Phenothiazine type zinc-iodine battery electrolyte and zinc-iodine battery

Abstract

The invention provides a phenothiazine type zinc-iodine battery electrolyte and a zinc-iodine battery, and the phenothiazine type zinc-iodine battery electrolyte comprises soluble zinc salt, soluble iodine salt, methylene blue and water. The zinc-iodine battery comprises a positive current collector, a negative electrode and an electrolyte, the electrolyte is located between the positive current collector and the negative electrode, and the electrolyte is the phenothiazine type zinc-iodine battery electrolyte. According to the zinc-iodine battery adopting the electrolyte, the energy density of the battery is kept, and meanwhile, the multi-iodide shuttle effect is effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a phenothiazine type zinc-iodine battery electrolyte and a zinc-iodine battery. Background Art

[0002] Aqueous zinc-ion batteries (ZIBs), as a highly safe energy storage device, can effectively avoid the high flammability risk of traditional lithium-ion batteries and show unique application potential. Among the many ZIBs cathode material systems, iodine-based cathode materials have become a hot topic of current research due to their low cost, excellent working voltage and high specific capacity. However, the multi-iodide shuttle effect generated by the zinc-iodine battery system during the battery cycle seriously restricts its practical application. This phenomenon is mainly due to the reaction between the alkaline I⁻ in the electrolyte and the Lewis acid I2 on the cathode (positive electrode) surface to generate multi-iodide intermediates with high solubility characteristics. These multi-iodides migrate across the membrane driven by the concentration gradient and react with the metal zinc anode (negative electrode), which ultimately leads to a series of problems such as increased self-discharge of the battery, corrosion of the zinc anode and irreversible loss of cathode active materials.

[0003] To solve the key problem of polyiodide shuttle effect, previous researchers have proposed a variety of strategies. For example, porous conductive substrates (such as activated carbon, mesoporous carbon and coordination polymer framework) are used as host materials to limit the migration of iodine by physical adsorption. In addition, chemical coordination is also a method. A variety of organic materials (such as tetraalkylammonium salts, polymers, etc.) can chemically coordinate with polyiodide molecules. The strong chemical interaction between organic functional groups and iodine / polyiodide can eliminate the shuttle effect in battery operation and improve the self-discharge problem of the battery.

[0004] However, although the above strategies have achieved certain results in suppressing the poly-iodide shuttle effect, these methods all rely on the loading of high-quality adsorbent materials or organic ligands, which significantly reduces the mass proportion of active materials. Specifically, in the physical adsorption strategy, the mass of activated carbon usually accounts for more than 50% of the total mass of the positive electrode material, resulting in a mass proportion of active iodine of less than 50%; similarly, in the chemical coordination strategy, the mass proportion of the coordinated ligand often exceeds 30% of the total mass of the positive electrode material. This status quo of low active material mass ratio seriously restricts the energy density of the battery and is difficult to meet the needs of practical applications. Therefore, the development of a new strategy that can effectively suppress the poly-iodide shuttle effect while maintaining a high active material ratio has become an urgent need for current research. Summary of the invention

[0005] In order to solve the above problems of the prior art, the present invention provides a phenothiazine-type zinc-iodine battery electrolyte and a zinc-iodine battery, which effectively suppress the multi-iodide shuttle effect while maintaining the battery energy density.

[0006] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a phenothiazine-type zinc-iodine battery electrolyte, comprising: a soluble zinc salt, a soluble iodine salt, methylene blue and water.

[0007] Preferably, the zinc salt is one of zinc chloride, zinc sulfate, zinc perchlorate and zinc acetate.

[0008] Preferably, the iodized salt is zinc iodide.

[0009] Preferably, the concentration of methylene blue is 0.02~0.2M.

[0010] Preferably, the concentration of the zinc salt is 15-25 M, and the concentration of the iodine salt is 1.0-5.0 M.

