Mn single atom loaded hard carbon nanosheet and preparation method and application thereof
By uniformly loading Mn single atoms onto a hard carbon matrix and using green and easily recyclable molten salt as a template, high-performance hard carbon nanosheets were prepared, solving the problems of complex synthesis and high cost of sodium-ion battery anode materials, and achieving excellent electrochemical performance and environmentally friendly production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-29
- Publication Date
- 2026-03-31
AI Technical Summary
The synthesis process of existing sodium-ion battery anode materials is complex and costly, and hard carbon materials have shortcomings in terms of conductivity, initial coulombic efficiency and cycle stability.
Using green and easily recyclable molten salt as a template, Mn-ZIF8 precursor was synthesized by wet chemical method. After being mixed with polyacrylonitrile, potassium chloride and sodium chloride, it was calcined at high temperature to prepare hard carbon nanosheets loaded with Mn single atoms. The uniform distribution of Mn single atoms on the hard carbon matrix was used to improve the electrochemical performance of the material.
The prepared hard carbon nanosheets exhibit excellent cycle stability and high rate performance, have high specific capacity, are environmentally friendly and have low production costs, making them suitable as anode materials for sodium-ion batteries.
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Figure CN121769082A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a hard carbon nanosheet loaded with Mn single atoms, its preparation method and application, belonging to the field of sodium-ion battery material technology. Background Technology
[0002] Against the backdrop of global energy transition and sustainable development, sodium-ion batteries, due to their abundant sodium resources, low cost, and relatively good safety, are gradually becoming a promising energy storage technology. Theoretically, sodium-ion batteries have advantages comparable to lithium-ion batteries, but they still face a series of significant challenges in practical applications, especially in the development of anode materials. Existing commercial graphite anode materials, due to their small interlayer spacing, struggle to effectively bind larger sodium ions. Therefore, researchers have been continuously exploring novel anode materials in recent years to improve the overall performance of sodium-ion batteries.
[0003] Hard carbon materials, due to their large interlayer spacing and abundant amorphous structure, possess high theoretical capacity and show great potential for sodium ion storage. However, there is still considerable room for improvement in key performance indicators such as conductivity, initial coulombic efficiency, and cycling stability. Researchers have discovered that the electrochemical performance of hard carbon materials can be effectively improved by introducing heteroatoms or by controlling the nanostructure.
[0004] It is worth noting that, compared with traditional non-metallic element doping methods, this method has a clear metal-nitrogen-carbon (MN) profile. x -C) configuration metal single atoms can alter the local charge distribution of carbon materials, exhibiting strong affinity for alkali metal ions and low migration resistance. Furthermore, by dispersing individual metal atoms on a support material, the amount of metal used can be significantly reduced while maintaining high selectivity, thus improving material utilization efficiency. This method provides a new approach for developing high-performance energy storage materials. Among these, Mn, due to its abundant oxidation states and good electrochemical activity, has become a popular candidate in single-atom material research. However, the synthesis process of single-atom materials is complex, potentially generating harmful substances or causing environmental pollution, and production costs are high. Moreover, designing support materials with good single-atom dispersion capabilities is also a challenge. Therefore, given this background, it is necessary to develop a green, environmentally friendly, simple, and effective method to prepare Mn single-atom-loaded hard carbon anode materials, thereby improving the performance and extending the lifespan of sodium-ion batteries, and making a positive contribution to the development of energy storage and conversion technologies. Summary of the Invention
[0005] To address the issues of complex synthesis processes and high costs in existing sodium-ion battery anode materials technologies, this application provides a green, environmentally friendly, simple, and effective method for preparing hard carbon nanosheets loaded with Mn single atoms. Utilizing a green and easily recyclable molten salt as a template, Mn single atoms are uniformly loaded onto a hard carbon matrix, successfully constructing a structurally stable and high-performance hard carbon material. When used as an anode material in sodium-ion batteries, these Mn-loaded hard carbon nanosheets exhibit excellent cycle stability and high-rate performance, along with high specific capacity, making a positive contribution to the development of energy storage and conversion technologies and demonstrating broad application prospects.
