An amorphous carbon material, a method for preparing the same, and an application thereof

Abstract

The application provides an amorphous carbon material and a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. The amorphous carbon material comprises M elements, the M elements are selected from at least one of sulfur elements, selenium elements or tellurium elements; the amorphous carbon material contains C-M X -C covalent bonds and C-MO X -C covalent bonds, wherein x is selected from 1 or 2; the interplanar spacing d 002 of the amorphous carbon material is 0.355 nm to 0.410 nm; the La of the amorphous carbon material is 6.2 nm to 11.0 nm; and the Lc of the amorphous carbon material is 1.1 nm to 4.2 nm. By regulating the element doping and microstructure of the amorphous carbon material, the electronic conductivity and sodium storage performance of the amorphous carbon material can be improved, and the initial coulombic efficiency and cycle performance of the sodium ion battery can be improved.

Description

Technical Field

[0001] This application belongs to the field of sodium-ion battery technology, specifically relating to an amorphous carbon material, its preparation method, and its application. Background Technology

[0002] Sodium and lithium belong to the same group of alkali metals and have similar physicochemical properties. Furthermore, sodium and its compounds are relatively abundant, making sodium-ion batteries compatible and complementary to lithium-ion batteries in the energy storage field. Amorphous carbon materials, due to their advantages such as high specific capacity, low sodium storage potential, and good cycle stability, have become highly promising anode materials for sodium-ion batteries. Therefore, developing low-cost, high-performance carbon-based anode materials is crucial for promoting the development of sodium-ion batteries.

[0003] Most carbon-based anode materials exhibit electrochemical curves that include a plateau (where the slope of the curve is almost zero, typically between 0 and 0.1 V) and a ramp (where the slope of the curve is non-zero, typically above 0.1 V). The low potential of the plateau is beneficial for increasing the output voltage of the full cell; therefore, developing carbon materials with high plateau capacity has become a current research hotspot. Summary of the Invention

[0004] In view of this, this application provides an amorphous carbon material, its preparation method and application. By controlling the elemental doping and microstructure of the amorphous carbon material, its electronic conductivity and sodium storage performance can be improved, thereby improving the first coulombic efficiency and cycle performance of sodium-ion batteries.

[0005] In a first aspect, this application provides an amorphous carbon material comprising an element M, wherein the element M is selected from at least one of sulfur, selenium, or tellurium; the amorphous carbon material contains CM. X -C covalent bond and C-MO X -C covalent bond, where x is selected from 1 or 2; interplanar spacing d of amorphous carbon materials. 002 The la content of the amorphous carbon material ranges from 0.355 nm to 0.410 nm; the la content of the amorphous carbon material ranges from 6.2 nm to 11.0 nm; and the lc content of the amorphous carbon material ranges from 1.1 nm to 4.2 nm. The amorphous carbon material of this application is doped with at least one of sulfur, selenium, and tellurium to generate CM in the amorphous carbon material. X -C covalent bond and C-MO X -C covalent bonds form a cross-linked structure, providing capacity and assisting in pore formation. They can also create closed pores or micropores or mesopores with extremely small openings within amorphous carbon materials, which is beneficial for the storage of sodium ions at low potential plateaus and increases the proportion of plateau capacity. Furthermore, this application incorporates methods to increase the interplanar spacing d of the amorphous carbon material. 002This method can enhance electron conduction and improve the sodium storage performance of amorphous carbon materials. At the same time, by controlling the values ​​of La and Lc of the amorphous carbon material to be relatively small, the disorder and defect degree of the material are increased, which can provide more sodium ion storage sites, which is conducive to the rapid transfer and release of charge. Combined with the large number of closed pores or small open pores in the above materials, it can reduce the contact between the material and the electrolyte and side reactions, thereby improving the initial coulombic efficiency and cycle performance of sodium-ion batteries.

[0006] In some embodiments, the amorphous carbon material satisfies at least one of the following conditions:

[0007] (1) Interplanar spacing d of amorphous carbon materials 002 The wavelength ranges from 0.368 nm to 0.395 nm.

[0008] (2) The La of amorphous carbon materials is 7.9 nm to 10.5 nm;

[0009] (3) The Lc of the amorphous carbon material is 1.1 nm to 2.1 nm. When the microstructure of the amorphous carbon material is controlled to meet the above conditions, it can better cooperate with the cross-linked structure in the material, thereby improving the initial coulombic efficiency and cycle performance of the sodium-ion battery. In particular, when the amorphous carbon material simultaneously meets the above conditions (1) to (3), the resulting sodium-ion battery can exhibit even better initial coulombic efficiency and cycle performance.

[0010] In some embodiments, the mass percentage of element M is 1.1% to 5.0% based on the mass of the amorphous carbon material. Controlling the mass percentage of element M in the amorphous carbon material to satisfy the above relationship can further improve the initial coulombic efficiency and cycle performance of sodium-ion batteries by forming suitable closed pores through crosslinking.

[0011] In some embodiments, in the C1s spectrum of the amorphous carbon material, based on the total mass of the amorphous carbon material, CM X The mass percentage of -C covalent bonds is 41% to 49%, C-MO X The mass percentage of -C covalent bonds is 39% to 51%. When CM in amorphous carbon materials... X -C covalent bond and C-MO X When the content of -C covalent bonds satisfies the above relationship, the initial coulombic efficiency and cycle performance of sodium-ion batteries can be further improved.

[0012] Secondly, this application provides a method for preparing any of the above-mentioned amorphous carbon materials, comprising the following steps: Step 1, mixing asphalt and element M to obtain a mixture, placing the mixture in an inert atmosphere, then heating to a pretreatment temperature and performing pretreatment to obtain an intermediate; the heating rate to the pretreatment temperature is 0.2℃ / min to 30℃ / min; the pretreatment temperature is 80℃ to 600℃; the pretreatment time is 0.5h to 10h; Step 2, placing the intermediate in an inert atmosphere, then heating to a carbonization temperature and performing carbonization treatment to obtain an amorphous carbon material; the heating rate to the carbonization temperature is 0.2℃ / min to 30℃ / min; the carbonization temperature is 800℃ to 2000℃; the carbonization treatment time is 0.5h to 10h. This preparation method uses asphalt as a carbon source and mixes it with element M to form a precursor material. After pretreatment and high-temperature carbonization, it can obtain amorphous carbon materials with high plateau characteristics at relatively low temperatures. This preparation method has the advantages of strong operability, high carbon yield, simple raw materials, high consistency of product morphology, high safety and high reaction efficiency.

