Bi2S3 / CoS2 heterojunction doped self-supporting carbon film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of new-generation energy materials, in particular to a Bi2S3 / CoS2 heterojunction doped self-supporting carbon film as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing polyacrylonitrile, soluble cobalt salt and N, N-dimethylformamide, stirring to obtain a spinning solution, and carrying out electrostatic spinning on the spinning solution to obtain a Co / PAN membrane; after the Co / PAN film is mixed with a 2-methylimidazole solution and a soluble cobalt salt solution, a ZIF-67 / PAN film is obtained; and immersing the ZIF-67 / PAN membrane into a bismuth nitrate solution, pre-carbonizing, vulcanizing, and self-supporting the carbon membrane. Due to the doping of the Bi2S3 / CoS2 heterojunction, the electron mobility of the negative electrode material is effectively improved, the conductivity and the reaction kinetics are enhanced, and the prepared self-supporting carbon film is high in specific capacity, has good rate capability and cycling stability and is particularly suitable for manufacturing a negative electrode of a sodium-ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of a new generation of energy materials, in particular to a Bi 2 S 3 / CoS 2 Heterojunction doped self-supporting carbon film and preparation method and application thereof. Background Art

[0002] With the vigorous development of the new energy field, the problems of high cost and poor safety of lithium batteries have become increasingly prominent. Sodium-ion batteries (SIBs) have attracted widespread attention due to their abundant reserves and similar "rocking chair" working mechanism to lithium-ion batteries. However, SIBs negative electrode materials have low capacity, poor long-cycle performance and low initial Coulombic efficiency (ICE), and there is an urgent need to develop new high-performance SIBs negative electrode materials. Based on the ion storage mechanism, SIBs negative electrode materials are divided into three categories, namely intercalation type, conversion type and alloy type. Among them, conversion reaction type cobalt-based sulfides have attracted widespread attention from researchers due to their excellent theoretical capacity, rich valence states and excellent sodium ion storage capacity. However, this type of material also faces many challenges, such as: relatively low conductivity, slow kinetics, large volume changes, and the shuttling effect of polysulfides.

[0003] Compared with single-component metal sulfides, heterogeneous multi-component metal sulfides can greatly promote the interface reaction kinetics and accelerate the electron / ion transport through the internal electric field on the heterogeneous interface due to the different coupling components. The synergistic effect of different components will effectively avoid the aggregation of generated products and reduce the pressure of sodium ions during the insertion / extraction process. Therefore, it is necessary to construct and improve the electrochemical performance of sodium storage in materials. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a Bi 2 S 3 / CoS 2 Heterojunction-doped self-supporting carbon film and its preparation method and application, using electrospun fiber as a matrix, ZIF-67-derived Bi 2 S 3 / CoS 2 The heterojunction is uniformly loaded in the electrospun three-dimensional carbon nanofiber network to construct a self-supporting negative electrode material for sodium ion batteries. 3 + , introducing a large number of lattice mismatches, distortions and defects in the material.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film comprises the following steps:

[0007] 1) mixing and stirring polyacrylonitrile, a soluble cobalt salt and N,N-dimethylformamide to obtain a spinning solution, and electrospinning the spinning solution to obtain a Co / PAN membrane;

[0008] 2) mixing the Co / PAN membrane obtained in step 1) with a 2-methylimidazole solution and a soluble cobalt salt solution, stirring, standing and drying in sequence to obtain a ZIF-67 / PAN membrane;

[0009] 3) immersing the ZIF-67 / PAN membrane obtained in step 2) in a bismuth nitrate solution, allowing it to stand and then drying to obtain a Bi / Co-MOF / PAN membrane;

[0010] 4) pre-carbonizing the Bi / Co-MOF / PAN membrane obtained in step 3) to obtain a pre-carbonized membrane;

[0011] 5) Mixing the pre-carbonized film obtained in step 4) with sulfur powder and then vulcanizing to obtain Bi 2 S 3 / CoS 2 Heterojunction doped free-standing carbon films.

