Electrolyte in aqueous zinc metal battery as well as preparation method and application of electrolyte

Abstract

The invention discloses an electrolyte in an aqueous zinc metal battery as well as a preparation method and application of the electrolyte. Relates to the field of electrolyte. The electrolyte comprises the following components: a zinc salt; an additive, wherein the additive comprises vitamin B6; and water. According to the invention, the vitamin B6 (VB6) is used as an electrolyte additive, and the VB6 additive has a certain effect of adjusting the pH value of the electrolyte; and the material can also be adsorbed on the electrode surface of the zinc metal battery, so that the effect of reducing side reactions caused by free water on the surface is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, and in particular to an electrolyte in an aqueous zinc metal battery and a preparation method and application thereof. Background Art

[0002] With the sharp increase in modern energy demand and increasingly stringent environmental protection requirements, the world is actively exploring sustainable energy solutions. As the most widely used energy storage device, lithium-ion batteries have shown excellent performance in many fields, but their development is limited by the scarcity of lithium resources. Lithium is a relatively scarce resource in the earth's crust, which leads to high costs for the application of lithium-ion batteries in large-scale energy storage. In addition, the organic electrolytes used in lithium-ion batteries also have safety issues, especially flammability and explosion risks, which make their application in large-scale energy storage scenarios face huge challenges. These problems have driven a global boom in research on new battery technologies, especially aqueous batteries.

[0003] Aqueous batteries have attracted much attention due to their high safety, environmental friendliness and low cost. Zinc-ion batteries, as a type of aqueous battery, benefit from the rich zinc resources, low cost, and high theoretical specific capacity (5855mAh cm -3 ), with a moderate electrode potential (-0.76 V relative to the standard hydrogen electrode), has shown great potential in the field of energy storage. However, in the process of practical application and commercialization, zinc-ion batteries still face a series of problems that need to be solved.

[0004] First, the main technical difficulty faced by zinc metal negative electrodes is that zinc ions often undergo uneven deposition during the charge and discharge process, leading to the formation of dendrites. Dendrites are metal microstructures generated during electrochemical reactions. These structures not only affect the life of the battery, but may also puncture the diaphragm, causing internal short circuits, and thus posing safety hazards. The growth of dendrites is a major obstacle in the current development of aqueous zinc-ion batteries, and how to effectively control the formation of dendrites is an important topic of current research.

[0005] Secondly, during operation, the zinc electrode is prone to hydrogen evolution reaction. This is because the electrolysis potential of water is lower than the reduction potential of zinc ions. Therefore, when zinc ions are deposited on the electrode, it is often accompanied by a side reaction of water decomposition to produce hydrogen. The hydrogen evolution reaction not only consumes the active substances in the battery, but also accelerates the consumption of the electrolyte and the corrosion of the electrode, thereby shortening the battery life. This problem seriously affects the coulombic efficiency and long-term stability of zinc-ion batteries.

[0006] In addition, the surface of the zinc electrode is prone to generate a passivation layer after long-term cyclic use, such as zinc hydroxide (Zn(OH)2) and zinc sulfate hydrate (Zn4SO4(OH)6·xH2O). These by-products will cover the electrode surface, hindering the effective transmission of zinc ions, resulting in a significant decrease in the electrochemical performance of the battery. The formation of the passivation layer not only reduces the activity of the electrode, but may also increase the internal impedance of the battery, resulting in a significant decrease in the charge and discharge performance. The interaction between these side reactions and by-products increases the complexity of aqueous zinc-ion batteries and hinders their commercialization.

[0007] In general, although aqueous zinc-ion batteries have shown broad application prospects in the field of energy storage, there are still many technical bottlenecks to achieve their real large-scale application. These problems do not exist in isolation, but influence and restrict each other. How to effectively solve these problems and improve the overall performance of zinc-ion batteries is still the core task of research in this field. Summary of the invention

[0008] The object of the present invention is to provide a stable electrolyte with no side reactions.

[0009] The first aspect of the present invention is:

[0010] An electrolyte is provided.

[0011] A second aspect of the present invention is:

[0012] Provided is a method for preparing an electrolyte.

[0013] The third aspect of the present invention is:

[0014] Application of the electrolyte.

[0015] The invention also provides a zinc metal battery.

