A preparation method of a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure

Abstract

The application is a three-dimensional carbon fiber continuous film with composite Bi@NC core-shell structure prepared by electrostatic spinning method, and the steps are as follows: firstly, a precursor solution for electrostatic spinning is prepared, then Bi@NC flexible fiber film is obtained through high-temperature calcination, and the specific morphology of the Bi@NC core-shell structure fiber is controlled by changing the annealing temperature and time. The method has the advantages of simple process, low cost and strong practicability. As long as the annealing temperature, time and Bi precursor amount are changed, fiber film with different core-shell structure morphology can be obtained, and the application in sodium metal negative electrode host shows excellent performance, and has good application prospect.

Description

Technical Field

[0001] This invention relates to the field of new energy electrochemistry, specifically to a method for preparing a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure. Background Technology

[0002] Driven by the urgent need for sustainable energy storage technologies, sodium metal possesses an extremely high theoretical specific capacity (1166 mA hg). -1 Sodium metal anodes have become a research hotspot in the energy field due to their relatively low electrochemical potential (-2.714 V vs. standard hydrogen electrode) and abundant and inexpensive sodium-based resources. However, due to the high electrochemical activity and unlimited volume variation of sodium metal, uncontrollable excessive side reactions between sodium and electrolyte and the uncontrolled growth of sodium dendrites lead to rapid capacity decay and low coulombic efficiency. Furthermore, sodium dendrites can puncture the separator, causing short circuits and even posing significant safety hazards, severely hindering the practical application of sodium metal anodes. Optimizing electrolytes and electrolyte additives, designing three-dimensional sodium metal hosts, constructing low nucleation barrier engineering and interface engineering, and improving current collectors and separators are common improvement strategies used by researchers. Among these, core-shell structures based on amorphous carbon shells, designed by combining low nucleation barrier engineering and nanostructured interfaces, have gained favor among researchers. By incorporating various heterogeneous seeds, such as N-doped carbon, Au nanoparticles, SnS2 nanosheets, CoSe2, Sb nanoparticles, Sn atoms, and Zn atoms, into hollow amorphous carbon shells, the coulombic efficiency and cycle stability of sodium metal batteries can be improved. Despite these advances, the long-term cycleability of sodium metal anodes at high capacity and high density remains a significant challenge. The development of three-dimensional core-shell sodium hosts, combining structural integrity and efficient charge transport, has shown potential to address this issue. However, the fabrication complexity of these hosts still hinders their widespread adoption. Fortunately, electrospinning has emerged as an economically attractive and controllable manufacturing method. Bismuth (Bi) possesses high affinity and enhances sodium ion diffusion kinetics, contributing to efficient and dendrite-free cycling in sodium metal anodes. The cost-effectiveness of Bi is also a considerable advantage, promoting the prospect of large-scale deployment. While the application of electrospun Bi-embedded fibers has been primarily limited to sodium-ion batteries, three-dimensional Bi core-carbon shell structures are now emerging as promising hosts for sodium metal anodes. Furthermore, the sodium deposition space provided by the core-shell structure is beneficial for elucidating the potential mechanisms that promote the diffusion of sodium ions within the sodium-bismuth alloy, which will provide valuable insights for ultimately improving the cycle life and performance of sodium metal anodes.

[0003] Electrospinning technology, with its advantages of simple operation, controllable preparation, and economic and environmental friendliness, is widely used in sodium metal batteries. First, the fiber diameter is controlled by adjusting the proportion of the precursor solution to find a size conducive to sodium deposition. Second, fibers can be spun quickly from a prepared precursor solution without the need for large amounts of chemical reagents. Finally, the annealed material exhibits flexibility, resistance to folding and deformation, and can be directly used as a negative electrode material, avoiding the addition of electrochemically inactive materials. During high-temperature carbonization, abundant nanopores of 10–50 nm are obtained by removing polymethyl methacrylate (PMMA), resulting in a Bi@NC core-shell structure. Summary of the Invention

[0004] This invention proposes a Bi@NC core-shell structured three-dimensional sodium metal host anode prepared by electrospinning. Its fabrication process is simple, highly controllable, environmentally friendly and economical, and the porous structure can maintain the structural integrity of the active anode material.

[0005] The technical solution of the present invention is: a method for preparing a Bi@NC core-shell structured nanometal battery anode material, the steps of which are as follows: first, a spinning solution is prepared, then a three-dimensional carbon fiber continuous film is obtained by electrospinning, then dried in a vacuum drying oven, and finally annealed at different temperatures, and the battery is assembled to obtain a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure.