[0012] Preferably, in step 1), the volume ratio of the mass of polyacrylonitrile, the mass of the soluble cobalt salt and N,N-dimethylformamide is 0.714-1.053 g: 0.142-0.282 g: 10 mL;

[0013] The stirring time is 6 hours.

[0014] Preferably, the soluble cobalt salt in step 1) or step 2) includes one or more of cobalt acetate, cobalt sulfate, cobalt nitrate and cobalt chloride.

[0015] Preferably, the conditions for electrospinning in step 1) include: an operating voltage of 15 to 20 kV, a distance between the needle and the collector of 12 to 20 cm, a spinning environment temperature of 15 to 25 ° C, a humidity of 25 to 50%, and a solution propulsion speed of 0.00015 to 0.00030 mL s -1 , the drum speed is set to 150~300rmin -1 .

[0016] Preferably, in step 2), the ratio of the mass of the Co / PAN film to the volume of the 2-methylimidazole solution and the volume of the soluble cobalt salt solution is 5.9-11.8 mg:20 mL:10 mL;

[0017] Each 20 mL of 2-methylimidazole solution contains 0.3144 to 0.6321 g of 2-methylimidazole;

[0018] Each 10 mL of soluble cobalt salt solution contains 416 to 879 mg of soluble cobalt salt;

[0019] The standing time is 1 to 4 hours;

[0020] The drying conditions include: temperature of 60° C. and time of 12 h.

[0021] Preferably, in step 3), the volume ratio of the mass of the ZIF-67 / PAN membrane to the bismuth nitrate solution is 10-45 mg:10 mL;

[0022] Each 10 mL of bismuth nitrate solution contains 15 to 50 mg of bismuth nitrate;

[0023] The standing time is 2h;

[0024] The drying conditions include: temperature of 60° C. and time of 12 h.

[0025] Preferably, the pre-carbonization conditions in step 4) include: a temperature of 200-350° C. and a time of 2 hours.

[0026] Preferably, the mass ratio of the pre-carbonized film to the sulfur powder in step 5) is 1:5-10;

[0027] The vulcanization conditions include: temperature of 400-600° C., time of 2 hours, and in a nitrogen atmosphere.

[0028] The present invention also provides a Bi prepared by the preparation method described in the above technical solution 2 S 3 / CoS 2 Heterojunction doped free-standing carbon films.

[0029] The present invention also provides the Bi described in the above technical solution 2 S 3 / CoS 2 Application of heterojunction-doped self-supporting carbon films in the preparation of negative electrode materials for sodium-ion batteries.

[0030] Beneficial effects of the present invention:

[0031] The present invention uses ion exchange method to introduce Bi into the material 3+, forming a heterogeneous interface with lattice mismatch, distortion and defects in the crystal, enhancing the conductivity and reaction kinetics of the material; the three-dimensional mesh carbon fiber structure effectively alleviates the volume expansion of the material during the charging and discharging process, improves the conductivity of the material while providing a directional charge transfer direction, and effectively improves the cycle stability of the battery; the prepared self-supporting electrode material does not require the use of conductive inert components such as adhesives, thereby improving the overall specific capacity of the material, and does not require the use of current collector materials such as copper foil, further reducing the cost of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0033] Figure 1 Field emission scanning electron microscope (SEM) image of the ZIF-67 / PAN film prepared in Example 1;

[0034] Figure 2 Bi prepared in Example 1 2 S 3 / CoS 2 Field emission scanning electron microscopy (SEM) image of the heterojunction-doped free-standing carbon film;

[0035] Figure 3 Bi prepared in Example 1 2 S 3 / CoS 2 Heterojunction-doped free-standing carbon films as anode materials for sodium-ion batteries in 2Ag -1 Cycling performance diagram of 1000 cycles at the current density;

[0036] Figure 4 CoS prepared in Example 5 2 Doped free-standing carbon films as anode materials for sodium-ion batteries in 2Ag -1 Cycling performance diagram of 1000 cycles at the same current density. DETAILED DESCRIPTION

[0037] The present invention provides a Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film comprises the following steps:

[0038] 1) mixing and stirring polyacrylonitrile, a soluble cobalt salt and N,N-dimethylformamide to obtain a spinning solution, and electrospinning the spinning solution to obtain a Co / PAN membrane;

[0039] 2) mixing the Co / PAN membrane obtained in step 1) with a 2-methylimidazole solution and a soluble cobalt salt solution, stirring, standing and drying in sequence to obtain a ZIF-67 / PAN membrane;

[0040] 3) immersing the ZIF-67 / PAN membrane obtained in step 2) in a bismuth nitrate solution, allowing it to stand and then drying to obtain a Bi / Co-MOF / PAN membrane;

[0041] 4) pre-carbonizing the Bi / Co-MOF / PAN membrane obtained in step 3) to obtain a pre-carbonized membrane;

[0042] 5) Mixing the pre-carbonized film obtained in step 4) with sulfur powder and then vulcanizing to obtain Bi 2 S 3 / CoS 2 Heterojunction doped free-standing carbon films.

[0043] The invention mixes and stirs polyacrylonitrile, soluble cobalt salt and N,N-dimethylformamide to obtain a spinning solution, and electrostatically spins the spinning solution to obtain a Co / PAN membrane.

[0044] In the present invention, the mass of the polyacrylonitrile, the mass of the soluble cobalt salt and the volume ratio of N,N-dimethylformamide are preferably 0.714-1.053 g: 0.142-0.282 g: 10 mL. In the present invention, the stirring time is preferably 6 hours. In the present invention, the soluble cobalt salt preferably includes one or more of cobalt acetate, cobalt sulfate, cobalt nitrate and cobalt chloride. In the present invention, the conditions for the electrospinning preferably include: the operating voltage is 15-20 kV, the distance between the needle and the collector is 12-20 cm, the spinning environment temperature is maintained at 15-25 ° C, the humidity is 25-50%, and the solution propulsion speed is 0.00015-0.00030 mL s -1 , the drum speed is set to 150~300rmin -1 .

[0045] The invention mixes the obtained Co / PAN membrane with a 2-methylimidazole solution and a soluble cobalt salt solution, and then stirs, stands and dries in sequence to obtain a ZIF-67 / PAN membrane.

[0046] In the present invention, the mass of the Co / PAN film to the volume of the 2-methylimidazole solution and the volume ratio of the soluble cobalt salt solution is preferably 5.9-11.8 mg:20 mL:10 mL. In the present invention, each 20 mL of 2-methylimidazole solution preferably contains 0.3144-0.6321 g of 2-methylimidazole. In the present invention, each 10 mL of soluble cobalt salt solution preferably contains 416-879 mg of soluble cobalt salt. In the present invention, the standing time is preferably 1-4 h. In the present invention, the drying conditions preferably include: a temperature of 60°C and a time of 12 h.

[0047] The present invention immerses the obtained ZIF-67 / PAN membrane in a bismuth nitrate solution, leaves it to stand and then dries it to obtain a Bi / Co-MOF / PAN membrane. In the present invention, the volume ratio of the mass of the ZIF-67 / PAN membrane to the bismuth nitrate solution is preferably 10 to 45 mg:10 mL. In the present invention, each 10 mL of bismuth nitrate solution preferably contains 15 to 50 mg of bismuth nitrate. In the present invention, the standing time is preferably 2 hours. In the present invention, the drying conditions preferably include: a temperature of 60°C and a time of 12 hours.

[0048] The present invention pre-carbonizes the obtained Bi / Co-MOF / PAN membrane to obtain a pre-carbonized membrane. In the present invention, the pre-carbonization conditions preferably include: a temperature of 200 to 350° C. and a time of 2 hours.

[0049] The present invention mixes the obtained pre-carbonized film with sulfur powder and then performs sulfurization to obtain Bi 2 S 3 / CoS 2 Heterojunction doped self-supporting carbon film. In the present invention, the mass ratio of the pre-carbonized film to the sulfur powder is preferably 1:5 to 10. In the present invention, the sulfurization conditions preferably include: a temperature of 400 to 600° C., a time of 2 hours, and a nitrogen atmosphere.

