Preparation method of negative electrode material, prepared negative electrode material and application thereof

Abstract

The application provides a preparation method of a negative electrode material, the prepared negative electrode material and an application thereof. The preparation method comprises the following steps: firstly, an organic carbon source is contacted with an activator for activation treatment, and after the treatment, a first material is obtained through washing and drying; the first material is subjected to modification treatment in the presence of a modification atmosphere to obtain a second material; a transition metal is introduced into the second material to obtain a third material; the third material is subjected to heat treatment in the presence of a growth atmosphere, and then the negative electrode material is obtained through washing and drying. The problems of poor conductivity, low initial coulombic efficiency and poor cycle performance of the current sodium ion battery negative electrode material are solved.

Description

Technical Field

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

[0002] With the continuous expansion of the new energy market and the increasing demand for sustainable energy, sodium-ion batteries, which are abundant in resources, low in cost, and have excellent overall performance, have attracted widespread attention. They not only show great potential in large-scale energy storage but also have promising future applications in power batteries and portable batteries. Although there are various preparation routes for anode materials, a process route that can achieve industrial-scale production has not yet been determined. Furthermore, batch consistency and stability need to be improved, becoming the main bottlenecks affecting the industrialization and large-scale production of sodium-ion batteries. The research and mass production of high-performance, cost-effective hard carbon anode materials is key to accelerating the industrialization and widespread application of sodium-ion batteries.

[0003] Among the numerous anode materials studied, carbon-based sodium-ion battery anode materials show the greatest promise for industrialization, especially hard carbon materials which possess excellent sodium storage performance. Currently, research focuses primarily on improving the capacity of anode materials, but compared to improving specific capacity, increasing the initial coulombic efficiency of anode materials is far more challenging. During the first charge and discharge cycle, an SEI film forms on the surface of the anode material. An ideal SEI film should possess stable physical and chemical properties, high electronic insulation, and provide channels for rapid insertion and extraction of sodium ions. It should maintain structural stability during cycling, exhibit high density, and suppress reactions such as corrosion and co-intercalation by solvent molecules. However, high-capacity anode materials often have low initial coulombic efficiency. The increase in sodium storage active sites consumes a large number of active ions during the first charge cycle, leading to irreversible chemical reactions and reducing the initial coulombic efficiency.

[0004] Patent CN 114956037 A, when using biomass such as bamboo, pine wood chips, and coconut shells, as well as bituminous coal, as precursors to prepare sodium-ion battery anode materials, achieved a reversible specific capacity of up to 384 mAh / g at a carbonization temperature of 1600–1800℃. However, the highest initial coulombic efficiency was only 89%, failing to achieve a high initial coulombic efficiency while improving specific capacity. Actively seeking carbon-based anode materials and their preparation methods that can balance and improve specific capacity, rate performance, and initial coulombic efficiency, and resolving the limitations of anode materials, is of great significance for the rapid industrialization of sodium-ion batteries. Summary of the Invention

[0005] This invention addresses the problems of poor conductivity, low initial coulombic efficiency, and poor cycle performance of traditional sodium-ion battery anode materials. It proposes an anode material, its preparation method, and its application. By activating and creating pores with an organic carbon source, modifying the pore structure, and then loading a transition metal to grow a heterogeneous carbon layer structure, a sodium-ion battery anode material with good conductivity, high initial coulombic efficiency, and good cycle performance is prepared.

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

[0007] (1) The organic carbon source is contacted with the activator for activation treatment, and then washed and dried to obtain the first material;

[0008] (2) Under the presence of a modifying atmosphere, the first material obtained in step (1) is modified to obtain the second material.

[0009] (3) A transition metal is introduced into the second material obtained in step (2) to obtain a third material;

[0010] (4) The third material obtained in step (3) is heat-treated in the presence of a growth atmosphere, and then washed and dried to obtain the negative electrode material.

[0011] According to some specific implementation methods, the organic carbon source in step (1) can be derived from organic matter that can be carbonized to obtain carbon materials. More specifically, the organic carbon source is selected from one or more of petroleum coke, asphalt, ethylene tar, shale oil, and heavy oil. Preferably, the softening point of the asphalt used is 60–350°C, more preferably 80–250°C; the density of the asphalt is 0.9–1.4 g / cm³. 3 Preferably, it is 0.9–1.2 g / cm³. 3 The type of petroleum coke includes, but is not limited to, needle coke, sponge coke, and pellet coke, preferably needle coke and / or pellet coke. The volatile matter content in the petroleum coke is 1 wt% to 15 wt%, preferably 5 wt% to 10 wt%. The particle size of the petroleum coke is 10 to 500 μm, preferably 20 to 100 μm.

[0012] According to some specific embodiments, the activator in step (1) can be selected from one or more of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates; the activator can be a particulate solid with a particle size of 300 μm to 1 cm. More specifically, the activator in step (1) can be 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.

[0013] According to some specific implementation methods, when the organic carbon source is activated to form pores in step (1), the organic carbon source and the activator need to be mixed evenly. The mixing method can be any of the solid-solid mixing methods such as direct mixing, ball milling, mechanical pulverization, and air jet pulverization. Direct mixing is preferred.

[0014] According to some specific implementation methods, the weight ratio of organic carbon source to activator in step (1) is 1:1 to 1:5, preferably 1:1.5 to 1:4.

[0015] According to some specific implementation methods, before the activation treatment in step (1), the gas in the activation device is usually fully replaced with an inert atmosphere to ensure that there is no oxygen in the activation device and the activation process is carried out under an inert atmosphere.

[0016] According to some specific embodiments, the activation treatment in step (1) is carried out under an inert atmosphere, with a volumetric flow rate of 50–500 mL / min, preferably 100–300 mL / min. The inert atmosphere can be selected from nitrogen and / or inert gases.

[0017] According to some specific implementation methods, the activation treatment temperature in step (1) is 700-1000℃, preferably 750-950℃; the activation treatment time is 20-100min, preferably 20-60min; and the further heating rate is 1-10℃ / min, preferably 3-10℃ / min.

[0018] According to some specific implementation methods, the activation treatment in step (1) preferably further includes a pre-activation treatment, wherein the pre-activation treatment temperature is 200-500℃, preferably 300-480℃; and the pre-activation treatment time is 20-100min, preferably 20-60min. Furthermore, the heating rate is 3-10℃ / min, preferably 5-8℃ / min;

[0019] According to some specific implementation methods, the washing in step (1) includes acid washing and water washing. The acid washing and water washing processes remove residual salts or other compounds generated during the reaction. Acid washing can be performed using an acid solution, which can be one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5wt% to 20wt%, preferably 1wt% to 10wt%. The mass ratio of the acid solution to the solid material is 10:1 to 100:1, preferably 20:1 to 60:1. Water washing is performed using deionized water or ultrapure water. The mass ratio of water to the solid material during water washing is 10:1 to 100:1, preferably 20:1 to 50:1.

