CN115897067A - Antimony-based hierarchical porous carbon fiber negative electrode material and preparation method and application thereof - Google Patents

Abstract

The invention discloses an antimony-based hierarchical porous carbon fiber cathode material and a preparation method and application thereof. The method comprises the following steps: (1) Mixing antimony salt, polyacrylonitrile, polyvinylpyrrolidone and a solvent to obtain a precursor solution; (2) Carrying out electrostatic spinning treatment on the precursor solution to obtain a precursor; (3) And annealing the precursor to obtain the antimony-based hierarchical porous carbon fiber negative electrode material. The method has the advantages of simple preparation process, high yield, low production cost, and contribution to obtaining the antimony-based graded-pore carbon fiber cathode material with high capacity, stable structure and uniform appearance.

Description

Antimony-based hierarchical porous carbon fiber negative electrode material and preparation method and application thereof

Technical Field

The invention belongs to the field of batteries, and particularly relates to an antimony-based hierarchical porous carbon fiber negative electrode material, and a preparation method and application thereof.

Background

Lithium ion batteries have been the main power source of electric vehicles and portable electronic devices due to their high energy density and power density and reliable cycling stability, but they have been developed vigorously in recent years due to limited lithium resources, low cost of potassium and wide distribution in earth's crust, which makes it a substitute for lithium batteries. From the development of potassium ion batteries, the electrochemical performance of potassium ion batteries is largely dependent on the structure and performance of the electrode materials used. However, due to the larger radius of the potassium ion, the intercalation and deintercalation in the charging and discharging process needs a proper pore diameter to better participate in the reaction, and more capacity is contributed.

Disclosure of Invention

The present application is primarily based on the following problems and findings:

the carbon material has stable structure and good reversibility, and is not only commercially applied to lithium ion batteries, but also widely researched in potassium ion batteries. However, in order to prevent the carbon material from being oxidized, the preparation of the carbon-based material needs to be performed under an expensive nitrogen or inert atmosphere, and in order to obtain the porous structure carbon material, an expensive template needs to be introduced and then removed by means of etching with strong acid, strong base and the like, so that the preparation process is complicated and the cost is high; on the other hand, the carbon material has low theoretical capacity, so that the carbon material has poor effect in the circulation process, and is often required to be compounded with other materials with high theoretical capacity, and the antimony-based material is considered to be one of promising candidates due to high theoretical capacity and proper working voltage, but large volume expansion is often generated in the circulation process, so that the electrode is crushed, and the circulation performance is poor. Therefore, it is a great challenge to find a method for preparing a carbon-based material with a porous structure at low cost and high efficiency.

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide an antimony-based graded-pore carbon fiber negative electrode material, and a preparation method and application thereof. The method has the advantages of simple preparation process, high yield and low production cost, and is favorable for obtaining the antimony-based hierarchical porous carbon fiber cathode material with high capacity, stable structure and uniform appearance, and the cathode material can be used for a potassium ion battery cathode, so that the battery capacity is improved, and the electrochemical performance is improved.

In one aspect of the invention, a method of making an antimony-based graded pore carbon fiber anode material is presented. According to an embodiment of the invention, the method comprises:

(1) Mixing antimony salt, polyacrylonitrile, polyvinylpyrrolidone and a solvent to obtain a precursor solution;

(2) Carrying out electrostatic spinning treatment on the precursor solution to obtain a precursor;

(3) And annealing the precursor to obtain the antimony-based graded-pore carbon fiber negative electrode material.

The method for preparing the antimony-based graded-pore carbon fiber negative electrode material in the embodiment of the invention at least has the following beneficial effects: 1) The antimony salt and the carbon-based material are compounded, the prepared antimony-based hierarchical porous carbon fiber negative electrode material not only contains an antimony-based material with higher theoretical capacity, but also has a stable structure and a three-dimensional structure, can provide stable frame support, effectively avoids electrode crushing caused by larger volume expansion of the antimony-based material in the circulation process, and is beneficial to increasing the capacity of the battery and improving the cycle performance and the rate capability of the battery; 2) Pore-forming agents are not added in the preparation process, and the pore structure design is realized by utilizing the thermal decomposition difference of the polyacrylonitrile and the polyvinylpyrrolidone, so that on one hand, the raw material types can be reduced, the process flow is simplified, and the subsequent annealing treatment process can be carried out in the air atmosphere, so that the operation difficulty, the raw material cost and the processing cost are reduced, and on the other hand, the proportion of the polyacrylonitrile and the polyvinylpyrrolidone is favorably changed to conveniently and flexibly adjust the mesoporous structure; 3) The precursor obtained by adopting electrostatic spinning treatment is of a nanofiber structure, has a large specific surface area and a rapid electron transmission path, and is beneficial to enhancing the electrochemical performance of the battery; 4) The method does not need to introduce a high-price and complex template, does not need to adopt an etching means, does not need to introduce a pore-forming agent, has simple preparation process and lower production cost, and is beneficial to industrial production.

