Method for improving electricity storage performance of nickel cobaltate cathode through photo-assisted electrochemical oxidation
By supplementing the electrochemical oxidation process with light irradiation, a highly crystalline NiOOH/CoOOH composite layer is formed, which solves the problem of insufficient reactivity of nickel cobalt oxide and improves the high-efficiency energy storage performance of nickel cobalt oxide materials, making them suitable for water-based zinc ion hybrid capacitors.
Patent Information
- Application Number
- CN202511284513.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-10
- Publication Date
- 2026-01-06
AI Technical Summary
When nickel cobalt oxide is used as the cathode material of an aqueous zinc ion hybrid capacitor, there are insufficient reactive sites and the kinetic reaction rate is slow, resulting in a large gap between the actual energy storage capacity and the theoretical capacity. Existing improvement methods have problems such as difficulty in controlling the conditions, complex preparation process, and difficulty in large-scale implementation.
By supplementing the electrochemical oxidation process with light irradiation, the semiconductor properties of nickel cobalt oxide are utilized to generate photogenerated electrons and holes, forming a NiOOH/CoOOH composite layer with high crystallinity. This increases the reactive surface area and adds new reaction pathways, thereby improving the energy storage performance of the material.
By using a photo-assisted electrochemical oxidation method, the operation is simplified and the cost is reduced, thereby improving the electrochemical performance of nickel cobalt oxide materials and significantly increasing their energy storage capacity, making them suitable for large-scale applications.
Smart Images
Figure CN121282018A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of energy storage electrode material technology, and relates to a method for improving the energy storage performance of nickel cobalt oxide by supplementing the electrochemical oxidation treatment of nickel cobalt oxide with light irradiation to generate a composite surface layer with higher crystallinity, increasing the active surface and adding new reaction pathways. Background Technology
[0002] With the rapid development of portable electronic products and electric vehicles, the demand for high-performance, intrinsically safe, and environmentally friendly high-efficiency energy storage devices is increasing. Although lithium-ion batteries are widely used, they suffer from problems such as scarce lithium resources, significant safety hazards, and slow charging speeds. Furthermore, despite offering high energy density, their relatively low power density limits their application in some situations. Aqueous zinc-ion hybrid capacitors not only offer advantages such as low cost, high safety, and good cycle performance, but also combine the characteristics of batteries and capacitors, achieving both high energy density and power density, thus possessing great development potential.
[0003] Nickel cobalt oxide, when used as a cathode material in aqueous zinc-ion hybrid capacitors, boasts a theoretical specific capacity exceeding 500 mAh / g. It not only possesses high theoretical capacity but also advantages such as abundant resources, simple preparation, and good reversibility, making it a popular electrode material. However, nickel cobalt oxide suffers from insufficient reactive sites and slow kinetic reaction rates, resulting in a significant difference between its actual and theoretical energy storage capacities. Current methods to improve the performance of nickel cobalt oxide mainly include doping, introducing oxygen vacancy defects, and combining it with other materials. However, these methods all suffer from varying degrees of difficulties in controlling the conditions, complex preparation processes, and large-scale implementation. Therefore, developing a simple, efficient, easily controllable, low-cost, and large-scale application method to improve the performance of nickel cobalt oxide is particularly important. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a method for improving the energy storage performance of nickel cobalt oxide cathodes through photo-assisted electrochemical oxidation. The invention leverages the semiconductor properties of nickel cobalt oxide, utilizing its ability to generate highly reactive photogenerated electrons and holes under light. During the electrochemical oxidation process, light irradiation is applied to promote the formation of a highly crystalline NiOOH / CoOOH composite layer on its surface. The formation of this composite layer increases the reactive surface area, introduces new reaction pathways, and thus enhances the intercalation and adsorption of electrolyte ions, thereby increasing the material's energy storage capacity. This method is simple, easy to implement, low-cost, and time-efficient, enabling large-scale implementation. The resulting nickel cobalt oxide material exhibits significantly improved electrochemical performance and demonstrates a high energy storage capacity when used as an aqueous zinc ion hybrid capacitor.
