Polyaniline and carbon powder composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to a polyaniline and carbon powder composite material and a preparation method and application thereof. The composite material comprises a current collector, polyaniline and carbon powder, wherein the polyaniline and the carbon powder are loaded on the current collector; the polyaniline and the carbon powder are uniformly distributed. Preferably, the carbon powder is functionalized carbon powder, and the carbon powder is selected from one or more of a carbon nanotube, activated carbon or graphene; the functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder; the polyaniline and the functionalized carbon powder form a three-dimensional network structure, and a hydrogen bond is formed between the polyaniline and the functionalized carbon powder. A hydrogen bond formed between polyaniline and functionalized carbon powder can effectively inhibit dissolution of the positive electrode material in a zinc salt electrolyte containing iodide ions, and the stability of the positive electrode material structure is enhanced. Meanwhile, the reduction unit of bipolar polyaniline can effectively catalyze the oxidation-reduction reaction of I- / I0 and anchor the polyiodide ions, so that the shuttle side reaction of the polyiodide ions is inhibited, the growth of zinc dendrites is reduced, and the specific capacity and the cycling stability of the organic matter composite positive electrode are further remarkably improved. Besides, carboxyl and / or hydroxyl functional groups contained in the functionalized carbon powder provide certain protons for polyaniline, and energy storage is carried out through intercalation and deintercalation of the protons, so that PANI redox reaction kinetics is accelerated, and the electrolytic type aqueous zinc-iodine battery with high energy density and long service life is constructed.

Description

Technical Field

[0001] The present application relates to the field of electrochemical energy storage technology, and in particular to a polyaniline and carbon powder composite material and a preparation method and use thereof. Background Art

[0002] As global warming continues to intensify, the demand for efficient and sustainable energy storage systems is growing rapidly. Aqueous zinc-ion batteries are considered to be a very promising option due to their abundant zinc resources, extremely low cost and excellent environmental friendliness. Aqueous zinc-iodine batteries stand out as an emerging and promising energy storage technology, mainly because of their great potential in achieving high energy density.

[0003] However, current aqueous zinc-iodine batteries still face many challenges. During the charge and discharge process, the redox reaction kinetics of iodine species are sluggish, resulting in low coulombic efficiency of the battery, limiting the battery's rate performance; and the polyiodides produced will shuttle between the positive and negative electrodes, on the one hand causing the loss of active iodine, and on the other hand causing side reactions on the surface of the zinc negative electrode, corroding the zinc negative electrode, causing the battery's capacity and cycle life to decay rapidly, while also reducing the battery's coulombic efficiency and energy efficiency, hindering its widespread application.

[0004] Compared with a large amount of carbon materials adsorbing or electrodepositing iodine as a positive electrode material, it is of great significance to use efficient catalysts to promote the reversible transformation of iodine ions / iodine in the electrolyte to construct an electrolytic zinc-iodine battery with high specific capacity and stability. In particular, conductive polymers have become one of the most promising catalytic positive electrode materials due to their low cost, diverse structures and green environmental protection. Therefore, this application is proposed in view of the problems faced by zinc-iodine batteries, such as slow redox kinetics, severe self-discharge, limited cycle life and low coulombic efficiency. Summary of the invention

[0005] In a first aspect, the present application provides a composite material of polyaniline and carbon powder, the composite material comprising: a current collector, polyaniline and carbon powder loaded on the current collector;

[0006] Preferably, the carbon powder is functionalized carbon powder, and the carbon powder is selected from one or more of carbon nanotubes, activated carbon or graphene.

[0007] Preferably, the functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder;

[0008] The polyaniline and the functionalized carbon powder form a three-dimensional network structure, and hydrogen bonds are formed between the polyaniline and the functionalized carbon powder.

[0009] The three-dimensional network structure formed by polyaniline and functionalized carbon powder is similar to a "sea urchin".

[0010] Preferably, the mass ratio of the polyaniline to the carbon powder is (5 - 7):(4 - 2).

[0011] Preferably, the composite material further contains a binder, and the mass ratio of the polyaniline, the carbon powder, and the binder is (4 - 7):(5 - 2):1.

