Zirconium diboride composite positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the field of electrochemistry, and particularly relates to a zirconium diboride composite positive electrode material and a preparation method and application thereof.The preparation method comprises the steps that a zirconium source and a boron source are mixed and then subjected to high-temperature heat treatment in an inert gas atmosphere in an environment with a reducing agent, and nanometer zirconium diboride is obtained; the preparation method comprises the following steps: fully dispersing nano zirconium diboride and activated carbon in a solvent, and fully grinding to obtain the zirconium diboride composite material. The electrode material prepared by the method is high in stability and good in cycle performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemistry, and particularly relates to a zirconium diboride composite positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Aqueous batteries exhibit great potential in energy storage and conversion applications, mainly due to their inherent safety and cost-effectiveness. Iodine (I2) is an ideal positive electrode material for aqueous batteries due to its abundant resources, non-toxicity, and high theoretical capacity (based on I / I - Redox couple, 211 mAh g -1 ).

[0003] In recent years, many studies have focused on combining iodine positive electrodes with zinc negative electrodes to develop high-performance, sustainable energy storage systems. However, the volatility of iodine, poor electronic conductivity, slow redox kinetics, and high solubility lead to rapid capacity decay and severe self-discharge phenomena. These limitations severely affect the practical performance and cycle life of Zn||I2 batteries.

[0004] To address these challenges, carbon materials such as carbon fibers, activated carbon, and carbon nanotubes have been widely studied as carriers for physically adsorbing iodine species. However, carbon-based carriers cannot effectively immobilize iodine due to weak van der Waals forces. To overcome this problem, metal compounds have been used to compensate for the shortcomings of carbon materials due to their strong interaction with iodine species. In particular, transition metal compounds such as Fe-N-C, Co9S8, and Ni-Co-DA have been shown to be able to catalyze the transformation of iodine.

[0005] To further enhance performance, it is crucial to introduce an electrocatalytic carrier that not only has catalytic activity but also has excellent electronic conductivity and can effectively immobilize iodine species. This integrated approach will more effectively promote reaction kinetics and improve cycle stability. In addition, the influence of catalyst materials on the electrocatalytic kinetics of iodine redox reactions has not been fully studied. Clarifying the catalytic mechanism will release the practical potential of the catalytic carrier in effectively alleviating the shuttle effect of iodine species, paving the way for commercialization. SUMMARY

[0006] To solve the problem of poor reversibility and low coulombic efficiency of zinc-iodine batteries caused by the shuttle effect of polyiodide in the prior art, the present application mainly provides a zirconium diboride composite positive electrode material and a preparation method thereof, and the specific technical solutions are as follows: A preparation method of a zirconium diboride composite positive electrode material, comprising the following steps: mixing a zirconium source and a boron source, then high-temperature heat-treating in an inert gas atmosphere in the presence of a reducing agent to obtain nano-zirconium diboride; and dispersing the nano-zirconium diboride and activated carbon in a solvent, and grinding for 5-20 hours to obtain a zirconium diboride composite material.

[0007] Further, the zirconium source is zirconium tetrachloride; the boron source and the reducing agent are sodium borohydride.

[0008] Further, the substance amount ratio of the zirconium source and the boron source is 1:2-3; the mass ratio of the zirconium diboride and the activated carbon is 1:3-10.

[0009] Further, the heat treatment is heat treatment at 500-700 DEG C for 5-8 h.

[0010] Further, after the heat treatment, the obtained product is washed with dilute hydrochloric acid, water and ethanol respectively, and zirconium diboride is obtained after drying.

[0011] Further, the rotation speed of the grinding is 600-1200 rpm.

[0012] A preparation method of an electrode containing a zirconium diboride composite positive electrode material, comprising the following steps: a. The above prepared positive electrode material is mixed with a conductive agent and a binder to obtain a slurry; then the slurry is coated on carbon paper, and a precursor electrode is obtained after drying; further, the precursor electrode needs to be treated in the dark and stored in a sealed manner; b. The precursor electrode is subjected to constant current electrodeposition in a mixed electrolyte of potassium iodide and zinc sulfate at a current density of 0.5-1.5 mA / cm² for 3-8 min, and then dried after water washing to obtain an electrode; further, the mixed electrolyte of potassium iodide and zinc sulfate needs to be treated in the dark.

