Preparation method and application of I2 / ATP composite material

Abstract

The invention relates to the technical field of aqueous zinc-iodine battery positive electrode materials, and discloses a preparation method and application of an I2 / ATP composite material, and the preparation method comprises the following steps: (1) carrying out acid pickling stirring, freeze drying and uniform grinding on purified attapulgite to obtain acidified attapulgite; (2) carrying out heat treatment on the acidified attapulgite at 300-500 DEG C for 2-4 hours to obtain heat-treated attapulgite; and (3) uniformly grinding the heat-treated attapulgite and I2, adding a certain amount of deionized water, heating at 110-140 DEG C for 14-24 hours, cooling, centrifuging and drying to obtain the I2 / ATP composite material. The composite material prepared by the invention is applied to a positive electrode of an aqueous zinc-iodine battery, so that the battery has the advantages of high specific capacity, slow specific capacity attenuation, good battery stability and the like.

Description

Technical Field

[0001] The invention relates to the technical field of positive electrode materials for aqueous zinc-iodine batteries, and in particular to a preparation method and application of an I2 / ATP composite material. Background Art

[0002] As human society's demand for energy continues to grow, fossil energy is over-exploited and consumed, and the problem of energy shortage is becoming increasingly prominent. At the same time, serious environmental pollution problems are also coming, and the development of clean and renewable energy technologies is imminent. Lithium-ion batteries (LIBs) have the characteristics of high energy density, long cycle life, no memory effect, and wide operating temperature. They dominate the commercial secondary battery market and are widely used in electric vehicles, energy storage power stations, and electronic equipment. However, the safety hazards brought by flammable organic electrolytes and the cost issues caused by the scarcity of lithium resources have restricted their large-scale application. In recent years, aqueous zinc-ion batteries (AZIBs) have been widely used due to their low cost, environmental friendliness, abundant raw materials, and high theoretical specific capacity (820 mAh g -1 or 5854 mAh L -1 ), low overpotential and high volume energy density, and has become a research hotspot, and is considered to be a very promising energy source that can replace lithium-ion batteries.

[0003] Compared with non-aqueous lithium-ion batteries, aqueous rechargeable zinc-ion batteries are a promising alternative and have received increasing attention in the field of grid storage research. Its advantages are as follows: First, zinc is an element with abundant reserves on Earth, and zinc mine resources are distributed all over the world. Second, the electrolyte used in aqueous zinc-based batteries is a non-toxic, non-flammable aqueous electrolyte, which is safer. Third, the aqueous electrolyte and zinc negative electrode allow the battery to be assembled in an open environment, reducing the manufacturing cost of the battery. Compared with traditional intercalation-type positive electrode materials, the positive electrode of aqueous zinc-iodine batteries is iodine element, which is based on conversion reaction. During the charging and discharging process, the structure will not collapse due to the insertion and migration of zinc ions, and it has a high theoretical capacity (211 mAh / g). In addition, iodine resources are abundant (about 55 micrograms of iodine per liter of seawater), which is conducive to the long-term and large-scale application of zinc-iodine batteries.

[0004] In zinc-iodine batteries, the active material of the positive electrode is iodine, but single iodine is easy to sublime, which is not conducive to the preparation of electrodes. Therefore, other materials are usually needed as carriers to load iodine as the positive electrode material of the battery. For the iodine positive electrode, the biggest challenge is the shuttle effect of polyiodides. During the charging and discharging process of zinc-iodine batteries, water-soluble polyiodides will inevitably be produced. These polyiodides will migrate to the zinc negative electrode under the action of electric field and concentration gradient, react with it, cause zinc corrosion and self-discharge, and reduce the performance of the battery. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a method for preparing an I2 / ATP composite material and its application, wherein the heat-treated attapulgite (ATP) and iodine are simply heated to load iodine on ATP to obtain an I2 / ATP composite material. The composite material prepared by the present invention is applied to the positive electrode of an aqueous zinc-iodine battery, so that the battery has the advantages of high specific capacity, slow specific capacity decay, good battery stability, etc.

