A negative electrode material, a preparation method thereof and a sodium ion battery

Abstract

The application discloses a kind of negative electrode material and its preparation method and sodium ion battery, the preparation method of the negative electrode material includes the following steps: (1) organic carbon source is activated and handled, after activation is completed, first material is obtained by washing and drying;(2) the first material obtained in step (1) is carbonized and handled, and second material is obtained after processing;(3) after the second material obtained in step (2) is carried out on the growth of heterogeneous carbon layer structure, negative electrode material is obtained.There is also provided a kind of negative electrode material obtained by using the above preparation method and sodium ion battery comprising negative electrode material.By high-temperature activation of organic carbon source to form pore, combined with pore modification and heterogeneous structure growth to obtain negative electrode material, the specific capacity and the first week coulomb efficiency can be balanced while improving the rate performance of the negative electrode material.

Description

Technical Field

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

[0002] With the global energy transition and the rapid development of the new energy industry, the demand for lithium-ion batteries has surged, highlighting the growing shortage of lithium resources. Future lithium supply will be insufficient to meet demand. Against this backdrop, sodium-ion batteries, due to their abundant resources, excellent low-temperature performance, resistance to over-discharge, high safety, and environmental friendliness, are considered a beneficial supplement to lithium-ion batteries and have broad application prospects.

[0003] Sodium-ion batteries work on a similar principle to lithium-ion batteries; during charging, the sodium in the battery... + Ions will move to the positive electrode, and during discharge, Na + The ions then return to the negative electrode. Because sodium-ion batteries use inexpensive materials, they have low manufacturing costs and are expected to become an important technology for renewable energy storage. Currently, the negative electrode material is one of the technological bottlenecks in the development of sodium-ion batteries. Carbon-based negative electrode materials have a low sodium intercalation plateau, high capacity, and cycle stability, making them the most promising sodium storage negative electrode materials for industrialization.

[0004] Currently, typical precursors for sodium-based anode materials include biomass and resins. However, biomass suffers from drawbacks such as low carbon yield and poor batch-to-batch stability, while the high cost of resin precursors limits their large-scale application. Patent CN107732240A discloses a method for preparing hard carbon materials using a mixture of pitch and phenolic resin as raw materials. The raw materials are pretreated under high pressure, and the prepared hard carbon material exhibits a maximum specific capacity of 280 mAh / g at 0.1C and an initial coulombic efficiency of 75%, indicating room for improvement in electrochemical performance. Patent CN117293312A discloses a method for preparing hard carbon materials using plant-based, sugar-based, and resin-based carbon sources as precursors, employing a combination of solid-phase pore formation, gas-phase pore formation, and high-temperature sintering. This method achieves high specific capacity and initial coulombic efficiency, but the hard carbon yield is relatively low, and the raw material cost is high. Therefore, how to prepare carbon-based sodium-based anode materials using inexpensive, carbon-rich raw materials is a key challenge currently facing this field.

[0005] Petroleum industry byproducts such as petroleum coke are abundant and inexpensive carbon-rich precursors. Using petroleum-based carbon-rich precursors as raw materials to prepare sodium-ion battery anode materials can achieve high-value utilization of carbon-based materials and expand the sources of precursors for sodium-ion battery anode materials, further reducing raw material costs. Therefore, it is of great significance. Summary of the Invention

[0006] This invention addresses the problem of poor rate performance of traditional hard carbon materials. The core objective is to provide a negative electrode material, its preparation method, and a sodium-ion battery. By activating organic carbon sources at high temperatures to create pores, and combining this with pore modification and heterostructure growth, the negative electrode material can be obtained. While ensuring a balanced improvement in specific capacity and first-cycle coulombic efficiency, the rate performance of the negative electrode material can be significantly improved.

[0007] This invention first discloses a method for preparing a negative electrode material, the method comprising the following steps:

[0008] (1) The organic carbon source is activated in the presence of an activator, and the first material is obtained by washing and drying after activation.

[0009] (2) Carbonize the first material obtained in step (1) to obtain the second material;

[0010] (3) After growing a heterogeneous carbon layer structure on the second material obtained in step (2), the negative electrode material is obtained.

[0011] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the organic carbon source in step (1) can be an organic material that can be carbonized to obtain carbon material, such as various hydrocarbon compounds. More specifically, the organic carbon source can be selected from one or more of petroleum coke, asphalt, ethylene tar, shale oil, and heavy oil.

[0012] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, when the organic carbon source in step (1) is asphalt, preferably, the softening point of the asphalt 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 .

[0013] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, when the organic carbon source in step (1) is petroleum coke, 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. Furthermore, the volatile matter content in the petroleum coke is 1wt% to 15wt%, preferably 5wt% to 10wt%. The particle size of the petroleum coke is 10 to 500 μm, preferably 20 to 100 μm.