[0006] The preparation steps of the spinning solution are as follows: polyacrylonitrile and polymethyl methacrylate are added to N,N dimethylamide, heated and stirred in a water bath at 60℃-80℃ for 2-5 hours, then BiCl3 is added, and the reaction is continued for 8-10 hours to obtain the spinning solution. The mass ratio of polyacrylonitrile, polymethyl methacrylate and BiCl3 is 3-5:2-3:1.

[0007] The preparation steps of obtaining a three-dimensional carbon fiber continuous film using the electrospinning method are as follows: the spinning solution is poured into a syringe, a needle is connected, a 12kV high voltage is applied, the rotation speed of the collecting device and the injection speed are controlled, and finally the filament is spun onto an aluminum foil. The electrospinning method is as follows: the syringe is 10ml, the inner diameter of the needle is 0.25mm, the rotation speed of the collecting device is 350r / min, the working voltage is 12KV, and the injection speed is 4ml / h.

[0008] The vacuum drying conditions are: 5-7 hours in a vacuum drying oven at 60℃-80℃.

[0009] The annealing conditions for the electrospun material are as follows: annealing is performed using a N2 / H2 mixed gas, with an initial temperature of 20℃ and a heating rate of 2℃ / min. The temperature is then increased to 350℃ at a heating rate of 2℃ / min and held for 3 hours. The temperature is then increased to 720℃ and held for 4 hours. Finally, the temperature is decreased to the initial temperature of 20℃ at a rate of 1℃ / min.

[0010] The annealing conditions for the electrospun material are as follows: annealing is performed using a N2 / H2 mixed gas, with an initial temperature of 25℃ and a heating rate of 2℃ / min. The temperature is then increased to 350℃ at a heating rate of 2℃ / min and held for 3 hours. The temperature is then increased to 650℃ and held for 8 hours. Finally, the temperature is decreased to the initial temperature of 25℃ at a rate of 1℃ / min.

[0011] The annealing conditions for the electrospun material can also be as follows: annealing with a N2 / H2 mixed gas, starting temperature of 30℃, heating rate of 2℃ / min, heating to 350℃ at a heating rate of 2℃ / min, holding at 3h, heating to 700℃ and holding at 700℃ for 5h, and cooling back to the starting temperature of 30℃ at a rate of 1℃ / min.

[0012] Bi exhibits different morphologies at different annealing temperatures. At higher temperatures, Bi tends to volatilize, leaving behind a porous structure.

[0013] The battery assembly steps are as follows: first, place the positive electrode sheet, then place the nano sheet, then place the Bi@NC material, add the electrolyte (35ml), place two layers of PP separator, then add the electrolyte (35ml), the electrolyte is NaPF6, then place the Bi@NC material, then place the sodium sheet, then place the nickel mesh, then the spring sheet, and finally add the negative electrode shell.

[0014] This invention utilizes electrospinning technology to prepare a Bi@NC core-shell structured three-dimensional sodium metal host as a nanometal anode. The method first involves preparing a spinning solution, then using electrospinning to prepare the three-dimensional nanometal host structure, which is then dried in a vacuum drying oven. Annealing is performed using a N2 / H2 mixed gas. At an annealing temperature of 720℃, a porous structure emerges, increasing the specific surface area. These pores can accommodate the expansion of Bi particles. The core-shell structure avoids direct contact between sodium and the electrolyte, reducing electrolyte consumption. A stable SEI film can be formed on the carbon shell, exhibiting strong ionic conductivity and high mechanical strength.

[0015] The beneficial effects of this invention are:

[0016] (1) Electrospinning is a simple, efficient, environmentally friendly and economical technology. The diameter of the fiber can be directly controlled by changing the parameters.

