[0179] S4: The first carbon negative electrode material and the phenolic resin (passed through a 30-mesh sieve) were mixed according to a mass ratio of 95:5, transferred to a tube furnace, sintered at 1200°C for 4h under an argon atmosphere, cooled, mixed in a VC, sieved through a 325-mesh sieve, and a third carbon negative electrode material was obtained.

[0180] S5: The second carbon negative electrode material and the phenolic resin (passed through a 30-mesh sieve) were mixed according to a mass ratio of 95:5, transferred to a tube furnace, sintered at 1200°C for 4h under an argon atmosphere, cooled, mixed in a VC, sieved through a 325-mesh sieve, and a third carbon negative electrode material was obtained.

[0181] Example 3

[0182] S1: Sucrose was pre-carbonized at 600°C for 24h under an oxygen-containing atmosphere (ammonia and nitrogen in a mass ratio of 1:99), crushed, and mechanically pulverized to a median particle size of 14μm to obtain a first precursor;

[0183] S2: The first precursor and zinc chloride were mixed according to a mass ratio of 8:2, heated to 600°C for 2h under an argon atmosphere, and cooled. The obtained material, hydrochloric acid, and deionized water were mixed according to a mass ratio of 1:1:4, stirred for 2h, filtered, and the obtained solid was washed with deionized water until the pH was 4-7, dried, and a second precursor was obtained;

[0184] S3: The second precursor and boric acid were mixed according to a mass ratio of 90:10, transferred to a box furnace, heated to 800°C for 1h under a helium atmosphere, and cooled. The obtained material, hydrochloric acid, and deionized water were mixed according to a mass ratio of 1:0.5:8, stirred for 2h, filtered, and the obtained solid was washed with deionized water until the pH was 4-7, centrifuged and dried, mixed in a VC, sieved through a 325-mesh sieve, and a first carbon negative electrode material was obtained;

[0185] S4: The first carbon negative electrode material and the phenolic resin (passed through a 30-mesh sieve) were mixed according to a mass ratio of 95:5, transferred to a tube furnace, sintered at 1200°C for 4h under an argon atmosphere, cooled, mixed in a VC, sieved through a 325-mesh sieve, and a third carbon negative electrode material was obtained.

[0186] S5: The second carbon negative electrode material and the phenolic resin (passed through a 30-mesh sieve) were mixed according to a mass ratio of 95:5, transferred to a tube furnace, sintered at 1200°C for 4h under an argon atmosphere, cooled, mixed in a VC, sieved through a 325-mesh sieve, and a third carbon negative electrode material was obtained.

[0187] Example 4

[0188] S1: The washed and dried coconut shell was pre-carbonized at 800℃ for 1h under an oxygen-containing atmosphere (mass ratio of water vapor and nitrogen was 0.2:99.8), crushed, and air-jet pulverized to a median particle size of about 7μm to obtain a first precursor;

[0189] S2: The first precursor and iodine powder were mixed in a mass ratio of 95:5, heated to 400℃ under an argon atmosphere for 2h, and cooled. The obtained material, acetic acid, and deionized water were mixed in a mass ratio of 1:2:5, stirred for 2h, filtered, and the obtained solid was washed with deionized water until the pH was 4-7, dried, and a second precursor was obtained;

[0190] S3: The second precursor and sulfur powder were mixed in a mass ratio of 93:7, transferred to a box furnace, heated to 900℃ under an argon atmosphere for 2h, and cooled. The obtained material, hydrobromic acid, and deionized water were mixed in a mass ratio of 1:0.6:6, stirred for 24h, filtered, and the obtained solid was washed with deionized water until the pH was 4-7, centrifuged, dried, mixed with VC, and sieved through a 325 mesh screen to obtain a first carbon negative electrode material;

[0191] S4: The first carbon negative electrode material and thermosetting phenolic resin were mixed in a mass ratio of 65:35, put into a VC heating machine, rotated at 100rpm / min, heated to 250℃ under a nitrogen atmosphere for 2h, continuously heated to 600℃ for 6h, cooled, and a second carbon negative electrode material was obtained;

[0192] S5: The second carbon negative electrode material and polyvinyl chloride (sieved through a 30 mesh screen) were put into tetrahydrofuran in a mass ratio of 85:15, stirred for 2h, spray dried, transferred to a box furnace, sintered at 1050℃ under a nitrogen atmosphere for 24h, cooled, mixed with VC, and sieved through a 325 mesh screen to obtain a third carbon negative electrode material.