In addition, the method for preparing the antimony-based graded-pore carbon fiber anode material according to the embodiment of the invention can also have the following additional technical characteristics:

in some embodiments of the present invention, in the step (1), the mass ratio of the polyacrylonitrile to the polyvinylpyrrolidone is 0.5 to 1.8, preferably 5: (3-5).

In some embodiments of the invention, the antimony salt comprises antimony chloride and the solvent is N, N-dimethylformamide.

In some embodiments of the present invention, in the step (1), based on the total mass of the antimony salt, the polyacrylonitrile and the polyvinylpyrrolidone, the mass ratio of the antimony salt is 10% to 40%.

In some embodiments of the invention, in step (2), the electrospinning process satisfies at least one of the following conditions: the spinning voltage is 15-25 kV, the advancing speed of the injector is 0.6-1.2 ml/h, the distance between the needle head and the roller is 10-20 cm, the rotating speed of the roller is 50-200 r/min, the humidity is 20-50%, and the temperature is 30-40 ℃.

In some embodiments of the invention, in step (3), the annealing treatment is performed under an air atmosphere.

In some embodiments of the invention, the annealing treatment temperature is 423-600 ℃ and the time is 1-4 h.

In some embodiments of the invention, the antimony-based graded pore carbon fiber anode material has an average pore size of 2 to 10nm.

In another aspect of the invention, the invention provides an antimony-based hierarchical porous carbon fiber negative electrode material prepared by the method for preparing the antimony-based hierarchical porous carbon fiber negative electrode material. Compared with the prior art, the antimony-based hierarchical pore carbon fiber negative electrode material is simple in production process, low in production cost, high in specific capacity, good in cycle performance and rate capability, and capable of being used for preparing a potassium ion battery.

In yet another aspect of the present invention, a negative electrode sheet is provided. According to an embodiment of the invention, the negative plate comprises the antimony-based graded porous carbon fiber negative electrode material or the antimony-based graded porous carbon fiber negative electrode material prepared by the method for preparing the antimony-based graded porous carbon fiber negative electrode material. Compared with the prior art, the cathode plate has higher theoretical capacity and better structural stability, and can effectively improve the capacity, the cycle performance and the rate performance of the battery.

In yet another aspect, the present invention is directed to a potassium ion battery. According to the embodiment of the invention, the potassium ion battery comprises the negative electrode plate, and/or the antimony-based graded porous carbon fiber negative electrode material prepared by the method for preparing the antimony-based graded porous carbon fiber negative electrode material. Compared with the prior art, the battery has higher specific capacity, and has better cycle performance and rate capability.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a flow diagram of a method of making an antimony-based graded pore carbon fiber anode material according to one embodiment of the invention.

Fig. 2 is a thermal decomposition curve of Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) in air according to an embodiment of the present invention, wherein (a) in fig. 2 is a Thermogravimetric (TG) curve of PAN and PVP in air, and (b) a thermogravimetric Differential (DTG) curve of PAN and PVP in air.

FIG. 3 is a comparative scanning electron microscope image of the antimony-based hierarchical porous carbon fiber negative electrode materials obtained in examples 1 to 3 of the present invention, wherein (a), (b), and (c) in FIG. 3 are scanning electron microscope images of the antimony-based hierarchical porous carbon fiber negative electrode materials obtained in examples 1, 2, and 3, respectively.

Fig. 4 is an adsorption-desorption temperature map and a negative electrode material pore diameter distribution map of the antimony-based hierarchical porous carbon fiber negative electrode material prepared according to example 1 of the present invention.

Fig. 5 is an adsorption-desorption temperature map and an anode material pore diameter distribution map of the antimony-based hierarchical porous carbon fiber anode material prepared according to example 2 of the present invention.