[0020] According to some specific implementation methods, the drying temperature in step (1) is 60 to 150°C, preferably 60 to 120°C; and / or the drying time is 1 to 24 hours, preferably 4 to 12 hours.

[0021] According to some specific implementation methods, the first material in step (1) can also be subjected to crushing 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 shape of the crushed first material is spherical with an aspect ratio of less than 2. The particle size D50 of the first material is 6-25 μm, preferably 8-15 μm; the particle size D10 of the first material is 0.5-6 μm, preferably 1-5 μm; and the particle size D90 of the first material is 26-60 μm, preferably 26-40 μm.

[0022] According to some specific implementation methods, before the processing in step (2) is carried out, the air in the reaction device is first replaced with an inert atmosphere. The inert atmosphere can be nitrogen and / or an inert gas, and the inert gas can be one or more of helium, neon, argon, krypton, and xenon.

[0023] According to some specific embodiments, the modifying atmosphere in step (2) includes atmosphere A, atmosphere B, and an optional balance gas. Atmosphere A is selected from one or two of carbon dioxide and water vapor, and atmosphere B is selected from one or more of hydrogen, methane, ethane, ethylene, propylene, and propane. Atmosphere A has a volume percentage of 20%–95%, preferably 30%–90%, and atmosphere B has a volume percentage of 0.1%–40%, preferably 0.5%–30%. The balance gas is nitrogen and / or an inert gas, preferably nitrogen. The balance gas has a volume percentage of 0%–60%.

[0024] According to some specific implementation methods, when the atmosphere A in the modifying atmosphere in step (2) contains both carbon dioxide and water vapor, the volume percentage of carbon dioxide is 30% to 99%, preferably 40% to 90%.

[0025] According to some specific implementation methods, in step (2), by controlling the concentration of carbon dioxide in the modified atmosphere, the carbon material surface micropores can be fully developed through the reaction of C-CO2, resulting in a well-developed microporous structure. The distance between the walls of the micropores is very close, and the pore volume is relatively small, which can complete the adsorption and desorption process of electrolyte ions more quickly during the charging and discharging process, improve the ion transport performance, and thus improve the rate performance of the negative electrode material.

[0026] According to some specific implementation methods, the volumetric flow rate of the modifying atmosphere in step (2) is 100-600 mL / min, preferably 200-500 mL / min.

[0027] According to some specific implementation methods, the modification treatment temperature in step (2) is 700-1000℃, preferably 800-900℃; preferably, the heating rate can be controlled at 1-10℃ / min, preferably 2-8℃ / min. The modification treatment time in step (2) is 10-100min, preferably 20-60min.

[0028] According to some specific implementation methods, the introduction of transition metal into the second material obtained in step (2) in step (3) can be carried out by one or more of the following methods: sol-gel method, equal volume impregnation, excessive impregnation, uniform precipitation method, co-precipitation method, preferably the sol-gel method, and more preferably the operation is carried out under the promotion of stirring, ultrasound, etc.

[0029] According to some specific implementation methods, when the transition metal is introduced into the second material obtained in step (2) in step (3) using the sol-gel method, the specific process is as follows: the transition metal precursor, complexing agent and solvent are mixed evenly, and then the second material is introduced for treatment and dried to obtain the third material.

[0030] According to some specific embodiments, in a preferred embodiment, the transition metal precursor is a transition metal salt, which can be an inorganic salt or an organic salt. Specifically, the transition metal precursor can be selected from one or more of the following: copper nitrate, ferric nitrate, nickel nitrate, cobalt nitrate, copper sulfate, ferric sulfate, ferrous sulfate, nickel sulfate, molybdenum sulfate, copper chloride, ferric chloride, nickel chloride, copper acetate, ferric acetate, and nickel acetate. Preferably, it is selected from one or more of the following: nickel nitrate, ferric nitrate, cobalt nitrate, copper nitrate, ferrous sulfate, nickel acetate, ferric acetate, and copper acetate. The concentration of the transition metal salt is 0.01–0.15 mol / L, preferably 0.02–0.1 mol / L.

[0031] According to some specific implementation methods, in a preferred embodiment, the complexing agent may be selected from one or more of citric acid, maleic acid, oxalic acid, ammonium oxalate, ethanolamine, diethanolamine, triethanolamine, polyvinylpyrrolidone, glucose, and tartaric acid.

[0032] According to some specific implementation methods, in a preferred case, the solvent is one or more of water and low molecular weight alcohol solvents, specifically one or more of water, ethanol, methanol, isopropanol, and n-butanol.

[0033] According to some specific implementation methods, in a preferred case, the mass ratio of the transition metal precursor to the second material is 3:1 to 1:20, and more preferably 2:1 to 1:15.

[0034] According to some specific implementation methods, in a preferred case, the mass ratio of the transition metal precursor to the complexing agent is 3:1 to 1:2, preferably 2:1 to 1:2.

[0035] According to some specific implementation methods, in a preferred case, the second material treatment is carried out under stirring conditions, and the treatment temperature is 35-100°C, preferably 50-90°C.

[0036] According to some specific implementation methods, in a preferred case, after the transition metal precursor, complexing agent and solvent are mixed evenly, the pH of the system is preferably adjusted to 5.5 to 7.5, such as by using ammonia water with a concentration of 15wt% to 30wt%.

[0037] According to some specific implementation methods, in a preferred case, the drying after the introduction of the second material can be carried out by forced air drying and / or vacuum drying, preferably vacuum drying, with a drying temperature of 60-120°C, more preferably 80-100°C, and a drying time of 2-24 hours, more preferably 5-12 hours.

[0038] According to some specific implementation methods, the sol-gel method for loading transition metal salts is beneficial for the uniform loading of transition metals on the outer surface of carbon materials. This not only avoids damaging the porous structure of the carbon but also helps maintain its original channel structure, which is conducive to improving the platform capacity during charge and discharge. During the subsequent formation of the composite heterogeneous carbon layer, the transition metal compounds on the outer layer of the porous carbon undergo thermal decomposition during a carbonization process, and are simultaneously reduced by the porous carbon at high temperatures. This forms uniformly dispersed transition metal micro / nano particles on the porous carbon surface, serving as reactive sites for the composite heterogeneous carbon layer. This facilitates the formation of heterogeneous carbon layer structures such as carbon nanotubes and amorphous carbon, while also contributing to the uniformity and density of the surface heterogeneous carbon layer structure. This reduces electrolyte consumption during charge and discharge, improving the initial coulombic efficiency and cycle performance of the negative electrode material.

[0039] According to some specific implementation methods, the growth atmosphere described in step (4) includes low-carbon hydrocarbons, carbon dioxide, and an inert atmosphere.