[0011] In a second aspect, the present invention provides a zinc-iodine battery, comprising a positive electrode current collector, a negative electrode and an electrolyte, wherein the electrolyte is located between the positive electrode current collector and the negative electrode, and the electrolyte is the phenothiazine-type zinc-iodine battery electrolyte as described above.

[0012] Preferably, the positive electrode current collector is a carbon nanotube film.

[0013] Preferably, the carbon nanotube film is a carbon nanotube film formed by a composite of multi-walled carbon nanotubes and single-walled carbon nanotubes.

[0014] Preferably, the zinc-iodine battery further comprises a first diaphragm and a second diaphragm, the first diaphragm is located between the positive electrode current collector and the electrolyte, the second diaphragm is located between the electrolyte and the negative electrode, the first diaphragm is a polyolefin diaphragm, and the second diaphragm is a glass fiber diaphragm.

[0015] In a third aspect, the present invention provides the use of methylene blue as an additive in a zinc-iodine battery electrolyte or a zinc-iodine battery.

[0016] Compared with the prior art, the present invention has the following beneficial effects: In the zinc-iodine battery electrolyte of the present invention, zinc salt is used as an electrolyte, and iodine salt forms iodine positive electrode material during the reaction. During the battery cycle, the iodine positive electrode material reacts with the alkaline I⁻ in the electrolyte to generate polyiodide. In order to avoid the shuttle effect of polyiodide, the present invention introduces methylene blue as an additive in the zinc-iodine battery electrolyte. Methylene blue, as a P-type phenothiazine molecule, is a typical Lewis soft acid, which can stably complex with polyiodide (Lewis soft base) generated during the battery charging and discharging process, thereby effectively inhibiting the polyiodide shuttle effect. In addition, the methylene blue molecule contains a capacity-contributing phenothiazine ring, which can be reversibly oxidized and provide capacity during charging and discharging, that is, methylene blue is also used as a highly active material. Therefore, the addition of methylene blue effectively inhibits the polyiodide shuttle effect while maintaining the battery energy density, and improves the cycle stability and electrochemical performance of the zinc-iodine battery. This innovative strategy provides a new idea for the development of high-performance zinc-iodine batteries. Compared with the traditional physical adsorption or organic material loading method, the present invention can effectively suppress the shuttling effect of polyiodides while maintaining a high active material ratio.

[0017] In the zinc-iodine battery assembled based on the electrolyte of the present invention, methylene blue can stably complex with polyiodides generated during the battery charging and discharging process, thereby effectively inhibiting the polyiodide shuttle effect. At the same time, methylene blue can be reversibly oxidized and provide capacity during charging and discharging, so that the zinc-iodine battery has good cycle stability and high battery capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The working mechanism diagram of methylene blue additive; (a) no methylene blue added, (b) methylene blue added, (c) reaction mechanism.

[0020] Figure 2 The effect of different concentrations of methylene blue additive on the electrochemical performance of zinc-iodine batteries.

[0021] Figure 3 The self-discharge curves of zinc-iodine batteries corresponding to two electrolytes; (a) zinc-iodine battery of comparative example 1, (b) zinc-iodine battery of example 13.

[0022] Figure 4 It is the long cycle curve of the zinc-iodine battery of comparative example 1 and embodiment 13 at a large rate.

[0023] Figure 5 In-situ optical microscope tests of zinc-iodine batteries during the charge and discharge process for two electrolytes; (a) zinc-iodine battery of comparative example 1, (b) zinc-iodine battery of example 13.

[0024] Figure 6 In-situ Raman tests of zinc-iodine batteries during the charge and discharge process corresponding to two electrolytes; (a) zinc-iodine battery of comparative example 1, (b) zinc-iodine battery of example 13. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0027] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0028] From the above analysis, it can be seen that the problem of low battery energy density originates from the electrochemical inertness of the adsorption material or the coordination ligand. Here, the present invention proposes an electrolyte with a P-type phenothiazine molecule - methylene blue (MB) as an active additive to suppress the polyiodide shuttling effect without sacrificing energy density. The methylene blue molecule is composed of a phenothiazine ring with capacity contribution and a tetraalkylammonium functional group that can fix polyiodides. During the charge and discharge process, the phenothiazine ring can be reversibly oxidized and provide capacity. At the same time, the polyiodides generated during the battery charge and discharge process coordinate with the tetraalkylammonium functional groups on the methylene blue molecules and precipitate on the cathode current collector (positive electrode current collector) ( Figure 1 ). This unique active additive effectively inhibits the multi-iodide shuttle effect while maintaining the battery energy density, improving the cycle stability and electrochemical performance of zinc-iodine batteries.

