A water-based zinc-based electrolyte, a preparation method and application thereof

Abstract

The application discloses a kind of aqueous zinc-based electrolyte and its preparation method and application, the electrolyte is composed of zinc salt, additive and solvent.The additive is tetraoxypyrimidine, the additive can be coordinated with zinc ion to weaken its hydration effect, and adsorbed on the surface of zinc negative electrode to induce uniform deposition of zinc ion, promote uniform zinc ion flux.Especially, the additive has certain oxidizability, which can digest zinc dendrite by interacting with zinc dendrite, thereby prolonging battery life.The application provides a simple, efficient and low-cost solution to the problems of dendrite, hydrogen evolution and corrosion existing in the negative electrode of the current aqueous zinc-based battery, and obtains a high-performance aqueous zinc-based battery, which can help the development of low-cost and high-performance zinc-based battery, and greatly promote the commercialization application process of aqueous zinc-based battery.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, specifically to an aqueous zinc-based electrolyte, its preparation method, and its application. Background Technology

[0002] Renewable energy sources such as solar, wind, and hydropower are seasonal and time-sensitive. Directly connecting them to the grid can lead to power supply fluctuations, making it difficult to directly match electricity demand. Therefore, storing renewable energy is key to resolving this contradiction. Lithium-ion batteries (LIBs) are currently the most mature electrochemical energy storage device. However, their inherent safety issues, high cost, and low abundance in the Earth's crust limit their application in large-scale energy storage.

[0003] To fill this gap, researchers proposed an aqueous zinc-based battery. This aqueous zinc-based battery utilizes the high theoretical volumetric capacity of zinc metal (5855 mAh cm⁻¹). -3 Based on the theoretical premise of low redox potential (-0.76V vs. standard hydrogen electrode), and with advantages such as low cost, environmental friendliness and high abundance in the Earth's crust, it has become one of the popular candidates for large-scale energy storage.

[0004] However, uncontrolled dendrite growth and corrosion side reactions have always been obstacles to the commercialization of zinc-based batteries. Uneven zinc deposition leads to dendrite growth, which will damage the smooth electrode surface and puncture the separator after several cycles, causing a short circuit. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an aqueous zinc-based electrolyte, its preparation method, and its application. The aqueous zinc-based electrolyte of this invention can solve the problems of battery failure caused by dendrite growth and side reactions, thereby improving battery performance and extending battery life.

[0006] To achieve the above objectives, the specific solution adopted by the present invention is as follows:

[0007] On one hand, the present invention provides an aqueous zinc-based electrolyte, comprising a zinc salt, an additive, and a solvent, wherein the additive is alloxan; the concentration of the additive in the electrolyte is 1-5 g / L.

[0008] Furthermore, the zinc salt is any one or more of zinc sulfate, zinc chloride, or zinc bromide.

[0009] Furthermore, the concentration of zinc salt in the electrolyte is 1–2 mol / L.

[0010] 4. Further, the solvent is water.

[0011] On the other hand, the present invention provides a method for preparing an aqueous zinc-based electrolyte, comprising the following steps:

[0012] S1. Prepare the base solution using solvent and zinc salt;

[0013] S2. Add the additive to the base solution and sonicate it to dissolve, thus obtaining the electrolyte.

[0014] In another aspect, the present invention provides an application of the above-mentioned aqueous zinc-based electrolyte in the field of aqueous zinc-based batteries.

[0015] Beneficial effects:

[0016] (1) The electrolyte of this invention includes a tetraoxazine additive. Tetraoxazine is an oxygen-containing derivative of pyrimidine. Compared with pyrimidine, all of its carbon-hydrogen bonds are replaced by carbon-oxygen double bonds. At this time, all four oxygen atoms of the molecule have lone pairs of electrons, which can coordinate with the zinc ion orbitals to form coordination ions, inhibiting the interaction between zinc ions and water, thereby weakening the solvation effect and homogenizing the zinc ion concentration field. In addition, the carbon-oxygen double bonds of tetraoxazine can open to form hydroxyl groups, thereby consuming interfacial hydrogen ions and taking electrons from zinc dendrites to dissolve them, thus inhibiting hydrogen evolution, corrosion and dendrite growth. The reaction equation is shown below:

[0017]

[0018] In summary, the electrolyte of this application achieves dendrite-free and stable zinc deposition by adding alloxan additives, thereby greatly improving the cycle reversibility of the battery.

[0019] (2) The electrolyte in this invention is an aqueous solution, which does not have the safety hazards of organic electrolytes in lithium-ion batteries, and is environmentally friendly, low in cost and high in energy density. Attached Figure Description

[0020] Figure 1 This is a cycle life diagram for battery A.

[0021] Figure 2 This is a cycle life diagram for battery B.

