阅读说明：本技术 一种自支撑柔性薄膜及其制备方法和应用 (Self-supporting flexible film and preparation method and application thereof ) 是由 王勤 武旭扬 陈斌 苗鹤 于 2021-07-23 设计创作，主要内容包括：本发明提供了一种自支撑柔性薄膜及其制备方法和应用,所述制备方法包括以下步骤：S10：将钴盐、聚乙烯吡咯烷酮和聚丙烯腈配制成待纺丝溶液,静电纺丝制备复合纤维薄膜；S20：在氮气条件下对所述复合纤维薄膜进行碳化处理,同时加入碳源进行化学气相沉积反应生长碳纳米管,得到三维多孔碳纳米纤维；S30：对所述三维多孔碳纳米纤维进行氧化处理,得到所述自支撑柔性薄膜。本发明提供的自支撑柔性薄膜具有纳米网状结构,可以提高催化剂的担载量；同时,催化剂采用原位生长的方式,进一步提高了催化剂与基底的结合力,降低了界面接触电阻。(The invention provides a self-supporting flexible film and a preparation method and application thereof, wherein the preparation method comprises the following steps: s10: preparing a solution to be spun from cobalt salt, polyvinylpyrrolidone and polyacrylonitrile, and preparing a composite fiber film by electrostatic spinning; s20: carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding a carbon source to perform chemical vapor deposition reaction to grow a carbon nanotube to obtain three-dimensional porous carbon nanofiber; s30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film. The self-supporting flexible film provided by the invention has a nano-mesh structure, and can improve the loading capacity of a catalyst; meanwhile, the catalyst adopts an in-situ growth mode, so that the binding force between the catalyst and the substrate is further improved, and the interface contact resistance is reduced.)

1. A method for preparing a self-supporting flexible film is characterized by comprising the following steps:

s10: preparing a solution to be spun from cobalt salt, polyvinylpyrrolidone and polyacrylonitrile, and preparing a composite fiber film by electrostatic spinning;

s20: carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding a carbon source to perform chemical vapor deposition reaction to grow a carbon nanotube to obtain three-dimensional porous carbon nanofiber;

s30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film.

2. The method according to claim 1, wherein the mass ratio of the cobalt salt, polyvinylpyrrolidone and polyacrylonitrile is (1-2) to (1-3) to (0.5-6).

3. The method according to claim 2, wherein the cobalt salt is one or more of cobalt acetate, cobalt nitrate and cobalt carbonate.

4. The method according to claim 1, wherein the solvent of the solution to be spun is dimethylformamide, and the mass fraction of the solute is 10 to 20%.

5. The preparation method according to claim 1, wherein the mass ratio of the composite fiber membrane to the carbon source is 1 (5-20).

6. The method according to claim 5, wherein the carbon source is one or more of melamine, dicyandiamide, ethylenediamine and methane.

7. The production method according to claim 1, wherein the carbonization treatment is performed under the conditions: controlling the carbonization temperature to be 600-1000 ℃; the carbonization time is 100-140 min.

8. The production method according to claim 1, wherein the oxidation treatment conditions are: under the reaction atmosphere containing oxygen, the oxidation temperature is controlled to be 250-350 ℃, and the oxidation time is controlled to be 20-40 min.

9. A self-supporting flexible film, prepared by the method of any one of claims 1 to 8.

10. A self supporting flexible film as claimed in claim 9, used to make a flexible air cathode.

Technical Field

The invention relates to the field of flexible zinc-air batteries, in particular to a self-supporting flexible film and a preparation method and application thereof.

Background

The air cathode is an important component of the flexible zinc-air battery, and is a place where oxygen reduction (ORR) and Oxygen Evolution (OER) reactions occur during charging and discharging of the battery. The traditional air cathode construction method is that carbon paper, carbon cloth, metal mesh and the like are used as substrates, catalysts, carbon carriers, binders and the like are prepared into slurry according to a certain proportion and coated on the substrates; or the catalyst is grown in situ on the substrate by adopting methods such as hydrothermal reaction, electrodeposition and the like. The air cathode prepared by the traditional method has low stability, and catalyst particles are easy to fall off under the repeated action of external force; in addition, the use of non-conductive polymeric binders can result in increased interfacial contact resistance, affecting electron transport and reaction kinetics; meanwhile, the woven structure of the substrate is too loose, the loading capacity of the catalyst cannot be improved, and the activity is limited.

