Preparation method and application of zinc metal negative electrode with interface coating

Abstract

The invention discloses a preparation method of a zinc metal negative electrode with an interface coating, which comprises the following steps: adding biomass activated carbon into deionized water, uniformly stirring to obtain a biomass activated carbon dispersion liquid, then adding a poly (3, 4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution and a cosolvent to obtain a mixed solution, cleaning and drying a zinc foil, and drying to obtain the zinc metal negative electrode with the interface coating. And uniformly coating the mixed solution on the surface of the zinc foil, and drying to obtain the zinc foil. Compared with the prior art, the surface of the zinc metal negative electrode is coated with the activated carbon coated PEDOT: PSS composite film interface coating, the biomass activated carbon has a hierarchical porous structure and a high specific surface area, a large number of active sites are provided for Zn < 2 + >, and enough space is provided for growth of Zn < 2 + > dendritic crystals; the nitrogen-containing functional group in the biomass activated carbon can also improve the conductivity of the electrode material and adjust the transportation and deposition of Zn < 2 + >. The zinc metal negative electrode has good cycle stability, and the preparation process is clean and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of aqueous zinc ion batteries, and in particular relates to a preparation method and application of a zinc metal negative electrode with an interface coating. Background Art

[0002] In recent years, energy storage has become a serious global problem due to the growing energy demand and irreversible fossil fuel consumption, as well as the corresponding environmental pollution. The development of advanced energy storage devices is considered to be the most critical and effective solution strategy at present. As we all know, lithium-ion batteries are the most commonly used energy storage devices in our daily life and transportation, such as electric vehicles and hybrid vehicles. However, the limited lithium resources, the rising manufacturing costs, and the flammable and toxic properties of electrolytes in lithium-ion batteries have hindered the large-scale application of lithium-ion batteries.

[0003] Rechargeable aqueous zinc-ion batteries have the advantages of high specific capacity, environmental protection, low cost and high safety. They are an ideal green battery system and one of the most promising energy storage devices for large-scale energy storage. They are expected to be applied in the field of clean energy. However, there are some problems with using zinc metal directly as the negative electrode: (1) During the repeated charge and discharge process of the battery, zinc ions and metallic zinc repeatedly deposit and dissolve on the surface of the negative electrode, forming dendritic precipitates. As the precipitates grow, they eventually become zinc dendrites. These zinc dendrites can easily pierce the diaphragm and cause battery short circuits. At the same time, they can cause uneven thickness distribution of the zinc electrode and cause electrode deformation, resulting in a decrease in the capacity of the zinc-ion battery. (2) Hydrogen evolution reaction is an inevitable side reaction in zinc metal batteries, which consumes part of the charge and reduces the coulombic efficiency of the battery. In addition, the evolved hydrogen gas will increase the pressure in the closed battery system, causing battery expansion. (3) The zinc metal in the electrolyte will undergo chemical and electrochemical corrosion. These problems limit the application of aqueous zinc-ion batteries. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned shortcomings existing when zinc metal is directly used as a negative electrode in existing aqueous zinc ion batteries, and to provide a method for preparing a zinc metal negative electrode with an interface coating.

[0005] To solve the above-mentioned purpose, the present invention adopts the following technical solution:

[0006] A method for preparing a zinc metal negative electrode with an interface coating comprises the following steps:

[0007] (1) adding biomass activated carbon into deionized water and stirring evenly to obtain a biomass activated carbon dispersion;

[0008] (2) adding a poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS) aqueous solution and a co-solvent to the biomass activated carbon dispersion, stirring evenly to obtain a mixed solution;

[0009] (3) After the zinc foil is cleaned and dried, the mixed solution obtained in step (2) is evenly coated on the surface of the zinc foil, and after drying, a zinc metal negative electrode with an interface coating is obtained.

[0010] Furthermore, in step (1), the preparation method of the biomass activated carbon is as follows: adding red vine to deionized water, heating at 100°C for 2h, filtering, and drying to obtain red vine residues, grinding the red vine residues, and carbonizing at 600°C for 2h under an argon atmosphere to obtain red vine carbide, mixing the red vine carbide with an activator and dispersing them in deionized water, stirring them thoroughly, and freeze-drying them, and then carbonizing them at 800°C for 2h under an argon atmosphere, and finally centrifuging the product for cleaning and drying to obtain biomass activated carbon.

[0011] Furthermore, in step (1), the amount of the biomass activated carbon and deionized water is: 1g biomass activated carbon: 30-40mL deionized water.

[0012] Furthermore, in step (2), the co-solvent is DMSO (dimethyl sulfoxide).

[0013] Furthermore, in step (2), the volume ratio of the co-solvent to deionized water is 3:20.

[0014] Furthermore, in step (2), the mass concentration of the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution is 1.5%, and the mass ratio of the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution to the biomass activated carbon is (50-70):1.