[0050] The present invention also provides a Bi prepared by the preparation method described in the above technical solution 2 S 3 / CoS 2 Heterojunction doped free-standing carbon films.

[0051] The present invention also provides the Bi described in the above technical solution 2 S 3 / CoS 2 Application of heterojunction-doped self-supporting carbon films in the preparation of negative electrode materials for sodium-ion batteries.

[0052] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] A kind of Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film, comprising the steps of:

[0055] 0.938 g of polyacrylonitrile and 0.237 g of cobalt acetate tetrahydrate were dissolved in 10 mL of DMF and stirred at room temperature for 6 hours to prepare a spinning solution. The electrospinning working voltage was set to 18 kV, the distance between the needle and the collector was 15 cm, the spinning environment temperature was maintained at 25 °C, the humidity was 30%, and the solution propulsion speed was 0.00025 mL s -1 , the drum speed is set to 200rmin -1 Under the conditions of , Co / PAN membrane was prepared by electrospinning;

[0056] 11.8 mg of Co / PAN membrane was immersed in 20 mL of methanol solution containing 0.5933 g of 2-methylimidazole, and 10 mL of methanol solution containing 687 mg of cobalt acetate tetrahydrate was added, mixed, stirred, and allowed to stand for 4 h, washed with anhydrous ethanol, and dried at 60 ° C for 12 h to obtain the reaction product ZIF-67 / PAN membrane;

[0057] 10 mg of ZIF-67 / PAN membrane was immersed in 10 mL of 20 mg of Bi(NO 3 ) 3 .5H 2 O ethylene glycol solution, after standing for 2 h, taken out, washed three times with anhydrous ethanol and deionized water respectively, and dried at 60 ° C for 12 h to obtain Bi / Co-MOF / PAN membrane;

[0058] The Bi / Co-MOF / PAN membrane was treated at 200 °C for 2 h in air atmosphere to obtain a pre-carbonized membrane;

[0059] 10 mg of the pre-carbonized film and 80 mg of sulfur powder were placed in a nitrogen atmosphere and treated at 400°C for 2 h to obtain a Bi2S3 / CoS2 heterojunction-doped self-supporting carbon film.

[0060] The self-supporting carbon film was taken out, sliced ​​and weighed, placed in a glove box for balancing for 8 hours, and then assembled into a sodium ion battery to test the electrochemical performance of the battery.

[0061] Example 2

[0062] A kind of Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film, comprising the steps of:

[0063] 1.053 g of polyacrylonitrile and 0.142 g of cobalt sulfate were dissolved in 10 mL of DMF and stirred at room temperature for 6 hours to prepare a spinning solution. The electrospinning working voltage was set to 15 kV, the distance between the needle and the collector was 12 cm, the spinning environment temperature was maintained at 25 °C, the humidity was 25%, and the solution propulsion speed was 0.00015 mL s -1 , the drum speed is set to 150rmin -1 Under the conditions of , Co / PAN membrane was prepared by electrospinning;

[0064] 6.4 mg of Co / PAN membrane was immersed in 20 mL of methanol solution containing 0.3144 g of 2-methylimidazole, and 10 mL of methanol solution containing 505 mg of cobalt sulfate was added, mixed, stirred, and allowed to stand for 1 h, washed with anhydrous ethanol, and dried at 60 ° C for 12 h to obtain the reaction product ZIF-67 / PAN membrane;

[0065] 45 mg of ZIF-67 / PAN membrane was immersed in 10 mL of 15 mg of Bi(NO 3 ) 3 .5H 2 O ethylene glycol solution, after standing for 2 h, taken out, washed three times with anhydrous ethanol and deionized water respectively, and dried at 60 ° C for 12 h to obtain Bi / Co-MOF / PAN membrane;

[0066] The Bi / Co-MOF / PAN membrane was treated at 300 °C for 2 h in air atmosphere to obtain a pre-carbonized membrane;

[0067] 10 mg of the pre-carbonized film and 50 mg of sulfur powder were placed in a nitrogen atmosphere and treated at 500°C for 2 h to obtain a Bi2S3 / CoS2 heterojunction-doped self-supporting carbon film.

