Zinc-iodine battery positive electrode and preparation method thereof

Abstract

The invention provides a zinc-iodine battery positive electrode and a preparation method thereof, and the preparation method comprises the following steps: mixing a carbon-iodine composite material, a conductive agent, a thickening agent and a binder to obtain first slurry; mixing mesoporous carbon / microporous carbon, a conductive agent, a thickening agent and a binder to obtain second slurry; coating the surface of a current collector with the first slurry to form a first active material layer; coating the second slurry on the surface of the first active material layer, and drying to complete the preparation of the zinc-iodine battery positive electrode; according to the invention, dissolution of iodine is efficiently inhibited by virtue of a double-layer synergistic effect; mesoporous carbon in the carbon-iodine composite material has a developed pore structure and an extremely high specific surface area, so that iodine molecules can be effectively adsorbed and wrapped in pore channels, and dissolution is prevented; the covering effect of the second active substance layer further forms a physical barrier for dissolution of iodine; in addition, the surface of the mesoporous / microporous carbon is rich in oxygen-containing functional groups, and the oxygen-containing functional groups and iodine molecules entering the electrolyte can form chemical bonds, so that iodide ions are further recovered.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous energy storage, and in particular to a zinc-iodine battery positive electrode and a preparation method thereof. Background Art

[0002] In the context of global energy transformation, energy storage technology is the core of building a new power system. Although lithium-ion batteries are widely used, their resource limitations, safety risks, and environmental impacts have made aqueous batteries a potential alternative. Aqueous zinc-iodine batteries have advantages such as high theoretical capacity (211 mAh / g), low cost, and environmental friendliness, but they face the following problems: iodine and iodide have poor conductivity (10 -6 S cm -1 ~10 -9 S cm -1 ), resulting in low electrode reaction activity; polyiodide is easily dissolved and undergoes shuttle effect during the cycle, causing loss of active substances and self-discharge; the traditional carbon-iodine composite electrode preparation method easily leads to uneven iodine distribution and cannot effectively inhibit the diffusion of polyiodide ions.

[0003] Although existing technologies have alleviated these issues by adsorbing iodine on porous carbon materials, the iodine loading capacity is limited, and heat treatment can easily lead to iodine volatilization and loss. Therefore, a cathode preparation method that can improve iodine utilization, inhibit the shuttle effect, and improve cycle stability is urgently needed. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the present invention provides a zinc-iodine battery positive electrode and a preparation method thereof. The specific invention contents are as follows: In a first aspect, the present invention provides a method for preparing a positive electrode of a zinc-iodine battery, the preparation method comprising: The carbon-iodine composite material, the conductive agent, the thickener and the binder are mixed and homogenized to obtain a first slurry; the mesoporous carbon / microporous carbon, the conductive agent, the thickener and the binder are mixed and homogenized to obtain a second slurry; Applying the first slurry on the surface of the current collector, and forming a first active material layer on the surface of the current collector after drying; The second slurry is then coated on the surface of the first active material layer. After drying, a second active material layer is formed on the surface of the first active material layer, and the preparation of the zinc-iodine battery positive electrode is completed.

[0005] Optionally, the carbon-iodine composite material is formed by combining mesoporous carbon and iodine; The carbon-iodine ratio in the carbon-iodine composite material is 1:0.2-1.5.

[0006] Optionally, the carbon-iodine composite material is prepared by an ethanol adsorption method, a water adsorption method or a steam method.

[0007] Optionally, the conductive agent is one or more of carbon black (SP), acetylene black, graphene, and carbon nanotubes; The thickener is carboxymethyl cellulose; The binder is styrene-butadiene rubber.

[0008] Optionally, the mass ratio of the carbon-iodine composite material, the conductive agent, the thickener and the binder is 7-11:0.5-1.5:1:1.

[0009] Optionally, the solid content of the second slurry is 5% to 20%, and the mass ratio of the mesoporous carbon / microporous carbon, the conductive agent, the thickener and the binder is 7-11:0.5-1.5:1:1.

[0010] Optionally, the specific surface area of ​​the mesoporous carbon is 1923-2210 m 2 / g, mesopore volume is 0.4~0.43 cc / g, micropore volume is 0.59~0.64 cc / g, total pore volume is 0.99~1.07 cc / g, and mesoporosity is 35~50%; The specific surface area of ​​the microporous carbon is 1517-1700m 2 / g, the micropore volume is 0.52~0.56 cc / g, the mesopore volume is 0.19~0.21 cc / g, the total pore volume is 0.71~0.77 cc / g, and the mesoporosity is 25-35%.

[0011] Optionally, the coating thickness of the second slurry is smaller than the coating thickness of the first slurry.

[0012] Optionally, the current collector is a Ti foil current collector.

[0013] In a second aspect, the present invention provides a zinc-iodine battery positive electrode obtained by the preparation method described in the first aspect.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention provides a method for preparing a positive electrode of a zinc-iodine battery, which comprises: mixing a carbon-iodine composite material, a conductive agent, a thickener and a binder, and then homogenizing the mixture to obtain a first slurry; mixing mesoporous carbon / microporous carbon, a conductive agent, a thickener and a binder, and then homogenizing the mixture to obtain a second slurry; coating the first slurry on the surface of a current collector, and forming a first active material layer on the surface of the current collector after drying; continuously coating the second slurry on the surface of the first active material layer, and forming a second active material layer on the surface of the first active material layer after drying, thereby completing the preparation of the positive electrode of the zinc-iodine battery.

