A method for preparing a negative electrode material, a prepared negative electrode material and use thereof

Abstract

The application provides a preparation method of a negative electrode material, a prepared negative electrode material and application thereof, and the preparation method comprises the following steps: (1) obtaining material A by treating an organic carbon source in the presence of an oxygen-containing atmosphere; (2) obtaining material B by activating the material A; (3) mixing the material B with a solution containing a transition metal salt, and then obtaining material C by drying; and (4) obtaining the negative electrode material by growing a heterogeneous carbon layer on the material C. The application also provides a negative electrode material and a sodium ion battery obtained by using the above preparation method. The preparation process of the negative electrode material uses an organic carbon source as a raw material, the pore size distribution of the organic carbon source is accurately shaped by controlling an activation process, and the porous carbon structure is coated with a composite carbon structure in the presence of a transition metal salt, so that the overall electrochemical performance of the negative electrode material is improved.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials technology, and in particular relates to a battery anode material and its preparation method. Background Technology

[0002] The utilization of renewable energy is receiving increasing attention from researchers, and energy storage systems, as supporting facilities for renewable energy utilization, need corresponding development. Sodium-ion batteries are gradually becoming a new choice for energy storage systems due to their advantages such as abundant sodium resources and low cost. Compared with lithium ions, sodium ions have a larger radius and atomic mass, and the standard potential of sodium is about 0.3V higher than that of lithium. This means that under the same conditions, the operating voltage of sodium-ion batteries is 0.3V lower than that of lithium-ion batteries. Therefore, the energy density of sodium-ion batteries may be difficult to reach the level of lithium-ion batteries, making it difficult to apply them to fields with high energy density requirements, such as portable electronic devices and new energy vehicles. However, for large-scale energy storage fields with lower energy density requirements and a greater desire for low cost, sodium-ion batteries show more advantages and are likely to become a rising star in the future energy storage market.

[0003] Traditional lithium-ion battery anodes, such as graphite, have a positive intercalation energy for sodium, resulting in low sodium storage capacity and making them unsuitable for use as sodium-ion batteries. Hard carbon materials, with their larger interlayer spacing and lower potential, stand out among carbon-based anode materials. Due to their excellent sodium storage performance, they are among the most promising materials for industrialization. Traditional biomass-based and resin-based hard carbon materials carbonize precursors at temperatures above 1300℃ to reduce specific surface area and improve first-cycle coulombic efficiency. However, excessively high temperatures degrade both the specific capacity and rate performance of the material. Patent CN 105914371A describes anode materials prepared using phenolic resin as a raw material. The precursor material requires ultra-high temperature treatment above 1500℃ to achieve a relatively high first-cycle coulombic efficiency of 92%, but the specific capacity is only 270 mAh / g. Increasing the carbonization temperature improves the first-cycle coulombic efficiency but reduces the specific capacity. Patent CN 114956037 A selects biomass such as bamboo, pine wood chips, coconut shells, and bituminous coal as precursors to prepare sodium-ion battery anode materials. The carbonization temperature is between 1600 and 1800℃. The reversible specific capacity of the prepared anode material reaches a maximum of 384mAh / g, but the first coulombic efficiency is only 89% at most. While improving the specific capacity, it is impossible to obtain a high first coulombic efficiency.

[0004] Given that existing sodium-ion battery anode materials cannot simultaneously achieve high specific capacity, good rate performance, and high first-cycle coulombic efficiency, there is an urgent need in this field to find a carbon-based anode material and its preparation method that can balance and improve specific capacity, rate performance, and first-cycle coulombic efficiency. Solving the constraints of anode materials is of great significance for the rapid industrialization of sodium-ion batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a negative electrode material, the prepared negative electrode material, and its applications. The preparation process of the negative electrode material uses an organic carbon source as raw material, and precisely shapes its pore size distribution by controlling the activation process. Under the condition of the presence of transition metal salts, the porous carbon structure is coated with a composite carbon structure to improve the overall electrochemical performance of the negative electrode material.

[0006] The first aspect of this invention provides a method for preparing a negative electrode material, comprising the following steps:

[0007] (1) Material A is obtained by treating an organic carbon source in the presence of an oxygen-containing atmosphere;

[0008] (2) Material A is activated in the presence of an activator to obtain material B;

[0009] (3) Mix material B with a solution containing transition metal salts, and then dry it to obtain material C;

[0010] (4) A heterogeneous carbon layer is grown on material C, and then the negative electrode material is obtained after washing and drying.

[0011] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the oxygen-containing atmosphere in step (1) is a mixture of oxygen and an optional inert atmosphere. In a more preferred embodiment, the volume percentage of oxygen in the mixture is 1% to 99%, preferably 5% to 60%. The inert atmosphere can be nitrogen and / or an inert gas, which can be selected from any one or more of helium, neon, argon, krypton, and xenon.

[0012] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the flow rate of the oxygen-containing atmosphere during the treatment process in step (1) is 100-1000 mL / min, preferably 200-600 mL / min.

[0013] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the organic carbon source in step (1) can be any organic material that can be carbonized to obtain a porous structure, including one or more of asphalt, ethylene tar, shale oil, and heavy oil. The asphalt can be coal tar pitch and / or petroleum asphalt; preferably, it is petroleum asphalt.

[0014] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the softening point of the asphalt is 60–350°C, preferably 80–300°C; and the density of the asphalt is 0.9–1.4 g / cm³. 3 The preferred concentration is 0.9–1.2 g / cm³. 3 .

[0015] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, step (1) may further involve introducing a colloid along with an organic carbon source for processing. The colloid is a viscous liquid obtained after four-component separation of vacuum wax oil, appearing as a yellow to dark brown liquid that melts upon heating. Furthermore, the density of the colloid is 0.9–1.2 g / cm³. 3 The preferred density of the gel is 0.95–1.1 g / cm³. 3 The average relative molecular mass of the gum is 500-1200, preferably 700-1000. The gum is an aromatic hydrocarbon compound with a large molecular weight containing elements such as oxygen, nitrogen, and sulfur. It is dissolved in heavy oil in a semi-solid state and has a complex chemical structure. The inventors found that when the gum is introduced into the oxidation treatment of the organic carbon source in step (1), the gum reacts more rapidly in the subsequent activation process because the gum has a smaller carbon-hydrogen ratio (C / H) and a smaller molecular weight than the organic carbon source (such as asphalt). The preferentially generated macromolecular free radicals can act as chain initiators, promoting the condensation reaction of macromolecular free radicals such as asphalt, which is more conducive to the formation of micropores in the subsequent activation process (2).

