Chelating protein derived hard carbon material as well as preparation method and application thereof

Abstract

The invention discloses a chelate protein derived hard carbon material and a preparation method and application thereof, fungus is used as a raw material, phytic acid is used as a phosphorus source, a chelate protein composite precursor is obtained through an in-situ chelation reaction, and a phosphorus-doped hard carbon electrode is further obtained. According to the technical scheme, fungi and phytic acid which are low in price are adopted as raw materials, phosphorus atoms are promoted to be efficiently and uniformly doped in hard carbon through methods of freeze drying, crushing, in-situ chelation reaction and high-temperature pyrolysis carbonization, and the novel hard carbon negative electrode material which is low in cost and high in performance is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a chelated protein derived hard carbon material and a preparation method and application thereof. Background Art

[0002] Sodium-ion batteries have become an indispensable part of the new energy system due to their abundant resources, low cost, excellent high and low temperature performance and safety performance. There are many types of negative electrode materials for sodium-ion batteries, including carbon-based negative electrodes, silicon-based negative electrodes, metal negative electrodes, organic negative electrodes, etc.

[0003] Hard carbon material is the most mature commercialized negative electrode material for sodium ion batteries. It has an open pore structure, high specific surface area and good conductivity. Therefore, compared with other negative electrode materials, hard carbon negative electrode has higher specific capacity, better cycle stability and excellent rate performance.

[0004] However, there are still many problems to be solved in the hard carbon negative electrode, such as low first coulombic efficiency, poor rate performance, and small specific capacity. Scientists have proposed many strategies to solve this series of problems. Among them, heteroatom doping with N, P, S, O, etc. is an important and effective method. As we all know, hard carbon is obtained by pyrolyzing the pretreated precursor under an inert atmosphere. In this process, inappropriate heating rate and carbonization temperature may lead to poor development of the carbon layer or too small interlayer spacing; at the same time, the release of small molecules of the precursor during pyrolysis plus a series of cross-linking reactions will make the hard carbon have abundant pores and defects. However, the too small interlayer spacing in hard carbon is not conducive to the deintercalation of sodium ions, resulting in poor rate performance and small specific capacity of hard carbon. Heteroatom doping is a mature method to control defects and interlayer spacing. Through the doping of heteroatoms, the interlayer spacing of hard carbon is enlarged, and the heteroatoms act as defects in the carbon layer. The conductivity of hard carbon is also improved, thereby improving its rate performance and specific capacity. However, heteroatom doping also has its challenges. How to effectively and successfully dope heteroatoms, how to accurately control the doping amount, and how to clarify the doping mechanism of heteroatoms in the carbon layer are all inevitable problems. Summary of the invention

[0005] In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide a chelated protein-derived hard carbon material and a preparation method and application thereof. The preparation method of the hard carbon material has the advantages of low production cost, simple and efficient doping method, and uniform distribution of heteroatoms in the fungal material. The prepared hard carbon material has the advantages of large interlayer spacing and rich defects, ensuring that it can act as a negative electrode material to enable sodium ion batteries to exhibit excellent electrochemical properties.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] A method for preparing a chelated protein-derived hard carbon material, using fungi as raw materials and phytic acid as a phosphorus source, obtaining a chelated protein composite precursor through an in-situ chelation reaction, and further obtaining a phosphorus-doped hard carbon electrode.

[0008] As a preference, the method comprises the following steps:

[0009] (1) washing the fungi, freeze-drying the washed fungi, and crushing the freeze-dried fungi into a powdery fungal precursor for later use by a crusher;

[0010] (2) taking a powdered fungal precursor and phytic acid, and performing an in-situ chelation reaction in a beaker to obtain a composite precursor after the reaction;

[0011] (3) The composite precursor after the reaction is freeze-dried and crushed again to obtain a powdered chelated protein composite precursor.

[0012] (4) placing the obtained powdered chelating protein composite precursor into a porcelain boat, sending it into a tubular furnace, adjusting the appropriate temperature, and pyrolyzing it to obtain a phosphorus-doped hard carbon material.

[0013] Preferably, in step (1), the fungus is at least one of yeast, black mold, Monascus, Sporothrix, Aspergillus flavus, Auricularia auricula, Shiitake mushroom and artificial fungus.

[0014] Preferably, in step (1), the fungus is an artificial fungus.

[0015] Preferably, in step (1), the fungus is washed with deionized water for 3-5 times, and after filtering the water, the fungus is placed in a refrigerator for freezing until the water in the fungus is completely frozen, and then placed in a freeze dryer for freeze drying for 24 hours.

