Preparation of high-iodine-loading nitrogen-oxygen double-doped carbon material composite positive electrode and application of high-iodine-loading nitrogen-oxygen double-doped carbon material composite positive electrode in zinc iodine battery

Abstract

The invention relates to the technical field of zinc-iodine batteries, and provides preparation of a high-iodine-loading nitrogen-oxygen double-doped carbon material composite positive electrode and application of the high-iodine-loading nitrogen-oxygen double-doped carbon material composite positive electrode in a zinc-iodine battery. A working electrode with a high iodine loading capacity PONC / I2 composite material (PONC / I2) as an active substance is prepared, nitrogen-oxygen double-doped hierarchical porous carbon (PONC) is prepared by taking polydopamine gel as a precursor and performing high-temperature calcination, and multi-dimensional optimization of'pore structure and double-element synergy 'is combined. The strong interface chemistry brought by the rich N / O dopant on the hierarchical porous structure enhances the adsorption of iodine substances, realizes the high load of iodine, promotes the catalytic conversion kinetics of iodine and polyiodide, and relieves the capacity fading caused by the shuttle effect of the polyiodide intermediate. The capacity of the prepared positive electrode material is still kept at 60-80mAh g <-1 > after the positive electrode material is circulated for 65000 times at the current density of 10A g <-1 >, and the positive electrode material has excellent rate capability and long cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to the preparation of a high iodine-loaded nitrogen-oxygen dual-doped carbon material composite positive electrode and the application of the same in a zinc-iodine battery. Background Art

[0002] Serious energy problems have prompted people to continuously explore advanced energy storage systems with high economy, environmental protection and long cycle life. Zinc-iodine batteries have become one of the promising options due to their inherent safety, cost-effectiveness and relatively high theoretical specific capacity. However, during the discharge and charge process, the soluble intermediate polyiodine active substances are easily converted into triiodide anions (I 3 - ) dissolves in the form of iodine, resulting in low actual energy density of zinc-iodine batteries, and also leading to problems of self-discharge and low Coulomb efficiency during the cycle. These soluble polyiodide intermediates migrate to the anode side through the shuttle effect, aggravating Zn anode corrosion and causing cycle performance degradation.

[0003] In order to solve these problems, researchers have developed a variety of heteroatom-doped carbon materials as iodine carriers to improve the intrinsic properties of carbon materials, help regulate the microenvironment of the carbon surface, enhance the accessibility of active sites and provide additional pseudocapacitance. Although relevant research has achieved a series of remarkable results, the single-atom doped active sites are of a single type and mass transfer is limited, resulting in the current zinc-iodine batteries still facing the problems of slow reaction kinetics, multi-iodine shuttle effect, difficulty in increasing iodine loading and short cycle life.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a preparation method of a high iodine-loaded nitrogen-oxygen dual-doped carbon material composite positive electrode and its application in a zinc-iodine battery, so as to solve the problems of low iodine loading in the positive electrode material of zinc-iodine batteries, slow reaction kinetics, multi-iodine shuttle effect and short cycle life.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0007] Preparation of a high iodine loading nitrogen and oxygen dual-doped carbon material composite cathode and its application in zinc-iodine batteries, based on PONC / I 2 The composite material is an active material, which is obtained by grinding and mixing the active material with a conductive agent and a binder in a solvent and then coating the mixture on a current collector.

[0008] The conductive agent is carbon black.

[0009] The current collector is a titanium foil; preferably, the thickness of the titanium foil is 0.02 mm.

[0010] The adhesive is polyvinylidene fluoride; preferably, the density of polyvinylidene fluoride is 1.75-1.78 g / cm 3 .

[0011] The solvent is N-methylpyrrolidone.

[0012] The present invention also provides a method for preparing the working electrode, comprising the following steps:

[0013] Step 1. Using a simple ultrasonic polymerization method, acrylic acid is used as a monomer, N-N'methylenebisacrylamide is used as a crosslinker, and potassium persulfate is used as an initiator. The solution is placed in an ultrasonic cleaner at a water bath temperature of 45°C and ultrasonicated for 2 hours. The solution is then placed in a mold and polymerized at 60°C for 180 minutes to obtain a sodium polyacrylate gel.