[0016] Specifically, the technical solution adopted according to the first aspect of the present invention is:

[0017] An electrolyte comprising the following components:

[0018] Zinc salts;

[0019] Additives, wherein the additives include vitamin B6;

[0020] water.

[0021] According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0022] The present invention uses vitamin B6 (VB6) as an electrolyte additive. The VB6 additive not only has a certain function of adjusting the pH value of the electrolyte; it can also be adsorbed on the electrode surface of the zinc metal battery to reduce the side reactions caused by free water on the surface.

[0023] According to one embodiment of the present invention, the concentration ratio of the zinc salt to vitamin B6 is 200-220:4-4.2.

[0024] According to one embodiment of the present invention, the concentration of vitamin B6 is greater than 10 mmol L -1 , less than 70mmolL -1 .

[0025] According to one embodiment of the present invention, the concentration of vitamin B6 is 30-50 mmol L -1 .

[0026] According to one embodiment of the present invention, the concentration of vitamin B6 is 30-40 mmol L -1 .

[0027] According to one embodiment of the present invention, the concentration of vitamin B6 is 38-40 mmol L -1 .

[0028] According to one embodiment of the present invention, the concentration of vitamin B6 is 40-50 mmol L -1 .

[0029] According to one embodiment of the present invention, the concentration of vitamin B6 is 40-42 mmol L -1 .

[0030] According to one embodiment of the present invention, the concentration of vitamin B6 is 40 mmol L -1 .

[0031] The present invention finds that the vitamin B6 molecule has uniqueness, so that at a concentration of about 40 mM, the vitamin B6 molecule can be adsorbed on the surface of the zinc metal electrode, thereby reducing the side reactions caused by free water on the surface.

[0032] According to one embodiment of the present invention, the pH of the electrolyte is 3.2-3.4.

[0033] According to one embodiment of the present invention, the pH of the electrolyte is 3.3-3.4.

[0034] According to one embodiment of the present invention, the pH of the electrolyte is 3.3.

[0035] The present invention finds that the uniqueness of the vitamin B6 molecule enables vitamin B6 to further reduce side reactions on the surface of the zinc metal electrode at a specific initial pH value, and the specific initial pH is around 3.3.

[0036] According to one embodiment of the present invention, the zinc salt includes at least one of zinc chloride, zinc sulfate and zinc acetate.

[0037] Specifically, the technical solution adopted according to the second aspect of the present invention is:

[0038] A method for preparing the electrolyte comprises the following steps:

[0039] The zinc salt and the additive are mixed in water to obtain the electrolyte.

[0040] According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0041] The electrolyte preparation method provided by the present invention has a simple process, is easy to operate, and is suitable for commercial large-scale production applications. Compared with an electrolyte without any additives, the preparation method can effectively ensure that the negative zinc metal sheet of the zinc metal battery maintains a good morphology and state before and after the cycle, thereby improving the overall performance of the battery. This is mainly due to the fact that the VB6 molecule can be adsorbed on the tip of the zinc negative electrode surface through surface characteristics, effectively avoiding the occurrence of the tip effect, thereby inducing zinc ions to deposit in a relatively flat area, while adjusting the initial pH value of the electrolyte. Under the synergistic effect of the two, the effect of inhibiting dendrite growth and the occurrence of side reactions is achieved.

[0042] According to one embodiment of the present invention, when the electrolyte of the present invention is used in a battery, when the electrodes of the battery are metal electrodes other than zinc or the electrodes of the battery are metal electrodes other than zinc metal deposited, the additive VB6 cannot achieve the technical effect claimed by the present invention.

[0043] According to one embodiment of the present invention, the method for preparing the electrolyte comprises the following steps: adding zinc salt to water, stirring the solution until it becomes transparent, and adding vitamin B6 to obtain the electrolyte.

[0044] According to one embodiment of the present invention, the method for preparing the electrolyte comprises the following steps: using deionized water as a solvent, adding zinc sulfate, stirring the solution until transparent, preparing a 2-3 mol / L ZnSO4 electrolyte, adding vitamin B6, preparing an electrolyte containing 30-50 mM vitamin B6, and adjusting the pH value of the electrolyte to 3.2-3.4.

[0045] According to one embodiment of the present invention, the method for preparing the electrolyte comprises the following steps: using deionized water as a solvent, adding zinc sulfate, stirring the solution until transparent, preparing a 2 mol / L ZnSO4 electrolyte, adding vitamin B6, preparing an electrolyte containing 40 mM vitamin B6, and adjusting the pH value of the electrolyte to 3.3.