[0016] In the preferred embodiment, in the above-mentioned method for preparing the negative electrode material, after the introduction of the colloid in the treatment process of step (1), the molecular structure of the two is rearranged and stabilized during the treatment process by adjusting the ratio of organic carbon source (such as asphalt) and colloid, which can form a more compact and stable carbon skeleton, reduce the difference in the reactivity of the carbon structure, and facilitate the concentrated distribution of the pore structure during the activation process in step (2).

[0017] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the mass ratio of organic carbon source to colloid is 1:1 to 20:1, preferably 2:1 to 10:1, based on weight.

[0018] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the processing conditions in step (1) are as follows: the processing temperature is 80-350℃, preferably 180-300℃; the processing time is 1-10h, preferably 1-6h; and in a more preferred embodiment, the processing in step (1) is carried out under stirring conditions.

[0019] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the material A obtained in step (1) is preferably further subjected to pulverization after cooling. The particle size of the pulverized material A is usually 10 μm to 3 cm, preferably 0.3 mm to 2 cm.

[0020] In the preferred embodiment, in the above-mentioned method for preparing anode materials, the bulk phase and surface of material A obtained in step (1) have abundant oxygen-containing functional groups, which is beneficial to enhancing the bonding force between the carbon matrix and the transition metal in step (3), promoting the generation of new catalytic sites, further benefiting the growth and morphology control of the composite carbon layer in step (4), and thus affecting the composition and electrochemical performance of the prepared anode material.

[0021] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the activator in step (2) is an alkaline activator, specifically one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide, preferably one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate. The activator is a particulate solid with a particle size of 300 μm to 1 cm.

[0022] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the ratio between material A and activator in step (2) is 1:0.1 to 1:4, preferably 1:0.7 to 1:2, based on weight.

[0023] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, before activating material A in step (2), an inert atmosphere can generally be used to replace the gas in the activation device to remove the oxygen-containing atmosphere in the activation device and ensure that the activation process is carried out in the presence of an inert atmosphere.

[0024] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the activation treatment in step (2) is carried out under an inert atmosphere, and the volumetric flow rate of the inert atmosphere is 50 to 500 mL / min, preferably 100 to 400 mL / min.

[0025] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the activation conditions in step (2) are generally controlled as follows: the activation temperature is 600–1000℃, preferably 700–900℃; the activation time is 10–100 min, preferably 20–60 min. Furthermore, the heating rate during the activation process is 1–8℃ / min, preferably 1–5℃ / min;

[0026] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the material B obtained after activation treatment in step (2) further needs to be washed and dried. The washing includes acid washing and water washing. The acid washing and water washing processes remove residual alkali metal compounds from the reaction. The acid washing is performed using an acid solution, and the acid is one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5% to 20%, preferably 1% to 10%. The mass ratio of the acid solution to the solid product is 5:1 to 50:1, preferably 5:1 to 30:1. The water washing uses deionized water or ultrapure water. The mass ratio of water to the solid product during water washing is 10:1 to 100:1, preferably 30:1 to 60:1.

[0027] After washing, drying is usually required. Generally, the drying temperature is 60-150℃, preferably 60-120℃; the drying time is 1-24h, preferably 4-12h.

[0028] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the transition metal in the transition metal salt solution in step (3) is selected from one or more of iron, cobalt, nickel, copper, zinc, and manganese, preferably one or more of iron, cobalt, nickel, and copper; the transition metal salt is selected from one or more of copper nitrate, ferric nitrate, nickel nitrate, cobalt nitrate, copper sulfate, ferric sulfate, nickel sulfate, ferrous sulfate, copper chloride, ferric chloride, nickel chloride, copper acetate, ferric acetate, and nickel acetate, preferably one or more of nickel nitrate, ferric nitrate, ferrous sulfate, cobalt nitrate, copper nitrate, nickel acetate, ferric acetate, and copper acetate. The concentration of the transition metal salt solution is 0.01–2 mol / L, preferably 0.05–1 mol / L.

[0029] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the mass ratio of the transition metal salt loading to material B in step (3) is 0.03:1 to 1.5:1, preferably 0.06:1 to 1:1. In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the mixing in step (3) can be performed using at least one of the following methods: equal-volume impregnation, excessive impregnation, ultrasonic impregnation, uniform precipitation, and co-precipitation. Impregnation is preferred, and mixing is more preferably performed by stirring, ultrasound, or other methods to promote the mixing process.

[0030] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the temperature of the mixing process in step (3) is 10-90°C, preferably 20-70°C; and the mixing time is 0.5-24h, preferably 5-18h.

[0031] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the drying temperature in step (3) is 40–90°C, preferably 60–80°C; the drying time is 4–24 h, preferably 8–18 h. Generally, forced air drying or vacuum drying can be used.

[0032] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the material C obtained in step (3) is preferably subjected to pulverization and shaping treatment, which can be achieved by methods such as air jet milling, ball milling, and wet milling. Air jet milling is preferred, and multiple air jet milling is more preferred. The pulverized material C has a spherical shape with an aspect ratio of less than 2.

[0033] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, before growing a heterogeneous carbon layer on the material C in step (4), an inert atmosphere is typically used to fully replace the gas in the reaction device to ensure that no oxygen is present in the device. The reaction device can be at least one of a tubular furnace, a moving bed, a rotary kiln, and preferably at least one of a tubular furnace or a moving bed.

[0034] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the heterogeneous carbon layer growth process on the material C in step (4) is as follows: the material C is treated with a hydrocarbon-containing atmosphere and then washed to obtain the negative electrode material; the hydrocarbon-containing atmosphere includes low-carbon hydrocarbons with 1-10 carbon atoms and an optional inert atmosphere, wherein the number of carbon atoms of the low-carbon hydrocarbons is preferably 1-7; the low-carbon hydrocarbons can be alkanes, alkenes, aromatics, or alkynes; specifically, the low-carbon hydrocarbons can be selected from at least one of methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, benzene vapor, and toluene vapor; the inert atmosphere is nitrogen and / or an inert gas; the volume percentage of low-carbon hydrocarbons in the hydrocarbon-containing atmosphere is 1%-100%, preferably 5%-25% or 60%-100%. The flow rate of the hydrocarbon-containing atmosphere is 100-500 mL / min, preferably 200-400 mL / min.

