An aqueous zinc-ion battery and its preparation method

Abstract

This application provides an aqueous zinc-ion battery and its preparation method, belonging to the field of energy storage system technology. It includes a positive electrode, a negative electrode, an electrolyte, and a separator. The active material of the positive electrode is a cyclic azo organic compound, the active material of the negative electrode is a zinc-based material, and the electrolyte is an aqueous electrolyte containing zinc salts. This application effectively inhibits the dissolution of the organic positive electrode in the aqueous electrolyte by introducing an azo organic compound with a cyclic conjugated structure as the positive electrode active material, improving the reversibility of the zinc ion insertion / deintercalation reaction, thereby significantly improving the cycle stability and rate performance of the aqueous zinc-ion battery.

Description

Technical Field

[0001] This application relates to an aqueous zinc-ion battery and its preparation method, belonging to the field of energy storage system technology. Background Technology

[0002] Aqueous zinc-ion batteries are a novel electrochemical energy storage technology, typically composed of key components such as a zinc metal negative electrode, a positive electrode, an electrolyte, and a separator. Their core working principle can be simply summarized as follows: zinc metal undergoes a reversible deposition / stripping reaction on the negative electrode side, while the active material and zinc ions undergo reversible intercalation / deintercalation or coordination reactions on the positive electrode side, thereby achieving the interconversion of electrical energy and chemical energy.

[0003] Therefore, zinc-ion batteries have advantages such as high theoretical capacity, high safety of aqueous electrolytes, and abundant raw material sources. However, traditional aqueous zinc-ion batteries still have many shortcomings in terms of cathode materials, electrolyte composition, and interface stability, which limit the further improvement of their electrochemical performance and the expansion of their application range.

[0004] Therefore, it is of great significance to develop an aqueous zinc-ion battery with high stability, long cycle life and controllable cost. Summary of the Invention

[0005] In view of this, this application first provides an aqueous zinc-ion battery, which effectively suppresses the dissolution of organic cathode in aqueous electrolyte by introducing an azo organic compound with a cyclic conjugated structure as the positive electrode active material, improves the reversibility of zinc ion insertion / deintercalation reaction, and thus significantly improves the cycle stability and rate performance of the aqueous zinc-ion battery.

[0006] Specifically, this application is implemented through the following scheme:

[0007] An aqueous zinc-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The active material of the positive electrode is a cyclic azo organic compound with a cyclic conjugated structure, the active material of the negative electrode is a zinc-based material, and the electrolyte is an aqueous electrolyte containing zinc salts.

[0008] This application uses cyclic azo organic compounds as the positive electrode active material. This active material has a stable cyclic conjugated structure and excellent reversible redox properties, which can effectively inhibit the dissolution of the active material in aqueous electrolytes. The negative electrode active material, composed of zinc-based materials, undergoes a reversible zinc deposition / stripping reaction during charge and discharge. It works synergistically with the positive electrode active material to complete the electrochemical reaction. Combined with an aqueous electrolyte containing zinc salts, this gives the battery good electrochemical stability and cycle performance, effectively improving the battery's power density and lifespan.

[0009] Furthermore, as a preferred option:

[0010] The cyclic azo organic compounds are cyclic azobenzene compounds.

[0011] More preferably:

[0012] The cyclic azobenzene compound is obtained by the following method: using a benzene ring as a raw material, an azo group is introduced onto the benzene ring through a Mills reaction to obtain a diaminodiazo precursor, and the diaminodiazo precursor undergoes a molecular cyclization reaction to form an azobenzene compound with a cyclic structure.

[0013] The zinc-based material is zinc metal plate, zinc foil, zinc powder, porous zinc electrode or zinc alloy, with zinc metal (zinc metal plate, zinc foil, zinc powder) being preferred.

[0014] The zinc salt is at least one of zinc sulfate (ZnSO4), zinc perchlorate, zinc acetate, zinc tetrafluoroborate, zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc trifluoromethanesulfonate, and bis(trifluoromethanesulfonylimide) zinc, with zinc sulfate being preferred.

[0015] The zinc salt concentration in the electrolyte is 1~5 mmol / L.

[0016] The separator is a hydrophilic anti-dendritic composite battery separator.

[0017] The above-mentioned aqueous zinc-ion battery can be prepared using the following method:

[0018] Step 1: Mix cyclic azo organic compounds with conductive materials and binders, add N-methylpyrrolidone to dissolve and grind to prepare positive electrode slurry, coat the positive electrode slurry onto the surface of graphite paper and flatten it, dry it and cut it to obtain positive electrode sheet;

[0019] Step 2: Using the positive electrode as the positive electrode, along with the negative electrode, separator, and electrolyte, an aqueous zinc-ion battery is assembled.