[0006] Technical solution: The present invention provides a method for preparing an I2 / ATP composite material, comprising the following steps: (1) Mixing attapulgite with an appropriate amount of deionized water, stirring, centrifuging and taking the surface layer to obtain purified attapulgite, acid-washing and stirring, freeze-drying, and grinding the mixture evenly to obtain acidified attapulgite; (2) heat treating the acidified attapulgite at 300-500° C. for 2-4 hours to obtain heat-treated attapulgite; (3) Grinding the heat-treated attapulgite and I2 evenly, adding a certain amount of deionized water, heating at 110-140°C for 14-24h, cooling, centrifuging, and drying to obtain an I2 / ATP composite material.

[0007] Furthermore, in step (1), the acid washing is specifically performed by placing the purified attapulgite in hydrochloric acid and stirring for 12-14 hours.

[0008] Furthermore, the concentration of the hydrochloric acid is 2-4 mol / L.

[0009] Furthermore, in step (3), the mass ratio of the heat-treated attapulgite to the I2 is 1:1-2.

[0010] Preferably, in step (3), the drying temperature is 30-35°C.

[0011] The present invention also provides an application of the I2 / ATP composite material prepared by any of the methods described above in an aqueous zinc-iodine battery, wherein the positive electrode of the aqueous zinc-iodine battery is a stainless steel foil coated with the I2 / ATP composite material.

[0012] Furthermore, the negative electrode of the aqueous zinc-iodine battery is zinc foil.

[0013] Furthermore, the diaphragm of the aqueous zinc-iodine battery is a GF / A type glass fiber diaphragm.

[0014] Furthermore, the electrolyte of the aqueous zinc-iodine battery is a solution of 2-4 M ZnSO4 or ZnCl2.

[0015] Beneficial effects: Compared with the prior art, the present invention uses simple hydrothermal and heat treatment to load iodine on ATP to synthesize I2 / ATP composite positive electrode materials. Attached clay is a layered chain structured hydrated magnesium-rich aluminum silicate clay mineral with a large specific surface area and strong adsorption, mechanical stability and thermal stability. After heat treatment, its specific surface area is greatly increased, the layered structure is expanded, and it has good adsorption performance. The increased ATP specific surface area and interlayer gap provide more adsorption sites for iodine. In addition, the large number of hydrophilic groups of attached clay are conducive to the migration of zinc iodine ions and inhibit the shuttle effect during the charge and discharge process of zinc-iodine batteries, which effectively improves the rate performance, long cycle performance and electrochemical performance of aqueous zinc-iodine batteries. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a color comparison diagram of the attapulgite before and after loading iodine in Example 1; Figure 2 CV diagram of the zinc-iodine battery assembled in the embodiment; Figure 3 This is the EIS diagram of the zinc-iodine battery assembled in the embodiment; Figure 4 Cycle diagram of the zinc-iodine battery assembled in this example. DETAILED DESCRIPTION

[0016] The present invention is described in detail below in conjunction with the embodiments.

[0017] Implementation 1: The concave clay was mixed with an appropriate amount of deionized water, stirred in a blender for 5 min, and the surface layer was centrifuged to obtain the purified ATP. After pickling with 2-4 mol / L hydrochloric acid and stirring for 12 h, the mixture was freeze-dried and ground evenly. The mixture was heated at 400 °C in a muffle furnace for 2 h. After cooling, 0.5 g of the heat-treated ATP and 0.5 g of I2 were ground in a mortar for 2 min, poured into 50 mL of deionized water, ultrasonicated for 10 min, placed in a sealed reactor, heated in an oven at 140 °C for 18 h, cooled to room temperature, and then centrifuged to obtain the reaction product. The product was dried in a vacuum oven at 30 °C for 12 h to obtain the I2 / ATP composite material. A stainless steel foil coated with the I2 / ATP composite material was used as the positive electrode, a zinc foil was used as the negative electrode, a glass fiber GF / A was used as the diaphragm, and a 2 M ZnSO4 aqueous solution was used as the electrolyte to assemble a 2032 type button zinc ion battery.