[0015] Furthermore, in step (3), the zinc foil has a thickness of 100 μm.

[0016] Furthermore, in step (3), the coating thickness is 20-30 μm.

[0017] Furthermore, in step (3), the coating method is spin coating, dipping, casting or spraying, preferably casting.

[0018] Furthermore, in step (3), the drying method is natural drying at room temperature, and the drying time is greater than 8 hours.

[0019] The zinc metal negative electrode with interface coating is prepared by the above method.

[0020] Application of the zinc metal negative electrode with interface coating prepared by the above method in zinc ion batteries.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention coats an activated carbon@PEDOT:PSS composite film interface coating on the surface of the zinc metal negative electrode. The biomass activated carbon has a hierarchical porous structure and a high specific surface area. 2+ It provides a large number of active sites and provides Zn 2+ The growth of dendrites provides enough space. The nitrogen-containing functional groups in biomass activated carbon can also improve the conductivity of electrode materials and regulate the Zn 2+ transport and deposition of Zn; PEDOT:PSS can balance the electric field distribution and induce Zn to preferentially deposit on the (002) crystal plane, inhibiting corrosion reactions and reducing by-products.

[0023] (2) The present invention coats an activated carbon@PEDOT:PSS composite film interface coating on the surface of the zinc metal negative electrode, ingeniously utilizing the easy film-forming property of the PEDOT:PSS aqueous solution, without the need to use polymer binders such as PVDF and CMC.

[0024] (3) The zinc metal negative electrode with an interface coating prepared by the present invention has good cycle stability and safety performance, and the preparation process is clean, environmentally friendly and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a surface scanning electron microscope image of the zinc metal negative electrode with the interface coating prepared in Example 1;

[0026] Figure 2 This is a cross-sectional scanning electron microscope image of the zinc metal negative electrode with the interface coating prepared in Example 1;

[0027] Figure 3 The surface scanning electron microscope images of the zinc metal negative electrodes prepared in Example 1 and Comparative Example 1 after being immersed in a 2M ZnSO4 electrolyte for 7 days;

[0028] Figure 4 The zinc metal negative electrode prepared in Example 1 and Comparative Example 1 and 2M ZnSO 4 The contact angle of the electrolyte;

[0029] Figure 5 The symmetrical battery assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 、0.5mAhcm -2 Long cycle performance test results under conditions;

[0030] Figure 6 The symmetrical battery assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 、1mAh cm-2 Long cycle performance test results under conditions;

[0031] Figure 7 The half-cell assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 , 0.5mAh cm -2 Long cycle performance test results under conditions;

[0032] Figure 8 The half-cell assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 、1mAh cm -2 Long cycle performance test results under conditions;

[0033] Fig. 9 The full battery assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -1 Long cycle performance test results under 3.5°C. DETAILED DESCRIPTION

[0034] The specific implementation modes of the present invention are described below in conjunction with the accompanying drawings and examples. However, the following examples are only used to illustrate the present invention in detail and do not limit the scope of the present invention in any way.

[0035] In the following examples, the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS) aqueous solution used has a mass concentration of 1.5% and is purchased from Sigma-Aldrich, but is not limited thereto.

[0036] Example 1

[0037] A method for preparing a zinc metal negative electrode with an interface coating comprises the following steps:

[0038] (1) Preparation of biomass activated carbon: Adding red vine to deionized water, heating in a water bath at 100°C for 2 h, filtering and drying to obtain red vine residues, grinding the red vine residues, heating to 600°C at a heating rate of 5°C / min under an argon atmosphere, and carbonizing for 2 h to obtain red vine carbide, mixing the red vine carbide with an activator KOH (mass ratio of 1:1) and dispersing it in deionized water, ultrasonicating for 30 min, stirring for 2 h, and then freeze-drying for 24 h, and then heating to 800°C at a heating rate of 5°C / min under an argon atmosphere, and carbonizing for 2 h. Finally, the product was centrifuged and washed with deionized water, and dried to obtain biomass activated carbon;

[0039] (2) Add 10 mg of biomass activated carbon into 300 μL of deionized water and stir ultrasonically for 10 min to obtain a biomass activated carbon dispersion;

[0040] (3) Add 600 μL of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution (600 mg) and 45 μL of co-solvent DMSO to the biomass activated carbon dispersion and stir for 24 h to obtain a mixed solution;

[0041] (4) A zinc foil with a thickness of 100 μm was cut into a size of 5 cm×10 cm, the surface was ultrasonically cleaned with ethanol and dried, and then the mixed solution prepared in step (3) was evenly coated on the surface of the zinc foil. After drying at room temperature for 8 hours, a zinc metal negative electrode with an interface coating was obtained.

