Double-carbon packaged selenium tin sulfide sodium ion battery flexible negative electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to a dual-carbon packaged selenium tin sulfide sodium ion battery flexible negative electrode material and a preparation method thereof. In the material, selenium tin sulfide (SnSSe) is encapsulated in a double-carbon layer formed by hollow carbon spheres (HC) and flexible nitrogen-doped carbon nanofibers (NCF). The preparation method of the material comprises the following steps: firstly, preparing hollow carbon spheres; then, generating SnSSe on the inner wall of the hollow carbon sphere through hydrothermal treatment induction to obtain SnSe (at) HC; and finally, carrying out electrostatic spinning to obtain a flexible SnSe coated HC-electrostatic spinning nanofiber membrane, and carrying out carbonization treatment to obtain the SnSe coated HC-NCF composite fiber membrane. By means of the special double-carbon-layer structure, the volume expansion of SnSSe in the sodium storage process can be more effectively limited, dissolution of polysulfide and polyselenide is greatly limited, the cycle stability of the battery is improved, and then the sodium storage stability of SnSSe is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of battery materials, specifically relating to a flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide and its preparation method. Background Technology

[0002] Sodium-ion batteries share a similar mechanism with lithium-ion batteries, and given the abundance and low cost of sodium resources, they possess immense potential for large-scale energy storage and represent a competitive new energy storage system. However, due to the significantly larger ionic radius of sodium ions compared to lithium ions, graphite, a traditional anode material for lithium-ion batteries, cannot be directly used as the anode material for sodium-ion batteries. Tin disulfide (SnS2), with its high theoretical specific capacity (1136 mAh·g), offers a solution. -1 SnS2, with its low cost and large interlayer spacing, has the potential to become a negative electrode material for sodium-ion batteries. However, its low inherent conductivity and significant volume expansion (approximately 324%) during sodium storage result in poor rate performance and cycle stability, greatly affecting its practical application in sodium-ion batteries.

[0003] To improve the stability and conductivity of SnS2 during sodium storage, current research has demonstrated the preparation of tin selenide sulfide (SnSSe) composites by replacing sulfur in SnS2 with heteroatoms (Se). The introduction of heteroatoms (Se) can improve the conductivity of SnS2, increase its interlayer spacing, and enhance its rate performance. However, like SnS2, SnSSe still suffers from significant volume expansion and the dissolution of polysulfides and polyselenides during cycling, resulting in poor long-term cycling stability.

[0004] To address these issues, research has found that SnSSe can be encapsulated within carbon materials. Carbon materials can both limit the volume expansion of SnSSe and reduce the dissolution of polysulfides and polyselenides. However, the carbon layers prepared using current technologies are typically porous or open structures, which have very limited effectiveness in limiting the volume expansion of SnSSe and reducing the dissolution of polysulfides and polyselenides. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible negative electrode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide (SnSSe) and its preparation method, which addresses the aforementioned deficiencies. The special dual-carbon layer structure can more effectively limit the volume expansion of SnSSe during sodium storage and greatly limit the dissolution of polysulfides and polyselenides, thereby improving the cycle stability of the battery and thus improving the sodium storage stability of SnSSe.

[0006] The technical solution of this invention is as follows:

[0007] A flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide is disclosed. In this material, SnSSe is encapsulated in a dual-carbon layer composed of hollow carbon spheres (HC) and flexible nitrogen-doped carbon nanofibers (NCF). SnSSe is uniformly generated and distributed on the inner wall of the hollow carbon spheres to form SnSSe@HC. SnSSe@HC is completely wrapped inside the flexible nitrogen-doped carbon nanofibers to form a flexible SnSSe@HC-NCF composite fiber membrane with a dual-carbon layer structure.

[0008] The special structure of the dual-carbon encapsulation can effectively improve the volume expansion and polysulfide / selenide dissolution problems of SnSSe when used as a negative electrode material in sodium-ion batteries.

[0009] Furthermore, in the SnSSe@HC-NCF composite fiber membrane, the diameter of the hollow carbon spheres is 100-600 nm.