[0018] Implementation 2: The attapulgite was mixed with an appropriate amount of deionized water, stirred in a blender for 5 min, and the surface layer was centrifuged to obtain the purified ATP. After pickling with 2-4 mol / L hydrochloric acid and stirring for 12 h, it was freeze-dried and ground evenly. It was heated at 400°C in a muffle furnace for 2 h. After cooling, 0.5 g of the heat-treated ATP and 0.5 g of I2 were ground in a mortar for 2 min, poured into 50 mL of deionized water, ultrasonicated for 10 min, put into a closed reactor, heated in an oven at 140°C for 18 h, cooled to room temperature, and then centrifuged to obtain the reaction product. It was dried in a vacuum oven at 30°C for 12 h to obtain the I2 / ATP composite material. A stainless steel foil coated with the I2 / ATP composite material was used as the positive electrode, a zinc foil was used as the negative electrode, a glass fiber GF / A was used as the separator, and a 3 M ZnCl2 aqueous solution was used as the electrolyte to assemble a 2032 type button zinc ion battery.

[0019] Implementation 3: The concave clay was mixed with an appropriate amount of deionized water, stirred in a blender for 5 min, and the surface layer was centrifuged to obtain the purified ATP. After pickling with 2-4 mol / L hydrochloric acid and stirring for 12 h, it was freeze-dried and ground evenly. It was heated at 400°C in a muffle furnace for 2 h. After cooling, 0.5 g of the heat-treated ATP and 1 g of I2 were ground in a mortar for 2 min, poured into 50 mL of deionized water, ultrasonicated for 10 min, put into a closed reactor, heated in an oven at 140°C for 18 h, cooled to room temperature, and then centrifuged to obtain the reaction product. It was dried in a vacuum oven at 30°C for 12 h to obtain the I2 / ATP composite material. A stainless steel foil coated with the I2 / ATP composite material was used as the positive electrode, zinc foil as the negative electrode, glass fiber GF / A as the separator, and 3 M ZnCl2 aqueous solution as the electrolyte to assemble a 2032-type button zinc ion battery.

[0020] Comparative Example 1: The attapulgite was mixed with an appropriate amount of deionized water, stirred in a blender for 5 minutes, and the surface layer was centrifuged to obtain the purified ATP. After pickling with 2-4 mol / L hydrochloric acid and stirring for 12 hours, it was freeze-dried and ground evenly. It was heated at 400°C in a muffle furnace for 2 hours. After cooling, 0.5 g of the heat-treated ATP and 1 g of I2 were ground in a mortar for 2 minutes to obtain an I2 / ATP composite material. A stainless steel foil coated with the I2 / ATP composite material was used as the positive electrode, a zinc foil as the negative electrode, a glass fiber GF / A as the separator, and a 3 M ZnCl2 aqueous solution as the electrolyte to assemble a 2032 type button zinc ion battery.

[0021] Comparative Example 2: The concave clay was mixed with an appropriate amount of deionized water, stirred in a blender for 5 min, and the surface layer was centrifuged to obtain the purified ATP. 0.5 g ATP and 0.5 g I2 were ground in a mortar for 2 min, poured into 50 mL of deionized water, and ultrasonicated for 10 min before being placed in a sealed reactor. The product was heated in an oven at 140 °C for 18 h, cooled to room temperature, and then centrifuged to obtain the reaction product, which was dried in a vacuum oven at 30 °C for 12 h to obtain the I2 / ATP composite material. A stainless steel foil coated with the I2 / ATP composite material was used as the positive electrode, a zinc foil as the negative electrode, a glass fiber GF / A as the separator, and a 3 M ZnCl2 aqueous solution as the electrolyte to assemble a 2032-type button zinc ion battery. The specific surface area and performance comparison of ATP without acidification and heat treatment are shown in Table 1.