[0020] The mass ratio of the cyclic azo organic compound to the conductive material and binder is 3:6:1.

[0021] The conductive material is carbon black (sp carbon) or carbon nanotubes.

[0022] The adhesive is a polyvinylidene fluoride or PTFE emulsion.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] Using cyclic azo organic compounds, such as cyclic azobenzene, as the positive electrode active material in an aqueous zinc-ion battery, combined with zinc-based materials such as zinc metal as the negative electrode active material and an aqueous electrolyte system containing zinc salts, the constructed battery exhibits excellent reversible redox performance and structural stability. It also features fast electrode reaction kinetics, low charge transport impedance, and stable output even at high rates, thus significantly improving the battery's power density. Simultaneously, this positive electrode material effectively suppresses dissolution in the aqueous electrolyte, improving the battery's energy utilization efficiency and cycle life. Furthermore, the preparation process of cyclic azobenzene is relatively simple, and the raw materials are widely available, facilitating large-scale production and reducing the overall cost of the battery. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0026] Figure 1 This is a schematic diagram illustrating the working principle of the aqueous zinc-ion battery of this application.

[0027] The numbers in the diagram are: 1. Negative electrode; 2. Positive electrode plate; 3. Separator; 4. Electrolyte.

[0028] Figure 2 This is a schematic diagram of the structure of the cyclic azobenzene compound in this application.

[0029] Figure 3 The graph shows the electrochemical performance of the positive and negative electrodes of this application in 2M ZnSO4 electrolyte using cyclic voltammetry. Part (a) of the graph shows the electrochemical performance of the positive electrode at different voltage change rates, and part (b) shows the potential difference between the positive and negative electrodes.

[0030] Figure 4 This is a charge-discharge curve of the battery in this application, obtained by constant current charge-discharge testing at a 0.5C rate.

[0031] Figure 5 The figures show the rate performance of the battery of this application and the conventional azobenzene solution. Part (a) of the figure shows the rate performance of the battery of this application, and part (b) shows the rate performance of the corresponding solution of conventional azobenzene material.

[0032] Figure 6 The diagram shows the long-cycle operation of the battery in this application at different rates. Part (a) in the diagram represents the operation at 0.5C rate, and part (b) represents the operation at 10C rate.

[0033] Figure 7 This is a comparison of the energy density of the battery in this application with that of the corresponding conventional azobenzene battery. Detailed Implementation

[0034] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0035] This embodiment provides an aqueous zinc-ion battery. The technical solution of this application is described below with reference to the accompanying drawings.

[0036] See Figure 1 , Figure 1 This diagram illustrates the core structure and working principle of the aqueous zinc-ion battery in this embodiment. It includes a negative electrode 1, a positive electrode 2, a separator 3, and an electrolyte 4.

[0037] 1) The negative electrode 1 is made of zinc metal plate.

[0038] 2) The active material in the positive electrode 2 is a cyclic azobenzene compound with a stable cyclic conjugated structure.

[0039] In this embodiment, the cyclic azobenzene compound can also be prepared by the following method:

[0040] Using o-nitrosoacetanilide and o-phenylenediamine as raw materials, and acetic acid as solvent, an azo group was introduced onto the benzene ring via a Mills reaction at 60°C to obtain a diaminodiazo precursor. Subsequently, the diaminodiazo precursor containing the azo group was subjected to a molecular cyclization reaction under anhydrous and oxygen-free conditions at room temperature using dichloromethane as solvent, lead tetraacetate as catalyst, and triethylamine as acid-binding agent, to introduce the azo group into a cyclic framework, yielding an azobenzene compound with a cyclic structure. After the reaction, the resulting product was separated, concentrated, and vacuum dried to obtain... Figure 2 The cyclic azobenzene compound with the structure shown.

[0041] 3) The diaphragm 3 is placed between the negative electrode 1 and the positive electrode 2 to isolate the positive and negative electrodes, prevent them from contacting each other directly, and allow zinc ions in the electrolyte to move freely.

[0042] 4) Electrolyte 4 contains 2M zinc sulfate.

[0043] The preparation method of aqueous lithium-ion batteries is as follows:

[0044] Step 1, Prepare the positive electrode:

[0045] Cyclic azobenzene compound, sp carbon, and polyvinylidene fluoride were mixed in a mortar in a ratio of 3:6:1. Then, nitrogen-methylpyrrolidone (NMP) was added to form a uniform slurry. The slurry was coated onto the surface of a 50 μm graphite paper current collector with a doctor blade. After drying at 60°C, it was cut into a positive electrode sheet with a diameter of 15 mm.

