Preparation and application of halogen electrolyte additive for aqueous zinc ion battery

Abstract

The invention belongs to the technical field of energy storage of aqueous zinc ion batteries, and particularly relates to preparation and application of an aqueous zinc ion battery halogen electrolyte additive. On one hand, the electrolyte additive with iodide ions is adopted to mix different aqueous zinc ion battery electrolytes, and generation of zinc dendrites is effectively inhibited, so that the cycle life of the aqueous zinc ion battery is prolonged, and the battery performance is improved; on the other hand, the manganese dioxide positive electrode material is combined to form the total battery, the bromide ions and the manganese dioxide positive electrode material are coupled, and the capacity of the total battery is improved. In addition, the halogen electrolyte additive used in the invention is low in concentration, so that the cost is reduced on the premise of ensuring that the performance is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage of aqueous zinc-ion batteries, and particularly relates to the preparation and application of halogen electrolyte additives for aqueous zinc-ion batteries. Background Art

[0002] Lithium is considered to be the most promising anode for lithium-ion batteries due to its high energy density. However, the growth of lithium dendrites hinders the development of lithium-ion batteries because the presence of lithium dendrites may cause short-circuit problems, leading to fatal safety hazards such as fires and explosions. Therefore, there is an urgent need to develop a new generation of energy storage devices to replace it.

[0003] Aqueous zinc-ion batteries (AZIBs) have received extensive attention in the energy storage field due to their low cost, high safety, environmental friendliness, etc. AZIBs have unique advantages, such as high theoretical capacity (820 mAh·g -1 , 5855 mAh·cm -3 ), low redox potential (0.76 V, compared with the standard hydrogen electrode), high abundance (300 times higher than lithium), and good stability, which greatly expands the available range of electrolytes.

[0004] As an important part of AZIBs, the electrolyte can provide a migration channel for zinc ions to connect the positive and negative electrodes, and ensure the electrochemical stability window, the reversible plating / stripping process of zinc ions, and the ionic conductivity. At the same time, the selection of the electrolyte is crucial for the correct evaluation of electrode materials to obtain excellent electrochemical performance. Among them, zinc sulfate is often used as the electrolyte for AZIBs due to its excellent stability and compatibility with the electrodes. However, traditional zinc sulfate electrolyte batteries have poor Coulomb efficiency and rapid capacity decline due to the dissolution of the positive electrode material and the occurrence of irreversible side reactions, and the problem of zinc dendrite growth piercing the separator causing short circuits. By introducing additive ions into the traditional zinc sulfate electrolyte, the modification of the electrolyte can be realized, thereby prolonging the cycle life of the battery and obtaining more excellent electrochemical performance.

[0005] Halogens, also known as Group VIIA elements, mainly consist of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Since fluorine and chlorine exist in the form of gases at room temperature, and astatine is a radioactive element, its application in battery systems is quite difficult. Therefore, bromine and iodine are the main elements that can be used in energy storage systems, and they have rich reserves in the ocean and a very wide source. Therefore, if an electrolyte additive for aqueous zinc-ion batteries can be developed using bromine and iodine, it is expected to overcome the current deficiencies of traditional zinc sulfate electrolyte batteries. Summary of the Invention

[0006] To overcome the deficiencies of the above-mentioned existing technologies, the present invention proposes an aqueous solution additive with halogen ions for aqueous zinc-ion batteries. By mixing different electrolytes with halogen ion additives, it can promote uniform zinc deposition, effectively inhibit the formation of zinc dendrites, and avoid the problem of short circuit caused by its piercing the battery separator, thereby improving the cycle life and performance of the battery. And the halogen ions are added at a low concentration, and their reserves in seawater are abundant and easy to extract, greatly reducing the manufacturing cost of the battery.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides the application of a halogen ion electrolyte additive in an aqueous zinc-ion battery, and the halogen ion electrolyte additive is zinc iodide or zinc bromide.