[0010] Furthermore, in the SnSSe@HC-NCF composite fiber membrane, the diameter of the flexible nitrogen-doped carbon nanofibers is 200-2000 nm.

[0011] Furthermore, the SnSSe content in the SnSSe@HC-NCF composite fiber membrane is 20wt%-90wt%.

[0012] A method for preparing the dual-carbon encapsulated tin selenide flexible anode material for sodium-ion batteries includes the following steps:

[0013] First, hollow carbon spheres were prepared using the template method.

[0014] Then, based on the abundant oxygen-containing functional groups on the inner surface of the hollow carbon spheres, Sn source, S source, Se source and reducing agent are induced to generate SnSSe on the inner wall of HC through hydrothermal treatment, resulting in SnSSe@HC.

[0015] Finally, the obtained SnSSe@HC was dispersed in an N,N-dimethylformamide solution containing polyacrylonitrile and polyvinylpyrrolidone to obtain an electrospinning precursor solution; the electrospinning precursor solution was electrospinned to obtain a flexible SnSSe@HC-electrospinned nanofiber membrane.

[0016] The obtained flexible SnSSe@HC-electrospun nanofiber membrane was carbonized to obtain SnSSe@HC-NCF composite fiber membrane.

[0017] Furthermore, the specific steps for preparing the dual-carbon encapsulated tin selenide flexible anode material for sodium-ion batteries are as follows:

[0018] (1) Preparation of hollow carbon spheres:

[0019] First, resorcinol, formaldehyde, ammonia, and tetraethyl orthosilicate were added to an ethanol and water solvent system and stirred at room temperature to obtain phenolic resin / silica composite microspheres; resorcinol and formaldehyde together served as carbon precursors.

[0020] Then, the obtained phenolic resin / silica composite microspheres were calcined under a nitrogen atmosphere to obtain carbon / silica microspheres.

[0021] Finally, the carbon / silica microspheres were etched with sodium hydroxide solution under heating conditions to remove the silica and obtain hollow carbon spheres.

[0022] (2) Preparation of SnSSe@HC:

[0023] The hollow carbon spheres obtained in step (1) are dispersed in an aqueous solution composed of Sn source, S source, Se source and reducing agent, and hydrothermally treated at 160-200℃ for 8-12h to prepare SnSSe@HC.

[0024] (3) Preparation of SnSSe@HC-NCF composite fiber membrane:

[0025] First, the SnSSe@HC obtained in step (2) is dispersed in an N,N-dimethylformamide (DMF) solution containing a mixed polymer of polyacrylonitrile and polyvinylpyrrolidone, and then ultrasonically and uniformly stirred to obtain an electrospinning precursor solution.

[0026] Then, the obtained electrospinning precursor solution was electrospinned to obtain a flexible SnSSe@HC-electrospinned nanofiber membrane.

[0027] Finally, the obtained flexible SnSSe@HC-electrospun nanofiber membrane was carbonized under a nitrogen protective atmosphere to obtain SnSSe@HC-NCF composite fiber membrane.

[0028] Furthermore, the Sn source is at least one of sodium stannate, stannous chloride, or stannous chloride; the S source is at least one of thiourea, sodium sulfide, or thioacetamide; the Se source is at least one of selenium oxide, sodium selenate, or selenium powder; and the reducing agent is sodium borohydride or hydrazine hydrate.

[0029] Furthermore, in step (1), the mass ratio of formaldehyde: resorcinol: ammonia: water: tetraethyl orthosilicate: ethanol is 1:2:(5-20):(40-70):(20-40):(300-400).

[0030] Furthermore, the stirring time in step (1) is 12-24h; the calcination temperature is 600-900℃, the calcination time is 2-4h, and the heating rate of the calcination is 5℃ / min; the concentration of the sodium hydroxide solution is 1-4mol / L, and the etching temperature is 60-100℃.

[0031] Furthermore, in step (2), the mass ratio of hollow carbon sphere: Sn source: S source: Se source: reducing agent: water is 1:(5-10):(1-2):(2-4):(5-10):(500-600).