[0013] In some embodiments, the mass ratio of bitumen to element M is 1:(0.3 to 3.0); and / or, element M is selected from at least one of elemental sulfur, elemental selenium, or elemental tellurium.

[0014] In some implementations, the inert atmosphere includes nitrogen and / or argon.

[0015] Preferably, the inert atmosphere also includes hydrogen, with the volume percentage of hydrogen being 5% to 40% based on the volume of the inert gas.

[0016] Thirdly, this application provides a negative electrode sheet, including a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes any of the above-mentioned amorphous carbon materials or amorphous carbon materials obtained by any of the preparation methods.

[0017] In some embodiments, a negative electrode sheet and a sodium metal sheet are used to form a coin cell, which is charged with a constant current of 0.1C to a cutoff voltage of 2.5V. Based on the total capacity of the coin cell, the capacity with a charging potential below 0.1V accounts for 61% to 74%.

[0018] Fourthly, this application provides a sodium-ion battery, including any of the above-mentioned negative electrode sheets.

[0019] The beneficial effects of this application are as follows: This application discloses an amorphous carbon material and its preparation method. Through the combination of elemental M and pretreatment and carbonization treatment, the following effects can be achieved: (1) Elemental M can react with pitch carbon source under pretreatment conditions to form CM. X-C covalent bond, C-MO X -C covalent bonds prevent the orderly stacking of carbon layers during subsequent high-temperature carbonization, thereby inhibiting the graphitization of carbon materials at high temperatures; (2) M atoms in amorphous carbon materials can change the electron distribution within the carbon layer, inducing the formation of rolled carbon layers during carbonization, which is beneficial for the formation of closed pores, thereby achieving high plateau capacity; (3) Compared to oxygen or nitrogen atoms, M atoms, including at least one of S, Se, or Te atoms, are more easily removed at lower temperatures, resulting in a significant reduction in the temperature for constructing pitch-based carbon materials with high plateau characteristics. Based on this, the method provided in this application can obtain amorphous carbon materials with high plateau characteristics and high capacity at relatively low temperatures such as 800℃ or 1300℃. The reversible specific capacity at 0.1C can reach more than 315mAh / g, with a plateau capacity ratio of more than 60%. After 100 cycles at 0.5C, the reversible specific capacity can be maintained above 205mAh / g. It has excellent electrochemical performance, huge potential commercial value, and is suitable for promotion and application.

[0020] The above description is merely an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it according to the contents of the specification, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings. The specific implementation methods of this application are given in detail in the following embodiments and their accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 The first charge-discharge curve of the amorphous carbon material (A3) prepared in Example 3 of this application at 0.1C is shown.

[0023] Figure 2 These are the cycling performance diagrams of the amorphous carbon materials of Example 3 and Comparative Example 1 of this application;

[0024] Figure 3 These are S2p XPS diagrams of the amorphous carbon materials in Examples 2, 3, and 4 of this application;

[0025] Figure 4 The first charge-discharge curve of the amorphous carbon material (A6) prepared in Example 6 of this application at 0.1C is shown.

[0026] Figure 5This is the XRD pattern of the amorphous carbon material (A6) prepared in Example 6 of this application;

[0027] Figure 6 The first charge-discharge curve of the amorphous carbon material (A9) prepared in Example 9 of this application at 0.1C is shown.

[0028] Figure 7 This is a SEM image of the amorphous carbon material (A9) prepared in Example 9 of this application;

[0029] Figure 8 The first charge-discharge curve of the amorphous carbon material (B1) prepared in Comparative Example 1 of this application is shown at 0.1C.

[0030] Figure 9 This is the XRD pattern of the amorphous carbon material (B1) prepared in Comparative Example 1 of this application;

[0031] Figure 10 This is a SEM image of the amorphous carbon material (B1) prepared in Comparative Example 1 of this application;

[0032] Figure 11 Small-angle X-ray scattering (SAXS) images of amorphous carbon materials in Examples 2-4 and Comparative Example 1 of this application;

[0033] Figure 12 The amorphous carbon materials of Examples 2-4 and Comparative Example 1 of this application are in... The diagram shows the SAXS intensity and pore volume ratio obtained from N2 adsorption / desorption. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] Mechanistic studies of the electrochemical curves of amorphous carbon materials have shown that the plateau segment originates from the filling of sodium ions within the closed pores, while the ramp segment is related to defects and functional groups in the carbon material. The closed pores are formed by the stacking and entanglement of graphite microcrystalline domains composed of carbon layers of a certain size, and are closely related to the precursor and carbonization temperature of the carbon material. Therefore, selecting a suitable precursor or corresponding precursor processing technology is crucial. However, for a given precursor, the content of closed pores typically increases first and then decreases with increasing temperature, reaching its maximum between 1500℃ and 1900℃. Within this temperature range, the content of defects and functional groups in the carbon material decreases sharply, resulting in a significant reduction in the reversible capacity. Therefore, the high plateau characteristic of amorphous carbon materials is usually achievable only above 1500℃. Thus, preparing carbon materials with high plateau characteristics or high plateau characteristics at relatively lower temperatures has significant research value and promising prospects for industrial applications.

[0036] As a petrochemical byproduct, asphalt is considered a promising precursor for carbon materials due to its low cost and high carbon content. However, because of its soft carbon precursor properties, direct high-temperature carbonization and pyrolysis of asphalt often yields soft carbon materials with a high degree of graphitization. These materials have almost no closed pores, resulting in poor sodium storage performance (<100 mAh·g). -1 The current methods for controlling the microstructure of low-cost pitch precursors to achieve high-capacity pitch-based carbon materials with a large number of closed pores and extremely low defect content at lower temperatures are insufficient for the commercial application of sodium-ion batteries. Therefore, developing new microstructure control methods for low-cost pitch precursors is a key technology that urgently needs to be developed.

