A zinc negative electrode with a double protective layer and a preparation method thereof

Abstract

The present invention discloses a double-layer protective layer for a zinc negative electrode and a preparation method thereof. The preparation method comprises: subjecting cleaned zinc metal foil to a hydrothermal treatment to obtain a modified zinc metal foil; the original zinc metal foil is a commercial zinc metal foil, and the hydrothermal treatment is performed under a set mixed solution, a set temperature, and a set duration. After the hydrothermal treatment, the present invention constructs a double protective layer in situ on the surface of the commercial zinc metal foil. The upper, uniform ZnO layer can isolate the electrolyte and facilitate interfacial zinc ion transport, while the lower CuZn5 alloy layer or In metal layer can guide the rapid and uniform deposition of zinc, thereby preventing dendrite growth. The modified zinc metal negative electrode provided by the present invention forms two protective layers with different functions on the surface, resulting in improved electrochemical reaction activity and cycle stability, while meeting the requirements of a simple process.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical materials and relates to zinc metal negative electrode materials, in particular to a zinc negative electrode containing a double protective layer and a preparation method thereof. Background Art

[0002] Faced with the depletion of fossil energy and the subsequent environmental degradation, the development of sustainable energy and storage systems is urgent. Lithium-ion batteries are the first commercial rechargeable energy storage devices, but their inherent instability has promoted the development of safer and cheaper multivalent aqueous metal batteries. Among them, aqueous zinc-ion batteries have a high theoretical specific capacity (5855 mAh cm -3 ), low redox potential (-0.763V vs standard hydrogen electrode, SHE), dual electron transfer mechanism and minimal environmental impact are considered to be promising next-generation energy storage devices. In polar aqueous electrolytes, zinc ions are solvated in a tight ion pair [Zn(H2O)6] 2+ They exist in the double layer in the form of ions, and they need to overcome a large desolvation barrier to be deposited on the zinc negative electrode, which makes the reaction kinetics slow.

[0003] In order to solve the serious corrosion caused by excessive contact between the zinc negative electrode and active water molecules, the use of high-concentration electrolyte ("water in salt") and hydrogel electrolyte to reduce the active water molecules in the interface is an effective strategy, but it is difficult to be applied in practice due to its high cost. As an alternative, it was found that the artificial SEI layer can be used to isolate the electrolyte and uniformly Zn 2+ Flux is used to improve the reversibility of zinc anodes. These layers can be broadly divided into insulating and conductive layers based on their properties. Insulating artificial layers such as ZnO, MOFs, and montmorillonite are generally used as physical barriers to isolate the electrolyte or to provide appropriately sized pores and interlayer spaces to promote the desolvation of large-sized solvated ion complexes, thereby inhibiting zinc corrosion. However, due to the relatively rigid nature of the inorganic layer, it is prone to fracture when zinc is excessively plated on the electrode. Consequently, 3D porous conductive artificial layers or frameworks, such as porous carbon and metal frameworks, have been widely reported. Their interconnected network structures can provide numerous nucleation sites and a uniform electric field to guide uniform zinc deposition, while also providing sufficient free volume to accommodate byproducts and zinc deposition. Among these, zinc-philic metal / alloy particles or artificial layers on the anode surface have excellent abilities to regulate zinc deposition behavior and inhibit hydrogen evolution reactions, resulting in a long lifespan for the zinc anode. Therefore, tightly integrating these two artificial layers would be an excellent strategy to significantly improve the stability of the zinc anode. Not only that, this special double-protective layer structure can also be used in electrochemical devices such as supercapacitors and sensors. Summary of the Invention

[0004] In order to address the deficiencies of the prior art, the present invention aims to provide a zinc negative electrode containing a double protective layer and a preparation method thereof, which can significantly improve the cycle stability of the zinc metal negative electrode in an aqueous zinc ion battery.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is: a zinc negative electrode containing a double-layer protective layer, in which a double-layer protective layer is in situ constructed on the upper surface of the zinc metal foil through hydrothermal treatment, and a CuZn5 layer or an In layer is uniformly deposited on the bottom layer, and a ZnO layer is formed on the CuZn5 layer or the In layer.

[0006] The clean zinc metal foil is subjected to hydrothermal treatment to obtain modified zinc metal; the solute of the solution used for the hydrothermal treatment is any one of Na2CO3, Zn(Ac)2, and Cu(Ac)2 or InCl3.

[0007] The temperature of the hydrothermal treatment is 25-250°C.

[0008] The time of hydrothermal treatment is 0.1 to 100 hours.

[0009] Based on the application of the zinc negative electrode containing the double protective layer in electrochemical devices.