[0193] Example 5

[0194] S1: The pitch was pre-carbonized at 500℃ for 1h under an oxygen-containing atmosphere (mass ratio of oxygen and nitrogen was 2:98), crushed using a crusher with a 3mm screen, and ball-milled to a median particle size of about 6μm to obtain a first precursor;

[0195] S2: The first precursor, sodium oxide, and sucrose were mixed in a mass ratio of 8:0.5:1.5, heated to 500℃ under a nitrogen atmosphere for 1h, and cooled. The obtained material, hydrochloric acid, and deionized water were mixed in a mass ratio of 1:0.5:3, stirred for 2h, filtered, and the obtained solid was washed with deionized water until the pH was 4-7, dried, and a second precursor was obtained;

[0196] S3: The second precursor and ammonium phosphate are mixed in a mass ratio of 9:1, transferred to a box furnace, heated to 1000°C under a nitrogen atmosphere, and held for 1 h, and then cooled. The obtained material, hydrochloric acid, and deionized water are mixed in a mass ratio of 1:1:10, stirred for 2 h, filtered, and the obtained solid is washed with deionized water until the pH is 4-7, centrifuged, dried, mixed with VC, and sieved through a 325 mesh screen to obtain a first carbon negative electrode material;

[0197] S4: The first carbon negative electrode material and pitch (median particle size 2 μm) are mixed in a mass ratio of 80:20, added to isopropyl alcohol with a solid content of 30%, stirred for 2 h, spray dried and granulated, and the obtained material is transferred to a box furnace, heated to 600°C under a helium atmosphere, and held for 2 h to obtain a second carbon negative electrode material;

[0198] S5: The second carbon negative electrode material and pitch (median particle size 2 μm) are mixed in a mass ratio of 90:10, placed in a VC heating machine, rotated at a speed of 120 rpm / min, heated to 250°C under a nitrogen atmosphere, and held for 3 h, then heated to 500°C and held for 2 h, cooled, transferred to a tube furnace, heated to 1100°C under a xenon atmosphere, and held for 2 h, mixed with VC, and sieved through a 325 mesh screen to obtain a third carbon negative electrode material.

[0199] Example 6

[0200] S1: Almond shells are pre-carbonized at 300°C under an oxygen atmosphere (oxygen and argon in a mass ratio of 1:99) for 4 h, broken using a 3 mm screen crusher, and ball milled to a median particle size of about 5 μm to obtain a first precursor;

[0201] S2: The first precursor and aluminum chloride are mixed in a mass ratio of 8:2, heated to 400°C under a helium atmosphere, and held for 2 h, and then cooled. The obtained material, hydrochloric acid, and deionized water are mixed in a mass ratio of 1:1:8, stirred for 1 h, centrifuged, and the obtained solid is washed with deionized water until the pH is 4-7, dried, and a second precursor is obtained;

[0202] S3: The second precursor and ammonium phosphate are mixed in a mass ratio of 92:8, transferred to a box furnace, heated to 950°C under an argon atmosphere, and held for 2 h, and then cooled. The obtained material, nitric acid, and deionized water are mixed in a mass ratio of 1:2:3, stirred for 2 h, filtered, and the obtained solid is washed with deionized water until the pH is 4-7, centrifuged, dried, mixed with VC, and sieved through a 325 mesh screen to obtain a first carbon negative electrode material;

[0203] S4: The first carbon negative electrode material and thermosetting phenolic resin are mixed in a mass ratio of 70:30, added to deionized water with a solid content of 30%, stirred for 2 h, spray dried and granulated, and the obtained material is transferred to a box furnace, heated to 600°C under a nitrogen atmosphere, and held for 2 h to obtain a second carbon negative electrode material;

[0204] S5: The second carbon negative electrode material and sucrose were mixed in a mass ratio of 92:8, and were put into a VC heating machine, with a rotation speed of 120 rpm / min, and were heated to 180°C under a nitrogen atmosphere for 3h, and were continuously heated to 600°C for 3h, and were cooled, and were transferred to a box furnace and were heated to 1300°C under a xenon atmosphere for 2h, and were mixed in a VC, and were sieved to obtain a third carbon negative electrode material.

[0205] Example 7

[0206] The difference from Example 1 is that S2 is: the first precursor, lithium carbonate and glucose were mixed in a mass ratio of 8.5:1:0.5, and were heated to 300°C under a nitrogen atmosphere for 1h, and were cooled. The obtained material, hydrochloric acid and deionized water were mixed in a mass ratio of 1:0.5:5, and were stirred for 2h, and were filtered, and the obtained solid was washed with deionized water until the pH was 4-7, and was dried to obtain a second precursor; other conditions were the same as in Example 1.