[0040] According to some specific embodiments, in a preferred case, the volume proportion of low-carbon hydrocarbons is 1% to 98%, preferably 5% to 25% or 60% to 99%.

[0041] According to some specific implementation methods, in a preferred embodiment, the volume ratio of carbon dioxide is 1% to 20%, preferably 2% to 15%.

[0042] According to some specific implementation methods, in a preferred embodiment, the volume ratio of the inert atmosphere is 1% to 90%, preferably 10% to 85%.

[0043] According to some specific implementation methods, the low-carbon hydrocarbon is further selected from one or more of alkanes, alkenes, aromatics and alkynes from C1 to C10, preferably from any one or more of alkanes, alkenes and aromatics from C1 to C7. Specifically, the low-carbon hydrocarbon can be selected from one or more of methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, benzene vapor and toluene vapor.

[0044] According to some specific implementation methods, the inert atmosphere can be one or more of argon, helium, xenon, and nitrogen, preferably argon.

[0045] According to some specific implementation methods, in step (4), before the heat treatment to grow the heterogeneous carbon layer structure, the gas in the growth device is usually fully replaced with an inert atmosphere (preferably argon) to ensure that there are no other gases in the device.

[0046] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the heat treatment in step (4) can be carried out in a tubular furnace, a fluidized bed reactor, a moving bed reactor, or a rotary kiln, preferably at least one of a tubular furnace or a moving bed reactor.

[0047] As some specific implementation methods, the introduction of carbon dioxide into the mixed gas in step (4) alters the gas composition and reaction kinetics of the reaction system, which helps to form a more stable carbon structure during the carbon-based composite process. Simultaneously, the addition of carbon dioxide increases the number of reactive oxygen species in the system. These reactive oxygen species can react with carbon atoms during vapor deposition, promoting the rearrangement and ordering of carbon atoms, thereby promoting the graphitization process and improving the rate performance and long-cycle performance of the anode material. Furthermore, the addition of carbon dioxide to the growth atmosphere also affects the temperature distribution and heat transfer efficiency during the deposition process. By adjusting the amount of carbon dioxide added, the temperature gradient during the deposition process can be optimized, promoting the graphitization process over a wider temperature range.

[0048] As some specific implementation methods, the heat treatment in step (4) includes two stages: a first stage heat treatment and a second stage heat treatment. A combination of low-temperature and high-temperature control is used to precisely control the carbonization process, thereby further optimizing and regulating the carbon wall structure and pore size distribution of the third material.

[0049] Furthermore, as some specific embodiments, the first stage heat treatment temperature is 700–900°C, preferably 700–850°C; the first stage heat treatment time is 30–150 min, preferably 50–120 min; and the flow rate of the growth atmosphere is 250–500 mL / min, preferably 300–450 mL / min. The first stage heat treatment is carried out at a relatively low temperature, allowing the gaseous carbon source to diffuse on the material surface and undergo a chemical reaction at a slower rate, generating a uniform and continuous carbon precursor layer.

[0050] Furthermore, as some specific embodiments, the second-stage heat treatment temperature is 900–1200°C, preferably 900–1150°C; the heating rate is 1–5°C / min, preferably 1–3°C / min; the second-stage heat treatment time is 20–60 min, preferably 30–50 min. The flow rate of the growth atmosphere is 50–300 mL / min, preferably 80–250 mL / min. The second-stage heat treatment is carried out at a relatively high temperature, where the material coated with the carbon precursor comes into contact with the gaseous carbon source, undergoing high-temperature condensation and dehydrogenation reactions, thereby forming a dense outer carbon layer uniformly coating the material.

[0051] As some specific implementation methods, the second heat treatment temperature is further 100-500°C higher than the first heat treatment temperature, preferably 100-300°C higher.

[0052] As some specific implementation methods, after the heat treatment is completed, the temperature is lowered to room temperature in an inert atmosphere, and the cooling rate can be controlled to be 0.1 to 10 °C / min, preferably 1 to 5 °C / min.

[0053] As some specific implementation methods, the washing in step (4) includes acid washing and water washing. The purpose is to remove the residual transition metal compounds in the reaction through the acid washing and water washing process. Acid washing is carried out using an acid solution. The acid can be one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5wt% to 20wt%, preferably 1wt% to 10wt%. The mass ratio of the acid solution to the solid phase stream is 5:1 to 50:1, preferably 5:1 to 30:1. During water washing, the mass ratio of water to the solid phase stream is 10:1 to 100:1, preferably 20:1 to 50:1.

[0054] As some specific implementation methods, the drying temperature in step (4) is 60–150°C, preferably 60–120°C. The drying time is 1–24 h, preferably 4–12 h.

[0055] A second aspect of the present invention provides a negative electrode material, which is obtained by the preparation method described in the first aspect.

[0056] More preferably, the specific surface area of ​​the negative electrode material is 0–12 m². 2 / g, preferably 0-9m 2 / g.

[0057] More preferably, the surface of the negative electrode material exhibits a densely arranged villous structure, the thickness of which is 10-50 nm, the length of which is 10-30 nm, and the diameter of which is 1-5 nm.

[0058] Further preferred, the negative electrode material contains carbon nanotubes.

[0059] More preferably, the carbon content of the negative electrode material is greater than or equal to 99 wt%, and more preferably greater than or equal to 99.5 wt%.

[0060] The third aspect of the present invention also provides an application of the negative electrode material described in the second aspect in a sodium-ion battery.

[0061] The method for preparing the negative electrode material and the prepared negative electrode material provided by this invention have one or more of the following beneficial effects:

[0062] (1) The negative electrode material provided by the present invention has a core rich in well-developed microporous structure, which is conducive to improving the sodium storage capacity of the negative electrode material. The villous surface structure is conducive to the migration of sodium ions on the surface and the enhancement of the material structure stability. At the same time, it contains carbon nanotubes that can form a three-dimensional conductive network, which can realize efficient electron transport and is conducive to reducing the internal resistance of the battery. It has excellent comprehensive electrochemical performance.

[0063] (2) The preparation method provided by the present invention has mild operating conditions and the maximum reaction temperature does not exceed 1100℃. Compared with the preparation temperature of hard carbon products on the market (above 1400℃), the preparation method provided can significantly reduce energy consumption and save process costs.

[0064] (3) This invention promotes the full development of micropores on the surface of carbon materials by activating pore formation and modifying pore structure, while enhancing the structural stability of porous carbon. Combined with the uniform introduction of transition metals on the outer surface, the two steps are organically combined to effectively enhance the dynamic performance of sodium ion insertion and extraction, and can improve specific capacity, first charge and discharge coulombic efficiency and cycle performance in a balanced manner.