[0046] Another aspect of the present invention provides a zinc metal battery, including a positive electrode, a separator, a zinc metal negative electrode and the electrolyte described in the first embodiment. Since the application adopts all the technical solutions of the above electrolyte, it has at least all the beneficial effects brought by the technical solutions of the above embodiment.

[0047] Another aspect of the present invention further provides a zinc metal half-cell, which includes a zinc metal working electrode, a zinc metal counter / reference electrode, a separator, a battery shell, and the electrolyte described in the first embodiment.

[0048] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0050] Figure 1 The graphs are the cycle stability test graphs of the half-cells of Example 1, Examples 3-4 and Comparative Example 1.

[0051] Figure 2 This is a test diagram of the cycle stability of the half-cell of Comparative Example 2-3.

[0052] Figure 3 This is a cycle life test chart of the full batteries prepared in Example 2 and Comparative Example 4.

[0053] Figure 4 The double-layer capacitance test diagram of the half-cell of Example 1 and Comparative Example 1.

[0054] Figure 5 1 and 2 are X-ray diffraction diagrams of the products on the zinc foil surface after half-cell cycling of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0055] The words "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0056] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0057] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0058] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0059] Example 1

[0060] An electrolyte comprising the following components:

[0061] Zinc sulfate;

[0062] Vitamin B6;

[0063] water;

[0064] The concentration of zinc sulfate in the electrolyte is 2 mol L -1 ;

[0065] The concentration of vitamin B6 in the electrolyte is 40 mmol L -1 ;

[0066] Wherein, the pH value of the above electrolyte is 3.3.

[0067] The method for preparing the above-mentioned electrolyte comprises the following steps:

[0068] Zinc sulfate and vitamin B6 are mixed in water to obtain the above electrolyte.

[0069] A half-cell, the preparation method comprising the following steps:

[0070] A zinc foil with a diameter of 12 mm was used as the working electrode, a zinc foil with a diameter of 12 mm was used as the counter / reference electrode, a glass fiber separator and a standard CR2032 battery shell were used to assemble the battery, and 180 μL of the above electrolyte was added into the battery to obtain a half-cell.

[0071] Example 2

[0072] The electrolyte used in Example 2 is the same as that in Example 1. The difference between Example 2 and Example 1 is that the battery in Example 2 is a zinc metal battery, which uses a copper foil deposited with a certain amount of zinc as the negative electrode (the positive and negative electrode capacity ratio is 1:5).

[0073] Specific:

[0074] An electrolyte comprising the following components:

[0075] Zinc sulfate;

[0076] Vitamin B6;

[0077] water;

[0078] The concentration of zinc sulfate in the electrolyte is 2 mol L -1 ;

[0079] The concentration of vitamin B6 in the electrolyte is 40 mmol L -1 ;

[0080] Wherein, the pH value of the above electrolyte is 3.3.

[0081] The method for preparing the above-mentioned electrolyte comprises the following steps:

[0082] Zinc sulfate and vitamin B6 are mixed in water to obtain the above electrolyte.

[0083] A zinc metal battery, the preparation method comprising the following steps:

[0084] A zinc foil with a diameter of 12 mm was used as the negative electrode, a 12 mm active material VS2 electrode was used as the positive electrode, a glass fiber separator and a standard CR2032 battery shell were used to assemble a full battery, and 180 μL of the above electrolyte was added into the battery to obtain a zinc metal battery.

[0085] Example 3

[0086] The difference between Example 3 and Example 1 is that the concentration of vitamin B6 is different. In Example 3, the concentration of vitamin B6 is 10 mmol L -1 .

[0087] Specific:

[0088] An electrolyte comprising the following components:

[0089] Zinc sulfate;

[0090] Vitamin B6;

[0091] water;

[0092] The concentration of zinc sulfate in the electrolyte is 2 mol L -1 ;

[0093] The concentration of vitamin B6 in the electrolyte is 10 mmol L -1 ;

[0094] Wherein, the pH value of the above electrolyte is 3.3.

[0095] The method for preparing the above-mentioned electrolyte comprises the following steps:

[0096] Zinc sulfate and vitamin B6 are mixed in water to obtain the above electrolyte.