[0009] The present invention has found through research that after introducing iodine into the aqueous zinc-ion battery, the strong adsorption of iodide ions on the zinc surface can induce zinc ion deposition by reducing the desolvation energy of the by-product [Zn(H 2 O) 6 2+ , thus realizing uniform zinc deposition and fast zinc deposition kinetics, reducing the formation of zinc dendrites, and improving the cycle life and performance of the battery; after introducing bromine into the aqueous zinc-ion battery, since the potential of bromine is close to that of manganese dioxide, it can be coupled with the manganese dioxide positive electrode material to provide capacity for the manganese dioxide positive electrode material, thereby improving the capacity of the zinc-manganese dioxide full battery. Therefore, on the one hand, the present invention uses an electrolyte additive with iodide ions to mix different aqueous zinc-ion battery electrolytes, effectively inhibiting the formation of zinc dendrites, thereby improving the cycle life and battery performance of the aqueous zinc-ion battery; on the other hand, it combines with the manganese dioxide positive electrode material to form a full battery, couples the bromide ions with the manganese dioxide positive electrode material, and improves the capacity of the full battery. In addition, the halogen electrolyte additive used in the present invention is at a low concentration, which reduces the cost while ensuring a large improvement in performance.

[0010] Preferably, the electrolyte is an aqueous solution of zinc salt, and the concentration of the zinc salt is 1-3 mol / L.

[0011] Preferably, the concentration of the halogen ions in the electrolyte is 0.01-0.03 mol / L.

[0012] Preferably, the aqueous zinc-ion battery includes a zinc-zinc symmetric battery and a zinc-manganese dioxide full battery.

[0013] The second aspect of the present invention provides a zinc-manganese dioxide full battery, and the zinc-manganese dioxide full battery uses zinc bromide as an electrolyte additive and α-MnO 2 ​As a positive electrode material. An electrolyte with a halogen ion additive is coupled with a manganese dioxide positive electrode material. By utilizing the characteristic that the halogen ion additive has a similar potential to manganese dioxide, the halogen ion provides capacity for the manganese dioxide positive electrode material, thereby improving the capacity of the full battery.

[0014] Preferably, the α-MnO 2 is prepared by dissolving manganese sulfate monohydrate, ammonium sulfate and ammonium persulfate in water, reacting by heating, and then performing suction filtration, washing and drying to obtain it.

[0015] Preferably, the temperature of the heating reaction is 100 - 150 °C, and the time is 10 - 15 h.

[0016] Preferably, the molar ratio of manganese sulfate monohydrate, ammonium sulfate and ammonium persulfate is 7 - 9:14 - 16:7 - 9.

[0017] Preferably, the washing is to wash repeatedly with ethanol and water 2 - 5 times in sequence.

[0018] Preferably, the preparation method of the α-MnO 2 positive electrode material is: adding a binder made of polyvinylidene fluoride powder and N-methylpyrrolidone to the α-MnO 2 powder, adding carbon black, and regulating the viscosity by dropping N-methylpyrrolidone solution. After making a slurry, it is evenly coated on a titanium sheet to obtain the manganese dioxide positive electrode material.

[0019] More preferably, the molar ratio of the polyvinylidene fluoride powder and N-methylpyrrolidone is 1:19, and the molar ratio of the α-MnO 2 powder, carbon black and polyvinylidene fluoride powder is controlled at 8:1:1.

[0020] More preferably, the coating thickness is 140 - 170 μm, and the manganese dioxide loading on the titanium sheet is controlled at 1 - 3 mg / cm 2 .