[0029] The phenothiazine zinc-iodine battery electrolyte (MBI electrolyte for short) of the present invention comprises: a soluble zinc salt, a soluble iodine salt, methylene blue and water.

[0030] The zinc salt is used as an electrolyte to provide zinc ions; the iodide salt will be deposited on the positive electrode collector as an iodine positive electrode material when the battery undergoes electrochemical reaction; and methylene blue is used as an additive to fix the polyiodides formed in the electrochemical reaction, thereby inhibiting the polyiodide shuttle effect and improving the cycle stability and electrochemical performance of the zinc-iodine battery.

[0031] In some embodiments of the present invention, the zinc salt is one of zinc chloride, zinc sulfate, zinc perchlorate and zinc acetate, and the iodized salt is zinc iodide.

[0032] In some embodiments of the present invention, in the phenothiazine zinc-iodine battery electrolyte, the concentration of zinc salt is 15~25M, the concentration of iodine salt is 1.0~5.0 M; the concentration of methylene blue is 0.02~0.2 M, and the concentration of methylene blue is more preferably 0.1~0.2 M.

[0033] The phenothiazine type zinc-iodine battery electrolyte of the present invention can be prepared by simple mixing, for example: zinc salt, iodine salt, methylene blue and water are stirred and mixed to obtain the phenothiazine type zinc-iodine battery electrolyte.

[0034] Based on the phenothiazine-type zinc-iodine battery electrolyte, the present invention assembles a zinc-iodine battery, which includes a positive electrode collector, a negative electrode, a first diaphragm, a second diaphragm and an electrolyte, wherein the electrolyte is located between the positive electrode collector and the negative electrode, the first diaphragm is located between the positive electrode collector and the electrolyte, and the second diaphragm is located between the electrolyte and the negative electrode. The electrolyte is the phenothiazine-type zinc-iodine battery electrolyte described in the present invention.

[0035] In some embodiments of the present invention, the positive electrode current collector is a carbon nanotube film, specifically a carbon nanotube film formed by a composite of multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs); wherein, by mass percentage, the multi-walled carbon nanotubes account for 85% to 95%, and the single-walled carbon nanotubes account for 5% to 15%. The thickness of the carbon nanotube film is 50 to 100 μm.

[0036] The positive electrode current collector preparation method is as follows: multi-walled carbon nanotubes and single-walled carbon nanotubes are dispersed in an appropriate amount of isopropanol, and subjected to strong ultrasonic treatment for 10 to 30 minutes; then, the obtained mixture is reacted under stirring conditions for 12 to 24 hours, and then filtered and washed with ethanol; the obtained filter cake is dried at 60° C. for 30 minutes, and finally a carbon nanotube film is prepared as the positive electrode current collector.

[0037] The present invention uses a carbon nanotube film as a positive electrode current collector, because the carbon nanotube film has the characteristics of high conductivity, high specific surface area, high mechanical strength, corrosion resistance, light weight, etc., so the positive electrode based on the carbon nanotube film of the present invention can improve the electron transmission efficiency, capacity and battery life, and can also reduce the weight of the zinc-iodine battery. In addition, the present invention uses a combination of single-walled carbon nanotubes and multi-walled carbon nanotubes, which can combine the high conductivity and high strength of single-walled carbon nanotubes and the structural stability and good flexibility of multi-walled carbon nanotubes. The two work synergistically to improve the overall performance of zinc-iodine batteries.