[0012] The second aspect of the present application provides a preparation method of the polyaniline and carbon powder composite material described in the first aspect. The preparation method includes the following steps:

[0013] Mix the polyaniline, the carbon powder, and the binder, then grind them, and then add an organic solvent and mix well to obtain a slurry;

[0014] Coat the obtained slurry on a current collector, and after drying treatment, the composite material can be obtained.

[0015] The mass ratio of the polyaniline, the carbon powder, and the binder is (4 - 7):(5 - 2):1.

[0016] Preferably, the slurry is ground again and then coated or roll-pressed onto the current collector.

[0017] Preferably, the loading amount of the positive electrode material on the current collector is 1.5 - 30.0 mg cm -2 . Preferably, 1.5 - 5 mg cm -2 .

[0018] Preferably, the current collector is selected from one or more of carbon cloth, graphite paper, stainless steel mesh, stainless steel foil, titanium mesh, and titanium foil.

[0019] The drying conditions are drying at 100 - 40 °C for 8 - 40 hours. For example, drying at 60 °C for 24 hours.

[0020] Preferably, the binder is selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC).

[0021] Preferably, the organic solvent is selected from one or more of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and acetonitrile (ACN).

[0022] The third aspect of the present application provides the use of the polyaniline and carbon powder composite material described in any item of the first aspect as a positive electrode material for an aqueous zinc-iodine battery.

[0023] The fourth aspect of the present application provides an aqueous zinc-iodine battery, and the battery includes the composite material described in the first aspect.

[0024] Preferably, when assembling the battery, a suitable electrolyte is added according to the size of the battery, and the amount of the added electrolyte is 50 - 300 μL / g.

[0025] Preferably, the negative electrode sheet of the battery is a metal zinc foil, the thickness of the metal zinc foil is 30-100 μm, and is sealed and assembled into a CR2032 battery at a pressure of 50-70 MPa for electrochemical performance testing.

[0026] The electrolyte of the battery is an aqueous solution comprising a zinc salt and an iodine source.

[0027] Preferably, the zinc salt is zinc sulfate heptahydrate, zinc trifluoromethanesulfonate, or zinc chloride.

[0028] Preferably, the iodine salt is one or more of ammonium iodide, zinc iodide, potassium iodide, sodium iodide, manganese iodide, bromine iodide and some iodine ion complexes.

[0029] Preferably, the molar concentration of the zinc salt is 0.5-5M, and the molar concentration of the iodine salt is 0.05-2M.

[0030] This application has the following beneficial effects:

[0031] 1. The present application provides a positive electrode material for an aqueous zinc-iodine battery. The present application obtains the positive electrode material by compounding polyaniline and carbon powder, and forms an organic / inorganic reaction interface on the surface of polyaniline, and the material exhibits excellent electrochemical properties. Preferably, the carbon powder can be functionalized carbon powder, such as functionalized carbon nanotubes. The hydrogen bonds formed between polyaniline and functionalized carbon nanotubes can effectively inhibit the dissolution of the positive electrode material, thereby significantly improving the cycle stability of the composite positive electrode, and a three-dimensional network structure is formed between the two, which enhances the conductivity of the positive electrode material and improves the energy density and overall performance of the battery. Polar polyaniline has oxidation and reduction units, in which the carboxyl functional groups of functionalized carbon nanotubes provide certain protons for polyaniline, and energy is stored through the insertion and extraction of protons to accelerate the kinetics of PANI redox reactions and improve the specific capacity. At the same time, the reduction unit of polyaniline can effectively anchor polyiodide ions to inhibit the shuttling of polyiodide ions, catalyze the conversion of iodine, and reduce the growth of zinc dendrites, thereby constructing an aqueous zinc-iodine battery with high energy density and long life.

