A carbon material loaded with tin single atoms and clusters, and its preparation method and application

Abstract

This invention provides a method for preparing a carbon material loaded with tin single atoms and clusters. The method includes the following steps: dispersing a carbon source, a nitrogen source, a fluorine source, and a tin source in a solvent at a mass ratio of 1:(1-5):(4-8):(0.01-0.3), stirring and drying to obtain a precursor; and heat-treating the precursor to obtain the carbon material. The carbon matrix exhibits a composite morphology of two-dimensional nanosheets and zero-dimensional nanospheres, the tin single atoms display a Sn-N3 configuration, and the tin clusters exhibit a planar quadrilateral structure composed of four tin atoms. In this invention, the carbon material loaded with tin single atoms and clusters exhibits excellent specific capacity and rate capability. In this invention, in addition to the introduction of pseudocapacitive active sites by nitrogen / fluorine heteroatoms, the tin single atoms and clusters have high sodium storage activity, and they exert a synergistic effect when coexisting. Furthermore, the composite morphology of the carbon matrix increases the exposed area of ​​the active sites, improves the charge migration rate, and enhances the sodium storage performance of the anode material.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode material technology, specifically to a carbon material loaded with tin single atoms and clusters, its preparation method, and its application. Background Technology

[0002] The large-scale application of new energy sources urgently requires the development of electrochemical energy storage technologies. Among them, lithium-ion batteries have received widespread attention and significant development due to their outstanding performance in energy density, cycle performance, and power output. However, lithium metal is highly sensitive to oxygen and moisture, easily reacting with water in the electrolyte to produce hydrogen gas, posing a safety hazard. Furthermore, the volume change of lithium metal also presents an issue, potentially leading to electrode structure cracking and decreased charge / discharge efficiency.

[0003] Sodium is much more abundant and widely distributed in the Earth's crust than lithium, making the raw materials for sodium-ion batteries more readily available and sustainable. Due to sodium's resource and price advantages over lithium, sodium-ion batteries have become one of the strongest competitors to lithium-ion batteries in large-scale energy storage and low-speed electric vehicles. However, sodium-ion battery technology is still under development. Regarding the selection of anode materials for sodium-ion batteries, compared to metal oxides / sulfides, silicon / tin, etc., carbon materials are easier to adjust in structure and composition and have higher ionic / electronic conductivity. However, the specific capacity and rate performance of existing carbon anode materials still need improvement. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a carbon material loaded with tin single atoms and clusters, its preparation method, and its applications. By designing a carbon material loaded with SAMs of different configurations, the active sites of the carbon anode material are enriched, the conductivity of the carbon material is improved, and a sodium-ion carbon anode material with excellent specific capacity and rate performance is obtained. The specific invention content is as follows:

[0005] In a first aspect, the present invention provides a method for preparing a carbon material loaded with tin single atoms and clusters, the method comprising the following steps:

[0006] S1. Disperse carbon source, nitrogen source, fluorine source and tin source in a solvent in a mass ratio of 1:(1~5):(4~8):(0.01~0.3), stir and dry to obtain the precursor;

[0007] S2. The precursor is subjected to heat treatment at 650-850°C to obtain the carbon material.

[0008] Optionally, in step S1, the carbon source is one or more of aniline, dopamine, xanthine, glucose, and lignin;

[0009] The nitrogen source is urea, melamine, or dinitrileamine;

[0010] The fluorine source is perfluorotetradecanoic acid, polyvinylidene fluoride, polytetrafluoroethylene, or ammonium fluoride.

[0011] The tin source is one of hydrated stannous dichloride and hydrated stannous tetrachloride;

[0012] The solvent is ultrapure water or anhydrous ethanol.

[0013] Optionally, the carbon source is one or more of aniline, dopamine, and xanthine;

[0014] The nitrogen source is urea or melamine;

[0015] The fluorine source is polyvinylidene fluoride, polytetrafluoroethylene, or ammonium fluoride.

[0016] The tin source is either hydrated stannous dichloride or hydrated stannous tetrachloride.

[0017] Optionally, the carbon source is xanthine;

[0018] The nitrogen source is melamine;

[0019] The fluorine source is polytetrafluoroethylene;

[0020] The tin source is hydrated stannous dichloride;

[0021] The solvent is anhydrous ethanol.