[0032] Furthermore, in step (3), the mass ratio of polyacrylonitrile to polyvinylpyrrolidone in the mixed polymer is 1:1; wherein the weight-average molecular weight of the polyacrylonitrile used is 150,000 and the weight-average molecular weight of polyvinylpyrrolidone is 1,300,000.

[0033] The mass ratio of the SnSSe@HC mixed polymer is (0.1-1):1, and the concentration of the mixed polymer in N,N-dimethylformamide solution is 10%-30% (w / v).

[0034] Furthermore, in step (3), the voltage for electrospinning is 15-30kV, the spinning distance is 10-20cm, and the flow rate of the electrospinning precursor liquid is 0.1-10mL / h.

[0035] The carbonization treatment temperature is 600-900°C. o C, the carbonization treatment time is 2-4 hours, and the heating rate of the carbonization treatment is 1℃ / min. Nitrogen is used as the inert gas.

[0036] The SnSSe@HC-NCF composite fiber membrane prepared above can be used directly as a negative electrode material for sodium-ion batteries without the need for coating. The prepared flexible electrode requires no binder, conductive agent, or metal current collector, effectively simplifying the negative electrode material preparation steps and reducing manufacturing costs. The SnSSe@HC-NCF composite fiber membrane, as a negative electrode material for sodium-ion batteries, exhibits high discharge specific capacity, good rate performance, and excellent cycle stability.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. This invention creatively encapsulates SnSSe within a double carbon layer composed of hollow carbon spheres and electrospun carbon nanofibers using a hydrothermal method combined with electrospun carbon nanofibers, constructing an electrode material with excellent flexibility. The highly reactive SnSSe is encapsulated within a double carbon layer composed of size-tunable hollow carbon spheres and flexible nitrogen-doped carbon nanofibers. This unique double carbon layer structure effectively limits the volume expansion of SnSSe during sodium storage and restricts the dissolution of polysulfides and polyselenides. The highly flexible nitrogen-doped carbon nanofibers provide a good conductive network, ensuring rapid electron / ion transport during sodium storage and effectively improving electrochemical reaction kinetics.

[0039] 2. The prepared electrode material eliminates the need for current collectors, conductive agents, and binders, effectively simplifying the electrode fabrication process and improving battery energy density. Furthermore, based on the electrode material's excellent flexibility, it can be used as an electrode material for flexible energy storage devices, showing promising application prospects.

[0040] 3. The SnSSe@HC-NCF composite fiber membrane prepared by this invention has a novel structure, good conductivity, high reactivity, and stable electrochemical performance. As a sodium-ion battery anode material, it exhibits high discharge specific capacity, excellent rate performance, and cycle stability. When used as a sodium-ion battery anode material, at 2 A·g... -1 It exhibits a current density greater than 450 mAh·g after 500 cycles. -1 The discharge specific capacity is at 10 A·g -1 It still has a capacity of over 300 mAh·g at current density -1 The specific discharge capacity. Attached Figure Description

[0041] Figure 1 This is a scanning electron microscope (SEM) image of SnSSe@HC obtained in Example 1.

[0042] Figure 2 The image shows a SEM image of the SnSSe@HC-NCF composite fiber membrane obtained in Example 1.

[0043] Figure 3 The image shows the X-ray diffraction pattern of the SnSSe@HC-NCF composite fiber membrane obtained in Example 1.

[0044] Figure 4 The image shows the X-ray photoelectron spectrum of the SnSSe@HC-NCF composite fiber membrane obtained in Example 1.

[0045] Figure 5 The rate performance of the SnSSe@HC-NCF composite fiber membrane obtained in Example 6 is shown.

[0046] Figure 6The cycling stability of the SnSSe@HC-NCF composite fiber membrane obtained in Example 6. Detailed Implementation

[0047] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0048] The specific operation method for assembling a sodium-ion battery using the SnSSe@HC-NCF composite fiber membrane as the negative electrode material is as follows:

[0049] The SnSSe@HC-NCF composite fiber membrane described in this invention is cut into 12mm negative electrode sheets for later use; then, a CR2025 button cell is used for battery assembly. The positive electrode of the battery uses metallic sodium, the separator uses a glass fiber membrane with a pore size of 22μm, and the electrolyte uses ethylene glycol dimethyl ether as the solvent and NaPF6 with a concentration of 1mol / L as the electrolyte.