[0068] The self-supporting carbon film was taken out, sliced ​​and weighed, placed in a glove box for balancing for 8 hours, and then assembled into a sodium ion battery to test the electrochemical performance of the battery.

[0069] Example 3

[0070] A kind of Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film, comprising the steps of:

[0071] 0.824 g polyacrylonitrile and 0.189 g cobalt nitrate were dissolved in 10 mL DMF and stirred at room temperature for 6 hours to prepare a spinning solution. The electrospinning working voltage was set to 18 kV, the distance between the needle and the collector was 18 cm, the spinning environment temperature was maintained at 25 °C, the humidity was 50%, and the solution propulsion speed was 0.00030 mL s -1, the drum speed is set to 300rmin -1 Under the conditions of , Co / PAN membrane was prepared by electrospinning;

[0072] 6.3 mg of Co / PAN membrane was immersed in 20 mL of methanol solution containing 0.6321 g of 2-methylimidazole, and 10 ml of methanol solution containing 416 mg of cobalt nitrate was added, mixed, stirred, and allowed to stand for 2 h, washed with anhydrous ethanol, and dried at 60 ° C for 12 h to obtain the reaction product ZIF-67 / PAN membrane;

[0073] 25 mg of ZIF-67 / PAN membrane was immersed in 10 mL of 50 mg of Bi(NO 3 ) 3 .5H 2 O ethylene glycol solution, after standing for 2 h, taken out, washed three times with anhydrous ethanol and deionized water respectively, and dried at 60 ° C for 12 h to obtain Bi / Co-MOF / PAN membrane;

[0074] The Bi / Co-MOF / PAN membrane was treated at 350 °C for 2 h in air atmosphere to obtain a pre-carbonized membrane;

[0075] 10 mg of pre-carbonized film and 100 mg of sulfur powder were placed in a nitrogen atmosphere and treated at 600 °C for 2 h to obtain Bi 2 S 3 / CoS 2 Heterojunction doped free-standing carbon films.

[0076] The self-supporting carbon film was taken out, sliced ​​and weighed, placed in a glove box for balancing for 8 hours, and then assembled into a sodium ion battery to test the electrochemical performance of the battery.

[0077] Example 4

[0078] A kind of Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film, comprising the steps of:

[0079] 0.714 g polyacrylonitrile and 0.282 g cobalt chloride were dissolved in 10 mL DMF and stirred at room temperature for 6 hours to prepare a spinning solution. The electrospinning working voltage was set to 20 kV, the distance between the needle and the collector was 15 cm, the spinning environment temperature was maintained at 25 °C, the humidity was 40%, and the solution propulsion speed was 0.00025 mL s -1 , the drum speed is set to 250rmin -1 Under the conditions of , Co / PAN membrane was prepared by electrospinning;

[0080] 5.9 mg of Co / PAN membrane was immersed in 20 mL of methanol solution containing 0.5933 g of 2-methylimidazole, and 10 ml of methanol solution containing 879 mg of cobalt chloride was added, mixed, stirred, and allowed to stand for 3 h, washed with anhydrous ethanol, and dried at 60 ° C for 12 h to obtain the reaction product ZIF-67 / PAN membrane;

[0081] 30 mg of ZIF-67 / PAN membrane was immersed in 10 mL of 30 mg of Bi(NO 3 ) 3 .5H 2 O ethylene glycol solution, after standing for 2 h, taken out, washed three times with anhydrous ethanol and deionized water respectively, and dried at 60 ° C for 12 h to obtain Bi / Co-MOF / PAN membrane;

[0082] The Bi / Co-MOF / PAN membrane was treated at 250 °C for 2 h in air atmosphere to obtain a pre-carbonized membrane;

[0083] 10 mg of pre-carbonized film and 60 mg of sulfur powder were placed in a nitrogen atmosphere and treated at 500 ° C for 2 h to obtain Bi 2 S 3 / CoS 2 Heterojunction doped free-standing carbon films.