[0014] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the specific process of step (1) activating the organic carbon source is to mix the organic carbon source and the activator evenly and then perform activation treatment under activation conditions. The mixing method of the organic carbon source and the activator can be at least one of the mixing methods such as direct mixing, ball milling, mechanical pulverization, and air jet pulverization, with direct mixing being preferred.

[0015] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the activator in step (1) can be selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide, preferably selected from one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate.

[0016] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the activator in step (1) is usually a particulate solid with a particle size of 300 μm to 1 cm.

[0017] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, 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.

[0018] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, before the activation treatment in step (1), the gas in the activation device is usually fully replaced by an inert atmosphere to ensure that there is no oxygen in the activation device. The activation process is carried out under an inert atmosphere, and the volume flow rate of the inert atmosphere is 50 to 500 mL / min, preferably 100 to 300 mL / min.

[0019] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the activation conditions in step (1) are as follows: the activation temperature is 700-1000℃, preferably 750-950℃; the heating rate is preferably controlled at 1-10℃ / min, preferably 3-10℃ / min; the activation time is 20-100min, preferably 20-60min.

[0020] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the activation treatment in step (1) further includes a pre-activation treatment, wherein the pre-activation treatment conditions are as follows: the pre-activation temperature is 200-500℃, preferably 300-450℃; the heating rate is preferably controlled at 3-10℃ / min, preferably 5-8℃ / min; and the pre-activation time is 20-100min, preferably 20-60min.

[0021] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the washing in step (1) includes acid washing and water washing. The acid washing and water washing processes remove residual salts and compounds generated during the reaction. The acid washing is performed using an acid solution, and 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 0.5% to 20%, preferably 1% to 10%. The mass ratio of the acid solution to the solid material is 10:1 to 100:1, preferably 20:1 to 60:1. The water washing is performed using deionized water or ultrapure water. The mass ratio of water to solid material during water washing is 10:1 to 100:1, preferably 20:1 to 50:1.

[0022] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the drying temperature in step (1) is 60-150°C, preferably 60-120°C.

[0023] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the drying time in step (1) is 1 to 24 hours, preferably 4 to 12 hours.

[0024] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the activated product in step (1) is washed and dried to obtain the first material. The first material can preferably also be crushed and shaped, which can be achieved by air jet milling, ball milling, wet milling, etc. Air jet milling is preferred, and multiple air jet milling is even more preferred.

[0025] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the shape of the first material after pulverization is spherical with an aspect ratio of less than 2.

[0026] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the particle size D50 of the first material is 6-25 μm, preferably 8-15 μm.

[0027] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the particle size D10 of the first material is 0.5 to 6 μm, preferably 1 to 5 μm.

[0028] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the particle size D90 of the first material is 26-60 μm, preferably 26-40 μm.

[0029] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the carbonization temperature in step (2) is 900-1800℃, preferably 1000-1400℃; the carbonization time is 0.5-6h, preferably 1-4h; furthermore, the heating rate during the carbonization process can be controlled at 1-20℃ / min, preferably 2-10℃ / min. The carbonization process in step (2) can further modify the pores of the first material, achieving precise control over the proportion of micropores and mesopores and the total pore volume of the material. If the temperature is too low, the short-range ordering process cannot be achieved; if the temperature is too high, a large-area graphitization process will occur. The long-range ordered structure is not conducive to the interlayer insertion and extraction process of sodium ions during the charging and discharging process, resulting in a loss of sodium storage capacity of the negative electrode material. Furthermore, carbonization at the appropriate temperature mentioned in step (2) not only promotes short-range ordering of carbon graphite microcrystals and improves the structural stability of the material, making it less prone to deformation or breakage under external forces or temperature changes, but also improves the rate performance and cycle performance of the material. Simultaneously, the carbon wall structure of the hard carbon material is optimized after carbonization, reducing defect sites and dangling sites, which can reduce irreversible capacity loss during the first charge-discharge process, thereby improving the first coulombic efficiency. Moreover, in the subsequent use of the hard carbon material, the optimized carbon wall structure can reduce the interaction between the material and the electrolyte during charge-discharge, reducing heat release and gas generation, thereby improving battery safety.

[0030] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, after the carbonization process in step (2) is completed, the temperature is lowered to the temperature at which the heterogeneous carbon layer is grown on the surface in step (3), and the cooling rate is 0.5 to 5 °C / min, preferably 1 to 3 °C / min.

[0031] As some specific implementation methods, in the above-mentioned method for preparing anode materials, the specific process of obtaining anode materials by growing a heterogeneous carbon layer structure on the second material obtained in step (2) in step (3) is as follows: the second material obtained in step (2) is heat-treated in the presence of a growth atmosphere.

[0032] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, before growing the heterogeneous carbon layer structure in step (3), the gas in the growth device is usually fully replaced with an inert atmosphere (preferably argon) to ensure that no other gas exists in the device.