[0207] Example 8

[0208] The difference from Example 1 is that the ball milling in S1 is adjusted to a median particle size of 12μm from 3μm, and the granulation in step S4 is not performed; S2 is the same as in Example 1. S3 is adjusted to mix the second precursor and phosphorus pentoxide in a mass ratio of 95:5, and are transferred to a box furnace and are heated to 1000°C under a nitrogen atmosphere for 1h, and are cooled. The obtained material, hydrochloric acid and deionized water are mixed in a mass ratio of 1:1:10, and are stirred for 2h, and are filtered, and the obtained solid is washed with deionized water until the pH is 4-7, and is centrifuged and dried, and is mixed in a VC, and is sieved to 325 mesh. The obtained material and pitch (median particle size 3μm) are mixed in a mass ratio of 90:10, and are put into a VC heating machine, with a rotation speed of 120 rpm / min, and are heated to 250°C under a nitrogen atmosphere for 3h, and are continuously heated to 500°C for 2h, and are cooled, and are transferred to a tube furnace and are heated to 1100°C under a xenon atmosphere for 2h, and are mixed in a VC, and are sieved to 325 mesh, i.e. S4 and S5 are not performed, and a fourth carbon negative electrode material is obtained after S6.

[0209] Example 9

[0210] The difference from Example 1 is that the carbon coating in step S5 is not performed, i.e. the obtained material after spray drying is transferred to a tube furnace and is heated to 1100°C under a xenon atmosphere for 2h, and is mixed in a VC, and is sieved to 325 mesh to obtain a second carbon negative electrode material, and other conditions are the same.

[0211] Example 10

[0212] S1: thermosetting phenolic resin was pre-carbonized at 650℃ for 2h under mixed gas of oxygen and nitrogen (mass ratio of 2:98), crushed by a crusher with 3mm screen, and ball-milled to a median particle size of about 9μm to obtain a first precursor;

[0213] S2: the first precursor and aluminum chloride were mixed according to a mass ratio of 9:1, heated to 450℃ under nitrogen atmosphere, and kept for 2h. The obtained material, sulfuric acid, and deionized water were mixed according to a mass ratio of 1:1:10, stirred for 1h, filtered, and the obtained solid was washed with deionized water until PH=4-7, dried, and a second precursor was obtained;

[0214] S3: the second precursor and ammonium dihydrogen phosphate were mixed according to a mass ratio of 96:4, transferred to a box furnace, heated to 1100℃ under nitrogen atmosphere, kept for 1h, and cooled. The obtained material, hydrochloric acid, and deionized water were mixed according to a mass ratio of 1:1:5, stirred for 2h, filtered, and the obtained solid was washed with deionized water until PH=4-7, centrifuged, dried, mixed with VC, sieved by a 325 mesh screen, and a first carbon negative electrode material was obtained.

[0215] Comparative Example 1

[0216] The difference from Example 1 is that in step S1, the pre-carbonization atmosphere is nitrogen atmosphere, and other conditions are the same.

[0217] Comparative Example 2

[0218] The difference from Example 1 is that in step S1, the pre-carbonization is first carried out under nitrogen atmosphere, and then pretreated under an oxygen-containing atmosphere, i.e. pre-carbonization under nitrogen atmosphere at 630℃ for 1h, and then heated to 630℃ under an oxygen-containing atmosphere (oxygen and nitrogen mass ratio of 2:98) for 1h, and other conditions are the same.

[0219] Comparative Example 3

[0220] The difference from Example 1 is that step S2 is not carried out, i.e. no modification is carried out, and other conditions are the same.

[0221] Comparative Example 4

[0222] The difference from Example 1 is that step S3 is not carried out, i.e. no doping modification is carried out after modification, and other conditions are the same.

[0223] Comparative Example 5

[0224] The difference from Example 7 is that no reaction additive (glucose) is added in S2, i.e. S2 is: the first precursor, lithium carbonate and 8.5:1 in mass ratio are mixed, heated to 300°C under nitrogen atmosphere, and kept for 1 h, and then cooled. The obtained material, hydrochloric acid and deionized water are mixed in a mass ratio of 1:0.5:5, stirred for 2 h, filtered, and then the obtained solid is washed with deionized water until PH = 4-7, dried, and the second precursor is obtained; and other conditions are the same as in Example 7.