[0037] Based on the above problems, this application proposes an amorphous carbon material comprising element M, wherein element M is selected from at least one of sulfur, selenium, or tellurium; the amorphous carbon material contains CM. X -C covalent bond and C-MO X -C covalent bond, where x is selected from 1 or 2; interplanar spacing d of amorphous carbon materials. 002The wavelength ranges from 0.355 nm to 0.410 nm; the La wavelength of amorphous carbon materials ranges from 6.2 nm to 11.0 nm; and the Lc wavelength of amorphous carbon materials ranges from 1.1 nm to 4.2 nm. This application employs element M for chemical cross-linking within amorphous carbon. This chemical cross-linking involves the chemical bonding of the amorphous carbon material with S, Se, or Te at high temperatures, forming covalent bonds. These covalent bonds make the amorphous carbon material difficult to break and maintain a neat arrangement during high-temperature carbonization, thus forming a turbulent carbon layer that is more conducive to sodium ion diffusion and storage. This improves the overall reversible specific capacity of sodium ions and also assists in pore formation (pore formation arises from two aspects: firstly, the turbulent carbon layers caused by chemical cross-linking interweave to form sub-nanometer closed pores; secondly, the formation of a three-dimensional network structure binds some ions to the carbon layer, allowing a small number of ions to be removed only at higher temperatures. Higher removal temperatures help to disrupt the neatly arranged carbon layers at low temperatures, forming micropores and mesopores with extremely small openings; both of these pore structures are beneficial for sodium ion storage at low potential plateaus, thus increasing the plateau capacity ratio). The multi-closed-pore framework structure formed by the above-mentioned chemical cross-linking, combined with the large interlayer spacing of amorphous carbon materials and the increase in material disorder and randomness, can further improve the sodium storage capacity and sodium ion kinetics of amorphous carbon materials, thereby improving the first coulombic efficiency and cycle performance of sodium-ion batteries.

[0038] For example, the interplanar spacing d of shaped carbon materials 002The la value is from 0.355 nm to 0.410 nm, for example, it can be a value within the range of 0.355 nm, 0.362 nm, 0.367 nm, 0.371 nm, 0.375 nm, 0.376 nm, 0.383 nm, 0.387 nm, 0.390 nm, 0.397 nm, 0.400 nm, 0.406 nm, 0.408 nm, 0.410 nm, or any combination thereof; the la value of amorphous carbon materials is from 6.2 nm to 11.0 nm, for example, it can be 6.2 nm, 6.3 nm, 6.6 nm, 7.0 nm, 7.6 nm, 7.7 nm. The Lc values ​​are within the range of nm, 8.3 nm, 8.7 nm, 9.0 nm, 9.5 nm, 9.7 nm, 10.0 nm, 10.5 nm, 10.8 nm, 11.0 nm, or any combination thereof; the Lc value of amorphous carbon materials is from 1.1 nm to 4.2 nm, for example, it can be within the range of 1.1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 2.0 nm, 2.3 nm, 2.3 nm, 2.8 nm, 3.0 nm, 3.1 nm, 3.4 nm, 3.7 nm, 3.8 nm, 4.1 nm, 4.2 nm, or any combination thereof. When the interlayer spacing and disorder of amorphous carbon materials are controlled to meet the above conditions, they can better cooperate with the cross-linked structure in the material, improving the initial coulombic efficiency and cycle performance of sodium-ion batteries.

[0039] In some embodiments, the mass percentage of element M in the amorphous carbon material is from 1.1% to 5.0%, for example, it can be a value within the range of 1.1%, 1.3%, 1.6%, 1.9%, 2.0%, 2.5%, 2.9%, 3.2%, 3.3%, 3.6%, 3.9%, 4.1%, 4.6%, 4.9%, 5.0%, or any combination thereof. Controlling the mass percentage of element M in the amorphous carbon material to satisfy the above relationship enables the formation of suitable closed pores through crosslinking, increasing the closed-pore ratio and further improving the initial coulombic efficiency and cycle performance of sodium-ion batteries.

[0040] In some embodiments, in the C1s spectrum of amorphous carbon materials, based on the total mass of the amorphous carbon material, CM X The mass percentage of -C covalent bonds is 41% to 49%, for example, it can be a value within the range of 41.00%, 41.07%, 42.18%, 42.83%, 43.25%, 43.52%, 44.49%, 45.26%, 45.79%, 46.48%, 46.87%, 47.16%, 48.28%, 48.61%, 49.00%, or any two of these ranges; C-MO XThe mass percentage of -C covalent bonds is 39% to 51%, for example, it can be a value within the range of 39.00%, 39.58%, 40.14%, 41.62%, 42.67%, 42.77%, 44.05%, 44.65%, 45.95%, 47.25%, 47.76%, 48.80%, 49.84%, 50.69%, 51.00%, or any combination thereof. This involves controlling the CM content in amorphous carbon materials. X -C covalent bond and C-MO X When the mass percentage of -C covalent bonds satisfies the above relationship, the cross-linking structure inside the amorphous carbon material can be further optimized, the proportion of closed pores can be increased, the capacity proportion of the low potential plateau in the charge-discharge curve of sodium-ion batteries can be improved, and the initial coulombic efficiency and cycle performance can be improved.

[0041] In some embodiments, the amorphous carbon material further includes C=S covalent bonds. In the C1s spectrum of the amorphous carbon material, the mass percentage of C=S covalent bonds is 0.7% to 1.5% based on the total mass of the amorphous carbon material. For example, it can be a value within the range of 0.70%, 0.73%, 0.77%, 0.87%, 0.89%, 0.95%, 1.06%, 1.07%, 1.17%, 1.20%, 1.29%, 1.35%, 1.40%, 1.44%, 1.5%, or any combination thereof.

[0042] In some embodiments, small-angle X-ray scattering (SAXS) analysis is performed on the amorphous carbon material of this application, and the amorphous carbon material is analyzed in... Based on the SAXS intensity at the location, the percentage of closed pore volume, based on the total pore volume of amorphous carbon, is 97.0% to 98.5%, for example, it can be a value within the range of 97.0%, 97.2%, 97.3%, 97.4%, 97.5%, 97.6%, 97.7%, 97.9%, 98.0%, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, or any combination thereof.