[0046] Step 2, processing the negative electrode: Take a new metal plate as the raw material for the negative electrode, grind and clean it to remove the zinc oxide layer on the surface, and then cut it into round pieces with a diameter of 15mm using a cutting machine, which are the negative electrodes.

[0047] Step 3, Assemble the battery:

[0048] Using the positive electrode sheet prepared in step one as the positive electrode and the material processed in step two as the negative electrode, a CR2016 battery case is used. A zinc-nickel ion-specific hydrophilic membrane CZ356 is placed between the positive and negative electrodes, and a zinc sulfate aqueous electrolyte with a content of 2M is injected to complete the assembly of the aqueous zinc-ion battery.

[0049] The positive electrode and battery obtained by the above method were subjected to performance tests, including cyclic voltammetry (CV), constant current charge-discharge method, rate performance test, and long-cycle performance test.

[0050] CV curve data were recorded using a Gamry Interface 5000E electrochemical workstation. Tests were performed using a glassy carbon working electrode, an Ag / AgCl reference electrode, and a platinum wire electrode. Figure 3 As shown in part (a), when cyclic azobenzene is used as the positive electrode active material, the positive electrode exhibits excellent reversible redox performance in aqueous systems. Its redox potential does not change with increasing voltage change rate, and the average median voltage of cyclic azobenzene is 70 mV (vs Ag / AgCl), proving that cyclic azobenzene has a high redox potential. Simultaneously, its small inter-peak potential difference indicates low polarization and fast redox kinetics, making it a potential positive electrode material for aqueous zinc-ion batteries. Furthermore, combined with… Figure 3 As can be seen from part (b), the potential difference between the positive and negative electrodes is approximately 1.12V.

[0051] Charge / discharge performance, rate performance, and long-cycle performance were recorded using LANDdt software.

[0052] Charge and discharge test results are as follows Figure 4 As shown: The aqueous zinc-ion battery in this embodiment exhibits a stable voltage plateau during discharge, with the main discharge plateau located at approximately 1.1V, which is consistent with the potential difference between the cyclic voltammetry curves (see...). Figure 3 (part (b)) has a higher output voltage. When cyclic azobenzene is used as the positive electrode active material, it exhibits higher output voltage under low rate conditions (such as...). Figure 4At 0.5C, it can achieve a specific capacity output close to its theoretical single-electron reaction capacity, demonstrating good electrochemical activity utilization.

[0053] Rate performance tests were conducted on the cyclic azobenzene cathode under different rate conditions, and the results are as follows: Figure 5 As shown, Figure 5 The black line represents the coulombic efficiency, and the red and green lines represent the charge / discharge capacity on the left vertical axis. The C-rate indicates how quickly the battery charges or discharges to its theoretical capacity; a higher C-rate corresponds to a higher current density and a faster charge / discharge rate. At low rates (1C, 2C, etc.), the battery's discharge capacity remains stable at approximately 95-100 mAh / g. As the current density increases significantly to 10C, the discharge capacity does not experience a drastic drop but instead stabilizes at approximately 85 mAh / g. Figure 5 In part (a), the capacity retention rate is significantly higher than that of the azobenzene material in CN116207373A when it is used as the positive electrode. Figure 5 (See part (b)). Even at ultra-high current densities of 20C, 30C, 50C, and even 100C, the battery can still operate normally and provide a certain capacity, with approximately 15 mAh / g at 100C. Figure 5 (as shown in part (a)). This ability to remain functional even under extreme conditions demonstrates its excellent rapid charge-discharge capability, further confirming that its electrochemical reaction has extremely fast reaction kinetics.

[0054] Long-cycle life tests were conducted on the constructed aqueous zinc-ion battery. The results are as follows: Figure 6 As shown: Under low to medium rate conditions, the capacity of the cyclic azobenzene cathode remained stable during hundreds of cycles, without significant capacity decay. Figure 6 In Part (a), the 0.5C; however, under high-rate conditions, after more than 3000 charge-discharge cycles, the battery still retains more than 70% of its initial capacity, and the coulombic efficiency remains close to 100% throughout the cycle. Figure 6 The 10C value in section (b) indicates that this aqueous zinc-ion battery possesses excellent structural stability and cycle durability.