[0006] The technical solution adopted in this application is as follows:
[0007] According to one aspect of this application, a method for preparing hard carbon nanosheets loaded with Mn single atoms is provided, comprising the following steps:
[0008] S1. Mix an aqueous solution containing manganese and zinc sources with an aqueous solution containing 2-methylimidazole and react to obtain the precursor.
[0009] S2. Grind the mixture containing the precursor, polyacrylonitrile, potassium chloride, and sodium chloride from step S1 to obtain intermediate product powder.
[0010] S3. In an inactive atmosphere, the intermediate product powder from step S2 is calcined to obtain the hard carbon nanosheets loaded with Mn single atoms.
[0011] Optionally, in step S1, the reaction conditions include: stirring for 10–60 min and then standing for 18–32 h.
[0012] Optionally, step S1 also includes centrifuging, washing, and drying the product after the reaction.
[0013] Optionally, in step S1, the molar ratio of 2-methylimidazole to manganese in the manganese source and zinc in the zinc source is 1:(0.008-0.016):(0.08-0.13).
[0014] Optionally, in step S1, the content of 2-methylimidazole in the mixture after mixing the aqueous solution containing manganese and zinc sources with the aqueous solution containing 2-methylimidazole is 1 to 10 mmol / mL.
[0015] Optionally, in step S1, the aqueous solution containing 2-methylimidazole also contains a surfactant;
[0016] The molar ratio of 2-methylimidazole to surfactant is 1:0.00008 to 0.00012.
[0017] Optionally, the surfactant is selected from hexadecyltrimethylammonium bromide.
[0018] Optionally, the manganese source is a soluble manganese salt, and the zinc source is a soluble zinc salt.
[0019] Optionally, the manganese source is manganese nitrate.
[0020] Optionally, the zinc source is zinc acetate.
[0021] Optionally, in step S2, the grinding time is 20 to 60 minutes.
[0022] Optionally, in step S2, the weight ratio of the precursor, polyacrylonitrile, potassium chloride, and sodium chloride is 1:(1-1.5):(9-11):(6-8).
[0023] Optionally, in step S3, the calcination conditions include: heating the intermediate product powder to 650-750°C and holding it at that temperature for 0.5-1.5 hours, and then heating it to 1150-1150°C and holding it at that temperature for 3-5 hours.
[0024] Optionally, the heating rate I is 2.5–3.5 °C / min. -1 .
[0025] Optionally, the heating rate II is 4.5–5.5 °C / min. -1 .
[0026] According to another aspect of this application, a hard carbon nanosheet loaded with Mn single atoms prepared by the above preparation method is provided, wherein the hard carbon nanosheet loaded with Mn single atoms comprises hard carbon nanosheets.
[0027] The surface of the hard carbon nanosheets is uniformly distributed with several protruding hollow carbon frames.
[0028] The hollow carbon framework is ZIF-8(Zn) with Mn single atoms uniformly distributed on its surface;
[0029] There are interconnected channels between the several protruding hollow carbon frames.
[0030] The surface of the hollow carbon frame is covered with thin carbon sheets.
[0031] According to another aspect of this application, the application of hard carbon nanosheets loaded with Mn single atoms prepared by the above preparation method as a negative electrode material in sodium-ion batteries is also provided.
[0032] The beneficial effects that this application can produce include:
[0033] This application provides a method for preparing hard carbon nanosheets loaded with Mn single atoms. A molten salt mixture of potassium chloride and sodium chloride is used as a template, which is then uniformly mixed with polyacrylonitrile and Mn-ZIF8 and calcined to 1100℃ to obtain the target product, Mn-PHCS. Mn-ZIF8 not only introduces Mn single atoms, inducing rapid sodium storage kinetics, but also acts as a pore-forming agent utilizing the high-temperature Zn evaporation characteristic, resulting in hard carbon nanosheets that expose a large number of active sites. This preparation method uses a green and recyclable molten salt, is simple in process, environmentally friendly, and low in cost, while also achieving a high product yield, showing great application potential. Attached Figure Description
[0034] Figure 1 This is an X-ray diffraction pattern of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0035] Figure 2 This is a field emission scanning electron microscope image of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0036] Figure 3 This is a transmission electron microscope (TEM) image of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0037] Figure 4 This is a high-resolution transmission electron microscope image of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0038] Figure 5 This is a selected area diffraction electron microscope image of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0039] Figure 6 This is a spherical aberration electron microscope image of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0040] Figure 7 This is an energy dispersive X-ray spectral surface scan of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0041] Figure 8 This is a high-resolution X-ray photoelectron spectrum of Mn 2p of the Mn-PHCS hard carbon material prepared in the embodiments of this application.