[0032] 2. The material of the present application can improve the specific capacity and cycle stability of the positive electrode of aqueous zinc-iodine batteries. Specifically, it is manifested as follows: Figure 8 It can be seen that at a current density of 3Ag -1 Under the conditions of , after nearly 5000 charge and discharge cycles, the capacity retention rate of the positive electrode material of Example 1 (C-PANI in the figure) is 95%; its specific capacity is still as high as nearly 400mAh g -1 , showing high specific capacity and excellent cycle stability. Figure 9 , 10It can be seen that the cathode materials of Example 1 have average discharge capacities of 423, 390, 366, 350, 323, 308, and 277 mAh g at 1.0, 2.0, 3.0, 5.0, 7.0, 10.0, and 20.0 Ag -1 respectively. Overall, it shows high-capacity output and maintains relatively stable performance when the current density changes. Compared with the unmodified similar material (PANI), its rate performance advantage is very obvious. From -1 it can be known that at a large current density of 20.0 Ag Figure 13 the cathode material of Example 1 still exhibits amazing long-cycle stability. After undergoing up to 40,000 charge-discharge cycles, its capacity retention rate can still be as high as 85.7%, the battery can still maintain excellent stability, and its specific capacity can also be maintained at a good level. This shows that the cathode material can effectively anchor polyiodide ions, inhibit their shuttling, thereby reducing the corrosion of the zinc anode, reflecting its excellent performance under long cycle life. -1 Description of the Drawings

[0033] Figure 1 is the scanning electron microscope image of polyaniline (PANI) provided in Example 1 of this application;

[0034] Figure 2 is the scanning electron microscope image of the cathode material (C-PANI) provided in Example 1 of this application;

[0035] Figure 3 is the transmission electron microscope image of the cathode material (C-PANI) provided in Example 1 of this application;

[0036] Figure 4 is the XPS spectrum of N1s of polyaniline (PANI) and the cathode material (C-PANI) provided in Example 1 of this application;

[0037] Figure 5 is the Raman spectrum of the cathode material (C-PANI), polyaniline (PANI), and functionalized carbon nanotubes (CNTs) provided in Example 1 of this application;

[0038] Figure 6 is the element distribution map of the cathode material (C-PANI) provided in Example 1 of this application;

[0039] Figure 7 is the XRD pattern of the cathode material (C-PANI) and polyaniline (PANI) provided in Example 1 of this application;

[0040] Figure 8 is the cathode material provided in Example 1 of this application as the cathode of an aqueous zinc-iodine battery, at a current density of 3000 amperes per gram (abbreviated as @3Ag​-1 ) Charge-discharge long cycle diagram (the curve corresponding to the left arrow is the specific capacity at different cycle numbers, and the curve corresponding to the right arrow is the Coulombic efficiency at different cycle numbers);

[0041] Figure 9 Electrochemical rate performance diagrams of the cathode materials provided in Example 1 and Comparative Example 1 of the present application as the cathodes of aqueous zinc-iodine batteries, with current densities of 1.0, 2.0, 3.0, 5.0, 7.0, 10.0, and 20.0 Ag -1 ;

[0042] Figure 10 Charge-discharge curve diagram of the cathode material provided in Example 1 of the present application as the cathode of an aqueous zinc-iodine battery, with the current densities used in constant current charge-discharge being 1.0, 2.0, 3.0, 5.0, 7.0, 10.0, and 20.0 A-1g -1 ;

[0043] Figure 11 Charge-discharge long cycle comparison diagram of the cathode material provided in Example 1 of the present application as the cathode of an aqueous zinc-iodine battery at a current density of 1000 milliamperes per gram (abbreviated as @1Ag -1 );

[0044] Figure 12 Charge-discharge long cycle comparison diagrams of the cathode materials provided in Example 1 and Comparative Example 1 of the present application as the cathodes of aqueous zinc-iodine batteries at a current density of 5000 milliamperes per gram (abbreviated as @5.0Ag -1 );

[0045] Figure 13 Charge-discharge long cycle comparison diagram of the cathode material of Example 1 of the present application as the cathode of an aqueous zinc-iodine battery at a current density of 20 amperes per gram (abbreviated as @20.0Ag -1 )(The two curves near the left arrow are the specific capacities of the C-PANI cathode at different cycle numbers, and the right arrow is the Coulombic efficiency of the C-PANI cathode at different cycle numbers).