Fig. 6 is an adsorption-desorption temperature contour map and an anode material pore diameter distribution map of the antimony-based hierarchical porous carbon fiber anode material prepared according to example 3 of the present invention.

Fig. 7 is an adsorption-desorption temperature line graph and an anode material pore diameter distribution graph of the antimony-based hierarchical porous carbon fiber anode material prepared according to comparative example 1 of the present invention.

Fig. 8 is an adsorption-desorption temperature map and a pore diameter distribution map of the antimony-based hierarchical porous carbon fiber anode material prepared according to comparative example 2 of the present invention.

Fig. 9 is an adsorption-desorption temperature map and a pore diameter distribution map of the antimony-based hierarchical porous carbon fiber anode material prepared according to comparative example 3 of the present invention.

FIG. 10 is a graph of adsorption-desorption isotherm and pore diameter distribution of the anode material of antimony-based hierarchical porous carbon fiber anode material prepared according to comparative example 4 of the present invention.

Fig. 11 is an X-ray diffraction pattern of antimony-based graded-pore carbon fiber anode material prepared according to example 1 of the present invention.

FIG. 12 is a graph comparing the cycle performance of potassium ion batteries assembled with antimony-based hierarchical porous carbon fiber anode materials prepared according to examples 1-3 of the present invention.

Fig. 13 is a graph of rate performance of potassium ion batteries assembled with antimony-based graded pore carbon fiber anode materials prepared according to example 1 of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In one aspect of the invention, a method of making an antimony-based graded pore carbon fiber anode material is presented. According to an embodiment of the invention, as understood in connection with fig. 1, the method comprises:

s100: mixing antimony salt, polyacrylonitrile, polyvinylpyrrolidone and solvent to obtain precursor solution

According to the embodiment of the invention, antimony salt and a carbon-based material are mixed to obtain a precursor solution, and then the precursor solution is subjected to a subsequent process, so that the hierarchical porous carbon fiber anode material with antimony base and carbon base can be obtained finally, the antimony base material is introduced, the specific capacity of the anode material is favorably improved, the carbon-based material can provide stable frame support for the antimony base material, the possibility of electrode crushing caused by large volume expansion of the antimony base material in the circulation process is effectively reduced, and the cycle performance and the rate capability of the battery are favorably improved.

According to the embodiment of the invention, when the mixing treatment is carried out, a pore-forming agent (such as diisopropyl azodicarboxylate) is not added or added, a high-price and complex template is not required to be introduced, an etching means is not required, and the thermal decomposition difference of polyacrylonitrile and polyvinylpyrrolidone (understood by referring to fig. 2) is utilized, so that polyvinylpyrrolidone can be decomposed in a large amount in the subsequent annealing treatment process, and polyacrylonitrile is only decomposed in a small part, thereby realizing the pore structure design. The ratio of polyacrylonitrile to polyvinylpyrrolidone can be changed, so that the pore size structure of the obtained final product can be conveniently and flexibly adjusted, and for example, an antimony-based hierarchical pore carbon fiber cathode material with a mesoporous structure can be selectively obtained according to the actual requirements of a potassium ion battery.

According to some embodiments of the present invention, the mass ratio of polyacrylonitrile to polyvinylpyrrolidone may be 0.5 to 1.8, for example, may be 0.6, 0.9, 1.2, 1.5, or 1.7, and preferably may be 5: (3-5), for example, it may be 5/3.5, 5/4 or 5/4.5, etc., and the inventors found that the change of the mass ratio of polyacrylonitrile to polyvinylpyrrolidone has a significant influence on the pore size structure of the finally obtained antimony-based hierarchical pore carbon fiber negative electrode material, wherein if the mass ratio of polyacrylonitrile to polyvinylpyrrolidone is too large, the pore size of the formed final product is smaller, which is more favorable for obtaining a negative electrode material with a microporous structure, and if the mass ratio of polyacrylonitrile to polyvinylpyrrolidone is too small, the pore size of the final product is easily larger, and if the pore size is too large or too small, which leads to the reduction of the adsorption capacity and the specific surface area of the negative electrode material, and further leads to the reduction of the specific capacity. Further, by controlling the mass ratio of PAN to PVP to be 5: (3-5), the method is also more favorable for obtaining the ordered mesoporous cathode material with the average pore diameter of 2-10 nm and concentrated particle size distribution, so that the cathode material has stronger adsorption capacity and larger specific surface area, thereby not only storing charges, but also promoting the migration of electrolyte ions (such as potassium ions) under the high-load condition, being favorable for improving the specific capacity of the cathode material, and being widely applied to potassium ion batteries.