[0015] In the preparation method provided by the present invention, the mesoporous carbon selected by the present invention (specific surface area of ​​1923-2210 m2 / g, mesopore volume of 0.4-0.43 cc / g, micropore volume of 0.59-0.64 cc / g, total pore volume of 0.99-1.07 cc / g, mesoporosity of 35-50%) and microporous carbon (specific surface area of ​​1517-1700 m 2 / g, micropore volume is 0.52~0.56 cc / g, mesopore volume is 0.19~0.21 cc / g, total pore volume is 0.71~0.77 cc / g, and mesoporosity is 25-35 %) has a developed pore structure and an extremely high specific surface area. The carbon-iodine composite material in the first active material layer (carbon-iodine composite layer) fixes iodine by physical adsorption and chemical bonding. The mesoporous carbon therein effectively "wraps" the iodine molecules (I2 or I⁻) inside the pores by physical adsorption, forming a structure similar to a "molecular cage"; the oxygen-containing functional groups (such as hydroxyl groups, carboxyl groups, etc.) rich in the surface of the mesoporous carbon can form chemical bonds with iodine molecules to reduce the dissolution of iodine; the second active material layer acts as a barrier, covering the surface of the first active material layer to form a physical barrier to further block the migration of dissolved iodine into the electrolyte, and the surface of the mesoporous / microporous carbon in the second active material layer is rich in oxygen-containing functional groups, which can form chemical bonds (such as CI bonds or hydrogen bonds) with iodine molecules entering the electrolyte to further recover iodide ions; efficient dissolution inhibition is achieved through the synergistic effect of the double layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A flow chart of a method for preparing a positive electrode sheet for a zinc-iodine battery provided in an embodiment of the present invention is shown; Figure 2 The figures show the capacity of the zinc-iodine batteries provided in Example 1 and Comparative Example 2 at different rates. Figure 3 The figures show the capacities of other zinc-iodine batteries provided in Example 2 of the present invention and Comparative Example 2 at different rates; Figure 4 The figures show the capacities of other zinc-iodine batteries provided in Examples 3 and 4 of the present invention and Comparative Example 3 at different rates; Figure 5 The figures show the capacity of other zinc-iodine batteries provided in Examples 5 and 6 of the present invention and Comparative Example 4 at different cycle times; Figure 6The figure shows the capacity of the zinc-iodine battery provided in Comparative Example 1 of the present invention at different rates; Figure 7 A graph showing the relationship between the capacity difference and rate of other zinc-iodine batteries provided in Examples 3 and 4 of the present invention and Comparative Example 3, obtained by taking the 1C average capacity as a standard; Figure 8 The figures show the capacity of other zinc-iodine batteries provided in Examples 3 and 4 of the present invention and Comparative Example 3 at different cycle times; Figure 9 The figures show the capacities of other zinc-iodine batteries provided in Examples 7, 8, and 9 of the present invention and Comparative Example 5 at different cycle times. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product that is identical or similar to the present invention and is obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work fall within the scope of protection of the present invention.

[0019] Where specific experimental steps or conditions are not specified in the examples, the conventional experimental steps or conditions described in the prior art in the art may be used. Reagents and other instruments used, for which the manufacturer is not specified, are commercially available conventional reagent products. Furthermore, the accompanying drawings are merely schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. Identical reference numerals in the figures denote identical or similar parts, and their repeated descriptions will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0020] Technologies, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies, methods, and equipment should be considered part of the description of the present invention.

[0021] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Before describing in detail the zinc-iodine battery positive electrode and preparation method provided by the present invention, it is necessary to describe the related technologies as follows: In the global energy transition, energy storage technology, as a critical infrastructure supporting the operation of new power systems, plays a decisive role in maintaining grid stability and increasing renewable energy penetration. Lithium-ion batteries, with their excellent energy density and proven track record, have become the preferred energy storage technology. However, limitations such as resource constraints, price uncertainty, safety concerns, and environmental impacts are driving the search for new alternatives. Aqueous batteries are secondary batteries using water as the electrolyte. Compared to batteries with organic electrolytes, aqueous batteries offer advantages such as increased safety, environmental friendliness, and high ionic conductivity. Furthermore, their low-cost and widely available raw materials reduce over-reliance on specific mineral resources, aligning with sustainable development goals. More importantly, aqueous batteries have a lower environmental impact and demonstrate greater ecological compatibility, both in manufacturing and at end-of-life disposal, aligning with the globally advocated green transition path. However, current aqueous batteries generally have lower energy density than lithium batteries, limiting the amount of energy they can store per unit volume. Furthermore, they are limited by drawbacks such as a narrow window voltage, electrode side reactions, and poor cycling stability, resulting in limited practical applications.