[0043] The preparation method of the aforementioned amorphous carbon material in this application includes the following steps: Step 1: Mixing asphalt and element M to obtain a mixture, placing the mixture in an inert atmosphere, then heating to a pretreatment temperature and performing pretreatment to obtain an intermediate; the heating rate to the pretreatment temperature is 0.2℃ / min to 30℃ / min; the pretreatment temperature is 80℃ to 600℃; the pretreatment time is 0.5h to 10h; Step 2: Placing the intermediate in an inert atmosphere, then heating to a carbonization temperature and performing carbonization treatment to obtain an amorphous carbon material; the heating rate to the carbonization temperature is 0.2℃ / min to 30℃ / min; the carbonization temperature is 800℃ to 2000℃; the carbonization time is 0.5h to 10h. This application, through the above preparation method, promotes the chemical cross-linking of the asphalt carbon source and element M through pretreatment and carbonization treatment, forming amorphous carbon material. X -C covalent bond and C-MO X -C covalent bonds can form turbulent carbon layers that are more conducive to the diffusion and storage of sodium ions, as well as closed pores, micropores or mesopores with extremely small openings. This is beneficial to increasing the plateau capacity ratio of sodium-ion batteries. It can also improve the interlayer spacing and disorder of amorphous carbon materials. Combined with closed pores, it can further improve the first coulombic efficiency and cycle performance of sodium-ion batteries.

[0044] In some embodiments, the asphalt is selected from at least one of low-temperature coal tar pitch, medium-temperature coal tar pitch, high-temperature coal tar pitch, petroleum asphalt, and coal tar pitch. In this application, low-temperature coal tar pitch refers to coal tar pitch with a softening point ≤75℃; medium-temperature coal tar pitch refers to coal tar pitch with a softening point >75℃ and ≤95℃; and high-temperature coal tar pitch refers to coal tar pitch with a softening point >95℃.

[0045] In some embodiments, the mass ratio of asphalt to elemental M is 1:(0.3 to 3.0), for example, a mass ratio of asphalt to elemental M of 1:0.3, 1:0.5, 1:0.7, 1:0.9, 1:1.2, 1:1.4, 1:1.5, 1:1.8, 1:2.2, 1:2.3, 1:2.5, 1:2.6, 1:2.8, 1:3, or any combination thereof. When the mass ratio of asphalt to elemental M is controlled within the above range, it is beneficial to improve the chemical cross-linking effect, increase the closed-cell ratio of amorphous carbon materials, and further improve the initial coulombic efficiency and cycle performance of sodium-ion batteries. Preferably, the mass ratio of asphalt to elemental M is 1:(0.5 to 1.5), more preferably 1:(0.7 to 1.2).

[0046] In some embodiments, the specific method for obtaining the mixture is as follows: the asphalt and sulfur / selenium / tellurium are treated by any one of wet mixing and solid-phase grinding, and then dried by any one of freezing, vacuum or heating to obtain the mixture; wherein the solvent for wet mixing is any one of water, nitric acid, ethanol, acetone, cyclohexane, carbon disulfide, benzene, toluene and quinoline.

[0047] In some embodiments, the inert atmosphere includes nitrogen and / or argon, and further includes hydrogen, wherein the volume percentage of hydrogen is 5% to 40% based on the volume of the inert gas, for example, values ​​within the range of 5%, 7%, 9%, 12%, 15%, 18%, 19%, 24%, 26%, 29%, 31%, 33%, 36%, 40%, or any combination thereof. For example, the inert atmosphere is a mixture of argon and hydrogen.

[0048] In some embodiments, the heating rate to the pretreatment temperature is from 0.2°C / min to 30°C / min, for example, a value within the range of 0.2°C / min, 1.8°C / min, 4.2°C / min, 5.4°C / min, 8.3°C / min, 9.9°C / min, 13.9°C / min, 15.8°C / min, 17.8°C / min, 20.0°C / min, 21.0°C / min, 25.3°C / min, 25.9°C / min, 28.4°C / min, 30°C / min, or any combination thereof; the pretreatment temperature is 80°C. The temperature ranges from ℃ to 600℃, for example, values ​​within the range of 80℃, 94℃, 158℃, 172℃, 208℃, 258℃, 315℃, 353℃, 388℃, 420℃, 447℃, 519℃, 541℃, 565℃, 600℃, or any combination thereof; the pretreatment time ranges from 0.5h to 10h, for example, values ​​within the range of 0.5h, 0.6h, 1.3h, 2.6h, 3.2h, 4.2h, 4.7h, 5.2h, 6.2h, 6.7h, 7.7h, 7.9h, 9.1h, 9.4h, 10h, or any combination thereof. When the pretreatment conditions are controlled within the above ranges, it is beneficial to improve the chemical cross-linking effect of the pitch carbon source and elemental M, increase the closed-cell ratio, interlayer spacing, and disorder of the amorphous carbon material, and improve the initial coulombic efficiency and cycle performance of the sodium-ion battery.

[0049] In some embodiments, the heating rate to the carbonization temperature is from 0.2°C / min to 30°C / min, for example, a value within the range of 0.2°C / min, 1.8°C / min, 4.2°C / min, 5.4°C / min, 8.3°C / min, 9.9°C / min, 13.9°C / min, 15.8°C / min, 17.8°C / min, 20.0°C / min, 21.0°C / min, 25.3°C / min, 25.9°C / min, 28.4°C / min, 30°C / min, or any combination thereof; the carbonization temperature is from 800°C to 2000°C. For example, values ​​within the range of 800℃, 850℃, 980℃, 1050℃, 1140℃, 1230℃, 1280℃, 1440℃, 1520℃, 1620℃, 1660℃, 1740℃, 1850℃, 1960℃, 2000℃, or any two of these ranges; the carbonization time is from 0.5h to 10h, for example, values ​​within the range of 0.5h, 0.6h, 1.3h, 2.6h, 3.2h, 4.2h, 4.7h, 5.2h, 6.2h, 6.7h, 7.7h, 7.9h, 9.1h, 9.4h, 10h, or any two of these ranges. When the conditions for carbonization treatment are controlled within the above range, it is beneficial to improve the chemical cross-linking effect of pitch carbon source and element M, increase the closed-pore ratio, interlayer spacing and disorder of amorphous carbon materials, and further improve the first coulombic efficiency and cycle performance of sodium-ion batteries.