[0038] In some embodiments of the present invention, the negative electrode is a zinc negative electrode.

[0039] In some embodiments of the present invention, the first separator is a polyolefin separator, and the second separator is a glass fiber separator.

[0040] The zinc-iodine battery assembled based on the phenothiazine-type zinc-iodine battery electrolyte of the present invention significantly reduces the deposition amount of polyiodide during the charge and discharge process, and significantly improves the cycle stability of the zinc-iodine battery.

[0041] Example 1 The present embodiment provides a phenothiazine type zinc-iodine battery electrolyte, comprising: zinc chloride, zinc iodide, methylene blue and water; wherein the concentration of zinc chloride is 20 M, the concentration of zinc iodide is 3.0 M, and the concentration of methylene blue is 0.1 M.

[0042] The preparation method of the phenothiazine type zinc-iodine battery electrolyte is as follows: zinc chloride, zinc iodide and methylene blue are added into water, and stirred to obtain the electrolyte.

[0043] Embodiment 2~4 The method is basically the same as Example 1, except that the concentrations of methylene blue in Examples 2 to 4 are 0.02 M, 0.05 M, and 0.2 M, respectively.

[0044] Example 5 This embodiment provides a phenothiazine-type zinc-iodine battery electrolyte, comprising: zinc sulfate, zinc iodide, methylene blue and water; wherein the concentration of zinc sulfate is 15 M, the concentration of zinc iodide is 2.0 M, and the concentration of methylene blue is 0.05 M.

[0045] The preparation method of the phenothiazine type zinc-iodine battery electrolyte is as follows: zinc sulfate, zinc iodide and methylene blue are added into water, and stirred to obtain the electrolyte.

[0046] Example 6 The present embodiment provides a phenothiazine zinc-iodine battery electrolyte, comprising: zinc perchlorate, zinc iodide, methylene blue and water; wherein the concentration of zinc perchlorate is 20 M, the concentration of zinc iodide is 3.0 M, and the concentration of methylene blue is 0.1 M.

[0047] The preparation method of the phenothiazine type zinc-iodine battery electrolyte is as follows: zinc perchlorate, zinc iodide and methylene blue are added into water, and stirred to obtain the electrolyte.

[0048] Example 7 This embodiment provides a phenothiazine zinc-iodine battery electrolyte, comprising: zinc acetate, zinc iodide, methylene blue and water; wherein the concentration of zinc acetate is 20 M, the concentration of zinc iodide is 3.0 M, and the concentration of methylene blue is 0.15 M.

[0049] The preparation method of the phenothiazine type zinc-iodine battery electrolyte is as follows: zinc acetate, zinc iodide and methylene blue are added into water, and stirred to obtain the electrolyte.

[0050] Example 8 This embodiment provides a phenothiazine zinc-iodine battery electrolyte, including: zinc chloride, zinc iodide, methylene blue and water; wherein the concentration of zinc chloride is 25 M, the concentration of zinc iodide is 5.0 M, and the concentration of methylene blue is 0.2 M.

[0051] The preparation method of the phenothiazine type zinc-iodine battery electrolyte is as follows: zinc chloride, zinc iodide and methylene blue are added into water, and stirred to obtain the electrolyte.

[0052] Example 9 This embodiment provides a phenothiazine zinc-iodine battery electrolyte, comprising: zinc chloride, zinc iodide, methylene blue and water; wherein the concentration of zinc chloride is 15 M, the concentration of zinc iodide is 1.0 M, and the concentration of methylene blue is 0.02 M.

[0053] The preparation method of the phenothiazine type zinc-iodine battery electrolyte is as follows: zinc chloride, zinc iodide and methylene blue are added into water, and stirred to obtain the electrolyte.

[0054] Example 10 This embodiment provides a zinc-iodine battery, comprising a positive electrode current collector, a negative electrode, a separator, and the electrolyte described in Embodiment 2.

