Preparation method of carbon-coated potassium intercalation hydrated vanadium pentoxide photoelectric cathode

Abstract

The invention discloses a preparation method of a carbon-coated potassium intercalation hydrated vanadium pentoxide photoelectric cathode, and relates to a preparation method of a photoelectric cathode. The invention aims to solve the problems that an existing material is large in band gap, poor in conductivity and insufficient in cycling stability, energy conversion efficiency and energy storage performance are difficult to consider at the same time, and the actual application process is restricted. The preparation method comprises the following steps: firstly, intercalating K < + > between hydrated vanadium pentoxide (VOH) layers through hydro-thermal synthesis to enhance the structural stability, and introducing a carbon source glucose in the synthesis process to realize in-situ carbon coating; and then mixing the material with a conductive agent and a binder to prepare a photoelectrode, assembling an improved CR2032 button cell containing a transparent window, and injecting an electrolyte to construct a photoresponse cell device. The obtained C-KVOH electrode shows enhanced electrochemical performance under illumination, the rate capability is excellent, the cycling stability is as high as 86%, and meanwhile, the C-KVOH electrode has good low-temperature adaptability and light response characteristics. The invention belongs to the technical field of new energy storage.

Description

Technical Field

[0001] The present invention relates to a method for preparing a photocathode, belonging to the technical field of new energy energy storage. Background Art

[0002] With the rapid development of portable electronic devices, environmental perception systems and next-generation flexible electronic products, traditional battery systems face severe challenges in terms of energy density, cycle stability and intelligent response ability. Photo-assisted Metal-Ion Batteries (PAMIBs) have shown broad prospects in realizing the integration of "collection-conversion-storage" due to their ability to efficiently convert light energy into electrical energy and drive electrochemical processes. In particular, Photo-assisted Zinc-Ion Batteries (PAZIB) have become a hot research and application direction due to their high safety, rich zinc resources and outstanding economy.

[0003] The key to improving the comprehensive performance of PAZIB lies in developing photocathode materials with both strong photoelectrochemical response and high zinc ion storage capacity. Although current common materials such as BiVO4, MoS2 and VO2 have certain photo-responsive activities, due to problems such as large band gaps, poor conductivity and insufficient cycle stability, it is difficult to balance energy conversion efficiency and energy storage performance, which restricts their practical application process.

[0004] In this context, vanadium-based layered materials are considered to be potential photocathode candidate materials due to their rich Zn 2+ intercalation / deintercalation channels and tunable electronic structures. In particular, by regulating the layer spacing and band gap structure through potassium ion intercalation and further introducing carbon coating to improve conductivity and light absorption ability, a C-KVOH composite photocathode material with a synergistic photo-electro-thermo-enhanced effect can be constructed. This material not only exhibits excellent photoelectric conversion efficiency, Zn 2+ diffusion kinetics and structural stability, but also overcomes problems such as complex synthesis and poor matching of traditional heterostructure materials, and has significant advantages in process simplicity and scalable integration.

[0005] For example, a patent for invention with a publication number of CN105140502A and an application date of July 10, 2015 discloses a potassium-intercalated vanadium pentoxide nanobelt cathode material for lithium batteries and a preparation method thereof. The preparation method is a sol-gel method, in which a vanadium source and an organic potassium compound are added to distilled water, heated and stirred until the solution turns light yellow, and then an appropriate amount of glycine is added. Stir and heat for several more hours, and then dry in an oven at 60 °C to obtain a precursor, and a uniform nanobelt-shaped potassium-intercalated vanadium pentoxide material is obtained after sintering. The molecular formula of the potassium-intercalated vanadium pentoxide material is KxV2O5 (0 < x ≤ 0.5), which is a fixed compound with potassium intercalated in the vanadium-oxygen layer on the basis of maintaining the layered structure of vanadium pentoxide. The potassium-intercalated vanadium pentoxide cathode material prepared by this method has excellent cycle stability and good rate performance, and the reaction conditions are mild, the process is simple, and it is suitable for large-scale production.