[0050] This application also provides a negative electrode sheet, including a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes any of the above-mentioned amorphous carbon materials or amorphous carbon materials obtained by any of the preparation methods.

[0051] In some embodiments, a negative electrode sheet and a sodium metal sheet are used to fabricate a coin cell, which is then charged at a constant current of 0.1C to a cutoff voltage of 2.5V. Based on the total capacity of the coin cell, the capacity percentage with a charging potential below 0.1V is 61% to 74%. That is, the plateau potential of the amorphous carbon material of this application is 61% to 74%, for example, it can be a value within the range of 61.0%, 61.5%, 62.8%, 63.3%, 64.8%, 65.4%, 66.9%, 67.1%, 68.1%, 69.8%, 70.6%, 71.5%, 72.4%, 73.2%, 74.0%, or any combination thereof. The amorphous carbon material of this application forms closed pores through the chemical cross-linking of the M element, in conjunction with the interplanar spacing d... 002 Furthermore, the regulation of disorder can improve the capacity of the plateau segment, which in turn helps to improve the first coulombic efficiency and cycle performance of sodium-ion batteries.

[0052] In some embodiments, the negative electrode current collector includes at least one of aluminum foil, copper foil, or stainless steel foil. In this application, the negative electrode active material layer further includes a binder, which includes at least one of sodium cellulose, sodium carboxymethyl cellulose, hydroxypropyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, diacetyl cellulose, polyacrylic acid, sodium alginate, styrene-butadiene rubber, butadiene acrylate rubber, polypyrrole, polyaniline, epoxy resin, or guar gum.

[0053] In some embodiments, the preparation method of the above-mentioned negative electrode sheet includes the following steps: adding the above-mentioned artificial SEI film modified amorphous carbon material and polymer binder to a solvent and stirring to form a uniform slurry, coating the slurry onto the negative electrode current collector, and drying to obtain the negative electrode; wherein, the solvent may be selected from at least one of water, acetone, N-methylpyrrolidone, dimethylformamide or ethanol.

[0054] Finally, this application provides a sodium-ion battery, including any of the above-mentioned negative electrode plates.

[0055] In this application, the sodium-ion battery further includes a positive electrode, which comprises a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material, which may include at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0056] In some embodiments, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce. For example, the sodium transition metal oxide is Na. x MO2, wherein M is at least one of Ti, V, Mn, Co, Ni, Fe, Cr or Cu, and 0 < x ≤ 1.

[0057] In some embodiments, the polyanionic compound may be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y can be at least one of P, S, or Si; n represents (YO4). n The price state.

[0058] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. nA class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y can be at least one of P, S, or Si, and n represents (YO4). n The valence state; the halogen can be at least one of F, Cl or Br.

[0059] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, or Si, and n represents (YO4). n The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce, and m represents (ZO). y ) m+ The valence state; the halogen can be at least one of F, Cl or Br.

[0060] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3, NaM'PO4F (where M' is one or more of V, Fe, Mn, and Ni) or Na3(VO y )2(PO4)2F 32y At least one of (0≤y≤1).

[0061] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co or Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0062] In some embodiments, the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode. This application does not impose specific limitations on the type of conductive agent, which can be selected according to actual needs. As an example, the conductive agent may be at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, or carbon nanofibers.

[0063] In some embodiments, the positive electrode active material layer may further include a binder to firmly bond the positive electrode active material and optional conductive agent to the positive electrode current collector. This application does not impose specific limitations on the type of binder, which can be selected according to actual needs. As an example, the binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), or carboxymethyl chitosan (CMCS).

[0064] In some embodiments, the positive current collector can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, or carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate can each be independently selected from at least one of copper, aluminum, nickel, or stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil with a polymer base film.

[0065] The positive current collector is one or more of the following: copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil, with aluminum foil being preferred.

[0066] The above-mentioned positive electrode can be prepared according to conventional methods in the art. Typically, the positive electrode active material and optional conductive agent and binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector, and after drying and cold pressing, the positive electrode is obtained.

[0067] The sodium-ion battery of this application also includes a separator membrane, which can be any material suitable for separator membranes of electrochemical energy storage devices in the art. For example, it can be at least one of the following: polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, or natural fiber.

[0068] The electrolyte may include an organic solvent and a sodium electrolyte salt. As an example, the organic solvent may also include at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or methyl tert-butyl ether; the sodium electrolyte salt may be at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, or sodium chloride.

[0069] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes to obtain a battery cell. Alternatively, the battery cell can be obtained by winding. The battery cell is placed in a packaging shell (which can be a soft pack, a square aluminum shell, a square steel shell, a cylindrical aluminum shell, or a cylindrical steel shell), electrolyte is injected, and the shell is sealed to obtain a sodium-ion battery.

[0070] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Unless otherwise specified, the raw materials used in the following embodiments are all from common commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0071] Example 1

[0072] The amorphous carbon material in this embodiment is prepared using a method comprising the following steps:

[0073] Step 1, Grinding: Mix asphalt and sublimed sulfur at a mass ratio of 1:0.5, and grind at a grinding speed of 500 r / min for 1 hour to obtain a mixture;

[0074] Drying: The mixture obtained by grinding was placed in an oven at 100°C and dried for 12 hours;

[0075] Pretreatment: The dried mixture is placed in a tube furnace for pretreatment, during which a sulfidation reaction occurs using argon as the sulfidation atmosphere. The temperature settings of the tube furnace for this pretreatment are as follows: when the furnace temperature is <150℃, the temperature is increased at a rate of 0.2℃ / min; when the furnace temperature is ≥150℃, the temperature is held for 0.5h. Then, the pretreated intermediate material is allowed to cool naturally to room temperature.

[0076] Step 2, Carbonization Treatment: The pretreated intermediate material is ground and placed in a high-temperature tube furnace for carbonization treatment, using argon as the carbonization atmosphere. The temperature of the high-temperature tube furnace is set as follows: when the furnace temperature is <1100℃, the temperature is increased at a rate of 0.5℃ / min; when the furnace temperature is ≥1100℃, the temperature is held for 3 hours. The carbonization treatment yields the amorphous carbon material in this embodiment, which is then naturally cooled to room temperature.