[0055] The positive electrode current collector is made of multi-walled carbon nanotubes, single-walled carbon nanotubes and isopropanol: 42.5 mg of multi-walled carbon nanotubes and 7.5 mg of single-walled carbon nanotubes are dispersed in 30 mL of isopropanol and subjected to strong ultrasonic treatment for 10 minutes; then, the resulting mixture is reacted under stirring conditions for 12 hours, and then filtered and washed with ethanol; the resulting filter cake is dried at 60°C for 30 minutes, and finally a carbon nanotube film is prepared as the positive electrode current collector.

[0056] The negative electrode is a metal zinc sheet. The zinc sheet negative electrode needs to be polished with 2000-grit sandpaper before use. After polishing for 20 minutes, it is polished with 0.3 mm and 0.05 mm aluminum oxide polishing powder and anhydrous ethanol respectively; then it is ultrasonically cleaned in a mixed solution of acetone, deionized water and isopropanol (acetone, deionized water and isopropanol volume ratio 1:1:1), and after drying at room temperature, it is punched into discs with a diameter of 12 mm.

[0057] The separators include polyolefin separators and glass fiber separators.

[0058] The positive electrode current collector, negative electrode, electrolyte and separator are assembled into button cells for electrical performance testing. The battery shell model is CR2032, the glass fiber separator model is Whatman GF / A, and the polyolefin separator model is Celgard 3501. The battery shell is assembled in the order of positive electrode shell-19mm titanium sheet-silicone gasket (outer diameter 19 mm, inner diameter 8 mm, thickness 0.2 mm)-carbon nanotube film (diameter 8mm, thickness 80 μm)-polyolefin separator-MBI electrolyte-glass fiber separator-zinc negative electrode (diameter 12 mm)-16 mm titanium sheet-gasket-spring-negative electrode shell, and then the battery is sealed using a tablet press. During the assembly process, avoid contact between the tweezers and the positive and negative electrodes to cause a short circuit.

[0059] Embodiment 11 This embodiment provides a zinc-iodine battery, including a positive electrode current collector, a negative electrode, a separator, and the electrolyte described in Example 6.

[0060] The positive electrode current collector is made of multi-walled carbon nanotubes, single-walled carbon nanotubes and isopropanol: 45 mg of multi-walled carbon nanotubes and 5 mg of single-walled carbon nanotubes are dispersed in 40 mL of isopropanol in proportion and subjected to strong ultrasonic treatment for 20 minutes. Subsequently, the resulting mixture is reacted under stirring conditions for 18 hours, then filtered and washed with ethanol. The resulting filter cake is dried at 60°C for 30 minutes, and finally a carbon nanotube film is prepared as the positive electrode current collector.

[0061] The negative electrode is a metal zinc sheet, which is processed according to the method of Example 10.

[0062] The separators include polyolefin separator Celgard 2325 and glass fiber separator Whatman GF / A.

[0063] The positive electrode current collector, negative electrode, electrolyte and separator were assembled into a button battery according to the method of Example 10, and the electrical performance was tested.

[0064] Example 12 This embodiment provides a zinc-iodine battery, comprising a positive electrode current collector, a negative electrode, a separator, and the electrolyte described in Embodiment 7.

[0065] The positive electrode current collector is made of 47.5 mg multi-walled carbon nanotubes, 2.5 mg single-walled carbon nanotubes and isopropanol: the multi-walled carbon nanotubes and single-walled carbon nanotubes are dispersed in 50 mL of isopropanol and subjected to strong ultrasonic treatment for 30 minutes; then, the resulting mixture is reacted under stirring conditions for 24 hours, and then filtered and washed with ethanol; the resulting filter cake is dried at 60°C for 30 minutes, and finally a carbon nanotube film is prepared as the positive electrode current collector.

[0066] The negative electrode is a metal zinc sheet, which is processed according to the method of Example 10.

[0067] The separators include polyolefin separator Celgard 2500 and glass fiber separator Whatman GF / A.

[0068] The positive electrode current collector, negative electrode, electrolyte and separator were assembled into a button battery according to the method of Example 10, and the electrical performance was tested.

