Halogen positive electrode, preparation method and zinc-halogen battery

Abstract

A halogen positive electrode, a preparation method and a zinc-halogen battery. The preparation method comprises: dispersing cationic cellulose nanofibers in an organic solvent to form a dispersion; mixing and stirring the dispersion, activated carbon, ketjen black and a binder to obtain a mixed coating liquid; coating the mixed coating liquid on a current collector and drying same to form a host material; and depositing a halogen active substance on the host material to obtain a halogen positive electrode. By introducing the cationic cellulose nanofibers, the loading capacity of the halogen active substance can be effectively improved, the halogen active substance can be stably fixed on the positive electrode side, and the shuttle of the positive electrode active substance can be inhibited, thereby improving the energy density of the zinc-based halogen battery in terms of the full battery and the cycle stability at high temperatures.

Description

Halogen positive electrode, preparation method and zinc-halogen battery Technical Field

[0001] The present application relates to the technical field of battery preparation, and in particular to a halogen positive electrode, a preparation method and a zinc-halogen battery. Background Art

[0002] Aqueous zinc-based batteries have attracted widespread attention due to their high safety, cost-effectiveness, high energy density, and ease of preparation. Among the various cathode materials for zinc-based batteries, halogen cathodes, particularly iodine cathodes, stand out due to their high theoretical specific capacity and output voltage, offering a promising opportunity to increase the energy density of zinc-based batteries. Furthermore, the highly reversible and excellent kinetics of the conversion reactions of halogen cathodes contribute to the excellent cycling stability and high power density of zinc-based halogen batteries.

[0003] A major challenge for halogen cathodes is how to increase the halogen loading and effectively fix it on the cathode substrate, achieving high energy density at the full-cell level for zinc-based halogen batteries and enabling operation at high temperatures. However, the current halogen cathode active material loading is low, resulting in low energy density for the full battery. At the same time, because the adsorption between the cathode substrate material and the active material is not strong enough, the active material easily diffuses into the electrolyte and slowly diffuses to the negative electrode side through the diaphragm, causing severe self-discharge and reducing the coulombic efficiency of the battery. These problems are even more serious when the battery operates at high temperatures, greatly limiting the application range of aqueous zinc-based batteries.

[0004] Cathode modification is an effective strategy to inhibit the shuttle effect of cathode active materials. To date, many materials such as porous carbon, graphene, and MXen have been widely used to inhibit the shuttle effect of cathode active materials. Taking iodine electrode as an example, Yan et al. used porous carbon as a substrate material to confine polyiodide in the cathode. When the iodine loading was 1.6 mg cm -2 , the current density is 0.3 mA cm -2 Under these conditions, the assembled zinc-iodine battery can provide 0.2 mAh cm -2 Hoang et al. designed a three-dimensional graphene cathode to immobilize easily soluble polyiodides, effectively suppressing the shuttle effect. The assembled zinc-iodine battery has an iodine loading of 1.2 mg cm -2 , the current density is 1.2 mA cm -2 The surface capacity under these conditions reached 0.3 mAh cm -2, and can operate stably for more than 2000 times with a capacity retention rate of 96.7%. After using these porous carbon materials on the positive electrode substrate, although the specific capacity and battery cycle stability based on iodine active substances have been optimized, the iodine loading and the energy density of the whole battery are usually ignored. Specifically, since the interaction between these porous carbon materials and the positive electrode active material is mainly based on the van der Waals force adsorption of the spatial confinement effect, this interaction force is relatively weak and is not enough to construct a high-load halogen positive electrode. Recently reported zinc-iodine batteries only work at room temperature (30°C) and with relatively low iodine loading (less than 10 mg cm -2 ) were tested under low energy density and limited application range, which restricts the use of zinc-iodine batteries. Therefore, in order to achieve high energy density and stable halogen cathode at high temperature, it is urgent to explore new substrate materials to firmly confine iodine active substances.

[0005] Currently, the main method for increasing the loading of halogen active materials in the positive electrode is to coat the current collector titanium mesh with a layer of new porous carbon materials such as activated carbon, graphene, and MXene, and then use van der Waals forces to fix the halogen active materials in these host materials. This relatively weak force is insufficient to construct a high-load halogen positive electrode, and it is even more difficult to meet the high-temperature operation requirements of zinc-based halogen batteries.

