Zinc oxide electrode modification method and application
By covering the reduced graphene oxide layer on the surface of the zinc oxide electrode, the problem of uneven deposition of zincate ions is solved, the battery performance improvement and cost reduction is achieved, the modification process is simplified, and it is suitable for alkaline water-based nickel-zinc batteries.
Patent Information
- Application Number
- CN202510424961.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2025-08-26
AI Technical Summary
During the charging and discharging process of conventional zinc oxide negative electrode materials, zinc dendrites growth and passivation layer formation are caused by uneven deposition of zincate ions, resulting in deterioration of battery performance. The existing modification methods are costly or complex in processes are not conducive to commercialization.
The surface of the zinc oxide electrode is covered with a reduced graphene oxide layer of 10-20 nm thick, and the reduced graphene oxide is coated on the surface of the zinc oxide electrode by wet method, scraper or dry spraying method to form a multi-layer reduced graphene oxide layer to inhibit the migration of zincate ions.
Effectively inhibit zincate ion migration, improve battery performance, reduce costs, simplify modification processes, and improve battery cycle stability and capacity retention.
Smart Images
Figure CN120545293A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a zinc oxide electrode modification method and application. Background Art
[0002] As research on various zinc-ion batteries continues to deepen, further development is needed for various electrode materials and electrode-electrolyte interfaces. Alkaline aqueous nickel-zinc batteries have garnered widespread attention due to their versatility, low cost, and high safety. In particular, they can charge and discharge at low temperatures, making them widely applicable in low-temperature applications. From a cost perspective, zinc metal reserves are abundant and relatively inexpensive globally. From a production safety perspective, aqueous zinc-ion batteries offer low toxicity and high electrochemical activity. Furthermore, zinc as the negative electrode possesses high mass specific capacity, high volumetric capacity, and a low redox potential. Most importantly, zinc metal can be directly incorporated into aqueous electrolytes, exhibiting high oxidation resistance and moisture resistance, significantly reducing zinc battery processing costs. Batteries utilizing various metal doping methods, such as zinc-manganese, zinc-silver, and zinc-nickel batteries, have begun to emerge. These batteries all leverage the stability and safety of zinc metal, particularly in alkaline aqueous nickel-zinc batteries, where these advantages are further amplified.
[0003] However, alkaline aqueous nickel-zinc batteries still have specific problems to solve, especially the conventional zinc oxide negative electrode material still has defects. Conventional zinc oxide negative electrode materials will undergo solid phase-solution-solid phase "ZnO-Zn(OH)4 2- -Zn" conversion process, in which zincate ions dissolved in the electrolyte will be deposited on the battery separator or even the nickel positive electrode, resulting in irreversible Zn loss. In addition, the uneven deposition of zincate ions will generate a passivation layer with poor conductivity and cause the growth of zinc dendrites, thereby deteriorating battery performance. The source of these problems can essentially be attributed to the fact that zincate will accumulate in large quantities and unevenly near the electrode during the migration and deposition process over a large range, resulting in different ion environments in a certain local area, and severe zinc dendrites and passivation layers will form in this local area. Therefore, inhibiting the migration of zincate ions in alkaline electrolytes is an effective way to improve battery performance.
[0004] In order to achieve the purpose of inhibiting the migration of zincate ions, some studies have used carbon-coated structures for modification (Advanced Energy Materials 2018, 8(36), 1802470). However, this technology is for carbon coating of ZnO particles, which is too expensive and not conducive to commercial production. In addition, introducing too much carbon material into the negative electrode will cause other negative electrode reactions, such as hydrogen generation. There are also studies using zinc negative electrodes and soluble metal Ag for modification (ACS Energy Letters 2021, 6(2), 404-412). However, the zinc negative electrode and soluble metal Ag used in this technology are too expensive to be commercialized, and the preparation process is complicated, which is not conducive to large-scale promotion. Summary of the Invention
[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for modifying a zinc oxide electrode.
[0006] Another object of the present invention is to provide a zinc oxide electrode modified by the above method.
[0007] Another object of the present invention is to provide an application of the zinc oxide electrode in an alkaline aqueous nickel-zinc battery.