[0069] Embodiment 13 This embodiment provides a zinc-iodine battery, comprising a positive electrode current collector, a negative electrode, a separator, and the electrolyte described in Embodiment 1.

[0070] The positive electrode current collector is made of multi-walled carbon nanotubes, single-walled carbon nanotubes and isopropanol: 45 mg of multi-walled carbon nanotubes and 5 mg of single-walled carbon nanotubes are dispersed in 50 mL of isopropanol and subjected to strong ultrasonic treatment for 10 minutes; then, the resulting mixture is reacted under stirring conditions for 24 hours, and then filtered and washed with ethanol; the resulting filter cake is dried at 60°C for 30 minutes, and finally a carbon nanotube film is prepared as the positive electrode current collector.

[0071] The negative electrode is a metal zinc sheet, which is processed according to the method of Example 10.

[0072] The separators include polyolefin separator Celgard 3501 and glass fiber separator Whatman GF / A.

[0073] The positive electrode current collector, negative electrode, electrolyte and separator were assembled into a button battery according to the method of Example 10, and the electrical performance was tested.

[0074] Embodiments 14 to 16 It is basically the same as Example 13, except that Examples 14 to 16 respectively use the electrolyte described in Examples 2 to 4.

[0075] Comparative Example 1 It is basically the same as Example 13, except that methylene blue is not added to the electrolyte.

[0076] The specific preparation process includes: (1) Preparation of positive electrode current collector: 45 mg of carboxylated multi-walled carbon nanotubes (MWCNTs) and 5 mg of carboxylated single-walled carbon nanotubes (SWCNTs) were dispersed in 50 mL of isopropanol and subjected to strong ultrasonic treatment for 10 minutes. Subsequently, the resulting mixture was reacted under stirring conditions for 24 hours, after which it was filtered and washed with ethanol. The resulting filter cake was dried at 60 ° C for 30 minutes, and finally a carbon nanotube film was prepared as the positive electrode current collector.

[0077] (2) Preparation of electrolyte: 27.26 g zinc chloride and 9.57 g zinc iodide were dissolved in 10 mL deionized water to prepare a zinc-iodine electrolyte (referred to as BI electrolyte) consisting of 20 M ZnCl2 and 3 M ZnI2.

[0078] (3) Preparation of zinc negative electrode: The zinc sheet negative electrode needs to be polished with 2000-grit sandpaper before use. After polishing for 20 minutes, it is polished with 0.3 mm and 0.05 mm alumina polishing powder and anhydrous ethanol respectively. It is then ultrasonically cleaned in a mixed solution of acetone, deionized water and isopropanol (acetone, deionized water and isopropanol volume ratio 1:1:1), dried at room temperature and punched into discs with a diameter of 12 mm.

[0079] (4) Assembly of zinc-iodine battery: The battery shell model is CR2032, the glass fiber separator model is Whatman GF / A, and the polyolefin separator model is Celgard 3501. The battery is assembled in the following order: positive electrode shell-19 mm titanium sheet-silicone gasket (outer diameter 19 mm, inner diameter 8 mm, thickness 0.2 mm)-carbon nanotube film (diameter 8 mm, thickness 80 μm)-polyolefin separator-BI electrolyte-glass fiber separator-zinc negative electrode (diameter 12 mm)-16 mm titanium sheet-gasket-spring-negative electrode shell, and then the battery is sealed using a tablet press. During the assembly process, avoid contact between the tweezers and the positive and negative electrodes to cause a short circuit.

[0080] Electrochemical performance test: The zinc-iodine batteries with different concentrations of methylene blue in Examples 13 to 16 were tested at 0.5 to 1.4 V to study the effects of different concentrations of methylene blue on the performance of zinc-iodine batteries. Self-discharge tests and long cycle tests were performed on the two different zinc-iodine batteries in Example 13 and Comparative Example 1 at 0.5 to 1.4 V, and the changes in the polyiodide concentration during the battery charge and discharge process were observed by in-situ Raman and in-situ optical microscopy. The results are as follows: Figures 2 to 6 shown.

