Diaphragm with negative charges and application of diaphragm in zinc-based halogen battery

Abstract

The invention belongs to the field of material chemistry, and relates to a negatively charged diaphragm and application thereof in a zinc-based halogen battery. The diaphragm is prepared by carrying out ultrasonic dispersion, vacuum filtration and drying on an organic polymer containing an anionic group, and has a negative charge surface and a porous structure. The high-load iodine positive electrode is prepared by coating a titanium mesh current collector with a specific material and electroplating iodine; and the zinc-iodine battery is formed by the high-load iodine positive electrode, a zinc sheet negative electrode and ZnSOelectrolyte. The diaphragm utilizes electrostatic repulsive force with multi-iodine anions to inhibit iodine shuttling, improve iodine loading capacity and battery energy density and enhance cycling stability, has good flexibility and high strength, and has a wide prospect in the field of flexible wearable electronic equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical materials, and in particular relates to a negatively charged diaphragm and application thereof in a zinc-based halogen battery. Background Art

[0002] The rapid development of flexible wearable electronic devices has put forward stringent requirements on energy storage batteries. Among various battery systems, flexible zinc-iodine batteries are highly anticipated due to the high energy density and fast reaction kinetics of iodine-based positive electrodes. Their aqueous electrolytes and non-toxic materials also ensure safety and biocompatibility. However, current flexible zinc-iodine batteries face many difficulties. On the one hand, insufficient iodine electrode loading makes it difficult to increase the energy density of the entire battery; on the other hand, traditional glass fiber separators have poor flexibility and mechanical strength, and cannot maintain stable performance during multiple bending and folding operations.

[0003] In addition, with the exploration of improving the energy density of batteries, the shuttling phenomenon of iodine active substances migrating to the electrolyte becomes more and more prominent when the iodine electrode load is increased. This not only reduces the Coulomb efficiency, but also causes serious self-discharge problems. Although many studies have tried to solve this problem, such as Qu's team using special electrolytes to inhibit the shuttling of polyiodide ions, Yang et al. adding substances to reduce the concentration of polyiodide ions, and Zhou et al. developing new diaphragms, there is still a lack of diaphragm materials that can meet the needs of high load and shuttling inhibition at the same time, and have both flexible and strong properties, which limits the further development of flexible zinc-iodine batteries. Summary of the invention

[0004] A method for preparing a negatively charged separator comprises the following steps: S1 disperses the organic polymer material containing anionic groups uniformly in water, performs ultrasonic treatment to ensure stable and uniform distribution, and the ultrasonic power is 900W, and then forms it by vacuum filtration with the help of intermolecular hydrogen bonds; S2 vacuum-dries the formed membrane at room temperature to obtain a porous membrane with a smooth surface and negative charge, which can be directly used in zinc-iodine batteries, wherein the concentration of the polymer in water is 0.4wt%.

[0005] The present invention also provides a method for preparing a high-loaded iodine positive electrode, comprising the following steps: S1: adding activated carbon, Ketjen black and polyvinylidene fluoride (PVDF) into an organic solvent NMP in a mass ratio of 7:2:1, so that the concentration in NMP is 50 mg / mL, and sealing and stirring at room temperature for 12 hours to obtain a uniform mixed slurry; S2: coating the slurry on a titanium mesh current collector by multiple scraping methods, and then drying at 80° C. until the organic solvent NMP is completely volatilized, and the carrier material loading after drying is about 12.4 mg / cm²; S3 uses a mixed solution of ZnI2 and KI as the electrolyte, and deposits iodine on the titanium mesh through a two-electrode constant current electroplating method. After the electroplating is completed, it is vacuum dried at room temperature to obtain a high-loaded iodine positive electrode. The iodine loading after drying is about 13.9 mg / cm², and the concentrations of the electrolyte ZnI2 and KI are both 0.5M.

[0006] The present invention also provides a zinc-iodine battery, comprising the negatively charged porous diaphragm according to claim 1 and the high-load iodine positive electrode according to claim 2, and also comprising a zinc sheet negative electrode and a 2MZnSO4 electrolyte.

[0007] Furthermore, the organic polymer material is a sustainable and low-cost anionic polymer, which enables the diaphragm to have good flexibility and high mechanical strength through intermolecular hydrogen bonding, and is used to inhibit the shuttling of polyiodine active substances.

[0008] Furthermore, the diaphragm has an electrostatic repulsion effect with polyiodine anions through surface charge regulation, thereby inhibiting the shuttling effect of electroactive substances and improving the cycle stability of the iodine positive electrode under high iodine loading conditions.