[0022] Optionally, in step S1, the mass ratio of the carbon source, nitrogen source, fluorine source and tin source is 1:(2-4):(5-7):(0.02-0.2).

[0023] Optionally, the mass ratio of the carbon source, nitrogen source, fluorine source and tin source is 1:3:6:0.1.

[0024] Optionally, in step S2, the heat treatment temperature is 700–800°C.

[0025] Optionally, the heat treatment employs a stepped heating method, including:

[0026] First heating stage: 4-10℃ min -1 The heating rate was increased from room temperature to 450℃, and the temperature was maintained at 360℃ and 450℃ for 1 hour and 2 hours, respectively.

[0027] Second heating stage: 1–3℃ min -1 The heating rate was increased from 450℃ to 650-850℃, and the temperature was held at the highest temperature for 1 hour.

[0028] In a second aspect, the present invention provides a carbon material loaded with tin single atoms and clusters obtained by the preparation method described in the first aspect above.

[0029] Thirdly, the present invention provides an application of carbon materials loaded with tin single atoms and clusters obtained by the preparation method described in the first aspect above in sodium-ion batteries.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] This invention provides a method for preparing carbon materials loaded with tin single atoms and clusters. The method involves thoroughly mixing carbon, nitrogen, fluorine, and tin sources in a specific mass ratio, followed by high-temperature heat treatment. This allows tin single atoms and clusters to be loaded onto a nitrogen-fluorine co-doped carbon matrix, forming a carbon material for sodium-ion batteries. The carbon matrix exhibits a composite morphology of two-dimensional nanosheets and zero-dimensional nanospheres. The tin single atoms display a Sn-N3 configuration, and the tin clusters exhibit a planar quadrilateral structure composed of four tin atoms. In this invention, the carbon material loaded with tin single atoms and clusters exhibits excellent specific capacity and rate performance. In addition to the introduction of pseudocapacitive active sites by nitrogen / fluorine heteroatoms, the tin single atoms and clusters possess high sodium storage activity, exhibiting a synergistic effect when coexisting. Furthermore, the composite morphology of the carbon matrix increases the exposed area of ​​the active sites, improves the charge migration rate, and enhances the sodium storage performance of the anode material. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A flowchart of the preparation method of carbon materials loaded with tin single atoms and clusters provided in the embodiments of the present invention is shown;

[0034] Figure 2 The following is a SEM image of a carbon material loaded with tin single atoms and clusters provided in an embodiment of the present invention;

[0035] Figure 3 The XRD pattern of the carbon material loaded with tin single atoms and clusters provided in the embodiments of the present invention is shown.

[0036] Figure 4 The image shows a scanning transmission electron microscope (STEM) image of a carbon material loaded with tin single atoms and clusters provided in an embodiment of the present invention.

[0037] Figure 5The synchrotron radiation X-ray absorption spectrum and fitting results of the carbon material loaded with tin single atoms and clusters provided in the embodiments of the present invention are shown.

[0038] Figure 6 The following diagram shows the performance of a sodium-ion half-cell assembled from carbon materials loaded with tin single atoms and clusters, as provided in an embodiment of the present invention.

[0039] Figure 7 The figure shows the theoretical calculation results of the adsorption capacity of the carbon material loaded with tin single atoms and clusters for sodium ions provided in the embodiments of the present invention;

[0040] Figure 8 The specific capacity test results of the carbon material loaded with tin single atoms and clusters provided in the embodiments of the present invention are shown. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0042] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0043] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0044] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0045] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] Before providing a detailed description of the carbon material loaded with tin single atoms and clusters, its preparation method, and its applications provided by this invention, it is necessary to explain the relevant technologies as follows:

[0047] In their research on improving the electrochemical performance of carbon anode materials, the inventors discovered that heteroatom doping (such as N, P, S, and F) is an effective strategy, proven through experiments and theory to facilitate the introduction of active sites into the carbon matrix. Furthermore, single-atom metal (SAM) doped carbon materials have also attracted increasing attention. Mn-N4 single atoms can provide additional sodium ion adsorption sites, thereby improving specific capacity. For example, Cr single atoms can modulate the solid electrolyte interphase (SEI) on the carbon electrode surface, thus improving the initial coulombic efficiency (ICE).