[0022] Figure 3 This is a cycle life diagram for battery C.

[0023] Figure 4 This is a cycle life diagram for battery D.

[0024] Figure 5 This is a cycle life diagram for battery E.

[0025] Figure 6 This is a cycle life diagram for battery F.

[0026] Figure 7 This is a SEM image of the zinc electrode surface of battery A after cycling.

[0027] Figure 8 This is a SEM image of the zinc electrode surface of battery B after cycling.

[0028] Figure 9 This is a SEM image of the zinc electrode surface of battery C after cycling.

[0029] Figure 10 This is a SEM image of the zinc electrode surface of battery D after cycling.

[0030] Figure 11 The image shows the XRD pattern of the zinc electrode surface after cycling in the battery AD converter. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0032] To address the inherent hydrogen evolution and corrosion problems in aqueous zinc-based batteries and to inhibit zinc dendrite growth, this invention provides an aqueous zinc-based electrolyte, its preparation method, and its applications. The aqueous zinc-based battery includes an electrolyte, a positive electrode, a separator, and a negative electrode (which can be metallic zinc, carbon felt, or graphite felt). The electrolyte includes a zinc salt, an additive, and a solvent, wherein the additive is alloxan; the concentration of the additive in the electrolyte is 1–5 g / L, and the concentration of the zinc salt is 1–2 mol / L. The main component of the additive in this invention is alloxan, which can bind with zinc ions to remove active water molecules and adsorb onto the electrode surface to eliminate dendrite growth.

[0033] Preferably, the zinc salt is any one or more of zinc sulfate, zinc chloride, or zinc bromide. The solvent is water.

[0034] The electrolyte is prepared by first using a solvent and zinc salt to prepare a basic solution; then adding additives to the basic solution and ultrasonically stirring to dissolve them, thus obtaining the electrolyte.

[0035] The technical solution of the present invention will be described in detail below with reference to embodiments and comparative examples.

[0036] Example 1

[0037] A method for preparing an aqueous zinc-based electrolyte mainly includes the following steps:

[0038] S1. Place 32.29g of zinc sulfate in an appropriate amount of deionized water, and then sonicate it for 15min to completely dissolve it, to obtain 100mL of basic solution containing 2mol / L zinc sulfate.

[0039] S2. Dissolve 0.1g of alloxan in the base solution, and then sonicate for 5min to completely dissolve it, to obtain 100mL of electrolyte containing 2mol / L zinc sulfate and 1g / L alloxan.

[0040] The electrolyte prepared in this embodiment was used to fabricate an aqueous zinc-based battery. Specifically, commercial zinc foil (100 μm thick) was first cleaned and cut into φ11.3 mm circular pieces to form zinc electrodes. Then, the positive electrode shell was placed on the experimental table with its inner surface facing up, and the zinc electrode, separator, zinc electrode, and gasket were placed in sequence. The electrolyte was then dripped in to completely wet the separator, and the negative electrode shell was then covered. After sealing, a zinc symmetric battery was obtained, denoted as battery A.

[0041] Example 2

[0042] The difference between Example 2 and Example 1 is that in step S2, 0.3g of alloxan is dissolved in the base solution and then ultrasonically dispersed for 5 minutes to completely dissolve it, resulting in 100mL of electrolyte containing 2mol / L zinc sulfate and 3g / L alloxan.

[0043] The electrolyte prepared in this example was used to make a battery, denoted as Battery B, using the battery preparation method described in Example 1.

[0044] Example 3

[0045] The difference between Example 3 and Example 1 is that in step S2, 0.3g of alloxan is dissolved in the base solution and then ultrasonically dispersed for 5 minutes to completely dissolve it, resulting in 100mL of electrolyte containing 2mol / L zinc sulfate and 3g / L alloxan.

[0046] The electrolyte prepared in this example was used to make a battery, denoted as battery C, using the battery preparation method described in Example 1.

[0047] Comparative Example 1

[0048] The difference between Comparative Example 1 and Example 1 is that it does not include step S2.

[0049] The electrolyte prepared in this comparative example was used to make a battery, denoted as battery D, using the battery preparation method described in Example 1.

[0050] Comparative Example 2

[0051] The difference between Comparative Example 2 and Example 1 is that in step S2, 0.05 g of alloxan was dissolved in the base solution and then ultrasonically dispersed for 5 min to completely dissolve it, resulting in a 100 mL electrolyte containing 2 mol / L zinc sulfate and 0.5 g / L alloxan.

[0052] The electrolyte prepared in this comparative example was used to make a battery, denoted as battery E, using the battery preparation method in Example 1.