[0077] Sorting: The amorphous carbon material obtained after carbonization is passed through a 200-mesh vibrating screen and sorting equipment to obtain amorphous carbon material with uniform particle size (amorphous carbon material number A1).

[0078] Examples 2-10

[0079] The preparation methods of the amorphous carbon materials provided in Examples 2-10 are basically the same as those in Example 1, with the main differences being in the process parameter settings, component ratios, and the elemental M, as shown in Table 1. Specifically, sublimed sulfur, selenium powder, and tellurium powder are used for S, Se, and Te, respectively. In Examples 7, 8-10, freeze-drying is employed for 12 hours. The samples obtained in Examples 2-10 are A2 to A10, respectively.

[0080] Comparative Example 1

[0081] The preparation method of the amorphous carbon material in this comparative example is basically the same as that in Example 1. The main difference is that sublimed sulfur is not added, and only pitch is ground in step 1, followed by subsequent drying, pretreatment, carbonization and sorting. The resulting amorphous carbon material is numbered B1.

[0082] Comparative Examples 2-4

[0083] The preparation methods of the amorphous carbon materials provided in Comparative Examples 2-4 are basically the same as those in Comparative Example 1, with the main differences being in the setting of process parameters, component ratios, and the element M, as shown in Table 1. In Comparative Examples 3 and 4, freeze-drying was used for 12 hours. The samples obtained in Comparative Examples 2-4 are B2-B4, respectively.

[0084] Table 1

[0085]

[0086]

[0087] Performance testing:

[0088] Amorphous carbon materials A1-A10 and B1-B4 obtained in Examples 1-10 and Comparative Examples 1-4, respectively, were used as active materials and assembled into sodium-ion batteries according to the following method. Electrochemical performance tests were performed, and the results are shown in Table 2. The preparation method of the sodium-ion battery includes the following steps:

[0089] (1) Mix and grind the above active materials with sodium alginate at a mass ratio of 9:1, add deionized water and wet grind until the slurry can pass through a 200-mesh stainless steel screen.

[0090] (2) The slurry ground in step (1) was coated onto copper foil using a wet film coating machine, with a thickness of 200 μm. Then it was transferred to a vacuum oven at 120°C and dried for 12 h to obtain an electrode sheet.

[0091] (3) Cut the electrode sheet from step (2) into small circular pieces with a diameter of 12 mm and transfer them to a glove box filled with argon gas. Assemble the button cell in the following order: negative electrode shell, spring sheet, gasket, sodium metal sheet, separator, small circular electrode sheet, and positive electrode shell. Add 150 μL of electrolyte. (The button cell model used is CR2032, the separator is a glass fiber separator, and the electrolyte is sodium hexafluorophosphate (NaPF6) dissolved in a solvent of ethylene carbonate and dimethyl carbonate (mass ratio of 1:1). The mass percentage of NaPF6 is 12% based on the mass of the electrolyte.) After assembly, let it stand at room temperature for 8 hours to obtain a sodium-ion battery.

[0092] Discharge specific capacity and charge specific capacity tests: The sodium-ion battery was discharged at a constant current of 0.1C to a cutoff voltage of 0V, and the discharge specific capacity of the sodium-ion battery was measured; the sodium-ion battery was charged at a constant current of 0.1C to a cutoff voltage of 2.5V, and the charge specific capacity of the sodium-ion battery was measured.

[0093] Initial coulombic efficiency = charge specific capacity / discharge specific capacity × 100%.

[0094] Plot the charge-discharge curves of the sodium-ion battery. Based on the charging curves, calculate the percentage of the capacity at charging potentials below 0.1V relative to the total capacity of the sodium-ion battery. This percentage represents the plateau percentage of the sodium-ion battery.

[0095] Table 2

[0096]

[0097]

[0098] Figure 1 , Figure 4 , Figure 6 and Figure 8 The first charge-discharge curves for A3, A6, A9, and B1 at 0.1C are shown. Figure 1 , Figure 4 , Figure 6 and Figure 8The comparison shows that the amorphous carbon material prepared by the method of Example 3 in this application has a discharge capacity (i.e., discharge specific capacity) of 448 mAh / g and a reversible capacity (i.e., charging capacity, charging specific capacity) of 315.2 mAh / g, with a coulombic efficiency of 70.36% during the first charge-discharge process; the amorphous carbon material prepared by the method of Example 6 has a discharge capacity of 416.64 mAh / g and a reversible capacity of 330.30 mAh / g, with a coulombic efficiency of 79.27% ​​during the first charge-discharge process; the amorphous carbon material prepared by the method of Example 9 has a discharge capacity of 379.70 mAh / g and a reversible capacity of 317.60 mAh / g, with a coulombic efficiency of 83.64% during the first charge-discharge process; while the amorphous carbon material prepared by the method of Comparative Example 1 has a discharge capacity of 153.60 mAh / g, a reversible capacity of 109 mAh / g, and a coulombic efficiency of 70.96% during the first charge-discharge process. The amorphous carbon materials prepared by the methods in Examples 1-10 and Comparative Examples 1-4 were subjected to their first charge-discharge tests, and their discharge capacity, reversible capacity, and coulombic efficiency are shown in Table 2. It was found that the plateau percentage in Examples 1-10 exceeded 60%, and the total reversible specific capacity exceeded 300 mAh / g. This demonstrates that the amorphous carbon materials prepared by the method of this application show significant improvements in discharge capacity, reversible capacity, and coulombic efficiency, indicating that the preparation method provided by this application and the resulting amorphous carbon materials can effectively improve sodium storage performance.

[0099] X-ray photoelectron spectroscopy (XPS) analysis was performed on the amorphous carbon materials of Examples 2, 3 and 4 of this application and Comparative Example 1 to analyze the chemical bond state of the organic matter. Figure 3 These are the S2p XPS spectra of the amorphous carbon materials of Examples 2, 3, and 4 of this application. The plateau percentage, mass percentage of each chemical bond in the C 1s spectrum, and mass percentage of each chemical bond in the S2p spectrum of the amorphous carbon materials of the above examples and Comparative Example 2 were tested, and the results are shown in Table 3 below.