[0006] Summary of the Invention

[0007] In view of this, it is necessary to provide a halogen positive electrode, a preparation method and a zinc-halogen battery with better applicability at high temperatures to address the technical problem that the existing technology is difficult to meet the requirements of zinc-based halogen batteries operating at high temperatures.

[0008] To solve the above problems, this application adopts the following technical solutions:

[0009] One of the purposes of this application is to provide a method for preparing a halogen positive electrode, comprising the following steps:

[0010] dispersing cationic cellulose nanofibers in an organic solvent to form a dispersion;

[0011] Mixing and stirring the dispersion, activated carbon, Ketjen black and binder to obtain a mixed coating liquid;

[0012] coating the mixed coating liquid on a current collector and performing a drying process to form a host material;

[0013] A halogen active material is deposited on the host material to obtain the halogen positive electrode.

[0014] In some embodiments, in the step of dispersing the cationic cellulose nanofibers in an organic solvent to form a dispersion, the organic solvent includes n-methyl-2-pyrrolidone cations.

[0015] In some embodiments, the content of the cationic cellulose nanofibers is 9.8-10.2 mg / mL.

[0016] In some embodiments, in the step of mixing and stirring the dispersion, activated carbon, Ketjen black and a binder to obtain a mixed coating liquid, the binder includes polyvinylidene fluoride.

[0017] In some embodiments, the mass ratio of the dispersion, activated carbon, Ketjen black and binder is about 2:5:2:1.

[0018] In some embodiments, the step of coating the mixed coating liquid on a current collector and drying the mixed coating liquid to form a host material specifically includes the following steps:

[0019] The mixed coating solution was coated on the current collector and dried at 75-85 °C until the organic solvent evaporated. The host material loading after drying was 9.5-10.5 mg cm -2 .

[0020] In some embodiments, the coating method includes any one of a casting method, a blade coating method, a spray coating method, and a spin coating method.

[0021] In some embodiments, the step of depositing the halogen active material on the host material to obtain the halogen positive electrode specifically includes:

[0022] A mixed solution of ZnI2 and KI2 is used as an electrolyte, and a two-electrode constant current electroplating method is adopted to deposit iodine on the host material, and then vacuum drying is performed at room temperature to obtain the halogen positive electrode.

[0023] In some embodiments, the concentrations of ZnI2 and KI2 in the electrolyte are both 0.49-0.51 M, the electroplating time is 35.8-36.2 min, and the current is 4.9-5.1 mA cm -2 The iodine loading in the halogen positive electrode is 13.8-14.2 mg cm -2 .

[0024] The second object of the present application is to provide a halogen positive electrode prepared by any of the methods for preparing a halogen positive electrode.

[0025] The third purpose of this application is to provide a zinc-halogen battery, including the halogen positive electrode.

[0026] This application adopts the above technical solution, and its beneficial effects are as follows:

[0027] The halogen positive electrode, preparation method and zinc-halogen battery provided by the present application are as follows: cationic cellulose nanofibers are dispersed in an organic solvent to form a dispersion; the dispersion, activated carbon, Ketjen black and a binder are mixed and stirred to obtain a mixed coating liquid; the mixed coating liquid is coated on a current collector and dried to form a host material; and a halogen active substance is deposited on the host material to obtain the halogen positive electrode. The halogen positive electrode and preparation method provided by the present application, by introducing cationic cellulose nanofibers, can effectively increase the loading amount of the halogen active substance and stably fix it on the positive electrode side, thereby suppressing the shuttling problem of the positive electrode active substance and improving the energy density of the zinc-based halogen battery at the full cell level and the cycle stability at high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] FIG1 is an analytical diagram showing the effect of high iodine loading on improving the energy density of a full battery as provided in this application.

[0030] FIG2 is a schematic diagram showing the principle of using cCNF provided in this application to adsorb iodine and increase iodine loading.

[0031] FIG3 is a flow chart of the steps of the method for preparing a halogen positive electrode provided in an embodiment of the present application.

[0032] FIG4 is a comparison photograph of the iodine positive electrode prepared in Example 1 of the present application and the iodine positive electrode of Comparative Example 1 immersed in a 2M ZnSO4 electrolyte at 60° C.