[0048] Based on the above research, this invention aims to introduce metal single atoms and metal clusters into a non-metallic heteroatom-doped carbon matrix, designing a carbon material loaded with SAMs of different configurations. This enriches the active sites of the carbon anode material, improves its conductivity, and yields a sodium-ion carbon anode material with excellent specific capacity and rate performance. Specifically, the carbon anode material provided by this invention is a carbon material with tin single atoms and tin clusters loaded on a nitrogen-fluorine co-doped carbon matrix. Introducing Sn, a high-capacity active material, into the carbon anode material can increase sodium storage capacity and improve the battery's energy density. Furthermore, tin has excellent electronic conductivity; introducing tin into the carbon anode material can improve the material's conductivity and enhance the battery's discharge performance.

[0049] Although tin can improve the energy storage performance of carbon anode materials, problems such as tin volume expansion and reaction with the electrolyte still exist, which may lead to capacity decay and reduced battery cycle life. Therefore, in practical applications, these problems need to be solved through reasonable design and structural control to achieve the best performance improvement effect of tin introduction into carbon anode materials. To this end, the following is a detailed introduction to a carbon material loaded with tin single atoms and clusters, its preparation method, and its applications. The specific implementation details are as follows:

[0050] In a first aspect, the present invention provides a method for preparing a carbon material loaded with tin single atoms and clusters. Figure 1 A flowchart illustrating the preparation method of carbon materials loaded with tin single atoms and clusters according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the method includes the following steps:

[0051] S1. Disperse carbon source, nitrogen source, fluorine source and tin source in a solvent in a mass ratio of 1:(1~5):(4~8):(0.01~0.3), stir and dry to obtain the precursor;

[0052] S2. The precursor is subjected to heat treatment at 650-850°C to obtain the carbon material.

[0053] In practice, the above preparation process can be further broken down into the following steps:

[0054] Prepare raw materials: Prepare carbon source, nitrogen source, fluorine source, and tin source. The carbon source can be one or more of high-purity aniline, dopamine, xanthine, glucose, and lignin; the nitrogen source can be amine compounds, such as urea, melamine, or dinitrileamine; the fluorine source can be perfluorotetradecanoic acid, polyvinylidene fluoride, polytetrafluoroethylene, or ammonium fluoride; the tin source can be one of hydrated stannous dichloride and hydrated stannous tetrachloride.

[0055] Mixing raw materials: The selected carbon source, nitrogen source, fluorine source, and tin source are weighed in a certain proportion and uniformly dispersed in an appropriate amount of solvent for mixing. Considering the solvent's solubility / dispersion ability on the above carbon source, nitrogen source, fluorine source, and tin source, ultrapure water or anhydrous ethanol is selected as the solvent, and a ball mill or other equipment is used for mixing to ensure the uniform distribution of each component. After stirring and drying, the mixed raw material (precursor) is obtained.

[0056] High-temperature heat treatment: The mixed raw materials are placed in a high-temperature resistant container and subjected to high-temperature heat treatment under an inert atmosphere. The heating temperature and time are adjusted according to specific requirements. It should be noted that this invention adopts a stepped heating mode for heating treatment. During the heating process, the carbon source, nitrogen source, and fluorine source in the raw materials undergo polymerization, pyrolysis, gasification, and reaction. Holding at different temperatures allows different reactants to fully soften or polymerize. The slow heating rate allows the carbon precursor to fully react with the dopant during the pyrolysis and escape of the dopant, ultimately forming a fluorine- and nitrogen-doped carbon matrix material. At the same time, the tin source is loaded on the nitrogen- and fluorine co-doped carbon matrix in the form of tin single atoms and clusters.

[0057] In practical implementation, the material performance can be further optimized by adjusting the ratio and formulation of tin content with other components. This invention, through detailed experimental research and optimization, controls the mass ratio of carbon source, nitrogen source, fluorine source, and tin source within the range of 1:(1-5):(4-8):(0.01-0.3) to avoid the negative impact of excessive tin content on material performance due to expansion during sodium formation, and to prevent excessively low tin content from causing a decrease in electronic conductivity, reducing lithium intercalation kinetics and electrochemical capacity.