[0100] Table 3

[0101]

[0102] Depend on Figure 3 As shown in Table 3, the amorphous carbon materials prepared in Examples 2-4 of this application all contain CS. X -C bond, C=S bond and C-SO X-C bonds, and the changes in these bonds are shown in Table 3. With the increase of S content in the bulk phase, the plateau capacity, XPS C1s and S2p partial covalent bond content of the amorphous carbon materials prepared in Examples 2-4 all increased compared to Comparative Example 2. Furthermore, by comparing the component ratios of Examples 2-4, it was found that the higher the mass ratio of sublimed sulfur to pitch, the higher the S content in the bulk phase of the sample, and the higher the C1s and S2p covalent bond content. X -C, C-SO X Both -C and C=S increase with the mass ratio of sublimed sulfur to bitumen. The plateau capacity percentage increases with the partial covalent bond content calculated by XPS C 1s and S 2p spectra, but stops increasing significantly after reaching a certain level. This indicates that the plateau capacity percentage and CS... X -C, C-SO X -C and C=S chemical bonds are positively correlated, and the increase slows down after reaching a certain level.

[0103] Cyclic performance test: The sodium-ion battery was discharged to 0V at a constant current of 0.5C, and then charged at a constant current of 0.5C with a cutoff voltage of 2.5V. This process is considered one cycle. After 160 cycles, the discharge specific capacity of the sodium-ion battery was measured.

[0104] Figure 2 This is a cycling performance diagram of the amorphous carbon materials of Example 3 and Comparative Example 1 of this application. Figure 2 As shown, the amorphous carbon material in Comparative Example 1 had a discharge specific capacity of 111 mAh / g after 160 cycles. Compared to Example 2, the comparative example, which was not modified by sulfur crosslinking, showed a significant decrease in discharge specific capacity. This is because, in Example 3 of this application, after sulfur crosslinking modification, the carbon material had a multi-closed-pore framework structure and a larger interlayer spacing, leading to increased material disorder and chaos; simultaneously, sulfur was present in oxidized form (C-SO4). X It exists in the form of β-C and thiophene sulfur (CSC 2p3 / 2 and CSC 2p1 / 2). After high-temperature pyrolysis, its microstructure changes, generating a large number of closed pores, which improves sodium storage capacity and sodium ion kinetics.

[0105] Figure 5 and Figure 9 The images show the XRD patterns of the amorphous carbon materials prepared in Example 6 and Comparative Example 1, respectively. Figure 5 and Figure 9 The comparison shows that the amorphous carbon material prepared by the method in Example 6 of this application exhibits a typical bimodal structure of amorphous carbon, corresponding to ( 002 The (100) and (100) crystal planes, after calculation, have their d 002 =0.3901, while the d of the amorphous carbon material prepared by the method in Comparative Example 1 is... 002The interlayer spacing d was calculated after XRD analysis of the amorphous carbon materials prepared by the same methods in Examples 1-10 and Comparative Examples 1-4, which were 3.487. 002 As shown in Table 2, it can be seen that the interlayer spacing d of the amorphous carbon material prepared by the method of this application is... 002 Both improved, indicating that the M-element modification preparation method provided in this application can increase the interlayer spacing and enhance electronic conduction, thereby improving the sodium storage performance of amorphous carbon materials.

[0106] Figure 7 and Figure 10 The images shown are SEM images of the amorphous carbon materials prepared in Example 9 and Comparative Example 1, respectively. Figure 7 and Figure 10 It can be seen that the amorphous carbon material prepared by the method in Example 9 of this application has a smaller particle size, softened edges, lost layered structure, rough surface, and inconspicuous pores. In contrast, the amorphous carbon material prepared in Comparative Example 1 has sharp edges and a large particle morphology, exhibiting a distinct layered structure. Similarly, SEM analysis of the amorphous carbon materials prepared in Examples 1-10 shows that their SEM images are similar to those of the amorphous carbon material in Example 9. This demonstrates that the amorphous carbon material prepared by the method of this application is beneficial for improving the sodium storage performance of the material.

[0107] Furthermore, the variations in La and Lc of the amorphous carbon materials prepared by Examples 1-10 and Comparative Examples 1-4 are shown in Table 2. Compared to the amorphous carbon materials prepared by Comparative Examples 1-4, the amorphous carbon materials prepared by Examples 1-10 of this application show a decrease in both La and Lc, indicating that the disorder and defect levels of the amorphous carbon materials prepared by the method of this application are increasing. Moreover, the first-cycle charge-discharge curves of the amorphous carbon materials prepared by Examples 1-10 and Comparative Examples 1-4 under 0.1C conditions show that the plateau percentage is as shown in Table 2. The plateau percentage of the amorphous carbon material prepared by Comparative Example 1 is 18.10%, while the plateau percentage of the amorphous carbon materials prepared by Examples 1-10 of this application ranges from 63.41% to 71.10%, indicating that the plateau percentage can be further increased.

[0108] Figure 11 Small-angle X-ray scattering (SAXS) images of the amorphous carbon materials in Examples 2-4 and Comparative Example 1 of this application are shown. SAXS was performed on the amorphous carbon materials in Examples 2-4 and Comparative Example 1. This is a multi-scale characterization method for pore structure, and key parameters such as pore distance and fractal dimension can be obtained by fitting the original data. The images are obtained based on the SAXS model. Figure 11 It can be seen that, compared with Comparative Example 1, Examples 2-4 The presence of a more pronounced plateau and higher strength indicates that the amorphous carbon materials of Examples 2-4 have more closed pores, and the radius of many closed pores has increased.

[0109] Figure 12 The amorphous carbon materials of Examples 2-4 and Comparative Example 1 of this application are in... The diagram shows the SAXS intensity and pore volume ratio obtained from N2 adsorption / desorption at the location. Blue represents the pore volume ratio of amorphous carbon materials. The SAXS intensity at a given point represents the proportion of closed-cell pore volume in the total pore volume; red indicates the pore volume of amorphous carbon materials. Figure 12 It can be seen that the closed-cell ratio increased significantly from 43.3% in Comparative Example 1 to over 97% in Examples 2-4, indicating that elemental M-induced crosslinking (especially sulfur-induced crosslinking) played a key role in promoting closed-cell formation. Notably, among these modified carbon materials, Example 3 had the highest closed-cell ratio, reaching 98.5%. This demonstrates that a 1:1 mass ratio of pitch to elemental M can maximize the closed-cell ratio of amorphous carbon materials, thereby improving the performance of sodium-ion batteries.