[0023] Iodine has a theoretical specific capacity of 211 mAh / g and a relatively high discharge platform (about 1.38 V vs Zn / Zn 2+ ), which is compatible with aqueous zinc-based batteries. At the same time, iodine reserves are relatively abundant, with reserves of about 50-60 μg / L in seawater. Higher iodine reserves can help further reduce the cost of zinc-iodine batteries. Zinc-iodine batteries perfectly highlight the characteristics of aqueous batteries and are a high-energy-density, low-cost and environmentally friendly energy storage system. However, iodine and iodide have poor conductivity (about 10 −6 to 10 −9 S cm −1 ), the resistivity of elemental iodine reached 1.3×10 7 Ω m. The thermodynamic instability and high sublimation properties of iodine complicate large-scale electrode fabrication. Intermediate polyiodides formed during cycling readily dissolve in the electrolyte and diffuse between the cathode and anode (averaging shuttle effect) under varying concentrations, leading to active material loss, severe self-discharge, and low Coulombic efficiency (CE).

[0024] At present, one of the main solutions to the above-mentioned problems of the positive electrode of zinc-iodine batteries is to design auxiliary structures, among which porous carbon materials are the most commonly used. Carbon materials not only have good conductivity, which can enhance the conductivity of the cathode, but also have adsorption functions and confined hollow structures, which can capture or limit polyiodide on the positive electrode side. Common methods for preparing carbon-iodine composite electrode materials are: ① The porous carbon material and iodine are ball-milled and placed in a reactor. The reactor is then transferred to a forced-air drying oven. Utilizing the volatile nature of iodine, iodine vapor is allowed to fully penetrate the pores of the porous carbon material at 40-70°C. This temperature is maintained for 6-12 hours to yield a composite. The composite is removed from the reactor and spread flat on an evaporating dish. The dish is then placed in a vacuum drying oven and heated at 60°C for 4 hours to remove excess iodine from the surface, yielding a carbon-iodine composite material.

[0025] ② Pure iodine is dispersed in a solvent, and a certain proportion of carbon material is added to the solution, the weight ratio of iodine and carbon material is controlled, and then the solvent is removed by stirring and volatilization at 40-60°C to obtain a carbon-iodine composite material.

[0026] Both of the above methods first synthesize a porous carbon support and then load iodine. This results in the iodine being loaded on the carbon surface. Even in the process of increasing the iodine loading, the excess iodine cannot be completely removed and thus mixes with the carbon, resulting in the formation of polyiodide ions that cannot be restricted by the pore size or adsorbed by the pore structure, thus forming a shuttle effect. If heat treatment is performed, the mass of the iodine will be drastically reduced, resulting in a loss of battery capacity and waste of raw materials. It will also produce harmful iodine vapor, which limits the synthesis of high-iodine-loaded carbon materials and poor electrode electrochemical performance.

[0027] To address the above issues, the present invention provides a zinc-iodine battery positive electrode and preparation method. By providing a double-layer active material layer, a carbon-iodine composite material is distributed in a gradient on the electrode surface. Iodine is directly fixed by the first active material layer (carbon-iodine composite layer), and the second active material layer (porous carbon layer) acts as a protective layer to further block iodine diffusion. The synergistic effect of the double layers achieves efficient dissolution inhibition. The specific implementation content is as follows: In a first aspect, the present invention provides a method for preparing a positive electrode of a zinc-iodine battery. Figure 1 The flow chart of the preparation method of the positive electrode of the zinc-iodine battery provided by the present invention is shown as follows: Figure 1 As shown, the preparation method includes: S1, mixing the carbon-iodine composite material, a conductive agent, a thickener, and a binder, and homogenizing the mixture to obtain a first slurry; mixing the mesoporous carbon / microporous carbon, a conductive agent, a thickener, and a binder, and homogenizing the mixture to obtain a second slurry; In practice, the carbon-iodine composite material is formed by combining mesoporous carbon and iodine, and can be prepared by ethanol adsorption, water adsorption, or steam adsorption. In the first slurry, the weight ratio of the carbon-iodine composite material, conductive agent, thickener, and binder is 7-11:0.5-1.5:1:1; preferably, the weight ratio of the carbon-iodine composite material, conductive agent, thickener, and binder is 8:1:1:1.

[0028] In specific implementation, in the second slurry, the mass ratio of mesoporous carbon / microporous carbon, conductive agent, thickener and binder is 7-11:0.5-1.5:1:1. When the second layer is coated, the coating thickness is reduced relative to the coating thickness of the second slurry. When homogenizing, the solid content in the second slurry is controlled to be 5% to 20%; to ensure that the second layer of slurry can be evenly covered on the surface of the first layer of slurry; preferably, the mass ratio of mesoporous carbon / microporous carbon, conductive agent, thickener and binder is 8:1:1:1, and the solid content in the second slurry is controlled to be 5 to 20%.

[0029] In a specific implementation, the conductive agent constituting the first slurry and the second slurry is selected from one or more of carbon black (SP), acetylene black, graphene, and carbon nanotubes, the thickener is carboxymethyl cellulose (CMC), and the binder is styrene-butadiene rubber (SBR).

[0030] S2. applying the first slurry to the surface of the current collector, and forming a first active material layer on the surface of the current collector after drying; In practice, the current collector is made of Ti foil. Using a flatbed coater, the first slurry is applied to the surface of the Ti foil current collector. It should be noted that the coating thickness of the first slurry in this embodiment of the present invention is sufficient to meet practical application requirements, and there are no specific requirements for the solids content of the first slurry, as long as it meets the viscosity requirements for slurry coating. After coating, the slurry is transferred to a forced air drying oven and dried at 60-80°C for 50-10 minutes to form a first active material layer on the current collector surface.