[0046] Figure 14 Charge-discharge long cycle comparison diagrams of the cathode materials provided in Comparative Example 1 and Comparative Example 2 as the cathodes of zinc-ion batteries at a current density of 20 amperes per gram (abbreviated as @20.0Ag -1 )(The two curves near the left arrow are the specific capacities of the CNTs and PANI cathodes at different cycle numbers, and the right arrow is the Coulombic efficiency of the CNTs and PANI cathodes at different cycle numbers).

[0047] Figure 15 Charge-discharge long cycle diagrams of the cathode material of Example 6 as the cathode of a zinc-ion battery at a current density of 0.5 amperes per gram (abbreviated as @0.5Ag -1Charge-discharge long cycle comparison diagram

[0048] Figure 16 The cathode materials of Example 7 were used as the cathodes of zinc-ion batteries at a current density of 0.5 A g -1 Charge-discharge long cycle comparison diagram

[0049] Figure 17 The cathode materials of Example 8 were used as the cathodes of aqueous zinc-iodine batteries at a current density of 0.5 A g -1 Charge-discharge long cycle comparison diagram Detailed implementation manners

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0051] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchase or can be prepared by existing methods. The experimental methods without specific conditions noted in the following embodiments are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0052] Various raw materials such as polyaniline, carboxylated carbon nanotubes, and hydroxylated carbon nanotubes used in the examples and comparative examples were obtained through purchase.

[0053] Example 1

[0054] A preparation method of a cathode material, the method comprising:

[0055] S1. Physically grind polyaniline, carboxylated carbon nanotubes, and polyvinylidene fluoride (PVDF) in a mass ratio of 6:3:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0056] S2. Uniformly coat the obtained slurry on carbon cloth, with a loading amount of 2.0 mg cm -2 , and dry at 60 °C for 24 hours to obtain the modified cathode material.

[0057] The aqueous zinc-iodine battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous mixed solution of zinc trifluoromethanesulfonate and ammonium iodide, where the concentration of zinc trifluoromethanesulfonate is 2 mol / L and the concentration of ammonium iodide is 0.3 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure of positive electrode, separator, and negative electrode in sequence.

[0058] Example 2

[0059] A preparation method of a positive electrode material, the method comprising:

[0060] S1. Physically grind polyaniline, hydroxylated carbon nanotubes, and polytetrafluoroethylene (PTFE) in a mass ratio of 5:4:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0061] S2. Uniformly coat the obtained slurry on a titanium foil with a loading amount of 1.5 mg cm -2 , and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0062] The aqueous zinc-iodine battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous mixed solution of zinc trifluoromethanesulfonate and zinc iodide, where the concentration of zinc trifluoromethanesulfonate is 2 mol / L and the concentration of ammonium iodide is 0.2 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure of positive electrode, separator, and negative electrode in sequence.

[0063] Example 3

[0064] A preparation method of a positive electrode material, the method comprising:

[0065] S1. Physically grind polyaniline, carboxylated carbon nanotubes, and polytetrafluoroethylene (PTFE) in a mass ratio of 4:5:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0066] S2. Uniformly coat the obtained slurry on a carbon cloth with a loading amount of 1.5 mg cm -2 , and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0067] The aqueous zinc-iodine battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.05 mm. The electrolyte is an aqueous solution mixed with zinc trifluoromethanesulfonate and potassium iodide. The concentration of zinc trifluoromethanesulfonate is 2 mol / L, and the concentration of potassium iodide is 0.4 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, the separator, and the negative electrode in sequence.

[0068] Example 4

[0069] A preparation method of a positive electrode material, the method comprising:

[0070] S1. Physically grind polyaniline, hydroxylated carbon nanotubes, and carboxymethyl cellulose (CMC) in a mass ratio of 7:2:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0071] S2. Uniformly coat the obtained slurry on a stainless steel mesh with a loading amount of 2 mg cm -2 , and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0072] The aqueous zinc-iodine battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution mixed with zinc sulfate and zinc iodide. The concentration of zinc sulfate is 2 mol / L, and the concentration of zinc iodide is 0.2 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, the separator, and the negative electrode in sequence.