[0013] Further, the binder is dissolved in N-methyl pyrrolidone in advance to configure a solution of 5-15 g / L, and then ultrasonic treatment is performed for 0.5-1.5 h, followed by stirring for 1-3 h to fully disperse uniformly.

[0014] Further, in the mixed electrolyte, the concentration of potassium iodide is 0.8-1.5 mol / L; and the concentration of zinc sulfate is 0.3-0.8 mol / L.

[0015] Further, the mass of the positive electrode material accounts for 75-85% of the slurry; and the electrode drying temperature should not be higher than 45 DEG C.

[0016] The electrode is used in the preparation of a water-based zinc-iodine battery.

[0017] By using the above scheme, the method has the following advantages: The zirconium diboride material is synthesized by only one step of solid phase reaction, and the highest process temperature is about 600 DEG C, which is lower than that of the traditional single element reaction method and the carbon thermal reduction method, and energy consumption can be effectively saved.

[0018] The present application first combines zirconium diboride with activated carbon, disperses and fixes zirconium diboride nanoparticles through activated carbon, effectively solves the problem of agglomeration, and effectively utilizes the physical adsorption of activated carbon to provide effective iodine adsorption sites.

[0019] Compared with the traditional iodine electrode host, the zirconium diboride / activated carbon-iodine electrode of the present application, wherein the zirconium diboride / activated carbon active material has metallic conductivity, can realize fast charge transfer. In addition, the catalytic effect of the zirconium diboride / activated carbon host makes I3 - further oxidize to iodine element, thereby releasing higher capacity and improving the utilization rate of iodine. And the zirconium diboride / activated carbon host of the present application has strong adsorption effect on I3 - , I5 - , effectively inhibits the shuttle of these ions, and improves the capacity, reversibility and cycle life of zinc-iodine batteries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a transmission electron microscope image of zirconium diboride prepared in Example 1; Figure 2 is an X-ray diffraction pattern of zirconium diboride prepared in Example 1; Figure 3 is a transmission electron microscope image of zirconium diboride / activated carbon prepared in Example 1; Figure 4 is a comparison of cyclic voltammograms of zinc-iodine batteries prepared in Examples 1, 2 and Comparative Example 1 at 10 mV / s; Figure 5 is a cyclic voltammogram of a zinc-iodine battery of a zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 at different scan rates; Figure 6 is a rate charge-discharge curve of a zinc-iodine battery of a zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 at different current densities; Figure 7 is a constant current charge-discharge curve of a zinc-iodine battery of a zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 at different current densities; Figure 8 is a specific capacity curve of a zinc-iodine battery of a zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 at 2 A·g -1 current density for long cycle charge-discharge; Figure 9 is a specific capacity curve of a zinc-iodine battery of a zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 at 10 A·g -1 current density for long cycle charge-discharge; Figure 10 is a specific capacity curve of a zinc-iodine battery of a zirconium diboride / activated carbon-iodine positive electrode prepared in Example 2 at 2 A·g-1 The specific capacity curve of long cycle charge-discharge under the current density; Figure 11 The zinc-iodine battery with the active carbon-iodine positive electrode prepared in Comparative Example 1 was subjected to long cycle charge-discharge under a current density of 2 A·g -1 The specific capacity curve of long cycle charge-discharge under the current density.

[0021] Figure 12 The zinc-iodine battery with the zirconium diboride-iodine positive electrode prepared in Comparative Example 2 was subjected to long cycle charge-discharge under a current density of 2 A·g -1 The specific capacity curve of long cycle charge-discharge under the current density. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0023] Example 1: (1) 1 mmol of anhydrous zirconium tetrachloride and 2 mmol of sodium borohydride were mixed in a glove box, and then transferred to a 50 mL stainless steel autoclave for reaction under the protection of argon, heated at 600 DEG C for 6 hours, and after cooling to room temperature, a pure black product was obtained, which was then washed with 3 M hydrochloric acid, distilled water and ethanol for several times; the product was dried at 60 DEG C under vacuum overnight to obtain ZrB2; Figure 1 It can be seen from the transmission electron microscope photograph of Example 1 that the particle size of ZrB2 prepared in Example 1 is about 10-20 nm, which is extremely small and uniform in size. Figure 2 It can be seen from the XRD pattern of Example 1 that the diffraction peaks in the figure correspond to the standard card of ZrB2, and no obvious impurity peak is present, indicating that the ZrB2 prepared by the method of the present application is a pure phase.