[0225] Test method

[0226] 1. Analysis of content of doping elements (B, N, P, S)

[0227] The carbon negative electrode material prepared in the above examples of the present application is respectively loaded in a certain carrier, cut by a high-energy argon ion beam to obtain a cross-section sample, and SEM combined with EDS (using a Hitachi S4800 scanning electron microscope to test SEM photos; scanning electron microscope combined with X-ray energy spectrum (EDS) is tested at 1000 times) is used to analyze the content of doping elements (B, N, P, S).

[0228] Figure 5 A cross-sectional schematic diagram of the carbon negative electrode material provided by the embodiments of the present application is shown, as shown in Figure 5 The particle cross-sectional area with a size of 8-20 μm is randomly selected, wherein D1, D2, D3 are respectively three areas (areas 1 / 2 / 3) with a maximum distance ≤1.5 μm from the edge of the particle cross-section, and D4, D5, D6 are respectively three areas (areas 4 / 5 / 6) with a maximum distance ≥2 μm from the edge of the particle cross-section. Figure 5 As shown in the figure, three areas (areas 1 / 2 / 3) with a maximum distance (D1, D2, D3) ≤1.5 μm from the edge of the particle cross-section are randomly selected near the edge, the average value of the doping element content (wt%) of the areas (areas 1 / 2 / 3) measured by EDS is the surface doping element content; three areas (areas 4 / 5 / 6) with a minimum distance (D4, D5, D6) ≥2 μm from the edge of the particle cross-section are randomly selected near the center of the particle cross-section, and the average value of the doping element content (wt%) of the areas (areas 4 / 5 / 6) measured by EDS is the inner doping element content. According to the doping element distribution uniformity calculation formula, the doping element distribution uniformity of the particle is obtained. Randomly select 3 particle cross-sections, calculate the average value of the doping element distribution uniformity, which is the doping element distribution uniformity of the carbon negative electrode material. The specific measurement results are shown in Tables 1 and 2.

[0229] The doping element distribution uniformity calculation formula is as follows:

[0230] Doping element distribution uniformity = (1 - |Inner layer doping element content - Surface layer doping element content| ÷ Surface layer doping element content) × 100%

[0231] 2. Carbon layer spacing measurement

[0232] XRD was tested by Panalytical X'Pert PRO MPD, and the carbon layer spacing was calculated by the diffraction angle of (002) of XRD, and the specific measurement results are shown in Table 1 and Table 2.

[0233] 3. Specific surface area measurement

[0234] Nitrogen adsorption-desorption test was carried out by using a Micromeritics surface tester at 77K, and the specific surface area was calculated by BET formula, and the specific measurement results are shown in Table 1 and Table 2.

[0235] 4. Median particle size test

[0236] Mastersizer 2000 laser particle size instrument was used for testing, and the steps were as follows: a beaker was used to take a sample of about 0.5g, 1-2mL of anhydrous ethanol was added for dispersion, then water was added for dispersion, the stirring rate was set to 2400-2500r / min, the ultrasonic intensity was 19.5, the shading degree was 5%-15%, the sample refractive index was 2.420, and the dispersant (water) refractive index was 1.330. The ultrasonic test was started, and the average value of four tests was taken, and D50(μm) was read, which was the median particle size.

[0237] Table 1 Performance indicators of carbon negative electrode materials prepared in the application

[0238]

[0239] Table 2 Performance indicators of carbon negative electrode materials prepared in the application

[0240]

[0241] As shown in Table 1, the content of the doping element (phosphorus) of the carbon negative electrode material of Example 1 and the carbon layer spacing are higher than those of Comparative Examples 1 and 2, and the doping element (phosphorus) distribution uniformity is higher than that of Comparative Examples 1 and 2, which shows that carbonization in an oxidizing atmosphere, synchronous pre-carbonization and oxidation under the participation of trace oxygen content can provide rich reaction sites for modification reaction, thereby facilitating the subsequent doping reaction to proceed fully, and being conducive to improving the diffusion depth and distribution uniformity of the doping element in the carbon negative electrode, and promoting the doping of the doping element between the carbon layers. However, pre-carbonization in an inert gas atmosphere and high-temperature heat treatment in an oxygen-containing atmosphere after pre-carbonization in an inert gas atmosphere cannot achieve similar effects.