[0006] Another example is a patent for invention with a publication number of CN111244463A and an application date of February 11, 2020, which discloses a preparation method and application of a PEG-intercalated double-layer vanadium pentoxide electrode material. Using vanadium pentoxide powder as the vanadium source, polyethylene glycol PEG-6000 as the intercalated molecule, and hydrogen peroxide as the co-solvent, a vanadium pentoxide precursor is prepared by a hydrothermal method combined with a vacuum freeze-drying technique. The precursor is placed in a muffle furnace and sintered at 200 °C in an air atmosphere to obtain the PEG-intercalated double-layer vanadium pentoxide electrode material. This electrode material is used to prepare sodium-ion batteries. The operation of the present invention is simple and the reaction conditions are easy to control. During the preparation process, an appropriate amount of PEG is introduced into the interlayer of the double-layer vanadium pentoxide, which can significantly improve the sodium storage specific capacity, cycle performance and rate performance of the double-layer vanadium pentoxide electrode material.

[0007] However, it is difficult for the above-mentioned patented technologies to balance the energy conversion efficiency and energy storage performance.

[0008] Therefore, the PAZIB system based on the C-KVOH photocathode material not only provides an innovative path for the development of high-performance light-responsive energy storage devices, but also provides a solid material basis and technical support for the light-storage integration applications in scenarios such as wearable electronics and intelligent sensing microsystems. Summary of the Invention

[0009] In order to solve the problems that the existing materials have a large band gap, poor conductivity, insufficient cycle stability, it is difficult to balance the energy conversion efficiency and energy storage performance, which restricts their actual application process, the present invention further proposes a preparation method of a carbon-coated potassium-intercalated hydrated vanadium pentoxide photocathode.

[0010] The technical solution adopted by the present invention to solve the above problems is: the steps of the present invention include:

[0011] Step 1: Add vanadium pentoxide to deionized water, stir at room temperature, and simultaneously dropwise add hydrogen peroxide. Maintain stirring until a clear orange transparent solution is formed.

[0012] Step 2: Dissolve potassium chloride and glucose in deionized water respectively to form a mixed solution, and slowly add it to the solution obtained in Step 1. After ultrasonic treatment, a uniform precursor solution is obtained.

[0013] Step 3: Transfer the obtained precursor solution to a sealed high-pressure reaction kettle for hydrothermal reaction. After cooling, carry out suction filtration, alcohol-water washing, and drying to obtain a carbon-coated potassium ion intercalated hydrated vanadium pentoxide composite material.

[0014] Step 4: Mix the carbon-coated potassium ion intercalated hydrated vanadium pentoxide powder with the conductive agent acetylene black and the binder PVDF, add NMP solvent to form a uniform slurry, coat the slurry on a carbon paper current collector, and carry out vacuum drying to form a photoanode.

[0015] Step 5: Based on an improved CR2032-type battery case with a light-transmitting window, assemble a photoanode, a Whatman glass fiber separator, a 3M Zn(CF3SO3)2 aqueous electrolyte, a zinc sheet cathode, a gasket, and a stainless steel top cover in sequence, and seal and press them together to obtain a light-assisted zinc ion battery.

[0016] Further, the molar ratio of vanadium pentoxide to potassium chloride is 1:4.

[0017] Further, the hydrothermal reaction temperature is 180–220 °C, preferably 200 °C, and the reaction time is 3–5 hours.

[0018] Further, the electrode slurry is composed of C-KVOH, acetylene black, and PVDF, and the mass ratio is 7:2:1, and the solvent is NMP.

[0019] Further, the active material loading of the photoanode is 1 mg / cm 2 , and the drying temperature is 60 °C.

[0020] Further, PAZIB works under the illumination condition of 100 mW·cm-2, the specific capacity reaches 347 mAh·g-1, and the capacity retention rate reaches 86% after 4000 cycles.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. The present invention adopts a strategy combining potassium ion intercalation and carbon coating, introduces potassium ion intercalation into layered hydrated vanadium pentoxide, and prepares a C-KVOH photoanode material with a photo-electro-thermo synergistic enhancement effect.