[0024] (2) ZrB2 and active carbon were mixed in a mass ratio of 1:4, and dispersed in ethanol, and the obtained dispersion was ultrasonically treated for 30 min to obtain a mixture; the mixture was sealed in a ball mill tank and milled at a speed of 800 rpm for 600 minutes, and finally a black powder-like ZrB2 / AC was collected; Figure 3 It can be seen from the transmission electron microscope photograph of Example 1 that the ZrB2 nanoparticles are uniformly distributed on the amorphous carbon, the presence of carbon promotes the dispersion of ZrB2 particles, and the spacing between ZrB2 particles is relatively average, avoiding the agglomeration of ZrB2 particles and the influence of ZrB2 particles far apart on the movement and transmission of ions and charges; (3) ZrB2 / AC, acetylene black and polyvinylidene fluoride binder were mixed in a mass ratio of 8:1:1 and ground into a uniform slurry; then, the slurry was coated on a 50µm thick carbon paper and dried under vacuum at 60°C for 24 hours to prepare the ZrB2 / AC precursor electrode. (4) In a mixed electrolyte of 1 M potassium iodide and 0.5 M zinc sulfate heptahydrate, at 1 mA / cm 2 A constant current electrodeposition of the ZrB2 / AC precursor electrode was performed at a current density of 300 seconds, followed by washing away the iodine ions adsorbed on the carbon paper with deionized water. Finally, the ZrB2 / AC-I2 electrode was dried overnight in an oven at 40°C to obtain the ZrB2 / AC-I2 electrode.

[0025] Example 2: (1) 1 mmol of anhydrous zirconium tetrachloride and 2 mmol of sodium borohydride were mixed in a glove box and then transferred to a 50 mL stainless steel autoclave. The reaction was carried out under argon protection and heated at 600 °C for 6 hours. After cooling to room temperature, a pure black product was obtained. The product was then washed multiple times with 3 M hydrochloric acid, distilled water and ethanol. The product was dried overnight under vacuum at 60 °C to obtain ZrB2. (2) ZrB2 and activated carbon were mixed at a mass ratio of 1:8 and ultrasonically treated in an ethanol dispersion for 30 min to obtain a mixture; the mixture was sealed in a ball mill jar and ground at 800 rpm for 600 minutes, and finally black powder ZrB2 / AC was collected. (3) ZrB2 / AC, acetylene black and polyvinylidene fluoride binder were mixed in a mass ratio of 8:1:1 and ground into a uniform slurry; then, the slurry was coated on a 50µm thick carbon paper and dried under vacuum at 60°C for 24 hours to prepare the ZrB2 / AC precursor electrode. (4) In a mixed electrolyte of 1 M potassium iodide and 0.5 M zinc sulfate heptahydrate, at 1 mA / cm 2 A constant current electrodeposition of the ZrB2 / AC precursor electrode was performed at a current density of 300 seconds, followed by washing away the iodine ions adsorbed on the carbon paper with deionized water. Finally, the ZrB2 / AC-I2 electrode was dried overnight in an oven at 40°C to obtain the ZrB2 / AC-I2 electrode.

[0026] Comparative Example 1: (1) Activated carbon, acetylene black and polyvinylidene fluoride binder were mixed in a mass ratio of 8:1:1 and ground into a uniform slurry; then, the slurry was coated on a 50µm thick carbon paper and dried under vacuum at 60°C for 24 hours to prepare an AC precursor electrode. (2) The AC precursor electrode was galvanostatically electrodeposited in a mixed electrolyte of 1 M potassium iodide and 0.5 M zinc sulfate heptahydrate at a current density of 1 mA / cm2for 300 seconds, followed by washing the iodine ions adsorbed on the carbon paper with deionized water. Finally, the electrode was dried in an oven at 40°C overnight to obtain the AC-I2 electrode.