[0014] Step 2. placing the sodium polyacrylate gel in a 0.1 M tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.0 to 9.0, adding 2 to 5 mg / mL dopamine hydrochloride to carry out a polymerization reaction, and washing and drying the reaction product to obtain a polydopamine hydrogel;

[0015] Step 3. Carbonize the synthesized polydopamine hydrogel and place it under N 2 In the atmosphere, the calcination temperature is 700-900°C, the heating rate is 2°C / min, and after calcination for 2-4 hours, a nitrogen-oxygen dual-doped carbon material (PONC) is prepared;

[0016] Step 4. Disperse iodine in deionized water, add PONC to the solution, control the weight ratio of iodine to PONC to be 1:1-2, ultrasonicate for 2h, react at 60℃ for 12h, centrifuge, and dry the product in a vacuum oven at 45℃ to obtain high iodine loading PONC / I 2 Composite materials.

[0017] Step 5. Resulting PONC / I 2 The composite material, carbon black and polyvinylidene fluoride are mixed and ground by dropping N-methylpyrrolidone to obtain positive electrode slurry for zinc-iodine battery; the obtained positive electrode slurry is coated on titanium foil, dried and cut into pieces to finally obtain positive electrode material for zinc-iodine battery.

[0018] Optimally, in step 1, the amount of crosslinker in the sodium polyacrylate gel is 0.6% to 0.8%, and the amount of initiator is 0.3% to 0.5%. Further optimized, the amount of crosslinker is 0.7%, and the amount of initiator is 0.44%.

[0019] Preferably, the pH of the 0.1 M Tris buffer solution in step 2 is 8.0 to 9.0, and more preferably 8.5.

[0020] Preferably, in step 2, the concentration of dopamine hydrochloride in the tris(hydroxymethyl)aminomethane buffer solution is 2-5 mg / mL; more preferably 2 mg / mL.

[0021] Preferably, the reaction polymerization time in step 2 is 6 to 12 hours; more preferably 6 hours.

[0022] Preferably, in step 3, the synthesized polydopamine hydrogel is heated in N 2 Calcination in atmosphere at 700-900°C; more preferably 800°C.

[0023] Preferably, in step 3, the synthesized polydopamine hydrogel is heated in N 2 The calcination is carried out under the atmosphere for 2 to 4 hours, more preferably 2 hours.

[0024] Preferably, the weight ratio of PONC to iodine in the composite material of step 4 is 1:1-2; more preferably 1:1.6.

[0025] Preferably, the material mixing method in steps 4 and 5 is one or both of ultrasonic-assisted dispersion and mechanical stirring.

[0026] Specifically, the time for ultrasonic-assisted dispersion is 2 to 3 hours, and more preferably 2 hours.

[0027] The rotation speed of the mechanical stirring is 200 to 300 r / min, preferably 250 r / min. The stirring time is 6 to 12 hours, preferably 8 to 12 hours.

[0028] The invention also provides a use of the working electrode for manufacturing a zinc-iodine battery.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The working electrode provided by the present invention maintains a capacity of 60 to 80 mAh / g after 65,000 cycles at a current density of 10,000 mA / g, and a capacity retention rate of 80 to 85%.

[0031] The preparation method provided by the invention has a simple process, cheap and readily available raw materials and is easy to operate.

[0032] The zinc-iodine battery positive electrode material prepared by the invention inhibits the shuttle effect and zinc anode corrosion and has excellent cycle performance.

[0033] Beneficial Effects

[0034] (1) The present invention prepares sodium polyacrylate gel by a simple ultrasonic polymerization method. Through the polymerization of dopamine, as a carbon source, a hierarchical porous carbon doped with nitrogen and oxygen diatoms with a large specific surface area is formed after a one-step high-temperature calcination, which is beneficial to the physical capture of iodine substances with high negative iodine content, and can also improve electrolyte penetration and ion transport.

[0035] (2) The technical solution of the present invention is based on nitrogen-oxygen dual-doped hierarchical porous carbon materials as carriers for loading iodine active substances, combined with the multi-dimensional optimization of "pore structure + dual element synergy" and the strong interfacial chemistry brought about by the rich N / O dopants. While enhancing the adsorption of polyiodides, it also promotes the catalytic conversion kinetics of iodine and polyiodides, and alleviates the shuttling effect of polyiodide intermediates to a certain extent, thereby greatly improving the cycle stability and electrochemical performance of aqueous zinc-iodine batteries.