Disclosure of Invention

Aiming at the problems, the technical scheme provided by the invention abandons the traditional substrates such as carbon paper, carbon cloth, metal mesh and the like, provides a three-dimensional self-supporting carbon nanofiber substrate with a nanoscale and microporous structure, and grows the high-efficiency bifunctional composite catalyst on the substrate in situ.

In one aspect, the present invention provides a method for preparing a self-supporting flexible film, comprising the steps of:

s10: preparing a solution to be spun from cobalt salt, polyvinylpyrrolidone and polyacrylonitrile, and preparing a composite fiber film by electrostatic spinning;

s20: carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding a carbon source to perform chemical vapor deposition reaction to grow a carbon nanotube to obtain three-dimensional porous carbon nanofiber;

s30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film.

Furthermore, the mass ratio of the cobalt salt, the polyvinylpyrrolidone and the polyacrylonitrile is (1-2) to (1-3) to (0.5-6).

Further, the cobalt salt is one or more of cobalt acetate, cobalt nitrate and cobalt carbonate.

Further, the solvent of the solution to be spun is dimethylformamide, and the mass fraction of the solute is 10-20%.

Further, the mass ratio of the composite fiber film to the carbon source is 1 (5-20).

Further, the carbon source is one or more of melamine, dicyandiamide, ethylenediamine and methane.

Further, the carbonization treatment conditions are as follows: controlling the carbonization temperature to be 600-1000 ℃; the carbonization time is 100-140 min.

Further, the conditions of the oxidation treatment are as follows: under the reaction atmosphere containing oxygen, the oxidation temperature is controlled to be 250-350 ℃, and the oxidation time is controlled to be 20-40 min.

In another aspect, the present invention provides a self-supporting flexible film prepared by the above method.

Further, the self-supporting flexible film may be used to make a flexible air cathode.

The technology of the present invention will be described in detail below in order to make those skilled in the art more understand the technical solution of the present invention.

In the preparation method, the composite fiber film is prepared by adopting an electrostatic spinning technology, and a precursor of the catalyst is anchored on the composite fiber film; then growing a catalyst on the composite fiber film in situ by a chemical vapor deposition method.

The composite fiber film takes polyacrylonitrile as a framework, and the surface of the composite fiber film is coated with cobalt salt and polyvinylpyrrolidone as precursors of catalysts. The specific preparation method comprises the following steps:

s11: dissolving cobalt salt and polyvinylpyrrolidone in dimethyl formamide according to the mass ratio of (1-2) to (1-3), and stirring in a water bath at 50 ℃ for 2 hours to fully dissolve the cobalt salt and the polyvinylpyrrolidone; controlling the concentration of the solution to be 10-20 wt%; to obtain a first solution.

S12: dissolving polyacrylonitrile in dimethylformamide, stirring in 80 deg.C water bath for 1 hr to dissolve completely; controlling the concentration of the solution to be 10 wt%; and obtaining a second solution.

S13: mixing the first solution and the second solution, and stirring in a water bath at 80 ℃ for 24 hours to form the solution to be spun; the mass ratio of polyacrylonitrile to polyvinylpyrrolidone is controlled to be 1 (0.5-2).

S14: adopting electrostatic spinning equipment, adjusting the applied voltage to be 12-18kV, and controlling the feeding speed of the solution to be spun to be 0.1 mL/h; the distance between the receiver and the nozzle on the equipment is 12-18 cm; and obtaining the composite fiber film.

The composite fiber film needs to be dried and stabilized to be used for the subsequent process; the drying condition is preferably vacuum drying at 70 ℃ for 24 h; the stabilizing treatment conditions are as follows: under the air atmosphere, the temperature is increased to 250 ℃ at the speed of 1 ℃/min and kept for 2 h; the temperature was then raised to 350 ℃ at a rate of 1 ℃/min for 3h under a nitrogen atmosphere. The treatment can exert the organic solvent and the additive, and further stabilize the three-dimensional network structure of the composite fiber film.