According to the embodiment of the invention, the antimony salt in the invention can be soluble antimony salt, and the purpose of introducing the solvent is to achieve sufficient dissolution and dispersion of the antimony salt, polyacrylonitrile and polyvinylpyrrolidone and meet the spinnability requirement of the precursor solution, wherein the solvent can preferably adopt a volatile solvent or a solvent with a boiling point significantly lower than the annealing treatment temperature, so that the solvent can be sufficiently volatilized during the subsequent annealing treatment, and the situation that the antimony-based hierarchical porous carbon fiber negative electrode material contains residual solvent to limit the application of the antimony-based hierarchical porous carbon fiber negative electrode material is avoided. In addition, the mixing sequence of the antimony salt, the polyacrylonitrile, the polyvinylpyrrolidone and the solvent during the mixing treatment is not particularly limited, and a person skilled in the art can flexibly select the antimony salt according to the actual situation, for example, the antimony salt can be dissolved in the solvent first, and then the polyacrylonitrile and the polyvinylpyrrolidone are added to uniformly mix the antimony salt, the polyacrylonitrile and the polyvinylpyrrolidone, so that the antimony salt, the polyacrylonitrile and the polyvinylpyrrolidone can be fully dispersed, and the precursor structure obtained after the electrostatic spinning treatment is more uniform.

According to the embodiment of the invention, based on the total mass of the antimony salt, the polyacrylonitrile and the polyvinylpyrrolidone, the mass ratio of the antimony salt can be 10% -40%, for example, 15%, 20%, 25%, 30% or 35%, and the inventors found that if the amount of the antimony salt is too small, the prepared antimony-based hierarchical porous carbon fiber negative electrode material is difficult to reach a higher theoretical capacity, and is not beneficial to improving the battery capacity; if the amount of the antimony salt is too large, more antimony-based materials generate larger volume expansion in the cycle process of the battery, and may have negative effects on the service performance and the structural stability of the electrode material, thereby affecting the cycle performance of the battery. According to the invention, the mass ratio of the antimony salt is controlled within the range, so that the finally prepared cathode material has better electrochemical performance.

S200: carrying out electrostatic spinning treatment on the precursor solution to obtain a precursor

According to the embodiment of the invention, the precursor of the nanofiber structure can be obtained through electrostatic spinning treatment, and the nanofiber structure has higher surface-to-volume ratio, controllable fiber diameter, surface morphology, porous structure and mechanical strength, so that the finally obtained cathode material has larger specific surface area and a fast electron transmission path, and is more favorable for enhancing the electrochemical performance of a battery.

According to the embodiment of the invention, in the electrostatic spinning treatment process, the spinning voltage may be 15 to 25kV, for example, 18kV, 20kV, 22kV or 24kV, etc.; the speed of the injector may be 0.6 to 1.2ml/h, for example 0.8ml/h, 1ml/h or 1.1ml/h, etc., the distance between the needle and the roller may be 10 to 20cm, for example 12cm, 14cm, 16cm or 18cm, etc., the rotation speed of the roller may be 50 to 200 revolutions/min, for example 60 revolutions/min, 90 revolutions/min, 120 revolutions/min, 150 revolutions/min or 180 revolutions/min, etc., the humidity may be 20 to 50%, for example 25%, 30%, 40% or 45%, etc., and the temperature may be 30 to 40 ℃, for example 32 ℃, 34 ℃, 36 ℃ or 38 ℃, etc. According to the invention, by controlling the electrostatic spinning to be carried out under the above conditions, the nanofiber structure precursor with higher surface volume ratio, uniform fiber diameter, surface morphology, porous structure and better mechanical strength can be obtained better.