[0010] The electrochemical device specifically includes any one of a zinc ion battery, a supercapacitor, and a sensor.

[0011] When used in a zinc ion battery, the counter electrode is the zinc negative electrode or the MnO2 electrode.

[0012] Beneficial effects

[0013] The present invention greatly improves the reaction activity and cycle stability of the zinc metal negative electrode by in-situ construction of a double protective layer. The process is simple and pollution-free to the environment, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1a XRD patterns of commercial and modified zinc metal negative electrodes prepared in Examples 1 and 5 of the present invention.

[0015] Figure 1b This is the XRD pattern of the modified zinc metal negative electrode prepared in Example 4 of the present invention.

[0016] Figure 2a This is a scanning electron microscope image of the surface of a commercial zinc metal negative electrode prepared in Example 1 of the present invention.

[0017] Figure 2b This is a scanning electron microscope image of the surface of the modified zinc metal negative electrode prepared in Example 4 of the present invention.

[0018] Figure 2cThis is a scanning electron microscope image of the modified zinc metal surface prepared in Example 5 of the present invention.

[0019] Figure 2d This is a scanning electron microscope image of the cross section of the modified zinc metal negative electrode prepared in Example 5 of the present invention and the corresponding X-ray energy spectrum line scan curve. Figure 3a This is the electrochemical cycling performance diagram of an aqueous zinc ion symmetric battery assembled with a commercial zinc metal negative electrode prepared in Example 1 of the present invention.

[0020] Figure 3b This is a diagram showing the electrochemical cycling performance of an aqueous zinc ion symmetric battery assembled with the modified zinc metal negative electrode prepared in Example 2 of the present invention.

[0021] Figure 3c This is the electrochemical cycling performance diagram of the aqueous zinc ion symmetric battery assembled with the modified zinc metal negative electrode prepared in Example 3 of the present invention.

[0022] Figure 3d This is a diagram showing the electrochemical cycling performance of an aqueous zinc ion symmetrical battery assembled with the modified zinc metal negative electrode prepared in Example 5 of the present invention.

[0023] Figure 4 Electrochemical cycling performance diagram of full-cell aqueous zinc-ion batteries assembled with commercial and modified zinc metal negative electrodes prepared in Examples 1 and 5 of the present invention and MnO2. DETAILED DESCRIPTION

[0024] The present invention will be further described below through detailed implementation examples to make the technical solutions and advantages of the present invention clearer, but the technical parameters in the following implementation examples are not intended to limit the present invention.

[0025] In view of the poor electrochemical reaction activity and cycle stability of existing zinc metal negative electrode materials, the present invention proposes a zinc negative electrode double-layer protective layer and a preparation method thereof.

[0026] A typical embodiment of the present invention provides a method for preparing a zinc negative electrode containing a double protective layer, wherein a zinc metal foil is hydrothermally treated to obtain a modified zinc metal foil; the original zinc metal foil is a commercial zinc metal foil, and the hydrothermal treatment is carried out in a set metal salt mixed solution at a set temperature and a set time.

[0027] The present invention utilizes the ion exchange reaction of zinc metal foil and constructs two protective layers with different functions in situ on the surface of commercial zinc metal foil through hydrothermal treatment. The upper uniform ZnO layer can isolate the electrolyte and facilitate the transport of zinc ions at the interface. The lower CuZn5 alloy layer or In metal layer can guide the rapid and uniform deposition of zinc to avoid the growth of dendrites. This greatly improves the cycle stability and reaction kinetics of the zinc negative electrode material and enhances the electrochemical performance of aqueous zinc ion batteries.

[0028] The temperature in the hydrothermal treatment of the present invention may fluctuate within a certain range, and the temperature fluctuation range may be 5°C.

[0029] In some examples of this embodiment, the hydrothermal treatment time is 0.1 to 100 hours. When the hydrothermal treatment time is 0.5 to 30 hours, the electrochemical reaction activity and cycle stability of the modified zinc negative electrode are more significantly improved.

[0030] In some examples of this embodiment, the temperature of the hydrothermal treatment is 25-250° C. When the temperature is 50-200° C., the electrochemical reaction activity and cycle stability of the modified zinc negative electrode are more significantly improved.

[0031] In some examples of this embodiment, the solute of the hydrothermal treatment solution is Na2CO3, Zn(Ac)2, plus one of Cu(Ac)2 or InCl3, and the solvent is not limited to deionized water.

[0032] Another embodiment of the present invention provides a modified zinc metal negative electrode obtained by the above preparation method.

[0033] A third embodiment of the present invention provides a use of the modified zinc metal negative electrode in an electrochemical device.

[0034] The electrochemical devices of the present invention include zinc ion batteries, supercapacitors and sensors.