[0023] 2. The process of the present invention is simple and highly controllable. The obtained electrode has excellent specific capacity, light response ability and low-temperature adaptability, and can be widely applied to photo-assisted zinc-ion batteries and portable energy devices, providing a new solution for constructing a new type of green energy storage system suitable for multiple scenarios;

[0024] 3. The present invention has low cost, is easy to implement and suitable for large-scale preparation. It adopts room-temperature stirring and one-step synthesis with consistent temperature, without the need for complex equipment and high-temperature sintering, and is suitable for large-scale material preparation and device integration;

[0025] 4. The synergistic enhancement mechanism of the present invention significantly improves the battery performance. K + intercalates to regulate the layer spacing and stabilize the structure, and carbon coating improves the conductivity and light absorption ability, realizing dual-channel enhancement of photoelectricity and photothermal, and effectively improving the specific capacity and rate performance of the battery;

[0026] 5. The present invention has strong light response and low-temperature adaptability. The band gap is reduced to 2.41 eV, with excellent visible light response; it still maintains more than 80% of the capacity under the low-temperature condition of -10 °C, showing superior environmental adaptability;

[0027] 6. The present invention has practical application ability and expandability. The constructed photo-assisted battery can drive devices such as electronic calendars and electric model cars, and has the function of "charging while using" in weak light, no mains power, and cold environments, and is suitable for various scenarios such as wearable, sensing, and remote power supply;

[0028] 7. The present invention provides a technical path for the development of photoenergy storage integration devices. The present invention innovatively integrates ion regulation, carbon coating and light response enhancement mechanisms, providing a realizable structure and process reference for the next-generation photoenergy storage integrated energy system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the XRD pattern of the carbon-coated K + intercalated hydrated vanadium pentoxide (C-KVOH) photocathode obtained in the embodiment of the present invention. The peak position shift of the (001) crystal plane can be clearly observed, indicating that K + is successfully intercalated and the layer spacing is adjusted;

[0030] Figure 2 is the XPS pattern of the C-KVOH photocathode;

[0031] Figure 3 is the scanning electron microscope (SEM) image of the C-KVOH sample;

[0032] Figure 4 is the high-resolution transmission electron microscope (HRTEM) image of the C-KVOH;

[0033] Figure 5UV-Vis absorption spectrum of C-KVOH;

[0034] Figure 6 Schematic diagram of the current-time response (I-t) curve of the C-KVOH photocathode under illumination and non-illumination conditions;

[0035] Figure 7 Rate performance diagram of C-KVOH-based PAZIB under light and dark conditions;

[0036] Figure 8 Practical application photo of PAZIB composed of C-KVOH photocathode working in a commercial electronic calendar under simulated sunlight conditions;

[0037] Figure 9 Schematic diagram of the working mechanism of the C-KVOH-based photocathode under illumination. Detailed implementation manners

[0038] Detailed implementation manner one: As Figures 1 to 9 shown, a preparation method of a carbon-coated potassium intercalated vanadium pentoxide photocathode specifically includes the following steps:

[0039] Step one: Add 0.72 g of vanadium pentoxide (V2O5) to 40 ml of deionized water, stir at room temperature, and slowly dropwise add 8 ml of hydrogen peroxide (H2O2) while continuously stirring until a clear orange transparent solution is formed;

[0040] Step two: Dissolve 0.147 g of potassium chloride (KCl) and 0.072 g of glucose in 10 ml of deionized water respectively to form a mixed solution, slowly add it to the solution obtained in step one, and perform ultrasonic treatment for 10 min to obtain a uniform precursor solution;

[0041] Step three: Transfer the obtained precursor solution to a sealed high-pressure reaction kettle, perform hydrothermal reaction at 200 °C for 4 h, cool, perform suction filtration, wash with alcohol and water, and dry at 60 °C to obtain a carbon-coated potassium ion intercalated vanadium pentoxide composite material (C-KVOH);