[0016] Preferably, in step (2), weigh the powdered fungal precursor, take an appropriate amount of deionized water, adjust the solution to a pH of 3-6 with glacial acetic acid, add the weighed powdered fungal precursor and excess phytic acid to the solution, wherein the ratio of phytic acid to deionized water is 1:10-50; and stir the mixture for 4-12 hours.

[0017] Preferably, in step (3), the product after the reaction is filtered, and the obtained composite precursor is placed in a refrigerator for freezing until the liquid in the composite precursor is completely frozen, and then placed in a freeze dryer for freeze drying for 24 hours.

[0018] Preferably, in step (4), a porcelain boat containing a powdered chelating protein composite precursor is placed in a tubular furnace. Under the protection of an argon atmosphere, the tubular furnace is controlled to heat up to 100-400°C at a rate of 5°C / min, and calcined at a constant temperature for 0.5-2h. The tubular furnace is then controlled to heat up to 1000-1300°C at a rate of 5°C / min, calcined at a constant temperature for 0.5-3h, and then cooled to room temperature to obtain a chelating protein-derived hard carbon material.

[0019] A chelated protein derived hard carbon material prepared by the above preparation method.

[0020] An application of the chelated protein derived hard carbon material as described above in sodium ion batteries.

[0021] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0022] 1. In the present invention, low-cost fungi and phytic acid are used as raw materials, and through freeze-drying, crushing, in-situ chelating reaction, and high-temperature pyrolysis carbonization methods, phosphorus atoms are promoted to be efficiently and uniformly doped in hard carbon, thereby obtaining a low-cost, high-performance new hard carbon negative electrode material.

[0023] 2. In the chelated protein-derived hard carbon material prepared by the present invention, fungi provide the basic hard carbon layer, and phytic acid provides the P element for heteroatom doping, which increases the interlayer spacing of the carbon layer and provides abundant defects, has a larger sodium storage space, and has good ionic conductivity.

[0024] 3. The present invention effectively improves the electrochemical performance of sodium ion batteries by applying chelated protein-derived hard carbon materials to sodium ion batteries, and provides a new idea for hard carbon heteroatom doping. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic SEM diagram of the hard carbon material sample prepared in Example 6 of the present invention.

[0026] Figure 2 These are the first three charge and discharge curves of the hard carbon material sample prepared in Example 6 of the present invention.

[0027] Figure 3 These are the first three cycles of the cyclic voltammetry curve of the hard carbon material sample prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below by detailed examples to make the technical solutions and advantages of the present invention clearer. However, the following examples are exemplary and intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0029] Example 1

[0030] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0031] A fungal material is selected as a hard carbon precursor, wherein the fungal material is yeast.

[0032] (1) The yeast was washed with deionized water for 3 times, freeze-dried for 24 hours, and crushed into powder to obtain a powdered fungal precursor for use, which is conducive to sufficient contact and reaction with phytic acid in the next step;

[0033] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0034] (3) After the reaction, the composite precursor is filtered, freeze-dried for 24 hours, taken out and crushed into powder to obtain a powdered chelating protein composite precursor;

[0035] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0036] Example 2

[0037] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0038] The fungal material is selected as the hard carbon precursor, wherein the fungal material is black mold.

[0039] (1) washing black mold with deionized water three times, freeze-drying for 24 hours, and crushing into powder to obtain a powdered fungal precursor for later use;

[0040] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0041] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0042] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0043] Example 3

[0044] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0045] A fungal material is selected as the hard carbon precursor, wherein the fungal material is Monascus purpurogenum.

[0046] (1) washing Monascus with deionized water three times, freeze-drying for 24 h, and crushing into powder to obtain a powdered fungal precursor for later use;

[0047] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0048] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0049] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0050] Example 4

[0051] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0052] A fungal material is selected as the hard carbon precursor, wherein the fungal material is Sporothrix.

[0053] (1) washing the sporothrix with deionized water three times, freeze-drying for 24 hours, and crushing into powder to obtain a powdered fungal precursor for later use;

[0054] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0055] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0056] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0057] Example 5

[0058] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0059] Fungal material is selected as the hard carbon precursor, wherein the fungal material is Aspergillus flavus.

