Carbon nanosheet as negative electrode of fast-charging sodium-ion battery and preparation method and application thereof

Abstract

The application discloses a preparation method of a fast-charging type sodium ion battery negative electrode carbon nanosheet, and comprises the following steps: 1) uniformly mixing gluconate, a pore forming agent and N and S containing organic matter, and then performing heat treatment; 2) uniformly grinding the primary carbonization product, and then performing heat treatment again, and then performing washing and vacuum drying, and the method is completed. In the application, the gluconate is used as a carbon source, an oxygen source and an in-situ template agent, and the CO2, SO2 and NO2 gases generated in the hybrid decomposition process of the sulfur source and the alkali metal bicarbonate at high temperature are utilized, so that the interlayer spacing of the carbon is optimized, the prepared negative electrode carbon nanosheet has excellent electrical performance in the sodium ion half battery, the first cycle coulombic efficiency reaches 83.9% at a 0.1C rate, and after sufficient activation, the reversible specific capacity is stabilized at about 340mAh / g at a 0.5C current density, and the cycle can be over 10000 times at a high rate of 20C.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a carbon nanosheet for the negative electrode of a fast-charging sodium-ion battery, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in commercial electronics and electric vehicles due to their high energy density, long cycle life, and lack of memory effect. However, due to the limited and uneven distribution of lithium resources and the poor safety performance of lithium-ion batteries, there is a need to develop other battery systems to meet energy demands. In the periodic table, sodium ions are located in the same group as lithium ions. Sodium-ion batteries (SIBs) share the same rocking chair principle as lithium-ion batteries, allowing them to use similar components. Furthermore, SIBs are characterized by abundant sodium resources (sodium content in the Earth's crust is 440 times that of lithium), fast charging performance, good low-temperature performance, and low cost, making them a strong alternative to lithium-ion batteries.

[0003] The performance of sodium-ion batteries is largely determined by the negative electrode, and current sodium-ion carbon-based negative electrodes are mainly amorphous carbon materials. Amorphous carbon has a highly disordered microstructure, large interlayer spacing, numerous surface defects, and overlapping graphite crystallites forming nanoscale pores, providing a large number of reaction sites for sodium storage. Amorphous carbon materials can be divided into two categories: hard carbon and soft carbon (carbon materials that can be graphitized above 2800℃ are called soft carbon, and those that cannot are called hard carbon). Hard carbon has a closed-cell structure and abundant defect structures, allowing sodium ions to intercalate and deintercalate between its layers, exhibiting an adsorption / intercalation or adsorption / filling mechanism in sodium storage; in addition, its excessively disordered graphite layers lead to poor conductivity. For these reasons, hard carbon suffers from poor rate performance and low initial coulombic efficiency in sodium storage. In contrast, soft carbon has a higher degree of graphitization and better conductivity, and it also exhibits adsorption-desorption behavior on surface defects in sodium storage, making it easier for sodium ions to intercalate and deintercalate during charge and discharge. Therefore, soft carbon has great potential in the application of sodium-ion battery anode materials.

[0004] Although soft carbon exhibits good rate performance, its small interlayer spacing negatively impacts sodium ion kinetics, resulting in low reversible capacity. Current research primarily addresses this issue by increasing the interlayer spacing through heteroatom doping. However, excessive macropore content hinders sodium storage, and numerous side reactions deplete sodium ions, leading to irreversible capacity loss in the first cycle and consequently, a low first-cycle coulombic efficiency. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a fast-charging sodium-ion battery negative electrode carbon nanosheet, which addresses the problems of low initial coulombic efficiency and poor cycle stability of existing heteroatom-doped negative electrode carbon materials.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing carbon nanosheets as the negative electrode of a fast-charging sodium-ion battery includes the following steps:

[0008] 1) Mix gluconate, pore-forming agent and N and S-containing organic matter evenly, and then perform heat treatment to obtain preliminary carbonization products;

[0009] 2) Grind the preliminary carbonization product from step 1) until uniform, perform heat treatment again, and then wash and vacuum dry to obtain the negative electrode carbon nanosheets.