[0055] To improve the specific capacity and cycle performance of zinc-ion batteries, the industry has conducted extensive research. For example, regarding cathode materials, azobenzene or halogen-substituted azobenzene (e.g., CN116207373A) is introduced, utilizing its N=N double bond as a redox active site to achieve reversible ion storage and release; or covalent cross-linking of nanosheets with organic active molecules (e.g., CN119297188A) is used to increase the redox active sites of the electrode. Regarding electrolytes, azobenzene-based organic small molecules with azo groups and their salts or derivatives (e.g., CN116598606A, CN119108665A) are introduced to reduce zinc dendrite formation and mitigate oxygen evolution corrosion of the zinc anode, thereby improving the battery's reversible capacity and cycle life. However, despite these successful studies, the azobenzene cathode still faces significant electrochemical polarization problems, primarily due to its strong hydrophobicity. In comparison, azopyridine has better hydrophilicity and electronic control capabilities, but its partial solubility in aqueous electrolytes can still lead to capacity decay during cycling. Therefore, effectively suppressing solubility while improving hydrophilicity is a key challenge in realizing high-performance azo cathode materials.

[0056] This application synthesizes a cyclic azobenzene molecule (C-azo) as an AZIB cathode material. By modifying the structure to improve the crystallinity of the small-molecule azo compound, its solubility in aqueous electrolytes is significantly reduced without sacrificing its intrinsic redox capabilities. The intrinsically porous molecular framework promotes the oxidation of Zn... 2+ The efficient diffusion of the AZIB device resulted in a high discharge potential (approximately 1.08V), excellent rate performance, and long-term cycle stability, effectively improving the battery's power density and lifespan (see [link]). Figure 7 It retains more than 73% of its capacity after 3000 cycles at 10°C.

[0057] In the above-described configuration, this application improves the crystallinity of small-molecule azo compounds by synthesizing cyclic azobenzene through structural modification, thereby significantly reducing their solubility in aqueous electrolytes without sacrificing their intrinsic redox capabilities. Simultaneously, their intrinsically porous molecular framework promotes the growth of Zn... 2+ The efficient diffusion of the electrolyte results in excellent fast charge and discharge capabilities. Although CN116207373A has good hydrophilicity and electronic regulation capabilities, its partial solubility in aqueous electrolytes still easily leads to capacity decay during cycling, resulting in a shorter battery life. Therefore, it cannot achieve the same effect.

[0058] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. An aqueous zinc-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that: The active material of the positive electrode is a cyclic azo organic compound with a cyclic conjugated structure, the active material of the negative electrode is a zinc-based material, and the electrolyte is an aqueous electrolyte containing zinc salts. The structural formula of the cyclic azo organic compound is: 。 2. The aqueous zinc-ion battery according to claim 1, characterized in that, The cyclic azo organic compounds are obtained by the following method: using a benzene ring as a raw material, introducing an azo group onto the benzene ring to obtain a diaminodiazo precursor, and then subjecting the diaminodiazo precursor to a molecular cyclization reaction to form a cyclic azo organic compound.

3. The aqueous zinc-ion battery according to claim 1, characterized in that: The zinc-based material is zinc metal plate, zinc foil, zinc powder, or zinc alloy.

4. The aqueous zinc-ion battery according to claim 1, characterized in that: The zinc salt is at least one of zinc sulfate, zinc perchlorate, zinc acetate, zinc tetrafluoroborate, zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc trifluoromethanesulfonate, and bis(trifluoromethanesulfonylimide) zinc.

5. The aqueous zinc-ion battery according to claim 1, characterized in that: The zinc salt concentration is 1~5 mmol / L.

6. The method for preparing an aqueous zinc-ion battery according to claim 1, characterized in that: The separator is a hydrophilic anti-dendritic composite battery separator.

7. A method for preparing the aqueous zinc-ion battery according to claim 1, characterized in that, The steps are as follows: Step 1: Mix cyclic azo organic compounds with conductive materials and binders, add N-methylpyrrolidone to dissolve and grind to prepare positive electrode slurry, coat the positive electrode slurry onto the surface of graphite paper and flatten it, dry it and cut it to obtain positive electrode sheet; Step 2: Using the positive electrode as the positive electrode, along with the negative electrode, separator, and electrolyte, an aqueous zinc-ion battery is assembled.

8. The method for preparing an aqueous zinc-ion battery according to claim 7, characterized in that: The mass ratio of cyclic azo organic compounds to conductive materials and binders is 3:6:

1.

9. The method for preparing an aqueous zinc-ion battery according to claim 7, characterized in that: The conductive material is carbon black or carbon nanotubes, and the binder is polyvinylidene fluoride or PTFE emulsion.

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