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] In the present invention, by introducing low-concentration halogen ions into the traditional zinc sulfate electrolyte, the combination of halogen ions and water molecules is promoted, thereby inducing uniform zinc deposition, thereby improving the cycle life and battery performance of the aqueous zinc-ion battery. At the same time, the introduction of a lower-concentration halogen ion additive realizes an obvious improvement in the performance of the aqueous zinc-ion battery, and can effectively reduce the cost. Among them, the cycle life test shows that on the premise of adding zinc iodide, the prepared battery has a double-layer diaphragm at 5 mA·cm -2 and 1 mAh·cm -2Under such conditions, an ultra-long cycle life of 1900 h was achieved (compared with the cycle life of 340 h of traditional zinc sulfate batteries), improving the performance of the battery. The results of electrochemical analysis show that the introduction of zinc iodide can change the properties of the battery, provide a larger current density at the same potential, promote faster nucleation, and induce the formation of uniform zinc deposition. The electrode sheets before and after cycling were characterized, and it was found that the proportion of (002)Zn increased after the introduction of iodide ions. On this basis, two manganese dioxide cathode materials with different structures (α-MnO 2 , β-MnO 2 ) were prepared. A zinc-manganese dioxide full battery was composed with a zinc anode, and zinc bromide was introduced into the full battery system. Utilizing the characteristic that the potential of bromide ions is similar to that of manganese dioxide, bromide ions were used to improve the capacity of the manganese dioxide cathode material. Through the comparison of charge-discharge curves, it was found that when choosing α-MnO 2 with a spherical structure as the cathode material, the zinc-manganese dioxide full battery using halogen ions as additives had a significantly improved capacitance compared with the traditional zinc sulfate electrolyte full battery and had a higher capacity. Description of the Drawings

[0023] Figure 1 Comparison of the cycle life of a traditional ZnSO 4 electrolyte and an aqueous zinc-ion battery assembled after introducing 0.01 mol / L ZnI 2 electrolyte;

[0024] Figure 2 Comparison of the cyclic voltammograms of a traditional ZnSO 4 electrolyte and an aqueous zinc-ion battery assembled after introducing 0.01 mol / L ZnI 2 electrolyte;

[0025] Figure 3 Comparison of the X-ray diffraction patterns of the negative zinc sheet after cycling of a traditional ZnSO 4 electrolyte and an aqueous zinc-ion battery assembled after introducing 0.01 mol / L ZnI 2 electrolyte;

[0026] Figure 4 X-ray diffraction patterns of α-MnO 2 and β-MnO 2 ;

[0027] Figure 5 Scanning electron microscope images of two cathode materials, α-MnO 2 and β-MnO 2 ;

[0028] Figure 6Comparison of charge-discharge curves after coupling bromide ions with two manganese dioxide cathode materials in a full cell. Detailed implementation manners

[0029] The following further describes the detailed implementation manners of the present invention. It should be noted here that the description of these implementation manners is for helping to understand the present invention, but does not limit the present invention. In addition, the technical features involved in the various implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The experimental methods in the following examples are all conventional methods unless otherwise specified, and the test materials used in the following examples are all available through conventional commercial channels unless otherwise specified.

[0031] Example 1: Application of halogen ions as electrolyte additives in aqueous zinc-ion batteries

[0032] 1. Weigh 2.8758 g of zinc sulfate and dissolve it in 10 mL of deionized water. After stirring to fully dissolve it, then weigh 0.0319 g of zinc iodide and add it thereto. After fully dissolving and mixing, a 1 mol / L zinc sulfate + 0.01 mol / L zinc iodide electrolyte is prepared. Or: Weigh 2.8758 g of zinc sulfate and dissolve it in 10 mL of deionized water. After stirring to fully dissolve it, a 1 mol / L zinc sulfate electrolyte is prepared.

[0033] 2. Preparation of manganese dioxide

[0034] (1) Mix 1.3522 g of manganese sulfate monohydrate, 1.9820 g of ammonium sulfate, and 1.8256 g of ammonium persulfate powder (i.e., 0.008 mol of manganese sulfate monohydrate, 0.015 mol of ammonium sulfate, 0.008 mol of ammonium persulfate) and dissolve them in 50 mL of deionized water to obtain a clear solution. Then place it in a reaction kettle and heat it at 120 °C for 12 h. After the product is completely cooled, take it out and perform suction filtration with a suction filter. At the same time, wash it three times repeatedly with absolute ethanol and deionized water, and finally dry it in an oven at 60 °C to obtain α-MnO 2 powder.

[0035] (2) Mix 1.3522 g of manganese sulfate monohydrate and 1.9820 g of ammonium sulfate powder and dissolve them in 50 mL of deionized water to obtain a clear solution. Then place it in a reaction kettle and heat it at 120 °C for 12 h. After the product is completely cooled, take it out and perform suction filtration with a suction filter. At the same time, wash it three times repeatedly with absolute ethanol and deionized water, and finally dry it in an oven at 60 °C to obtain β-MnO 2 powder.