[0010] In the preparation method of this invention, firstly, gluconate is used as a carbon source, oxygen source and in-situ template. After decomposition, sodium oxides or sodium salts such as (NaO, Na2CO3) are produced. These substances act as templates during carbonization. After being washed away, they leave a large number of pores with a pore size distribution between 1.8-5 nm, which are mesoporous. At the same time, the introduction of a large number of pores also increases the specific surface area of ​​the material. Then, during the initial carbonization process, sodium bicarbonate decomposes to produce a large amount of CO2 and H2O, which play an expansion role and increase the specific surface area of ​​the material. Simultaneously, N and S-containing organic compounds (thiourea) will also undergo preliminary decomposition, producing sulfur oxides such as H2S and NH3, as well as gases such as nitrogen oxides and carbon oxides. This causes the pre-carbonized material to expand further, increasing its specific surface area. Furthermore, at high temperatures (second heat treatment), the graphite layer continues to grow, and thiourea and sodium carbonate continue to hybridize and decompose. SOx, NOx, and COx produced by thiourea decomposition will induce the formation of more sites within the pores, creating defects and making the interlayer spacing of carbon more uniform. The large amount of gas will also increase the number of mesopores, further increasing the specific surface area of ​​the material. Moreover, at high temperatures (second heat treatment), SOx and NOx produced by thiourea decomposition will form bonds with carbon during the carbonization process, forming active sites, reducing the adsorption energy of sodium ions, and thus improving the reaction kinetics of sodium ions.

[0011] In some specific embodiments, the gluconate includes, but is not limited to, any one or more of sodium gluconate, potassium gluconate, potassium gluconate, and zinc gluconate.

[0012] In some specific embodiments, the pore-forming agent includes, but is not limited to, alkali metal bicarbonates, including, but not limited to, any one or more of sodium bicarbonate, ammonium bicarbonate, potassium bicarbonate, and calcium bicarbonate.

[0013] In some specific embodiments, the N and S-containing organic compounds include, but are not limited to, any one or more of thiourea, thioamino acids, and hexanoyl thioesters.

[0014] In some specific embodiments, the pore-forming agent contains N and S organic matter in a mass ratio of (0.1-1):(0.1-2):1.

[0015] In some specific embodiments, the heat treatment process conditions in step 1) are: heat treatment temperature of 300-400℃ and time of 0.5-1h.

[0016] In some specific embodiments, the heat treatment process conditions in step 2) are: heat treatment temperature of 600-1000℃ and time of 1-3h; and vacuum drying at a drying temperature of 100-130℃ for 10-12h.

[0017] In some specific embodiments, the mixing in step 1) specifically includes ethanol, with 2-3 ml of ethanol added per gram of gluconate. This step facilitates the uniform dispersion of gluconate, pore-forming agent, and N and S-containing organic matter, providing technical support for obtaining uniformly pore-sized negative electrode carbon nanosheets.

[0018] As part of the same inventive concept, this invention also provides a fast-charging sodium-ion battery negative electrode carbon nanosheet prepared by the aforementioned method. The negative electrode carbon nanosheet has a bulk structure, a particle size of 2-20 μm, a pore size of 1.8-5 nm, and a specific surface area of ​​1000-1700 m². 2 / g, with an average carbon interlayer spacing of 0.41-0.45nm.

[0019] As part of the same inventive concept, this invention also provides the application of the carbon nanosheets of the fast-charging sodium-ion battery negative electrode in sodium-ion batteries.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] 1) The negative electrode carbon nanosheets of this invention utilize gluconate as the carbon source, oxygen source, and in-situ template agent, and leverage the CO2, SO2, and NO2 gases generated during the high-temperature hybridization and decomposition of sulfur source and alkali metal bicarbonate to optimize the interlayer spacing of carbon, thus preparing nitrogen-oxygen-sulfur co-doped mesoporous carbon nanosheets with high specific surface area. These negative electrode carbon nanosheets have a pore size of 1.8-5 nm and a specific surface area of ​​1000-1700 m². 2With an average carbon interlayer spacing of 0.41-0.45 nm, which facilitates sodium ion insertion and extraction, and induced active sites (CS, CO, CN, etc.) generated from oxygen and nitrogen-sulfur sources in the template, this material exhibits excellent electrical performance in sodium-ion half-cells, achieving a first-cycle coulombic efficiency of 83.9% at 0.1C. After sufficient activation, its reversible specific capacity stabilizes at around 340 mAh / g at a current density of 0.5C. Even at a high rate of 20C, it can cycle for over 10,000 cycles, demonstrating both high rate capability and long cycling performance.

[0022] 2) The negative electrode carbon nanosheets of the present invention have a sheet-like and / or block-like structure with a particle size distribution of 2-20 μm. The abundant defects and pores on their surface provide more reaction sites and transport paths for sodium ions. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0024] Figure 1 XRD results of nitrogen, oxygen, and sulfur doped mesoporous negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.75:1 provided in Example 1 of the present invention;

[0025] Figure 2 XRD results of nitrogen, oxygen, and sulfur doped mesoporous negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.5:1 provided in Example 2 of the present invention;

[0026] Figure 3 The XRD results of nitrogen, oxygen, and sulfur doped mesoporous anode carbon nanosheets with sodium gluconate: sodium bicarbonate = 2:1 provided in Comparative Example 1 of this invention are shown.