[0065] (4) The negative electrode material provided by the present invention has excellent performance. The first discharge specific capacity at a current density of 0.1C is as high as 300-400mAh / g, the first week coulombic efficiency can reach up to 93%, and the specific capacity retention rate after 200 charge-discharge cycles is up to 82%.

[0066] (5) The raw materials selected in the preparation process of the negative electrode material of the present invention are low cost and widely available, which greatly expands the source of raw materials for the negative electrode and solves the bottleneck problem of raw materials for the negative electrode. While vigorously promoting the industrialization of sodium-ion batteries, the flexible process can provide suitable materials for the needs of different market application scenarios, and the preparation process is simple. Attached Figure Description

[0067] Figure 1 This is a transmission electron microscope (TEM) image of the sample obtained in Example 1.

[0068] Figure 2 This is a scanning electron microscope image of the sample obtained in Example 1.

[0069] Figure 3 This is the adsorption-desorption curve of the sample obtained in Example 1.

[0070] Figure 4 The graph shows the stability test results of the sample obtained in Example 1 after 200 charge-discharge cycles at 0.1C.

[0071] Figure 5 The image shows a scanning electron microscope (SEM) image of the sample obtained in Comparative Example 2. Detailed Implementation

[0072] The embodiments of the present invention will be described in further detail below with reference to examples. These examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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%.

[0078] Unless otherwise specified, all percentages, parts, ratios, etc., mentioned in this instruction manual are based on weight, and pressures are gauge pressures. In this document, room temperature generally refers to 25°C.

[0079] 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.

[0080] 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.

[0081] In this paper, transmission electron microscopy (TEM) images were tested using a JEM-F200 field emission transmission electron microscope from Nippon Electron.

[0082] In this paper, scanning electron microscope (SEM) images were tested using a JSM-7500F scanning electron microscope manufactured by NEC Corporation.

[0083] In this paper, the carbon content was tested using an ELEMENTRAC CS-I elemental analyzer from Germany.

[0084] 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.

[0085] The rate performance test is as follows: Under normal temperature conditions, the coin cells after the first charge and discharge are subjected to constant current charge and discharge tests at 0.1C / 0.1C, 0.5C / 0.5C, 1C / 1C, and 2C / 2C. The rate discharge retention rate is obtained by dividing the 2C specific capacity by the 0.1C specific capacity.

[0086] Cyclic performance testing is conducted as follows: Under normal temperature conditions, the coin cells after their first charge and discharge are subjected to 200 constant current charge and discharge cycles at 0.1C / 0.1C. The cycle discharge retention rate is obtained by dividing the specific capacity after 200 charge and discharge cycles by the specific capacity at 0.1C.

[0087] Example 1

[0088] 38.91 g of needle coke and 85.60 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder 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 250 mL / min for 20 min. The temperature was then raised to 420℃ and held constant for 50 min, followed by a further increase to 900℃ and held constant for 40 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 10 wt% dilute hydrochloric acid at a liquid-to-solid ratio of 25:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 35:1. The resulting filter cake was dried in a forced-air drying oven at 120℃ for 4 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 4.9 μm, 14.8 μm, and 28.4 μm, respectively, which constituted the first material.

[0089] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was raised to 900 °C at a nitrogen flow rate of 200 mL / min. The flow rate was then switched to 400 mL / min to introduce a modifying atmosphere (nitrogen volume percentage of 5%, water vapor volume percentage of 85%, and methane volume percentage of 10%) and reacted for 60 min. The second material was obtained by cooling the nitrogen atmosphere to room temperature.

[0090] Weigh 2.92g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 4.67g of citric acid, and 167mL of deionized water. Stir magnetically until completely dissolved. Adjust the pH to 6.5 with ammonia while stirring continuously. Heat in a 60℃ water bath until the solution becomes a sol. Add 14.6g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a forced-air drying process at 110℃ for 10 hours to obtain the third material.

[0091] The third 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 raised to 880 °C at a nitrogen flow rate of 200 mL / min. The temperature was then switched to a growth atmosphere of 400 mL / min (methane volume percentage 55%, ethane volume percentage 10%, carbon dioxide volume percentage 8%, helium volume percentage 27%). The temperature was maintained at 880 °C for 50 min, and then raised to 980 °C and maintained for 30 min. The fourth material was obtained by cooling the nitrogen atmosphere to room temperature.

[0092] The fourth material was transferred to a flask, washed with 10wt% dilute hydrochloric acid at a liquid-to-solid mass ratio of 25:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 35:1. The resulting filter cake was dried in an 80℃ forced-air drying oven for 6 hours to obtain the negative electrode material.

[0093] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​1.8 m². 2 The carbon material has a villous surface structure and contains carbon nanotubes. Electrochemical performance tests were conducted on it. According to the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 332.78 mAh / g, the reversible specific capacity was 309.95 mAh / g, the first-cycle coulombic efficiency was 93.14%, and the specific capacitance retention rate after 200 charge-discharge cycles was 81.26%.

[0094] Example 2

[0095] 42.06 g of petroleum coke and 168.24 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder 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 300 mL / min for 20 min. The temperature was then raised to 450℃ and held for 40 min, followed by a second activation at 860℃ for 50 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 7 wt% dilute acetic acid at a liquid-to-solid ratio of 35:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 45:1. The resulting filter cake was dried in an 80℃ forced-air drying oven for 6 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 5.1 μm, 14.2 μm, and 29.8 μm, respectively, which constituted the first material.

[0096] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 250 mL / min for 20 min. Then, the temperature was raised to 950 °C at a nitrogen flow rate of 250 mL / min. The flow rate was then switched to 350 mL / min to introduce a modifying atmosphere (5% nitrogen, 90% carbon dioxide, and 5% ethane by volume) and reacted for 40 min. The second material was obtained by cooling the nitrogen atmosphere to room temperature.

[0097] Weigh 1.37g of ferrous sulfate heptahydrate, 2.47g of oxalic acid, and 123mL of solution (deionized water: ethanol = 3:1). Stir magnetically until completely dissolved. Adjust the pH to 7.2 with ammonia while stirring continuously. Heat in an 80℃ water bath until the solution becomes a sol. Add 13.72g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a forced-air drying process at 105℃ for 9 hours to obtain the third material.

[0098] The third material was loaded into a corundum boat and placed in a tube furnace. After replacing the air in the activation furnace with nitrogen at a flow rate of 200 mL / min for 20 min, the temperature was raised to 780 °C at a nitrogen flow rate of 200 mL / min. The temperature was then switched to a growth atmosphere of 350 mL / min (75% methane, 1% acetylene, 2% carbon dioxide, and 22% nitrogen). The temperature was maintained at 780 °C for 100 min, and then raised to 900 °C and maintained for 60 min. The temperature was then lowered to room temperature under a nitrogen atmosphere to obtain the fourth material.