[0058] The carbon material loaded with tin single atoms and clusters prepared by the above-mentioned technical solution provided by the present invention is specifically composed of a nitrogen-fluorine co-doped carbon matrix, tin single atoms and tin clusters loaded on the carbon matrix. Specifically, the carbon matrix has a composite morphology of two-dimensional nanosheets and zero-dimensional nanospheres, the tin single atoms exhibit a Sn-N3 configuration, and the tin clusters exhibit a planar quadrilateral structure composed of four tin atoms. In the present invention, the carbon anode material loaded with tin single atoms and clusters exhibits excellent specific capacity and rate performance in the electrolyte. In the present invention, in addition to the introduction of pseudocapacitive active sites by nitrogen / fluorine heteroatoms, tin single atoms and clusters have high sodium storage activity, and the two exert a synergistic effect when coexisting. Furthermore, the carbon matrix with a composite morphology increases the exposed area of ​​the active sites, improves the charge migration rate, and enhances the sodium storage performance of the anode material.

[0059] In some embodiments, the present invention disperses a certain proportion of carbon source, nitrogen source, fluorine source, and tin source in a solvent, and then stirs and dries to obtain a precursor. In this invention, the type of carbon source is highly important, taking into account the content of heteroatoms and the types of functional groups, so as to achieve better integration with other substances during mixing and heat treatment. Therefore, the preferred carbon source is one or more of aniline, dopamine, and xanthine. In this invention, considering the solubility of nitrogen and fluorine sources in the solvent, and the overall control of the initial reaction temperature and decomposition temperature during heat treatment, the preferred nitrogen source is one of urea and melamine; the preferred fluorine source is one of polyvinylidene fluoride, polytetrafluoroethylene, and ammonium fluoride. In this invention, the preferred tin source includes one of hydrated stannous dichloride and hydrated stannous tetrachloride. The preferred ratio of carbon source, nitrogen source, fluorine source, and tin source is 1:(2-4):(5-7):(0.02-0.2).

[0060] In some embodiments, the present invention provides a more preferred set of raw material ratios, namely, the carbon source is xanthine; the nitrogen source is melamine; the fluorine source is polytetrafluoroethylene; the tin source is hydrated stannous chloride; and the solvent is anhydrous ethanol. The mass ratio of the carbon source, nitrogen source, fluorine source, and tin source is 1:3:6:0.1.

[0061] In some embodiments, the high-temperature heat treatment temperature is 650℃~850℃, preferably 700℃~800℃. This invention considers that temperature has a significant impact on the morphology and structure of intermediates formed during the heat treatment process, thereby affecting the structure and composition of carbon materials. Therefore, based on extensive experimental research and empirical summarization, this invention concludes that a stepped heating method is preferably adopted for the specific heat treatment process. This includes: a first heating stage: at 4~10℃ min... -1 The heating rate was increased from room temperature to 450℃, and the temperature was maintained at 360℃ and 450℃ for 1 hour and 2 hours respectively; the second heating stage was carried out at a rate of 1-3℃ per minute. -1The heating rate was increased from 450℃ to 650-850℃, and the temperature was held at the highest temperature for 1 hour.

[0062] As an example, the stepped heating method includes: First heating stage: 5℃ min... -1 The heating rate was increased from room temperature to 450℃, and the temperature was maintained at 360℃ and 450℃ for 1 hour and 2 hours respectively; the second heating stage was carried out at a rate of 2℃ / min. -1 The temperature was increased from 450℃ to 800℃, and held at the highest temperature for 1 hour.

[0063] Secondly, the present invention provides a carbon material loaded with tin single atoms and clusters obtained by the preparation method described in the first aspect above. The carbon material loaded with tin single atoms and clusters provided by the present invention improves the specific capacity and rate capability of the carbon material loaded with tin single atoms and clusters under the combined effect of the tin single atoms and clusters.

[0064] Thirdly, the present invention provides an application of carbon materials loaded with tin single atoms and clusters obtained by the preparation method described in the first aspect above in sodium-ion batteries.