[0073] Example 5

[0074] A preparation method of a positive electrode material, the method comprising:

[0075] S1. Physically grind polyaniline, carboxylated carbon nanotubes, and polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0076] S2. Uniformly coat the obtained slurry on a stainless steel mesh with a loading amount of 2 mg cm -2 , and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0077] The aqueous zinc-iodine battery of this embodiment is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.05 mm. The electrolyte is an aqueous solution of zinc trifluoromethanesulfonate and sodium iodide. The concentration of zinc trifluoromethanesulfonate is 2 mol / L, and the concentration of sodium iodide is 0.5 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, the separator, and the negative electrode in sequence.

[0078] Comparative Example 1 - The same as Example 1 except that no functionalized carbon nanotubes are added

[0079] A preparation method of a comparative positive electrode material, the method comprising:

[0080] S1. Physically grind polyaniline and polyvinylidene fluoride (PVDF) in a mass ratio of 9:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0081] S2. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 2 mg cm -2 , and dry it at 60 °C for 24 hours to obtain a modified positive electrode material, denoted as PANI.

[0082] The aqueous zinc-iodine battery of this embodiment is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc trifluoromethanesulfonate and ammonium iodide. Among them, the concentration of zinc trifluoromethanesulfonate is 2 mol / L, and the concentration of ammonium iodide is 0.3 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, the separator, and the negative electrode in sequence.

[0083] Comparative Example 2 - The same as Example 1 except that no polyaniline is added

[0084] A preparation method of a comparative positive electrode material, the method comprising:

[0085] S1. Physically grind carboxylated carbon nanotubes and polyvinylidene fluoride (PVDF) in a mass ratio of 9:1, and then uniformly mix them into an N-methylpyrrolidone solution;

[0086] S2. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 2 mg cm -2 , and dry it at 60 °C for 24 hours to obtain a modified positive electrode material, denoted as CNTS.

[0087] The aqueous zinc-iodine battery of this embodiment is composed of a positive electrode, a negative electrode, a diaphragm and an electrolyte. The negative electrode adopts a commercial high-purity zinc sheet with a thickness of 0.1 mm, and the electrolyte is a mixed aqueous solution of zinc trifluoromethanesulfonate and ammonium iodide, wherein the concentration of zinc trifluoromethanesulfonate is 2 mol / L and the concentration of ammonium iodide is 0.3 mol / L. The diaphragm uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber diaphragm and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the diaphragm is located between the positive electrode and the negative electrode, presenting a sandwich-like stacking structure, which is the positive electrode, the diaphragm and the negative electrode in sequence.

[0088] Material characterization and performance testing:

[0089] Scanning electron microscope tests were performed on the positive electrode materials provided in Examples 1 to 5 and Comparative Examples 1 and 2. Since the results are similar, only the test results of Example 1 are used as an example below.

[0090] Figure 1 a and b are scanning electron microscope images of the polyaniline provided in Example 1. The images show the particle morphology of the polyaniline, which has an irregular shape, obvious texture and roughness on the surface, and a relatively loose overall structure.

[0091] Figure 2 This is a scanning electron microscope image of the positive electrode material of the aqueous zinc-iodine battery provided in Example 1. The image shows a complex fibrous morphology, indicating that the polyaniline particles and the carboxylated carbon nanotubes are intertwined to form a three-dimensional network structure. This structure helps to improve its conductivity and increase active sites.

[0092] Figure 3 This is a transmission electron micrograph of the positive electrode material provided in Example 1. This image shows the interface of polyaniline and carbon nanotubes in more detail. In this image, the filamentous structure of the carbon nanotubes can be observed, forming the core of the polyaniline, showing clearer details. The polyaniline is wrapped around the carbon nanotubes at the nanoscale, further enhancing the performance of the composite material.

[0093] Figure 4 The XPS spectra of N1s of polyaniline and aqueous zinc-iodine battery positive electrode materials provided in Example 1 of the present application. From the in-depth analysis of the figure, it can be seen that the overall shape of the N 1s peak is relatively broad, indicating different chemical environments of nitrogen. The main characteristic peaks of polyaniline include -N=, representing the presence of reduced nitrogen, with a peak value at about 398.5eV. After adding functionalized carbon nanotubes, the main characteristic peaks of the positive electrode material include -NH +, this peak represents the nitrogen in the oxidized state of polyaniline, usually located at about 399.5 eV. Through the chemical state change of nitrogen element in this spectrum, it shows that polyaniline stores energy through the insertion and extraction of protons. At the same time, polyaniline can anchor polyiodide ions, thereby inhibiting their shuttle and reducing the corrosion of the zinc negative electrode.