[0036] 3. Preparation of manganese dioxide cathode material

[0037] (1) Add an N-methylpyrrolidone solution containing polyvinylidene fluoride powder (molar ratio 1:19) and 10 mg of carbon black to the prepared manganese dioxide powder to make a slurry. Among them, the molar ratio of manganese dioxide powder, carbon black, and polyvinylidene fluoride powder is 8:1:1. Then stir with a magnetic stirrer, and at the same time, add approximately 240 mg of N-methylpyrrolidone solution during the stirring process to adjust the viscosity of the slurry. Stop stirring after about two hours when the slurry becomes a uniform and flowable state.

[0038] (2) Coat the flowable slurry on a titanium sheet with a coater, control the coating thickness to be 150 μm, and finally obtain a manganese dioxide loading of approximately 1 mg / cm on the titanium sheet. 2 to prepare the manganese dioxide positive electrode material.

[0039] 4. Assembly of Aqueous Zinc-Ion Batteries

[0040] (1) Assemble a zinc-zinc symmetric battery with the battery model CR2032. The battery structure includes a positive electrode battery case, a negative electrode battery case, a mixed halogen electrolyte or zinc sulfate electrolyte, a separator, a gasket, a spring sheet, and a circular zinc sheet with a diameter of 1.4 cm, and use a battery sealer for encapsulation.

[0041] (2) Assemble a zinc-manganese dioxide full battery with the battery model CR2032. The battery structure includes a positive electrode battery case, a negative electrode battery case, a mixed halogen electrolyte or zinc sulfate electrolyte, a separator, a gasket, a spring sheet, a circular zinc sheet with a diameter of 1.4 cm, and a circular titanium sheet with a diameter of 1.0 cm covered with manganese dioxide positive electrode material, and use a battery sealer for encapsulation.

[0042] Introduce 0.01 mol / L zinc bromide electrolyte into 1 mol / L zinc sulfate electrolyte and couple it with the manganese dioxide positive electrode material to assemble a zinc-manganese dioxide full battery. Utilize the characteristic that the potential of bromide ions is similar to that of manganese dioxide, and use bromide ions to provide capacity for the manganese dioxide positive electrode material, thereby improving the capacity of the full battery.

[0043] Example 2: Material Characterization and Battery Performance Testing

[0044] (1) Cycle life test: Use a CT-400Tn-5V50mA battery test system to conduct a cycle life test on symmetric batteries assembled with 1 mol / L zinc sulfate electrolyte and 1 mol / L zinc sulfate + 0.01 mol / L zinc iodide electrolyte (hereinafter simply referred to as zinc sulfate electrolyte battery and battery with zinc iodide electrolyte additive). The test conditions are 5 mA / cm 2 , 1 mAh / cm 2, finally, the cycle life of the zinc sulfate electrolyte battery is 340 h, and that of the battery with zinc iodide electrolyte additive is 1900 h( Figure 1 ).

[0045] (2) Cyclic voltammetry curve test: The cyclic voltammetry curves of the zinc sulfate electrolyte battery and the symmetric battery with zinc iodide electrolyte additive were tested using a CS2350M electrochemical workstation. The voltage scanning range was -0.4 V - 0.6 V, and the scanning rate was 1 mV / s. It was found that the battery with zinc iodide electrolyte additive provided a higher current density at the same potential( Figure 2 ).

[0046] (3) X-ray diffraction pattern of the negative zinc sheet after cycling: The surface of the zinc sheet after cycling of the zinc sulfate electrolyte battery and the symmetric battery with zinc iodide electrolyte additive was characterized using an Ultima X-ray diffractometer. The test conditions were 5° - 90° and 10° / min. It was found that the proportion of (100)Zn in the zinc sulfate electrolyte battery was higher, and the proportion of (002)Zn in the battery with zinc iodide electrolyte additive was higher. And (002)Zn is beneficial to the formation of uniform zinc deposition, indicating that the battery with zinc iodide electrolyte additive is beneficial to inhibiting the formation of zinc dendrites( Figure 3 ).