[0031] S3. Continue to apply the second slurry on the surface of the first active material layer, form a second active material layer on the surface of the first active material layer after drying, and complete the preparation of the zinc-iodine battery positive electrode.

[0032] In specific implementation, the coating thickness of the second slurry should not be greater than the coating thickness of the first slurry. If the coating thickness of the second slurry is too high, the mesoporous carbon / microporous carbon content in the electrode material will be too high, causing consumption of the electrolyte and side reactions, affecting battery performance. After the second slurry is coated, it is transferred to a blast drying oven and dried at 60-80°C for 50-10 minutes to form a second active material layer on the surface of the current collector.

[0033] The present invention achieves efficient inhibition of iodine dissolution through double-layer synergistic effect; due to the mesoporous carbon selected in the present invention (specific surface area of ​​1923-2210 m 2 / g, mesopore volume of 0.4-0.43 cc / g, micropore volume of 0.59-0.64 cc / g, total pore volume of 0.99-1.07 cc / g, mesoporosity of 35-50%) and microporous carbon (specific surface area of ​​1517-1700 m 2 / g, micropore volume is 0.52~0.56 cc / g, mesopore volume is 0.19~0.21 cc / g, total pore volume is 0.71~0.77 cc / g, and mesoporosity is 25-35 %) has a developed pore structure and an extremely high specific surface area. The carbon-iodine composite material in the first active material layer (carbon-iodine composite layer) fixes iodine by physical adsorption and chemical bonding. The mesoporous carbon therein effectively "wraps" the iodine molecules (I2 or I⁻) inside the pores by physical adsorption, forming a structure similar to a "molecular cage"; the oxygen-containing functional groups (such as hydroxyl groups, carboxyl groups, etc.) rich in the surface of the mesoporous carbon can form chemical bonds with iodine molecules to reduce the dissolution of iodine; the second active material layer acts as a barrier, covering the surface of the first active material layer to form a physical barrier to further block the migration of dissolved iodine into the electrolyte, and the surface of the mesoporous / microporous carbon in the second active material layer is rich in oxygen-containing functional groups (such as hydroxyl groups, carboxyl groups, etc.), which can form chemical bonds (such as CI bonds or hydrogen bonds) with iodine molecules entering the electrolyte to further recover iodine ions.

[0034] In a second aspect, the present invention provides a zinc-iodine battery positive electrode obtained by the preparation method described in the first aspect.

[0035] In order to enable those skilled in the art to more clearly understand the present invention, the zinc-iodine battery positive electrode and the preparation method of the present invention are described in detail through the following examples.

[0036] Example 1 Preparation of carbon-iodine composite material by ethanol adsorption method: mesoporous carbon and elemental iodine were weighed in a ratio of 1:0.6, added to a beaker containing 20 ml of ethanol, sealed with plastic wrap and pierced, placed on a magnetic stirrer, and stirred at 60 °C overnight to obtain a carbon-iodine composite material. The specific surface area of ​​the mesoporous carbon used was 2211.59 m 2 / g, in the mesoporous carbon, the micropore volume is 0.62853 cc / g, the mesopore volume is 0.42477 cc / g, the total pore volume is 1.0533 cc / g, and the mesoporosity is 40.33%.

[0037] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a first slurry. The slurry is specifically composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0.

[0038] The mesoporous carbon was mixed with a conductive agent, a thickener, and a binder in specific proportions and homogenized to produce a second slurry. The slurry consisted of mesoporous carbon, carbon black (SP), CMC, and SBR in a mass ratio of 8.0:1.0:1.0:1.0, with a solids content of 16.5%.

[0039] The first slurry was applied to multiple sheets of 20μm Ti foil using a flatbed coater at a coating thickness of 200μm and a coating speed of 20 mm / s. The sheets were then transferred to a forced-air drying oven and dried at 60°C for 10 minutes before removal. The electrode sheets were fixed to the coater in the coating direction. The second slurry was applied to the surface of the first slurry layer at coating thicknesses of 50, 100, and 200μm, respectively, at a coating speed of 20 mm / s. The sheets were then transferred to a forced-air drying oven at 60°C until dry. The resulting zinc-iodine battery positive electrode sheets were designated E-1B06-M50, E-1B06-M100, and E-1B06-M200.

[0040] Example 2 The difference from Example 1 is that the carbon material used in the second slurry of this embodiment is microporous carbon, wherein the specific surface area of ​​the microporous carbon used is 1673.683 m 2 / The microporous carbon has a micropore volume of 0.5200 cc / g, a mesopore volume of 0.20118 cc / g, a total pore volume of 0.7212 cc / g, and a mesoporosity of 27.90%. The resulting zinc-iodine battery positive electrodes were named E-1B06-S50, E-1B06-S100, and E-1B06-S200.