[0036] (3) The aqueous zinc-iodine battery constructed with the product obtained by the technical solution of the present invention as the positive electrode has a long cycle life, good rate performance and stable performance. -1 The cycle life can reach 10,000 cycles under the test conditions; -1 The cycle life can reach 65,000 cycles at high current density, and the capacity retention rate is 82.77%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the processing process of PONC hierarchical porous carbon prepared in Examples 1 to 3;

[0038] Figure 2 This is a scanning electron microscope (SEM) image of the PONC-2 material prepared in Example 1 of the present invention;

[0039] Figure 3 This is a transmission electron microscope (TEM) image of the PONC-2 material prepared in Example 1 of the present invention;

[0040] Figure 4 This is an X-ray photoelectron spectroscopy (XPS) graph of the PONC-2 material prepared in Example 1 of the present invention;

[0041] Figure 5 and Figure 6 PONC-2 and PONC-2 / I prepared in Example 1 of the present invention 2 Specific surface area and pore size distribution diagram;

[0042] Figure 7 PONC-2 / I prepared in Example 1 of the present invention 2 SEM images of composite materials and their corresponding element distribution diagrams;

[0043] Figure 8 This is a UV-vis graph of the iodine adsorption capacity of PONC-2 prepared in Example 1 of the present invention;

[0044] Fig. 9 PONC-2 / I prepared in Examples 1 to 4 of the present invention 2 PONC-5 / I 2 Thermogravimetric curves of composite materials;

[0045] Fig.10 PONC-2 / I prepared in Example 1 of the present invention and the comparative example 2 Cyclic voltammogram of the composite material as the positive electrode material of zinc-iodine battery at a scan rate of 0.1mV / s;

[0046] Fig.11 PONC-2 / I prepared in Example 1 of the present invention and the comparative example 2 Composite materials as positive electrode materials for zinc-iodine batteries at 1Ag -1 Charge and discharge curves under current density;

[0047] Fig.12 PONC-2 / I prepared in Example 1 of the present invention and the comparative example 2 Composite materials as positive electrode materials for zinc-iodine batteries at 1Ag -1 Cyclic stability under conditions;

[0048] Fig.13 PONC-2 / I prepared in Example 1 of the present invention and the comparative example 2 Composite materials as positive electrode materials for zinc-iodine batteries at 10Ag -1 Long-term cycle stability under low temperature conditions;

[0049] Fig.14 PONC-2 / I prepared in Example 1 of the present invention and the comparative example 2 Rate performance of composite materials as positive electrode materials for zinc-iodine batteries. DETAILED DESCRIPTION

[0050] The present invention is further described below by specific examples. Unless otherwise specified, the technical means used in the present invention are methods known to those skilled in the art. In addition, the present invention includes but is not limited to the following examples, and any equivalent replacement or local improvement carried out under the spirit and principle of the present invention will be deemed to be within the protection scope of the present invention.

[0051] In the following embodiments:

[0052] Thermogravimetric analyzer (TGA): Beijing Hengjiu HTG-1

[0053] Scanning electron microscope (SEM): JEOL JSM-7001F;

[0054] Transmission electron microscope (TEM): Hitachi HT7800, Japan;

[0055] Element energy dispersive spectrometer (EDS): Peaguas XM2, USA;

[0056] D8 advanced X-ray diffractometer (XRD): BrukerAXS, Germany;

[0057] XPS photoelectron spectrometer (XPS): ESCALAB XI+, Thermo Fisher Scientific, USA;

[0058] Example 1

[0059] (1) Using a simple ultrasonic polymerization method, 10 g of acrylic acid was used as a monomer, 0.07 g of N-N'methylenebisacrylamide was added as a cross-linking agent, and 0.044 g of potassium persulfate was used as an initiator. The solution was placed in an ultrasonic cleaner at a water bath temperature of 45°C and ultrasonicated for 2 h. The solution was placed in a mold and polymerized at 60°C for 180 min to obtain a sodium polyacrylate gel. The mass of the cross-linking agent was controlled to be 0.7 wt%, and the mass of the initiator was controlled to be 0.44 wt%.