[0094] Figure 5 Raman spectra of the aqueous zinc-iodine battery cathode materials (C-PANI), polyaniline (PANI), and carboxylated carbon nanotubes (CNTs) provided in Example 1 of this application. It can be seen from the Raman spectra that the peak at 1336 cm -1 is attributed to C-N + stretching, and the blue shift of the peak position of the C-N + band indicates the existence of hydrogen bond interaction between polyaniline (PANI) and carboxylated carbon nanotubes (CNTs), enhancing the structural stability of the cathode material.

[0095] Figure 6 Element distribution maps of the cathode materials provided in Example 1. It can be seen from the figure that the microstructure of the composite material of polyaniline and carbon nanotubes is shown. In the figure, the fibrous structure of carbon nanotubes and the particles of polyaniline form an interlaced network. Overall, the combination of the transmission electron microscopy image on the left and the element mapping image on the right provides detailed information on the microstructure and element distribution of the polyaniline and carbon nanotube composite material, helping to study its properties and performance.

[0096] Figure 7 XRD patterns of the cathode materials and polyaniline provided in Example 1 of this application. This figure shows the structural similarity between C-PANI and PANI. By comparing their XRD patterns, their crystallization characteristics and relative stability can be inferred to represent the successful composite of the cathode material.

[0097] Using the cathode materials provided in Example 1 and Comparative Examples 1 and 2 with the same concentration of zinc salt and iodine salt, an aqueous zinc-iodine battery was constructed. Specifically, the cathode materials provided in Example 1 and Comparative Examples 1 and 2 were used as the cathode, zinc foil as the anode, and the electrolyte was 2M Zn(OTF)2 and 0.3M NH4I. Charge-discharge tests and long charge-discharge cycle tests were carried out on the battery, and the results are as Figures 8 to 13 shown.

[0098] Long charge-discharge cycle tests were carried out on the cathode materials provided in Examples 1 to 5. Since the results are similar, only the test results of Example 1 are used for illustration below. Figure 8 is the long charge-discharge cycle condition of the cathode materials provided in Example 1 and Comparative Example 1 as the zinc-ion battery cathode at a current density of 3A g -1 . It can be seen from Figure 8 that at a current density of 3A g -1Under the condition of nearly 5,000 charge-discharge cycles, the capacity retention rate of the cathode material of Example 1 (legend: C-PANI) is almost perfectly maintained at 95%, and its specific capacity is as high as 400 mAh g -1 , showing extremely excellent cycle stability.

[0099] The charge-discharge test was carried out on the cathode material provided in Example 1. Since the results are similar, only the test results of Example 1 are taken as an example for illustration below. Figure 9 、 10 The rate performance and the corresponding charge-discharge curves of the cathode material provided in Example 1 at different current densities are shown. The current densities used for constant current charge-discharge are 1.0, 2.0, 3.0, 5.0, 7.0, 10.0, 20.0 A g -1 . The average discharge capacities of the cathode material of Example 1 (legend: C-PANI) at 1.0, 2.0, 3.0, 5.0, 7.0, 10.0, 20.0 A g -1 are 423, 390, 366, 350, 323, 308 and 277 mAh g -1 respectively. Overall, it shows an excellent trend of high-capacity output and relatively stable change with the current density. Compared with the cathode material of Comparative Example 1 of unmodified similar materials (legend: PANI), its rate performance advantage is significant. This shows that carboxylated carbon nanotubes provide certain protons for polyaniline to promote energy storage, and enhance the conductivity of the material, improving the overall performance of the battery.

[0100] Figure 11 This is the long-term charge-discharge comparison chart of the cathode materials provided in Example 1 and Comparative Example 1 of the present application as the cathode of an aqueous zinc-iodine battery at a current density of 1000 milliamperes per gram (abbreviated as @1 A g -1 ). Figure 12 This is the long-term charge-discharge comparison chart of the cathode materials provided in Example 1 and Comparative Example 1 of the present application as the cathode of an aqueous zinc-iodine battery at a current density of 5000 milliamperes per gram (abbreviated as @5.0 A g -1 ).