[0041] Example 3 Steam method for preparing a carbon-iodine composite: Mesoporous carbon and elemental iodine were weighed in a ratio of 1:0.6, thoroughly ground in a mortar, and then transferred to a 100 ml reactor. The mixture was then placed in a 60°C forced air drying oven for 6 hours to obtain a composite. The composite was then removed from the reactor and spread flat on an evaporating dish. The dish was then placed in a vacuum drying oven and heated at 60°C for 4 hours to remove excess iodine from the surface. The mesoporous carbon used was the same as that used in Example 1.

[0042] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a first slurry. The slurry is specifically composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0.

[0043] Mesoporous carbon, a conductive agent, a thickener, and a binder are mixed and homogenized in a certain proportion to obtain a second slurry. The slurry is composed of mesoporous carbon, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0. The solid content of the second slurry is 16.5%.

[0044] The first slurry was applied to multiple sheets of 20 μm Ti foil using a flatbed coater at a coating thickness of 200 μm and a coating speed of 20 mm / s. The sheets were then transferred to a forced-air drying oven and dried at 60°C for 10 minutes before removal. The electrode sheets were fixed to the coater in the coating direction. The second slurry was applied to the surface of the first slurry layer at coating thicknesses of 50, 100, and 200 μm, respectively, at a coating speed of 20 mm / s. The sheets were then transferred to a forced-air drying oven at 60°C until dry. The resulting zinc-iodine battery positive electrode sheets were designated S-1B06-M50, S-1B06-M100, and S-1B06-M200.

[0045] Example 4 The difference from Example 3 is that the carbon material used in the second slurry of this example is microporous carbon, wherein the microporous carbon is the same as the microporous carbon used in Example 2. The resulting zinc-iodine battery positive electrode sheets are named S-1B06-S50, S-1B06-S100, and S-1B06-S200.

[0046] Example 5 Preparation of a carbon-iodine composite material by water adsorption: Mesoporous carbon and a standard iodine solution were added to a beaker at a carbon-iodine ratio of 1:0.6. The mixture was stirred at high speed on a magnetic stirrer for 30 minutes. The supernatant was removed by centrifuge, washed three times with deionized water, and dried naturally to obtain a carbon-iodine composite material. The mesoporous carbon was the same as that used in Example 1.

[0047] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a first slurry. The slurry is specifically composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0.

[0048] The mesoporous carbon was mixed with a conductive agent, a thickener, and a binder in a certain proportion and homogenized to obtain a second slurry. The slurry was composed of mesoporous carbon, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0, with a solids content of 16.5%.

[0049] The first slurry was applied to multiple sheets of 20μm Ti foil using a flatbed coater at a coating thickness of 200μm and a coating speed of 20 mm / s. The sheets were then transferred to a forced-air drying oven and dried at 60°C for 10 minutes before removal. The electrode sheets were fixed to the coater in the coating direction. The second slurry was applied to the surface of the first slurry layer at coating thicknesses of 50, 100, and 200μm at a coating speed of 20 mm / s. The sheets were then transferred to a forced-air drying oven at 60°C until dry. The resulting zinc-iodine battery positive electrode sheets were designated W-1B06-M50, W-1B06-M100, and W-1B06-M200.

[0050] Example 6 The difference from Example 5 is that the carbon material used in the second slurry of this example is microporous carbon, wherein the microporous carbon is the same as the microporous carbon used in Example 2. The obtained zinc-iodine battery positive electrode sheets are named W-1B06-S50, W-1B06-S100, and W-1B06-S200.

[0051] Example 7 Mesoporous carbon and standard iodine solution were added to a beaker at a carbon-iodine ratio of 1:1.3. The mixture was stirred at high speed on a magnetic stirrer for 30 minutes. The supernatant was removed by centrifuge, washed three times with deionized water, and dried naturally to obtain a carbon-iodine composite material. The mesoporous carbon was the same as that used in Example 1.

[0052] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a first slurry. The slurry is specifically composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), with a mass ratio of 8.0:1.0:1.0:1.0.

[0053] The mesoporous carbon was mixed with a conductive agent, a thickener, and a binder in a certain proportion and homogenized to obtain a second slurry. The slurry was composed of mesoporous carbon, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0, with a solids content of 16.5%.

[0054] The first slurry was applied to a 20 μm thick Ti foil using a flatbed coater at a coating thickness of 200 μm and a coating speed of 20 mm / s. The electrode was then transferred to a forced-air drying oven and dried at 60°C for 10 minutes. The electrode was then fixed to the coater in the coating direction. The second slurry was applied to the surface of the first slurry layer at a coating thickness of 50 μm and a coating speed of 20 mm / s. The electrode was then transferred to a forced-air drying oven at 60°C until dry. The resulting zinc-iodine battery positive electrode was designated W-1B13-15.

[0055] Example 8 The difference from Example 7 is that the solid content of the second slurry in this example is 11%, and all other conditions are the same. The resulting zinc-iodine battery positive electrode sheet is named W-1B13-10.

[0056] Example 9 The difference from Example 7 is that the solid content of the second slurry in this example is 5.5%, and the rest are the same. The obtained zinc-iodine battery positive electrode sheet is named W-1B13-05.

[0057] Comparative Example 1 Mesoporous carbon, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0 are mixed and homogenized to obtain a first slurry.