[0060] (2) placing the sodium polyacrylate gel in a 0.1 M tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.0 to 9.0, adding 2 mg / mL dopamine hydrochloride, and polymerizing for 6 hours, washing and drying the reaction product to obtain a polydopamine hydrogel, and controlling the pH of the 0.1 M tris(hydroxymethyl)aminomethane buffer solution to be 8.5;

[0061] (3) The synthesized polydopamine hydrogel was carbonized and placed in N 2 In the atmosphere, the calcination temperature was 800°C, the heating rate was 2°C / min, and after calcination for 2 hours, PONC was prepared;

[0062] (4) Dispersing iodine in deionized water, adding PONC to the solution, controlling the weight ratio of iodine to PONC to be 1:1.6, ultrasonicating for 2 h, reacting at 60 °C for 12 h, centrifuging, and drying the product in a vacuum oven at 45 °C to obtain high iodine loading PONC / I 2 Composite materials.

[0063] (5) PONC / I 2 The composite material is mixed with carbon black and polyvinylidene fluoride in a ratio of 8:1:1. N-methylpyrrolidone is added dropwise while grinding. The obtained positive electrode slurry is coated on a stainless steel foil, dried and cut to obtain a zinc-iodine battery positive electrode material.

[0064] Example 2

[0065] (1) Using a simple ultrasonic polymerization method, 10 g of acrylic acid was used as a monomer, 0.07 g of N-N'methylenebisacrylamide was added as a cross-linking agent, and 0.044 g of potassium persulfate was used as an initiator. The solution was placed in an ultrasonic cleaner at a water bath temperature of 45°C and ultrasonicated for 2 h. The solution was placed in a mold and polymerized at 60°C for 180 min to obtain a sodium polyacrylate gel. The mass of the cross-linking agent was controlled to be 0.7 wt%, and the mass of the initiator was controlled to be 0.44 wt%.

[0066] (2) placing the sodium polyacrylate gel in a 0.1 M tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.0 to 9.0, adding 5 mg / mL dopamine hydrochloride, and polymerizing for 6 hours, washing and drying the reaction product to obtain a polydopamine hydrogel, and controlling the pH of the 0.1 M tris(hydroxymethyl)aminomethane buffer solution to be 8.5;

[0067] (3) The synthesized polydopamine hydrogel was carbonized and placed in N 2 In the atmosphere, the calcination temperature was 800°C, the heating rate was 2°C / min, and after calcination for 2 hours, PONC was prepared;

[0068] (4) Dispersing iodine in deionized water, adding PONC to the solution, controlling the weight ratio of iodine to PONC to be 1:1.6, ultrasonicating for 2 h, reacting at 60 °C for 12 h, centrifuging, and drying the product in a vacuum oven at 45 °C to obtain high iodine loading PONC / I 2 Composite materials.

[0069] (5) PONC / I 2 The composite material is mixed with carbon black and polyvinylidene fluoride in a ratio of 8:1:1. N-methylpyrrolidone is added dropwise while grinding. The obtained positive electrode slurry is coated on a stainless steel foil, dried and cut to obtain a zinc-iodine battery positive electrode material.

[0070] Example 3

[0071] (1) Using a simple ultrasonic polymerization method, 10 g of acrylic acid was used as a monomer, 0.07 g of N-N'methylenebisacrylamide was added as a cross-linking agent, and 0.044 g of potassium persulfate was used as an initiator. The solution was placed in an ultrasonic cleaner at a water bath temperature of 45°C and ultrasonicated for 2 h. The solution was placed in a mold and polymerized at 60°C for 180 min to obtain a sodium polyacrylate gel. The mass of the cross-linking agent was controlled to be 0.7 wt%, and the mass of the initiator was controlled to be 0.44 wt%.

[0072] (2) placing the sodium polyacrylate gel in a 0.1 M tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.0 to 9.0, adding 2 mg / mL dopamine hydrochloride, and polymerizing for 12 hours, washing and drying the reaction product to obtain a polydopamine hydrogel, and controlling the pH of the 0.1 M tris(hydroxymethyl)aminomethane buffer solution to be 8.5;

[0073] (3) The synthesized polydopamine hydrogel was carbonized and placed in N 2 In the atmosphere, the calcination temperature was 800°C, the heating rate was 2°C / min, and after calcination for 2 hours, PONC was prepared;

[0074] (4) Dispersing iodine in deionized water, adding PONC to the solution, controlling the weight ratio of iodine to PONC to be 1:1.6, ultrasonicating for 2 h, reacting at 60 °C for 12 h, centrifuging, and drying the product in a vacuum oven at 45 °C to obtain high iodine loading PONC / I 2 Composite materials.

