Method for constructing metal zinc negative electrode surface protection layer through one-step heating and application

Abstract

The invention belongs to the technical field of electrode material modification, and particularly relates to a method for constructing a metal zinc negative electrode surface protection layer through one-step heating and application. The method comprises the following steps: cleaning the surface of a commercial zinc electrode, heating in an inert gas atmosphere, cooling, and taking out the commercial zinc electrode to obtain the modified zinc negative electrode material. According to the method, copper impurities originally existing in the commercial zinc electrode are creatively utilized, internal copper atoms have diffusivity through thermal activation, meanwhile, the copper atoms are induced to be diffused to the surface through attraction force of oxygen anions from the surface layer of the commercial zinc electrode, finally, the surface layer rich in copper is formed, and under the action of the surface layer, the surface layer rich in copper is formed. The deposited zinc is dendrite-free, dense, uniform and has a (101) orientation. Meanwhile, in the preparation process, additional additives are not needed, operation is easy, and the method has the advantages of being low in cost, high in efficiency and free of pollution and has the industrialization prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of electrode material modification, and specifically relates to a method for constructing a surface protective layer of a metal zinc negative electrode by one-step heating and an application thereof. Background Art

[0002] Accelerating the development and application of renewable energy such as wind and solar energy, large-scale fixed energy storage devices play a vital role in promoting sustainable energy development, and aqueous zinc batteries are receiving widespread attention due to their low cost and environmental protection. Zinc sheets, as enrichment materials for aqueous zinc batteries, have high theoretical specific capacity and low redox potential. Compared with lithium batteries, they have advantages in safety and cost, and have great application potential. However, the uncontrollable growth of dendrites on the surface of zinc negative electrodes during use is the biggest obstacle to their widespread application. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a method and application for constructing a surface protective layer of a metallic zinc negative electrode by one-step heating.

[0004] The technical solution adopted by the present invention is as follows: a method for constructing a surface protective layer of a metal zinc negative electrode by one-step heating, comprising the following steps: cleaning the surface of a commercial zinc electrode, then heating it under an inert gas atmosphere, and taking out the commercial zinc electrode after cooling to obtain a modified zinc negative electrode material.

[0005] Preferably, the surface of the commercial zinc electrode is cleaned by rinsing with anhydrous ethanol.

[0006] Preferably, the inert gas is argon or nitrogen.

[0007] Preferably, the heating is carried out in a tube furnace.

[0008] Preferably, the heating temperature is 250-350° C. and the heating time is 5-15 h.

[0009] The one-step heating method for constructing a surface protective layer of a metal zinc negative electrode as described above is used for preparing an application of a zinc negative electrode.

[0010] The one-step heating method for constructing a surface protective layer of a metallic zinc negative electrode as described above is used for preparing an aqueous zinc battery.

[0011] A zinc negative electrode material for an aqueous zinc battery is prepared by the method of constructing a metal zinc negative electrode surface protective layer by one-step heating as described above.

[0012] An aqueous zinc battery comprises the zinc negative electrode material as described above.