[0084] The self-supporting carbon film was taken out, sliced ​​and weighed, placed in a glove box for balancing for 8 hours, and then assembled into a sodium ion battery to test the electrochemical performance of the battery.

[0085] Comparative Example 1

[0086] A kind of Bi 2 S 3 / CoS 2 A method for preparing a heterojunction-doped self-supporting carbon film, comprising the steps of:

[0087] The experiment of Example 1 was repeated, but without the Bi ion replacement reaction, to prepare CoS 2 Doped self-supporting carbon film is used as a control sample. Specifically:

[0088] 0.938 g of polyacrylonitrile and 0.237 g of cobalt acetate tetrahydrate were dissolved in 10 mL of DMF and stirred at room temperature for 6 hours to prepare a spinning solution. The electrospinning working voltage was set to 18 kV, the distance between the needle and the collector was 15 cm, the spinning environment temperature was maintained at 25 °C, the humidity was 30%, and the solution propulsion speed was 0.00025 mL s -1 , the drum speed is set to 200rmin -1 Under the conditions of , Co / PAN membrane was prepared by electrospinning;

[0089] 11.8 mg of Co / PAN membrane was immersed in 20 mL of methanol solution containing 0.5933 g of 2-methylimidazole, and 10 mL of methanol solution containing 687 mg of cobalt acetate tetrahydrate was added, mixed, stirred, and allowed to stand for 4 h, washed with anhydrous ethanol, and dried at 60 ° C for 12 h to obtain the reaction product ZIF-67 / PAN membrane;

[0090] The ZIF-67 / PAN membrane was treated at 200 °C for 2 h in air atmosphere to obtain a pre-carbonized membrane;

[0091] 10 mg of pre-carbonized film and 80 mg of sulfur powder were placed in a nitrogen atmosphere and treated at 400 °C for 2 h to obtain CoS 2 Doped free-standing carbon films.

[0092] The self-supporting carbon film was taken out, sliced ​​and weighed, placed in a glove box for balancing for 8 hours, and then assembled into a sodium ion battery to test the electrochemical performance of the battery.

[0093] The five self-supporting carbon films prepared in Example 1 (denoted as a), 2 (denoted as b), 3 (denoted as c), 4 (denoted as d) and Comparative Example 1 (denoted as e) were measured at 0.5 Ag. -1 Electrochemical performance at different current densities.

[0094] Table 1 shows the characterization results of the self-supporting carbon films prepared by Examples 1, 2, 3, 4 and Comparative Example 1. It can be seen from the data in Table 1 that the Bi 2 S 3 / CoS 2 Heterojunction doped self-supporting carbon battery negative electrode materials (a), (b), (c), (d) at 0.5Ag -1 The current density was 498.56 mAh g after 100 cycles. -1 , 454.33mAh g -1 , 403.98mAh g -1 , 368.24mAh g -1 Excellent sodium storage performance, while only CoS 2 Doped self-supporting carbon battery negative electrode material (e) at 0.5Ag -1 The specific capacity after 100 cycles at the current density is 292.13 mAh g -1 .

[0095] Depend on Figure 3 It can be seen that the Bi obtained by the preparation method of the present invention 2 S 3 / CoS 2 Heterojunction doped self-supporting carbon film battery anode material (a) at 2A g -1The high current density can still achieve 247.92 mAh g after 1000 cycles. -1 Excellent sodium storage performance.

[0096] Depend on Figure 4 It can be seen that the CoS obtained by the preparation method of the present invention 2 Doped self-supporting carbon film battery negative electrode material (e) at 2Ag -1 The specific capacity after 1000 cycles at high current density is 151.35 mAh g -1 .

[0097] like Figure 1 From the field emission scanning electron microscope photograph of the ZIF-67 / PAN film prepared in Example 1, it can be seen that the PAN fibers are covered with ZIF-67 particles, which are approximately cubic in structure and have a side length of approximately 100 nanometers. Figure 2 It can be seen that the size of the particles on the fiber surface is slightly reduced after subsequent carbonization and vulcanization.