[0042] Comparative Example 1

[0043] Preparation method of zinc metal negative electrode: cut zinc foil with a thickness of 100 μm into a size of 5 cm×10 cm, clean the surface with ethanol ultrasonically and dry it to obtain the zinc metal negative electrode.

[0044] Figure 1 This is a surface scanning electron microscope image of the zinc metal negative electrode with the interface coating prepared in Example 1. As shown in the figure, the surface of the interface coating of the zinc metal negative electrode is relatively smooth.

[0045] Figure 2 This is a cross-sectional scanning electron microscope image of the zinc metal negative electrode with the interface coating prepared in Example 1. It can be seen that the thickness of the interface coating is about 25 μm.

[0046] 1. Corrosion resistance test:

[0047] In order to test the corrosion resistance of the interface coating to the electrolyte, the zinc metal negative electrodes prepared in Example 1 and Comparative Example 1 were immersed in 2M ZnSO 4 The samples were placed in the electrolyte for 7 days and then taken out and observed under a scanning electron microscope.

[0048] Figure 3 The zinc metal negative electrode prepared in Example 1 and Comparative Example 1 was heated to 2M ZnSO 4 Scanning electron microscope image of the surface after immersion in electrolyte for 7 days, Figure 3 A is the zinc metal negative electrode prepared in Example 1, Figure 3 B is the zinc metal negative electrode prepared in Comparative Example 1. As shown in the figure, obvious by-products can be observed on the bare zinc surface of Comparative Example 1, and the corrosion is serious. However, there is no obvious change on the surface of the zinc metal negative electrode prepared in Example 1, indicating that the corrosion resistance is good and the occurrence of side reactions can be effectively reduced.

[0049] 2. Contact angle test:

[0050] Put 2M ZnSO 4 The electrolyte was dropped onto the surfaces of the zinc metal negative electrodes prepared in Example 1 and Comparative Example 1, respectively, and contact angle tests were performed.

[0051] Figure 4 The zinc metal negative electrode prepared in Example 1 and Comparative Example 1 and 2M ZnSO 4 The contact angle of the electrolyte, where Figure 4 A is the zinc metal negative electrode prepared in Comparative Example 1, Figure 4 B is the zinc metal negative electrode prepared in Example 1. As can be seen from the figure, the contact angles of the zinc metal negative electrodes prepared in Comparative Example 1 and Example 1 are 91° and 28° respectively. The contact angle of the zinc metal negative electrode prepared in Example 1 is significantly reduced, indicating that the activated carbon@PEDOT:PSS composite film interface coating has very good hydrophilicity, which can effectively improve the electrolyte wettability and make Zn 2+ The deposition is more uniform.

[0052] 3. Symmetrical battery test:

[0053] The zinc metal negative electrodes prepared in Example 1 and Comparative Example 1 were cut into circular electrodes with a diameter of 12 mm using a button battery slicer, and then assembled into symmetrical batteries. Specific method: Place the zinc negative electrode electrodes on both sides of the diaphragm, add steel sheets and springs, cover the positive and negative battery shells, put them into a sealing machine, and seal them at a pressure of 50 MPa to complete the assembly of the symmetrical battery. The electrolyte uses 2M ZnSO 4 At a current density of 1 mA cm -2 , area capacity 0.5mAh cm -2 Symmetrical battery charge and discharge long cycle test was carried out under the conditions of

[0054] Figure 5 The symmetrical battery assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 、0.5mAhcm -2 The long cycle performance test results under the conditions show that the bare zinc symmetric battery assembled with the zinc metal negative electrode of comparative example 1 had a short circuit in only 90 hours, while the cycle life of the symmetric battery assembled with the zinc metal negative electrode of embodiment 1 can reach 2200 hours, which is 20 times that of bare zinc, and the polarization voltage is also reduced from 62mV of bare zinc to 40mV. This shows that the activated carbon@PEDOT:PSS composite film interface coating can effectively promote Zn 2+ Stable deposition and dissolution, with excellent electrochemical stability.

[0055] Figure 6 The symmetrical battery assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 、1mAh cm -2 The long cycle performance test results under the conditions show that when the current density and area capacity increase to 5mAcm -2 and 1mAhcm-2 Under the protection of the activated carbon@PEDOT:PSS composite film interface coating, the cycle life of the symmetrical battery assembled using the zinc metal negative electrode of Example 1 can reach 1200h.