Further, preparing the self-supporting flexible film by growing a catalyst on the composite fiber film in situ; the method does not adopt adhesive, enhances the binding force between the catalyst and the substrate, and greatly improves the loading capacity of the catalyst on the substrate, thereby improving the electron transmission rate; on the other hand, the catalyst comprises cobalt oxide with OER catalytic advantage and nitrogen-doped carbon nanotubes with ORR catalytic advantage, and the cobalt oxide and the nitrogen-doped carbon nanotubes are compounded in situ and have ORR/OER dual-functional catalytic activity. Therefore, the self-supporting flexible film and the flexible air cathode prepared by the method provided by the invention have higher surface area and porosity than carbon cloth and foam metal.

Specifically, the in-situ growth of the catalyst on the composite fiber film comprises the following steps:

s20: and carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding a carbon source to perform chemical vapor deposition reaction to grow a carbon nanotube to obtain the three-dimensional porous carbon nanofiber.

S30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film.

Wherein, in step S20, the carbonization temperature is 600-1000 ℃, the carbonization time is 100-140min, and the temperature rise rate is 5 ℃/min; the mass ratio of the composite fiber film to the carbon source is 1 (5-20); the selection of the carbon source includes, but is not limited to: melamine, dicyandiamide, ethylenediamine and methane.

In the high-temperature carbonization process, the polymer skeleton in the composite fiber film is converted into three-dimensional porous carbon nanofibers, and meanwhile, cobalt ions Co on the surfaces of the fibers²⁺Reduced into metal cobalt nano particles which can be used as a catalyst to assist a carbon source to vertically and directionally grow a carbon nano tube array on the surface of the carbon nano fiber. Because the method is carried out in a nitrogen atmosphere, the carbon nano tube is doped with partial nitrogen element in the growth process.

In step S30, the oxidation treatment conditions are: under the reaction atmosphere containing oxygen, the oxidation temperature is controlled to be 250-350 ℃, and the oxidation time is controlled to be 20-40 min.

Further, the self-supporting flexible film may be used directly as a flexible air cathode.

In summary, the technical solution provided by the present invention has one or more of the following advantages:

1. the self-supporting air cathode has a nano-mesh structure, so that the loading capacity of the catalyst can be improved; meanwhile, the catalyst adopts an in-situ growth mode, so that the binding force between the catalyst and the substrate is further improved, and the interface contact resistance is reduced.

2. By skillful design of the catalyst, the Co particles reduced in the carbonization process are utilized to catalyze and grow the carbon nanotube array, thereby realizing Co₃O₄And N-CNT, and has the double-function catalytic activity of enhancing oxygen reduction (ORR) and Oxygen Evolution (OER) of the catalyst.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a microtopography of the self-supporting flexible film provided in example 1.

Figure 2 is a XRD phase test curve of the self-supporting flexible film provided in example 1.

Fig. 3 is a disk electrode test curve of the flexible air cathode provided in example 1.

Fig. 4 is a disk electrode test curve of the flexible air cathode provided in example 1.

Fig. 5 is a discharge performance curve of the flexible zinc-air battery provided in example 1.

Fig. 6 is a cycle performance test curve of the flexible zinc-air battery provided in example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

[ example 1 ]

The invention provides a preparation method of a self-supporting flexible film, which comprises the following steps:

s11: dissolving cobalt salt and polyvinylpyrrolidone in dimethylformamide, and stirring in a water bath at 50 ℃ for 2 hours to fully dissolve the cobalt salt and the polyvinylpyrrolidone; to obtain a first solution.

S12: dissolving polyacrylonitrile in dimethylformamide, stirring in 80 deg.C water bath for 1 hr to dissolve completely; and obtaining a second solution.

S13: and mixing the first solution and the second solution, and stirring in a water bath at 80 ℃ for 24 hours to form the solution to be spun.

S14: adopting electrostatic spinning equipment, adjusting the applied voltage to be 16kV, and controlling the feeding speed of the solution to be spun to be 0.1 mL/h; the distance between the receiver and the nozzle on the device is 16 cm; and obtaining the composite fiber film.