[0075] (5) PONC / I 2 The composite material is mixed with carbon black and polyvinylidene fluoride in a ratio of 8:1:1. N-methylpyrrolidone is added dropwise while grinding. The obtained positive electrode slurry is coated on a stainless steel foil, dried and cut to obtain a zinc-iodine battery positive electrode material.

[0076] Example 4

[0077] (1) Using a simple ultrasonic polymerization method, 10 g of acrylic acid was used as a monomer, 0.07 g of N-N'methylenebisacrylamide was added as a cross-linking agent, and 0.044 g of potassium persulfate was used as an initiator. The solution was placed in an ultrasonic cleaner at a water bath temperature of 45°C and ultrasonicated for 2 h. The solution was placed in a mold and polymerized at 60°C for 180 min to obtain a sodium polyacrylate gel. The mass of the cross-linking agent was controlled to be 0.7 wt%, and the mass of the initiator was controlled to be 0.44 wt%.

[0078] (2) placing the sodium polyacrylate gel in a 0.1 M tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.0 to 9.0, adding 2 mg / mL dopamine hydrochloride, and polymerizing for 6 hours, washing and drying the reaction product to obtain a polydopamine hydrogel, and controlling the pH of the 0.1 M tris(hydroxymethyl)aminomethane buffer solution to be 8.5;

[0079] (3) The synthesized polydopamine hydrogel was carbonized and placed in N 2 In the atmosphere, the calcination temperature was 800°C, the heating rate was 2°C / min, and after calcination for 2 hours, PONC was prepared;

[0080] (4) Dispersing iodine in deionized water, adding PONC to the solution, controlling the weight ratio of iodine to PONC to be 1:1, ultrasonicating for 2 h, reacting at 60 °C for 12 h, centrifuging, and drying the product in a vacuum oven at 45 °C to obtain high iodine loading PONC / I 2 Composite materials.

[0081] (5) PONC / I 2 The composite material is mixed with carbon black and polyvinylidene fluoride in a ratio of 8:1:1. N-methylpyrrolidone is added dropwise while grinding. The obtained positive electrode slurry is coated on a stainless steel foil, dried and cut to obtain a zinc-iodine battery positive electrode material.

[0082] Comparative Example 1

[0083] This comparative example provides a positive electrode material for a zinc-iodine battery.

[0084] (1) Using commercial granular activated carbon (AC), grinding it for 10 to 30 minutes until it becomes powder;

[0085] (2) Disperse iodine in deionized water, add AC to the solution, control the weight ratio of iodine to AC to be 1:1.6, sonicate for 2 h, react at 60 °C for 12 h, centrifuge, and dry the product in a vacuum oven at 45 °C to obtain AC / I with high iodine loading. 2 Composite materials.

[0086] (3) AC / I 2 The composite material is mixed with carbon black and polyvinylidene fluoride in a ratio of 8:1:1. N-methylpyrrolidone is added dropwise while grinding. The obtained positive electrode slurry is coated on a stainless steel foil, dried and cut to obtain a zinc-iodine battery positive electrode material.

[0087] Performance Testing

[0088] The morphology of Example 1 was observed using a scanning electron microscope and a projection electron microscope. Figure 2 and Figure 3 As shown, the PONC prepared in Example 1 has abundant porous structure and presents a relatively amorphous structure. In addition, the thickness of the carbon nanosheet is about 10 nm, and the carbon interlayer spacing is enlarged to 0.426 nm, which is attributed to the successful incorporation of N and O.

[0089] X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of C, O and N elements in the PONC prepared in Example 1. Figure 4The high-resolution N1s spectrum of PONC is deconvoluted into three peaks at 389.3, 400.7, and 402.5 eV, which are pyridinic-N, pyridinic-N, and graphite-N, respectively. The high-resolution XPS spectra of C1s and O1s of PONC contain not only CC / C=C, but also CO / CN, -OH, and C=O groups, further illustrating the successful doping of nitrogen and oxygen.

