Preparation and application of a composite zinc anode modified by hydrated molybdenum oxide

Abstract

The invention belongs to the field of aqueous ion batteries, in particular to the preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide and its application. The preparation method comprises the following steps: S1: preparing an electrodeposition solution, weighing ammonium molybdate into a volumetric flask, using water as a solvent, performing constant volume, and setting aside; S2: preparing a zinc sheet substrate, cutting a metal zinc sheet into zinc sheets of the same size, washing the surface of the zinc sheet with deionized water and ethanol in turn, drying under vacuum for ten minutes, and ensuring that the deposition area is consistent; S3: preparing an HMoOx / Zn composite negative electrode. The invention controls the thickness of hydrated molybdenum oxide formed on the surface of the zinc sheet by deposition time, forms an amorphous hydrated molybdenum oxide modification layer on the zinc surface, has stable chemical properties, effectively guides zinc ion deposition and shedding, inhibits the generation of zinc dendrites, thereby improving its electrochemical properties, has good specific capacity and cycle stability, is simple in synthesis method, low in cost, and has high repeatability of electrode performance.

Description

Technical Field

[0001] The invention relates to the technical field of aqueous ion batteries, and in particular to the preparation and application of a composite zinc negative electrode modified with hydrated molybdenum oxide. Background Art

[0002] With the development of the times, today's energy demand problem is becoming more and more urgent, which has made people turn their attention to clean and renewable energy, such as solar energy, wind energy, and hydropower. The storage and conversion of these energy sources is an important prerequisite for their large-scale application. At present, lithium-ion batteries are the most widely used secondary batteries. Lithium-ion batteries use carbon materials as negative electrodes and lithium-containing compounds as positive electrodes. There is no metallic lithium, only lithium ions. This is a lithium-ion battery. Lithium-ion batteries refer to the general term for batteries with lithium ion embedded compounds as positive electrode materials. The charging and discharging process of lithium-ion batteries is the embedding and deintercalation process of lithium ions. In the process of embedding and deintercalation of lithium ions, it is accompanied by the embedding and deintercalation of equivalent electrons to lithium ions (it is customary to use embedding or deintercalation for the positive electrode, and insertion or deintercalation for the negative electrode). During the charging and discharging process, lithium ions are embedded / deintercalated and inserted / deintercalated back and forth between the positive and negative electrodes, which is vividly called a "rocking chair battery", but it has high costs and safety issues. In comparison, aqueous zinc-ion batteries have good stability, high safety and low pollution, so they have attracted the attention of researchers.

[0003] The main components of aqueous zinc-ion batteries include: positive electrode, negative electrode, electrode liquid and diaphragm. The importance of negative electrode materials is self-evident. It is an irreplaceable component of the entire zinc battery system and affects the working performance of the battery. Zinc metal is one of the most promising electrode materials for application research in aqueous zinc-ion batteries. Although zinc metal has many advantages as a negative electrode, its application has not yet achieved the best results and there are still some problems. During the charging / discharging process, the unevenness of the zinc metal surface will lead to the formation of dendrites, which will further pierce the battery diaphragm and cause internal short circuit failure. The zinc foil will be passivated when in contact with water, which will affect the electrochemical performance of the aqueous zinc-ion battery. The hydrogen evolution reaction will also cause the battery to foam, swell, and rupture, and eventually lead to electrolyte leakage. In summary, during the charging and discharging process, the zinc metal negative electrode has disadvantages such as dendrites, passivation and hydrogen evolution, which can easily lead to a decrease in the battery cycle life. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a preparation and application of a composite zinc negative electrode modified with hydrated molybdenum oxide.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A preparation method of a composite zinc negative electrode modified with hydrated molybdenum oxide comprises the following steps:

[0007] S1: Preparation of electrodeposition solution: weigh ammonium molybdate into a volumetric flask, use water as solvent, make up to volume, and set aside;

[0008] S2: Prepare a zinc sheet substrate, cut the metal zinc sheet into zinc sheets of the same size, wash the surface of the zinc sheet with deionized water and ethanol in turn, dry it under vacuum for ten minutes, and ensure that the deposition area is consistent;

[0009] S3: Prepare HMoOx / Zn composite negative electrode, and perform electrodeposition through a three-electrode system, using calomel electrode as reference electrode, Pt sheet as counter electrode, the solution obtained in step S1 as deposition electrolyte, and zinc foil treated in step S2 as working electrode, and perform constant potential deposition under constant potential to coat the modified layer of HMoOx on the zinc foil, take it out, rinse it with deionized water, and dry it under vacuum for standby use.

[0010] Preferably, in S1, the concentration of ammonium molybdate is 1-10 mmol / L.