The composite fiber film needs to be dried and stabilized to be used for the subsequent process; the drying condition is preferably vacuum drying at 70 ℃ for 24 h; the stabilizing treatment conditions are as follows: under the air atmosphere, the temperature is increased to 250 ℃ at the speed of 1 ℃/min and kept for 2 h; the temperature was then raised to 350 ℃ at a rate of 1 ℃/min for 3h under a nitrogen atmosphere. The treatment can exert the organic solvent and the additive, and further stabilize the three-dimensional network structure of the composite fiber film.

S20: and carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding a carbon source to perform chemical vapor deposition reaction to grow a carbon nanotube to obtain the three-dimensional porous carbon nanofiber.

S30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film.

In this embodiment, the mass ratio of the cobalt salt, polyvinylpyrrolidone and polyacrylonitrile is controlled to be 1: 1: 1; wherein the cobalt salt is cobalt nitrate; and the mass fraction of the solute of the first solution and the second solution is 10 percent.

The carbon source is methane, and the mass ratio of the composite fiber film to the carbon source is 1: 5. The carbonization treatment conditions are as follows: the carbonization temperature is 800 ℃, and the carbonization time is 120 min.

The conditions of the oxidation treatment are as follows: under the reaction atmosphere containing oxygen, the oxidation temperature is controlled to be 300 ℃, and the oxidation time is controlled to be 30 min.

Referring to fig. 1, the microstructure of the self-supporting flexible film of this embodiment is observed by Scanning Electron Microscopy (SEM), the coarse network structure is a carbon nanofiber substrate, the curls are carbon nanotubes, and the cobalt oxide is nanoparticles, which are not shown in the figure.

Referring to fig. 2, phase analysis of the self-supporting flexible thin film is performed by using a high-resolution X-ray diffractometer (XRD), and it can be seen that cobalt exists in the form of cobalt oxide in the self-supporting flexible thin film, which can be used as an effective catalytic component.

Referring to fig. 3 and 4, the intrinsic catalytic activity of oxygen reduction (ORR) and Oxygen Evolution (OER) of the catalyst material in the self-supporting air cathode was tested using an electrochemical workstation in combination with a rotating disk electrode, and the ORR half-wave potential, OER overpotential @ j ═ 10mA/cm were measured using Linear Sweep Voltammetry (LSV)²And OER-ORR potential difference delta E and other main electrochemical parameters, and evaluating the intrinsic catalytic activity of the catalyst. Currently, the best ORR catalytic activity is Pt and its alloy, and the best OER catalytic activity is Ir, Ru and its oxide.

In FIG. 3, (ii) is CNF, ((ii) is Co @ CNF, ((iii) is Co/N-CNT @ CNF, ((iii) is Co)₃O₄N-CNT @ CNF, (-) Pt/C; it can be seen that the ORR half-wave potential of curve # iv is most positive, about 0.8V, close to the value of Pt/C.

In FIG. 4, (ii) is CNF, ((ii) is Co @ CNF, ((iii) is Co/N-CNT @ CNF, ((iii) is Co)₃O₄N-CNT @ CNF, # IrO₂(ii) a As can be seen, the curve No. 4 is at 10mA/cm²The lower potential is about 1.58V to IrO₂The performance of (2) is also good. Therefore, the self-supporting flexible film provided by the invention has good ORR and OER dual-functional catalytic activity.

Referring to fig. 5 and 6, the self-supporting flexible film is used as a flexible air cathode, a high-purity zinc foil with the thickness of 0.1mm is used as an anode, a Polypropylene (PAA) -based gel electrolyte is used as an electrolyte, a flexible zinc air battery with a sandwich structure is assembled, and the charging and discharging performance and the cycling stability of the flexible zinc air battery are tested by using battery testing equipment. The maximum power density of the discharge curve of the flexible zinc-air battery is about 118Mw/cm²(ii) a And the cycling stability is good, after 400 charging and discharging cycles are completed, the discharging voltage is not obviously attenuated, and the charging voltage is increased by 3.6%.

[ example 2 ]

The embodiment provides a preparation method of a self-supporting flexible film, which comprises the following steps:

s11: dissolving cobalt acetate and polyvinylpyrrolidone in dimethyl formamide according to the mass ratio of 1:3, and stirring in a water bath at 50 ℃ for 2 hours to fully dissolve the cobalt acetate and the polyvinylpyrrolidone; controlling the concentration of the solution to be 20 wt%; to obtain a first solution.