[0097] A half-cell, the preparation method comprising the following steps:

[0098] A zinc foil with a diameter of 12 mm was used as the working electrode, a zinc foil with a diameter of 12 mm was used as the counter / reference electrode, a glass fiber separator and a standard CR2032 battery shell were used to assemble the battery, and 180 μL of the above electrolyte was added into the battery to obtain a half-cell.

[0099] Example 4

[0100] The difference between Example 4 and Example 1 is that the concentration of vitamin B6 is different. The concentration of vitamin B6 in Example 4 is 70 mmol L -1 .

[0101] Specific:

[0102] An electrolyte comprising the following components:

[0103] Zinc sulfate;

[0104] Vitamin B6;

[0105] water;

[0106] The concentration of zinc sulfate in the electrolyte is 2 mol L -1 ;

[0107] The concentration of vitamin B6 in the electrolyte is 70 mmol L -1 ;

[0108] Wherein, the pH value of the above electrolyte is 3.3.

[0109] The method for preparing the above-mentioned electrolyte comprises the following steps:

[0110] Zinc sulfate and vitamin B6 are mixed in water to obtain the above electrolyte.

[0111] A half-cell, the preparation method comprising the following steps:

[0112] A zinc foil with a diameter of 12 mm was used as the working electrode, a zinc foil with a diameter of 12 mm was used as the counter / reference electrode, a glass fiber separator and a standard CR2032 battery shell were used to assemble the battery, and 180 μL of the above electrolyte was added into the battery to obtain a half-cell.

[0113] Comparative Example 1

[0114] The difference between Comparative Example 1 and Example 1 is that the electrolyte used in Comparative Example 1 does not contain vitamin B6.

[0115] Comparative Example 2

[0116] The difference between Comparative Example 2 and Example 1 is that vitamin B1 is used to replace vitamin B6 in Comparative Example 2, and the concentration of vitamin B1 in the electrolyte of Comparative Example 2 is also 40 mmol L -1 , the pH value of the electrolyte is 3.9.

[0117] Comparative Example 3

[0118] The difference between Comparative Example 3 and Example 1 is that vitamin B1 is used to replace vitamin B6 in Comparative Example 3, and the concentration of vitamin B1 in the electrolyte of Comparative Example 3 is also 40 mmol L -1 , the pH value of the electrolyte is 3.3.

[0119] Comparative Example 4

[0120] The electrolyte used in Comparative Example 4 is the same as that in Comparative Example 1. The difference between Comparative Example 4 and Comparative Example 1 is that the battery in Comparative Example 4 is a zinc metal battery, which uses a copper foil deposited with a certain amount of zinc as the negative electrode (the positive and negative electrode capacity ratio is 1:5).

[0121] Specific:

[0122] An electrolyte comprising the following components:

[0123] Zinc sulfate;

[0124] water;

[0125] The concentration of zinc sulfate in the electrolyte is 2 mol L -1 ;

[0126] Wherein, the pH value of the above electrolyte is 3.3.

[0127] The method for preparing the above-mentioned electrolyte comprises the following steps:

[0128] Mix zinc sulfate in water to obtain the above electrolyte.

[0129] A zinc metal battery, the preparation method comprising the following steps:

[0130] A zinc foil with a diameter of 12 mm was used as the negative electrode, a 12 mm active material VS2 electrode was used as the positive electrode, a glass fiber separator and a standard CR2032 battery shell were used to assemble a full battery, and 180 μL of the above electrolyte was added into the battery to obtain a zinc metal battery.

[0131] Performance Testing:

[0132] Test Example 1

[0133] The half-cell samples of Example 1, Examples 3-4 and Comparative Example 1 of the present invention were subjected to a cycle stability test (the test system used a Xinwei battery charge and discharge tester). The test results are as follows: Figure 1 The test conditions are a current density of 5 mAh cm -2 , constant current deposition-electrolysis capacity 5 mAh cm -2 , and conduct cycle performance tests.

[0134] from Figure 1 It can be seen that the half-cell prepared in Example 1 shows good stability in the cycle operation and can run continuously for 750 hours. However, the half-cell prepared in Comparative Example 1 without vitamin B6 short-circuited after 100 hours, which was mainly due to the excessive growth of dendrites. Different concentrations of vitamin B6 were added to Examples 3-4, and the cycle life of the half-cell was improved relative to that of Comparative Example 1, but it was still lower than the performance of Example 1. Example 1 used 40mM vitamin B6, which increased the cycle life of the half-cell by 750% relative to that of Examples 3-4. In summary, vitamin B6 as an electrolyte additive can effectively improve the cycle life of the battery, and the optimal concentration is 40mM.