[0022]

[0023] Results Analysis Figure 1 This is a comparison chart of ATP before preparation and ATP after loading with iodine. From the figure, we can see the obvious difference between its state before and after. From the uniform change of color, we can see that iodine is evenly loaded in ATP, which means that the larger specific surface area and stronger adsorption capacity of ATP after heat treatment firmly adsorb iodine in its layer chain structure. Figure 2 The CV diagram of the zinc-iodine battery assembled in the embodiment shows that it has obvious redox peaks, one oxidation peak and one reduction peak, corresponding to the mutual conversion of iodine ions. From the comparison of the preparation of the materials in Example 1 and Comparative Example 1, the I2 / ATP composite material prepared by hydrothermal reaction has iodine that is very easy to sublimate. It reacts in the state of iodine vapor in a closed reactor for 12 hours, so that it is more fully and evenly adsorbed. However, the iodine in the ground I2 / ATP composite material is always in the air and is easy to sublimate. It is also not easy to grind evenly, resulting in the loss of iodine and cannot be fully adsorbed on the concave soil. Figure 4 The electrochemical performance of the zinc-iodine battery assembled with the I2 / ATP composite material prepared in Example 1 after 100 cycles at a current density of 0.5 A / g shows that it has a very high specific capacity, indicating that the layered chain structure of the attapulgite increased after heat treatment, as well as its adsorption capacity, can adsorb iodine ions very well and firmly fix them on ATP. The large number of hydrophilic groups of the attapulgite are conducive to the migration of zinc-iodine ions, inhibiting the shuttle effect during the charge and discharge process of the zinc-iodine battery, so that the battery can have a high specific capacity.

[0024] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an I2 / ATP composite material, characterized in that: The following steps are involved: (1) Mixing attapulgite with an appropriate amount of deionized water, stirring, and centrifuging to obtain a surface layer to obtain purified attapulgite; acid-washing the purified attapulgite, stirring, freeze-drying, and grinding to obtain acidified attapulgite; (2) heat treating the acidified attapulgite at 300-500° C. for 2-4 hours to obtain heat-treated attapulgite; (3) Grinding the heat-treated attapulgite and I2 evenly, adding a certain amount of deionized water, heating at 110-140°C for 14-24h, cooling, centrifuging, and drying to obtain an I2 / ATP composite material.

2. The method for preparing the I2 / ATP composite material according to claim 1, wherein: In step (1), the acid washing is specifically performed by placing the purified attapulgite in hydrochloric acid and stirring for 12-14 hours.

3. The method for preparing the I2 / ATP composite material according to claim 2, characterized in that: The concentration of the hydrochloric acid is 2-4 mol / L.

4. The method for preparing the I2 / ATP composite material according to claim 1, wherein: In step (3), the mass ratio of the heat-treated attapulgite to the I2 is 1:1-2.

5. The method for preparing the I2 / ATP composite material according to claim 1, wherein: In step (3), the drying temperature is 30-35°C.

6. Use of the I2 / ATP composite material prepared by the method according to any one of claims 1 to 5 in an aqueous zinc-iodine battery, characterized in that: The positive electrode of the aqueous zinc-iodine battery is a stainless steel foil coated with an I2 / ATP composite material.

7. The use of the I2 / ATP composite material in an aqueous zinc-iodine battery according to claim 6, characterized in that: The negative electrode of the aqueous zinc-iodine battery is zinc foil.

8. The use of the I2 / ATP composite material in an aqueous zinc-iodine battery according to claim 6, characterized in that: The diaphragm of the aqueous zinc-iodine battery is a GF / A type glass fiber diaphragm.

9. The use of the I2 / ATP composite material in an aqueous zinc-iodine battery according to claim 6, characterized in that: The electrolyte of the aqueous zinc-iodine battery is a 2-4 M ZnSO4 or ZnCl2 solution.

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