[0042] Step four: Mix C-KVOH powder, conductive agent acetylene black, and binder PVDF in a mass ratio of 7:2:1, add NMP solvent to form a uniform slurry, coat the slurry on a carbon paper current collector, and perform vacuum drying at 60 °C to form a photocathode, and the active material loading of the photocathode is 1 mg / cm 2 ;

[0043] Step 5: Based on the improved CR2032 button cell case with a light-transmitting optical window, assemble the photocathode, Whatman glass fiber separator, 200 μL of 3M Zn(CF3SO3)2 aqueous electrolyte, zinc sheet anode, gasket, and stainless steel top cover in sequence, and perform encapsulation and pressing to obtain a photo-assisted zinc-ion battery (PAZIB).

[0044] Example

[0045] Example 1

[0046] Step 1: Weigh 0.72 g of vanadium pentoxide (V2O5) and add it to 40 ml of deionized water. Slowly drop 8 ml of hydrogen peroxide (H2O2) under magnetic stirring conditions, stir at room temperature, and maintain the stirring reaction for 30 min. The solution gradually becomes clear orange.

[0047] Let it stand and observe until no more bubbles are released from the system to obtain the V2O5-H2O2 reaction solution.

[0048] Step 2: In another beaker, weigh 0.147 g of potassium chloride (KCl) and 0.072 g of glucose, add 10 ml of deionized water, and stir for 10 min to fully dissolve them to obtain a uniform K + / carbon source mixed solution.

[0049] Step 3: Slowly add the K + / carbon source mixed solution obtained in Step 2 to the V2O5-H2O2 solution obtained in Step 1, and perform ultrasonic treatment for 10 min to promote the uniform mixing of the precursors, finally forming a stable and uniform precursor solution.

[0050] Step 4: Transfer the above precursor solution to a 100 ml polytetrafluoroethylene-lined autoclave, seal it, and place it in an oven for hydrothermal reaction at 200 °C for 4 h (240 min).

[0051] After the reaction, naturally cool it to room temperature, take out the product, perform vacuum filtration, and wash it alternately with anhydrous ethanol and deionized water 3 times to remove the surface residues. Finally, dry it in vacuum at 60 °C for 6 h to obtain carbon-coated potassium ion intercalated hydrated vanadium pentoxide material (C-KVOH).

[0052] Step 5: Weigh and mix the obtained C-KVOH powder, acetylene black, and PVDF according to a mass ratio of 7:2:1, add an appropriate amount of NMP solvent, and perform ultrasonic dispersion for 30 min to prepare a uniform slurry.

[0053] Drop the slurry onto a carbon paper current collector of the Hesen H3P030N model, and dry it in vacuum at 60 °C for 12 h to form a photocathode with a uniform thickness, and control the active material mass to be 1 mg.

[0054] Step 6: Using the improved CR2032 button battery case as the outer shell, punch a circular light window with a diameter of 11 mm at the top and attach a high-transparency optical glass.

[0055] Assemble the battery in the following order: C-KVOH photoanode → Whatman glass fiber separator → drop 200 μL of 3M Zn(CF3SO3)2 aqueous electrolyte → zinc sheet cathode → gasket → stainless steel top cover, encapsulate and press, to obtain a prototype photo-assisted zinc-ion battery (PAZIB) with light response ability.

[0056] Characterize the sample of Example 1. Figure 1 All the peaks in correspond to the characteristic peaks of C-KVOH respectively. Figure 2 The XPS spectrum results in are corresponding to XRD, indicating the successful synthesis of C-KVOH composite material. As Figure 3 shown, C-KVOH is a foam-like three-dimensional structure composed of stacked ultrathin nanosheets. The high-resolution transmission electron microscopy (HRTEM) image of C-KVOH shows clear crystal lattice fringes, and the interlayer spacing is Figure 4 which further proves the influence of K + intercalation on the crystal structure. As Figure 5 shown, compared with un-intercalated VOH, C-KVOH has stronger absorption in the range of 500 - 800 nm, and the band gap decreases from 2.57 eV to 2.41 eV.