[0035] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the heterogeneous carbon layer growth temperature in step (4) is 600–1000℃, preferably 700–900℃, and the heterogeneous carbon layer growth time is 30–200 min, preferably 50–150 min. Furthermore, the heating rate can be controlled at 1–20℃ / min, preferably 2–10℃ / min.

[0036] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, after the heterogeneous carbon layer growth reaction in step (4) is completed, the hydrocarbon-containing atmosphere is stopped, and the temperature is lowered to room temperature in an inert atmosphere. Furthermore, the cooling rate can be controlled at 0.1 to 20 °C / min, preferably 1 to 5 °C / min.

[0037] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the pore size distribution of material B obtained after activation of petroleum coke or pitch in step (2) is 0.1–1 nm. More preferably, the pore size distribution of material B exhibits a bimodal distribution between 0.4 and 1 nm.

[0038] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the washing in step (4) includes acid washing and water washing. The acid washing and water washing processes remove the residual transition metal compounds from the reaction. The acid washing is performed using an acid solution, and the acid is one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5% to 20%, preferably 1% to 10%. The mass ratio of the acid solution to the solid product is 5:1 to 50:1, preferably 5:1 to 30:1. The water washing uses deionized water or ultrapure water, and the mass ratio of water to the solid product during water washing is 10:1 to 100:1, preferably 20:1 to 50:1.

[0039] In a preferred embodiment, in the above-mentioned method for preparing the negative electrode material, the drying temperature in step (4) is 60-150°C, preferably 60-120°C; and the drying time is 1-24h, preferably 4-12h.

[0040] A second aspect of the present invention provides a negative electrode material obtained by the above preparation method, the negative electrode material comprising a carbon layer A and a carbon layer B, wherein the carbon layer A is a microporous carbon material, and the carbon layer B comprises carbon nanotubes (CNTs) and amorphous carbon.

[0041] In a preferred embodiment, the specific surface area of ​​the aforementioned negative electrode material is no greater than 15 m². 2 / g, preferably not greater than 10m 2 / g.

[0042] In a preferred embodiment, in the above-mentioned negative electrode material, the pore size of the microporous carbon in the carbon layer A is not greater than 2 nm, preferably 0.4 to 1.5 nm; furthermore, the pore size of the microporous carbon in the carbon layer A exhibits a bimodal distribution, with the pore size concentrated at 0.5 nm and 0.7 nm.

[0043] In a preferred embodiment, the specific surface area of ​​carbon layer A in the aforementioned negative electrode material is 100–3000 m². 2 / g, preferably 500-1800m 2 / g.

[0044] In a preferred embodiment, the pore volume of carbon layer A in the above-mentioned negative electrode material is 0.4–1.0 cm³. 3 / g, preferably 0.5~0.9cm 3 / g.

[0045] In a preferred embodiment, in the above-mentioned negative electrode material, carbon layer B is distributed on the outer surface of carbon layer A, and the two form a core-shell structure, wherein carbon layer A is the core and carbon layer B is the outer shell.

[0046] In a preferred embodiment, the mass ratio of carbon layer A to carbon layer B in the above-mentioned negative electrode material is 100:1 to 100:30, preferably 100:2 to 100:20.

[0047] In a preferred embodiment, the degree of disorder in the carbonaceous structure of the aforementioned anode material increases radially from the outside to the inside.

[0048] In a preferred embodiment, the carbon content in the aforementioned negative electrode material is not less than 99% by weight, preferably not less than 99.5 wt%.

[0049] In the preferred embodiment, the XRD pattern of carbon layer A in the above-mentioned negative electrode material does not show obvious peaks.

[0050] In the preferred embodiment, the XRD spectrum of carbon layer B in the above-mentioned negative electrode material has obvious 002 peak and 100 peak; wherein the 002 peak belongs to the (002) crystal plane of the carbon microcrystalline structure and is a diffraction peak at 23.2° on the abscissa 2θ; the 100 peak is the (100) crystal plane of the carbon microcrystalline structure and is a diffraction peak at 43.2° on the abscissa 2θ.

[0051] In a preferred embodiment, the D10 of the above-mentioned negative electrode material is 0.5 to 6 μm, preferably 1 to 5 μm.

[0052] In a preferred embodiment, the D50 of the above-mentioned negative electrode material is 6-25 μm, preferably 8-15 μm.

[0053] In a preferred embodiment, the D90 of the above-mentioned negative electrode material is 26-60 μm, preferably 26-40 μm.

[0054] A third aspect of the present invention provides a sodium-ion battery, wherein the sodium-ion battery comprises a negative electrode material obtained by the preparation method described in the second aspect of the present invention.

[0055] Compared with the prior art, the beneficial effects of the negative electrode material preparation method, the prepared negative electrode material, and its application provided by the present invention are reflected in one or more of the following aspects:

[0056] 1. The anode material preparation method provided by this invention utilizes low-cost and widely available precursors, significantly expanding the raw material sources for sodium-ion battery anodes and solving the bottleneck problem for the industrialization of sodium-ion batteries. The diverse sources, stable properties, and low cost of the precursors greatly broaden the range of sodium-ion battery anode materials. This ensures the uniformity and stability of the anode material during production and reduces production costs, thus possessing enormous potential and prospects for industrial applications. Furthermore, this method is simple and convenient to operate; product performance can be flexibly controlled simply by adjusting process parameters, making it highly suitable for large-scale industrial production.

[0057] 2. In the preparation method of the anode material provided by this invention, by precisely controlling the composition and ratio of raw materials, combined with optimized co-carbonization and oxidation conditions, and reasonable activation process conditions, pitch-based microporous carbon materials are prepared. The pitch-based microporous carbon materials exhibit unique pore size characteristics, with pore sizes concentrated below 1 nm and showing a bimodal distribution. This pore size distribution characteristic provides a high-performance inner carbon matrix for the heterogeneous carbon layer, which is beneficial for effectively improving the sodium storage capacity of sodium-ion battery anode materials.

[0058] 3. Compared with the preparation process of hard carbon products currently on the market, the preparation method of the present invention has relatively milder operating conditions, with a maximum temperature below 1000℃. Compared with the existing preparation temperature of hard carbon (above 1400℃), the preparation method provided by the present invention can significantly reduce energy consumption and save process costs.