[0042] Figure 9 This is a high-resolution X-ray photoelectron spectrum of N1s of the Mn-PHCS hard carbon material prepared in the embodiments of this application.
[0043] Figure 10 This is a CV curve of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0044] Figure 11This is the initial constant current charge-discharge curve of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0045] Figure 12 Electrochemical rate performance diagram of Mn-PHCS hard carbon material prepared in the embodiments of this application.
[0046] Figure 13 This is a graph showing the low-current electrochemical cycling performance of the Mn-PHCS hard carbon material prepared according to the embodiments of this application.
[0047] Figure 14 This is a graph showing the high-current electrochemical cycling performance of the Mn-PHCS hard carbon material prepared in the embodiments of this application. Detailed Implementation
[0048] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0049] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0050] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.
[0051] According to one embodiment of this application, a method for preparing hard carbon nanosheets loaded with Mn single atoms includes the following steps:
[0052] First, Mn-ZIF8 was synthesized by mixing manganese and zinc sources with 2-methylimidazole under specific conditions, and preparing the Mn-ZIF8 precursor via a wet chemical method. Second, the synthesized Mn-ZIF8 was mixed with polyacrylonitrile, and a blended molten salt of potassium chloride and sodium chloride was added as a template. After thorough grinding, a uniform mixed powder was formed. Then, the powder was placed in a ceramic boat and calcined at a target temperature under an inactive atmosphere at a constant heating rate. Finally, after cooling, Mn single-atom-loaded hard carbon nanosheets were obtained. This method not only uses a green and easily recyclable molten salt, making it environmentally friendly, but also fully utilizes the abundant oxidation states and excellent electrochemical activity of Mn by uniformly embedding Mn single atoms into a hard carbon matrix. The prepared hard carbon material exhibits high specific capacity, excellent conductivity, and outstanding cycle stability, showing broad application prospects.
[0053] According to one embodiment of this application, the preparation method of hard carbon nanosheets loaded with Mn single atoms specifically includes the following steps:
[0054] (1) At room temperature, a certain amount of manganese nitrate tetrahydrate and zinc acetate dihydrate were dissolved in ultrapure water to form solution A, and a certain amount of 2-methylimidazole and hexadecyltrimethylammonium bromide were dissolved in ultrapure water to form solution B. The two solutions were then mixed and stirred for a few minutes, allowed to stand, and finally centrifuged and dried to obtain the Mn-ZIF8 precursor;
[0055] (2) Mix and grind a certain amount of potassium chloride, sodium chloride, polyacrylonitrile and Mn-ZIF8 for 30 min;
[0056] (3) The mixed powder was loaded into a ceramic boat and kept at 700℃ for 1 hour under an argon atmosphere, then heated to 1100℃ for 4 hours. After cooling to room temperature, the resulting sample was named Mn-PHCS.
[0057] Example 1
[0058] (1) Preparation of precursors
[0059] 1.5 mmol of manganese nitrate tetrahydrate and 13.8 mmol of zinc acetate dihydrate were dissolved in 50 mL of ultrapure water. The solution was then rapidly poured into 50 mL of ultrapure water containing 120 mmol of 2-methylimidazole and 0.012 mmol of hexadecyltrimethylammonium bromide. After stirring for 15 min at room temperature, the mixture was allowed to stand for 24 h. The resulting pale pink precipitate was then centrifuged and washed several times with ultrapure water and ethanol. Finally, the precipitate was dried at 70 °C for 12 h to obtain the product, which was named Mn-ZIF8 as a precursor.
[0060] (2) Preparation of intermediate products
[0061] Mix 4.35g potassium chloride, 3.27g sodium chloride, 0.6g polyacrylonitrile and 0.46g Mn-ZIF8 and grind for 30 minutes to obtain a uniformly mixed powder of intermediate product.