[0101] Figure 11 It shows that under the condition of a current density of 1 A g -1 , the specific capacity of the cathode material of Example 1 reaches 380 mAh g -1 , and the capacity retention rate is 95%.

[0102] Figure 12 It shows that under the condition of a current density of 5 A g -1 , the specific capacity of the cathode material of Example 1 reaches 310 mAh g -1 , and the capacity retention rate is 90.3%.

[0103] In contrast, the performance of the positive electrode material in Comparative Example 1 (PANI in the legend) is much inferior. Figure 12 Among them, the capacity retention rate during the same period can only reach 42.8%. Figure 12 Among them, the corresponding specific capacity is only 120 mAh g -1 .

[0104] Figure 13 This is the charge-discharge long-cycle comparison chart of the positive electrode material of Example 1 of this application as the positive electrode of an aqueous zinc-iodine battery at a current density of 20 amperes per gram (abbreviated as @20.0 Ag -1 ). (The two curves near the left arrow are the specific capacities of the C-PANI positive electrode at different numbers of cycles, and the right arrow is the Coulombic efficiency of the C-PANI positive electrode at different numbers of cycles). Figure 13 It can be seen that under the condition of a current density of 20 Ag -1 , the specific capacity of the positive electrode material of Example 1 reaches 265 mAh g -1 , and after undergoing up to 40,000 charge-discharge cycles, its capacity retention rate can still be as high as 85.7%.

[0105] Figure 14 This is the charge-discharge long-cycle comparison chart of the positive electrode materials provided in Comparative Example 1 and Comparative Example 2 as the positive electrodes of zinc-ion batteries at a current density of 20 amperes per gram (abbreviated as @20.0 Ag -1 ). (The two curves near the left arrow are the specific capacities of the CNTs and PANI positive electrodes at different numbers of cycles, and the right arrow is the Coulombic efficiency of the CNTs and PANI positive electrodes at different numbers of cycles).

[0106] Figures 13 - 14 It can be known that if the optimal sample in the positive electrode material is replaced with pure polyaniline or pure carboxylated carbon nanotubes, the results in terms of capacity and stability are both poor. Specifically, at a high current density of 20 Ag -1 , the specific capacity of PANI as the positive electrode is less than 50 mAh g -1 , the specific capacity of CNTs as the positive electrode is nearly 100 mAh g -1 , but its lifespan is only 2000 cycles. This fully shows that the combination of polyaniline and carboxylated carbon nanotubes is crucial. At a high current density of 20 Ag -1 , the positive electrode material of Example 1 still shows amazing long-cycle stability. After undergoing up to 40,000 charge-discharge cycles, its capacity retention rate can still be as high as 85.7%. The battery can still maintain excellent stability, and its specific capacity can also be maintained at a good level, which fully reflects the excellent performance of this positive electrode material under high-current conditions.

[0107] Selection of the carbon powder for the positive electrode material in Example 6

[0108] Polyaniline (PANI), different types of carbon powders (graphene, activated carbon YP80, carboxylated carbon nanotubes) and a binder were mixed in a mass ratio of 6:3:1, and the resulting material was prepared as the positive electrode of the battery in the manner of Example 1. The electrolyte was 2M trifluoromethanesulfonic acid. Figure 15 The positive electrode materials were respectively used as the positive electrodes of zinc-ion batteries at a current density of 0.5 A / g (abbreviated as @0.5Ag -1 ) for the charge-discharge long cycle comparison chart. Figure 15 It can be seen that the specific capacities of the positive electrode materials obtained by uniformly compounding polyaniline with graphene, activated carbon YP80, and carboxylated carbon nanotubes are 115 mAh g-1, 150 mAh g-1, and 210 mAh g-1 respectively. This shows that all three carbon materials have relatively high specific capacities, and carboxylated carbon nanotubes are preferentially selected as the carbon powder in the positive electrode material.