[0242] As shown in Table 1, the content of the doping element (phosphorus) of the carbon negative electrode material of Example 1 and the carbon layer spacing are greater than those of Comparative Example 3, because the modification of the first precursor in step S2 of Example 1 is beneficial to the full implementation of the doping reaction and the embedding of the doping element into the carbon layer, thereby improving the uniformity of the doping element. The step S2 of Comparative Example 3 is not modified, resulting in that the doping reaction in S3 is mainly doped on the surface of the carbon material, the energy barrier of the doping reaction is high, the uniformity of the doping element distribution is low, the doping amount is small, and the doping element cannot be doped into the carbon layer.

[0243] Figure 6 The distribution of the doping element of the carbon negative electrode material provided by the embodiments of the present application is shown in the schematic diagram as shown in Figure 6 As shown in Table 2, the third carbon negative electrode material of Example 1 and the fourth carbon negative electrode material of Example 8 are compared. Because the first precursor with a large median particle size (12 μm) is obtained by step S1 in the preparation of the fourth carbon negative electrode material of Example 8, and the granulation in step S4 is not performed, the content of the heteroatom of the carbon negative electrode material is high on the outside and low on the inside, and the uniformity of the doping element distribution is relatively low. The third carbon negative electrode of Example 1 of the present application first prepares a first carbon negative electrode material with a small median particle size, and then performs secondary granulation, thereby significantly improving the uniformity of the doping element distribution and the uniformity of the doping element distribution. This shows that under the condition of similar median particle size, the method of first constructing a doped first carbon negative electrode material and then performing secondary granulation to prepare a carbon negative electrode material has a higher uniformity of the doping element distribution than the non-granulated carbon negative electrode material. Therefore, the method of constructing a first carbon negative electrode material and granulation proposed in the present application is beneficial to improving the uniformity of the doping element distribution of the carbon negative electrode, and can compensate for the irregularity of the first carbon negative electrode material, improve the uniformity of the subsequent carbon coating, and reduce the specific surface area through the synergistic effect of granulation and carbon coating, which is beneficial to improving the initial efficiency.

[0244] As shown in Table 1, the content of the doping element (phosphorus) of the carbon negative electrode material of Example 1 and the carbon layer spacing are greater than those of Comparative Example 4, because the doping element of the present application is doped between the carbon layers, resulting in an increase in the carbon layer spacing, while in Comparative Example 4, the intercalation material derived from the modification modifier is removed from the carbon layer of the material at high temperature, and cannot form a carbon material with increased carbon layer spacing.

[0245] The difference between Comparative Example 5 and Example 7 is that no reaction additive is added in the modification reaction in S2 of Comparative Example 5. Correspondingly, the content of the doping element, the uniformity of the doping element distribution, and the carbon layer spacing of Example 7 are all higher than those of Comparative Example 5. This shows that it is necessary to effectively perform the modification reaction in S2 by adding a reaction additive.

[0246] 5. Specific capacity and initial efficiency of button cell

[0247] Specific button cell preparation is prepared by a method known in the art: carbon material, conductive agent and binder are mixed in a mass percentage of 91:3:6, adjusted to a solid content of 50% with deionized water, and coated on a copper foil current collector, vacuum dried to prepare a negative electrode sheet;

[0248] The lithium battery button uses lithium sheet as the counter electrode, 1 mol / L LiPF6 / EC+DMC+EMC (v / v=1:1:1) as the electrolyte, Celgrad2400 as the separator, and 2016 button cell shell as the shell. The sodium battery button uses sodium sheet as the counter electrode, 1 mol / L NaPF6 / EC+DMC+EMC (v / v=1:1:1) as the electrolyte, Celgrad2400 as the separator, and 2016 button cell shell as the shell.

[0249] Button test method: the test conditions of specific capacity and first efficiency of the materials obtained in Examples 1-10 and Comparative Examples 1-5 are: tested on the LAND battery test system of Wuhan Jinuo Electronics Co., Ltd., first 0.2C constant current charging to voltage 5mV, then 5mV constant voltage charging to current 3.5*10 -6 A charging cutoff, and then 0.2C discharging, cutoff voltage 1.5V, the test results are shown in Table 2. The specific capacity (mAh / g) is the first discharge capacity divided by the weight of the carbon negative material contained in the negative electrode sheet, the nominal specific capacity of the lithium battery button is 400 mAh / g, and the nominal specific capacity of the sodium battery button is 300 mAh / g. The first efficiency is the ratio of the first discharge capacity to the first charge capacity.