[0009] Furthermore, the diaphragm is a lightweight and high-strength negative charge functional diaphragm, which achieves high energy density at the whole battery level and meets the application requirements of zinc-based halogen batteries in the field of flexible wearable electronic devices.

[0010] Beneficial technical effects of the invention: The negatively charged membrane of the present invention utilizes the strong electrostatic repulsion with polyiodine anions to successfully prevent I3 - and I5 - Penetration of multiple iodides. Compared with traditional porous carbon materials that rely on spatial confined adsorption, this electrostatic effect can more firmly fix negatively charged halogen active substances. Experiments show that the iodine positive electrode using the diaphragm of the present invention can greatly increase its iodine loading, which is significantly improved compared to the traditional method, thus laying the foundation for realizing a high energy density zinc-iodine full battery. Since the shuttling of iodine active substances is effectively suppressed and the side reactions caused by the shuttling are reduced, the cycle stability of the battery is greatly enhanced. During multiple charge and discharge cycles, the battery capacity retention rate is significantly improved. For example, the battery in the embodiment has a cycle life far exceeding that of batteries assembled with traditional diaphragms at a certain current density. Based on specific organic polymer materials and preparation processes, the diaphragm has good flexibility and high mechanical strength due to intermolecular hydrogen bonding. In the frequent bending and folding operations of flexible wearable electronic devices, it can effectively prevent internal short circuits in the battery and maintain structural integrity. This feature enables the battery to better adapt to complex deformation environments, expands its application range in the field of flexible devices, and is superior to traditional functional diaphragms in terms of strength and flexibility, providing a more reliable energy storage solution for flexible wearable electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the negative charge separator of the present invention being used to inhibit the shuttling effect of polyiodine active substances.

[0012] Figure 2 The negative charge separator prepared in Example 1 is used to stabilize the iodine positive electrode and the zinc-iodine battery of Comparative Example 1, and the charge and discharge performance is compared at a current density of 3Ag-1.

[0013] Figure 3 The negative charge separator prepared in Example 2 is used to stabilize the high-load iodine positive electrode and the zinc-iodine battery of Comparative Example 2, and the charge and discharge performance is compared at a current density of 2Ag-1. DETAILED DESCRIPTION

[0014] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Example 1

[0015] like Figure 1-Figure 2 As shown, an organic polymer containing a negatively charged functional group is added to water and ultrasonically treated at 900W for 45 minutes to make it uniformly dispersed. An appropriate amount of the dispersion is taken for vacuum filtration, and the filtration pressure is controlled between 0.05-0.1MPa, so that the polymer material forms a film through hydrogen bonding, and the film thickness is about 0.2mm. Finally, it is dried at a vacuum degree of 0.08MPa for 12 hours to obtain a porous film with a smooth surface and a negative charge, which can be directly used as a diaphragm for zinc-iodine batteries.

[0016] To prepare the iodine positive electrode, activated carbon, Ketjen black and PVDF binder (mass ratio 7:2:1) were evenly dispersed in NMP organic solvent to a concentration of 50 mg / mL, and evenly coated on the titanium mesh current collector, and dried at 80°C until the solvent was completely volatilized. Subsequently, iodine was deposited on the host material by constant current electroplating, with an electroplating current density of 0.2 A / cm² and an electroplating time of 3 hours. After vacuum drying, a spare iodine positive electrode was obtained, with an iodine loading of about 4.5 mg / cm².

[0017] The prepared negative charge separator was used to assemble a zinc-iodine full battery, with zinc sheet as the negative electrode and 2MZnSO4 as the electrolyte. -1 The charge and discharge test was carried out under the current density, and the data was recorded by the blue electric tester. The test results showed that the battery capacity reached 121.1mAhg -1 , the cycle life exceeds 2500 times, the charge and discharge curve is smooth, and the voltage platform is stable, indicating that the battery has good charge and discharge performance and cycle stability.

[0018] Performance test: The prepared I2 positive electrode was used to assemble a zinc-iodine full battery, with zinc sheet as the negative electrode, 2MZnSO4 as the electrolyte, and a glass fiber separator. -1 The charge and discharge tests were carried out at the current density.

[0019] The test results show that the battery capacity is 104.3mAhg -1 , the cycle life is only 540 times. Compared with Example 1, its capacity is lower, the cycle life is significantly shortened, the charge and discharge curve fluctuates greatly, and the voltage platform drops rapidly, indicating that the glass fiber separator is far inferior to the negatively charged separator of the present invention in inhibiting iodine shuttle and maintaining battery performance. Example 2

[0020] like Figure 3 As shown, an organic polymer containing a negatively charged functional group is added to water and treated with 900W ultrasound for 60 minutes to make it uniformly dispersed. An appropriate amount of the dispersion is taken for vacuum filtration, and the filtration pressure is controlled at 0.08-0.12MPa to form a hydrogen-bonded film between molecules with a thickness of about 0.25mm. Finally, it is dried at a vacuum degree of 0.1MPa for 15 hours to obtain a smooth surface with a negative charge porous membrane, which is used as a diaphragm for zinc-iodine batteries.