[0027] Figure 4 SEM image of nitrogen, oxygen, and sulfur doped mesoporous negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.75:1 provided in Example 1 of the present invention;

[0028] Figure 5 SEM image of nitrogen, oxygen, and sulfur doped mesoporous negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.5:1 provided in Example 2 of the present invention;

[0029] Figure 6 The image shows the SEM results of the mesoporous negative electrode carbon nanosheets with sodium gluconate: sodium bicarbonate = 2:1 provided in Comparative Example 1 of this invention.

[0030] Figure 7The BET result diagram of nitrogen, oxygen and sulfur doped mesoporous negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.75:1 provided in Example 1 of the present invention;

[0031] Figure 8 The BET result diagram of nitrogen, oxygen and sulfur doped mesoporous negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.5:1 provided in Example 2 of the present invention;

[0032] Figure 9 The BET results are shown for the mesoporous negative electrode carbon nanosheets with sodium gluconate: sodium bicarbonate = 2:1 provided in Comparative Example 1 of this invention.

[0033] Figure 10 Rate performance diagram of the negative electrode carbon nanosheets with sodium gluconate: thiourea: sodium bicarbonate = 2:0.75:1 provided in Example 1 of the present invention;

[0034] Figure 11 The cycling performance of a sodium-ion battery using carbon nanosheets as the negative electrode material in Example 1 at 20C is shown. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention.

[0036] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0037] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0038] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0039] In the following examples, all materials were of analytical grade. Sodium gluconate and calcium gluconate were purchased from Tianjin Zhonglian Chemical Reagent Co., Ltd., thiourea was purchased from Aladdin Chemical Reagent Co., Ltd., and sodium bicarbonate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0040] Example 1

[0041] This embodiment provides a method for preparing carbon nanosheets as the negative electrode of a fast-charging sodium-ion battery, which includes the following steps:

[0042] 1) Sodium gluconate, sodium bicarbonate and thiourea were mixed in a mass ratio of 2:1:0.75. Then, 2.5 ml of anhydrous ethanol was added for every 1 g of sodium gluconate. The mixture was then ground under an infrared lamp until dry to obtain the precursor.

[0043] 2) The precursor from step 1) is placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min, and then held at that temperature for 0.5 h to obtain the preliminary carbonized product;

[0044] 3) Grind the preliminary carbonization product from step 2) again until uniform, and heat it to 900℃ in an argon atmosphere at a heating rate of 5℃ / min, and then hold it for 2 hours to obtain the pyrolysis product.

[0045] 4) Wash the pyrolysis product from step 3) repeatedly with deionized water until neutral, dry it in a forced-air drying oven, and then dry it in a vacuum oven at 120°C for 10 hours to obtain the negative electrode carbon nanosheets.

[0046] Example 2

[0047] This embodiment provides a method for preparing carbon nanosheets as the negative electrode of a fast-charging sodium-ion battery, which includes the following steps:

[0048] 1) Sodium gluconate, sodium bicarbonate and thiourea were mixed in a mass ratio of 2:1:0.5, and 2.5 ml of anhydrous ethanol was added for every 1 g of sodium gluconate. The mixture was then ground under an infrared lamp until dry to obtain the precursor.

[0049] 2) The precursor from step 1) is placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min, and then held at that temperature for 0.5 h to obtain the preliminary carbonized product;

[0050] 3) Grind the preliminary carbonization product from step 2) again until uniform, and heat it to 900℃ in an argon atmosphere at a heating rate of 5℃ / min, and then hold it for 2 hours to obtain the pyrolysis product.

[0051] 4) Wash the pyrolysis product from step 3) repeatedly with deionized water until neutral, dry it in a forced-air drying oven, and then dry it in a vacuum oven at 120°C for 10 hours to obtain the negative electrode carbon nanosheets.

[0052] Example 3

[0053] This embodiment provides a method for preparing carbon nanosheets as the negative electrode of a fast-charging sodium-ion battery, which includes the following steps:

[0054] This embodiment provides a method for preparing carbon nanosheets as the negative electrode of a fast-charging sodium-ion battery, which includes the following steps:

[0055] 1) Mix calcium gluconate, sodium bicarbonate and thiourea in a mass ratio of 2:1:0.5, then add 2.5 ml of anhydrous ethanol for every 1 g of sodium gluconate, and grind under an infrared lamp until dry to obtain the precursor;

[0056] 2) The precursor from step 1) is placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min, and then held at that temperature for 0.5 h to obtain the preliminary carbonized product;

[0057] 3) Grind the preliminary carbonization product from step 2) again until uniform, and heat it to 900℃ in an argon atmosphere at a heating rate of 5℃ / min, and then hold it for 2 hours to obtain the pyrolysis product.