[0250] 6, 18650 type battery 1500 week capacity retention test

[0251] The 18650 type battery is prepared by a method known in the art: the prepared negative electrode material, conductive agent and binder are dispersed in a solvent in a mass percentage of 94:1:5, mixed uniformly, the solid content is controlled at 40%, coated on a copper foil current collector, vacuum dried to prepare a negative electrode sheet; then the NCM523 positive electrode sheet prepared by traditional mature process, 1 mol / L LiPF6 / EC+DMC+EMC (v / v=1:1:1) electrolyte, Celgard2400 separator, shell is assembled into 18650 cylindrical single battery by conventional production process. The energy density and cycle performance are tested on the LAND battery test system of Wuhan Jinuo Electronics Co., Ltd.

[0252] 1500 week capacity retention test method: 18650 battery is used, 3C / 3C is used for charge and discharge test, 1500 cycles of constant current charge and discharge are carried out at voltage 2.0-4.2V, the discharge capacity of the 1500th week is divided by the discharge capacity of the first week, and the cycle 1500 week capacity retention rate is obtained, the specific test results are shown in Tables 3 and 4.

[0253] Table 3 Performance indicators of batteries prepared from carbon materials prepared in this application

[0254]

[0255]

[0256] Table 4 Performance indicators of batteries prepared from carbon materials prepared in this application

[0257]

[0258] As shown in Table 3, the specific capacity, initial efficiency and 1500-cycle retention rate of the button-type lithium battery and button-type sodium battery of the carbon negative electrode material of Example 1 are all higher than those of Comparative Example 1 and Comparative Example 2, indicating that the simultaneous step S1 (pre-carbonization + oxidation) of the negative electrode material preparation method provided in the present application is beneficial to increasing the provision of doping reaction sites, promoting the full progress of the post-reaction, and improving the uniformity of the distribution of the doping elements within the carbon negative electrode material. The performance is better than the non-oxidized sample in step S1 (Comparative Example 1) and the sample that is pre-carbonized and oxidized in steps (Comparative Example 2).

[0259] As shown in Tables 3 and 4, the button-type lithium battery specific capacity (1.5V capacity, 0.8V capacity), lithium battery initial efficiency, sodium battery specific capacity, and sodium battery initial efficiency of the carbon negative electrode material in Example 1 are significantly higher than those in Comparative Example 3, indicating that the modification treatment of the first precursor in step S2 is beneficial to the characteristics of doping elements to enhance the capacity performance of carbon materials. Figure 7 The first charge and discharge curve of the carbon negative electrode material provided in the embodiment of the present application is shown in FIG. Figure 7 As shown, the capacity of the third carbon negative electrode material in Example 1 is significantly higher than that of Comparative Example 3 and Comparative Example 4 below 0.8V, and the capacity above 0.8V is less than that of Comparative Example 3 and Comparative Example 4, indicating that the doping method of the present application (intercalation of doped elements between carbon layers) mainly improves the available capacity (below 0.8V), while the conventional doping method (direct mixing and heat treatment of pre-carbonized material and doping source) mainly improves the harmful capacity (above 0.8V).

[0260] As shown in Table 3, the first efficiency of the button-type lithium battery and sodium battery of the carbon negative electrode material of Example 1 is significantly higher than that of Comparative Example 4, indicating that doping with carbon interlayer doping elements can significantly improve the capacity and first efficiency of carbon materials.

[0261] As shown in Table 3, the carbon negative electrode material of Examples 1-5 and Comparative Examples 1-4 has higher doping element distribution uniformity, lower specific surface area, and significantly higher first efficiency of the lithium battery, capacity of the sodium battery, first efficiency of the sodium battery, and 1500-week cycle retention rate than the first carbon negative electrode material. This indicates that the granulation modification can improve the doping element distribution uniformity, reduce the expansion rate of the carbon negative electrode material during charging and discharging, and improve the cycle performance of the carbon negative electrode material. In addition, the granulation combined with carbon coating reduces the contact between the doping elements and the electrolyte, further improving the cycle performance of the carbon negative electrode material.