[0090] PONC and PONC-I 2 BET test was performed to analyze its specific surface area and pore size distribution, such as Figure 5 and 6 As shown in Figure 2, PONC-2 has abundant mesopore distribution (2-4 nm) and a large surface area (1242.83 m 2 g -1 ). The isotherm is at P / P 0 <0.01, and absorbs rapidly at 0.4 <P / P 0 <0.9, a hysteresis loop is observed, and it increases slightly at high relative pressures (0.9 <P / P 0 <1), showing hierarchical porous characteristics. After loading iodine, the specific surface area and pore volume of PONC decreased sharply, which further indicated that a large amount of I 2 Captured in the pores rather than on the surface.

[0091] The elemental analysis of the samples was performed using the energy spectrometer equipped with the scanning electron microscope. Figure 7 It can be seen that iodine is evenly distributed in the PONC prepared in Example 1. In addition, PONC also has excellent adsorption capacity for iodine. The iodine solution after adding PONC is tested, and the results are as follows: Figure 8 As shown, the iodine signal peak intensity dropped sharply 6 hours after the addition of PONC and disappeared completely after 12 hours.

[0092] PONC-I prepared in Examples 1 to 2 2 Thermogravimetric characterization was performed and the results were as follows Fig. 9 PONC-I was prepared in Example 1 2 The amount of iodine in the PONC-I is 58 wt % and 51 wt % in Example 2, indicating that the PONC-I doped with nitrogen and oxygen atoms 2 It has an excellent hierarchical porous structure, combining chemical adsorption and physical anchoring of more iodine.

[0093] The positive electrode materials obtained in Examples 1, 2, 3, and 4 were cut into a circular shape with a diameter of 12 mm and directly used as the positive electrode of the zinc-iodine battery. Metal zinc was used as the negative electrode, and the electrolyte was 2 M ZnSO 4The separator is glass fiber, and they are assembled into 2032 button cells in air. The electrochemical performance is tested in the voltage range of 0.6 to 1.6 V using an electrochemical workstation and a battery testing system.

[0094] When the positive electrode materials prepared in Example 1 were used as positive electrodes, the -1 The cyclic voltammogram at the scanning speed is as follows Fig.10 As shown. Fig.10 It can be seen that there is a pair of redox peaks corresponding to I 2 / I - By comparing Example 1 with the comparative example, it can be seen that the positive electrode material prepared in Example 1 has stronger conductivity, smaller potential difference of redox peak, smaller electrode polarization and better reaction kinetics.

[0095] When the positive electrode materials prepared in Example 1 and Comparative Example are used, -1 The charge and discharge curves under current density are as follows Fig.11 As shown in the figure, compared with the comparative example, the potential difference between the corresponding charge and discharge platforms of Example 1 is small, indicating that its electrode polarization is small.

[0096] When the composite materials prepared in Example 1 and the comparative example were used as positive electrode materials, the -1 Cyclic stability and coulombic efficiency test under current density, the results are as follows Fig.12 As shown. Fig.11 It can be seen that the specific capacity and cycle stability of the battery in Example 1 are better than those of the comparative example, and the coulombic efficiency is close to 100%. Fig.13 At 10A g -1 By performing more cycles at a high current density, it can be seen that the above experimental results are also presented.

[0097] The rate performance of the full battery prepared in Example 1 was tested under the following conditions: the charge and discharge mode was constant current charging, and the current density was 0.1, 0.2, 0.3, 0.5, 1, 2, 5, 10, 5, 1, 0.1Ag. -1 The rate performance cycle curve of the full battery prepared in Example 1 is as follows: Fig.14 As shown, it exhibits excellent rate performance.

[0098] Embodiments 2, 3, and 4 also present substantially the same effects as above.

[0099] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Preparation of a high iodine loading nitrogen and oxygen dual-doped carbon material composite positive electrode and its application in zinc-iodine battery, using PONC / I2 composite material as active material, grinding and mixing the active material with a conductive agent and a binder in a solvent, and coating the mixed material on a current collector; the working electrode is prepared at a current density of 10Ag -1 After 65,000 cycles, the capacity remains at 60-80 mAh g -1 , the capacity retention rate is 80-85%; the PONC / I2 composite material, using polydopamine gel as a precursor to prepare nitrogen-oxygen dual-doped hierarchical porous carbon (PONC), combined with the multi-dimensional optimization of "pore structure + dual element synergy", not only increases the iodine loading, but also the strong interface chemistry brought by the rich N / O dopants, while enhancing the adsorption of polyiodides, it also promotes the catalytic conversion kinetics of iodine and polyiodides, and alleviates the shuttling effect of polyiodide intermediates to a certain extent, thereby greatly improving the cycle stability and electrochemical performance of aqueous zinc-iodine batteries.