[0017] (2) At an annealing temperature of 720℃, PMMA will volatilize, resulting in a porous structure that increases the specific surface area. These pores can accommodate the expansion of Bi particles. Utilizing this structure, other metals can be incorporated while maintaining the structural integrity of the active anode material;

[0018] (3) The core-shell structure can prevent the electrolyte from directly contacting sodium, reduce electrolyte consumption, and enhance the mechanical strength and ionic conductivity of the material. Attached Figure Description

[0019] Figure 1 Transmission electron microscopy (a, b, c) of Bi@NC fibers prepared at different annealing temperatures for Example 1 and scanning electron microscopy (d, e, f) of Bi@NC spun materials;

[0020] Figure 2 The XRD pattern of the Bi@NC core-shell structured three-dimensional sodium metal host anode material prepared in Example 1;

[0021] Figure 3 Raman spectrum of the Bi@NC core-shell structured three-dimensional sodium metal host anode material prepared in Example 1;

[0022] Figure 4 The Bi@NC core-shell structured three-dimensional sodium metal host anode material in Example 1 at 3 mA cm⁻¹ -2 3 mAh cm -2 Coulomb efficiency diagram below;

[0023] Figure 5 The Bi@NC core-shell structured three-dimensional sodium metal host anode material in Example 1 was tested at 30 mA cm⁻¹. -2 3 mAhcm -2 The following is a long loop graph. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing a Bi@NC core-shell structured nanometal battery anode material, comprising the following steps:

[0027] (1) To prepare the spinning solution, first pour 15 ml of NN dimethylamide (DMF), then slowly add 1.6 g of polyacrylonitrile (PAN) and 0.6 g of polymethyl methacrylate (PMMA) into the DMF, heat and stir in a water bath at 70°C for 2 h to obtain a yellow viscous solution, then slowly add 0.42 g of BiCl3 and stir for 8 h to obtain a uniform white solution;

[0028] (2) Using electrospinning technology to obtain three-dimensional carbon fiber continuous film, the steps are as follows: pour the spinning solution into the syringe, connect the needle, then apply high voltage, control the rotation speed of the collecting device and the injection speed, and finally spin the filament onto the aluminum foil. The spinning conditions are: the syringe is 10ml, the inner diameter of the needle is 0.25mm, the rotation speed of the collecting device is 350r / min, the working voltage is 12KV, and the injection speed is 4ml / h.

[0029] (3) Place the spun sample in a vacuum drying oven at 60℃ for 5 hours, and finally anneal it in the air at different temperatures; Annealing conditions: Anneal with N2 / H2 mixed gas, starting temperature is 20℃, heating rate is 2℃ / min, heating rate is 2℃ / min to 350℃, hold for 3 hours, heating rate is 720℃ and hold for 4 hours, cooling rate is 1℃ / min to the starting temperature of 20℃;

[0030] (4) Assemble the battery. The steps are as follows: First, place the positive electrode plate, then place the nanoplate, then place the Bi@NC material, add the electrolyte (35ml), place two layers of PP separator, then add the electrolyte NaPF6 (35ml), place the Bi@NC material, place the nanoplate, place the nickel mesh, spring sheet, and finally add the negative electrode shell.

[0031] Example 2

[0032] A method for preparing a Bi@NC core-shell structured nanometal battery anode material, comprising the following steps:

[0033] (1) To prepare the spinning solution, first pour in 30 ml of NN dimethylamide (DMF), then slowly add 5 g of polyacrylonitrile (PAN) and 3 g of polymethyl methacrylate (PMMA) into DMF, heat and stir in a water bath at 60°C for 3 h to obtain a yellow viscous solution, then slowly add 1 g of BiCl3 and stir for 8 h to obtain a uniform white solution.

[0034] (2) Using electrospinning technology to obtain three-dimensional carbon fiber continuous film, the steps are as follows: pour the spinning solution into the syringe, connect the needle, then apply high voltage, control the rotation speed of the collecting device and the injection speed, and finally spin the filament onto the aluminum foil. The spinning conditions are: the syringe is 10ml, the inner diameter of the needle is 0.25mm, the rotation speed of the collecting device is 350r / min, the working voltage is 12KV, and the injection speed is 4ml / h.

[0035] (3) Place the spun sample in a vacuum drying oven at 80℃ for 7 hours, and finally anneal it in the air at different temperatures; Annealing conditions: Anneal with N2 / H2 mixed gas, starting temperature is 20℃, heating rate is 2℃ / min, heating rate is 2℃ / min to 350℃, hold for 3 hours, heating rate is 720℃ and hold for 4 hours, cooling rate is 1℃ / min to the starting temperature of 20℃;

[0036] (4) Assemble the battery. The steps are as follows: First, place the positive electrode plate, then place the nanoplate, then place the Bi@NC material, add the electrolyte (35ml), place two layers of PP separator, then add the electrolyte NaPF6 (35ml), place the Bi@NC material, place the nanoplate, place the nickel mesh, spring sheet, and finally add the negative electrode shell.