[0059] 4. In the preparation method of the negative electrode material provided by the present invention, based on the activation and pore formation of the raw material precursor, a heterogeneous carbon layer structure is grown on the surface by introducing a transition metal, which can significantly improve the limiting factors of the first-cycle coulombic efficiency. Through the partial graphitization of the carbon wall and the enhancement of the material conductivity, the first-cycle coulombic efficiency and rate charge-discharge performance of the sodium electrode negative electrode material can be significantly improved. The negative electrode material has a current density of up to 300-490 mAh / g at 0.1C, and the first-cycle coulombic efficiency reaches more than 90%. Attached Figure Description

[0060] Figure 1 The pore size distribution and pore volume diagram of the microporous carbon material in carbon layer A of the negative electrode material prepared in Example 1.

[0061] Figure 2 Transmission electron microscopy (TEM) image of carbon layer B (containing carbon nanotubes) of the negative electrode material prepared in Example 1.

[0062] Figure 3 This is a comparison of the adsorption isotherms of carbon layer A and carbon layer B of the negative electrode material prepared in Example 1. Detailed Implementation

[0063] The embodiments of the present invention will be described in further detail below with reference to the examples. These examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0064] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0065] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0066] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0067] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0068] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0069] In the context of this invention, "substantially" means that deviations that are acceptable or considered reasonable to those skilled in the art are permitted, such as deviations within ±5%, ±2%, ±1%, ±0.5%, or ±0.1%.

[0070] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0071] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0072] In the context of this specification, carbonaceous structure refers to substances with different compositions and structural characteristics of carbon, such as layered structure, porous structure, fibrous structure, amorphous structure, tubular structure, spherical structure, etc. Different carbonaceous structures refer to carbon composed of different carbonaceous microcrystals.

[0073] In this paper, the specific surface area and pore size distribution curves of the samples were obtained using nitrogen adsorption-desorption curves on a Micromeritics ASAP 2020 adsorption instrument at an operating temperature of -196℃ (liquid nitrogen temperature). The samples were pretreated for dehydration at 300℃ under nitrogen protection before testing. Specific surface area, pore volume, and pore size distribution were calculated using the BET and DFT methods, respectively.

[0074] In this paper, the Raman analysis of the samples was performed using an HR-800 Raman spectrometer manufactured by HORIBA JobinYvon, France.

[0075] In this paper, transmission electron microscopy (TEM) images were tested using a JEM-F200 field emission transmission electron microscope from Nippon Electron.

[0076] In this paper, the carbon content was tested using an ELEMENTRAC CS-I elemental analyzer from Germany.

[0077] In the embodiments and comparative examples described herein, when assembling coin cells for electrochemical performance testing of the negative electrode material, the current collector of the negative electrode material is copper foil, the additive is Super-P, the binder is PVDF, and the mass ratio of active material, binder, and conductive agent is 92:3:5 to prepare the negative electrode of the sodium-ion battery. Metallic sodium is used as the counter electrode, 1M NaPF6 or NaClO4 EC / DMC (vol 1:1) is used as the electrolyte solution, and Celgard 2400 porous polypropylene membrane is used as the separator. The CR 2032 type coin cell is assembled in an argon-filled glove box for electrochemical performance testing.

[0078] In the context of this specification, the gum is derived from the gum component produced after four-component separation of vacuum-pressed wax oil (boiling range 350–540°C). It is a viscous liquid, ranging in appearance from yellow to dark brown, that melts upon heating, and has a density of 1.02 g / cm³. 3 The average relative molecular mass is 900.

[0079] Example 1

[0080] Weigh out 42.8g of petroleum asphalt (softening point 190℃, density 1.12g / cm³). 3 ), 10.7g of gelatin (density 1.02g / cm³) 3 The mixture was placed in a reactor, and a mixture of oxygen and nitrogen (oxygen volume fraction 25%) was introduced at a rate of 400 mL / min. The temperature was raised to 260°C, and the reaction was carried out for 5 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0081] Weigh 11.6g of the first material and 17.4g of potassium hydroxide, and thoroughly pulverize them in a pulverizer. Place the pulverized material into a corundum boat, put it into an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 300mL / min for 20min. Then, at a nitrogen flow rate of 300mL / min, raise the temperature to 850℃ at a rate of 2℃ / min and maintain the temperature for 30min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 10% dilute hydrochloric acid at a liquid-to-solid mass ratio of 30:1, filter, and wash with ultrapure water at a liquid-to-solid mass ratio of 45:1. Dry the resulting filter cake in a 105℃ forced-air drying oven for 10h to obtain the first material, which is then subjected to air jet milling and particle shaping.

[0082] Weigh 2.91g of nickel nitrate hexahydrate and completely dissolve it in 20mL of water / ethanol (volume ratio 3:2). Add 5.82g of the first material while stirring to ensure full contact between the solid and liquid. Stir and soak at 60℃ for 10h, and then dry in a vacuum drying oven at 70℃ for 12h to obtain the second material.

[0083] The second material was loaded into a corundum boat and placed in a tube furnace. The air in the furnace was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was increased to 800 °C at a nitrogen flow rate of 200 mL / min and a rate of 2 °C / min. A nitrogen-methane mixture (80% methane by volume) was introduced at a rate of 300 mL / min. After a reaction time of 140 min, the nitrogen-methane mixture was turned off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute acetic acid at a liquid-to-solid mass ratio of 20:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 108 °C forced-air drying oven for 7 h to obtain the negative electrode material.

[0084] The resulting carbon-based anode material exhibits a specific surface area of ​​6.9 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 4.8μm, D50 of 12.4μm, and D90 of 28.7μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 1262.84m². 2 / g, the pore volume of carbon layer A is 0.76 g / cm³. 3 The carbon content is 99.6% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 382.61 mAh / g, the reversible specific capacity was 350.78 mAh / g, and the first-cycle coulombic efficiency was 91.68%.