[0065] To enable those skilled in the art to more clearly understand the present invention, the following embodiments are provided to illustrate in detail a carbon material loaded with tin single atoms and clusters, its preparation method, and its application.

[0066] Example 1

[0067] Step 1: Mix xanthine, melamine, polytetrafluoroethylene, and stannous dichloride hydrate in anhydrous ethanol at a mass ratio of 1:3:6:0.1. Stir well and then dry.

[0068] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperature was increased to 360℃, 450℃, and the highest temperature, and held for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters.

[0069] Example 2

[0070] Step 1: Mix xanthine, melamine, polytetrafluoroethylene and stannous dichloride hydrate in a ratio of 1:3:6:0.05.

[0071] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1The temperatures were maintained at 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the ratio of reactants.)

[0072] Example 3

[0073] Step 1: Mix xanthine, melamine, polytetrafluoroethylene and stannous dichloride hydrate in a ratio of 1:3:6:0.2.

[0074] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperatures were maintained at 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the ratio of reactants.)

[0075] Example 4

[0076] Step 1: Mix dopamine, melamine, polytetrafluoroethylene and stannous dichloride hydrate in a ratio of 1:3:6:0.1.

[0077] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperatures were maintained at 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the carbon source).

[0078] Example 5

[0079] Step 1: Mix xanthine, melamine, polytetrafluoroethylene and stannous dichloride hydrate in a ratio of 1:4:4:0.1.

[0080] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperatures were maintained at 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the ratio of reactants.)

[0081] Example 6

[0082] Step 1: Mix xanthine, melamine, polytetrafluoroethylene, and stannous dichloride hydrate in anhydrous ethanol at a mass ratio of 1:3:6:0.1. Stir well and then dry.

[0083] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperatures were maintained at 360°C, 450°C, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 700°C, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the highest heat treatment temperature).

[0084] Example 7

[0085] Step 1: Mix xanthine, melamine, polytetrafluoroethylene, and stannous dichloride hydrate in anhydrous ethanol at a mass ratio of 1:3:6:0.1. Stir well and then dry.

[0086] Step 2: Perform heat treatment on the above precursor, with the heating rate fixed at 8°C / min. -1 The materials were heated to 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin metal. A rapid heating rate is detrimental to the complete reaction of the precursors, reducing the content of non-metallic heteroatoms on the carbon matrix, thus hindering the formation of single-atom structures. Furthermore, rapid heating also leads to the growth of tin clusters, making it easier to form large crystals. Therefore, rapid heating is not conducive to the preparation of carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the heating rate of the heat treatment).

[0087] Comparative Example 1

[0088] Step 1: Mix xanthine, melamine, polytetrafluoroethylene, and stannous dichloride hydrate in anhydrous ethanol at a mass ratio of 1:3:6:0.01. Stir well and then dry.

[0089] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperatures were maintained at 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the ratio of reactants.)

[0090] Comparative Example 2

[0091] Step 1: Mix xanthine, melamine, polytetrafluoroethylene, and stannous chloride hydrate in anhydrous ethanol at a mass ratio of 1:3:6:0.3. Stir well and then dry.

[0092] Step 2: Heat treat the above precursor at 450℃ or below for 5 minutes. -1 , 2℃ min above 450℃ -1 The temperatures were maintained at 360℃, 450℃, and the highest temperature for 1 hour, 2 hours, and 1 hour, respectively. This stepped heating method was used to reach the highest heat treatment temperature of 800℃, followed by natural cooling to obtain carbon materials loaded with tin single atoms and clusters. (The only difference from the preparation method in Example 1 is the ratio of reactants.)

[0093] Figure 2 SEM images of carbon materials loaded with tin single atoms and clusters provided in embodiments of the present invention are shown, wherein (a), (b), and (c) are SEM images of carbon materials loaded with tin single atoms and clusters prepared in Examples 1-3, respectively; and (d) and (e) are SEM images of carbon materials loaded with tin single atoms and clusters prepared in Comparative Examples 1-2, respectively. Figure 2 As shown, by observing the SEM images of the carbon materials prepared in Examples 1-3 and Comparative Examples 1-2, it was found that their microstructures all exhibited the morphology of wrinkled carbon nanosheets. In Comparative Example 2, larger, uniform spherical particles were found.