[0033] Figure 5 shows the iodine positive electrode prepared in Example 1 of the present application and the comparative example 1 in the zinc-iodine battery at 3A g -1 Comparison of current density and charge and discharge performance at room temperature.

[0034] Figure 6 shows the iodine positive electrode prepared in Example 1 of the present application and the comparative example 1 in the zinc-iodine battery at 2A g -1 Comparison of current density and charge and discharge performance at 60℃.

[0035] FIG7 shows the iodine positive electrode prepared in Example 2 of the present application and the comparative example 2 in the zinc-iodine battery at 2A g -1 Comparison of current density and charge and discharge performance at room temperature. DETAILED DESCRIPTION

[0036] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0039] It should be noted that the host materials for iodine cathodes are mostly porous materials such as porous carbon, graphene, and MXene. These materials rely primarily on spatially confined adsorption between the host and the iodine active species. This interaction is relatively weak, making it difficult to meet the requirements of high iodine loading and high battery energy density. The cationic cellulose nanofibers (cCNFs) provided by the present invention can be used to carry and immobilize negatively charged iodine active species. Due to the strong physicochemical adsorption effect between cCNFs and polyiodide ions, they facilitate the construction of high-loaded iodine cathodes, achieving high energy density for the entire battery and expanding the battery's applicability at high temperatures.

[0040] FIG1 is an analytical diagram showing the effect of a high iodine loading iodine positive electrode provided in this embodiment on improving the energy density of a full battery.

[0041] This embodiment improves the utilization rate of the host material by constructing a high-load iodine positive electrode, achieves high energy density at the whole battery level, and meets the requirements of zinc-based halogen batteries operating at high temperatures.

[0042] FIG2 is a schematic diagram showing the principle of using cCNF provided in this embodiment to adsorb iodine and increase iodine loading.

[0043] It can be understood that due to the strong physical and chemical adsorption effect between cCNF and polyiodide ions, it helps to construct a high-loaded iodine positive electrode, achieve high energy density of the whole battery and expand the applicability of the battery at high temperature.

[0044] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be further described in detail below by taking the multifunctional detection of atherosclerosis in blood vessels as an example, in combination with the accompanying drawings and embodiments.

[0045] Please refer to FIG3 , which is a flowchart of the steps of the method for preparing a halogen positive electrode provided in an embodiment of the present application, including the following steps S110 to S140 . The implementation method of each step is described in detail below.

[0046] Step S110: dispersing cationic cellulose nanofibers in an organic solvent to form a dispersion.

[0047] In this embodiment, the organic solvent includes n-methyl-2-pyrrolidone.

[0048] In this embodiment, the content of the cationic cellulose nanofibers is 9.8-10.2 mg / mL.

[0049] As can be appreciated, the cationic cellulose nanofibers (cCNFs) provided in this example are widely available and relatively low-cost, and can be used to carry and immobilize negatively charged iodine-active species. Due to the strong physicochemical adsorption effect between cCNFs and polyiodide ions, this facilitates the construction of a high-loaded iodine cathode, achieving high energy density in the full battery and expanding the battery's applicability at high temperatures.

[0050] Step S120: mixing and stirring the dispersion, activated carbon, Ketjen black and binder to obtain a mixed coating liquid.

[0051] In this embodiment, the binder includes polyvinylidene fluoride.

[0052] In this embodiment, the mass ratio of the dispersion, activated carbon, Ketjen black and binder is 2:5:2:1.

[0053] Step S130: coating the mixed coating liquid on a current collector and performing a drying process to form a host material.

[0054] In this embodiment, the step of coating the mixed coating liquid on the current collector and drying it to form the host material specifically includes the following steps: coating the mixed coating liquid on the current collector and drying it at 75-85°C until the organic solvent is completely volatilized. The host material loading capacity formed after drying is 9.5-10.5 mg cm -2 .

[0055] Furthermore, the coating method includes any one of a casting method, a blade coating method, a spray coating method, and a spin coating method.

[0056] It can be understood that this embodiment greatly improves the adsorption effect of the host material on electricity by introducing positively charged nano-functional materials into the positive electrode to form a strong physical and chemical adsorption effect with the halogen active substance.

[0057] Step S140: depositing a halogen active substance on the host material to obtain the halogen positive electrode.