S300: annealing the precursor to obtain the antimony-based hierarchical porous carbon fiber negative electrode material

According to the embodiment of the invention, the antimony-based carbon fiber with a porous structure can be obtained by annealing the precursor. The annealing treatment can be carried out in the air atmosphere, and the inventor finds that polyacrylonitrile and polyvinylpyrrolidone have thermal decomposition difference in the air, and by utilizing the difference, the polyvinylpyrrolidone can be decomposed in a large amount by controlling the temperature of the annealing treatment, and the polyacrylonitrile is only decomposed in a small part, so that ideal pore-size structure distribution is realized, wherein the annealing treatment in the air can avoid expensive nitrogen or inert gas, and meanwhile, the process of introducing and removing a complex template is not needed, so that the production cost can be reduced, and the process flow can be simplified.

According to the embodiment of the present invention, the temperature of the annealing treatment may be 423 to 600 ℃, for example 425 ℃, 450 ℃, 480 ℃,500 ℃, 520 ℃, 550 ℃, or 580 ℃, and the time may be 1 to 4 hours, for example, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or 3.5 hours. The inventors found that, as understood from fig. 2, in the air, polyacrylonitrile (PAN) starts a thermal decomposition reaction at about 332.21 ℃ and loses a part of its weight by a cyclization reaction, and loses most of its weight by a dehydrogenation reaction at about 569.35 ℃; and Polyvinylpyrrolidone (PVP) generates main thermal decomposition reaction at 423.04 ℃ or so to lose most weight, if the annealing treatment temperature is too high or the annealing treatment time is too long, the pyrolysis degree is easily caused to be too high, the pore diameter generated by the negative electrode material is too large, the problem of collapse of a porous structure due to insufficient integral strength of a product is easily caused, the cycle performance of the negative electrode material is influenced, if the annealing treatment temperature is too low or the annealing treatment time is too short, the pyrolysis degree is easily caused to be insufficient, and proper pore diameter distribution is difficult to obtain. According to the invention, by controlling the annealing temperature and time within the above range, the pyrolysis degree of PAN and PVP can be effectively controlled, so that the ordered mesoporous negative electrode material with concentrated particle size distribution can be more favorably obtained, and the application of the ordered mesoporous negative electrode material in a potassium ion battery is more favorable for improving the electrochemical performance and energy density of the battery. In addition, the specific equipment used for the annealing treatment in the present invention is not particularly limited, and those skilled in the art can flexibly select the equipment according to actual conditions, and for example, a muffle furnace or the like can be used.

According to the embodiment of the invention, after the annealing treatment, the obtained product can be further subjected to crushing or grinding treatment.

According to the embodiment of the invention, the average pore diameter of the antimony-based hierarchical pore carbon fiber anode material obtained through annealing treatment can be 2-10 nm, such as 2nm, 5nm, 7nm or 9 nm. The inventor finds that the optimal pore size ranges required for realizing ion intercalation and deintercalation are different for different ion batteries, for example, the optimal pore size ranges of electrode materials required for a sodium ion battery, a lithium ion battery and a potassium ion battery are different, while for a potassium ion battery, the inventor finds that controlling the pore size of a negative electrode material to be in the above ranges is more favorable for obtaining stronger adsorption capacity and specific surface area and promoting migration of potassium ions under high load conditions, so that the potassium ion battery used as the negative electrode material of the potassium ion battery is more favorable for improving the capacity density and electrochemical performance of the potassium ion battery, and the potassium ion battery shows excellent electrochemical performance, and has the advantages of high specific capacity, good cycle performance, excellent rate performance and the like.

In summary, the method for preparing the antimony-based hierarchical porous carbon fiber negative electrode material in the embodiment of the invention at least has the following beneficial effects: 1) The antimony-based hierarchical porous carbon fiber cathode material prepared by compounding antimony salt with a carbon-based material not only contains an antimony-based material with higher theoretical capacity, but also has a stable structure and a three-dimensional structure, can provide stable frame support, effectively avoids electrode crushing caused by larger volume expansion of the antimony-based material in the circulation process, and is beneficial to increasing the battery capacity and improving the cycle performance and the rate capability of the battery; 2) Pore-forming agents are not added in the preparation process, and the pore structure design is realized by utilizing the thermal decomposition difference of the polyacrylonitrile and the polyvinylpyrrolidone, so that on one hand, the raw material types can be reduced, the process flow is simplified, and the subsequent annealing treatment process can be carried out in the air atmosphere, so that the operation difficulty, the raw material cost and the processing cost are reduced, and on the other hand, the proportion of the polyacrylonitrile and the polyvinylpyrrolidone is favorably changed to conveniently and flexibly adjust the mesoporous structure; 3) The precursor obtained by adopting electrostatic spinning treatment is of a nanofiber structure, has a large specific surface area and a rapid electron transmission path, and is beneficial to enhancing the electrochemical performance of the battery; 4) The method does not need to introduce a high-price and complex template, does not need to adopt an etching means, does not need to introduce a pore-forming agent, has simple preparation process and lower production cost, and is beneficial to industrial production.