[0085] Example 2

[0086] Weigh out 39.3g of ethylene tar (density 1.02g / cm³ at 20℃). 3 Kinematic viscosity at 40℃ is 10.12 mm. 2 / s), 13.1g of gelatin (density 1.02g / cm³) 3 The mixture was placed in a reaction vessel, and a mixture of oxygen and nitrogen (oxygen volume fraction 45%) was introduced at a rate of 500 mL / min. The temperature was raised to 300°C, and the reaction was carried out for 3 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0087] Weigh 20.8g of the first material and 20.8g of potassium hydroxide, and thoroughly pulverize them in a pulverizer. Place the pulverized material into a corundum boat, put it into an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 400mL / min for 20min. Then, at a nitrogen flow rate of 400mL / min, raise the temperature to 900℃ at a rate of 5℃ / min and maintain the temperature for 20min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 5% dilute sulfuric acid at a liquid-to-solid mass ratio of 20:1, filter, and wash with ultrapure water at a liquid-to-solid mass ratio of 30:1. Dry the resulting filter cake in a 110℃ forced-air drying oven for 8h to obtain the first material, which is then subjected to air jet milling and particle shaping.

[0088] Weigh 6.67g of ferrous sulfate heptahydrate, dissolve it completely in 30mL of water, add 6.67g of the first material while stirring, so that the solid and liquid are fully wetted and contacted, stir and soak at 70℃ for 6h, and then dry in a vacuum drying oven at 60℃ for 18h to obtain the second material.

[0089] The second material was loaded into a corundum boat and placed in a tube furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was increased to 900 °C at a nitrogen flow rate of 200 mL / min and a rate of 10 °C / min. A nitrogen-benzene mixture (benzene vapor volume percentage 5%) was introduced at a rate of 400 mL / min. After a reaction time of 120 min, the nitrogen-benzene mixture was shut off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute hydrochloric acid at a liquid-to-solid mass ratio of 10:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 40:1. The resulting filter cake was dried in a 125 °C forced-air drying oven for 6 h to obtain the negative electrode material.

[0090] The resulting carbon-based anode material exhibits a specific surface area of ​​6.8 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 3.5μm, D50 of 11.8μm, and D90 of 29.2μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 1032.71m². 2 / g, the pore volume of carbon layer A is 0.58 g / cm³. 3The carbon content is 99.5% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 325.73 mAh / g, the reversible specific capacity was 294.49 mAh / g, and the first-cycle coulombic efficiency was 90.41%.

[0091] Example 3

[0092] Weigh out 38.4g of petroleum asphalt (softening point 230℃, density 1.17g / cm³). 3 ), 6.4g of gelatin (density 1.02g / cm³) 3 The mixture was placed in a reactor, and a mixture of oxygen and nitrogen (oxygen volume fraction 15%) was introduced at a rate of 600 mL / min. The temperature was raised to 250°C, and the reaction was carried out for 4 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0093] Weigh 15.1g of the first material and 18.8g of potassium hydroxide, and thoroughly pulverize them in a pulverizer. Place the pulverized material into a corundum boat, put it into an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 200mL / min for 20min. Then, at a nitrogen flow rate of 200mL / min, heat the material to 700℃ at a rate of 1℃ / min and maintain this temperature for 60min. Cool the material to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash it with 10% dilute acetic acid at a liquid-to-solid mass ratio of 50:1, filter it, and wash it with ultrapure water at a liquid-to-solid mass ratio of 60:1. Dry the resulting filter cake in a 90℃ forced-air drying oven for 12h to obtain the first material, which is then subjected to air jet milling and particle shaping.

[0094] Weigh 3.97g of nickel acetate tetrahydrate and completely dissolve it in 16mL of water / ethanol (volume ratio 2:1). Add 5.67g of the first material while stirring to ensure full contact between the solid and liquid. Stir and soak at 50℃ for 12h, and then dry in a vacuum drying oven at 65℃ for 15h to obtain the second material.

[0095] The second material was loaded into a corundum boat and placed in a tube furnace. After activating the furnace by replacing the air with nitrogen at a flow rate of 200 mL / min for 20 min, the temperature was increased to 850 °C at a nitrogen flow rate of 200 mL / min and a rate of 8 °C / min. A nitrogen-methane-ethylene mixture (65% methane and 2% ethylene by volume) was introduced at a rate of 330 mL / min. After a reaction time of 50 min, the nitrogen-methane-ethylene mixture was shut off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute sulfuric acid at a liquid-to-solid mass ratio of 25:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 42:1. The resulting filter cake was dried in a 110 °C forced-air drying oven for 8 h to obtain the negative electrode material.

[0096] The resulting carbon-based anode material exhibits a specific surface area of ​​4.9 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 3.9μm, D50 of 13.5μm, and D90 of 30.5μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 1763.57m². 2 / g, the pore volume of carbon layer A is 0.85g / cm³. 3 The carbon content is 99.4% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 405.71 mAh / g, the reversible specific capacity was 342.87 mAh / g, and the first-cycle coulombic efficiency was 84.51%.

[0097] Example 4

[0098] Weigh out 36.4g of petroleum asphalt (softening point 300℃, density 1.20g / cm³). 3 ), 18.2g of gelatin (density 1.02g / cm³) 3 The mixture was placed in a reaction vessel, and a mixture of oxygen and nitrogen (oxygen volume fraction 5%) was introduced at a rate of 300 mL / min. The temperature was raised to 200°C, and the reaction was carried out for 2 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0099] 19.6g of the first material and 16.3g of potassium hydroxide were weighed and thoroughly pulverized in a pulverizer. The pulverized material was placed in a corundum boat and then placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 280mL / min for 20min. Then, the temperature was increased to 790℃ at a nitrogen flow rate of 280mL / min and maintained at that temperature for 40min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask, washed with 6% dilute hydrochloric acid at a liquid-to-solid mass ratio of 40:1, and then filtered. The product was washed with ultrapure water at a liquid-to-solid mass ratio of 40:1. The resulting filter cake was dried in a 100℃ forced-air drying oven for 8h to obtain the first material, which was then subjected to air jet milling and particle shaping.

[0100] Weigh 2.40g of copper acetate monohydrate and dissolve it completely in 40mL of water. Add 12.0g of the first material while stirring to ensure full contact between the solid and liquid. Stir and soak at 65℃ for 9 hours, and then dry in a vacuum drying oven at 75℃ for 13 hours to obtain the second material.

[0101] The second material was loaded into an alumina boat and placed in a tube furnace. After activating the furnace by replacing the air with nitrogen at a flow rate of 200 mL / min for 20 min, the temperature was increased to 1000 °C at a nitrogen flow rate of 200 mL / min and a rate of 2 °C / min. A helium-methane-ethane mixture (55% methane, 10% ethane by volume) was introduced at a rate of 350 mL / min. After a reaction time of 100 min, the helium-methane-ethane mixture was shut off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 1% dilute acetic acid at a liquid-to-solid mass ratio of 30:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 45:1. The resulting filter cake was dried in a 150 °C forced-air drying oven for 6 h to obtain the negative electrode material.