[0099] The fourth material was transferred to a flask, washed with 8% dilute hydrochloric acid at a liquid-to-solid mass ratio of 40:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 40:1. The resulting filter cake was dried in a forced-air drying oven at 102℃ for 9 hours to obtain the negative electrode material.

[0100] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​3.7 m². 2 The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 378.42 mAh / g, the reversible specific capacity was 349.13 mAh / g, the first-cycle coulombic efficiency was 92.26%, and the specific capacitance retention rate after 200 charge-discharge cycles was 82.63%.

[0101] Example 3

[0102] Weigh out 46.32g of petroleum asphalt (softening point 190℃, density 1.12g / cm³). 346.32 g of KOH was pulverized to 30 μm in a pulverizer, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 400 mL / min for 20 min, then the temperature was raised to 480℃ and held constant for 30 min, followed by a further increase to 750℃ and held constant for 60 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 5 wt% dilute sulfuric acid at a liquid-to-solid ratio of 50:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 30:1. The resulting filter cake was dried in a 90℃ forced-air drying oven for 8 h. The particle size distributions (D10, D50, D90) after air-jet pulverization were 3.9 μm, 12.7 μm, and 31.2 μm, respectively, which constituted the first material.

[0103] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 980 °C at a nitrogen flow rate of 300 mL / min. The flow rate was then switched to 200 mL / min to introduce a modifying atmosphere (9.5% nitrogen, 55% water vapor, 35% carbon dioxide, and 0.5% propane) and reacted for 50 min. The reaction was then allowed to cool to room temperature under the nitrogen atmosphere to obtain the second material.

[0104] Weigh 1.05 g of nickel acetate tetrahydrate (Ni(CH3COO)2 4H2O), 1.26 g of diethanolamine, and 211 mL of ethanol. Stir magnetically until completely dissolved. Adjust the pH to 7.0 with ammonia while stirring continuously. Heat in a 50°C water bath until the solution becomes a sol. Add 15.75 g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a forced-air drying process at 120°C for 5 hours to obtain the third material.

[0105] The third 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 150 mL / min for 20 min. Then, the temperature was raised to 700 °C at a nitrogen flow rate of 150 mL / min. The growth atmosphere was then switched to 150 mL / min (methane volume percentage 60%, carbon dioxide volume percentage 15%, argon volume percentage 25%). The temperature was maintained at 700 °C for 150 min, and then raised to 1000 °C and maintained for 45 min. The fourth material was obtained by cooling the nitrogen atmosphere to room temperature.

[0106] The fourth material was transferred to a flask, washed with 5% dilute sulfuric acid at a liquid-to-solid mass ratio of 30:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 30:1. The resulting filter cake was dried in a 95°C forced-air drying oven for 7 hours to obtain the negative electrode material.

[0107] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​6.9 m². 2The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 312.74 mAh / g, the reversible specific capacity was 282.03 mAh / g, the first-cycle coulombic efficiency was 90.18%, and the specific capacitance retention rate after 200 charge-discharge cycles was 81.29%.

[0108] Example 4

[0109] 41.69 g of pellet coke and 125.07 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder was placed in a corundum boat and placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. The temperature was then raised to 400℃ and held at that temperature for 80 min. The temperature was then raised to 800℃ and held at that temperature for 30 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 15 wt% dilute nitric acid at a liquid-to-solid ratio of 20:1, and filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 50:1. The resulting filter cake was dried in a forced-air drying oven at 110℃ for 7 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 3.8 μm, 13.3 μm, and 31.7 μm, respectively, which was the first material.

[0110] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 1150 °C at a nitrogen flow rate of 300 mL / min. The flow rate was then switched to 450 mL / min to introduce a modifying atmosphere (3% nitrogen, 65% carbon dioxide, 20% water vapor, and 2% ethylene) and reacted for 20 min. The reaction was then allowed to cool to room temperature under the nitrogen atmosphere to obtain the second material.

[0111] Weigh out 5.64 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O), 11.28 g of tartaric acid, and 242 mL of methanol. Stir magnetically until completely dissolved. Adjust the pH to 6.8 with ammonia while stirring continuously. Heat in a 70°C water bath until the solution becomes a sol. Add 11.28 g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a 90°C forced-air drying oven for 14 hours to obtain the third material.

[0112] The third material was loaded into a corundum boat and placed in a tube furnace. After replacing the air in the activation furnace with nitrogen at a flow rate of 200 mL / min for 20 min, the temperature was raised to 820 °C at a nitrogen flow rate of 250 mL / min. The growth atmosphere was then switched to 250 mL / min (benzene vapor volume percentage 5%, carbon dioxide volume percentage 12%, nitrogen volume percentage 83%). The temperature was maintained at 820 °C for 100 min, and then raised to 980 °C and maintained for 50 min. The fourth material was obtained by cooling the nitrogen atmosphere to room temperature.

[0113] The fourth material was transferred to a flask, washed with 15wt% dilute nitric acid at a liquid-to-solid mass ratio of 20:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 120℃ forced-air drying oven for 4 hours to obtain the negative electrode material.

[0114] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​5.7 m². 2 The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 356.28 mAh / g, the reversible specific capacity was 326.78 mAh / g, the first-cycle coulombic efficiency was 91.72%, and the specific capacitance retention rate after 200 charge-discharge cycles was 81.06%.

[0115] Example 5

[0116] Weigh out 36.73g of petroleum asphalt (softening point 300℃, density 1.20g / cm³). 3 183.65 g of KOH was pulverized to 30 μm in a pulverizer, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 min. The temperature was then raised to 350℃ and held constant for 60 min, followed by a further increase to 820℃ and held constant for 35 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 8 wt% dilute hydrochloric acid at a liquid-to-solid ratio of 40:1, and then filtered. The filter cake was then washed with ultrapure water at a liquid-to-solid ratio of 40:1. The resulting filter cake was dried in a forced-air drying oven at 102℃ for 9 h. The particle size distributions (D10, D50, D90) after air-jet pulverization were 4.5 μm, 13.7 μm, and 28.9 μm, respectively, which constituted the first material.

[0117] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 1000℃ at a nitrogen flow rate of 300 mL / min. The flow rate was then switched to 300 mL / min to introduce a modifying atmosphere (26% carbon dioxide, 60% water vapor, 8% methane, and 6% hydrogen) and reacted for 45 min. The reaction was then allowed to cool to room temperature under the nitrogen atmosphere to obtain the second material.

[0118] Weigh 7.24g of nickel acetate tetrahydrate (Ni(CH3COO)2 4H2O), 7.24g of triethanolamine, and 291mL of methanol solution (water to methanol volume ratio 5:1). Stir magnetically until completely dissolved. Adjust the pH to 7.4 with ammonia while stirring continuously. Heat in a 90℃ water bath until the solution becomes a sol. Add 7.24g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a forced-air drying process at 108℃ for 10 hours to obtain the third material.