In still another aspect of the present invention, the present invention provides an antimony-based graded porous carbon fiber negative electrode material prepared by the above method for preparing an antimony-based graded porous carbon fiber negative electrode material. Compared with the prior art, the antimony-based hierarchical porous carbon fiber negative electrode material is simple in production process, low in production cost, high in specific capacity, good in cycle performance and rate capability, and capable of being used for preparing a potassium ion battery.

In yet another aspect of the present invention, a negative electrode sheet is provided. According to the embodiment of the invention, the negative plate comprises the antimony-based graded-hole carbon fiber negative electrode material or the antimony-based graded-hole carbon fiber negative electrode material prepared by the method for preparing the antimony-based graded-hole carbon fiber negative electrode material. The negative plate has all the technical characteristics and effects of the antimony-based graded porous carbon fiber negative electrode material and the method for preparing the antimony-based graded porous carbon fiber negative electrode material, and details are not repeated here. In general, the cathode plate has high theoretical capacity and good structural stability, and can effectively improve the capacity, the cycle performance and the rate performance of the battery. According to an embodiment of the present invention, the negative electrode sheet may include a current collector and an active material layer formed on a surface of the current collector, and the active material layer may include an antimony-based graded porous carbon fiber negative electrode material, a binder, a conductive agent, and the like, wherein the types of the binder and the conductive agent are not particularly limited, and may be selected by those skilled in the art according to actual needs, and in addition, when the antimony-based graded porous carbon fiber negative electrode material is used in the negative electrode sheet, it may be subjected to a destruction or grinding process in advance and then mixed with the binder and the conductive agent.

In yet another aspect, the present invention is directed to a potassium ion battery. According to the embodiment of the invention, the potassium ion battery comprises the negative electrode plate, and/or the antimony-based graded porous carbon fiber negative electrode material prepared by the method for preparing the antimony-based graded porous carbon fiber negative electrode material. The battery has all the technical characteristics and effects of the negative electrode plate, the antimony-based graded porous carbon fiber negative electrode material and the method for preparing the antimony-based graded porous carbon fiber negative electrode material, and details are not repeated here. In general, the battery has high specific capacity, and has good cycle performance and rate capability.

The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are conventional products which are commercially available, and are not indicated by manufacturers.

Example 1

(1) Adding 0.4g of antimony chloride into 18ml of N, N-dimethylformamide, stirring for 20 minutes, adding 1g of polyacrylonitrile and 0.8g of polyvinylpyrrolidone, and stirring and mixing for 12 hours to obtain a precursor solution;

(2) Carrying out electrostatic spinning treatment on the precursor solution: sucking 10mL of precursor solution by using an injector, placing the precursor solution on a sliding table, placing a roller at a speed of 100 rpm at a position 11cm away from a needle, applying a voltage of 20kV to the needle, wherein the propelling speed of the injector is 1mL/h, the humidity in an electrostatic spinning machine is 25%, and the temperature is 40 ℃ to obtain a precursor;

(3) And (3) placing the precursor in a crucible, heating to 500 ℃ in a muffle furnace in the air atmosphere at the temperature rate of 5 ℃/min, preserving the heat for 2h, and cooling to room temperature to obtain the antimony-based hierarchical porous carbon fiber cathode material.

Example 2

The difference from example 1 is that polyvinylpyrrolidone in step (1) was added in an amount of 0.6g.

Example 3

The difference from example 1 is that polyvinylpyrrolidone in step (1) was added in an amount of 1g

Comparative example 1

The difference from example 1 is that step (1) is: adding 1g of polyacrylonitrile into 18ml of N, N-dimethylformamide, and stirring and mixing for 12 hours to obtain a precursor solution.

Comparative example 2

The difference from example 1 is that in step (3), the annealing treatment is performed in a nitrogen atmosphere.

Comparative example 3

The difference from example 1 is that step (1) is: 1g of polyacrylonitrile and 0.8g of polyvinylpyrrolidone are added into 18ml of N, N-dimethylformamide, and stirred and mixed for 12 hours to obtain a precursor solution.