[0013] The beneficial effects of the present invention are as follows: the present invention innovatively utilizes the copper impurities originally existing in the commercial zinc electrode, and makes these internal copper atoms diffusible through thermal activation, and at the same time utilizes the attraction of oxygen anions from the surface layer of the commercial zinc electrode to induce these copper atoms to diffuse to the surface and finally form a copper-rich surface layer. Under the action of this surface layer, the deposited zinc is dendrite-free, dense, uniform and has a (101) orientation. At the same time, the present invention does not require additional additives during the preparation process and is simple to operate, has the advantages of low cost, high efficiency, and no pollution, and has the prospect of industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0015] Figure 1 Digital photo of heat treated zinc electrode material. Figure 2 Energy dispersive X-ray spectroscopy analysis of the surface of commercial zinc electrodes; Figure 3 Energy dispersive X-ray spectrometer analysis of the surface of heat-treated zinc electrode materials; Figure 4 Surface X-ray diffraction data of commercial zinc electrode and heat-treated zinc electrode materials; Figure 5 Calculation of the zinc affinity of the new phase on the surface of heat-treated zinc electrode materials; Figure 6 A top view of the zinc electrodeposition process of a commercial zinc electrode and the corresponding 3D height profile analysis of the same area; Figure 7 A top view of the zinc electrodeposition process for heat-treated zinc electrodes and a corresponding 3D height profile analysis of the same area; Figure 8 This is a scanning electron micrograph of zinc deposition on a commercial zinc electrode; Fig. 9 The SEM image of zinc deposition on the heat-treated zinc electrode; Fig.10 The X-ray diffraction data of the surface of commercial zinc electrode during zinc deposition at different surface capacities; Fig.11 The X-ray diffraction data of the surface of the heat-treated zinc electrode during zinc deposition at different surface capacities; Fig.12 For the cycling performance of commercial zinc electrodes; Fig.13 Cycling performance of heat-treated zinc electrodes; Fig.14 The surface color changes of two commercial zinc electrodes with different copper contents before and after heat treatment; Fig.15 This is a scanning electron microscope image of zinc deposition on the surface of a commercial zinc electrode with low copper content after heat treatment. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0017] The present invention provides a method for constructing a metal zinc negative electrode surface protective layer by one-step heating, comprising the following steps: cleaning the surface of a commercial zinc electrode, then heating it in an inert gas atmosphere, and cooling it down and taking out the commercial zinc electrode to obtain a modified zinc negative electrode material. Currently, commercial zinc electrodes available on the market all contain a certain amount of copper impurities. The present invention innovatively utilizes the copper impurities originally present in the commercial zinc electrode, and makes these internal copper atoms diffusible through thermal activation, and at the same time utilizes the attraction of oxygen anions in the surface layer of the commercial zinc electrode to induce these copper atoms to diffuse to the surface to finally form a copper-rich surface layer. Under the action of the surface layer, the deposited zinc is dendrite-free, dense, uniform and has a (101) orientation. The specific copper content in the commercial zinc electrode may vary depending on the production process, raw materials and application requirements. Most of its product specifications provide detailed information on the electrode composition, including the copper content. Some embodiments of the present invention test commercial zinc electrodes with different copper contents, and all of them can achieve the purpose of the present invention, which is to improve the uncontrollable growth of dendrites on the surface of the zinc negative electrode. The higher the copper content, the better the improvement effect.

[0018] In some embodiments of the present invention, the heating temperature is 250-350° C. and the heating time is 5-15 h. The purpose of the present invention can be achieved by heating within the above heating temperature and heating time ranges.

[0019] Embodiment 1: The surface of the commercial zinc electrode cut into a suitable size was rinsed clean with anhydrous ethanol. After natural drying, the electrode foil was placed in a tubular furnace with argon gas and heated at 330°C for 10 h to finally obtain a zinc negative electrode treatment with a copper-rich surface.

[0020] Digital photos of zinc electrode materials after heat treatment Figure 1 As shown, after the heat treatment, the surface of the electrode material turns yellow, which is presumably because copper present as an impurity in the zinc metal diffuses to the surface.

[0021] The commercial zinc electrode was placed in a centrifuge tube containing an appropriate amount of anhydrous ethanol, and the centrifuge tube was placed in an ultrasonic oscillator for 5 hours. After the end, a few drops of liquid were dropped onto a molybdenum mesh for energy dispersive X-ray diffraction test. The same method was used to prepare and test the heat-treated zinc electrode material. The results were as follows: Figure 2 and Figure 3 As shown, there is an obvious copper signal on the surface of the zinc electrode after heat treatment, indicating that simple heat treatment can induce copper, which exists as an impurity in the commercial zinc electrode, to be enriched on the surface.

[0022] X-ray diffraction data of commercial zinc electrode and heat-treated zinc electrode are shown in Figure 4 As shown in the figure, new copper-containing objects (Cu 0.02 Zn 0.98 O).

[0023] Based on the calculation results of density functional theory, the binding energy results of the copper-containing objects on the surface of the heat-treated zinc electrode and the zinc metal crystal planes for the zinc atoms are as follows: Figure 5 As shown, it is shown that the copper-containing object has a strong zinc affinity, can effectively regulate the uniform and dense deposition of zinc, and inhibit the growth of zinc dendrites.

[0024] Test Example 1: Using an in-situ optical cell, a 2 M ZnSO4 electrolyte was selected and the current density was 5 mA cm -2 , surface capacity is 2 mAh cm -2 Under the conditions of , the process of zinc electrodeposition on the surface of commercial zinc electrode and heat-treated zinc electrode was recorded in situ based on the top view perspective. The results are as follows Figure 6 and Figure 7 As shown in Figure 2, zinc deposition on the heat-treated zinc electrode showed no dendrite growth and maintained a dense and uniform deposition throughout.