[0058] In this embodiment, the step of depositing the halogen active substance on the host material to obtain the halogen positive electrode specifically includes: using a mixed solution of ZnI2 and KI2 as an electrolyte, adopting a two-electrode constant current electroplating method to deposit iodine on the host material, and then vacuum drying at room temperature to obtain the halogen positive electrode.

[0059] Furthermore, the concentrations of ZnI2 and KI2 in the electrolyte are both 0.49-0.51 M, the electroplating time is 35.8-36.2 min, and the current is 4.9-5.1 mA cm -2 The iodine loading in the halogen positive electrode is 13.8-14.2 mg cm -2 .

[0060] It can be understood that this embodiment improves the utilization rate of host materials by constructing a high-loaded iodine positive electrode, achieves high energy density at the full battery level, and meets the requirements of zinc-based halogen batteries operating at high temperatures. In addition, due to the negative electronegativity of the intermediate products of the halogen positive electrode reaction, the electrostatic effect can play an important role in the halogen positive electrode. Not only can a positively charged host material be introduced into the positive electrode, but the introduction of negatively charged functional groups or functional materials into the electrolyte or separator can also inhibit the diffusion of iodine active substances through electrostatic repulsion, which also helps to construct a high-iodine-loaded positive electrode.

[0061] The halogen positive electrode and preparation method provided in the present application can effectively increase the loading amount of halogen active materials and stably fix them on the positive electrode side by introducing cationic cellulose nanofibers, thereby suppressing the shuttling problem of positive electrode active materials and improving the energy density of zinc-based halogen batteries at the full battery level and the cycle stability at high temperatures.

[0062] In order to further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further elaboration of the features and advantages of the present invention, rather than for limitation of the claims of the present invention.

[0063] Example 1

[0064] cCNF, activated carbon, Ketjen black, and a binder (mass ratio of 2:5:2:1) were uniformly dispersed in an organic solvent and evenly coated on a stainless steel current collector. The mixture was then dried at 80°C until the organic solvent evaporated. Iodine was evenly plated onto the host material using a constant current electroplating method. After vacuum drying, the material was used as an iodine positive electrode. The iodine loading was approximately 4.7 mg cm -2.

[0065] Performance test: The prepared cCNF / AC@I2 cathode was used to assemble a zinc-iodine full battery, in which zinc sheet was used as negative electrode, 2M ZnSO4 was used as electrolyte, and glass fiber was used as separator. The assembled zinc-iodine full battery was -1 The capacity at the current density is 151.3 mAh g -1 ,battery life>9000 cycles.

[0066] Comparative Example 1

[0067] Performance test: The prepared AC@I2 cathode was used to assemble a zinc-iodine full battery, in which the zinc sheet was the negative electrode, 2M ZnSO4 was the electrolyte, and the glass fiber was the separator. The assembled zinc-iodine full battery was -1 The capacity at the current density is 120.9 mAh g -1 , the battery life is 700 cycles.

[0068] FIG4 is a comparison photograph of the iodine positive electrode prepared in Example 1 of the present application and the iodine positive electrode of Comparative Example 1 immersed in a 2M ZnSO4 electrolyte at 60° C.

[0069] Figure 5 shows the iodine positive electrode prepared in Example 1 of the present application and the comparative example 1 in the zinc-iodine battery at 3A g -1 Comparison of current density and charge and discharge performance at room temperature.

[0070] Figure 6 shows the iodine positive electrode prepared in Example 1 of the present application and the comparative example 1 in the zinc-iodine battery at 2A g -1 Comparison of current density and charge and discharge performance at 60℃.

[0071] Example 2

[0072] cCNF, activated carbon, Ketjen black, and a binder (mass ratio of 2:5:2:1) were uniformly dispersed in an organic solvent and evenly coated on a stainless steel current collector. The mixture was then dried at 80°C until the organic solvent evaporated. Iodine was evenly plated onto the host material using a constant current electroplating method. After vacuum drying, the material was used as an iodine positive electrode. The iodine loading was approximately 14.1 mg cm -2 .

[0073] Performance test: The prepared cCNF / AC@I2 cathode was used to assemble a zinc-iodine full battery, in which zinc sheet was used as negative electrode, 2M ZnSO4 was used as electrolyte, and hydrophilic polypropylene (PP) was used as separator. The assembled zinc-iodine full battery had a high performance at 0.2A g -1 The capacity at the current density is 182.7 mAh g -1 , the full battery energy density is 34.8Wh kg -1 .