[0035] In a fourth embodiment of the present invention, the modified zinc metal negative electrode is directly used as the negative electrode material.

[0036] The ion battery of the present invention is preferably a zinc ion battery, wherein the counter electrode is itself or MnO2.

[0037] The modified zinc metal obtained by the above preparation method can not only achieve better electrochemical activity and cycle stability in symmetrical batteries, but also achieve better cycle stability and electrochemical performance after being assembled into a full battery.

[0038] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0039] Example 1: Bare Zn Sample

[0040] Commercial zinc metal was placed in ethanol and ultrasonicated for ten minutes to remove surface impurities and labeled as Bare Zn. The X-ray diffraction pattern is shown in Figure 1a As shown in Figure 2, it can be seen that the prepared Bare Zn sample is a pure zinc metal phase. The scanning electron microscope image is shown in Figure 2. Figure 2aAs shown in Figure 3, surface cracks are an important cause of dendrite growth.

[0041] The prepared bare Zn sample was cut into discs with a diameter of 15 mm using a microtome. Symmetric cells and full cells were assembled using the same bare Zn discs or MnO2 as counter electrodes. The electrolyte was 2 mol / L. -1 The ZnSO4 solution was assembled into a CR2025 button battery in air, and then the battery was sealed with a sealing machine to produce a button battery. Finally, the battery was subjected to a constant current charge and discharge test using a blue electric charge and discharge instrument.

[0042] The negative electrode material prepared in the above embodiment is used in a symmetrical battery with an area current density of 0.5 mA cm -2 and an areal capacity of 0.5 mAh cm -2 The charge and discharge test was carried out under the condition of 5Ag -1 Carry out charge and discharge test under Figure 3a As shown in Figure 2, a short circuit occurred in the symmetrical battery after 205h of charge and discharge at a high overpotential of 70mV. Figure 4 As shown, the first cycle discharge capacity of the full battery is 170.1 mAh g -1 , and after 1990 cycles it dropped to 57.01 mAh g -1 .

[0043] Example 2: Zn@Zn sample

[0044] The bare Zn sample obtained in Example 1 was placed in a hydrothermal reactor together with a mixed solution of Na2CO3 and Zn(AC)2 and treated at 140°C for 3 hours to obtain a Zn@Zn sample.

[0045] The Zn@Zn was washed with deionized water and ethanol, dried at 60 °C, and cut into discs with a diameter of 15 mm using a slicer. Symmetric cells and full cells were assembled using the same Zn@Zn discs or MnO2 as counter electrodes, respectively. The electrolyte was 2 mol / L -1 The ZnSO4 solution was placed in the air as a CR2025 button battery, and then the battery was sealed with a sealing machine to produce a button battery. Finally, the battery was subjected to a constant current charge and discharge test on a blue electric charge and discharge instrument.

[0046] The negative electrode material prepared in the above embodiment is used in a symmetrical battery with an area current density of 0.5 mA cm -2 and an areal capacity of 0.5 mAh cm -2 Carry out charge and discharge test under Figure 3b As shown in Figure 3, a short circuit occurred in the symmetrical battery after 270 h of charge and discharge at an overpotential of 30 mV.

[0047] Example 3: Cu@Zn sample

[0048] The bare Zn sample obtained in Example 1 was placed in a hydrothermal reactor together with a mixed solution of Na2CO3 and Cu(AC)2 and treated at 140°C for 3 hours to obtain a Cu@Zn sample.

[0049] The Cu@Zn was washed with deionized water and ethanol, dried at 60°C, and cut into discs with a diameter of 15 mm using a slicer. Symmetric cells and full cells were assembled using the same Cu@Zn discs or MnO2 as counter electrodes, respectively. The electrolyte was 2 mol / L -1 The ZnSO4 solution was placed in the air as a CR2025 button battery, and then the battery was sealed with a sealing machine to produce a button battery. Finally, the battery was subjected to a constant current charge and discharge test on a blue electric charge and discharge instrument.

[0050] The negative electrode material prepared in the above embodiment is used in a symmetrical battery with an area current density of 0.5 mA cm -2 and an areal capacity of 0.5 mAh cm -2 Carry out charge and discharge test under Figure 3c As shown in Figure 3, a short circuit occurred in the symmetrical battery after 470 h of charge and discharge at an overpotential of 20 mV.

[0051] Example 4: InZn@Zn sample

[0052] The Bare Zn sample obtained in Example 1 was placed in a hydrothermal reactor together with a mixed solution of Na2CO3, Zn(AC)2 and InCl3 and treated at 140°C for 3 hours to obtain the InZn@Zn sample. Figure 1b The X-ray diffraction patterns shown and Figure 2b The scanning electron microscope images shown confirm the formation of an In metal layer and a uniform ZnO nanorod layer on the surface of the metallic zinc foil.