[0102] The resulting carbon-based anode material exhibits a specific surface area of ​​7.6 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 4.1μm, D50 of 11.9μm, and D90 of 32.6μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 867.93m². 2 / g, the pore volume of carbon layer A is 0.51g / cm³. 3 The carbon content is 99.6% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 304.21 mAh / g, the reversible specific capacity was 260.53 mAh / g, and the first-cycle coulombic efficiency was 85.64%.

[0103] Example 5

[0104] Weigh out 52.0g of petroleum asphalt (softening point 215℃, density 1.14g / cm³). 3 5.2g of gelatinous substance (density 1.02g / cm³) 3 The mixture was placed in a reactor, and a mixture of oxygen and nitrogen (oxygen volume fraction 60%) was introduced at a rate of 200 mL / min. The temperature was raised to 180°C, and the reaction was carried out for 6 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0105] 19.3g of the first material and 13.8g of potassium hydroxide were weighed and thoroughly pulverized in a pulverizer. The pulverized material was placed in a corundum boat and then placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 350mL / min for 20min. Then, the temperature was increased to 830℃ at a nitrogen flow rate of 350mL / min and maintained at that temperature for 35min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask and washed with 12% dilute sulfuric acid at a liquid-to-solid mass ratio of 30:1. The mixture was then filtered and washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a forced-air drying oven at 120℃ for 4h to obtain the first material, which was then subjected to air jet milling and particle shaping.

[0106] Weigh 1.46g of cobalt nitrate hexahydrate and completely dissolve it in 50mL of water / ethanol (volume ratio 3:2). Add 24.33g of the first material while stirring to ensure full contact between the solid and liquid. Stir and soak at 75℃ for 8 hours, and then dry in a vacuum drying oven at 80℃ for 8 hours to obtain the second material.

[0107] The second material was loaded into a corundum boat and placed in a tube furnace. After purging the air in the furnace with nitrogen at a flow rate of 200 mL / min for 20 min, the temperature was increased to 950 °C at a nitrogen flow rate of 200 mL / min and a rate of 4 °C / min. A helium-methane-ethylene mixture (75% methane, 1% acetylene by volume) was introduced at a rate of 350 mL / min. After a reaction time of 240 min, the helium-methane-ethylene mixture was shut off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute hydrochloric acid at a liquid-to-solid mass ratio of 20:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 110 °C forced-air drying oven for 9 h to obtain the negative electrode material.

[0108] The resulting carbon-based anode material exhibits a specific surface area of ​​8.2 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 5.0μm, D50 of 14.1μm, and D90 of 31.7μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 1435.92m². 2 / g, the pore volume of carbon layer A is 0.75g / cm³. 3 The carbon content is 99.3% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 394.67 mAh / g, the reversible specific capacity was 348.26 mAh / g, and the first-cycle coulombic efficiency was 88.24%.

[0109] Example 6

[0110] Weigh out 36.5g of petroleum asphalt (softening point 230℃, density 1.17g / cm³). 3 The mixture was placed into a reaction vessel, and a mixture of oxygen and nitrogen (70% oxygen by volume) was introduced at a rate of 350 mL / min. The temperature was raised to 310°C, and the reaction was carried out for 4 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0111] Weigh 8.7g of the first material and 21.75g ​​of potassium hydroxide, and thoroughly pulverize them in a pulverizer. Place the pulverized material into a corundum boat, put it into an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 300mL / min for 20min. Then, at a nitrogen flow rate of 300mL / min, raise the temperature to 910℃ at a rate of 3℃ / min and maintain the temperature for 20min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 5% dilute hydrochloric acid at a liquid-to-solid mass ratio of 50:1, filter, and wash with ultrapure water at a liquid-to-solid mass ratio of 70:1. Dry the resulting filter cake in a 105℃ forced-air drying oven for 10h to obtain the first material, which is then subjected to air jet milling and particle shaping.

[0112] Weigh 2.91g of nickel nitrate hexahydrate and completely dissolve it in 20mL of water / ethanol (volume ratio 3:2). Add 5.82g of the first material while stirring to ensure full contact between the solid and liquid. Stir and soak at 60℃ for 10h, and then dry in a vacuum drying oven at 70℃ for 12h to obtain the second material.

[0113] The second material was loaded into a corundum boat and placed in a tube furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was increased to 800 °C at a nitrogen flow rate of 200 mL / min and a rate of 2 °C / min. Methane was introduced at a flow rate of 200 mL / min, and the reaction was allowed to proceed for 150 min. The nitrogen-methane mixture was then shut off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute acetic acid at a liquid-to-solid mass ratio of 20:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 108 °C forced-air drying oven for 7 h to obtain the negative electrode material.

[0114] The resulting carbon-based anode material exhibits a specific surface area of ​​9.1 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 5.2μm, D50 of 14.9μm, and D90 of 29.6μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 2208.34m². 2 / g, the pore volume of carbon layer A is 0.93 g / cm³. 3The carbon content is 99.6% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 418.27 mAh / g, the reversible specific capacity was 348.17 mAh / g, and the first-cycle coulombic efficiency was 83.24%.

[0115] Comparative Example 1

[0116] Weigh out 42.8g of petroleum asphalt (softening point 190℃, density 1.12g / cm³). 3 ), 10.7g of gelatin (density 1.02g / cm³) 3 The product was loaded into a reaction vessel, nitrogen gas was introduced at a rate of 400 mL / min, the temperature was raised to 260°C, and the reaction was carried out for 5 hours. After the reaction was completed, the product was cooled, removed, and pulverized as the first material.

[0117] Weigh 11.6g of the first material and 17.4g of potassium hydroxide, and thoroughly pulverize them in a pulverizer. Place the pulverized material into a corundum boat, put it into an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 300mL / min for 20min. Then, at a nitrogen flow rate of 300mL / min, raise the temperature to 850℃ at a rate of 2℃ / min and maintain the temperature for 30min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 10% dilute hydrochloric acid at a liquid-to-solid mass ratio of 30:1, filter, and wash with ultrapure water at a liquid-to-solid mass ratio of 45:1. Dry the resulting filter cake in a 105℃ forced-air drying oven for 10h to obtain the first material, which is then subjected to air jet milling and particle shaping.