[0074] Comparative Example 2

[0075] Performance test: The prepared cCNF / AC@I2 cathode was used to assemble a zinc-iodine full battery, in which zinc sheet was used as negative electrode, 2M ZnSO4 was used as electrolyte, and hydrophilic polypropylene (PP) was used as separator. The assembled zinc-iodine full battery had a high performance at 0.2A g -1 The capacity at the current density is 109.4 mAh g -1 , the full battery energy density is 21.3Wh kg -1 .

[0076] FIG7 is a comparison of the energy densities of the iodine positive electrode prepared in Example 2 of the present application and that of Comparative Example 2 in a zinc-iodine battery at different power densities.

[0077] In the above embodiment of the present application, taking iodine electrode as an example, the cCNF was applied to zinc-iodine battery. The results showed that the positively charged nitrogen-containing sites can effectively adsorb I3 through strong physical and chemical adsorption. - and I5 - The iodine loading capacity was greatly increased by the addition of polyiodides, thereby achieving a high-energy-density zinc-iodine full battery and stably cycling at a high temperature of 60°C. This work shows that low-cost cationic cellulose-derived materials can strongly interact with polyhalides to increase the areal capacity of the positive electrode and further improve the energy density and cycling stability of the battery at the full cell level.

[0078] It can be understood that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a halogen positive electrode, characterized in that, It includes the following steps: Disperse cationic cellulose nanofibers in an organic solvent to form a dispersion; Mix and stir the dispersion, activated carbon, Ketjen black and binder to obtain a mixed coating solution; Coat the mixed coating solution on a current collector and perform a drying treatment to form a host material; Deposit a halogen active material on the host material to obtain the halogen positive electrode.

2. The preparation method of the halogen positive electrode according to claim 1, wherein In the step of dispersing cationic cellulose nanofibers in an organic solvent to form a dispersion, the organic solvent includes N-methyl-2-pyrrolidone cation.

3. The method for preparing a halogen positive electrode according to claim 1 or 2, characterized in that, The content of the cationic cellulose nanofibers is 9.8 - 10.2 mg / mL.

4. The preparation method of the halogen positive electrode according to claim 1, characterized in that, In the step of mixing and stirring the dispersion, activated carbon, Ketjen black and binder to obtain a mixed coating solution, the binder includes polyvinylidene fluoride.

5. The method for preparing a halogen positive electrode according to claim 1 or 4, characterized in that, The mass ratio of the dispersion, activated carbon, Ketjen black and binder is about 2:5:2:

1.

6. The preparation method of the halogen positive electrode according to claim 1, characterized in that, In the step of coating the mixed coating solution on a current collector and performing a drying treatment to form a host material, it specifically includes the following steps: Apply the mixed coating solution onto the current collector and dry it at 75 - 85 °C until the organic solvent has completely volatilized. The loading of the host material formed after drying is 9.5 - 10.5 mg cm -2 .

7. The method for preparing a halogen positive electrode according to claim 1 or 6, characterized in that, The coating method includes any one of the casting method, doctor blade method, spraying method, and spin coating method.

8. The method for preparing a halogen positive electrode according to claim 1, wherein, In the step of depositing a halogen active material on the host material to obtain the halogen positive electrode, it specifically includes: Using a mixed solution of ZnI2 and KI2 as the electrolyte, adopting a two-electrode constant current electroplating method, depositing iodine on the host material, and then drying in vacuum at room temperature to obtain the halogen positive electrode.

9. The preparation method of the halogen positive electrode according to claim 1 or 8, characterized in that, The concentrations of ZnI2 and KI2 in the electrolyte are both 0.49 - 0.51 M, the electroplating time is 35.8 - 36.2 min, and the current is 4.9 - 5.1 mA cm -2 , and the iodine loading in the halogen cathode is 13.8 - 14.2 mg cm -2 .

10. A halogen positive electrode, characterized in that, Prepared by the preparation method of the halogen positive electrode according to any one of claims 1 to 9.

11. A zinc-halogen battery, characterized in that, It includes the halogen positive electrode according to claim 10.

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