[0033] As some specific implementation methods, in the above-mentioned method for preparing anode materials, the growth of heterogeneous carbon layer structure in step (3) can be carried out in a tube furnace, a fluidized bed, a moving bed, or a rotary kiln, preferably at least one of a tube furnace or a moving bed.

[0034] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the growth atmosphere in step (3) includes low-carbon hydrocarbons, carbon dioxide and an inert atmosphere; the inert atmosphere is a balance gas.

[0035] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the volume ratio of low-carbon hydrocarbons is preferably 1% to 98%, more preferably 5% to 25% or 60% to 98%.

[0036] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the volume ratio of carbon dioxide is preferably 1% to 20%, and more preferably 2% to 15%.

[0037] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the volume ratio of inert atmosphere is preferably 1% to 90%, and more preferably 10% to 85%.

[0038] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, 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.

[0039] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the inert atmosphere can be one or more of argon, helium, xenon, and nitrogen, preferably argon.

[0040] As some specific implementation methods, in the above-mentioned methods for preparing anode materials, the introduction of carbon dioxide into the growth atmosphere 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 accelerating the graphitization process and improving the rate performance and long-cycle performance of the anode material. Furthermore, the addition of carbon dioxide 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.

[0041] As some specific implementation methods, in the above-mentioned method for preparing anode materials, the temperature of growing heterogeneous carbon layers on the surface in step (3) is controlled in two stages. A combination of low-temperature and high-temperature control is used to precisely control the carbonization process, thereby achieving further optimization and regulation of the carbon wall structure and pore size distribution of the third material.

[0042] As some specific implementation methods, in the above-mentioned method for preparing anode materials, the specific process of obtaining anode materials by growing a heterogeneous carbon layer structure on the second material obtained in step (2) in step (3) is as follows: the second material obtained in step (2) is subjected to heat treatment under the presence of a growth atmosphere, and the heat treatment includes two stages of heat treatment: a first stage heat treatment and a second stage heat treatment.

[0043] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, 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.

[0044] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, 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 coating 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.

[0045] As some specific implementation methods, in the above-mentioned method for preparing the negative electrode material, the second heat treatment temperature is 100-500°C higher than the first heat treatment temperature, preferably 100-300°C higher.

[0046] As some specific implementation methods, in the above-mentioned method for preparing negative electrode materials, the negative electrode material is obtained after the heat treatment is completed and the material is cooled to room temperature in an inert atmosphere.

[0047] A second aspect of the present invention provides a negative electrode material obtained by the preparation method described in the first aspect.

[0048] As some specific implementation methods, the above-mentioned negative electrode material includes a core and an outer layer, wherein the core is a microporous carbon material and the outer layer is a heterogeneous carbon layer containing carbon nanotubes; wherein the mass ratio of the core to the outer layer is 100:1 to 100:50, preferably 100:5 to 100:20.

[0049] As some specific implementation methods, in the above-mentioned negative electrode materials, the specific surface area of ​​the negative electrode material is 0-12m². 2 / g, preferably 0-9m 2 / g.

[0050] As some specific implementation methods, in the above-mentioned negative electrode materials, the specific surface area of ​​the core is 100-3000 m². 2 / g, preferably 500-1800m 2 / g.

[0051] As some specific implementation methods, in the above-mentioned negative electrode material, the pore size of the microporous carbon material in the core is no greater than 10 nm, preferably no greater than 5 nm; furthermore, the proportion of micropores smaller than 2 nm is greater than 50%, and the pore size exhibits a multi-peak distribution characteristic.

[0052] In some specific implementations, the core pore volume of the aforementioned negative electrode material is 0.6–1.3 cm³. 3 / g, preferably 0.6~1.0cm 3 / g.

[0053] As some specific implementation methods, in the above-mentioned negative electrode material, the carbon content of the negative electrode material is >99%, preferably >99.5%.

[0054] A third aspect of the present invention also provides a sodium-ion battery, the sodium-ion battery comprising the negative electrode material described in the second aspect of the present invention.

[0055] As some specific implementation methods, a sodium-ion battery further includes a negative electrode, a positive electrode, and an electrolyte.

[0056] As some specific implementation methods, the active material of the positive electrode can be selected from one or more of transition metal oxides, sodium polyanionic compounds, and Prussian blue.

[0057] Furthermore, the negative electrode includes a negative electrode active material, a conductive agent, and a binder, wherein the negative electrode active material is the negative electrode material prepared in this invention; the conductive agent is one or more of Super P, graphene, carbon nanotubes, acetylene black, Ketjen black, conductive graphite, KS-6, and carbon fiber VGCF; and the binder is one or more of PVDF (polyvinylidene fluoride), CMC (sodium carboxymethyl cellulose), SBR (styrene-butadiene latex), PTFE (polytetrafluoroethylene), PAA (polyacrylic acid), SA (sodium alginate), and PAN (polyacrylonitrile).