[0011] Preferably, in S2, the thickness of the zinc sheet is 0.03-2 mm.

[0012] Preferably, in S2, the marked deposition area is 1-9 cm2.

[0013] Preferably, in S3, the constant voltage deposition voltage used is one of the potentials between -2V and 0V.

[0014] Preferably, in S3, the deposition time is 1-300s.

[0015] Preferably, in S2, the cut zinc sheet has a length of 1-10 cm and a width of 1-10 cm.

[0016] The present invention also proposes an application of a composite zinc negative electrode modified by hydrated molybdenum oxide, and the composite zinc negative electrode modified by hydrated molybdenum oxide is used in an aqueous zinc ion battery.

[0017] In the present invention, the preparation and application of the composite zinc negative electrode modified by hydrated molybdenum oxide have the following beneficial effects:

[0018] 1. The present invention adopts constant potential for electrodeposition to form an amorphous hydrated molybdenum oxide modified thin layer on the surface of the zinc sheet, and this method can control the thickness of the hydrated molybdenum oxide formed on the surface of the zinc sheet by the deposition time.

[0019] 2. The present invention forms an amorphous hydrated molybdenum oxide modification layer on the zinc surface, which has stable chemical properties. The hydrated molybdenum oxide can interact with the electrolyte through its outer surface, transport the electrolyte to the interior of the material, reduce the direct contact between the water in the electrolyte and the zinc negative electrode, thereby alleviating the corrosion phenomenon on the surface of the negative electrode sheet. In addition, it effectively guides the deposition and shedding of zinc ions, inhibits the formation of zinc dendrites, and thus improves its electrochemical properties.

[0020] 3. The present invention has good specific capacity and cycle stability and can be used as the negative electrode of aqueous zinc ion batteries.

[0021] 4. The synthesis method of the present invention is simple, low-cost, and has high repeatability of electrode performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram of HMoOx / Zn composite electrodes at different deposition times prepared by a composite zinc negative electrode modified by hydrated molybdenum oxide proposed in the present invention;

[0023] Figure 2 This is a morphology diagram of a HMoOx / Zn composite electrode prepared from a composite zinc negative electrode modified with hydrated molybdenum oxide proposed in the present invention;

[0024] Figure 3 A cyclic stability curve of a HMoOx / Zn composite electrode prepared by a composite zinc negative electrode modified by hydrated molybdenum oxide proposed in the present invention in a symmetrical battery;

[0025] Figure 4 This is an electrochemical performance diagram of the HMoOx / Zn composite electrode prepared by a composite zinc negative electrode modified with hydrated molybdenum oxide proposed in the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Embodiment 1

[0028] Reference Figure 1-Figure 4 , a composite zinc negative electrode modified with hydrated molybdenum oxide is prepared, comprising the following steps:

[0029] S1: Preparation of electrodeposition solution: weigh ammonium molybdate into a volumetric flask, use water as solvent, make up to volume, and set aside;

[0030] S2: Prepare a zinc sheet substrate, cut the metal zinc sheet into zinc sheets of the same size, wash the surface of the zinc sheet with deionized water and ethanol in turn, dry it under vacuum for ten minutes, and ensure that the deposition area is consistent;

[0031] S3: Prepare HMoOx / Zn composite negative electrode, and perform electrodeposition through a three-electrode system, using calomel electrode as reference electrode, Pt sheet as counter electrode, the solution obtained in step S1 as deposition electrolyte, and zinc foil treated in step S2 as working electrode, and perform constant potential deposition under constant potential to coat the modified layer of HMoOx on the zinc foil, take it out, rinse it with deionized water, and dry it under vacuum for standby use.

[0032] In this embodiment, in S1, the concentration of ammonium molybdate is 1 mmol / L.

[0033] In this embodiment, in S2, the thickness of the zinc sheet is 0.03 mm.

[0034] In this embodiment, in S2, the marked deposition area is 1 cm2.

[0035] In this embodiment, in S3, the constant voltage deposition voltage used is one of the potentials of -2V.

[0036] In this embodiment, in S3, the deposition time is 1 s.

[0037] In this embodiment, in S2, the cut zinc sheet has a length of 1 cm and a width of 1 cm.

[0038] This embodiment also proposes an application of a composite zinc negative electrode modified with hydrated molybdenum oxide, and the composite zinc negative electrode modified with hydrated molybdenum oxide is used in an aqueous zinc ion battery.

[0039] In this embodiment, Figure 1 The deposition process of the composite zinc anode modified with hydrated molybdenum oxide is Figure 1 It can be seen that the zinc composite negative electrode modified with hydrated molybdenum oxide is deposited on the bare zinc substrate, and the silver-white substrate changes to a brown-red film. In addition, as the deposition time increases, its color becomes darker, indicating that the hydrated molybdenum oxide film has been deposited on the bare zinc substrate.