[0050] Example 1

[0051] The specific steps for preparing the dual-carbon encapsulated tin selenide selenide flexible anode material for sodium-ion batteries are as follows:

[0052] (1) Preparation of hollow carbon spheres:

[0053] First, in a solvent system of 220g ethanol and 40g deionized water, 1.2g resorcinol, 0.6g formaldehyde as a carbon precursor, 3g ammonia and 23.2g tetraethyl orthosilicate were added. After stirring at room temperature for 24h, the mixture was centrifuged and dried to obtain phenolic resin / silica composite microspheres.

[0054] Then, the phenolic resin / silica composite microspheres were placed in a tube furnace and heated to 700°C at 5°C / min under a nitrogen atmosphere and held for 2 hours; then cooled under nitrogen protection to obtain carbon / silica microspheres.

[0055] Finally, the obtained carbon / silica microspheres were immersed in a 2 mol / L NaOH solution and etched at 60 °C for 24 h to remove the silica, thus obtaining hollow carbon spheres.

[0056] (2) Preparation of SnSSe@HC:

[0057] First, dissolve 600 mg sodium stannate, 170 mg thiourea, 220 mg selenium oxide, and 600 mg sodium borohydride in 60 mL of deionized water.

[0058] Then, 100 mg of the hollow carbon spheres obtained in step (1) were dispersed in the above solution; the solution was transferred to a reaction vessel and hydrothermally treated at 180 °C for 10 h. After cleaning and drying, SnSSe@HC was prepared.

[0059] (3) Preparation of SnSSe@HC-NCF composite fiber membrane:

[0060] First, dissolve 0.5g of polyacrylonitrile and 0.5g of polyvinylpyrrolidone in 10mL of DMF; disperse 0.5g of SnSSe@HC obtained in step (2) in the above DMF solution, and sonicate and stir evenly to obtain electrospinning precursor solution.

[0061] Then, the obtained electrospinning precursor solution was electrospinned under the conditions of 20kV voltage, 15cm spinning distance, and 1mL / h flow rate of electrospinning precursor solution to obtain a flexible SnSSe@HC-electrospun nanofiber membrane.

[0062] Finally, the obtained flexible SnSSe@HC-electrospun nanofiber membrane was placed in a tube furnace and carbonized at 600℃ for 2 hours under nitrogen protection to obtain the SnSSe@HC-NCF composite fiber membrane.

[0063] When used as a negative electrode material in sodium-ion batteries, at 2A·g -1 It has 430 mAh·g after 500 cycles at current density -1 The discharge specific capacity is at 10 A·g -1 It still has 324 mAh·g at current density -1 The specific discharge capacity.

[0064] pass Figure 1 It can be seen that the hydrothermal process does not destroy the microstructure of the hollow carbon spheres. At the same time, due to the abundant functional groups on the inner wall of the hollow carbon spheres, SnSSe is uniformly generated on the inner wall of the carbon spheres.

[0065] pass Figure 2 It can be seen that the prepared SnSSe@HC is completely encapsulated inside the flexible nitrogen-doped carbon nanofibers.

[0066] pass Figure 3 It can be seen that the characteristic peaks of XRD in the spectrum correspond to the standard characteristic peaks of SnSSe, but no obvious characteristic peaks of carbon materials were observed in the spectrum. This is because carbon has an amorphous structure, and its characteristic peaks are weaker than those of SnSSe.

[0067] pass Figure 4 As can be seen from the figure, the presence of Sn, S, and Se elements further proves the successful preparation of SnSSe, and the appearance of the characteristic peak of N1s confirms that the carbon nanofibers are nitrogen-doped.

[0068] Example 2

[0069] The difference from Example 1 is that the amount of ammonia added in step (1) is 6g, while the rest is the same as in Example 1.

[0070] The diameter of the prepared SnSSe@HC is 200 nm.