[0262] As shown in Table 4, the carbon negative electrode material of Example 1 has significantly higher specific capacity of the lithium battery (1.5V capacity, 0.8V capacity), first efficiency of the lithium battery, capacity of the sodium battery, first efficiency of the sodium battery, and 1500-week cycle retention rate than Example 8, which indicates that the method of constructing the first carbon negative electrode material and granulation proposed in the present application can maximize the effect of doping elements on improving the capacity performance of the carbon negative electrode material by improving the doping uniformity of the carbon negative electrode material, and can reduce the charging and discharging expansion rate of the carbon material, thereby improving the cycle performance. The specific surface area of Example 1 is smaller than that of Example 9, and the first efficiency and cycle performance are higher than those of the latter. This is because the specific surface area is smaller than that of the latter, and the irreversible capacity corresponding to the formation of SEI film is smaller than that of the latter. The cycle performance of Example 1 is better than that of Example 9, which indicates that carbon coating is beneficial to reducing the contact between the electrolyte and the doping elements of the carbon negative electrode, reducing the electrochemical side reaction, and thereby improving the cycle performance.

[0263] The specific capacity of the lithium battery (1.5V capacity, 0.8V capacity), first efficiency of the lithium battery, capacity of the sodium battery, first efficiency of the sodium battery, and 1500-week cycle retention rate of the first carbon negative electrode material and the third carbon negative electrode material of Example 7 are significantly higher than those of the first carbon negative electrode material and the third carbon negative electrode material of Comparative Example 5, which indicates that the reaction additive is necessary for the effective modification reaction in S2.

[0264] The carbon negative electrode material, the preparation method and the application thereof provided in the present application are described in detail above, and the principles and implementation modes of the present application are described by applying specific examples. The above examples are only used to help understand the method and the core idea thereof; meanwhile, for those skilled in the art, the specific implementation modes and application ranges can be changed according to the idea of the present application, and the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method for preparing a carbon negative electrode material, characterized in that: The steps include: Under the action of a mixed gas, a raw material containing a carbon source is pre-carbonized to obtain a porous first precursor with oxygen-rich carbon layers; wherein the mixed gas includes a protective gas and an oxidizing gas, and the content of the oxidizing gas in the mixed gas is 0.1wt%-2wt%; The reaction temperature of the pre-carbonization is 300°C-800°C; In a protective gas atmosphere, the first precursor is subjected to a modification reaction with a modification modifier, and the product obtained after the modification reaction is subjected to a first purification treatment to obtain a second precursor containing intercalants between carbon layers; the modification modifier is a halogen and its compound, and the halogen and its compound include at least one of aluminum chloride, ferric chloride, ferric bromide, zinc chloride, zinc bromide, iodine, chlorine water, bromine water, iodine water and liquid bromine; or, the modification modifier includes a reaction additive and an alkali metal salt and / or an alkali metal oxide, and the reaction additive includes at least one of glucose, fructose, sucrose, polystyrene, polyvinyl chloride, polyvinyl alcohol, phenolic resin, melamine resin, furfural resin, urea-formaldehyde resin and asphalt; the mass ratio of the first precursor to the modification modifier is 70-99:1-30, and the reaction temperature of the modification reaction is 200°C-800°C; and In a protective gas atmosphere, a second precursor containing intercalants between the carbon layers is subjected to a doping reaction with a dopant, and the product obtained after the doping reaction is subjected to a second purification treatment to obtain the carbon negative electrode material; the mass ratio of the second precursor to the dopant is 70-99:1-30; the dopant includes at least one of a boron source, a nitrogen source, a phosphorus source and a sulfur source; the reaction temperature of the doping reaction is 800°C-1300°C; and the purification treatment is carried out in an acidic reagent.

2. The preparation method according to claim 1, characterized in that The method includes at least one of the following features (1) to (6): (1) The oxidizing gas includes at least one of air, oxygen, ozone, chlorine, water vapor, carbon dioxide and carbon monoxide; (2) The protective gas includes at least one of nitrogen, argon, neon, helium, xenon and krypton; (3) The carbon source comprises at least one of almond shells, coconut shells, walnut shells, date shells, peach shells, rice husks, peanut shells, melon seed shells, pistachio shells, macadamia shells, hazelnut shells, straw, wood chips, distiller's grains, starch, sucrose, glucose, phenolic resin, epoxy resin, melamine resin, furfural resin, urea-formaldehyde resin, asphalt, petroleum coke, needle coke, mesocarbon microbeads, and anthracite; (4) The raw material containing a carbon source also includes a curing agent; (5) The raw material containing a carbon source also includes a curing agent, and the mass ratio of the carbon source to the curing agent is 5-95:95-5; (6) The raw materials containing a carbon source also include a curing agent, and the curing agent includes at least one of melamine, hexamethylenetetramine, p-benzaldehyde, ammonium chloride, ammonium bromide, ammonium fluoride, ammonium iodide, ammonium sulfide, ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfate, ammonium hydrogen sulfate, ammonium carbonate, ammonium hydrogen carbonate, ammonium oxalate and ammonium acetate; (6) The reaction time of the pre-carbonization is 0.1h-24h.