[0040] Figure 2 This is a scanning electron microscope (SEM) photo of a zinc negative electrode modified with hydrated molybdenum oxide. Compared with bare zinc, the surface of the composite zinc negative electrode modified with hydrated molybdenum oxide is smoother. The cross-sectional SEM can clearly distinguish that a thin layer of hydrated molybdenum oxide is attached to the surface of the zinc foil.

[0041] Figure 3 The electrochemical performance of the zinc negative electrode modified with hydrated molybdenum oxide in a symmetric battery. Compared with bare zinc, the voltage window of exfoliation and deposition of the composite zinc negative electrode modified with hydrated molybdenum oxide is narrower and the cycle stability is higher, indicating that the hydrated molybdenum oxide modification layer can effectively guide the deposition and shedding of zinc ions on the surface of the zinc negative electrode, thereby improving the electrode cycle stability.

[0042] Figure 4The electrochemical performance of the zinc negative electrode modified with hydrated molybdenum oxide. Using the composite zinc metal modified with hydrated molybdenum oxide as the negative electrode and MnO2 as the positive electrode in the button cell, it can be seen that the zinc negative electrode modified with hydrated molybdenum oxide shows excellent electrochemical performance.

[0043] Among the modified materials, amorphous materials are selected as protective layers because of their chemical stability and ability to withstand harsh battery operating conditions. Many metal oxides can be transformed into hydrated metal oxides in an aqueous electrochemical environment and then serve as active phases in electrochemical processes. Hydrated molybdenum oxide (HMoOx) confines structural water within its volume. As an electrode coating, hydrous molybdenum oxide can interact with the electrolyte not only through its outer surface, but also through its aqueous inner surface, thereby transporting the electrolyte into the interior of the material. Compared with physical coating, electrodeposition is a unique technology that can achieve excellent coverage and conformal deposition. The thickness of the deposited film can be precisely controlled at the nanoscale level. The electrochemical performance of the zinc negative electrode is further improved by electrodepositing ultra-thin coatings.

[0044] The purpose of the present invention is to cover a layer of ultra-thin hydrated molybdenum oxide coating on the surface of a zinc sheet by a constant potential deposition method to prepare a hydrated molybdenum oxide modified zinc composite material with excellent electrochemical performance. The HMoOx / Zn composite negative electrode of the present invention is composed of a zinc foil substrate and an amorphous HMoOx modified layer, which solves the problems of hydrogen evolution, passivation, corrosion and dendrites, and gives the zinc metal negative electrode more excellent electrochemical performance. The synthesis method of the HMoOx / Zn composite negative electrode involved in the present invention has the advantages of simplicity, low cost and good repeatability.

[0045] The present invention adopts constant potential for electrodeposition to form an amorphous hydrated molybdenum oxide modified thin layer on the surface of the zinc sheet, and the method can control the thickness of the hydrated molybdenum oxide formed on the surface of the zinc sheet by the deposition time. The present invention forms an amorphous hydrated molybdenum oxide modified layer on the zinc surface, which has stable chemical properties. The hydrated molybdenum oxide can interact with the electrolyte through its outer surface to transport the electrolyte to the inside of the material. The direct contact between water in the electrolyte and the zinc negative electrode is reduced, thereby alleviating the corrosion phenomenon on the surface of the negative electrode sheet. In addition, the deposition and shedding of zinc ions are effectively guided, and the generation of zinc dendrites is suppressed, thereby improving its electrochemical performance. The present invention has good specific capacity and cycle stability, and can be used as the negative electrode of an aqueous zinc ion battery. The synthesis method of the present invention is simple, the cost is low, and the electrode performance repeatability is high.

[0046] Embodiment 2

[0047] A preparation method of a composite zinc negative electrode modified with hydrated molybdenum oxide comprises the following steps:

[0048] S1: Preparation of electrodeposition solution: weigh ammonium molybdate into a volumetric flask, use water as solvent, make up to volume, and set aside;

[0049] S2: Prepare a zinc sheet substrate, cut the metal zinc sheet into zinc sheets of the same size, wash the surface of the zinc sheet with deionized water and ethanol in turn, dry it under vacuum for ten minutes, and ensure that the deposition area is consistent;

[0050] S3: Prepare HMoOx / Zn composite negative electrode, and perform electrodeposition through a three-electrode system, using calomel electrode as reference electrode, Pt sheet as counter electrode, the solution obtained in step S1 as deposition electrolyte, and zinc foil treated in step S2 as working electrode, and perform constant potential deposition under constant potential to coat the modified layer of HMoOx on the zinc foil, take it out, rinse it with deionized water, and dry it under vacuum for standby use.