[0119] The third 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 raised to 800 °C at a nitrogen flow rate of 200 mL / min. The temperature was then switched to a growth atmosphere of 200 mL / min (methane volume percentage 65%, ethylene volume percentage 2%, carbon dioxide volume percentage 1%, argon volume percentage 32%). The temperature was maintained at 800 °C for 80 min, and then raised to 950 °C and maintained for 40 min. The fourth material was obtained by cooling the nitrogen atmosphere to room temperature.

[0120] The fourth material was transferred to a flask, washed with 2wt% dilute sulfuric acid at a liquid-to-solid mass ratio of 60:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 50:1. The resulting filter cake was dried in a 110℃ forced-air drying oven for 7 hours to obtain the negative electrode material.

[0121] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​8.1 m². 2 The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 384.69 mAh / g, the reversible specific capacity was 344.37 mAh / g, the first-cycle coulombic efficiency was 89.52%, and the specific capacitance retention rate after 200 charge-discharge cycles was 81.13%.

[0122] Example 6

[0123] Weigh out 43.67g of petroleum asphalt (softening point 230℃, density 1.17g / cm³). 387.34 g of KOH was pulverized to 30 μm in a pulverizer, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 100 mL / min for 40 min. The temperature was then raised to 500℃ and held constant for 20 min, followed by a second activation at 920℃ for 20 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 2 wt% dilute sulfuric acid at a liquid-to-solid ratio of 60:1, and filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 50:1. The resulting filter cake was dried in a 95℃ forced-air drying oven for 7 h. The particle size distributions (D10, D50, D90) after air-jet pulverization were 3.4 μm, 12.6 μm, and 29.3 μm, respectively, which constituted the first material.

[0124] The first material was placed in a carbonization reactor. After replacing the air in the reactor with nitrogen at a flow rate of 300 mL / min for 20 min, the temperature was raised to 920 °C at a nitrogen flow rate of 250 mL / min. Then, a modifying atmosphere (8% nitrogen, 40% water vapor, 40% carbon dioxide, 6% hydrogen, and 6% propylene) was introduced at a flow rate of 250 mL / min and reacted for 30 min. The second material was obtained by cooling the nitrogen atmosphere to room temperature.

[0125] Weigh out 3.64 g of copper acetate monohydrate (Cu(CH3COO)2H2O), 2.80 g of oxalic acid, and 203 mL of alcohol solution (water, ethanol, and isobutanol in a volume ratio of 3:2:1). Stir magnetically until completely dissolved. Adjust the pH to 6.9 with ammonia while stirring continuously. Heat in an 85°C water bath until the solution becomes a sol. Add 10.93 g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a 95°C forced-air drying oven for 12 hours to obtain the third material.

[0126] The third 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 raised to 750 °C at a nitrogen flow rate of 280 mL / min. The growth atmosphere was then switched to 280 mL / min (78% methane, 4% propylene, 3% carbon dioxide, and 15% helium). The temperature was maintained at 750 °C for 120 min, and then raised to 1150 °C and maintained for 20 min. The fourth material was obtained by cooling the nitrogen atmosphere to room temperature.

[0127] The fourth material was transferred to a flask, washed with 7wt% dilute acetic acid at a liquid-to-solid mass ratio of 35:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 45:1. The resulting filter cake was dried in a 90℃ forced-air drying oven for 8 hours to obtain the negative electrode material.

[0128] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​7.7 m². 2 The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 328.61 mAh / g, the reversible specific capacity was 290.20 mAh / g, the first-cycle coulombic efficiency was 88.31%, and the specific capacitance retention rate after 200 charge-discharge cycles was 80.76%.

[0129] Example 7

[0130] 46.69 g of needle coke and 84.04 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder 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 300 mL / min for 20 min. The temperature was then raised to 850 °C and held constant for 40 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 9 wt% dilute acetic acid at a liquid-to-solid ratio of 55:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 50:1. The resulting filter cake was dried in an 80 °C forced-air drying oven for 6 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 4.2 μm, 11.7 μm, and 32.5 μm, respectively, which was the first material.

[0131] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 930 °C at a nitrogen flow rate of 250 mL / min. The temperature was then switched to 500 mL / min to introduce a modifying atmosphere (40% water vapor, 50% nitrogen, and 10% ethylene by volume) and reacted for 30 min. The second material was obtained by cooling the nitrogen atmosphere to room temperature.

[0132] Weigh out 5.91g of ferrous sulfate heptahydrate, 3.69g of citric acid, and 425mL of methanol solution (water to methanol volume ratio of 2:1). Stir magnetically until completely dissolved. Adjust the pH to 7.1 with ammonia while stirring continuously. Heat in a 50℃ water bath until the solution becomes a sol. Add 8.87g of the second material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a forced-air drying process at 80℃ for 18 hours to obtain the third material.

[0133] The third 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 300 mL / min for 20 min. Then, the temperature was raised to 850 °C at a nitrogen flow rate of 300 mL / min. The growth atmosphere was then switched to 300 mL / min (80% methane, 6% carbon dioxide, and 14% nitrogen). The temperature was maintained at 850 °C for 90 min, and then raised to 1050 °C and maintained for 25 min. The fourth material was obtained by cooling the nitrogen atmosphere to room temperature.

[0134] The fourth material was transferred to a flask, washed with 12wt% dilute acetic acid at a liquid-to-solid mass ratio of 30:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 35:1. The resulting filter cake was dried in a forced-air drying oven at 108℃ for 10 hours to obtain the negative electrode material.

[0135] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​6.8 m². 2 The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 316.87 mAh / g, the reversible specific capacity was 284.42 mAh / g, the first-cycle coulombic efficiency was 89.76%, and the specific capacitance retention rate after 200 charge-discharge cycles was 80.81%.

[0136] Comparative Example 1

[0137] 38.91 g of needle coke and 85.60 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder 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 250 mL / min for 20 min. The temperature was then raised to 420℃ and held constant for 50 min, followed by a second activation at 900℃ for 40 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 10 wt% dilute hydrochloric acid at a liquid-to-solid ratio of 25:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 35:1. The resulting filter cake was dried in a forced-air drying oven at 120℃ for 4 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 4.9 μm, 14.8 μm, and 28.4 μm, respectively, which constituted the first material.

[0138] Weigh 2.92g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 4.67g of citric acid, and 167mL of deionized water. Stir magnetically until completely dissolved. Adjust the pH to 6.5 with ammonia while stirring continuously. Heat in a 60℃ water bath until the solution becomes a sol. Add 14.6g of the first material while stirring to ensure full contact between the solid and liquid. Then dehydrate and dry in a forced-air drying process at 110℃ for 10 hours to obtain the third material.