[0058] Furthermore, the electrolyte includes an organic solvent and an electrolyte sodium salt, wherein the organic solvent may be one or more of EC, PC, DMC, DEC, EMC, EA, FEC, and VC; and the electrolyte sodium salt may be one or more of NaClO4, NaPF6, NaBF4, NaFSI (sodium bis(fluorosulfonyl)imide, F2NNaO4S2), and NaTFSI (sodium fluorosulfonyl)imide.

[0059] Compared with the prior art, the beneficial effects of the negative electrode material, its preparation method, and sodium-ion battery provided by this invention are reflected in at least one of the following aspects:

[0060] (1) The present invention selects petroleum-based carbon-rich raw materials, which are low in cost. While realizing the high-value utilization of petroleum-based carbon-rich precursors, it can also prepare high-performance sodium-ion battery anode materials with high tap density.

[0061] (2) In the method for preparing anode material provided by the present invention, the organic combination of activation and carbonization processes realizes the shaping and fine control of the pore structure. At the same time, the carbon wall of the carbon material is partially graphitized to form a short-range ordered graphite microcrystalline structure, 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 sodium battery anode material can be significantly improved.

[0062] (3) In the method for preparing anode materials provided by the present invention, a certain amount of carbon dioxide is added to the growth atmosphere to promote the degree of graphitization in the vapor deposition process by changing the reaction kinetics, introducing active oxygen species and optimizing the temperature distribution in the deposition process, thereby improving the physical and chemical properties of the anode material.

[0063] (4) The sodium-ion battery anode material provided by the present invention has excellent performance, with a current density of more than 300 mAh / g at 0.1C and a first-cycle coulombic efficiency of more than 88%. At the same time, it has excellent rate performance, with a 2C rate discharge retention rate of more than 71%.

[0064] (5) The performance of the product of the present invention can be flexibly adjusted by controlling the process, and can provide suitable raw materials for different market application scenarios. The process is simple and has the potential for industrial scale-up. Attached Figure Description

[0065] Figure 1 This is a pore size distribution diagram of the kernel of the sample in Example 1.

[0066] Figure 2 This is a comparison graph of the adsorption-desorption curves of the samples from Example 1 and Comparative Example 2.

[0067] Figure 3 The first charge-discharge curve of the sample in Example 1 is shown.

[0068] Figure 4 This is a graph showing the rate performance test results of the sample from Example 1. Detailed Implementation

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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%.

[0075] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0076] 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.

[0077] 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.

[0078] In this paper, the carbon content was tested using an ELEMENTRAC CS-I elemental analyzer from Germany.

[0079] 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.

[0080] 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.

[0081] Example 1

[0082] Weigh out 8.72g of pellet coke and 26.16g of potassium hydroxide, pulverize and mix them, and place them in a corundum boat. Place the boat in an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 150mL / min for 20min. Then, at a nitrogen flow rate of 150mL / min, raise the temperature to 400℃ and maintain this temperature for 80min. Next, raise the temperature to 900℃ and maintain this temperature for 40min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 8wt% dilute hydrochloric acid (liquid-solid mass ratio 40:1), filter, wash with ultrapure water (liquid-solid mass ratio 40:1), and dry the resulting filter cake in a 100℃ forced-air drying oven for 9h. After air jet milling, obtain the first material.

[0083] The first material was loaded into a corundum boat and placed in a carbonization furnace. The air in the activation furnace was replaced with argon at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 1200℃ at an argon flow rate of 300 mL / min and carbonized at a constant temperature for 3 h. The temperature was then adjusted to 800℃, and the argon atmosphere was switched to a growth atmosphere (80% methane, 6% carbon dioxide, and 14% argon) at a flow rate of 300 mL / min and maintained for 80 min. Then, the temperature was raised to 950℃ and maintained for 40 min. The atmosphere was then switched to nitrogen, and the material was cooled to room temperature under a nitrogen atmosphere to obtain the negative electrode material.

[0084] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 5.1 m². 2 / g, with micropores smaller than 2nm accounting for 57.8%; electrochemical performance tests were conducted, and based on the first-week charge-discharge curve, the discharge specific capacity at 0.1C was 329.91mAh / g, the reversible specific capacity was 304.28mAh / g, the first-week coulombic efficiency was 92.23%, and the 2C rate retention rate was 75.30%.

[0085] Example 2

[0086] 9.54 g of needle coke and 23.85 g of potassium hydroxide were weighed, pulverized, and mixed. The mixture 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 200 mL / min for 20 min. Then, the temperature was raised to 300 °C and activated at a constant temperature for 20 min at a nitrogen flow rate of 200 mL / min. The temperature was then raised to 750 °C and activated at a constant temperature for 30 min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask, washed with 5 wt% dilute sulfuric acid at a liquid-to-solid mass ratio of 50:1, and filtered. The product was 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 h and then subjected to air jet milling to obtain the first material.