[0056] 4. Half-battery test:

[0057] The zinc metal negative electrodes prepared in Example 1 and Comparative Example 1 were cut into circular electrodes with a diameter of 12 mm using a button cell slicer as the zinc negative electrode plates; copper foil with a thickness of 100 μm was cut into circular electrodes with a diameter of 12 mm as the positive electrode plates, which were assembled into half-cells with the zinc negative electrode plates of Example 1 and Comparative Example 1, respectively. The electrolyte used was 2M ZnSO 4 At a current density of 1 mA cm -2 , area capacity 0.5mAh cm -2 Half-cell charge and discharge long cycle test was carried out under the conditions of

[0058] Figure 7 The half-cell assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 , 0.5mAh cm -2 The long cycle performance test results under the conditions are shown in the figure. The Zn|Cu half-cell assembled with the zinc metal negative electrode of comparative example 1 began to have voltage instability at around 500 cycles, and the charge and discharge process was irreversible. However, the charge and discharge process of the activated carbon@PEDOT:PSS|Cu half-cell assembled with the zinc metal negative electrode of example 1 has been stable for more than 1500 cycles, and the coulomb efficiency is maintained at more than 99%. This is because the interface coating of the activated carbon@PEDOT:PSS composite film can promote the Zn 2+ The uniform distribution of current and uniform deposition of Zn improve the coulombic efficiency and cycle life of the half-cell.

[0059] Figure 8 The half-cell assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -2 、1mAh cm -2 The long cycle performance test results under the conditions show that the current density and area capacity increase to 5mAcm -2 and 1mAh cm -2 Under the protection of the activated carbon@PEDOT:PSS composite film interface coating, the half-cell assembled with the zinc metal negative electrode of Example 1 was stably cycled for 3000 cycles.

[0060] 5. Full battery test:

[0061] The zinc metal negative electrodes prepared in Example 1 and Comparative Example 1 were cut into circular electrodes with a diameter of 12 mm using a button battery slicer as zinc negative electrode electrodes, and then respectively 2 Assemble the full battery. The electrolyte uses 2M ZnSO 4 +0.1MMnSO 4 . In 1Ag -1 The full battery charge and discharge long cycle test was carried out at a current density of 1.

[0062] Fig. 9 The full battery assembled with the zinc metal negative electrode of Example 1 and Comparative Example 1 was -1 The long cycle performance test results under the conditions of 2 The full battery has a higher initial specific capacity (305mAh g -1 ), after 1000 cycles, the specific capacity still remains at 248 mAh g -1 The capacity retention rate is 81.3%, which is much higher than that of the Zn|MnO assembled with the zinc metal negative electrode of Comparative Example 1. 2 This further demonstrates that the interface of activated carbon@PEDOT:PSS composite membrane can optimize the Zn 2+ storage and deposition.

Claims

1. A method for preparing a zinc metal negative electrode with an interface coating, characterized in that: The steps include: (1) adding biomass activated carbon into deionized water and stirring evenly to obtain a biomass activated carbon dispersion; (2) adding a poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution and a co-solvent to the biomass activated carbon dispersion, stirring evenly to obtain a mixed solution; (3) After the zinc foil is cleaned and dried, the mixed solution obtained in step (2) is evenly coated on the surface of the zinc foil, and after drying, a zinc metal negative electrode with an interface coating is obtained.

2. The method for preparing a zinc metal negative electrode having an interface coating as claimed in claim 1, characterized in that: In step (1), the preparation method of the biomass activated carbon is as follows: adding red vine to deionized water, heating at 100°C for 2h, filtering, and drying to obtain red vine residues, grinding the red vine residues, and carbonizing at 600°C for 2h under an argon atmosphere to obtain red vine carbide, mixing the red vine carbide with an activator and dispersing them in deionized water, stirring them thoroughly, and freeze-drying them, and then carbonizing them at 800°C for 2h under an argon atmosphere, and finally centrifuging the product for cleaning and drying to obtain biomass activated carbon.

3. The method for preparing a zinc metal negative electrode having an interface coating as claimed in claim 1, characterized in that: In step (1), the amount of biomass activated carbon and deionized water is: 1g biomass activated carbon: 30-40mL deionized water.

4. The method for preparing a zinc metal negative electrode having an interface coating according to claim 1, characterized in that: In step (2), the co-solvent is DMSO.

5. The method for preparing a zinc metal negative electrode having an interface coating as claimed in claim 1, characterized in that: In step (2), the volume ratio of the co-solvent to deionized water is 3:

20.

6. The method for preparing a zinc metal negative electrode with an interface coating as claimed in claim 1, characterized in that: In step (2), the mass concentration of the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution is 1.5%, and the mass ratio of the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution to the biomass activated carbon is (50-70):

1.

7. The method for preparing a zinc metal negative electrode having an interface coating as claimed in claim 1, characterized in that: In step (3), the zinc foil has a thickness of 100 μm.

8. The method for preparing a zinc metal negative electrode having an interface coating according to any one of claims 1 to 7, characterized in that: In step (3), the coating thickness is 20-30 μm.

9. A zinc metal negative electrode with an interface coating prepared by the method according to any one of claims 1 to 8.

10. Use of the zinc metal negative electrode with an interface coating prepared by the method according to any one of claims 1 to 8 in a zinc ion battery.

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