3. The preparation method according to claim 1, wherein The reaction time of the modification reaction is 0.1h-24h.

4. The preparation method according to claim 1, characterized in that The method includes at least one of the following features (1) to (2): (1) The mass ratio of the reaction additive to the alkali metal salt and / or alkali metal oxide is 1:0.5-5; (2) The alkali metal salt and / or alkali metal oxide includes at least one of lithium oxide, lithium carbonate, lithium acetate, lithium oxalate, sodium oxide, sodium acetate, sodium oxalate, sodium peroxide, sodium carbonate, sodium bicarbonate, magnesium oxide, magnesium carbonate, potassium oxide, potassium carbonate and potassium bicarbonate.

5. The preparation method according to claim 1, characterized in that The method includes at least one of the following features (1) to (6): (1) The boron source includes at least one of boric acid, borax, boron trioxide, sodium borohydride, sodium borate, calcium borate, zinc borate, magnesium borate, iron borate, titanium boride and sodium tetraphenylborate; (2) The phosphorus source includes at least one of phosphorus trichloride, phosphorus pentoxide, triammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, phosphate ester, red phosphorus and black phosphorus; (3) The nitrogen source includes at least one of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acid and ammonium bicarbonate; (4) The sulfur source includes at least one of sulfur powder, thiourea, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate and cysteine; (5) The reaction time of the doping reaction is 0.1h-24h; (6) The acidic reagent includes at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, acetic acid, oxalic acid, benzoic acid, hydrosulfuric acid, hydrobromic acid and hydroiodic acid.

6. The preparation method according to claim 1, characterized in that The method further comprises the steps of performing carbon coating on the surface of the carbon negative electrode material or performing carbon coating on the surface of the carbon negative electrode material after secondary granulation.

7. The preparation method according to claim 6, characterized in that The method includes at least one of the following features (1) to (4): (1) The carbon coating method includes at least one of solid phase coating, liquid phase coating, VC heating coating and gas phase coating; (2) The carbon coating method includes at least one of solid phase coating, liquid phase coating, VC heating coating and gas phase coating, and the coated carbon source of the solid phase coating, liquid phase coating and VC heating coating includes at least one of asphalt, sucrose, glucose, phenolic resin, epoxy resin, melamine resin, furfural resin and urea-formaldehyde resin; (3) The carbon coating method includes at least one of solid phase coating, liquid phase coating, VC heating coating and gas phase coating, and the carbon source of the gas phase coating includes at least one of ethanol, methane, ethane, propane, acetone, ethylene, acetylene, benzene, toluene and xylene; (4) The secondary granulation method includes spray drying granulation or VC heating granulation.

8. A carbon negative electrode material prepared according to the method for preparing a carbon negative electrode material according to any one of claims 1 to 7, characterized in that: The carbon negative electrode material includes a carbon matrix, wherein the carbon layers of the carbon matrix contain doping elements, and the doping elements have a distribution uniformity greater than or equal to 35%; The doping element distribution uniformity = (1-|inner layer doping element content-surface layer doping element content|÷surface layer doping element content) × 100%; The doping element includes at least one of boron, nitrogen, phosphorus and sulfur.

9. The carbon negative electrode material according to claim 8, characterized in that The carbon negative electrode material includes at least one of the following features (1) to (7): (1) The median particle size of the carbon negative electrode material is 1 μm-40 μm; (2) The specific surface area of ​​the carbon negative electrode material is 0.5m 2 / g-300m 2 / g; (3) In the carbon negative electrode material, the content of the doping element is 0.05wt%-12wt%; (4) The carbon matrix has a carbon interlayer spacing of 0.35 nm to 0.44 nm; (5) In the carbon negative electrode material, the doping element distribution uniformity is greater than or equal to 50%; (6) The carbon negative electrode material further includes a carbon coating layer formed on the surface of the carbon substrate; (7) The carbon negative electrode material further includes a carbon coating layer formed on the surface of the carbon substrate, and the thickness of the carbon coating layer is 0 μm-5 μm.

10. An application of a carbon negative electrode material, characterized in that: The carbon negative electrode material according to claim 8 or 9 or the carbon negative electrode material prepared by the preparation method according to any one of claims 1 to 7 is applied to a battery.

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