[0060] (1) washing Aspergillus flavus with deionized water three times, freeze-drying for 24 hours, and crushing into powder to obtain a powdered fungal precursor for later use;

[0061] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0062] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0063] (4) The chelated protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0064] Example 6

[0065] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0066] A fungus material is selected as the hard carbon precursor, wherein the fungus material is an artificial fungus.

[0067] (1) washing the artificial fungus with deionized water three times, freeze-drying it for 24 hours, and crushing it into powder to obtain a powdered fungal precursor for later use;

[0068] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0069] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0070] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0071] Example 7

[0072] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0073] A fungal material is selected as a hard carbon precursor, wherein the fungal material is Auricularia auricula.

[0074] (1) Wash the fungus with deionized water three times, freeze-dry it for 24 hours, and grind it into powder to obtain a powdered fungal precursor for later use;

[0075] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0076] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0077] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0078] Example 8

[0079] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0080] Fungal material is selected as the hard carbon precursor, wherein the fungal material is shiitake mushroom.

[0081] (1) Washing shiitake mushrooms with deionized water three times, freeze-drying for 24 hours, and crushing into powder to obtain a powdered fungal precursor for later use;

[0082] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4 to provide an acidic environment for the subsequent chelation reaction, add 17.8 ml of phytic acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the above solution, and stir magnetically for 8 hours to obtain a composite precursor after the reaction;

[0083] (3) filtering the product after the reaction, freeze-drying it for 24 hours, taking it out and crushing it into powder to obtain a powdery chelating protein composite precursor;

[0084] (4) The powdered chelating protein composite precursor was placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature was increased to 400°C at a rate of 5°C / min, and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 1200°C at a rate of 5°C / min, calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0085] Comparative Example 1

[0086] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0087] A fungus material is selected as the hard carbon precursor, wherein the fungus material is an artificial fungus.

[0088] (1) washing the artificial fungus with deionized water three times, freeze-drying it for 24 hours, and crushing it into powder to obtain a powdered fungal precursor for later use;

[0089] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4. Immerse 10 g of powdered fungal precursor into the solution and stir magnetically for 8 h.

[0090] (3) Filter the product in step (2), freeze-dry it for 24 hours, and then grind it into powder;

[0091] (4) The powdered product in step (3) is placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature is increased to 400°C at a rate of 5°C / min, and the mixture is calcined at a constant temperature for 1 hour. The temperature is then increased to 1200°C at a rate of 5°C / min, and the mixture is calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0092] Comparative Example 2

[0093] A method for preparing a chelated protein-derived hard carbon material comprises the following steps:

[0094] A fungus material is selected as the hard carbon precursor, wherein the fungus material is an artificial fungus.

[0095] (1) washing the artificial fungus with deionized water three times, freeze-drying it for 24 hours, and crushing it into powder to obtain a powdered fungal precursor for later use;

[0096] (2) Add glacial acetic acid to 400 ml of deionized water and adjust the solution to a pH of 4, add 17.8 ml of phosphoric acid to the acidic solution, and then immerse 10 g of powdered fungal precursor into the solution and stir magnetically for 8 h to obtain a composite precursor after the reaction;

[0097] (3) The product after the reaction was filtered, freeze-dried for 24 hours, and then crushed into powder;

[0098] (4) The powdered product in step (3) is placed in a porcelain boat, placed in a tubular furnace, and under the protection of an argon atmosphere, the temperature is increased to 400°C at a rate of 5°C / min, and the mixture is calcined at a constant temperature for 1 hour. The temperature is then increased to 1200°C at a rate of 5°C / min, and the mixture is calcined at a constant temperature for 3 hours, and then cooled to room temperature to obtain a hard carbon material sample.

[0099] Scanning electron microscope (SEM) inspection:

[0100] like Figure 1 As shown, it is a scanning electron microscope (SEM) image of the hard carbon material sample of Example 6 of the present invention. Figures a and b are scanning images of different scales of the smooth surface of the chelated protein-derived hard carbon, respectively. It can be seen that the carbon of the hard carbon material in Example 6 is irregular block-shaped and the surface is relatively smooth.