[0062] (3) Calcination to obtain hard carbon nanosheets loaded with Mn single atoms
[0063] The mixed powder was loaded into a porcelain boat and placed in a tube furnace. Under an argon atmosphere, it was first heated at 3°C for 3 minutes. -1 The temperature was increased to 700℃ and held for 1 hour, then increased at 5℃ per minute. -1 The heating rate was increased to 1100℃ and maintained for 4 hours. After cooling to room temperature, the resulting target hard carbon material product, namely hard carbon nanosheets loaded with Mn single atoms, was named Mn-PHCS.
[0064] Test Example 1: Morphology and Phase Analysis
[0065] Morphology and phase analysis were performed on the Mn-PHCS hard carbon material obtained in Example 1:
[0066] The XRD pattern of Mn-PHCS is as follows: Figure 1 As shown, it exhibits significant amorphous carbon characteristics, with two peaks appearing near 24° and 43° corresponding to the (002) and (100) crystal planes of the carbon material, respectively. The scanning electron microscope image of Mn-PHCS is shown below. Figure 2 As shown, the carbon framework formed by Mn-ZIF8 is uniformly distributed on the hard carbon nanosheets formed by polyacrylonitrile. Notably, there are partially interconnected channels between the protruding carbon frameworks, which suggests that this facilitates rapid electron flow. Transmission electron microscopy (TEM) images of Mn-PHCS are shown below. Figure 3 As shown, hollow carbon frameworks are encapsulated by thin carbon sheets and interconnected. High-resolution transmission electron microscopy (TEM) images of Mn-PHCS are shown below. Figure 4 As shown, the pseudo-graphite microcrystalline fringes exhibit long-range disorder and short-range order. The selected area diffraction electron microscope (SEM) pattern of Mn-PHCS is shown below. Figure 5 As shown, the diffuse scattering halo indicates that no crystalline Mn material has formed in the material. The aberration-corrected electron microscopy image of Mn-PHCS is shown below. Figure 6 As shown, numerous isolated bright spots are displayed, further confirming the presence of atomically dispersed Mn material in Mn-PHCS. The energy-dispersive X-ray spectral surface scan of Mn-PHCS is shown below. Figure 7 As shown, C, N, O, and Mn elements are uniformly distributed in Mn-PHCS. The high-resolution X-ray photoelectron spectrum of Mn 2p in Mn-PHCS is shown below. Figure 8 As shown, Mn 2+ (641.8 eV, 652.8 eV) and Mn 3+ The double peaks (643.2 eV, 654.3 eV) indicate that Mn 2+ and Mn 3+ The proportions were 41.53% and 58.47%, respectively, indicating that Mn in Mn-PHCS is mainly in the +3 valence state and metallic manganese is absent. The high-resolution X-ray photoelectron spectrum of N1s in Mn-PHCS is as follows: Figure 9 As shown, it can be divided into five different spectral bands, namely pyridine N (398.7 eV, 28.53%), MN x (399.4 eV, 17.02%), pyrrole N (401.1 eV, 27.47%), graphite N (402.0 eV, 20.72%), and N oxide (404.0 eV, 6.26%), of which MN x The existence of species implies that the atomically dispersed Mn atoms are coordinated with N atoms.
[0067] Test Example 2 Performance Testing Process
[0068] The Mn-PHCS hard carbon material powder sample obtained in Example 1 was assembled into a button-type sodium-ion battery. The specific steps are as follows: The active material, conductive agent (Super P), and binder (carboxymethyl cellulose) were ground uniformly at a mass ratio of 8:1:1, and a small amount of deionized water was added to prepare a slurry. The slurry was coated onto a 12mm diameter copper foil, and then kept at 70°C for 24 hours in a vacuum drying oven. Finally, the electrode sheets were assembled into a sodium-ion button battery in a glove box. The working electrode was the pre-prepared electrode sheet (approximately 0.8-1.0 mg / cm³ of active material). -2 The sodium metal sheet is used as the counter electrode, the diaphragm is a glass fiber membrane, and the electrolyte is 1M NaPF6 DIGLYME.