[0027] Comparative Example 2: (1) Zirconium diboride, acetylene black and polyvinylidene fluoride binder were mixed in a mass ratio of 8:1:1 and ground into a uniform slurry; then, the slurry was coated on a 50 pm thick carbon paper and dried at 60°C under vacuum for 24 hours to prepare a ZrB2 precursor electrode; (2) The ZrB2 precursor electrode was galvanostatically electrodeposited in a mixed electrolyte of 1 M potassium iodide and 0.5 M zinc sulfate heptahydrate at a current density of 1 mA / cm2for 300 seconds, followed by washing the iodine ions adsorbed on the carbon paper with deionized water. Finally, the electrode was dried in an oven at 40°C overnight to obtain the ZrB2-I2 electrode.

[0028] Example sample testing: A 100-micron-thick zinc metal foil was selected as the negative electrode, which was polished with sandpaper in advance and punched into a 12-mm-diameter disc; a domestic GF / D glass fiber was selected as the separator, which was punched into a 15-mm-diameter disc; the electrodes of each example or comparative example were selected as the positive electrode, each with a diameter of 12 mm; a R2023 type battery shell was selected, and the negative shell was sequentially filled with a spring, a gasket, a zinc sheet, a separator, 80 microliters of electrolyte, a positive electrode, and a positive shell. Finally, the zinc-iodine full battery was sealed by a battery sealing machine under a pressure of 50 MPa. The zinc-iodine full battery was used for electrochemical testing, and the test results were as follows: Figure 4 As can be seen from the cyclic voltammetry curves of FIG. 6, at a scan rate of 1 mV / s, the introduction of ZrB2 in different proportions in Examples 1 and 2 effectively reduces the overpotential of the zinc-iodine redox reaction, and the oxidation process of iodine species on the ZrB2 / AC-I2 positive electrode is more complete than that on the AC-I2 positive electrode in Comparative Example 1, thereby exhibiting higher capacity. This indicates that ZrB2 / AC greatly improves the reversibility of the iodine conversion reaction.

[0029] Figure 5 As can be seen from the cyclic voltammetry curves of FIG. 7, at different scan rates, the CV curve of the ZrB2 / AC-I2 positive electrode in Example 1 maintains a good shape, and only a slight shift occurs in the CV curve due to weak polarization. This indicates that ZrB2 / AC promotes the fast conversion kinetics of the iodine reaction.

[0030] Figure 6is the rate charge-discharge curve of the zinc-iodine battery with the zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 under different current densities. As can be seen from the figure, the battery prepared by using the electrode of the application can ensure good charge-discharge stability at low and high rates, and after the high rate is converted to the low rate, the charge-discharge capacity can be quickly restored, indicating that the structure of the electrode prepared by the method of the application is compact, and the good cycle life can still be retained under different energy impacts.

[0031] Figure 7 is the voltage-specific capacity curve of the zinc-iodine battery with the zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 under different current densities. As can be seen from the figure, the battery prepared by using the electrode of the application can ensure good charge-discharge platform at low and high rates, indicating a high reversible conversion reaction.

[0032] Figure 8 and Figure 9 are the specific capacity curves of the long cycle charge-discharge of the zinc-iodine battery with the zirconium diboride / activated carbon-iodine positive electrode prepared in Example 1 under 2 A·g -1 and 10 A·g -1 current densities. As can be seen from the figure, the battery using the electrode of the application can maintain good cycle stability under different currents, especially after 50,000 cycles under the current density of 10 A·g -1 , the capacity has not decayed at all, and the capacity retention rate is 100%, which fully shows that the electrode prepared by the method of the application has excellent cycle stability.

[0033] Figure 10 is the specific capacity curve of the long cycle charge-discharge of the zinc-iodine battery with the zirconium diboride / activated carbon-iodine positive electrode prepared in Example 2 under 2 A·g -1 current density. When the ZrB2 and activated carbon are compounded, the proportion of activated carbon in Example 2 is higher, Figure 10 which shows that the electrode material of Example 2 also has good cycle performance, indicating that the preparation of the electrode material within the raw material proportion range of the application can ensure good performance, and the method of the application has high reproducibility and good product control.