[0058] Microporous carbon and mesoporous carbon of the same mass were mixed and homogenized with a conductive agent, a thickener and a binder in a certain proportion to obtain two second slurries; one of the slurries had a solid content of 16.5%, and was specifically composed of mesoporous carbon, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0, wherein the mesoporous carbon was the same as that used in Example 1; the other slurry had a solid content of 16.5%, and was specifically composed of microporous carbon, carbon black (SP), CMC (mass fraction of 1.5%), and SBR in a mass ratio of 8.0:1.0:1.0:1.0, wherein the microporous carbon was the same as that used in Example 2.

[0059] The mesoporous carbon content in the first slurry layer in Example 3 was calculated using the carbon-iodine ratio. Subsequently, the coating thickness of the first slurry was adjusted and the first slurry was coated on multiple 20 μm Ti foils using a flatbed coater at a coating speed of 20 mm / s to obtain a pure carbon first slurry layer having the same carbon content as the first slurry layer prepared in Example 3. The second mesoporous carbon slurry was then applied to the surface of the first slurry layer at a coating thickness of 50, 100, and 200 μm, respectively, at a coating speed of 20 mm / s. The slurry was then transferred to a 60°C forced air drying oven until dry. The resulting zinc-iodine battery positive electrodes were named S-1B00-M50, S-1B00-M100, and S-1B00-M200. The second slurry containing microporous carbon was applied to the surface of the first slurry layer at a coating speed of 20 mm / s at a coating thickness of 50, 100, and 200 μm, respectively. The slurry was then transferred to a 60°C forced air drying oven to dry. The resulting zinc-iodine battery positive electrodes were named S-1B00-S50, S-1B00-S100, and S-1B00-S200.

[0060] The zinc-iodine battery positive electrode sheet containing only the first slurry layer is named S-1B00.

[0061] Comparative Example 2 Preparation of single-layer zinc-iodine battery positive electrode: Mesoporous carbon and elemental iodine were weighed in a ratio of 1:0.6 and added to a beaker containing 20 ml of ethanol. The mixture was sealed with plastic wrap and pierced with holes. The mixture was placed on a magnetic stirrer and stirred at 60°C overnight to obtain a carbon-iodine composite material. The mesoporous carbon was the same as that used in Example 1.

[0062] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a slurry. The slurry is composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0.

[0063] The slurry was applied to a 20 μm thick Ti foil using a flatbed coater at a coating speed of 20 mm / s to a thickness of 200 μm. The slurry was then transferred to a forced-air drying oven and dried at 60°C for 10 minutes to obtain a positive electrode. The resulting zinc-iodine battery positive electrode was designated E-1B06.

[0064] Comparative Example 3 Preparation of single-layer zinc-iodine battery positive electrode: Mesoporous carbon and elemental iodine were weighed in a ratio of 1:0.6, thoroughly ground in a mortar, and then transferred to a 100 ml reactor. The mixture was then placed in a 60°C forced air drying oven for 6 hours to obtain a composite. The composite was then removed from the reactor and spread flat on an evaporating dish. The evaporating dish was then placed in a vacuum drying oven and heated at 60°C for 4 hours to remove excess iodine from the surface. The mesoporous carbon used was the same as that used in Example 1.

[0065] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a slurry. The slurry is composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0.

[0066] The slurry was applied to a 20 μm thick Ti foil using a flatbed coater at a coating speed of 20 mm / s to a thickness of 200 μm. The slurry was then transferred to a forced-air drying oven and dried at 60°C for 10 minutes to obtain a positive electrode. The resulting zinc-iodine battery positive electrode was designated S-1B06.

[0067] Comparative Example 4 Preparation of single-layer zinc-iodine battery positive electrode: Mesoporous carbon and standard iodine solution were added to a beaker at a carbon-iodine ratio of 1:0.6. The mixture was stirred at high speed on a magnetic stirrer for 30 minutes. The supernatant was removed by centrifuge, washed three times with deionized water, and dried naturally to obtain a carbon-iodine composite material. The mesoporous carbon was the same as that used in Example 1.

[0068] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a slurry. The slurry is composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 8.0:1.0:1.0:1.0.

[0069] The slurry was applied to a 20 μm thick Ti foil using a flatbed coater at a coating speed of 20 mm / s to a thickness of 200 μm. The slurry was then transferred to a forced-air drying oven and dried at 60°C for 10 minutes to obtain a positive electrode. The resulting zinc-iodine battery positive electrode was designated W-1B06.

[0070] Comparative Example 5 Preparation of single-layer zinc-iodine battery positive electrode: Mesoporous carbon and standard iodine solution were added to a beaker at a carbon-iodine ratio of 1:1.3. The mixture was stirred at high speed on a magnetic stirrer for 30 minutes. The supernatant was removed by centrifuge, washed three times with deionized water, and dried naturally to obtain a carbon-iodine composite material. The mesoporous carbon was the same as that used in Example 1.

[0071] The carbon-iodine composite material, conductive agent, thickener, and binder are mixed and homogenized in a certain proportion to obtain a slurry. The slurry is specifically composed of the carbon-iodine composite material, carbon black (SP), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), with a mass ratio of 8.0:1.0:1.0:1.0.