[0135] Test Example 2

[0136] The half-cell samples prepared in Comparative Examples 2-3 of the present invention were subjected to a cycle stability test (the test system used a Xinwei battery charge and discharge tester). The test results are as follows: Figure 2 The test conditions are a current density of 5 mAh cm -2 , constant current deposition-electrolysis capacity 5 mAh cm -2 , and conduct cycle performance tests.

[0137] like Figure 2As shown, the half-cell prepared in Comparative Example 2 was short-circuited after only 143 hours of operation, indicating that not all B vitamins can improve battery performance. The half-cell prepared in Comparative Example 3 also failed after only 105 hours of operation, which also ruled out the influence of the initial pH value. This result verifies the particularity of vitamin B6.

[0138] Test Example 3

[0139] The full battery samples prepared in Example 2 of the present invention and Comparative Example 4 were subjected to full battery cycle life test (the test system used a Xinwei battery charge and discharge tester). The test results are as follows: Figure 3 The test condition is a current density of 1A g -1 , and conduct cycle performance tests.

[0140] like Figure 3 As shown, the full battery made from Example 2 can still maintain a capacity retention rate of 80.2% after 1000 cycles of stable operation. However, the full battery made from Comparative Example 4 showed a significant decrease in capacity after 230 cycles, which was mainly attributed to the occurrence of side reactions leading to a reduction in negative electrode active materials. This shows the potential for practical commercial application of Example 2 in zinc metal batteries.

[0141] Test Example 4

[0142] The double-layer capacitance of the electrode surface of the half-cell samples of Example 1 and Comparative Example 1 was tested (the test system was Chenhua electrochemical workstation). Figure 4 The test conditions are: cyclic voltammetry, the test range is -0.015-0.015V, and the scan rate is 12-20mV s -1 .

[0143] like Figure 4 As shown, the double-layer capacitance of the electrode surface in Example 1 is significantly lower than that in Comparative Example 1, indicating that vitamin B6 molecules are adsorbed on the electrode surface, thereby inducing zinc ions to deposit in relatively flat areas, ultimately achieving spontaneous adjustment of the interface roughness.

[0144] Test Example 5

[0145] The half-cell samples of Example 1 and Comparative Example 1 were heated to a current density of 2 mAh cm -2 , constant current deposition-electrolysis capacity 2 mAh cm -2 After 50 cycles under the same conditions, the products on the surface of zinc foil were qualitatively analyzed by X-ray diffraction.

[0146] like Figure 5As shown in the XRD test diagram, the signal of the surface by-product Zn4(OH)6SO4·5H2O (~8 degrees) in Example 1 is significantly lower than that in Comparative Example 1, which indicates that Example 1 has a significant inhibitory effect on the generation of by-products, thereby ensuring the electrode activity during the cycle and ultimately achieving an improvement in the overall performance of the battery.

[0147] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An electrolyte, characterized in that: Includes the following components: Zinc salts; Additives, wherein the additives include vitamin B6; water.

2. An electrolyte according to claim 1, characterized in that: The concentration ratio of the zinc salt to vitamin B6 is 200-220:4-4.

2.

3. An electrolyte according to claim 2, characterized in that: The concentration of vitamin B6 is greater than 10 mmol L -1 , less than 70mmol L -1 .

4. An electrolyte according to claim 3, characterized in that: The concentration of vitamin B6 is 30-40mmolL -1 .

5. An electrolyte according to claim 1, characterized in that: The pH of the electrolyte is 3.2-3.

4.

6. An electrolyte according to claim 1, characterized in that: The pH of the electrolyte is 3.3-3.

4.

7. An electrolyte according to claim 1, characterized in that: The zinc salt includes at least one of zinc chloride, zinc sulfate and zinc acetate.

8. A method for preparing the electrolyte according to any one of claims 1 to 7, characterized in that: The following steps are involved: The zinc salt and the additive are mixed in water to obtain the electrolyte.

9. A zinc metal battery, characterized in that: The invention comprises a positive electrode, a separator, a zinc metal negative electrode and the electrolyte according to any one of claims 1 to 7.

10. The zinc metal battery according to claim 9, characterized in that: The zinc metal negative electrode includes zinc foil.

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