[0071] When used as a negative electrode material in sodium-ion batteries, at 2A·g -1 It has 445 mAh·g after 500 cycles at current density -1 The discharge specific capacity is at 10 A·g -1 It still has 360 mAh·g at current density -1 The specific discharge capacity.

[0072] Example 3

[0073] The difference from Example 1 is that the amount of ammonia added in step (1) is 12g, while the rest is the same as in Example 1.

[0074] The prepared SnSSe@HC has a diameter of 100 nm.

[0075] When used as a negative electrode material in sodium-ion batteries, at 2A·g -1 It has 433 mAh·g after 500 cycles at current density -1 The discharge specific capacity is at 10 A·g -1 It still has 342 mAh·g at current density -1 The specific discharge capacity.

[0076] Example 4

[0077] The difference from Example 1 is that in step (3), the amount of polyacrylonitrile and polyvinylpyrrolidone added is 1g each, while the rest is the same as in Example 1.

[0078] When used as a negative electrode material in sodium-ion batteries, at 2A·g -1 It has 436 mAh·g after 500 cycles at current density -1 The discharge specific capacity is at 10 A·g -1 It still has 352 mAh·g at current density -1 The specific discharge capacity.

[0079] Example 5

[0080] The difference from Example 1 is that in step (3), the amount of polyacrylonitrile and polyvinylpyrrolidone added is 1.5g each, and the rest is the same as in Example 1.

[0081] When used as a negative electrode material in sodium-ion batteries, at 2A·g -1 It has 428 mAh·g after 500 cycles at current density -1 The discharge specific capacity is at 10 A·g -1It still has 326 mAh·g at current density -1 The specific discharge capacity.

[0082] Example 6

[0083] The difference from Example 1 is that the carbonization temperature in step (3) is 700°C, while the rest is the same as in Example 1.

[0084] pass Figure 5 As can be seen, the SnSSe@HC-NCF composite fiber membrane prepared in this example exhibits excellent rate performance as a sodium-ion battery anode material, achieving a rate of 10 A·g. −1 It has 330 mAh·g at current density −1 The specific discharge capacity.

[0085] Figure 6 The SnSSe@HC-NCF composite fiber membrane prepared in this example was used as a negative electrode material for sodium-ion batteries at 2 A·g −1 Cyclic stability at current density. It can be seen that the electrode did not show significant capacity decay after 500 cycles, and still retained 468 mAh·g after 500 cycles. −1 The discharge specific capacity demonstrates that the dual-carbon structure designed in this invention can effectively improve the cycle stability of SnSSe.

[0086] Example 7

[0087] The difference from Example 1 is that the carbonization temperature in step (3) is 800°C, while the rest is the same as in Example 1.

[0088] When used as a negative electrode material in sodium-ion batteries, at 2A·g -1 It has 412 mAh·g after 500 cycles at current density -1 The discharge specific capacity is at 10 A·g -1 It still has 335 mAh·g at current density -1 The specific discharge capacity.

Claims

1. A flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide, characterized in that, In this material, tin selenide sulfide is encapsulated in a double carbon layer composed of hollow carbon spheres and flexible nitrogen-doped carbon nanofibers; SnSSe is uniformly distributed on the inner wall of the hollow carbon spheres to form SnSSe@HC; SnSSe@HC is completely wrapped inside the flexible nitrogen-doped carbon nanofibers to form a flexible SnSSe@HC-NCF composite fiber membrane with a double carbon layer structure.

2. The flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide according to claim 1, characterized in that, The hollow carbon spheres in the SnSSe@HC-NCF composite fiber membrane have a diameter of 100-600 nm.

3. The flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide according to claim 1, characterized in that, The flexible nitrogen-doped carbon nanofibers in the SnSSe@HC-NCF composite fiber membrane have a diameter of 200-2000 nm.

4. The flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide according to claim 1, characterized in that, The SnSSe content in the SnSSe@HC-NCF composite fiber membrane is 20wt%-90wt%.