[0118] Weigh 2.91g of nickel nitrate hexahydrate and completely dissolve it in 20mL of water / ethanol (volume ratio 3:2). Add 5.82g of the first material while stirring to ensure full contact between the solid and liquid. Stir and soak at 60℃ for 10h, and then dry in a vacuum drying oven at 70℃ for 12h to obtain the second material.

[0119] The second material was loaded into a corundum boat and placed in a tube furnace. The air in the furnace was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was increased to 800 °C at a nitrogen flow rate of 200 mL / min and a rate of 2 °C / min. A nitrogen-methane mixture (80% methane by volume) was introduced at a rate of 300 mL / min. After a reaction time of 140 min, the nitrogen-methane mixture was turned off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute acetic acid at a liquid-to-solid mass ratio of 20:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 108 °C forced-air drying oven for 7 h to obtain the negative electrode material.

[0120] The resulting carbon-based anode material exhibits a specific surface area of ​​9.5 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 4.4μm, D50 of 11.6μm, and D90 of 30.7μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 1168.25m². 2 / g, the pore volume of carbon layer A is 0.74 g / cm³. 3 The carbon content is 99.2% by mass, and scanning electron microscopy analysis of its surface morphology revealed the presence of carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 328.76 mAh / g, the reversible specific capacity was 271.59 mAh / g, and the first-cycle coulombic efficiency was 82.61%.

[0121] Comparative Example 2

[0122] Weigh out 42.8g of petroleum asphalt (softening point 190℃, density 1.12g / cm³). 3 ), 10.7g of gelatin (density 1.02g / cm³) 3 The mixture was placed in a reactor, and a mixture of oxygen and nitrogen (oxygen volume fraction 25%) was introduced at a rate of 400 mL / min. The temperature was raised to 260°C, and the reaction was carried out for 5 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0123] Weigh 11.6g of the first material and 17.4g of potassium hydroxide, and thoroughly pulverize them in a pulverizer. Place the pulverized material into a corundum boat, put it into an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 300mL / min for 20min. Then, at a nitrogen flow rate of 300mL / min, raise the temperature to 850℃ at a rate of 2℃ / min and maintain the temperature for 30min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 10% dilute hydrochloric acid at a liquid-to-solid mass ratio of 30:1, filter, and wash with ultrapure water at a liquid-to-solid mass ratio of 45:1. Dry the resulting filter cake in a 105℃ forced-air drying oven for 10h to obtain the first material, which is then subjected to air jet milling and particle shaping.

[0124] The first material was loaded into a corundum boat and placed in a tube furnace. The air in the furnace was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was increased to 800 °C at a nitrogen flow rate of 200 mL / min and a rate of 2 °C / min. A nitrogen-methane mixture (80% methane by volume) was introduced at a rate of 300 mL / min. After a reaction time of 140 min, the nitrogen-methane mixture was turned off, and the mixture was allowed to cool to room temperature under a nitrogen atmosphere to obtain the third material. The third material was transferred to a flask, washed with 5% dilute acetic acid at a liquid-to-solid mass ratio of 20:1, and then filtered. The residue was then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 108 °C forced-air drying oven for 7 h to obtain the negative electrode material.

[0125] The resulting carbon-based anode material exhibits a specific surface area of ​​12.8 m² after nitrogen physical adsorption. 2 / g, the particle size distribution is D10 of 5.6μm, D50 of 12.9μm, and D90 of 34.1μm. The pore size of carbon layer A is concentrated at 0.5nm and 0.7nm, and the specific surface area of ​​carbon layer A is 1262.84m². 2 / g, the pore volume of carbon layer A is 0.76 g / cm³. 3 The carbon content is 98.8% by mass, and scanning electron microscopy analysis of its surface morphology showed that it does not contain carbon nanotubes. Electrochemical performance tests of the negative electrode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 340.69 mAh / g, the reversible specific capacity was 283.15 mAh / g, and the first-cycle coulombic efficiency was 83.11%.

[0126] Comparative Example 3

[0127] Weigh out 42.8g of petroleum asphalt (softening point 190℃, density 1.12g / cm³). 3 ), 10.7g of gelatin (density 1.02g / cm³) 3 The mixture was placed in a reactor, and a mixture of oxygen and nitrogen (oxygen volume fraction 25%) was introduced at a rate of 400 mL / min. The temperature was raised to 260°C, and the reaction was carried out for 5 hours. After the reaction was completed, the mixture was cooled, and the product was removed and pulverized as the first material.

[0128] 11.6g of the first material and 17.4g of potassium hydroxide were weighed and thoroughly pulverized in a pulverizer. The pulverized material was placed in a corundum boat and then placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 300mL / min for 20min. Then, the temperature was increased to 850℃ at a nitrogen flow rate of 300mL / min and maintained at that temperature for 30min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask and washed with 10% dilute hydrochloric acid at a liquid-to-solid mass ratio of 30:1. The mixture was then filtered and washed with ultrapure water at a liquid-to-solid mass ratio of 45:1. The resulting filter cake was dried in a forced-air drying oven at 105℃ for 10h to obtain the first material. This material was then subjected to air jet milling and particle shaping to obtain the negative electrode material.

[0129] The resulting carbon-based anode material exhibits a specific surface area of ​​1262.84 m² after nitrogen physical adsorption. 2 / g, with pore sizes concentrated at 0.5nm and 0.7nm, and a pore volume of 0.76g / cm³. 3 The particle size distribution is D10 = 5.8 μm, D50 = 15.4 μm, and D90 = 35.0 μm, with a carbon content of 99.6% by mass. Scanning electron microscopy analysis of the surface morphology revealed the absence of carbon nanotubes. Electrochemical performance tests of the anode material were conducted using assembled coin half-cells. The initial discharge specific capacity at 0.1C was 379.66 mAh / g, the reversible specific capacity was 200.50 mAh / g, and the first-cycle coulombic efficiency was 52.81%.

Claims

1. A method for preparing a negative electrode material, comprising the following steps: (1) Material A is obtained by treating an organic carbon source in the presence of an oxygen-containing atmosphere; (2) Material A is activated in the presence of an activator to obtain material B; (3) Mix material B with a solution containing transition metal salts, and then dry to obtain material C; (4) A heterogeneous carbon layer is grown on material C, and then the negative electrode material is obtained after washing and drying.