[0101] Performance Testing:

[0102] The hard carbon material samples prepared in the above Examples 1-8 and Comparative Examples 1-2 were made into circular sheets and assembled into button-type half-cells in a glove box with an argon atmosphere for electrochemical testing. The electrolyte was 1M NaPF6 in DME = 100 Vol%, and the diaphragm was Whatman GF / F type. The battery was assembled in the order of positive electrode shell, circular sheet, diaphragm, electrolyte, gasket, shrapnel, and negative electrode shell, and sealed with a packaging machine. After the battery was left to stand for 24 hours, electrochemical tests were carried out using a Xinwei electrochemical workstation and a Chenhua electrochemical workstation. The electrochemical tests were all carried out at 30°C, mainly constant current charge and discharge tests. In the constant current charge and discharge test, the main indicators include cycle life, CV, etc. The long cycle performance of the battery was tested under a current density of 50mA / g. Cyclic voltammetry tests were carried out at a scan rate of 0.1mv / s and a scan range of 0.01-2.

[0103] The performance test results are as follows:

[0104]

[0105]

[0106] Figure 2 The first three charge-discharge curves of the button-type sodium half-cell assembled with chelated protein-derived hard carbon in Example 6 show that the first discharge capacity reached 362 mAh / g, and the first coulombic efficiency was as high as 85.81%.

[0107] Figure 3 These are the first three cycles of the CV curves of the button-type sodium half-cell assembled with the chelated protein-derived hard carbon in Example 6. It can be seen that the first three cycles have a high degree of overlap, demonstrating the high reversibility of the electrochemistry of the chelated protein-derived hard carbon.

[0108] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

[0109] All features described in the description, the attached claims and the drawings are essential features for the invention both individually and in any combination.

Claims

1. A method for preparing a chelated protein-derived hard carbon material, characterized in that: Using fungi as raw materials and phytic acid as phosphorus source, a chelated protein composite precursor is obtained through an in situ chelation reaction, and then a phosphorus-doped hard carbon electrode is further obtained.

2. The method for preparing a chelated protein-derived hard carbon material according to claim 1, characterized in that: The following steps are involved: (1) washing the fungi, freeze-drying the washed fungi, and crushing the freeze-dried fungi into a powdery fungal precursor for later use by a crusher; (2) taking a powdered fungal precursor and phytic acid, and performing an in-situ chelation reaction in a beaker to obtain a composite precursor after the reaction; (3) The composite precursor after the reaction is freeze-dried and crushed again to obtain a powdered chelated protein composite precursor. (4) placing the obtained powdered chelating protein composite precursor into a porcelain boat, sending it into a tubular furnace, adjusting the appropriate temperature, and pyrolyzing it to obtain a phosphorus-doped hard carbon material.

3. The method for preparing a chelated protein-derived hard carbon material according to claim 2, characterized in that: In step (1), the fungus is at least one of yeast, black mold, Monascus, Sporothrix, Aspergillus flavus, Auricularia auricula, Shiitake mushroom and artificial fungus.

4. The method for preparing a chelated protein-derived hard carbon material according to claim 3, characterized in that: In step (1), the fungus is an artificial fungus.

5. The method for preparing a chelated protein-derived hard carbon material according to claim 2, characterized in that: In step (1), the fungus is washed with deionized water for 3-5 times, and after filtering the water, the fungus is placed in a refrigerator for freezing until the water in the fungus is completely frozen, and then placed in a freeze dryer for freeze drying for 24 hours.

6. The method for preparing a chelated protein-derived hard carbon material according to claim 2, characterized in that: In step (2), weigh the powdered fungal precursor, take an appropriate amount of deionized water, adjust the solution to a pH of 3-6 with glacial acetic acid, add the weighed powdered fungal precursor and excess phytic acid to the solution, wherein the ratio of phytic acid to deionized water is 1:10-50; and stir the mixture for 4-12 hours.

7. The method for preparing a chelated protein-derived hard carbon material according to claim 2, characterized in that: In step (3), the product after the reaction is filtered, and the obtained composite precursor is placed in a refrigerator for freezing until the liquid in the composite precursor is completely frozen, and then placed in a freeze dryer for freeze drying for 24 hours.

8. The method for preparing a chelated protein-derived hard carbon material according to claim 2, characterized in that: In step (4), a porcelain boat containing a powdered chelating protein composite precursor is placed in a tubular furnace. Under the protection of an argon atmosphere, the tubular furnace is controlled to heat up to 100-400°C at a rate of 5°C / min, and calcined at a constant temperature for 0.5-2h. The tubular furnace is then controlled to heat up to 1000-1300°C at a rate of 5°C / min, calcined at a constant temperature for 0.5-3h, and then cooled to room temperature to obtain a chelating protein-derived hard carbon material.

9. A chelated protein-derived hard carbon material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the chelated protein derived hard carbon material according to claim 9 in a sodium ion battery.

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