5. A method for preparing a flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide as described in claims 1-4, characterized in that, Includes the following steps: First, hollow carbon spheres were prepared using a template method; Then, SnSSe was induced to form on the inner wall of HC by hydrothermal treatment of Sn source, S source, Se source and reducing agent to obtain SnSSe@HC; Finally, the obtained SnSSe@HC was dispersed in an N,N-dimethylformamide solution containing polyacrylonitrile and polyvinylpyrrolidone to obtain an electrospinning precursor solution; the electrospinning precursor solution was electrospinned to obtain a flexible SnSSe@HC-electrospinned nanofiber membrane. The obtained flexible SnSSe@HC-electrospun nanofiber membrane was carbonized to obtain SnSSe@HC-NCF composite fiber membrane.

6. The method for preparing the flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide according to claim 5, characterized in that, The specific steps are as follows: (1) Preparation of hollow carbon spheres: First, resorcinol, formaldehyde, ammonia and tetraethyl orthosilicate were added in a solvent system of ethanol and water and stirred at room temperature to obtain phenolic resin / silica composite microspheres. Then, the obtained phenolic resin / silica composite microspheres were calcined under a nitrogen atmosphere to obtain carbon / silica microspheres. Finally, the carbon / silica microspheres were etched with sodium hydroxide solution under heating conditions to remove the silica and obtain hollow carbon spheres. (2) Preparation of SnSSe@HC: The hollow carbon spheres obtained in step (1) are dispersed in an aqueous solution composed of Sn source, S source, Se source and reducing agent, and hydrothermally treated at 160-200℃ for 8-12h to prepare SnSSe@HC; (3) Preparation of SnSSe@HC-NCF composite fiber membrane: First, the SnSSe@HC obtained in step (2) is dispersed in an N,N-dimethylformamide (DMF) solution containing a mixed polymer of polyacrylonitrile and polyvinylpyrrolidone, and ultrasonically and uniformly stirred to obtain an electrospinning precursor solution. Then, the obtained electrospinning solution was electrospinned to obtain a flexible SnSSe@HC-electrospun nanofiber membrane. Finally, the obtained flexible SnSSe@HC-electrospun nanofiber membrane was carbonized under a nitrogen protective atmosphere to obtain SnSSe@HC-NCF composite fiber membrane.

7. The method for preparing the flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide according to claim 5 or 6, characterized in that, The Sn source is at least one of sodium stannate, stannous chloride, or stannous chloride; the S source is at least one of thiourea, sodium sulfide, or thioacetamide; the Se source is at least one of selenium oxide, sodium selenate, or selenium powder; and the reducing agent is sodium borohydride or hydrazine hydrate.

8. The method for preparing the flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide according to claim 6, characterized in that, In step (1), the mass ratio of formaldehyde: resorcinol: ammonia: water: tetraethyl orthosilicate: ethanol is 1:2:(5-20):(40-70):(20-40):(300-400); The stirring time is 12-24 h; the calcination temperature is 600-900 ℃, the calcination time is 2-4 h, and the heating rate of the calcination is 5 ℃ / min; the concentration of the sodium hydroxide solution is 1-4 mol / L, and the etching temperature is 60-100 ℃.

9. The method for preparing the flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide according to claim 6, characterized in that, In step (2), the mass ratio of hollow carbon spheres: Sn source: S source: Se source: reducing agent: water is 1:(5-10):(1-2):(2-4):(5-10):(500-600).

10. The method for preparing the flexible anode material for sodium-ion batteries with dual-carbon encapsulated tin selenide sulfide according to claim 6, characterized in that, The mass ratio of polyacrylonitrile to polyvinylpyrrolidone in the mixed polymer of step (3) is 1:1; wherein the weight-average molecular weight of the polyacrylonitrile used is 150,000 and the weight-average molecular weight of polyvinylpyrrolidone is 1,300,000. The mass ratio of the SnSSe@HC mixed polymer is (0.1-1):1, and the concentration of the mixed polymer in N,N-dimethylformamide solution is 10%-30% (w / v). The electrospinning voltage is 15-30kV, the spinning distance is 10-20cm, and the electrospinning precursor solution flow rate is 0.1-10mL / h. The carbonization treatment temperature is 600-900°C. o C, the carbonization treatment time is 2-4 hours, and the heating rate of the carbonization treatment is 1℃ / min.

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