[0139] The third 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 raised to 880 °C at a nitrogen flow rate of 200 mL / min. The flow rate was then switched to a mixed gas (55% methane, 10% ethane, 8% carbon dioxide, and 27% helium) at a flow rate of 400 mL / min. The temperature was maintained at 880 °C for 50 min, and then raised to 980 °C and maintained for 30 min. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain the fourth material.

[0140] The fourth material was transferred to a flask, washed with 10wt% dilute hydrochloric acid at a liquid-to-solid mass ratio of 25:1, filtered, and then washed with ultrapure water at a liquid-to-solid mass ratio of 35:1. The resulting filter cake was dried in an 80℃ forced-air drying oven for 6 hours to obtain the negative electrode material.

[0141] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 10.4 m². 2 The carbon material has a villous surface structure containing carbon nanotubes. Electrochemical performance tests were conducted on it. Based on the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 387.26 mAh / g, the reversible specific capacity was 323.52 mAh / g, the first-cycle coulombic efficiency was 83.54%, and the specific capacitance retention rate after 200 charge-discharge cycles was 78.61%.

[0142] Comparative Example 2

[0143] 38.91 g of needle coke and 85.60 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder was placed in a corundum boat and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 250 mL / min for 20 min. The temperature was then raised to 420℃ and held at that temperature for 50 min, followed by a second activation at 900℃ for 40 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 10 wt% dilute hydrochloric acid at a liquid-to-solid ratio of 25:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 35:1. The resulting filter cake was dried in a forced-air drying oven at 120℃ for 4 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 4.9 μm, 14.8 μm, and 28.4 μm, respectively, which constituted the first material.

[0144] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was raised to 900 °C at a nitrogen flow rate of 200 mL / min. The flow rate was then switched to 400 mL / min to introduce a modifying atmosphere (5% nitrogen, 85% water vapor, and 10% methane by volume) and reacted for 60 min. The second material was obtained by cooling the nitrogen atmosphere to room temperature.

[0145] The second material was loaded into a corundum boat and placed in a tube furnace. After replacing the air in the activation furnace with nitrogen at a flow rate of 200 mL / min for 20 min, the temperature was raised to 880 °C at a nitrogen flow rate of 200 mL / min. The flow rate was then switched to a mixed gas (methane 55% by volume, ethane 10% by volume, carbon dioxide 8% by volume, and helium 27% by volume) at a flow rate of 400 mL / min. The temperature was maintained at 880 °C for 50 min, and then raised to 980 °C and maintained for 30 min. The mixed gas was then turned off, and the temperature was allowed to drop to room temperature under a nitrogen atmosphere to obtain the negative electrode material.

[0146] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 13.5 m². 2 The carbon material has a villous surface structure and does not contain carbon nanotubes. Electrochemical performance tests were conducted on it. According to the first-cycle charge-discharge curve, the initial discharge specific capacity at 0.1C was 319.22 mAh / g, the reversible specific capacity was 262.18 mAh / g, the first-cycle coulombic efficiency was 82.13%, and the specific capacitance retention rate after 200 charge-discharge cycles was 77.64%.

[0147] Comparative Example 3

[0148] 38.91 g of needle coke and 85.60 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder 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 250 mL / min for 20 min. The temperature was then raised to 420℃ and held constant for 50 min, followed by a further increase to 900℃ and held constant for 40 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 10 wt% dilute hydrochloric acid at a liquid-to-solid ratio of 25:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 35:1. The resulting filter cake was dried in a forced-air drying oven at 120℃ for 4 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 4.9 μm, 14.8 μm, and 28.4 μm, respectively, which constituted the first material.

[0149] The first material was placed in a carbonization reactor. The air in the reactor was replaced with nitrogen at a flow rate of 200 mL / min for 20 min. Then, the temperature was raised to 900 °C at a nitrogen flow rate of 200 mL / min. The flow rate was then switched to 400 mL / min to introduce a modifying atmosphere (5% nitrogen, 85% water vapor, and 10% methane by volume) and reacted for 60 min. The negative electrode material was obtained by cooling the nitrogen atmosphere to room temperature.

[0150] The resulting negative electrode material exhibits a specific surface area of ​​1276.37 m² after nitrogen physical adsorption. 2The carbon material has no villous structure on its surface and does not contain carbon nanotubes. Electrochemical performance tests were conducted on it. According to the first-week charge-discharge curve, the first discharge specific capacity at 0.1C was 482.31mAh / g, the reversible specific capacity was 225.34mAh / g, the first-week coulombic efficiency was 46.72%, and the specific capacitance retention rate after 200 charge-discharge cycles was 61.35%.

[0151] Comparative Example 4

[0152] 38.91 g of needle coke and 85.60 g of KOH were weighed and pulverized to 30 μm in a pulverizer. The powder was placed in a corundum boat and placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 250 mL / min for 20 min. The temperature was then raised to 420℃ and held constant for 50 min, followed by a second activation at 900℃ for 40 min. After cooling to room temperature, the activated product was obtained. The activated product was transferred to a flask, washed with 10 wt% dilute hydrochloric acid at a liquid-to-solid ratio of 25:1, and then filtered. The product was then washed with ultrapure water at a liquid-to-solid ratio of 35:1. The resulting filter cake was dried in a forced-air drying oven at 120℃ for 4 h. The particle size distributions (D10, D50, and D90) after air-jet pulverization were 4.9 μm, 14.8 μm, and 28.4 μm, respectively, indicating that it was a negative electrode material.

[0153] The resulting negative electrode material exhibits a specific surface area of ​​1879.32 m² after nitrogen physical adsorption. 2 / g, and its electrochemical performance was tested. According to the first week charge-discharge curve, the first discharge specific capacity at 0.1C was 762.83mAh / g, the reversible specific capacity was 249.52mAh / g, the first week coulombic efficiency was 32.71%, and the specific capacitance retention rate after 200 charge-discharge cycles was 52.34%.

Claims

1. A method for preparing a negative electrode material, the method comprising the following steps: (1) The organic carbon source is contacted with the activator for activation treatment, and then washed and dried to obtain the first material; (2) Under the presence of a modifying atmosphere, the first material obtained in step (1) is modified to obtain the second material; (3) A third material is obtained by introducing a transition metal into the second material obtained in step (2); (4) The third material obtained in step (3) is heat-treated in the presence of a growth atmosphere, and then washed and dried to obtain the negative electrode material.

2. The method for preparing the negative electrode material according to claim 1, characterized in that: The organic carbon source in step (1) comes from organic matter that can be carbonized to obtain carbon materials, and is selected from one or more of petroleum coke, asphalt, ethylene tar, shale oil, and heavy oil.

3. The method for preparing the negative electrode material according to claim 1, characterized in that: The activator in step (1) is selected from one or more of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates; preferably, the activator is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide, and more preferably, one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate.