[0087] The first material was loaded into a corundum boat and placed in a carbonization furnace. The air in the activation furnace was replaced with argon at a flow rate of 250 mL / min for 20 min. Then, the temperature was raised to 1600℃ at an argon flow rate of 250 mL / min and carbonized at a constant temperature for 2 h. The temperature was then adjusted to 820℃, and the argon atmosphere was switched to a growth atmosphere at a flow rate of 250 mL / min (5% benzene vapor, 12% carbon dioxide, and 83% argon). This atmosphere was maintained for 100 min, and the temperature was raised to 980℃ and maintained for 50 min. The atmosphere was then switched to nitrogen, and the material was cooled to room temperature under nitrogen atmosphere to obtain the negative electrode material.

[0088] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 5.1 m². 2 / g, with micropores smaller than 2nm accounting for 84.2%; electrochemical performance tests were conducted, and based on the first-week charge-discharge curve, the discharge specific capacity at 0.1C was 329.91mAh / g, the reversible specific capacity was 304.28mAh / g, the first-week coulombic efficiency was 92.23%, and the 2C rate retention rate was 75.30%.

[0089] Example 3

[0090] Weigh out 6.34g of petroleum coke and 25.36g of potassium hydroxide, pulverize and mix them, and place them in a corundum boat. Put the boat into an activation furnace, replace the air in the furnace with nitrogen at a flow rate of 400mL / min for 20min, then heat to 450℃ at a nitrogen flow rate of 400mL / min and maintain the temperature for 60min. Then heat to 950℃ and maintain the temperature for 50min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 15wt% dilute nitric acid at a liquid-to-solid mass ratio of 20:1, filter, wash with ultrapure water at a liquid-to-solid mass ratio of 50:1, dry the resulting filter cake in a 120℃ forced-air drying oven for 4h, and then perform air jet milling to obtain the first material.

[0091] The first material was loaded into a corundum boat and placed in a carbonization furnace. The air in the activation furnace was replaced with argon at a flow rate of 200 mL / min for 20 min. Then, the temperature was raised to 1400℃ at an argon flow rate of 200 mL / min and carbonized at a constant temperature for 4 h. The temperature was then adjusted to 700℃, and the argon atmosphere was switched to a growth atmosphere at a flow rate of 200 mL / min (methane volume percentage 65%, ethylene volume percentage 2%, carbon dioxide volume percentage 1%, and argon volume percentage 32%). This atmosphere was maintained for 150 min, and the temperature was raised to 1000℃ and maintained for 45 min. The atmosphere was then switched to nitrogen, and the temperature was lowered to room temperature under a nitrogen atmosphere to obtain the negative electrode material.

[0092] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​5.5 m². 2 / g, with micropores smaller than 2nm accounting for 55.7%; electrochemical performance tests were conducted, and based on the first-week charge-discharge curve, the discharge specific capacity at 0.1C was 337.81mAh / g, the reversible specific capacity was 299.10mAh / g, the first-week coulombic efficiency was 88.54%, and the 2C rate retention rate was 71.80%.

[0093] Example 4

[0094] Weigh out 9.28g of petroleum asphalt (softening point 190℃, density 1.12g / cm³). 313.92g of potassium hydroxide was pulverized and mixed, 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 300mL / min for 20min. Then, the temperature was raised to 500℃ at a nitrogen flow rate of 300mL / min and activated at that temperature for 40min. The temperature was then raised to 800℃ and activated at that temperature for 35min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask, washed with 10wt% dilute hydrochloric acid at a liquid-to-solid ratio of 25:1, and 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 an 80℃ forced-air drying oven for 6h and then subjected to air jet milling to obtain the first material.

[0095] The first material was loaded into a corundum boat and placed in a carbonization furnace. After replacing the air in the activation furnace with argon at a flow rate of 400 mL / min for 20 min, the temperature was raised to 1000℃ at an argon flow rate of 400 mL / min and carbonized at a constant temperature for 1 h. The temperature was then adjusted to 750℃, and the argon was switched to a growth atmosphere of 400 mL / min (methane volume percentage 55%, ethane volume percentage 10%, carbon dioxide volume percentage 8%, and argon volume percentage 27%), which was maintained for 120 min. The temperature was then raised to 1150℃ and maintained for 20 min. The temperature was then switched to nitrogen, and the mixture was cooled to room temperature in a nitrogen atmosphere to obtain the negative electrode material.