[0034] Figure 11 is the specific capacity curve of the long cycle charge-discharge of the zinc-iodine battery with the activated carbon-iodine positive electrode prepared in Comparative Example 1 under 2 A·g -1 current density. As can be clearly seen from the figure, the capacity of the battery prepared in the comparative example without zirconium diboride begins to decay obviously after 1,000 cycles, and the capacity retention rate is only about half of the initial capacity. The performance of the electrode material prepared by the method of the application is obviously better than that of Comparative Example 1.

[0035] Figure 12is the zinc-iodine battery of the zirconium diboride-iodine positive electrode prepared in Comparative Example 2 at 2 A·g -1 The specific capacity curve of long cycle charge-discharge at current density. It can be clearly seen from the figure that the capacity of the battery prepared in Comparative Example 2 without active carbon continuously decays with the cycle, and the capacity retention rate is only about 2 / 3 of the initial. The performance of the electrode material prepared by the method of the present application is obviously better than that of Comparative Example 2. By comparing the capacity retention rate after long cycle of each example and comparative example, it can be seen that neither zirconium diboride nor active carbon alone can make the electrode material have better cycle stability, and the combination of the two can make the capacity retention rate rise sharply.

[0036] For those skilled in the art, other various corresponding changes and modifications can be made according to the technical solutions and concepts described above, and all these changes and modifications should belong to the protection scope of the claims of the present application.

Claims

1. A method for preparing a zirconium diboride composite cathode material, characterized in that, The method comprises the following steps: The zirconium source and the boron source are mixed, and then high-temperature heat treatment is performed in an inert gas atmosphere in the presence of a reducing agent to obtain nano-zirconium diboride; the nano-zirconium diboride and activated carbon are dispersed in a solvent, and then ground for 5-20 hours to obtain a zirconium diboride composite material.

2. The method of preparing a zirconium diboride composite cathode material according to claim 1, characterized in that, The zirconium source is zirconium tetrachloride; and the boron source and the reducing agent are sodium borohydride.

3. The method of claim 1, wherein the zirconium diboride composite cathode material is prepared by the steps of: mixing a zirconium compound, a boron compound, and a carbon compound to form a mixture; and heating the mixture to form the zirconium diboride composite cathode material. The mass ratio of the zirconium source to the boron source is 1:2-3; and the mass ratio of the zirconium diboride to the activated carbon is 1:3-10.

4. The method of claim 1, wherein the zirconium diboride composite cathode material is prepared by the steps of: The heat treatment is performed at 500-700℃ for 5-8 hours. ​ 5. The method of claim 1, wherein the zirconium diboride composite cathode material is prepared by the steps of: mixing a zirconium compound, a boron compound, and a carbon compound; and heating the mixture to a temperature of 800-1,200°C in a vacuum or an inert gas atmosphere. After the heat treatment, the obtained product is washed with dilute hydrochloric acid, water and ethanol respectively, and then dried to obtain zirconium diboride.

6. The method of claim 1, wherein the zirconium diboride composite cathode material is prepared by the steps of: The rotation speed of the grinding is 600-1200 rpm. ​ 7. A method of producing an electrode containing a zirconium diboride composite positive electrode material, characterized by, The method comprises the following steps: a. The positive electrode material prepared in any one of claims 1-6 is mixed with a conductive agent and a binder to obtain a slurry; then the slurry is coated on carbon paper, and dried to obtain a precursor electrode; b. The precursor electrode is subjected to constant current electrodeposition in a mixed electrolyte of potassium iodide and zinc sulfate at a current density of 0.5-1.5 mA / cm² for 3-8 minutes, and then washed with water and dried to obtain an electrode.

8. The method of claim 7, wherein the electrode is prepared by, In the mixed electrolyte, the concentration of potassium iodide is 0.8-1.5 mol / L; and the concentration of zinc sulfate is 0.3-0.8 mol / L.

9. The method of claim 7, wherein the step of applying the coating is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The mass of the positive electrode material accounts for 75-85% of the slurry; and the drying temperature of the electrode should not be higher than 45℃.

10. Use of the electrode of any one of claims 7-9 in the preparation of a water-based zinc-iodine battery.

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