[0072] The slurry was applied to a 20 μm thick Ti foil using a flatbed coater at a coating speed of 20 mm / s to a thickness of 200 μm. The slurry was then transferred to a forced-air drying oven and dried at 60°C for 10 minutes to obtain a positive electrode. The resulting zinc-iodine battery positive electrode was designated W-1B13.

[0073] Table 2 shows the parameters of the positive electrode sheets of zinc-iodine batteries provided in the examples and comparative examples: Table 2 Parameters of positive electrode sheets of zinc-iodine batteries in the examples and comparative examples

[0074] Performance testing: After the positive electrode sheets of Examples 1-9 and Comparative Examples 1-5 were prepared, they were assembled with the negative electrode sheets and separators into 2032 button-type batteries for rate testing and charge-discharge cycle testing. The rate testing procedure was as follows: first, discharge at 1C to the cutoff voltage, then cycle at 1C, 3C, 5C, 8C, 4C, and 1C for five cycles, for a total of 31 cycles. Each charge-discharge rate was followed by a 3-minute rest period. The charge-discharge cycle test primarily focused on the 1C rate.

[0075] Figure 2 The capacity of the zinc-iodine battery provided in Example 1 and Comparative Example 2 under different rates is shown; Figure 2 It can be seen that the capacity of the single-layer coated zinc-iodine battery E-1B06 provided in Comparative Example 2 at 1C (0.1039 mAh) is significantly lower than that of the three groups of zinc-iodine batteries E-1B06-M50 (0.16618 mAh), E-1B06-M100 (0.18242 mAh) and E-1B06-M200 (0.20101 mAh) provided in Example 1, and this phenomenon persists at other rates, indicating that the mesoporous carbon in the second active material layer has capacity contribution. After the 8C test, the battery test rate returned to 1C, and the capacity of E-1B06 (0.09033 mAh) decreased by 13.06% compared with the initial 1C capacity (0.1039 mAh). At this rate, the capacity of E-1B06-M50 decreased by 7.89%, the capacity of E-1B06-M100 decreased by 3.75%, and the capacity of E-1B06-M200 decreased by 3.33%. This is due to the recovery of escaped iodine ions by the mesoporous carbon in the second active material layer, which reduced capacity loss.

[0076] Figure 3 The capacity of other zinc-iodine batteries provided in Example 2 of the present invention and Comparative Example 2 at different rates is shown. Figure 3 It can be seen that the capacity of the single-layer coated zinc-iodine battery E-1B06 provided in Comparative Example 2 at different rates is significantly lower than that of the three groups of zinc-iodine batteries E-1B06-S50, E-1B06-S100 and E-1B06-S200 provided in Example 2, indicating that the microporous carbon in the second active material layer also has a capacity contribution. The three have different coating thicknesses, resulting in different contents of microporous carbon in the second active material layer, but the capacity contribution is not proportional to it. After the 8C test, the battery test rate returned to 1C, and the capacity of E-1B06 (0.09033 mAh) decreased by 13.06% compared to the initial 1C capacity (0.1039 mAh). At this rate, the capacity of E-1B06-S50 decreased by 6.46%, the capacity of E-1B06-S100 decreased by 5.46%, and the capacity of E-1B06-S200 decreased by 4.87%. It can be seen that microporous carbon also has a recovery effect on escaped iodine ions.

[0077] In order to verify the versatility of the double coating method, carbon-iodine composite materials were further synthesized by different preparation methods. Figure 4 The capacity of other zinc-iodine batteries provided in Examples 3, 4 and Comparative Example 3 of the present invention at different rates is shown. In the zinc-iodine batteries prepared in Examples 3, 4 and Comparative Example 3, the carbon-iodine composite materials are all prepared by steam method. From the results, regardless of whether the second active material layer is mesoporous carbon or microporous carbon, the capacity of the assembled battery is higher than that of the single-layer coated zinc-iodine battery S-1B06 provided in Comparative Example 3, and after the S-1B06 test is completed, the capacity decreases by 10.5%, which is also higher than 5.63% of S-1B06-M50, 4.73% of S-1B06-M100, 2.20% of S-1B06-M200, 5.14% of S-1B06-S50, 2.68% of S-1B06-S100 and 5.24% of S-1B06-S200; it can be seen that the capacity recovery effect of double-layer coating is also applicable to carbon-iodine composite materials prepared by steam method.

[0078] Figure 5 The capacity of other zinc-iodine batteries provided in Examples 5, 6 and Comparative Example 4 of the present invention at different rates is shown. In the zinc-iodine batteries prepared in Examples 5, 6 and Comparative Example 4, the carbon-iodine composite materials are all prepared by water adsorption. From the results, the mesoporous carbon and microporous carbon in the second active material layer still contribute to the capacity, but the difference is that W-1B06-M50 and W-1B06-S50 have the highest capacity at each rate, which is opposite to the mesoporous carbon content in the second active material layer. After the W-1B06 test was completed, the capacity decreased by 13.36%, which was also higher than that of other groups.