[0058] 4) Wash the pyrolysis product from step 3) repeatedly with deionized water until neutral, dry it in a forced-air drying oven, and then dry it in a vacuum oven at 120°C for 10 hours to obtain the negative electrode carbon nanosheets.

[0059] Comparative Example 1

[0060] Comparative Example 1 provides a method for preparing carbon nanosheets as the negative electrode of a fast-charging sodium-ion battery, which is basically the same as that in Example 1, except that thiourea is not added. Specifically:

[0061] 1) Mix sodium gluconate and sodium bicarbonate in a mass ratio of 2:1, then add 2.5 ml of anhydrous ethanol for every 1 g of sodium gluconate, and grind until dry under an infrared lamp to obtain the precursor;

[0062] 2) The precursor from step 1) is placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min, and then held at that temperature for 0.5 h to obtain the preliminary carbonized product;

[0063] 3) Grind the preliminary carbonization product from step 2) again until uniform, and heat it to 900℃ in an argon atmosphere at a heating rate of 5℃ / min, and then hold it for 2 hours to obtain the pyrolysis product.

[0064] 4) Wash the pyrolysis product from step 3) repeatedly with deionized water until neutral, dry it in a forced-air drying oven, and then dry it in a vacuum oven at 120°C for 10 hours to obtain the negative electrode carbon nanosheets.

[0065] Performance testing

[0066] This application also characterizes and tests the prepared negative electrode carbon nanosheets, specifically as follows:

[0067] 1) Carbon interlayer spacing

[0068] The negative electrode carbon nanosheets prepared in Examples 1-2 and Comparative Example 1 were tested using XRD diffraction, and the results are as follows: Figure 1 , 2As shown in Figure 3, the (002) peak positions corresponding to the carbon interlayer spacing are 21.15°, 20.89°, 20.03° / 26.12°, and the corresponding interlayer spacings are respectively... Carbon materials without thiourea still have relatively narrow carbon layers, while carbon controlled by hybridization decomposition has more uniform interlayer spacing, and the generated impurity Na2CO3 is easier to wash out.

[0069] 2) Microscopic morphology

[0070] This test used SEM to measure the particle size and microstructure of the negative electrode carbon nanosheets prepared in Examples 1-2 and Comparative Example 1. The results are as follows: Figure 4 , 5 As shown in Figure 6, the negative electrode carbon nanosheets in Example 1 have more surface defects than those in Example 2 and Comparative Example 1. The particle size distribution of the material is also evident. The negative electrode carbon nanosheets in Examples 1 and 2 have smaller particle sizes, with a maximum particle size of approximately 20 μm. Furthermore, the negative electrode carbon nanosheets in Example 1 exhibit a sheet-like structure, while those in Example 2 have a blocky structure. In Comparative Example 1, the maximum particle size is approximately 30 μm, and its negative electrode carbon nanosheets also have a blocky structure. In other words, the particle size of the negative electrode carbon nanosheets in Example 1 is significantly smaller than that in Comparative Example 1. This smaller particle size increases the specific surface area, and the sheet-like structure also provides more contact sites for sodium ions, which is beneficial for improving kinetic performance.

[0071] 3) Physical properties

[0072] This test employed BET full analysis on the negative electrode carbon nanosheets prepared in Examples 1-2 and Comparative Example 1 to investigate their specific surface area and pore size distribution. The results are as follows: Figure 7 , 8 As shown in Figure 9, the specific surface areas of the carbon materials with thiourea content of 0.75, 0.5, and 0 are 1410.7878 m², respectively. 2 / g, 1685.8490m 2 / g, 464.8551m 2 / g; its pore size is mostly distributed between 1.8-5nm, belonging to mesoporous materials.

[0073] 4) Element content

[0074] The nitrogen, oxygen, and sulfur content of the negative electrode carbon nanosheets prepared in Examples 1-2 and Comparative Example 1 was analyzed using EA. The results are shown in Table 1.

[0075] Table 1 shows the content of N, C, S, and O in the negative electrode carbon nanosheets of each embodiment and comparative example.

[0076] Example 1 3.34 85.38 1.45 6.34 Example 2 0.81 91.63 0.87 5.15 Example 3 2.53 89.06 1.24 5.87 Comparative Example 1 0.15 76.90 0.43 9.92

[0077] As can be seen from the data in Table 1, the nitrogen and sulfur content in the negative electrode carbon nanosheets of this application increases with the increase of thiourea content. The doping amount of the negative electrode carbon nanosheets in Example 1 is: N: 3.34 wt%, S: 1.45 wt%, O: 6.34 wt%. In Comparative Example 1, O mainly comes from Na2CO3 or its decomposition products.