[0094] Figure 3 The XRD pattern of the carbon material loaded with tin single atoms and clusters provided in the embodiments of the present invention is shown, as follows: Figure 3 As shown, XRD tests were performed on the carbon materials prepared in Examples 1-3 and Comparative Examples 1-2. Tin metal peaks appeared in the carbon materials obtained in Example 3 and Comparative Example 2, indicating that the tin salt in the precursor was in excess.

[0095] Figure 4 The following are scanning transmission electron microscope (STEM) images of carbon materials loaded with tin single atoms and clusters provided in the embodiments of the present invention, wherein (a-b), (c-d), and (e-f) are carbon materials of Examples 2, 1, and 3, respectively.

[0096] like Figure 4 As shown, the distribution of tin in the carbon materials obtained in Examples 1-3 was observed using a high-angle annular dark-field scanning transmission electron microscope with spherical aberration correction. It was found that the carbon materials contained a large number of atomically small tin particles and tin clusters smaller than 1 nm. This phenomenon was consistent in both carbon nanosheets and carbon nanospheres. Observation of the cluster regularity revealed that as the initial tin salt feed ratio increased, the cluster size became larger, and the lattice fringes gradually became more pronounced.

[0097] To further analyze the configuration of tin single atoms and clusters, Figure 5 The XANES spectra of carbon materials loaded with tin single atoms and clusters provided in the embodiments of the present invention are shown. (a) and (b) show the K-edge X-ray absorption near-edge structure (XANES) spectra of Sn in the carbon materials loaded with tin single atoms and clusters prepared in Examples 1 and 2, respectively. (c) and (d) show the fitting results of the extended X-ray absorption fine structure spectra in the R space of the carbon materials of Examples 2 and 1, respectively. Figure 5 As shown, the K-edge X-ray absorption near-edge structure (XANES) spectra of the carbon materials Sn from Examples 1 and 2 were tested. By converting the spectra to Fourier transform and R-space, it can be seen that... The peak at this location is Sn-N (without phase correction), indicating the presence of tin single atoms in the material. However, by comparing it with Sn foil, [the following text appears to be incomplete and requires further context: "in"] The peak corresponds to the Sn-Sn metallic bond. This indicates that tin single atoms and clusters are present in the carbon materials of both Example 2 and Example 1. Further observation of the intensity changes of the two peaks revealed that the single-atom peak was weaker and the metallic bond peak was stronger in Example 1. The average coordination number of Sn-N in the carbon materials of both Example 2 and Example 1 is close to 3, and the sum of the coordination numbers of the metallic bonds is also close to 3.

[0098] Further, Figure 6 The following diagram illustrates the performance of a sodium-ion half-cell assembled from carbon materials loaded with tin single atoms and clusters, as provided in an embodiment of the present invention. Figure 6 The half-cell performance of the carbon materials in Examples 1-3 and Comparative Examples 1-2 was evaluated. Specifically, the carbon material in Example 1 was evaluated at half-cell values ​​of 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 Ag. -1 The average specific capacities at the specified times were 399.6, 341.5, 306.1, 261.6, 235.6, 214.5, 188.4, 167.4, and 140.1 mAh g, respectively. -1 After the rate test, it returned to 0.05A g. -1 At that time, the reversible specific capacity can still reach 362.2 mAh g. -1 The superiority of the comparative examples demonstrates that the tin single-atom and cluster carbon materials provided by this invention have high specific capacity and excellent rate performance.