[0037] Example 3

[0038] A method for preparing a Bi@NC core-shell structured nanometal battery anode material, comprising the following steps:

[0039] (1) To prepare the spinning solution, first pour in 30 ml of NN dimethylamide (DMF), then slowly add 3 g of polyacrylonitrile (PAN) and 2 g of polymethyl methacrylate (PMMA) to the DMF, heat and stir in an 80°C water bath for 3 h to obtain a yellow viscous solution, then slowly add 1 g of BiCl3 and stir for 8 h to obtain a uniform white solution.

[0040] (2) Using electrospinning technology to obtain three-dimensional carbon fiber continuous film, the steps are as follows: pour the spinning solution into the syringe, connect the needle, then apply high voltage, control the rotation speed of the collecting device and the injection speed, and finally spin the filament onto the aluminum foil. The spinning conditions are: the syringe is 10ml, the inner diameter of the needle is 0.25mm, the rotation speed of the collecting device is 350r / min, the working voltage is 12KV, and the injection speed is 4ml / h.

[0041] (3) Place the spun sample in a vacuum drying oven at 60℃ for 3 hours, and finally anneal it in the air at different temperatures; Annealing conditions: Anneal with N2 / H2 mixed gas, starting temperature is 20℃, heating rate is 2℃ / min, heating rate is 2℃ / min to 350℃, hold for 3 hours, heating rate is 720℃ and hold for 4 hours, cooling rate is 1℃ / min to the starting temperature of 20℃;

[0042] (4) Assemble the battery. The steps are as follows: First, place the positive electrode plate, then place the nanoplate, then place the Bi@NC material, add the electrolyte (35ml), place two layers of PP separator, then add the electrolyte NaPF6 (35ml), place the Bi@NC material, place the nanoplate, place the nickel mesh, spring sheet, and finally add the negative electrode shell.

[0043] Example 4

[0044] A method for preparing a Bi@NC core-shell structured nanometal battery anode material, comprising the following steps:

[0045] (1) To prepare the spinning solution, first pour 15 ml of NN dimethylamide (DMF), then slowly add 1.6 g of polyacrylonitrile (PAN) and 0.6 g of polymethyl methacrylate (PMMA) into the DMF, heat and stir in a water bath at 70°C for 2 h to obtain a yellow viscous solution, then slowly add 0.42 g of BiCl3 and stir for 8 h to obtain a uniform white solution;

[0046] (2) Using electrospinning technology to obtain three-dimensional carbon fiber continuous film, the steps are as follows: pour the spinning solution into the syringe, connect the needle, then apply high voltage, control the rotation speed of the collecting device and the injection speed, and finally spin the filament onto the aluminum foil. The spinning conditions are: the syringe is 10ml, the inner diameter of the needle is 0.25mm, the rotation speed of the collecting device is 350r / min, the working voltage is 12KV, and the injection speed is 4ml / h.

[0047] (3) Place the spun sample in a vacuum drying oven at 60℃ for 5 hours, and finally anneal it in the air at different temperatures; Annealing conditions: Anneal with N2 / H2 mixed gas, starting temperature is 25℃, heating rate is 2℃ / min, heating rate is 2℃ / min to 350℃, hold for 3 hours, heating rate is 650℃ and hold for 8 hours, cooling rate is 1℃ / min to the starting temperature of 25℃;

[0048] (4) Assemble the battery. The steps are as follows: First, place the positive electrode plate, then place the nanoplate, then place the Bi@NC material, add the electrolyte (35ml), place two layers of PP separator, then add the electrolyte NaPF6 (35ml), place the Bi@NC material, place the nanoplate, place the nickel mesh, spring sheet, and finally add the negative electrode shell.

[0049] Example 5

[0050] A method for preparing a Bi@NC core-shell structured nanometal battery anode material, comprising the following steps:

[0051] (1) To prepare the spinning solution, first pour 15 ml of NN dimethylamide (DMF), then slowly add 1.6 g of polyacrylonitrile (PAN) and 0.6 g of polymethyl methacrylate (PMMA) into the DMF, heat and stir in a water bath at 70°C for 2 h to obtain a yellow viscous solution, then slowly add 0.42 g of BiCl3 and stir for 8 h to obtain a uniform white solution;

[0052] (2) Using electrospinning technology to obtain three-dimensional carbon fiber continuous film, the steps are as follows: pour the spinning solution into the syringe, connect the needle, then apply high voltage, control the rotation speed of the collecting device and the injection speed, and finally spin the filament onto the aluminum foil. The spinning conditions are: the syringe is 10ml, the inner diameter of the needle is 0.25mm, the rotation speed of the collecting device is 350r / min, the working voltage is 12KV, and the injection speed is 4ml / h.