[0008] The purpose of the present invention is achieved through the following solutions:
[0009] A method for modifying a zinc oxide electrode comprises the following steps: covering the surface of the zinc oxide electrode with a reduced graphene oxide layer, wherein the thickness of the reduced graphene oxide layer is 10-20 nm.
[0010] The zinc oxide electrode is prepared by applying a slurry of zinc oxide and zinc powder to the surface of a current collector.
[0011] The reduced graphene oxide is multilayer reduced graphene oxide (rGO).
[0012] The multilayer reduced graphene oxide has a carbon content of less than 97 wt%, an oxygen content of more than 0.5 wt%, a sulfur content of less than 3 wt%, and a total thickness of 3-8 nm.
[0013] The covering method includes one of wet spraying, blade coating, and dry spraying.
[0014] The wet spraying method includes the following steps: dissolving the reduced graphene oxide material in water, adding an active agent to inhibit the agglomeration of the reduced graphene oxide to obtain a reduced graphene oxide slurry; spraying the slurry onto the surface of the ZnO electrode using a spray gun, and drying the slurry.
[0015] The solid content of the reduced graphene oxide slurry is 4-8 wt %.
[0016] The spraying height is 40-60 mm; the flow rate is 0.03-0.08 mL / s; and the horizontal movement speed of the spray gun is 5-8 mm / s.
[0017] The scraper coating method includes the following steps: dissolving reduced graphene oxide material in water, adding an active agent to inhibit the agglomeration of reduced graphene oxide, and obtaining reduced graphene oxide slurry; placing a ZnO electrode on a conveyor belt, setting a slurry outlet above the conveyor belt, extruding the slurry, scraping it flat on the surface of the ZnO electrode with a scraper, and drying it.
[0018] The active agent for wet spraying and scraper coating includes at least one of ethylenediaminetetraacetic acid (EDTA), tetramethylammonium hydroxide (TMAOH), tetrabutylammonium hydroxide (TBAOH), polyethylene oxide (PEO), ethanol, n-propanol, and isobutanol; the mass of the active agent accounts for 0.5%-3% of the mass of the reduced graphene oxide slurry.
[0019] The drying temperature in the wet spray coating and blade coating is room temperature to 80°C.
[0020] The dry spraying method comprises the following steps: placing reduced graphene oxide in a cavity and spraying it on the surface of the ZnO electrode using high-speed air.
[0021] The zinc oxide electrode modified by the above method.
[0022] Application of the above zinc oxide electrode in alkaline aqueous nickel-zinc batteries.
[0023] The mechanism of the present invention is:
[0024] The present invention coats the surface of a negative electrode, prepared from a mixture of ZnO and Zn powder, with a thin layer of reduced graphene oxide (rGO). This thin layer of rGO has a negative surface charge, effectively inhibiting the migration of negatively charged zincate ions to the separator or positive electrode, thereby suppressing side reactions. Furthermore, the negatively charged rGO layer provides an effective electric field, assisting in the uniform deposition of Zn.
[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0026] 1. Compared with existing carbon coating technology, the cost is greatly reduced. Instead of carbon coating individual ZnO particles, only a thin layer of reduced graphene oxide is coated on the currently commercialized ZnO electrode sheet.
[0027] 2. Compared with existing commercial alkaline Ni-Zn batteries, the battery performance is greatly improved, and it can effectively inhibit uneven Zn deposition and zincate migration.
[0028] 3. Simplify the method of adding active agents to the electrolyte. Prepare a water-soluble slurry, add reduced graphene oxide, active agents, and active agents in the electrolyte together in the solution, and further spray it on the surface of the ZnO negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 Schematic diagram of the structure of the rGO-modified zinc oxide electrode obtained in the present invention.
[0030] Figure 2 Schematic diagram of the working principle of the rGO-modified zinc oxide electrode obtained in the present invention.
[0031] Figure 3 This is the surface SEM image of the zinc oxide electrode obtained in step (2) of Example 1.
[0032] Figure 4 This is the surface SEM image of the rGO-modified zinc oxide electrode obtained in Example 1.