Comparative example 4

The difference from comparative example 3 is that, in step (3), the annealing treatment was performed under a nitrogen atmosphere.

Characterization and testing:

appearance and appearance: characterizing by a scanning electron microscope;

the material components are as follows: analysis by X-ray diffraction;

pore size distribution: the characterization is carried out by a BET specific surface area test method;

cycle performance: and (2) grinding the carbon fiber negative electrode material prepared in the embodiment or the comparative example, dispersing the ground carbon fiber negative electrode material, the binder carboxymethyl cellulose sodium and the conductive agent acetylene black in deionized water according to a mass ratio of 80. The metal potassium is used as a reference electrode and a counter electrode, the glass fiber is used as a diaphragm, and the CR2032 button cell is assembled in a glove box with the water and oxygen contents less than 0.5 ppm. The adopted 5M potassium bis (fluorosulfonyl) imide is dissolved in the electrolyte of diethylene glycol dimethyl ether. The CR2032 button cell is charged and discharged with constant current (0-3V) by a Xinwei cell tester BTS 7.0-5V 10mA, and the cycle performance of the CR2032 button cell is tested at the current density of 100 mA/g;

rate capability: the CR2032 button cell was tested for specific capacity at different current densities and cycles (50 mA/g,100mA/g,200mA/g,500mA/g,1000 mA/g).

Results and discussion:

the results of observing the antimony-based graded-pore carbon fiber negative electrode materials prepared in the above examples 1 to 3 by a scanning electron microscope are sequentially shown as (a), (b) and (c) in fig. 3, which shows that the antimony-based graded-pore carbon fiber negative electrode materials prepared by the method of the above examples of the present invention are porous nanofibers; also, as can be seen from fig. 3, as the mass ratio of PAN and PVP becomes larger, the fiber diameter and porosity of the obtained anode material also become larger.

The antimony-based hierarchical porous carbon fiber anode materials prepared in the above examples 1 to 3 and comparative examples 1 to 4 are characterized by a BET specific surface area test method, the obtained adsorption-desorption isotherms and pore size distribution diagrams are respectively shown in fig. 4 to 10, and the specific surface areas of the anode materials obtained in the corresponding examples or comparative examples are also distributed and labeled in fig. 4 to 10, wherein the adsorption-desorption isotherms and pore size distribution diagrams corresponding to the examples 1 to 3 are sequentially shown in fig. 4 to 6, and as can be seen from analysis, the antimony-based hierarchical porous carbon fiber anode materials prepared in the examples 1 to 3 by using the method of the present invention can be obtained by comprehensively controlling the parameters within the above ranges, such that the obtained antimony-based hierarchical porous carbon fiber anode materials have a mesoporous structure with relatively uniform and concentrated pore size distribution. In the comparative example 1, only PAN is annealed in air, and the corresponding adsorption-desorption isotherm curve is shown in fig. 7, in which the desorption curve and the adsorption curve are almost overlapped, the specific surface area is large, the pore diameter of the porous structure is small, the distribution range is narrow, and the porous structure is mainly a microporous structure and only a small amount of mesopores are formed; the difference between comparative example 2 (corresponding to fig. 8) and example 1 (corresponding to fig. 4) is only that the annealing treatment is performed in a nitrogen atmosphere compared with comparative example 2, and it can be seen from comparing fig. 8 and fig. 4 and combining the specific surface areas of the two, the porous structure formed by the negative electrode material in comparative example 2 is mainly composed of micropores, and the mesoporous pore size distribution is less; similarly, in comparative example 4 (corresponding to fig. 10) and comparative example 1 (corresponding to fig. 7), the desorption curve and the adsorption curve overlap with each other to a higher degree, the mesostructure content is lower, and the specific surface area measured under the same conditions is larger, and in comparative example 3 (corresponding to fig. 9) and comparative example 4 (corresponding to fig. 10), the same precursor is annealed in the air atmosphere, so that hysteresis is generated, and the specific surface area is smaller, indicating that the mesostructure is formed. Therefore, the annealing treatment of PAN and PVP in the nitrogen atmosphere tends to form a microporous structure, and the annealing treatment of PAN and PVP in the air atmosphere is more favorable for forming a mesoporous structure. Further, in combination with examples 1 to 3 and fig. 4 to 6, it can be further explained that when the mass ratio of PAN to PVP is 5: (3-5), the specific surface area of the prepared negative electrode material is increased and then reduced, and the mass ratio of PAN to PVP is controlled to be 5: (3-5) is more favorable for obtaining larger specific surface area.