[0109] Selection of the positive electrode material ratio in Example 7

[0110] Polyaniline (PANI), carboxylated carbon nanotubes and a binder were mixed in mass ratios of 7:2:1, 6:3:1, and 4:5:1 respectively, and the resulting materials were prepared as the positive electrodes of the battery in the manner of Example 1. Figure 16 The positive electrode materials were respectively used as the positive electrodes of zinc-ion batteries at a current density of 0.5 A / g (abbreviated as @0.5Ag -1 ) for the charge-discharge long cycle comparison chart. Figure 16 It can be seen that the specific capacities of the positive electrode materials with the three ratios are from low to high as 210 mAh g -1 (4:5:1), 320 mAh g -1 (7:2:1), 380 mAh g -1 (6:3:1). This shows that all three ratios have relatively high specific capacities, and polyaniline (PANI), functionalized carbon nanotubes and a binder in a mass ratio of 6:3:1 are preferentially selected as the positive electrode material.

[0111] Selection of the electrolyte concentration in Example 8

[0112] Polyaniline (PANI), functionalized carbon nanotubes and a binder were mixed in a mass ratio of 6:3:1 respectively, and the resulting materials were prepared as the positive electrodes of the battery in the manner of Example 1. The electrolytes were 2M zinc trifluoromethanesulfonate and ammonium iodide with different concentrations (0.2M, 0.3M, 0.5M). Figure 17 The positive electrode materials were respectively used as the positive electrodes of aqueous zinc-iodine batteries at a current density of 0.5 A / g (abbreviated as @0.5Ag -1 ) for the charge-discharge long cycle comparison chart. Figure 17It can be seen that different specific capacities are obtained with electrolytes of different iodine salt concentrations in this application, which are 200 mAh g -1 (0.2 M), 400 mAh g -1 (0.3 M), 700 mAh g -1 (0.5 M) from low to high. However, although the initial capacity of the high-concentration electrolyte is high, the capacity decays too fast during subsequent cycles, and the capacity retention rate is not high. At the same time, the high-concentration iodine salt will cause the shuttle of polyiodide ions, reducing the cycle life of the battery; the low-concentration iodine salt cannot meet the capacity requirements of the battery system. Therefore, the iodine concentration of 0.3 M in the electrolyte is preferentially selected as the iodine concentration of the system.

Claims

1. A composite material of polyaniline and carbon powder, characterized in that, The composite material includes: a current collector, polyaniline and carbon powder loaded on the current collector; the polyaniline and the carbon powder are both uniformly distributed.

2. The polyaniline and functionalized carbon nanotube composite material according to claim 1, characterized in that, The carbon powder is functionalized carbon powder, and the carbon powder is selected from one or more of carbon nanotubes, activated carbon or graphene; The functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder; Wherein, the polyaniline and the functionalized carbon powder form a three-dimensional network structure, and hydrogen bonds are formed between the polyaniline and the functionalized carbon powder.

3. The polyaniline and carbon powder composite material according to claim 1, wherein The mass ratio of the polyaniline to the carbon powder is (4-7):(5-2).

4. The polyaniline and carbon powder composite material according to claim 1, wherein The composite material also contains a binder, and the mass ratio of the polyaniline, the carbon powder and the binder is (4-7):(5-2):

1.

5. A method for preparing the polyaniline and carbon powder composite material according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: Mix polyaniline, carbon powder and binder and then grind them, and then add an organic solvent and mix evenly to obtain a slurry; Coat or roll the obtained slurry onto the current collector, and obtain the composite material after drying treatment.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the polyaniline, the carbon powder and the binder is (4-7):(5-2):

1.

7. The preparation method according to claim 5, wherein, The binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, and carboxymethyl cellulose; 8. The preparation method according to claim 5, characterized in that, The current collector is selected from one or more of carbon cloth, graphite paper, stainless steel mesh, stainless steel foil, titanium mesh, and titanium foil; The organic solvent is selected from one or several of N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

9. Use of the polyaniline and carbon powder composite material according to any one of claims 1 to 4 as a positive electrode material for an aqueous zinc-iodine battery.

10. An aqueous zinc-iodine battery comprising the polyaniline and carbon powder composite material according to any one of claims 1-4.

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