[0005] The technical solution of the present invention is as follows: under certain light and electrolyte conditions, nickel cobalt oxide attached to a conductive substrate is electrochemically oxidized, and after a certain reaction time, a NiOOH / CoOOH composite layer with high crystallinity is pre-generated on its surface. After being washed with distilled water, it is dried at 50°C for 12 hours.
[0006] The nickel cobalt oxide attached to the conductive substrate can be any form of nickel cobalt oxide attached to a substrate such as carbon cloth or nickel foam, such as nickel cobalt oxide nanorods or nanosheets.
[0007] The nickel cobalt oxide attached to the conductive substrate can be generated in situ or obtained by coating a slurry made of powdered nickel cobalt oxide onto the conductive substrate.
[0008] The light under the specified illumination conditions is ultraviolet-visible light, and the light intensity must not exceed 90 mW / cm². 2 .
[0009] The photo-assisted electrochemical oxidation can be carried out in a three-electrode system or a two-electrode system. In a three-electrode system, the nickel cobalt oxide electrode is the working electrode, a platinum or carbon sheet is the counter electrode, and the Hg / HgO electrode is the reference electrode. In a two-electrode system, the nickel cobalt oxide electrode is the working electrode, a platinum or carbon sheet is the counter electrode, and no reference electrode is used. The object of illumination during the process is the nickel cobalt oxide electrode.
[0010] The electrochemical oxidation treatment is performed under constant voltage conditions. For nickel cobalt oxide grown in situ on a conductive substrate, when using a three-electrode system, the voltage range of the working electrode relative to the reference electrode is 0–1.2 V, and the treatment time is 10 minutes. When using a two-electrode system, the voltage range of the working electrode relative to the counter electrode is 0–1.3 V, and the treatment time is 10 minutes. For electrodes prepared by loading nickel cobalt oxide powder slurry onto a conductive substrate, when using a three-electrode system, the voltage range of the working electrode relative to the reference electrode is 0–1.1 V, and the treatment time is 15 minutes. When using a two-electrode system, the voltage range of the working electrode relative to the counter electrode is 0–1.2 V, and the treatment time is 15 minutes.
[0011] The electrolyte used in the photo-assisted electrochemical oxidation is a strongly alkaline aqueous solution, such as potassium hydroxide, sodium hydroxide, or a mixture of both, with a total concentration of 1 mol / L.
[0012] The beneficial effects of this invention are:
[0013] The present invention provides a method for improving the energy storage performance of nickel cobalt oxide cathodes through photo-assisted electrochemical oxidation. This method successfully enhances the electrochemical performance of nickel cobalt oxide under conventional environmental conditions through a short-time oxidation process. This method effectively generates a highly crystalline NiOOH / CoOOH composite thin layer on the surface of nickel cobalt oxide, increasing the active surface area and introducing new reaction pathways while maintaining the stability of the morphology and crystal structure of the nickel cobalt oxide substrate. This technology is not only low-cost, easy to operate, and allows for easy control of conditions and short processing time, but it can also be implemented on a large scale, overcoming many difficulties in traditional methods. It provides favorable support for strengthening the application of nickel cobalt oxide in energy storage devices, further improving the performance of aqueous zinc ion hybrid capacitors, and expanding their applications. Attached Figure Description
[0014] Figure 1 The images show scanning electron microscope (SEM) images of nickel cobalt oxide material before (a) and after (b) photo-assisted electrochemical oxidation treatment in Example 1.
[0015] Figure 2 The images show the XRD patterns of nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 1.
[0016] Figure 3 Raman images of nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 1.
[0017] Figure 4 The above are charge-discharge curves of the capacitor assembled from nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 1.
[0018] Figure 5 The above are charge-discharge curves of the capacitor assembled from nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 2.
[0019] Figure 6 The above are charge-discharge curves of the capacitor assembled from nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 3.
[0020] Figure 7 The above are charge-discharge curves of the capacitor assembled from nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 4.
[0021] Figure 8 The above are charge-discharge curves of the capacitor assembled from nickel cobalt oxide material before and after photo-assisted electrochemical oxidation treatment in Example 5. Detailed Implementation
[0022] Example 1:
[0023] A three-electrode system was adopted, with nickel cobalt oxide nanowires grown in situ on carbon cloth as the working electrode, a platinum sheet as the counter electrode, Hg / HgO as the reference electrode, and KOH aqueous solution as the electrolyte.