An X-ray diffraction test is performed on the antimony-based hierarchical porous carbon fiber negative electrode material prepared in the above example 1, and a test result is shown in fig. 11, in which two obvious strong peaks are present at 27.7 ° and 31.1 °, which are characteristic peaks of a typical antimony trioxide material, which indicates that antimony trioxide is formed in the obtained negative electrode material, and the improvement of the specific capacity of a battery is facilitated.

The antimony-based graded-pore carbon fiber negative electrode materials prepared in the above examples 1 to 3 were subjected to cycle performance tests, and the test results are shown in fig. 12. The first-time charging reversible specific capacity of the antimony-based hierarchical porous carbon fiber material can reach more than 400mAh/g, the capacity can still be kept more than 300mAh/g after 50 cycles, the capacity retention rate can reach more than 75%, and the antimony-based hierarchical porous carbon fiber material shows good cycle performance. Further, the first charge reversible specific capacity of the antimony-based hierarchical porous carbon fiber negative electrode material in example 1 is up to 569.8mAh/g, the capacity can still be maintained at 437.3mAh/g after 50 cycles, the capacity retention rate is 76.7%, and the cycle performance is better.

The rate capability test of the antimony-based hierarchical porous carbon fiber negative electrode material prepared in example 1 is performed, and the test result is shown in fig. 13, so that it can be seen that the specific capacity of the battery can reach 197mAh/g when the current density is 1A/g, and can reach 433mAh/g when the current density is returned to 0.1A/g, and excellent rate capability is shown.

In summary, the antimony-based hierarchical pore carbon fiber anode material prepared by the embodiment of the invention has a mesoporous structure with uniform distribution, contains antimony trioxide, is beneficial to improving the specific capacity of a battery, and has good cycle performance and rate capability.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. A method for preparing an antimony-based graded-pore carbon fiber negative electrode material is characterized by comprising the following steps of:

(1) Mixing antimony salt, polyacrylonitrile, polyvinylpyrrolidone and a solvent to obtain a precursor solution;

(2) Carrying out electrostatic spinning treatment on the precursor solution to obtain a precursor;

(3) And annealing the precursor to obtain the antimony-based graded-pore carbon fiber negative electrode material.

2. The method according to claim 1, wherein in the step (1), the mass ratio of the polyacrylonitrile to the polyvinylpyrrolidone is 0.5-1.8, preferably 5: (3-5) of the total weight of the composition,

optionally, the antimony salt comprises antimony chloride and the solvent is N, N-dimethylformamide.

3. The method according to claim 1 or 2, wherein in the step (1), the mass ratio of the antimony salt is 10-40% based on the total mass of the antimony salt, the polyacrylonitrile and the polyvinylpyrrolidone.

4. The method according to claim 1, wherein in the step (2), the electrospinning process satisfies at least one of the following conditions: the spinning voltage is 15-25 kV, the advancing speed of the injector is 0.6-1.2 ml/h, the distance between the needle head and the roller is 10-20 cm, the rotating speed of the roller is 50-200 r/min, the humidity is 20-50%, and the temperature is 30-40 ℃.

5. The method according to claim 1, wherein in the step (3), the annealing treatment is performed under an air atmosphere.

6. The method according to claim 1 or 5, characterized in that the annealing treatment is carried out at a temperature of 423 to 600 ℃ for a time of 1 to 4 hours.

7. The method of claim 1, wherein the antimony-based graded pore carbon fiber anode material has an average pore size of 2 to 10nm.

8. An antimony-based graded-pore carbon fiber negative electrode material prepared by the method of any one of claims 1 to 7.

9. A negative electrode sheet, characterized by comprising the antimony-based graded porous carbon fiber negative electrode material of claim 8 or the antimony-based graded porous carbon fiber negative electrode material prepared by the method of any one of claims 1 to 7.

10. A potassium ion battery, comprising the negative electrode sheet of claim 9, and/or the antimony-based graded porous carbon fiber negative electrode material of claim 8, and/or the antimony-based graded porous carbon fiber negative electrode material prepared by the method of any one of claims 1 to 7.

Images