2. In the PONC / I2 composite material, the mass percentage of iodine is 58wt%; according to the SEM and TEM images of the PONC / I2 composite material, a three-dimensional hierarchical porous structure can be observed; The conductive agent is carbon black; the current collector is titanium foil; the adhesive is polyvinylidene fluoride; and the solvent is N-methylpyrrolidone; A method for preparing a high iodine loading PONC / I2 composite working electrode, characterized in that: The following steps are involved: Step 1. Using a simple ultrasonic polymerization method, acrylic acid is used as a monomer, N-N'methylenebisacrylamide is used as a crosslinker, and potassium persulfate is used as an initiator. The solution is placed in an ultrasonic cleaner at a water bath temperature of 45°C and ultrasonicated for 2 hours. The solution is then placed in a mold and polymerized at 60°C for 180 minutes to obtain a sodium polyacrylate gel. Step 2. placing the sodium polyacrylate gel in a 0.1 M tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.0 to 9.0, adding dopamine hydrochloride, wherein the concentration of dopamine hydrochloride in the tris(hydroxymethyl)aminomethane buffer solution is 2 to 5 mg / mL, performing a polymerization reaction, and washing and drying the reaction product to obtain a polydopamine hydrogel; Step 3. Carbonize the synthesized polydopamine hydrogel, place it in a N2 atmosphere, calcine it at a temperature of 700-900°C, and heat it up at a rate of 2°C / min for 2-4 hours to prepare PONC; Step 4. Disperse iodine in deionized water, add PONC to the solution, control the weight ratio of iodine to PONC to be 1:1-2, ultrasonicate for 2 hours, react at 60°C for 12 hours, centrifuge, and dry the product in a vacuum oven at 45°C to obtain a high iodine-loaded PONC / I2 composite material. Step 5. The obtained PONC / I2 composite material is mixed with carbon black and polyvinylidene fluoride by adding N-methylpyrrolidone and grinding to obtain a positive electrode slurry for a zinc-iodine battery; the obtained positive electrode slurry is coated on a titanium foil, dried, and cut to obtain a positive electrode material for a zinc-iodine battery.

3. The method for preparing a high iodine loading PONC / I2 composite working electrode according to claim 1, characterized in that: In step 1, the amount of crosslinking agent in the sodium polyacrylate gel is 0.35-0.4wt%, and the amount of initiator is 0.22-0.4wt%. The ultrasonic treatment time was 2 h.

4. The method for preparing a high iodine loading PONC / I2 composite working electrode according to claim 1, characterized in that: In step 2, the polymerization reaction time is 6 to 12 hours, and the polymerization reaction temperature is 25°C.

5. The method for preparing a high iodine loading PONC / I2 composite working electrode according to claim 1, characterized in that: In step 2, the concentration of dopamine hydrochloride in the tris(hydroxymethyl)aminomethane buffer solution is 2-5 mg / mL.

6. The method for preparing a high iodine loading PONC / I2 composite working electrode according to claim 1, characterized in that: In step 3, the synthesized polydopamine gel is calcined in a N2 atmosphere at a temperature of 700-900°C, a calcination time of 2-4 hours, and a heating rate of 2°C / min.

7. The method for preparing a high iodine loading PONC / I2 composite working electrode according to claim 1, characterized in that: In step 4, the concentration of the iodine solution is 0.13 mol / L, and the iodine solution is aged in an oven at 60° C. for 12 to 24 h.

8. The method for preparing a high iodine loading PONC / I2 composite working electrode according to claim 1, characterized in that: In step 4, the oven temperature during drying is 40 to 60° C. and the time is 12 to 48 hours.

9. The preparation method according to claim 1, characterized in that: In the step (3), the weight ratio of iodine to PONC in the composite material is 1:1-2.

10. A positive electrode material prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The working electrode is used for manufacturing zinc-iodine batteries.

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