[0047] (4) X-ray diffraction analysis of α-MnO 2 and β-MnO 2 : The surfaces of α-MnO 2 and β-MnO 2 were characterized using an X-ray diffractometer, and the peak results were consistent with those of the standard cards( Figure 4 ).

[0048] (5) Scanning electron microscope images of the positive electrode materials: The surface morphologies of the positive electrode materials of α-MnO 2 and β-MnO 2 were characterized using a JEOL JSM-IT200A scanning electron microscope at a magnification of 5000 times. It was observed that α-MnO 2 was a spherical structure, and β-MnO 2 was a needle-like structure( Figure 5 ).

[0049] (6) Charge-discharge curve test of the full battery: The charge-discharge curves of the zinc sulfate electrolyte battery and the zinc-manganese dioxide full battery with zinc bromide electrolyte additive were tested using a battery test system. The test conditions were a voltage of 0.8 V - 1.8 V. Taking the first 5 cycles, it was observed that the initial capacity of the zinc sulfate electrolyte battery in β-MnO 2 was 30 mAh / g, while that in α-MnO 2The initial capacity of the zinc sulfate electrolyte battery is 50 mAh / g, indicating that α-MnO 2 cathode material has better performance than β-MnO 2 cathode material; in α-MnO 2 , the initial capacity of the zinc sulfate electrolyte battery is observed to be 120 mAh / g, while that of the battery with zinc bromide electrolyte additive is 180 mAh / g, indicating that the addition of zinc bromide electrolyte improves the initial capacity of the zinc-manganese dioxide full battery( Figure 6 ).

[0050] In summary, the introduction of zinc iodide electrolyte additive can inhibit the formation of zinc dendrites, improve the cycle life and performance of the aqueous zinc-ion battery, and the introduction of zinc bromide electrolyte additive can improve the capacity of the manganese dioxide cathode material, and the α-MnO 2 cathode material in the assembled zinc-manganese dioxide full battery has better performance. In addition, the halogen electrolyte additive can achieve obvious performance improvement at a low addition concentration, effectively reduce the manufacturing cost, and is expected to be used in the energy storage system of the aqueous zinc-ion battery.

[0051] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

Claims

1. Application of halogen ion electrolyte additive in aqueous zinc ion battery, characterized in that: The halogen ion electrolyte additive is zinc iodide or zinc bromide.

2. The use according to claim 1, characterized in that: The electrolyte is an aqueous solution of zinc salt, and the concentration of the zinc salt is 1-3 mol / L.

3. The use according to claim 1, characterized in that: The concentration of halogen ions in the electrolyte is 0.01-0.03 mol / L.

4. The use according to claim 1, characterized in that: The aqueous zinc ion battery includes a zinc-zinc symmetrical battery and a zinc-manganese dioxide full battery.

5. A zinc-manganese dioxide full battery, characterized in that: The zinc-manganese dioxide full battery uses zinc bromide as an electrolyte additive and α-MnO2 as a positive electrode material.

6. A zinc-manganese dioxide full battery according to claim 5, characterized in that: The preparation method of α-MnO2 is as follows: dissolving monohydrated manganese sulfate, ammonium sulfate and ammonium persulfate into water, heating for reaction, and then filtering, washing and drying to obtain the α-MnO2.

7. A zinc-manganese dioxide full battery according to claim 6, characterized in that: The heating reaction is carried out at a temperature of 100-150° C. and for a time of 10-15 hours.

8. A zinc-manganese dioxide full battery according to claim 6, characterized in that: The molar ratio of the manganese sulfate monohydrate, ammonium sulfate and ammonium persulfate is 7-9:14-16:7-9.

9. A zinc-manganese dioxide full battery according to claim 6, characterized in that: The washing is performed by repeatedly washing with ethanol and water for 2-5 times.

10. A zinc-manganese dioxide full battery according to claim 6, characterized in that: The preparation method of α-MnO2 positive electrode material is as follows: add a binder made by mixing polyvinylidene fluoride powder and N-methylpyrrolidone to α-MnO2 powder, then add carbon black, and adjust the viscosity by dripping N-methylpyrrolidone solution, and evenly apply the slurry on the titanium sheet to obtain manganese dioxide positive electrode material.

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