[0033] Figure 5 Graphs of battery performance of electrodes before and after rGO modification, where a is the zinc oxide electrode obtained in step (2) of Example 1; b is the rGO-modified zinc oxide electrode obtained in Example 1. DETAILED DESCRIPTION
[0034] The present invention will be described in further detail below with reference to the Examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.
[0035] Unless otherwise specified, all reagents used in the examples can be purchased from the market.
[0036] Multilayer reduced graphene oxide: purchased from Shanxi Nuotai Biotechnology Co., Ltd., with carbon content <97 wt%, oxygen content >0.5 wt%, sulfur content <3 wt%, rGO purity >90 wt%, and thickness of 5 nm.
[0037] Example 1
[0038] (1) Preparation of reduced graphene oxide slurry:
[0039] Multilayer reduced graphene oxide (rGO) was mixed with deionized water, and EDTA was added to obtain a reduced graphene oxide slurry with a solid content of 5 wt %, wherein EDTA accounted for 2.2% of the mass of the reduced graphene oxide slurry.
[0040] (2) Preparation of zinc oxide electrode:
[0041] 73% zinc oxide, 18% zinc metal, and 9% binder (polyvinylidene fluoride (PVDF)) were mixed by mass to obtain a zinc oxide slurry; the zinc oxide slurry was coated on the surface of a tin-plated copper foil current collector with a scraper to a thickness of 4 μm, and then placed in a vacuum oven and dried at 60°C for 5 hours to obtain a zinc oxide electrode.
[0042] (3) rGO modified zinc oxide electrode:
[0043] Using a small laboratory spray gun, the rGO slurry was sprayed onto the surface of the zinc oxide electrode (spraying height 50 mm, flow rate 0.05 ml / s, horizontal movement speed 5 mm / s) to a thickness of 15 nm, achieving rGO coverage on the zinc oxide electrode. The slurry was then dried in a vacuum oven at 80°C for 4 hours to obtain the rGO-modified zinc oxide electrode.
[0044] Figure 1 This is a schematic diagram of the structure of the rGO-modified zinc oxide electrode obtained in the present invention, in which from top to bottom are the reduced graphene oxide layer, the zinc oxide layer, and the electrode current collector.
[0045] Figure 2 This is a schematic diagram of the working principle of the rGO-modified zinc oxide electrode obtained in the present invention. As shown in the figure, the graphene layer covering the electrode surface is negatively charged. During the battery reaction, zincate ions are generated and located in the electrolyte between the zinc oxide layer and the reduced graphene oxide layer, also with a negative charge. Therefore, the reduced graphene oxide layer effectively inhibits the migration of zincate ions to the separator or positive electrode, thereby suppressing side reactions. Furthermore, the negatively charged reduced graphene oxide layer also provides an effective electric field, assisting in the uniform deposition of Zn.
[0046] Test Example:
[0047] The rGO-modified zinc oxide electrode obtained in Example 1 was cut into 12 mm diameter sheets using a circular slicer and tested as the negative electrode of a button cell. The positive electrode used commercial nickel hydroxide / nickel element, and PTFE was used as the binder. A commercial double-layer membrane was used as the separator. A 12 M KOH solution was used as the electrolyte. The cells were assembled into button cells using conventional button cell assembly methods. A battery of the same specifications without rGO modification was also prepared for performance testing and comparison.
[0048] The material characterization was carried out using scanning electron microscopy (SEM) to test the surface morphology of the unmodified and modified zinc oxide electrodes. Figure 3 and Figure 4As shown in the figure, the surface of the unmodified zinc oxide electrode can be seen to be covered with zinc oxide and zinc particles, and there are some concentrated and uniform flaky areas, but there are also some cracks and height fluctuations. The surface of the modified zinc oxide electrode has black-covered areas. There is a spray-formed rGO layer on the surface of these areas, which covers the surface of the zinc oxide to form a coating that enhances conductivity. This proves that rGO is successfully coated on the surface of the zinc oxide electrode by a wet method.