[0096] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 11.4 m². 2 / g, with micropores smaller than 2nm accounting for 71.3%; electrochemical performance tests were conducted, and based on the first-week charge-discharge curve, the discharge specific capacity at 0.1C was 304.61mAh / g, the reversible specific capacity was 272.11mAh / g, the first-week coulombic efficiency was 89.33%, and the 2C rate retention rate was 73.49%.

[0097] Example 5

[0098] Weigh out 7.68g of petroleum asphalt (softening point 230℃, density 1.17g / cm³). 3 15.36g of potassium hydroxide was pulverized and mixed, 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 250mL / min for 20min. Then, the temperature was raised to 350℃ at a nitrogen flow rate of 250mL / min and activated at that temperature for 60min. The temperature was then raised to 850℃ and activated at that temperature for 25min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask, washed with 7wt% dilute acetic acid at a liquid-to-solid ratio of 35:1, and 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 a 90℃ forced-air drying oven for 8h and then subjected to air jet milling to obtain the first material.

[0099] The first material was loaded into a corundum boat and placed in a carbonization furnace. After replacing the air in the activation furnace with argon at a flow rate of 350 mL / min for 20 min, the temperature was raised to 1500℃ at an argon flow rate of 350 mL / min and carbonized at a constant temperature for 2.5 h. The temperature was then adjusted to 780℃, and the argon was switched to a growth atmosphere of 350 mL / min (75% methane, 1% acetylene, 2% carbon dioxide, and 22% argon). This atmosphere was maintained for 100 min, and the temperature was raised to 900℃ and maintained for 60 min. The atmosphere was then switched to nitrogen, and the temperature was lowered to room temperature under a nitrogen atmosphere to obtain the negative electrode material.

[0100] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​7.6 m². 2 / g, with micropores smaller than 2nm accounting for 67.2%; its electrochemical performance was tested, and according to the first week charge-discharge curve, the discharge specific capacity at 0.1C was 300.54mAh / g, the reversible specific capacity was 266.43mAh / g, the first week coulombic efficiency was 88.65%, and the 2C rate retention rate was 72.64%.

[0101] Example 6

[0102] Weigh out 9.51g of petroleum asphalt (softening point 300℃, density 1.20g / cm³). 3 33.29g of potassium hydroxide was pulverized and mixed, 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 350mL / min for 20min. Then, the temperature was raised to 400℃ at a nitrogen flow rate of 350mL / min and activated at that temperature for 50min. The temperature was then raised to 700℃ and activated at that temperature for 60min. After cooling to room temperature in a nitrogen atmosphere, the activated product was transferred to a flask, washed with 2wt% 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 110℃ forced-air drying oven for 7h and then subjected to air jet milling to obtain the first material.

[0103] The first material was loaded into a corundum boat and placed in a carbonization furnace. The air in the activation furnace was replaced with argon at a flow rate of 150 mL / min for 30 min. Then, the temperature was raised to 1700℃ at an argon flow rate of 150 mL / min and carbonized at a constant temperature for 4 h. The temperature was then adjusted to 920℃, and the argon was switched to a growth atmosphere of 150 mL / min (methane volume percentage 60%, carbon dioxide volume percentage 15%, and argon volume percentage 25%) and maintained for 30 min. Then, the atmosphere was switched to nitrogen and cooled to room temperature in a nitrogen atmosphere to obtain the negative electrode material.

[0104] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​8.8 m². 2 / g, with micropores smaller than 2nm accounting for 88.1%; its electrochemical performance was tested, and according to the first week charge-discharge curve, the discharge specific capacity at 0.1C was 318.24mAh / g, the reversible specific capacity was 280.11mAh / g, the first week coulombic efficiency was 88.02%, and the 2C rate retention rate was 71.33%.

[0105] Example 7

[0106] Weigh out 8.72g of pellet coke and 26.16g of potassium hydroxide, pulverize and mix them, and place them in a corundum boat. Place the boat in an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 150mL / min for 20min. Then, heat to 900℃ at a nitrogen flow rate of 150mL / min and maintain the temperature for 40min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 8wt% dilute hydrochloric acid (liquid-solid mass ratio 40:1), filter, wash with ultrapure water (liquid-solid mass ratio 40:1), and dry the filter cake in a 100℃ forced-air drying oven for 9h. After air jet milling, obtain the first material.

[0107] The first material was loaded into a corundum boat and placed in a carbonization furnace. The air in the activation furnace was replaced with argon at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 1200℃ at an argon flow rate of 300 mL / min and carbonized at a constant temperature for 3 h. The temperature was then adjusted to 800℃, and the argon atmosphere was switched to a growth atmosphere at a flow rate of 300 mL / min (80% methane, 6% carbon dioxide, and 14% argon). This atmosphere was maintained for 80 min, and the temperature was raised to 950℃ and maintained for 40 min. The atmosphere was then switched to nitrogen, and the temperature was lowered to room temperature under a nitrogen atmosphere to obtain the negative electrode material.