[0078] 5) Electrical performance analysis

[0079] This test examines the electrical properties of the negative electrode carbon nanosheets prepared in Examples 1-2 and Comparative Example 1. The specific test methods are as follows:

[0080] Electrodes were prepared using the negative electrode carbon nanosheets obtained in Examples 1, 2, and Comparative Example 1. Specifically, the slurry mass ratio was: negative electrode carbon nanosheets: binder (PVDF): conductive agent (Ketjen Black) = 8:1:1. An appropriate amount of N-methylalkylpyrrolidone was added, and the mixture was coated onto copper foil. After drying, it was cut into electrode sheets with a diameter of 12 mm. Sodium sheets were used as counter electrodes, glass fibers as separators, and 1 M NaPF6 in DIGLYME as electrolyte to assemble CR2032 type button batteries. The test voltage range was 0.01-2.8V, and the test temperature was 25℃. The test methods were: initial charge-discharge test at 0.1C, rate tests at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 20C, and 0.1C, and cycle tests at 20C. The results are shown in Table 2. Figure 10 and Figure 11 As shown:

[0081] Table 2. First-efficiency and rate performance (mAh / g) of sodium-ion batteries using carbon nanosheets as negative electrodes in each embodiment and comparative example.

[0082]

[0083] As shown in Table 2, the nitrogen, oxygen, and sulfur-doped mesoporous carbon nanosheets prepared in Examples 1-3 all exhibit superior material properties compared to Comparative Example 1. Figure 10 As shown, the nitrogen, oxygen, and sulfur-doped mesoporous carbon nanosheets obtained in Example 1 have the best performance, with a first-cycle coulombic efficiency of 83.9%, and the results in the rate test are slightly higher than those in Examples 2-3.

[0084] from Figure 11 As can be seen from the data, the negative electrode carbon nanosheets in Example 1 can still cycle 10,000 times at a high rate of 20C. This indicates that the material synthesized through in-situ pore formation and hybrid decomposition has a high specific surface area, suitable interlayer spacing, number of mesopores and active sites, which enable the material to exhibit excellent rate performance and stability in sodium-ion batteries.

[0085] In contrast, the negative electrode carbon nanosheets in Comparative Example 1 did not contain thiourea and did not form a good morphology. Although they are also mesoporous materials, the number of mesopores is significantly smaller than that in Examples 1-2, which is not conducive to the reaction and storage of sodium ions, and therefore the electrochemical performance is poor.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. The application of carbon nanosheets as a negative electrode in fast-charging sodium-ion batteries, characterized in that, The carbon nanosheets for the fast-charging sodium-ion battery negative electrode are obtained by the following method, including the following steps: 1) Mix gluconate, pore-forming agent and N and S-containing organic matter evenly, and then perform heat treatment to obtain preliminary carbonization products; 2) The preliminary carbonization product from step 1) is ground uniformly, heat-treated again, then washed and vacuum-dried to obtain the negative electrode carbon nanosheets; wherein the negative electrode carbon nanosheets are in block or sheet structure, with a particle size of 2-20 μm, a pore size of 1.8-5 nm, and a specific surface area of ​​1000-1700 m². 2 / g, with an average carbon interlayer spacing of 0.41-0.45 nm; wherein the pore-forming agent is one or more of sodium bicarbonate, ammonium bicarbonate, potassium bicarbonate, and calcium bicarbonate; and the N and S-containing organic matter is one or more of thiourea, thioamino acids, and hexanoyl thioester.

2. The application according to claim 1, characterized in that, The gluconate is one or more of sodium gluconate, potassium gluconate, potassium gluconate, and zinc gluconate.

3. The application according to claim 2, characterized in that, The pore-forming agent contains N and S organic matter in a mass ratio of (0.1-1):(0.1-2):

1.

4. The application according to claim 1, characterized in that, The heat treatment process conditions described in step 1) are: heat treatment temperature of 300-400℃ and time of 0.5-1h.

5. The application according to claim 1, characterized in that, The heat treatment process conditions in step 2) are as follows: the heat treatment temperature is 600-1000℃ and the time is 1-3h; the vacuum drying is carried out at a drying temperature of 100-130℃ for 10-12h.

6. The application according to claim 1, characterized in that, The mixing described in step 1) involves adding ethanol solvent, with 2-3 ml of ethanol added per gram of gluconate.

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