[0049] Use electrochemical workstation to test battery performance. Performance test is mainly long cycle test, test results are as follows Figure 5 As shown, the test steps are to activate the battery first, and then discharge at a rate of 0.5C until the voltage is less than 1.2V, and then discharge at a rate of 0.3C until the voltage is less than 1.2V. After standing for 10 minutes, charge at a rate of 0.3C until the voltage is greater than 1.9V, followed by constant voltage charging at 1.9V until the current rate is less than 0.1C or this step has been greater than 30 minutes, and then stand for 10 minutes, and discharge at a rate of 0.3C until the voltage is less than 1.2V. After completing the above steps, repeat the cycle of standing, charging at a rate of 0.3C, charging at a constant voltage of 1.9V, standing, and discharging at a rate of 0.3C again, and the cycle ends with 300 turns. Figure 5 The battery capacity changes in the first 30 cycles are given to show its performance. Figure 5 In b, the battery capacity after rGO modification remains stable at around 280mAh after 30 cycles, and the coulombic efficiency remains above 90%. Figure 5 The battery capacity of the unmodified zinc oxide electrode in a showed a significant downward trend in less than 30 cycles, gradually decreasing from about 160mAh to about 30mAh, and the coulombic efficiency was also extremely unstable, decreasing from about 90% to about 50%. That is, the modified zinc oxide electrode battery has more stable cycle stability and capacity retention rate, while the unmodified zinc oxide electrode battery has extremely poor performance, showing low cycle stability and capacity retention rate at a relatively small number of cycles.
[0050] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.
Claims
1. A method for modifying a zinc oxide electrode, characterized in that: The following steps are involved: A reduced graphene oxide layer is covered on the surface of the zinc oxide electrode, wherein the thickness of the reduced graphene oxide layer is 10-20 nm.
2. The method for modifying the zinc oxide electrode according to claim 1, wherein: The reduced graphene oxide is a multilayer reduced graphene oxide; The multilayer reduced graphene oxide has a carbon content of less than 97 wt%, an oxygen content of more than 0.5 wt%, a sulfur content of less than 3 wt%, and a total thickness of 3-8 nm.
3. The method for modifying the zinc oxide electrode according to claim 1, wherein: The covering method includes one of wet spraying, blade coating, and dry spraying.
4. The method for modifying the zinc oxide electrode according to claim 3, wherein: The wet spraying process comprises the following steps: The reduced graphene oxide material is dissolved in water, and an active agent is added to inhibit the agglomeration of the reduced graphene oxide to obtain a reduced graphene oxide slurry; the reduced graphene oxide slurry is sprayed onto the surface of the ZnO electrode using a spray gun and dried.
5. The method for modifying the zinc oxide electrode according to claim 4, wherein: The solid content of the reduced graphene oxide slurry is 4-8wt%; The spraying height is 40-60 mm; the flow rate is 0.03-0.08 mL / s; and the horizontal movement speed of the spray gun is 5-8 mm / s.
6. The method for modifying the zinc oxide electrode according to claim 3, wherein: The blade coating method comprises the following steps: The reduced graphene oxide material is dissolved in water, and an active agent is added to inhibit the agglomeration of the reduced graphene oxide to obtain a reduced graphene oxide slurry; a ZnO electrode is placed on a conveyor belt, a slurry outlet is set above the conveyor belt, the slurry is extruded, and it is flattened on the surface of the ZnO electrode with a scraper and dried.
7. The method for modifying a zinc oxide electrode according to claim 4 or 6, characterized in that: The active agent includes at least one of ethylenediaminetetraacetic acid, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, polyethylene oxide, ethanol, n-propanol, and isobutanol; the mass of the active agent accounts for 0.5%-3% of the mass of the reduced graphene oxide slurry; The drying temperature is from room temperature to 80°C.
8. The method for modifying the zinc oxide electrode according to claim 3, characterized in that: The dry spraying method comprises the following steps: placing reduced graphene oxide in a cavity and spraying it on the surface of the ZnO electrode using high-speed air.
9. The zinc oxide electrode modified by the method according to any one of claims 1 to 8.
10. Use of the zinc oxide electrode according to claim 9 in an alkaline aqueous nickel-zinc battery.