[0108] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​9.7 m². 2 / g, with micropores smaller than 2nm accounting for 79.5%; its electrochemical performance was tested, and according to the first week charge-discharge curve, the discharge specific capacity at 0.1C was 309.17mAh / g, the reversible specific capacity was 254.32mAh / g, the first week coulombic efficiency was 82.26%, and the 2C rate retention rate was 70.02%.

[0109] Comparative Example 1

[0110] Weigh out 8.72g of pellet coke and 26.16g of potassium hydroxide, pulverize and mix them, and place them in a corundum boat. Place the boat in an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 150mL / min for 20min. Then, at a nitrogen flow rate of 150mL / min, raise the temperature to 400℃ and maintain this temperature for 80min. Next, raise the temperature to 900℃ and maintain this temperature for 40min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 8wt% dilute hydrochloric acid (liquid-solid mass ratio 40:1), filter, wash with ultrapure water (liquid-solid mass ratio 40:1), and dry the resulting filter cake in a 100℃ forced-air drying oven for 9h. After air jet milling, obtain the first material.

[0111] The first material was loaded into a corundum boat and placed in a carbonization furnace. The air in the activation furnace was replaced with argon at a flow rate of 300 mL / min for 20 min. The temperature was then adjusted to 800℃, and the argon atmosphere was switched to a growth atmosphere at a flow rate of 300 mL / min (80% methane, 6% carbon dioxide, and 14% argon). This atmosphere was maintained for 80 min, and then the temperature was raised to 950℃ and maintained for 40 min. The atmosphere was then switched to nitrogen, and the material was cooled to room temperature under the nitrogen atmosphere to obtain the negative electrode material.

[0112] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 10.3 m². 2 / g, with micropores smaller than 2nm accounting for 61.7%; its electrochemical performance was tested, and according to the first week charge-discharge curve, the discharge specific capacity at 0.1C was 392.10mAh / g, the reversible specific capacity was 306.90mAh / g, the first week coulombic efficiency was 78.27%, and the 2C rate retention rate was 51.54%.

[0113] Comparative Example 2

[0114] Weigh out 8.72g of pellet coke and 26.16g of potassium hydroxide, pulverize and mix them, and place them in a corundum boat. Place the boat in an activation furnace, and replace the air in the furnace with nitrogen at a flow rate of 150mL / min for 20min. Then, at a nitrogen flow rate of 150mL / min, raise the temperature to 400℃ and maintain this temperature for 80min. Next, raise the temperature to 900℃ and maintain this temperature for 40min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 8wt% dilute hydrochloric acid (liquid-solid mass ratio 40:1), filter, wash with ultrapure water (liquid-solid mass ratio 40:1), and dry the resulting filter cake in a 100℃ forced-air drying oven for 9h. After air jet milling, obtain the first material.

[0115] The first material was loaded into a corundum boat and placed in a carbonization furnace. Argon gas was used to replace the air in the activation furnace at a flow rate of 300 mL / min for 20 min. Then, the temperature was raised to 1200℃ at an argon gas flow rate of 300 mL / min and carbonized at a constant temperature for 3 h. The process was then switched to nitrogen gas and cooled to room temperature in a nitrogen atmosphere to obtain the negative electrode material.

[0116] The resulting negative electrode material underwent nitrogen physical adsorption, and its specific surface area was 3156.81 m². 2 / g, with micropores smaller than 2nm accounting for 57.8%; its electrochemical performance was tested, and according to the first-week charge-discharge curve, the discharge specific capacity at 0.1C was 727.21mAh / g, the reversible specific capacity was 316.41mAh / g, the first-week coulombic efficiency was 43.51%, and the 2C rate retention rate was 26.73%.

[0117] Comparative Example 3

[0118] Weigh out 6.34g of petroleum coke and 25.36g of potassium hydroxide, pulverize and mix them, and place them in a corundum boat. Put the boat into an activation furnace, replace the air in the furnace with nitrogen at a flow rate of 400mL / min for 20min, then heat to 450℃ at a nitrogen flow rate of 400mL / min and maintain the temperature for 60min. Then heat to 950℃ and maintain the temperature for 50min. Cool to room temperature in a nitrogen atmosphere, transfer the activated product to a flask, wash with 15wt% dilute nitric acid at a liquid-to-solid mass ratio of 20:1, filter, wash with ultrapure water at a liquid-to-solid mass ratio of 50:1, dry the resulting filter cake in a 120℃ forced-air drying oven for 4h, and then perform air jet milling to obtain the first material.