[0110] In summary, this application discloses a method for preparing amorphous carbon materials with high reversible capacity and high platform ratio. The method involves grinding, drying, and pretreating a precursor material formed by mixing pitch carbon source and elemental M in different proportions to obtain a precursor material (i.e., intermediate) formed by mixing pitch carbon source and elemental M. Then, the precursor material is obtained by high-temperature carbonization, cooling, and passing through a vibrating screen. The preparation method has the following advantages: (1) Low cost: It uses inexpensive and readily available raw materials, and the experimental process is simple to operate; (2) The materials used are simple to prepare and highly operable: It adopts a two-step sintering method, which does not require multi-stage heating and other treatments; (3) The preparation process is simple, mainly reflected in the chemical cross-linking effect of pitch carbon source and M element: chemical cross-linking (chemical cross-linking includes the chemical bonding reaction between pitch base CC and M element at high temperature to form covalent bonds; these formed covalent bonds make it difficult to break and arrange neatly during high temperature carbonization, thus forming a turbulent carbon layer that is more conducive to the diffusion and storage of sodium ions, which is conducive to improving the overall reversible specific capacity of sodium ions) and auxiliary pore formation (pore formation effect, on the one hand, comes from the turbulent carbon layer caused by chemical cross-linking to form sub-nanometer closed pores, on the other hand, comes from the three The formation of the three-dimensional network structure, with some ions bound by the carbon layer, means that a small number of ions can only be removed at higher temperatures. The higher removal temperature is conducive to destroying the carbon layer that is already neatly arranged at low temperatures, thus forming micropores and mesopores with extremely small openings. Both of these pore structures are conducive to the storage of sodium ions on the low potential plateau, which is beneficial to increasing the plateau capacity ratio. (4) The prepared product has high morphological consistency: the synthesized material has uniform particle size, which solves the problem of poor consistency of the precursor of lithium-ion battery / sodium-ion battery negative electrode material in the past. (5) High safety: the synthesis process does not need to be sealed, thus avoiding the problem of excessive self-generated pressure during the reaction process, which meets the green chemistry principle of minimizing safety hazards in the chemical production process. (6) High reaction efficiency: the reaction is easy to occur, and the preparation of amorphous carbon materials can be completed in a short time. It can be seen that the above effects are achieved by simple pretreatment and the results are obvious. The amorphous carbon material prepared in this application has multiple closed pores formed by cross-linking of M element, exhibiting high reversible capacity and high plateau ratio. Its reversible discharge capacity at 0.1C can reach up to 448mAh / g, demonstrating excellent sodium storage capacity and significant potential commercial value, making it suitable for widespread application.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of this technical solution, and all such modifications or substitutions should be covered within the scope of the claims of this application.

Claims

1. An amorphous carbon material, characterized in that, The amorphous carbon material includes element M, which is selected from at least one of sulfur, selenium, or tellurium; the amorphous carbon material contains CM. X -C covalent bond and C-MO X -C covalent bond, wherein x is selected from 1 or 2; the interplanar spacing d of the amorphous carbon material 002 The range is from 0.355 nm to 0.410 nm; The La of the amorphous carbon material is 6.2 nm to 11.0 nm; The Lc of the amorphous carbon material is 1.1 nm to 4.2 nm.

2. The amorphous carbon material according to claim 1, characterized in that, The amorphous carbon material satisfies at least one of the following conditions: (1) The interplanar spacing d of the amorphous carbon material 002 The wavelength ranges from 0.368 nm to 0.395 nm. (2) The La of the amorphous carbon material is 7.9 nm to 10.5 nm; (3) The Lc of the amorphous carbon material is 1.1 nm to 2.1 nm.

3. The amorphous carbon material according to claim 1 or 2, characterized in that, Based on the mass of the amorphous carbon material, the mass percentage of element M is between 1.1% and 5.0%.

4. The amorphous carbon material according to claim 1 or 2, characterized in that, In the C 1s spectrum of the amorphous carbon material, based on the total mass of the amorphous carbon material, the C 1s spectrum... X The C-MO has a C-C covalent bond content of 41% to 49% by mass. X The mass percentage of -C covalent bonds is 39% to 51%.

5. The method for preparing amorphous carbon material according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Mix asphalt and element M to obtain a mixture. Place the mixture in an inert atmosphere, then heat it to the pretreatment temperature and perform pretreatment to obtain an intermediate. The heating rate to the pretreatment temperature is 0.2℃ / min to 30℃ / min. The pretreatment temperature is 80℃ to 600℃. The pretreatment time is 0.5 h to 10 h. Step 2: Place the intermediate in an inert atmosphere, then heat it to the carbonization temperature and perform carbonization treatment to obtain the amorphous carbon material; the heating rate to the carbonization temperature is 0.2℃ / min to 30℃ / min; the carbonization temperature is 800℃ to 2000℃; the carbonization treatment time is 0.5 h to 10 h.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the asphalt to the element M is 1:(0.3~3.0); and / or, The element M is selected from at least one of elemental sulfur, elemental selenium, or elemental tellurium.

7. The preparation method according to claim 5, characterized in that, The inert atmosphere includes nitrogen and / or argon.

8. The preparation method according to claim 7, characterized in that, The inert atmosphere also includes hydrogen, and the volume percentage of hydrogen is 5% to 40% based on the volume of the inert gas.

9. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes the amorphous carbon material according to any one of claims 1 to 4 or the amorphous carbon material obtained by the preparation method according to any one of claims 5 to 8.

10. The negative electrode sheet according to claim 9, characterized in that, The negative electrode sheet and sodium metal sheet are used to prepare a coin cell, which is charged with a constant current of 0.1C to a cutoff voltage of 2.5V. Based on the total capacity of the coin cell, the capacity with a charging potential below 0.1V accounts for 61% to 74%.

11. A sodium-ion battery, characterized in that, Includes the negative electrode sheet as described in claim 9 or 10.

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