[0053] InZn@Zn was washed with deionized water and ethanol, dried at 60 °C, and cut into 15 mm diameter discs using a microtome. Symmetric cells and full cells were assembled using the same InZn@Zn discs or MnO2 as counter electrodes. The electrolyte was 2 mol / L -1 The ZnSO4 solution was placed in the air as a CR2025 button battery, and then the battery was sealed with a sealing machine to produce a button battery. Finally, the battery was subjected to a constant current charge and discharge test on a blue electric charge and discharge instrument.

[0054] Example 5: CuZn@Zn sample

[0055] The bare Zn sample obtained in Example 1 was placed in a hydrothermal reactor together with a mixed solution of Na2CO3, Zn(AC)2 and Cu(Ac)2 and treated at 140°C for 3 hours to obtain a CuZn@Zn sample. Figure 2c As shown, the surface is a uniform ZnO nanorod layer. Figure 1a The X-ray diffraction patterns shown and Figure 2d The X-ray spectrometer line scan shown proves that the double protective layer formed is a ZnO nanorod layer on the upper side and a CuZn5 alloy layer on the lower side.

[0056] The CuZn@Zn was washed with deionized water and ethanol, dried at 60 °C, and cut into discs with a diameter of 15 mm using a slicer. Symmetric cells and full cells were assembled using the same CuZn@Zn discs or MnO2 as counter electrodes. The electrolyte was 2 mol / L -1 The ZnSO4 solution was placed in the air as a CR2025 button battery, and then the battery was sealed with a sealing machine to produce a button battery. Finally, the battery was subjected to a constant current charge and discharge test on a blue electric charge and discharge instrument.

[0057] The negative electrode material prepared in the above embodiment is used in a symmetrical battery with an area current density of 0.5 mA cm -2 and an areal capacity of 0.5 mAh cm -2 The charge and discharge test was carried out under the condition of 5Ag -1 Carry out charge and discharge test under Figure 3d As shown in the figure, the symmetrical battery can be charged and discharged for more than 2200h at a low overvoltage of 16mV. Figure 4 As shown, the first cycle discharge capacity of the full battery is 188.3 mAh cm -2 , and decreased to 139.7 mAh cm after 2500 cycles. -2 .

[0058] The above results show that the material prepared by the present invention is used as a matrix for zinc metal foil that is easy to undergo ion exchange, and the modified zinc metal foil subjected to hydrothermal treatment is used as the negative electrode of the zinc ion battery. It was found that after hydrothermal treatment, an upper layer of ZnO nanorods and a lower layer of CuZn5 alloy or In metal were formed. The formation of these two different phases and their distribution on the surface of the zinc negative electrode were demonstrated by X-ray diffraction patterns, scanning electron microscope images and X-ray energy spectrum images. Among them, the upper ZnO layer can isolate active water molecules and improve the zinc ion transport at the interface, while the lower CuZn5 alloy layer or In metal layer can guide the uniform deposition of zinc metal. This shows that in situ formation of a double protective layer with different functions on the zinc negative electrode through hydrothermal reaction is a simple and effective method to improve the electrochemical performance of its negative electrode.

[0059] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A zinc negative electrode containing a double protective layer, characterized in that: A double-layer protective layer is in situ constructed on the upper surface of the zinc metal foil through hydrothermal treatment, wherein a CuZn5 layer or an In layer is uniformly deposited on the bottom layer, and a ZnO layer is formed on the CuZn5 layer or the In layer.

2. The method for preparing a zinc negative electrode containing a double protective layer according to claim 1, characterized in that: The clean zinc metal foil is subjected to hydrothermal treatment to obtain a zinc negative electrode; the solute of the solution used for the hydrothermal treatment is a combination of Na2CO3, Zn(Ac)2, Cu(Ac)2 or a combination of Na2CO3, Zn(Ac)2, InCl3.

3. The method for preparing a zinc negative electrode containing a double protective layer according to claim 2, wherein: The temperature of the hydrothermal treatment is 25~250 ℃.

4. The method for preparing a zinc negative electrode containing a double protective layer according to claim 2, wherein: The hydrothermal treatment time is 0.1~100 h.

5. Use of the zinc negative electrode containing a double protective layer according to claim 1 in an electrochemical device.

6. The use according to claim 5, characterized in that The electrochemical device specifically includes any one of a zinc ion battery, a supercapacitor, and a sensor.

7. The use according to claim 6, characterized in that When used in a zinc ion battery, the counter electrode is the zinc negative electrode as described in claim 1 or a MnO2 electrode.

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