[0053] (3) Place the spun sample in a vacuum drying oven at 60°C for 5 hours, and finally anneal it in the air at different temperatures; Annealing conditions: The annealing conditions of the electrospun material can also be: annealing with N2 / H2 mixed gas, starting temperature of 30°C, heating rate of 2°C / min, heating to 350°C at 2°C / min, holding for 3 hours, heating to 700°C and holding for 5 hours, cooling to the starting temperature of 30°C at 1°C / min;

[0054] (4) Assemble the battery. The steps are as follows: First, place the positive electrode plate, then place the nanoplate, then place the Bi@NC material, add the electrolyte (35ml), place two layers of PP separator, then add the electrolyte NaPF6 (35ml), place the Bi@NC material, place the nanoplate, place the nickel mesh, spring sheet, and finally add the negative electrode shell.

Claims

1. A method for preparing a three-dimensional carbon fiber battery of composite Bi@NC core-shell structure, characterized in that, The steps are as follows: firstly, a spinning solution is prepared, then a three-dimensional carbon fiber continuous film is obtained by using an electrostatic spinning method, and then dried in a vacuum drying oven, and finally annealed at different temperatures, the battery is assembled, and a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure is obtained, the preparation steps of the spinning solution are as follows: polyacrylonitrile and polymethyl methacrylate are added to N-N dimethylamide, heated and stirred under the condition of a water bath at 60-80 DEG C for 2-5 hours, then BiCl3 is added, and the stirring reaction is continued for 8-10 hours to obtain the spinning solution, the mass ratio of the polyacrylonitrile, polymethyl methacrylate and BiCl3 is 3-5:2-3:1; The annealing conditions of the electrostatic spinning material are as follows: annealing is carried out with N2 / H2 mixed gas, the starting temperature is 20 DEG C, the heating speed is 2 DEG C / min, the temperature is increased to 350 DEG C at a heating speed of 2 DEG C / min, the temperature is kept for 3 hours, the temperature is increased to 720 DEG C and kept for 4 hours, the temperature is decreased to the starting temperature of 20 DEG C at a cooling speed of 1 DEG C / min, or The annealing conditions of the electrostatic spinning material are as follows: annealing is carried out with N2 / H2 mixed gas, the starting temperature is 25 DEG C, the heating speed is 2 DEG C / min, the temperature is increased to 350 DEG C at a heating speed of 2 DEG C / min, the temperature is kept for 3 hours, the temperature is increased to 650 DEG C and kept for 8 hours, the temperature is decreased to the starting temperature of 25 DEG C at a cooling speed of 1 DEG C / min, or The annealing conditions of the electrostatic spinning material are as follows: annealing is carried out with N2 / H2 mixed gas, the starting temperature is 30 DEG C, the heating speed is 2 DEG C / min, the temperature is increased to 350 DEG C at a heating speed of 2 DEG C / min, the temperature is kept for 3 hours, the temperature is increased to 700 DEG C and kept for 5 hours, the temperature is decreased to the starting temperature of 30 DEG C at a cooling speed of 1 DEG C / min.

2. The method for preparing a three-dimensional carbon fiber battery of composite Bi@NC core-shell structure according to claim 1, characterized in that: The preparation steps of the three-dimensional carbon fiber continuous film obtained by using the electrostatic spinning method are as follows: the spinning solution is poured into a syringe, a needle is connected, then a high voltage of 12 kV is applied, the rotating speed of the collection device and the injection speed are controlled, and finally the silk is spun on an aluminum foil.

3. The method for preparing a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure according to claim 1, characterized in that, The vacuum drying conditions are as follows: 5-7 hours in a vacuum drying oven at 60-80 DEG C.

4. The method for preparing a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure according to claim 1, characterized in that, The steps of assembling the battery are as follows: firstly, the positive electrode sheet is placed, then the sodium sheet is placed, the Bi@NC material is placed, the electrolyte is added dropwise, two layers of pp diaphragm are placed, the electrolyte is added dropwise again, the Bi@NC material is placed, the sodium sheet is placed, the nickel mesh is placed, the spring piece is placed, and finally the negative electrode shell is added.

5. The method for preparing a three-dimensional carbon fiber battery with a composite Bi@NC core-shell structure according to claim 4, characterized in that, The electrolyte is NaPF6.

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