[0021] To prepare a high-load iodine positive electrode, activated carbon, Ketjen black and PVDF binder (mass ratio 7:2:1) were uniformly dispersed in NMP organic solvent, coated on a titanium mesh current collector, and dried at 80°C until the solvent was completely volatilized. Subsequently, iodine was deposited on the host material by constant current electroplating, with an electroplating current density of 0.3A / cm² and an electroplating time of 4 hours. After vacuum drying, it was used for standby use, and the iodine loading was about 13.9mg / cm².

[0022] The prepared negatively charged porous membrane and high-load I2 positive electrode were used to assemble a zinc-iodine full battery, with zinc sheet as the negative electrode and 2MZnSO4 as the electrolyte. -1 The charge and discharge tests were carried out at a current density of .

[0023] The test results show that the battery capacity is 158.3mAhg -1 , the cycle life reaches 550 times. The charge-discharge curve shows a higher capacity platform and smaller polarization, indicating that under the condition of high iodine positive electrode load, the separator of the present invention can still effectively inhibit iodine shuttle and maintain good battery performance.

[0024] The prepared high-load I2 positive electrode was used to assemble a zinc-iodine full battery, in which the zinc sheet was the negative electrode, 2MZnSO4 was the electrolyte, and the glass fiber was the separator. -1 The charge and discharge tests were carried out at the current density.

[0025] The assembled zinc-iodine full battery at 2Ag-1 The capacity at the current density is 116.1 mAh g -1 , the battery life is 44 cycles. Compared with Example 2, its capacity and cycle life are greatly reduced, which further proves the key role of the negatively charged separator of the present invention in improving battery performance when used in high-load iodine positive electrode.

Claims

1. A method for preparing a negatively charged separator, characterized in that: The following steps are involved: S1 disperses the organic polymer material containing anionic groups uniformly in water, performs ultrasonic treatment to ensure stable and uniform distribution, and the ultrasonic power is 900W, and then forms it by vacuum filtration with the help of intermolecular hydrogen bonds; S2 vacuum-dries the formed membrane at room temperature to obtain a porous membrane with a smooth surface and negative charge, which can be directly used in zinc-iodine batteries, wherein the concentration of the polymer in water is 0.4wt%.

2. A method for preparing a high-loaded iodine positive electrode, characterized in that: The following steps are involved: S1: adding activated carbon, Ketjen black and polyvinylidene fluoride (PVDF) into an organic solvent NMP in a mass ratio of 7:2:1, so that the concentration in NMP is 50 mg / mL, and sealing and stirring at room temperature for 12 hours to obtain a uniform mixed slurry; S2: coating the slurry on a titanium mesh current collector by multiple scraping methods, and then drying at 80° C. until the organic solvent NMP is completely volatilized, and the carrier material loading after drying is about 12.4 mg / cm²; S3 uses a mixed solution of ZnI2 and KI as the electrolyte, and deposits iodine on the titanium mesh through a two-electrode constant current electroplating method. After the electroplating is completed, it is vacuum dried at room temperature to obtain a high-loaded iodine positive electrode. The iodine loading after drying is about 13.9 mg / cm², and the concentrations of the electrolyte ZnI2 and KI are both 0.5M.

3. A zinc-iodine battery, characterized in that: It comprises a negatively charged porous diaphragm prepared by the method of claim 1 and a high-loaded iodine positive electrode prepared by the method of claim 2, and also comprises a zinc sheet negative electrode and a 2MZnSO4 electrolyte.

4. The method for preparing a negatively charged separator according to claim 1, characterized in that: The organic polymer material is a sustainable and low-cost anionic polymer, which enables the diaphragm to have good flexibility and high mechanical strength through the action of intermolecular hydrogen bonds and is used to inhibit the shuttling of polyiodine active substances.

5. The method for preparing a negatively charged separator according to claim 1, characterized in that: The diaphragm has an electrostatic repulsion effect with polyiodine anions through surface charge regulation, thereby suppressing the shuttling effect of electroactive substances and improving the cycle stability of the iodine positive electrode under high iodine loading conditions.

6. The method for preparing a negatively charged separator according to claim 1, characterized in that: The diaphragm is a lightweight and high-strength negative charge functional diaphragm, which achieves high energy density at the whole battery level and meets the application requirements of zinc-based halogen batteries in the field of flexible wearable electronic devices.

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