[0069] Electrochemical performance tests were conducted on the fabricated button-type sodium-ion battery:
[0070] CV curve diagram as follows Figure 10 As shown, a pair of sharp redox peaks can be clearly observed, located at 0.01 V and 0.1 V, respectively, corresponding to Na. + Intercalation and deintercalation occur in the plateau region below 0.1V. Notably, the first-round curve does not overlap with other curves in the 0.1-1.1V range, exhibiting a very weak irreversible reduction peak, which is attributed to the formation of the SEI film. Overall, the cubic curves show high overlap, indicating that Mn-PHCS has good electrochemical stability.
[0071] The initial constant current charge-discharge curve is as follows: Figure 11 As shown, the discharge curve of the sample can be observed to consist of a ramp region above 0.1V and a plateau region below 0.1V. Mn-PHCS at 0.05Ag -1 The corresponding ICE at the current density is 76.53%.
[0072] Electrochemical rate performance such as Figure 12 As shown, Mn-PHCS exhibits excellent rate performance at 0.02, 0.05, 0.10, 0.20, 0.50, 1.00, 2.00, 5.00, and 10.00 Ag. -1 The average charging capacities under the following conditions were 369, 345, 327, 310, 285, 260, 227, 166, and 124 mAh g, respectively. -1 After the rate test, the current density returned to 0.02 A g. -1 At that time, the reversible specific capacity can reach 397mAh g. -1 .
[0073] The low-current electrochemical cycling performance and the high-current electrochemical cycling performance are respectively as follows: Figure 13 and Figure 14As shown, this demonstrates that Mn-PHCS possesses excellent cyclic stability.
[0074] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for preparing a hard carbon nanoplatelet loaded with Mn monatomic atoms, characterized in that, The method comprises the following steps: S1, mixing and reacting an aqueous solution containing a manganese source and a zinc source with an aqueous solution containing 2-methylimidazole to obtain a precursor; S2, grinding a mixture containing the precursor in step S1, polyacrylonitrile, potassium chloride and sodium chloride to obtain an intermediate product powder; S3, calcining the intermediate product powder in step S2 in an inactive atmosphere to obtain the Mn single atom loaded hard carbon nanosheet.
2. The production method according to claim 1, characterized by, In step S1, the reaction conditions include stirring for 10-60 min and standing for 18-32 h.
3. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of 2-methylimidazole to manganese in the manganese source and zinc in the zinc source is 1:(0.008-0.016):(0.08-0.13).
4. The method of claim 1, wherein, In step S1, the aqueous solution containing 2-methylimidazole also contains a surfactant; The molar ratio of 2-methylimidazole to surfactant is 1:0.00008-0.00012; Preferably, the surfactant is selected from cetyltrimethylammonium bromide; Preferably, the manganese source is a soluble manganese salt and the zinc source is a soluble zinc salt.
5. The method of producing according to claim 1, wherein In step S2, the grinding time is 20-60 min.
6. The method of claim 1, wherein, In step S2, the weight ratio of the precursor, polyacrylonitrile, potassium chloride and sodium chloride is 1:(1-1.5):(9-11):(6-8).
7. The preparation method according to claim 1, characterized in that, In step S3, the calcination conditions include heating the intermediate product powder to 650-750℃ for 0.5-1.5 h, and then heating to 1150-1150℃ for 3-5 h.
8. The preparation method according to claim 7, characterized in that, The rate of the temperature increase I is 2.5-3.5°C / min -1 ; Preferably, the rate of said temperature increase II is comprised between 4.5 and 5.5°C min -1 .
9. The Mn single atom supported hard carbon nanoplatelets prepared by the method of any one of claims 1 to 8, characterized in that, The Mn single atom loaded hard carbon nanosheet comprises a hard carbon nanosheet; The surface of the hard carbon nanosheet is uniformly distributed with a plurality of protruding hollow carbon frames; The hollow carbon frame is ZIF-8(Zn) with Mn single atoms uniformly distributed on the surface; The plurality of protruding hollow carbon frames have interconnected channels therebetween; The surface of the hollow carbon frame is wrapped by a thin carbon sheet.
10. Application of the Mn single atom loaded hard carbon nanosheet prepared by the preparation method of any one of claims 1-8 as a negative electrode material in a sodium ion battery.