[0051] In this embodiment, in S1, the concentration of ammonium molybdate is 5 mmol / L.

[0052] In this embodiment, in S2, the thickness of the zinc sheet is 1 mm.

[0053] In this embodiment, in S2, the marked deposition area is 5 cm2.

[0054] In this embodiment, in S3, the constant voltage deposition voltage used is one of the intermediate potentials of -1V.

[0055] In this embodiment, in S3, the deposition time is 150 s.

[0056] In this embodiment, in S2, the cut zinc sheet is 5 cm long and 5 cm wide.

[0057] This embodiment also proposes an application of a composite zinc negative electrode modified with hydrated molybdenum oxide, and the composite zinc negative electrode modified with hydrated molybdenum oxide is used in an aqueous zinc ion battery.

[0058] Embodiment 3

[0059] A preparation method of a composite zinc negative electrode modified with hydrated molybdenum oxide comprises the following steps:

[0060] S1: Preparation of electrodeposition solution: weigh ammonium molybdate into a volumetric flask, use water as solvent, make up to volume, and set aside;

[0061] S2: Prepare a zinc sheet substrate, cut the metal zinc sheet into zinc sheets of the same size, wash the surface of the zinc sheet with deionized water and ethanol in turn, dry it under vacuum for ten minutes, and ensure that the deposition area is consistent;

[0062] S3: Prepare HMoOx / Zn composite negative electrode, and perform electrodeposition through a three-electrode system, using calomel electrode as reference electrode, Pt sheet as counter electrode, the solution obtained in step S1 as deposition electrolyte, and zinc foil treated in step S2 as working electrode, and perform constant potential deposition under constant potential to coat the modified layer of HMoOx on the zinc foil, take it out, rinse it with deionized water, and dry it under vacuum for standby use.

[0063] In this embodiment, in S1, the concentration of ammonium molybdate is 10 mmol / L.

[0064] In this embodiment, in S2, the thickness of the zinc sheet is 2 mm.

[0065] In this embodiment, in S2, the marked deposition area is 9 cm2.

[0066] In this embodiment, in S3, the constant voltage deposition voltage used is one of the potentials of 0V.

[0067] In this embodiment, in S3, the deposition time is 300 s.

[0068] In this embodiment, in S2, the cut zinc sheet has a length of 10 cm and a width of 10 cm.

[0069] This embodiment also proposes an application of a composite zinc negative electrode modified with hydrated molybdenum oxide, and the composite zinc negative electrode modified with hydrated molybdenum oxide is used in an aqueous zinc ion battery.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide, characterized in that: The following steps are involved: S1: Preparation of electrodeposition solution: weigh ammonium molybdate into a volumetric flask, use water as solvent, make up to volume, and set aside; S2: Prepare a zinc sheet substrate, cut the metal zinc sheet into zinc sheets of the same size, wash the surface of the zinc sheet with deionized water and ethanol in turn, dry it under vacuum for ten minutes, and ensure that the deposition area is consistent; S3: Prepare a HMoOx / Zn composite negative electrode, and perform electrodeposition through a three-electrode system, using a calomel electrode as a reference electrode, a Pt sheet as a counter electrode, the solution obtained in step S1 as a deposition electrolyte, and the zinc foil treated in step S2 as a working electrode. Perform constant potential deposition under constant potential to coat the modified layer of HMoOx on the zinc foil, take it out, rinse it with deionized water, and dry it under vacuum for standby use.

2. The preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide according to claim 1, characterized in that: In the S1, the concentration of ammonium molybdate is 1-10 mmol / L.

3. The preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide according to claim 2, characterized in that: In S2, the thickness of the zinc sheet is 0.03-2 mm.

4. The preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide according to claim 3, characterized in that: In S2, the deposition area of ​​the marker is 1-9 cm 2 .

5. The preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide according to claim 4, characterized in that: In S3, the constant potential deposition voltage used is one of the potentials between -2V and 0V.

6. The preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide according to claim 5, characterized in that: In S3, the deposition time is 1-300s.

7. The preparation of a composite zinc negative electrode modified with hydrated molybdenum oxide according to claim 6, characterized in that: In S2, the cut zinc sheet has a length of 1-10 cm and a width of 1-10 cm.

8. An application of a composite zinc negative electrode modified with hydrated molybdenum oxide, characterized in that: The hydrated molybdenum oxide-modified composite zinc negative electrode prepared from the hydrated molybdenum oxide-modified composite zinc negative electrode according to any one of claims 1 to 7 is used in an aqueous zinc ion battery.

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