[0024] Working electrode preparation: A mixed solution of Ni(NO3)2, Co(NO3)2, and urea was prepared using distilled water as the solvent, with Ni(NO3)2 concentration of 3 g / L, Co(NO3)2 concentration of 6 g / L, and urea concentration of 9 g / L. The mixture was transferred to a hydrothermal reactor, and carbon cloth was placed in the solution. The reactor was sealed and heated to 100℃ and held at that temperature for 6 hours. After cooling, the carbon cloth was removed, washed with distilled water, and dried. Subsequently, it was sintered at 300℃ in air for 2 hours to obtain nickel cobalt oxide nanowire electrode material grown on carbon cloth.
[0025] Electrolyte preparation: Prepare a 1 mol / L KOH solution using distilled water as the solvent.
[0026] Photo-assisted electrochemical oxidation: The working electrode is fixed and connected using an L-shaped electrode clamp, with the working electrode plane parallel to the electrolyte surface and a distance of 0.5 cm between the working electrode plane and the electrolyte surface to ensure sufficient light intensity. A positive voltage of 1.2V relative to the reference electrode is applied to the working electrode, using a xenon lamp as the light source, and the light intensity is adjusted to 90 mW / cm². 2 Processing time: 10 minutes.
[0027] Figure 1 The images show scanning electron microscope (SEM) images of the electrode materials before and after photo-assisted electrochemical oxidation treatment. As can be seen from the images, the nickel cobalt oxide grown on the carbon cloth exhibits a nanowire array morphology. After photo-assisted electrochemical oxidation, the morphology of the nickel cobalt oxide did not change significantly, indicating that photo-assisted electrochemical oxidation does not destroy the morphological structure of the nickel cobalt oxide.
[0028] Figure 2 The figures show the XRD patterns of the electrode materials before and after photo-assisted electrochemical oxidation treatment. As can be seen from the figures, nickel cobalt oxide has a spinel structure. The positions and intensities of the diffraction peaks did not change significantly after photo-assisted electrochemical oxidation treatment, and no new diffraction peaks were generated, indicating that photo-assisted electrochemical oxidation did not change the main crystal structure of nickel cobalt oxide.
[0029] Figure 3 The figures show the Raman spectra of the electrode materials before and after photo-assisted electrochemical oxidation treatment. As can be seen from the figures, compared to untreated nickel cobalt oxide, at 458.1 cm⁻¹... -1 and 510.9cm -1New peaks appeared at the positions, corresponding to NiOOH and CoOOH respectively. The sharpness and narrow width of these two new peaks indicate high crystallinity. Since no new diffraction peaks were observed in the XRD pattern of the treated material, and the intensity of the original diffraction peaks did not decrease significantly, it can be concluded that the resulting NiOOH and CoOOH composite layer is relatively thin.
[0030] Both untreated and treated carbon cloth-based nickel cobalt oxide materials were used as cathodes in aqueous zinc ion hybrid capacitors, with zinc sheets as anodes and 6 mol / L KOH aqueous solution as electrolyte for charge-discharge tests. Figure 4 The figure shows the charge-discharge curves. As can be seen from the figure, at a current density of 1 A / g, the capacitor assembled with the treated electrode material has a specific capacitance of 1190 F / g, which is 3.5 times that of the capacitor assembled with the untreated material (338.3 F / g).
[0031] Example 2:
[0032] The preparation of the working electrode, electrolyte, and treatment system are the same as in Example 1, except that a positive voltage of 0.9 V relative to the reference electrode is applied to the working electrode during the photo-assisted electrochemical oxidation process, and the light intensity used is 70 mW / cm². 2 All other conditions are the same.
[0033] The capacitor assembly is the same as in Example 1. Figure 5 The figure shows the charge-discharge curves. As can be seen from the figure, at a current density of 1 A / g, the capacitor assembled with the treated nickel cobalt oxide material has a specific capacitance of 583.5 F / g, which is 1.7 times that of the capacitor assembled with the untreated material (338.3 F / g).
[0034] Example 3:
[0035] A two-electrode system was adopted, with nickel cobalt oxide nanosheets grown in situ on nickel foam as the working electrode, carbon sheet as the counter electrode, and KOH aqueous solution as the electrolyte.