4. The method for preparing the negative electrode material according to claim 1, characterized in that: The weight ratio of organic carbon source to activator in step (1) is 1:1 to 1:5, preferably 1:1.5 to 1:

4.

5. The method for preparing the negative electrode material according to claim 1, characterized in that: The activation temperature in step (1) is 700-1000℃, preferably 750-950℃.

6. The method for preparing the negative electrode material according to claim 1, characterized in that: The activation process in step (1) also includes a pre-activation process, wherein the pre-activation temperature is 200-500℃, preferably 300-480℃.

7. The method for preparing the negative electrode material according to claim 1, characterized in that: The washing process in step (1) includes acid washing and water washing.

8. The method for preparing the negative electrode material according to claim 1, characterized in that: The first material in step (1) is crushed and shaped. The shape of the crushed first material is spherical with an aspect ratio of less than 2.

9. The method for preparing the negative electrode material according to claim 1, characterized in that: The modifying atmosphere in step (2) includes atmosphere A, atmosphere B and optional balance gas, wherein atmosphere A is selected from one or two of carbon dioxide and water vapor, atmosphere B is selected from one or more of hydrogen, methane, ethane, ethylene, propylene and propane; the balance gas is nitrogen and / or an inert gas, preferably nitrogen.

10. The method for preparing the negative electrode material according to claim 9, characterized in that: The volume percentage of atmosphere A is 20% to 95%, preferably 30% to 90%; the volume percentage of atmosphere B is 0.1% to 40%, preferably 0.5% to 30%.

11. The method for preparing the negative electrode material according to claim 9, characterized in that: When the atmosphere A in the modifying atmosphere in step (2) contains both carbon dioxide and water vapor, the volume percentage of carbon dioxide is 30% to 99%, preferably 40% to 90%.

12. The method for preparing the negative electrode material according to claim 1, characterized in that: The modification treatment temperature in step (2) is 700-1000℃, preferably 800-900℃.

13. The method for preparing the negative electrode material according to claim 1, characterized in that: The introduction of transition metal into the second material obtained in step (2) in step (3) is carried out by one or more of the following methods: sol-gel method, equal volume impregnation, excessive impregnation, uniform precipitation method, and co-precipitation method, preferably the sol-gel method.

14. The method for preparing the negative electrode material according to claim 1 or 13, characterized in that: The process of introducing the transition metal into the second material obtained in step (2) in step (3) using the sol-gel method is as follows: the transition metal precursor, complexing agent and solvent are mixed evenly, and then the second material is introduced and dried to obtain the third material.

15. The method for preparing the negative electrode material according to claim 14, characterized in that: The transition metal precursor is a transition metal salt, which can be an inorganic or organic salt. The transition metal precursor is selected from one or more of the following: copper nitrate, ferric nitrate, nickel nitrate, cobalt nitrate, copper sulfate, ferric sulfate, ferrous sulfate, nickel sulfate, molybdenum sulfate, copper chloride, ferric chloride, nickel chloride, copper acetate, ferric acetate, and nickel acetate. Preferably, it is selected from one or more of the following: nickel nitrate, ferric nitrate, cobalt nitrate, copper nitrate, ferrous sulfate, nickel acetate, ferric acetate, and copper acetate.

16. The method for preparing the negative electrode material according to claim 14, characterized in that: The complexing agent may be selected from one or more of citric acid, maleic acid, oxalic acid, ammonium oxalate, ethanolamine, diethanolamine, triethanolamine, polyvinylpyrrolidone, glucose, and tartaric acid.

17. The method for preparing the negative electrode material according to claim 14, characterized in that: The solvent is one or more of water and low molecular weight alcohol solvents, specifically one or more of water, ethanol, methanol, isopropanol, and n-butanol.

18. The method for preparing the negative electrode material according to claim 14, characterized in that: The mass ratio of the transition metal precursor to the second material is 3:1 to 1:20, preferably 2:1 to 1:15; the mass ratio of the transition metal precursor to the complexing agent is 3:1 to 1:2, preferably 2:1 to 1:

2.

19. The method for preparing the negative electrode material according to claim 14, characterized in that: The second material treatment is carried out under stirring conditions, and the treatment temperature is 35-100℃, preferably 50-90℃.

20. The method for preparing the negative electrode material according to claim 14, characterized in that: After uniformly mixing the transition metal precursor, complexing agent, and solvent, the pH of the system is preferably adjusted to 5.5–7.

5.

21. The method for preparing the negative electrode material according to claim 1, characterized in that: The growth atmosphere described in step (4) includes low-carbon hydrocarbons, carbon dioxide, and an inert atmosphere.

22. The method for preparing the negative electrode material according to claim 21, characterized in that: The volume percentage of low-carbon hydrocarbons is 1% to 98%, preferably 5% to 25% or 60% to 99%.

23. The method for preparing the negative electrode material according to claim 21, characterized in that: In a preferred embodiment, the volume percentage of carbon dioxide is 1% to 20%, more preferably 2% to 15%.

24. The method for preparing the negative electrode material according to claim 21, characterized in that: The low-carbon hydrocarbon is selected from one or more of alkanes, alkenes, aromatics, and alkynes from C1 to C10, preferably from any one or more of alkanes, alkenes, and aromatics from C1 to C7. Specifically, the low-carbon hydrocarbon is selected from one or more of methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, benzene vapor, and toluene vapor.

25. The method for preparing the negative electrode material according to claim 1, characterized in that: The heat treatment described in step (4) includes two heat treatment stages: a first heat treatment stage and a second heat treatment stage. The temperature of the first heat treatment stage is 700-900℃, preferably 700-850℃. The temperature of the second heat treatment stage is 900-1200℃, preferably 900-1150℃.

26. The method for preparing the negative electrode material according to claim 25, characterized in that: The second stage heat treatment temperature is 100–500°C higher than the first stage heat treatment temperature, preferably 100–300°C higher.

27. The method for preparing the negative electrode material according to claim 1, characterized in that: The washing process in step (4) includes acid washing and water washing.

28. A negative electrode material, said negative electrode material being prepared by the preparation method of any one of claims 1-27.

29. The negative electrode material according to claim 28, characterized in that: The specific surface area of ​​the negative electrode material is 0–12 m². 2 / g, preferably 0-9m 2 / g.

30. The negative electrode material according to claim 28, characterized in that: The surface of the negative electrode material exhibits a densely arranged villous structure, the thickness of which is 10–50 nm, the length of which is 10–30 nm, and the diameter of which is 1–5 nm.

31. The negative electrode material according to claim 28, characterized in that: The negative electrode material contains carbon nanotubes.

32. The use of the negative electrode material according to any one of claims 28-31 in a sodium-ion battery.

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