2. The method for preparing the negative electrode material according to claim 1, wherein, The oxygen-containing atmosphere in step (1) is a mixture of oxygen and optional inert atmosphere. The volume percentage of oxygen in the mixture is 1% to 99%, preferably 5% to 60%.

3. The method for preparing the negative electrode material according to claim 1, wherein, The organic carbon source in step (1) is an organic material that can be carbonized to obtain a porous structure, including one or more of asphalt, ethylene tar, shale oil, and heavy oil. The asphalt is coal tar pitch and / or petroleum asphalt; preferably, it is petroleum asphalt.

4. The method for preparing the negative electrode material according to claim 1, wherein, In step (1), the gum and organic carbon source are introduced together for treatment; the mass ratio of organic carbon source to gum is 1:1 to 20:1, preferably 2:1 to 10:1, based on weight.

5. The method for preparing the negative electrode material according to claim 1, wherein, The processing conditions in step (1) are as follows: the processing temperature is 80-350℃, preferably 180-300℃.

6. The method for preparing the negative electrode material according to claim 1, wherein, The material A obtained in step (1) is cooled and then crushed. The particle size of the crushed material A is usually 10 μm to 3 cm, preferably 0.3 mm to 2 cm.

7. The method for preparing the negative electrode material according to claim 1, wherein, The activator in step (2) is an alkaline activator, which is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide, preferably one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate; the ratio between material A and activator in step (2) is 1:0.1 to 1:4 by weight, preferably 1:0.7 to 1:

2.

8. The method for preparing the negative electrode material according to claim 1, wherein, The activation conditions in step (2) are as follows: the activation temperature is 600-1000℃, preferably 700-900℃.

9. The method for preparing the negative electrode material according to claim 1, wherein, After the activation treatment in step (2) is completed, the material B is washed and dried. The washing includes acid washing and water washing. The acid washing is carried out with an acid solution. The acid is one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5% to 20%, preferably 1% to 10%.

10. The method for preparing the negative electrode material according to claim 1, wherein, The transition metal in the solution containing the transition metal salt in step (3) is selected from one or more of iron, cobalt, nickel, copper, zinc, and manganese, preferably one or more of iron, cobalt, nickel, and copper; the transition metal salt is selected from one or more of copper nitrate, ferric nitrate, nickel nitrate, cobalt nitrate, copper sulfate, ferric sulfate, nickel sulfate, ferrous sulfate, copper chloride, ferric chloride, nickel chloride, copper acetate, ferric acetate, and nickel acetate, preferably one or more of nickel nitrate, ferric nitrate, ferrous sulfate, cobalt nitrate, copper nitrate, nickel acetate, ferric acetate, and copper acetate; the concentration of the solution containing the transition metal salt is 0.01 to 2 mol / L, preferably 0.05 to 1 mol / L.

11. The method for preparing the negative electrode material according to claim 1, wherein, In step (3), the mass ratio of the transition metal salt loading to material B is 0.03:1 to 1.5:1, preferably 0.06:1 to 1:

1.

12. The method for preparing the negative electrode material according to claim 1, wherein, The material C obtained in step (3) is crushed and shaped by air jet milling, ball milling, or wet milling, with air jet milling being the preferred method.

13. The method for preparing the negative electrode material according to claim 1, wherein, The heterogeneous carbon layer growth process described in step (4) is as follows: material C is treated with a hydrocarbon atmosphere and then washed to obtain the negative electrode material; the hydrocarbon atmosphere includes low-carbon hydrocarbons with 1-10 carbon atoms and an optional inert atmosphere, wherein the number of carbon atoms of the low-carbon hydrocarbons is preferably 1-7; the low-carbon hydrocarbons are at least one of alkanes, alkenes, aromatics and alkynes.

14. The method for preparing the negative electrode material according to claim 13, wherein, The low-carbon hydrocarbon is selected from at least one of methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, benzene vapor, and toluene vapor; the inert atmosphere is nitrogen and / or an inert gas; the volume percentage of low-carbon hydrocarbon in the hydrocarbon-containing atmosphere is 1% to 100%, preferably 5% to 25% or 60% to 100%.

15. The method for preparing the negative electrode material according to claim 1, wherein, The heterogeneous carbon layer growth temperature in step (4) is 600-1000℃, preferably 700-900℃, and the heterogeneous carbon layer growth time is 30-200min, preferably 50-150min.

16. The method for preparing the negative electrode material according to claim 1, wherein, The washing in step (4) includes acid washing and water washing. The acid washing is carried out using an acid solution, and the acid is one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5% to 20%, preferably 1% to 10%.

17. The method for preparing the negative electrode material according to claim 1, wherein, The drying temperature in step (4) is 60-150°C, preferably 60-120°C.

18. A negative electrode material, said negative electrode material being prepared by the preparation method according to any one of claims 1-17.

19. The negative electrode material according to claim 18, wherein, The negative electrode material includes a carbon layer A and a carbon layer B, wherein carbon layer A is a microporous carbon material and carbon layer B includes carbon nanotubes and amorphous carbon.

20. The negative electrode material according to claim 18, wherein, The specific surface area of ​​the negative electrode material is no more than 15m². 2 / g, preferably not greater than 10m 2 / g.

21. The negative electrode material according to claim 18, wherein, The pore size of the microporous carbon in carbon layer A is no greater than 2 nm, preferably 0.4 to 1.5 nm; the pore size of the microporous carbon in carbon layer A has a bimodal distribution, with the pore size concentrated at 0.5 nm and 0.7 nm.

22. The negative electrode material according to claim 18, wherein, The specific surface area of ​​carbon layer A is 100–3000 m². 2 / g, preferably 500-1800m 2 / g; the pore volume of carbon layer A is 0.4–1.0 cm³. 3 / g, preferably 0.5–0.9 cm 3 / g.

23. The negative electrode material according to claim 18, wherein, No obvious peaks were observed in the XRD pattern of carbon layer A.

24. The negative electrode material according to claim 18, wherein, The XRD pattern of carbon layer B shows obvious 002 and 100 peaks; the 002 peak belongs to the (002) crystal plane of the carbon microcrystalline structure and is a diffraction peak at 23.2° on the abscissa; the 100 peak belongs to the (100) crystal plane of the carbon microcrystalline structure and is a diffraction peak at 43.2° on the abscissa.

25. A sodium-ion battery, the sodium-ion battery comprising the negative electrode material according to any one of claims 18-24.

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