[0036] Working electrode preparation: A mixed solution was prepared using a 2:1 (v / v) mixture of water and ethanol, with a Ni(NO3)2 concentration of 0.5 mmol / L, a Co(NO3)2 concentration of 1 mmol / L, and a cyclohexamethylenetetramine concentration of 2.2 mmol / L. The mixture was transferred to a hydrothermal reactor, and nickel foam was added to the solution. The reactor was sealed and heated to 90°C for 6 hours. After cooling, the nickel foam was removed, washed with distilled water, and dried. Subsequently, it was sintered at 400°C for 3 hours in air to obtain nickel cobalt oxide nanosheet electrode material grown on nickel foam.
[0037] Electrolyte preparation: Prepare a 1 mol / L KOH solution using distilled water as the solvent.
[0038] Photo-assisted electrochemical oxidation: The working electrode is fixed and connected using an L-shaped electrode clamp, with the working electrode plane parallel to the electrolyte surface and a distance of 0.5 cm between the working electrode plane and the electrolyte surface to ensure sufficient light intensity. A positive voltage of 1.3 V relative to the counter electrode is applied to the working electrode, using a xenon lamp as the light source, with the light intensity adjusted to 90 mW / cm². 2 Processing time: 10 minutes.
[0039] Nickel cobalt oxide materials on foamed nickel substrates that have not undergone photo-assisted electrochemical oxidation treatment and those that have undergone treatment were used as cathodes of aqueous zinc ion hybrid capacitors. Zinc sheets were used as anodes in both cases, and 6 mol / L KOH aqueous solution was used as electrolyte for charge-discharge tests. Figure 6 The figure shows the charge-discharge curves. As can be seen from the figure, at a current density of 1 A / g, the capacitor assembled with the treated electrode material has a specific capacitance of 829 F / g, which is 2.8 times that of the capacitor assembled with the untreated electrode material (294 F / g).
[0040] Example 4:
[0041] A three-electrode system was adopted, with a slurry made of nickel cobalt oxide nanowire powder loaded on nickel foam as the working electrode, a platinum sheet as the counter electrode, Hg / HgO as the reference electrode, and a mixed aqueous solution of KOH and NaOH as the electrolyte.
[0042] Working electrode preparation: Using N-methylpyrrolidone (NMP) as solvent, nickel cobalt oxide nanowire powder, polyvinylidene fluoride (PVDF) and carbon black were mixed and ground in a mass ratio of 8:1:1 to prepare a slurry. The slurry was pressed into nickel foam and then vacuum dried at 120°C for 12 hours.
[0043] Electrolyte preparation: Prepare a mixed solution of KOH and NaOH with a concentration of 0.5 mol / L each using distilled water as the solvent.
[0044] Photo-assisted electrochemical oxidation: The working electrode is fixed and connected using an L-shaped electrode clamp, with the working electrode plane parallel to the electrolyte surface and a distance of 0.5 cm between the working electrode plane and the electrolyte surface to ensure sufficient light intensity. A positive voltage of 1.1V relative to the reference electrode is applied to the working electrode, using a xenon lamp as the light source, and the light intensity is adjusted to 80 mW / cm². 2 Processing time: 15 minutes.
[0045] Both untreated and treated nickel cobalt oxide nanowires loaded with nickel foam were used as cathodes of an aqueous zinc ion hybrid capacitor, with zinc sheets as anodes and 6 mol / L KOH aqueous solution as electrolyte for charge-discharge tests. Figure 7The figure shows the charge-discharge curves. As can be seen from the figure, at a current density of 1 A / g, the capacitor assembled with the treated electrode material has a specific capacitance of 740.5 F / g, which is 4.0 times that of the capacitor assembled with the untreated electrode material (186.5 F / g).
[0046] Example 5:
[0047] A two-electrode system was adopted, with a slurry made of nickel cobalt oxide nanosheet powder loaded on carbon cloth as the working electrode, a carbon sheet as the counter electrode, and NaOH aqueous solution as the electrolyte.
[0048] Working electrode preparation: Using N-methylpyrrolidone (NMP) as solvent, nickel cobalt oxide nanosheet powder, polyvinylidene fluoride (PVDF) and carbon black were mixed and ground in a mass ratio of 8:1:1 to prepare a slurry. The slurry was pressed onto carbon cloth and then vacuum dried at 120°C for 12 hours.