S12: dissolving polyacrylonitrile in dimethylformamide, stirring in 80 deg.C water bath for 1 hr to dissolve completely; controlling the concentration of the solution to be 10 wt%; and obtaining a second solution.

S13: mixing the first solution and the second solution, and stirring in a water bath at 80 ℃ for 24 hours to form the solution to be spun; the mass ratio of polyacrylonitrile to polyvinylpyrrolidone is controlled to be 1: 0.5.

S14: adopting electrostatic spinning equipment, adjusting the applied voltage to be 12kV, and controlling the feeding speed of the solution to be spun to be 0.1 mL/h; the distance between the receiver and the nozzle on the device is 12 cm; and obtaining the composite fiber film.

The composite fiber film needs to be dried and stabilized to be used for the subsequent process; the drying condition is preferably vacuum drying at 70 ℃ for 24 h; the stabilizing treatment conditions are as follows: under the air atmosphere, the temperature is increased to 250 ℃ at the speed of 1 ℃/min and kept for 2 h; the temperature was then raised to 350 ℃ at a rate of 1 ℃/min for 3h under a nitrogen atmosphere. The treatment can exert the organic solvent and the additive, and further stabilize the three-dimensional network structure of the composite fiber film.

S20: and carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding dicyandiamide to perform chemical vapor deposition reaction to grow carbon nanotubes to obtain the three-dimensional porous carbon nanofiber. Wherein the mass ratio of the composite fiber film to the dicyandiamide is 1:20, and the carbonization treatment conditions are as follows: the carbonization temperature is 606 ℃, and the carbonization time is 140 min.

S30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film. The conditions of the oxidation treatment are as follows: under the reaction atmosphere containing oxygen, the oxidation temperature is controlled to be 250 ℃, and the oxidation time is controlled to be 40 min.

[ example 3 ]

The embodiment provides a preparation method of a self-supporting flexible film, which comprises the following steps:

s11: dissolving cobalt carbonate and polyvinylpyrrolidone in dimethyl formamide according to the mass ratio of 2:1, and stirring in a water bath at 50 ℃ for 2 hours to fully dissolve the cobalt carbonate and the polyvinylpyrrolidone; controlling the concentration of the solution to be 15 wt%; to obtain a first solution.

S12: dissolving polyacrylonitrile in dimethylformamide, stirring in 80 deg.C water bath for 1 hr to dissolve completely; controlling the concentration of the solution to be 10 wt%; and obtaining a second solution.

S13: mixing the first solution and the second solution, and stirring in a water bath at 80 ℃ for 24 hours to form the solution to be spun; the mass ratio of polyacrylonitrile to polyvinylpyrrolidone is controlled to be 1: 2.

S14: adopting electrostatic spinning equipment, adjusting the applied voltage to be 18kV, and controlling the feeding speed of the solution to be spun to be 0.1 mL/h; the distance between the receiver and the nozzle on the device is 18 cm; and obtaining the composite fiber film.

The composite fiber film needs to be dried and stabilized to be used for the subsequent process; the drying condition is preferably vacuum drying at 70 ℃ for 24 h; the stabilizing treatment conditions are as follows: under the air atmosphere, the temperature is increased to 250 ℃ at the speed of 1 ℃/min and kept for 2 h; the temperature was then raised to 350 ℃ at a rate of 1 ℃/min for 3h under a nitrogen atmosphere. The treatment can exert the organic solvent and the additive, and further stabilize the three-dimensional network structure of the composite fiber film.

S20: and carbonizing the composite fiber film under the condition of nitrogen, and simultaneously adding melamine to perform chemical vapor deposition reaction to grow carbon nanotubes to obtain the three-dimensional porous carbon nanofiber. Wherein the mass ratio of the composite fiber film to the melamine is 1:12, and the carbonization treatment conditions are as follows: the carbonization temperature is 1000 ℃, and the carbonization time is 100 min.

S30: and carrying out oxidation treatment on the three-dimensional porous carbon nanofiber to obtain the self-supporting flexible film. The conditions of the oxidation treatment are as follows: under the reaction atmosphere containing oxygen, the oxidation temperature is controlled to be 350 ℃, and the oxidation time is controlled to be 20 min.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.