[0079] Figure 6 The capacity of the zinc-iodine battery provided in Comparative Example 1 of the present invention at different rates is shown. Figure 4 and Figure 6 From the comparison, it can be seen that Comparative Example 1 is a blank control experimental example of Examples 3 and 4 (does not contain iodine). With iodine content as the single variable, after excluding the capacity contribution of carbon materials, the iodine capacity of each group is close to the same, which shows that gradient coating does not affect the performance of iodine capacity. Figure 6 The capacity changes of each group at different rates were relatively low, indicating that Figure 4 The capacity changes of each group at different rates are mainly due to the capacity changes of iodine. Then, the relationship between capacity difference and rate is plotted and displayed on the graph based on the average capacity of each group at 1C. Figure 7 It can be found that the presence of the second active material layer reduces the capacity loss at high rates, and the second active material layer composed of mesoporous carbon has better effects than microporous carbon, which is due to the excellent pore structure in the mesoporous carbon.

[0080] Figure 8The capacity of other zinc-iodine batteries provided in Examples 3 and 4 of the present invention and Comparative Example 3 under different cycle times is shown. Figure 8 It can be seen that the zinc-iodine battery S-1B06 provided in Comparative Example 3 can operate stably for more than 800 cycles, while Examples 3 and 4 establish a second active material layer on the electrode through double-layer coating. The coating thickness of the second active material layer is inversely proportional to the cycle life. This may be due to excessive mesoporous carbon and microporous carbon, which aggravates the consumption of the electrolyte or enhances the side reaction.

[0081] The coating thickness of the second active material layer was set to be smaller than the coating thickness of the first slurry to further explore the effect of the mesoporous carbon / microporous carbon content in the second active material layer on the battery cycle life. Figure 9 The capacity of other zinc-iodine batteries provided in Examples 7, 8, 9 and Comparative Example 5 under different cycle times is shown. Figure 9 It can be seen that under high iodine loading, the single-layer coated zinc-iodine battery W-1B13 provided in Comparative Example 5 has a cycle life of only 200 cycles due to the shuttle effect of polyiodide ions. However, Examples 7, 8, and 9 were coated with three second slurries with different solid contents, each with a coating thickness of 50 μm. All of these contributed to increased capacity and extended cycle life of high iodine-loading batteries. This is due to the fact that the second active material layer helps to fully utilize the iodine capacity and can intercept the formed polyiodide ions during discharge, preventing them from forming a shuttle effect; during charging, it can recover the escaped polyiodide ions, preventing unnecessary loss of polyiodide ions.

[0082] Furthermore, a comparison of the cycle lifespans of W-1B13-15, W-1B13-10, and W-1B13-05 revealed that W-1B13-05 had a significantly lower cycle life than the other two. This suggests that the mesoporous carbon content in the second active material layer is too low, leading to insufficient recovery of polyiodide ions. Therefore, the solids content of the second slurry should not be too low, preferably not less than 5.5%.

[0083] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0084] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and components involved are not necessarily required for the present invention.

[0085] The above is a detailed introduction to a zinc-iodine battery positive electrode and a preparation method provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a zinc-iodine battery positive electrode, characterized in that: The preparation method comprises: The carbon-iodine composite material, the conductive agent, the thickener and the binder are mixed and homogenized to obtain a first slurry; the mesoporous carbon / microporous carbon, the conductive agent, the thickener and the binder are mixed and homogenized to obtain a second slurry; Applying the first slurry on the surface of the current collector, and forming a first active material layer on the surface of the current collector after drying; The second slurry is then coated on the surface of the first active material layer. After drying, a second active material layer is formed on the surface of the first active material layer, and the preparation of the zinc-iodine battery positive electrode is completed.

2. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, wherein The carbon-iodine composite material is formed by combining mesoporous carbon and iodine; The carbon-iodine ratio in the carbon-iodine composite material is 1:0.2-1.

5.

3. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, wherein The carbon-iodine composite material is prepared by an ethanol adsorption method, a water adsorption method or a steam method.

4. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, wherein The conductive agent is one or more of carbon black (SP), acetylene black, graphene, and carbon nanotubes; The thickener is carboxymethyl cellulose; The binder is styrene-butadiene rubber.

5. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, wherein The mass ratio of the carbon-iodine composite material, the conductive agent, the thickener and the binder is 7-11: 0.5-1.5：1：1。 6. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, wherein The solid content of the second slurry is 5% to 20%, and the mass ratio of the mesoporous carbon / microporous carbon, the conductive agent, the thickener and the binder is 7-11: 0.5-1.5：1：1。 7. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, wherein: The specific surface area of ​​the mesoporous carbon is 1923m 2 / g~2210 m 2 / g, mesopore volume is 0.4cc / g~0.43cc / g, micropore volume is 0.59cc / g~0.64cc / g, total pore volume is 0.99cc / g~1.07cc / g, and mesoporosity is 35%~50%; The specific surface area of ​​the microporous carbon is 1517-1700m 2 / g, the micropore volume is 0.52~0.56 cc / g, the mesopore volume is 0.19cc / g~0.21 cc / g, the total pore volume is 0.71cc / g~0.77 cc / g, and the mesoporosity is 25%-35%.

8. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, characterized in that: The coating thickness of the second slurry is smaller than the coating thickness of the first slurry.

9. The method for preparing the positive electrode of zinc-iodine battery according to claim 1, characterized in that: The current collector is a Ti foil current collector.

10. A zinc-iodine battery positive electrode obtained by the preparation method according to any one of claims 1 to 9.

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