[0099] Figure 7The figure shows the theoretical calculation results of the adsorption capacity of the carbon material loaded with tin single atoms and clusters for sodium ions provided in the embodiments of the present invention. In the figure, (a) and (b) are the theoretical calculation results of the adsorption capacity of the carbon material containing only tin single atoms and the carbon material containing only tin clusters for a sodium ion, respectively; (c) is the theoretical calculation result of the adsorption capacity of the carbon material after introducing tin clusters on the basis of (a) for a sodium ion; (d) is the theoretical calculation result of the adsorption capacity of the carbon material after introducing tin single atoms on the basis of (b) for a sodium ion; as shown in the figure. Figure 7 As shown, theoretical calculations yielded adsorption energies of -2.16 eV for a single sodium ion for carbon materials containing only tin single atoms and -2.53 eV for carbon materials containing only tin clusters. This indicates that both tin single atoms and tin clusters can serve as additional adsorption energies for sodium. + The active sites are concentrated in tin, and the enhancement effect of tin clusters is more significant. When both tin single atoms and clusters are introduced simultaneously, the adsorption capacity of sodium ions in this carbon material is improved, with adsorption energies reaching -2.56 and -2.64 eV, respectively. This indicates that single atoms and clusters have a synergistic effect, which is beneficial to improving sodium storage capacity. Among them, Example 1 shows the highest specific capacity.

[0100] Figure 8 The specific capacity test results of the carbon material loaded with tin single atoms and clusters provided in the embodiments of the present invention are shown, such as... Figure 8 As shown, the half-cell performance of Example 1 was evaluated under ether and ester conditions. The carbon material of Example 1 was tested at 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 Ag. -1 The average specific capacities at the specified times were 363.3, 343.1, 324.5, 303.6, 288.7, 272.5, 251.4, 233.3, and 206.3 mAh g, respectively. -1 After the rate test, it returned to 0.05Ag. -1 At that time, the reversible specific capacity can still reach 360.2 mAh g. -1 This demonstrates that the tin single-atom and cluster carbon materials provided by this invention can achieve superior rate performance after optimizing the electrolyte.

[0101] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0102] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0103] The foregoing has provided a detailed description of a carbon material loaded with tin single atoms and clusters, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a carbon material loaded with tin single atoms and clusters, characterized in that, The method includes the following steps: S1. Disperse carbon source, nitrogen source, fluorine source and tin source in a solvent with a mass ratio of 1:(2~4):(5~7):(0.02~0.2), stir and dry to obtain the precursor; S2. The precursor is subjected to heat treatment at 650 °C~850 °C to obtain the carbon material; In step S1, the carbon source is one or more of aniline, dopamine, xanthine, glucose, and lignin. The nitrogen source is urea, melamine, or dinitrileamine; The fluorine source is perfluorotetradecanoic acid, polyvinylidene fluoride, polytetrafluoroethylene, or ammonium fluoride. The tin source is one of hydrated stannous dichloride and hydrated stannous tetrachloride; The solvent is ultrapure water or anhydrous ethanol; In step S2, the heat treatment employs a stepped heating method, including: First heating stage: 4~10 °C min -1 The heating rate was increased from room temperature to 450 °C, and the temperature was maintained at 360 °C and 450 °C for 1 h and 2 h, respectively. Second heating stage: 1~3 °C min -1 The heating rate was increased from 450 °C to 650~850 °C, and the temperature was held at the highest temperature for 1 h.

2. The method for preparing carbon materials loaded with tin single atoms and clusters according to claim 1, characterized in that, The carbon source is one or more of aniline, dopamine, and xanthine; The nitrogen source is urea or melamine; The fluorine source is polyvinylidene fluoride, polytetrafluoroethylene, or ammonium fluoride. The tin source is either hydrated stannous dichloride or hydrated stannous tetrachloride.

3. The method for preparing carbon materials loaded with tin single atoms and clusters according to claim 1 or 2, characterized in that, The carbon source is xanthine; The nitrogen source is melamine; The fluorine source is polytetrafluoroethylene; The tin source is hydrated stannous dichloride; The solvent is anhydrous ethanol.

4. The method for preparing carbon materials loaded with tin single atoms and clusters according to claim 1, characterized in that, The mass ratio of the carbon source, nitrogen source, fluorine source and tin source is 1:3:6:0.

1.

5. The method for preparing carbon materials loaded with tin single atoms and clusters according to any one of claims 1-3, characterized in that, In step S2, the heat treatment temperature is 700 °C to 800 °C.

6. A carbon material loaded with tin single atoms and clusters obtained by the preparation method according to any one of claims 1-5.

7. The application of a carbon material loaded with tin single atoms and clusters obtained by any of the preparation methods described in claims 1-5 in a sodium-ion battery.

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