[0081] from Figure 2 It can be seen that in Examples 13 to 16, when the concentrations of zinc salt and iodine salt are the same, the concentration of methylene blue has a great influence on the capacity of the zinc-iodine battery. -2 At a low current density of 1.5 M, the cell area capacity of 0.1 M methylene blue was as high as 2.58 mAh cm -2 The capacity of zinc-iodine batteries using other concentrations of methylene blue is far worse than 0.1 M, which indicates that the concentration of methylene blue cannot be too high (aggravated side reactions) or too low (insufficient catalytic mediation).

[0082] from Figure 3 It can be seen that the capacity retention rate of the zinc-iodine battery using BI electrolyte in comparative example 1 after being fully charged and standing for 12 hours is 54.2%, and the capacity retention rate of the zinc-iodine battery using MBI electrolyte in example 13 after being fully charged and standing for 12 hours reaches 72.3%. Therefore, compared with the zinc-iodine battery using BI electrolyte, the zinc-iodine battery using MBI electrolyte has a higher capacity retention rate after being fully charged and standing for 12 hours, that is, the zinc-iodine battery using MBI electrolyte in example 13 has higher stability.

[0083] from Figure 4 It can be seen that the zinc-iodine battery using MBI electrolyte in Example 13 has a high -2 The areal capacity is as high as 1.51 mAh cm at high current density. -2 , while the zinc-iodine battery using BI electrolyte in comparative example 1 was -2 The areal capacity is only 1.08 mAh cm at a high current density. -2 , indicating that the use of the MBI electrolyte of the present invention can increase the zinc-iodine capacity of the battery by 40%.

[0084] from Figure 5 and Figure 6 It can be seen that compared with the zinc-iodine battery based on BI electrolyte, the zinc-iodine battery of Example 13 effectively inhibits the dissolution and diffusion of polyiodides due to the addition of methylene blue. Because of this, the cycle stability of the zinc-iodine battery based on MBI electrolyte is significantly improved and the capacity is increased.

Claims

1. A phenothiazine type zinc-iodine battery electrolyte, characterized in that: include: Soluble zinc salt, soluble iodine salt, methylene blue and water.

2. The phenothiazine zinc-iodine battery electrolyte according to claim 1, characterized in that: The zinc salt is one of zinc chloride, zinc sulfate, zinc perchlorate and zinc acetate.

3. The phenothiazine type zinc-iodine battery electrolyte according to claim 1, characterized in that: The iodized salt is zinc iodide.

4. The phenothiazine zinc-iodine battery electrolyte according to claim 1, characterized in that: The concentration of methylene blue is 0.02~0.2 M.

5. The phenothiazine type zinc-iodine battery electrolyte according to claim 1, characterized in that: The concentration of zinc salt is 15~25M, and the concentration of iodized salt is 1.0~5.0M.

6. A zinc-iodine battery, characterized in that: The invention comprises a positive electrode current collector, a negative electrode and an electrolyte, wherein the electrolyte is located between the positive electrode current collector and the negative electrode, and the electrolyte is the phenothiazine type zinc-iodine battery electrolyte according to any one of claims 1 to 5.

7. The zinc-iodine battery according to claim 6, characterized in that: The positive electrode current collector is a carbon nanotube film.

8. The zinc-iodine battery according to claim 7, characterized in that: The carbon nanotube film is a carbon nanotube film formed by combining multi-walled carbon nanotubes and single-walled carbon nanotubes.

9. The zinc-iodine battery according to claim 6, characterized in that: It also includes a first separator and a second separator. The first separator is located between the positive electrode collector and the electrolyte, and the second separator is located between the electrolyte and the negative electrode. The first separator is a polyolefin separator, and the second separator is a glass fiber separator.

10. Application of methylene blue as an additive in zinc-iodine battery electrolyte or zinc-iodine battery.

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