[0098] like Figure 3 , prepared from Bi in Example 1 2 S 3 / CoS 2 Heterojunction-doped free-standing carbon films as anode materials for sodium-ion batteries in 2Ag -1 Cycling performance diagram of 1000 cycles at the same current density.

[0099] like Figure 4 , CoS prepared from Example 5 2 Doped free-standing carbon films as anode materials for sodium-ion batteries in 2Ag -1 Cycling performance diagram of 1000 cycles at the same current density.

[0100] Table 1 Characterization results of self-supporting carbon film battery negative electrode materials

[0101]

[0102] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Bi2S3 / CoS2 heterojunction doped self-supporting carbon film, characterized in that: The following steps are involved: 1) mixing and stirring polyacrylonitrile, a soluble cobalt salt and N,N-dimethylformamide to obtain a spinning solution, and electrospinning the spinning solution to obtain a Co / PAN membrane; 2) mixing the Co / PAN membrane obtained in step 1) with a 2-methylimidazole solution and a soluble cobalt salt solution, stirring, standing and drying in sequence to obtain a ZIF-67 / PAN membrane; 3) immersing the ZIF-67 / PAN membrane obtained in step 2) in a bismuth nitrate solution, allowing it to stand and then drying to obtain a Bi / Co-MOF / PAN membrane; 4) pre-carbonizing the Bi / Co-MOF / PAN membrane obtained in step 3) to obtain a pre-carbonized membrane; 5) The pre-carbonized film obtained in step 4) is mixed with sulfur powder and then sulfurized to obtain a Bi2S3 / CoS2 heterojunction doped self-supporting carbon film.

2. The preparation method according to claim 1, characterized in that: In the step 1), the volume ratio of the mass of polyacrylonitrile, the mass of the soluble cobalt salt and N,N-dimethylformamide is 0.714-1.053 g: 0.142-0.282 g: 10 mL; The stirring time is 6 hours.

3. The preparation method according to claim 1, characterized in that: The soluble cobalt salt in step 1) or step 2) includes one or more of cobalt acetate, cobalt sulfate, cobalt nitrate and cobalt chloride.

4. The preparation method according to claim 1, characterized in that: The conditions of the electrospinning in step 1) include: a working voltage of 15-20 kV, a distance between the needle and the collector of 12-20 cm, a spinning environment temperature of 15-25° C., a humidity of 25-50%, and a solution propulsion speed of 0.00015-0.00030 mL s -1 , the drum speed is set to 150~300rmin -1 .

5. The preparation method according to claim 1, characterized in that: In the step 2), the volume ratio of the mass of the Co / PAN film to the volume of the 2-methylimidazole solution and the volume of the soluble cobalt salt solution is 5.9-11.8 mg:20 mL:10 mL; Each 20 mL of 2-methylimidazole solution contains 0.3144 to 0.6321 g of 2-methylimidazole; Each 10 mL of soluble cobalt salt solution contains 416 to 879 mg of soluble cobalt salt; The standing time is 1 to 4 hours; The drying conditions include: temperature of 60° C. and time of 12 h.

6. The preparation method according to claim 1, characterized in that: In the step 3), the volume ratio of the mass of the ZIF-67 / PAN membrane to the bismuth nitrate solution is 10-45 mg:10 mL; Each 10 mL of bismuth nitrate solution contains 15 to 50 mg of bismuth nitrate; The standing time is 2h; The drying conditions include: temperature of 60° C. and time of 12 h.

7. The preparation method according to claim 1, characterized in that: The pre-carbonization conditions in step 4) include: a temperature of 200-350° C. and a time of 2 hours.

8. The preparation method according to claim 1, characterized in that: In step 5), the mass ratio of the pre-carbonized film to the sulfur powder is 1:5-10; The vulcanization conditions include: temperature of 400-600° C., time of 2 hours, and in a nitrogen atmosphere.

9. A Bi2S3 / CoS2 heterojunction doped self-supporting carbon film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Bi2S3 / CoS2 heterojunction doped self-supporting carbon film according to claim 9 in preparing negative electrode materials for sodium ion batteries.

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