[0025] Test Example 2: The zinc deposition on the surface of the commercial zinc electrode and the heat-treated zinc electrode was characterized by scanning electron microscopy. The obtained scanning electron microscopy images are shown in Figure 2. Figure 8 and Fig. 9 As shown, the current density of zinc deposition was 5 mA cm -2 , surface capacity of 1 mAh cm -2 The results show that the morphology of zinc deposited on the surface of the commercial zinc electrode is very uneven, and the dendrite growth phenomenon is very serious. In contrast, the zinc deposited on the surface of the zinc electrode after heat treatment maintains uniform deposition and has special texture crystallographic characteristics.

[0026] Zinc deposition was performed on the surface of commercial zinc electrode and heat-treated zinc electrode at a current density of 5 mA cm -2The surface capacities are 0, 0.5, and 1 mAh cm -2 The corresponding X-ray diffraction data are as follows: Fig.10 and Fig.11 As shown in the figure, for commercial zinc electrodes, as the surface capacity of deposited zinc increases, the relative strength of the various crystal planes of zinc metal on its surface does not change significantly. In contrast, for heat-treated zinc electrodes, the relative strength of the Zn-(101) crystal plane on its surface increases with the increase of the electrodeposition surface capacity, that is, as the surface capacity density increases, the Zn-(101) texture on the surface of the heat-treated zinc electrode is enhanced.

[0027] Test Example 3: The electrochemical performance of commercial zinc electrode and heat-treated zinc electrode materials were tested using a 2032-type button-type symmetrical cell. The components of the button-type cell include the negative electrode shell, modified zinc sheet, separator, modified zinc sheet, gasket and positive electrode shell. The electrolyte is a 2 M ZnSO4 aqueous solution. The cycling performance of different symmetrical cells was tested at a constant current density using a Xinwei battery test system. The test parameters are a current density of 5 mA cm -2 , with an area capacity of 1 mAh cm -2 The test data of zinc-zinc symmetric battery of commercial zinc electrode and heat-treated zinc electrode are as follows: Fig.12 and Fig.13 The results show that the commercial zinc electrode battery short-circuited at about 205 h and had poor cycle stability. In contrast, the heat-treated battery cycled stably for about 3600 h, and the cycle stability was significantly improved.

[0028] Test Example 4: Commercial zinc electrodes with copper impurity contents of 0.003% and 0.0003% were used and heated at 330°C for 10 h in a tube furnace filled with argon. Fig.14 As shown in the figure, both commercial zinc electrodes turned yellow after heating, while the zinc electrode with a lower copper impurity content turned yellow to a lesser extent. In addition, the commercial zinc electrodes mentioned in Test Examples 2 and 3 were copper-rich zinc (copper content was about 0.003%), while the copper-poor zinc electrode (copper content was 0.0003%) after heating had a yellowing phenomenon on its surface at a current density of 5 mA cm -2 , surface capacity of 1 mAh cm -2 After zinc deposition, the scanning electron microscope images are as follows: Fig.15 As shown, its surface still has Zn-(101) texture, but compared with Fig. 9 The intensity is obviously weaker.

[0029] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for constructing a surface protective layer of a metal zinc negative electrode by one-step heating, characterized in that The following steps are involved: The surface of the commercial zinc electrode is cleaned, then heated in an inert gas atmosphere, and after cooling, the commercial zinc electrode is taken out to obtain the modified zinc negative electrode material.

2. The method for constructing a metal zinc negative electrode surface protective layer by one-step heating according to claim 1, characterized in that: The surface of the commercial zinc electrode was cleaned by rinsing with anhydrous ethanol.

3. The method for constructing a metal zinc negative electrode surface protective layer by one-step heating according to claim 1, characterized in that: The inert gas is argon or nitrogen.

4. The method for constructing a metal zinc negative electrode surface protective layer by one-step heating according to claim 1, characterized in that: The heating is carried out in a tube furnace.

5. The method for constructing a metal zinc negative electrode surface protective layer by one-step heating according to claim 1, characterized in that: The heating temperature is 250-350°C and the heating time is 5-15 h.

6. Application of the method for constructing a surface protective layer of a metallic zinc negative electrode by one-step heating as described in any one of claims 1 to 5 in preparing a zinc negative electrode.

7. Use of the method for constructing a metal zinc negative electrode surface protective layer by one-step heating as described in any one of claims 1 to 5 in preparing an aqueous zinc battery.

8. A zinc negative electrode material for an aqueous zinc battery prepared by the method for constructing a metal zinc negative electrode surface protective layer by one-step heating as described in any one of claims 1 to 5. 9 . An aqueous zinc battery comprising the zinc negative electrode material according to claim 8 .

Images