[0049] Electrolyte preparation: Prepare a 1 mol / L NaOH aqueous solution using distilled water as the solvent.
[0050] Photo-assisted electrochemical oxidation: The working electrode is fixed and connected using an L-shaped electrode clamp, with the working electrode plane parallel to the electrolyte surface and a distance of 0.5 cm between the working electrode plane and the electrolyte surface to ensure sufficient light intensity. A positive voltage of 0.9 V is applied to the working electrode relative to the counter electrode, using a xenon lamp as the light source, with the light intensity adjusted to 70 mW / cm². 2 Processing time: 15 minutes.
[0051] Carbon cloth loaded with nickel cobalt oxide nanosheets that had not undergone photo-assisted electrochemical oxidation treatment and those that had undergone treatment were used as cathodes of aqueous zinc ion hybrid capacitors. Zinc sheets were used as anodes in both cases, and 6 mol / L KOH aqueous solution was used as electrolyte for charge-discharge tests. Figure 8 The figure shows the charge-discharge curves. As can be seen from the figure, at a current density of 1 A / g, the capacitor assembled with the treated electrode material has a specific capacitance of 546.8 F / g, which is 3.2 times that of the capacitor assembled with the untreated electrode material (170.8 F / g).
Claims
1. A method for improving the charge storage performance of a nickel cobaltate cathode by photo-assisted electrochemical oxidation, characterized in that Under certain light and electrolyte environment, a positive voltage is applied to the nickel cobaltate electrode, which promotes the pre-formation of a higher crystallinity NiOOH / CoOOH composite layer on the surface of the nickel cobaltate, the formation of the surface composite layer increases the active surface of the material, increases the new reaction path, thereby strengthening the intercalation and adsorption of electrolyte ions, which has a beneficial effect on the electricity storage performance.
2. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 1, characterized in that, The treated nickel cobaltate electrode can be any form of nickel cobaltate attached to a conductive substrate, such as carbon cloth, nickel foam, such as nickel cobaltate nanorods, nanosheets, etc.
3. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 2, characterized in that, The nickel cobaltate attached to the conductive substrate can be generated in situ, or a slurry made of powder state nickel cobaltate can be coated on the conductive substrate.
4. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 1, characterized in that, The light in the photo-assisted electrochemical oxidation process is ultraviolet-visible light, and the intensity of the light must be no higher than 90 mW / cm 2 .
5. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 1, characterized in that, The photo-assisted electrochemical oxidation can be carried out in a three-electrode system or a two-electrode system; when a three-electrode system is used, the nickel cobaltate electrode is the working electrode, platinum or carbon is the counter electrode, and Hg / HgO electrode is the reference electrode; when a two-electrode system is used, the nickel cobaltate electrode is the working electrode, platinum or carbon is the counter electrode, and no reference electrode is used; the object of the light in the process is the nickel cobaltate electrode.
6. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 5, characterized in that, The electrochemical oxidation treatment is under constant voltage conditions, for the in-situ grown nickel cobaltate on the conductive substrate, when a three-electrode system is used, the voltage range of the working electrode relative to the reference electrode is 0-1.2V, and the treatment time is 10 minutes; when a two-electrode system is used, the voltage range of the working electrode relative to the counter electrode is 0-1.3V, and the treatment time is 10 minutes; for the electrode prepared by loading the nickel cobaltate powder slurry on the conductive substrate, when a three-electrode system is used, the voltage range of the working electrode relative to the reference electrode is 0-1.1V, and the treatment time is 15 minutes; when a two-electrode system is used, the voltage range of the working electrode relative to the counter electrode is 0-1.2V, and the treatment time is 15 minutes.
7. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 1, characterized in that, The electrolyte used in the treatment is a strong alkaline solution, such as potassium hydroxide, sodium hydroxide or a mixture of the two, with a total concentration of 1 mol / L.
8. The method for improving the storage performance of the nickel cobaltate cathode by photo-assisted electrochemical oxidation according to claim 1, characterized in that, The nickel cobaltate cathode refers to the cathode of the aqueous zinc ion hybrid capacitor.