[0119] The first material was loaded into a corundum boat and placed in a carbonization furnace. After replacing the air in the activation furnace with argon at a flow rate of 200 mL / min for 20 min, the temperature was raised to 1400℃ at an argon flow rate of 200 mL / min and carbonized at a constant temperature for 4 h. The temperature was then adjusted to 700℃, and the argon atmosphere was switched to a growth atmosphere at a flow rate of 200 mL / min (methane volume percentage 65%, ethylene volume percentage 2%, and argon volume percentage 33%) and held for 150 min. The temperature was then raised to 1000℃ and held for 45 min. The temperature was then switched to nitrogen, and the material was cooled to room temperature under a nitrogen atmosphere to obtain the negative electrode material.

[0120] The resulting negative electrode material underwent nitrogen physical adsorption, resulting in a specific surface area of ​​8.7 m². 2 / g, with micropores smaller than 2nm accounting for 55.7%; electrochemical performance tests were conducted, and based on the first-week charge-discharge curve, the discharge specific capacity at 0.1C was 316.87mAh / g, the reversible specific capacity was 264.81mAh / g, the first-week coulombic efficiency was 83.57%, and the 2C rate retention rate was 70.64%.

Claims

1. A method for preparing a negative electrode material, the method comprising the following steps: (1) The organic carbon source is activated in the presence of an activator, and the first material is obtained by washing and drying after activation. (2) The first material obtained in step (1) is carbonized to obtain the second material; (3) After growing a heterogeneous carbon layer structure on the second material obtained in step (2), the negative electrode material is obtained.

2. The method for preparing the negative electrode material according to claim 1, wherein, The organic carbon source in step (1) comes from organic matter that can be carbonized to obtain carbon materials. The organic carbon source 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, wherein, The activator in step (1) is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide, preferably selected from one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate.

4. The method for preparing the negative electrode material according to claim 1, wherein, In step (1), the weight ratio of organic carbon source to activator 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, wherein, The activation conditions in step (1) are as follows: the activation temperature is 700-1000℃, preferably 750-950℃.

6. The method for preparing the negative electrode material according to claim 1 or 5, wherein, The activation process in step (1) includes a pre-activation process, wherein the pre-activation conditions are as follows: the pre-activation temperature is 200-500℃, preferably 300-450℃.

7. The method for preparing the negative electrode material according to claim 1, wherein, 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, wherein, The carbonization temperature in step (2) is 900-1800℃, preferably 1000-1400℃; the carbonization time is 0.5-6h, preferably 1-4h.

9. The method for preparing the negative electrode material according to claim 1, wherein, The process of obtaining the anode material by growing a heterogeneous carbon layer structure on the second material obtained in step (2) in step (3) is as follows: the second material obtained in step (2) is heat-treated in the presence of a growth atmosphere; the growth atmosphere includes low-carbon hydrocarbons, carbon dioxide and an inert atmosphere, and the inert atmosphere is a balance gas.

10. The method for preparing the negative electrode material according to claim 9, wherein, The volume percentage of low-carbon hydrocarbons is 1% to 98%, preferably 5% to 25% or 60% to 98%.

11. The method for preparing the negative electrode material according to claim 9, wherein, The volume percentage of carbon dioxide is 1% to 20%, preferably 2% to 15%.

12. The method for preparing the negative electrode material according to claim 9, wherein, 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.

13. The method for preparing the negative electrode material according to claim 9, wherein, The heat treatment includes two stages: a first stage heat treatment and a second stage heat treatment. The temperature of the first stage heat treatment is 700–900℃, preferably 700–850℃; the temperature of the second stage heat treatment is 900–1200℃, preferably 900–1150℃.

14. The method for preparing the negative electrode material according to claim 13, wherein, The second stage heat treatment temperature is 100–500°C higher than the first stage heat treatment temperature, preferably 100–300°C higher.

15. A negative electrode material obtained by the preparation method according to any one of claims 1-14.

16. The negative electrode material according to claim 15, wherein, The negative electrode material includes a core and an outer layer, wherein the core is a microporous carbon material and the outer layer is a heterogeneous carbon layer containing carbon nanotubes; wherein the mass ratio of the core to the outer layer is 100:1 to 100:50, preferably 100:5 to 100:

20.

17. The negative electrode material according to claim 15, wherein, The specific surface area of ​​the negative electrode material is 0–12 m². 2 / g, preferably 0-9m 2 / g.

18. The negative electrode material according to claim 15, wherein, The specific surface area of ​​the kernel is 100–3000 m². 2 / g, preferably 500–1800 m 2 / g.

19. The negative electrode material according to claim 15, wherein, The pore size of the microporous carbon material in the core is no greater than 10 nm, preferably no greater than 5 nm; among which, the proportion of micropores smaller than 2 nm is greater than 50%, and the pore size exhibits a multi-peak distribution characteristic.

20. The negative electrode material according to claim 15, wherein, The pore volume of the kernel is 0.6–1.3 cm³. 3 / g, preferably 0.6–1.0 cm 3 / g.

21. A sodium-ion battery, the sodium-ion battery comprising the negative electrode material according to any one of claims 15-20.

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