[0053] Comparative Example 3

[0054] The difference between Comparative Example 3 and Example 1 is that in step S2, 0.6 g of alloxan was dissolved in the base solution and then ultrasonically dispersed for 5 min to completely dissolve it, resulting in a 100 mL electrolyte containing 2 mol / L zinc sulfate and 6 g / L alloxan.

[0055] The electrolyte prepared in this comparative example was used to make a battery, denoted as battery F, using the battery preparation method described in Example 1.

[0056] The cycle life of the battery AF was tested, and the results are as follows: Figures 1 to 6 As shown, at 10mAcm -2 Current density and 10mAh cm -2 At the given area and capacity, battery A can achieve stable cycling for over 170 hours (e.g., Figure 1 As shown), battery B has a stable cycle life exceeding 180 hours (e.g. Figure 2 As shown), battery C has a stable cycle life exceeding 240 hours (e.g. Figure 3 As shown), battery D experiences a short circuit after 30 hours of cycling (as indicated). Figure 4 As shown), a short circuit occurred in the battery after 110 hours of cycle E (as indicated). Figure 5 As shown), it is slightly improved compared to Comparative Example 1. After 110 hours of cycling, the overpotential of battery F fluctuates drastically (as shown). Figure 6 (As shown), a short circuit subsequently occurred.

[0057] The surfaces of the zinc electrodes in batteries A, B, C, and D after cycling were observed using a scanning electron microscope. The results are as follows: Figure 7-10 As shown. Figure 10 The diagram shows the microstructure of the zinc electrode in battery D. It can be seen that there are a large number of fine dendrites on the surface, many by-products, and a very poor surface morphology. Figure 7 This is a microstructure diagram of the zinc electrode in battery A, and... Figure 10 compared to, Figure 7 Significant changes occurred in the sediment morphology, with dendrites and byproducts being greatly suppressed, indicating that a considerable portion of the zinc dendrites had been reduced in situ by alloxan. Figure 8 This is a microstructure diagram of the zinc electrode in battery B, and... Figure 10 and Figure 7 compared to, Figure 8 The deposition morphology in the sample is already quite dense, with multiple zinc crystals tightly packed together, eliminating dendrite growth, indicating that the zinc dendrites were almost completely reduced in situ by alloxan. Figure 9 This is a microstructure diagram of the zinc electrode in battery C, and... Figure 7 , Figure 8 and10 compared to, Figure 9 The zinc deposition is very dense, and the zinc dendrites are completely reduced in situ by alloxan. The zinc crystals fuse to form large zinc flakes, achieving a smooth deposition process.

[0058] Furthermore, the present invention performed X-ray diffraction tests on the zinc electrodes of batteries A, B, C, and D after cycling, and the results are as follows. Figure 11 As shown. The byproduct peak in Comparative Example 1 is the most prominent, indicating the occurrence of severe corrosion side reactions and hydrogen evolution reaction. The intensity ratio of the (002) crystal plane peak to the (101) crystal plane peak in Comparative Example 1 is I 002 / I 101 The value was only 1.44, while in Examples 2 and 3 it was 1.78 and 1.80 respectively, which was significantly higher than the comparative example, proving that the additive could induce zinc to be deposited along the (002) crystal plane, thus improving corrosion resistance and smoothness.

[0059] In summary, the electrolyte provided by this invention significantly inhibits zinc dendrite growth, demonstrating that the alloxan additive can effectively improve the operating performance of aqueous zinc-based batteries. The lower cycle life of Comparative Examples 2 and 3 indicates that the optimal effect can be achieved at an additive concentration of 1–5 g / L.

[0060] The electrolyte provided in this application significantly inhibits the growth of zinc dendrites and the occurrence of side reactions through the carbon-oxygen double bond in alloxan. This method is simple to operate, easy to scale up, and significantly improves the cycle life of aqueous zinc-based batteries assembled using this electrolyte.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An aqueous zinc-based electrolyte, characterized in that: It includes zinc salt, additives and solvent, wherein the additive is alloxan; the concentration of the additive in the electrolyte is 1 to 5 g / L.

2. The aqueous zinc-based electrolyte as described in claim 1, characterized in that, The zinc salt is any one or more of zinc sulfate, zinc chloride, or zinc bromide.

3. The aqueous zinc-based electrolyte as described in claim 1, characterized in that: The concentration of zinc salt in the electrolyte is 1–2 mol / L.

4. The aqueous zinc-based electrolyte as described in claim 1, characterized in that: The solvent is water.

5. A method for preparing an aqueous zinc-based electrolyte as described in claim 1, characterized in that, Includes the following steps: S1. Prepare the base solution using solvent and zinc salt; S2. Add the additive to the base solution and sonicate it to dissolve, thus obtaining the electrolyte.

6. The application of the aqueous zinc-based electrolyte as described in any one of claims 1 to 4 in the field of aqueous zinc-based batteries.

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