[0057] Perform optoelectronic and energy storage performance tests on the sample of Example 1. is the current-time response (I-t) curve of the C-KVOH photocathode under illumination and non-illumination conditions, and the comparison shows an enhanced light response ability. As Figure 6 shown. The rate performance graphs of the C-KVOH-based PAZIB under light and dark conditions. When the current density ranges from 500 to 5000 mA g-1, the capacities are 454 and 347 mAh g-1 respectively. As Figure 7 shown, the practical application photo of the PAZIB composed of the C-KVOH photocathode working in a commercial electronic calendar under simulated sunlight conditions shows that it can continuously work for more than 54 hours. As Figure 8 shown. Under illumination conditions, after C-KVOH absorbs light energy, photo-generated electron-hole pairs are generated. The holes can participate in the oxidation reaction to assist Zn 2+ deintercalation and accelerate the electrochemistry reaction kinetics; the electrons are transmitted to the cathode through the external circuit to complete the energy conversion. This optoelectronic-thermophotonic coupling effect can significantly improve the specific capacity and rate performance of the battery, reduce polarization, and extend the cycle life. As Figure 9 shown.

[0058] Example 2

[0059] Step 1: Weigh 0.72 g of vanadium pentoxide (V2O5) and add it to 40 ml of deionized water. Slowly add 8 ml of hydrogen peroxide (H2O2) under magnetic stirring conditions. Stir at room temperature and maintain the stirring reaction for 30 min. The solution gradually turns into a clear orange color;

[0060] Let it stand and observe until no more bubbles are released from the system to obtain the V2O5-H2O2 reaction solution;

[0061] Step 2: In another beaker, weigh 0.147 g of potassium chloride (KCl) and 0.00545 g of glucose, add 10 ml of deionized water, and stir for 10 min to fully dissolve them to obtain a uniform K + / carbon source mixed solution;

[0062] Step 3: Slowly add the K + / carbon source mixed solution obtained in Step 2 into the V2O5-H2O2 solution obtained in Step 1, and perform ultrasonic treatment for 10 min to promote the uniform mixing of the precursors, finally forming a stable and uniform precursor solution;

[0063] Step 4: Transfer the above precursor solution to a 100 ml polytetrafluoroethylene-lined autoclave, seal it, and place it in an oven for hydrothermal reaction at 180 °C for 4 h (240 min);

[0064] After the reaction is completed, naturally cool it to room temperature, take out the product, filter it by vacuum filtration, and wash it alternately with absolute ethanol and deionized water 3 times to remove the surface residues. Finally, dry it in vacuum at 60 °C for 6 h to obtain carbon-coated potassium-ion intercalated hydrated vanadium pentoxide material (C-KVOH);

[0065] Step 5: Weigh and mix the obtained C-KVOH powder, acetylene black, and PVDF according to a mass ratio of 7:2:1, add an appropriate amount of NMP solvent, and perform ultrasonic dispersion for 30 min to prepare a uniform slurry;

[0066] Drop the slurry onto a carbon paper current collector of the Hesen H3P030N model, and dry it in vacuum at 60 °C for 12 h to form a photoelectrode with a uniform thickness, and control the mass of the active substance to be 1 mg;

[0067] Step 6: Using an improved CR2032 button battery case as the outer shell, punch a circular light window with a diameter of 11 mm at the top and attach a highly transparent optical glass;

[0068] Assemble the battery in the following order: C-KVOH photoanode → Whatman glass fiber separator → Drop 200 μL of 3M Zn(CF3SO3)2 aqueous electrolyte → Zinc sheet cathode → Gasket → Stainless steel top cover, encapsulate and press it to obtain a prototype photo-assisted zinc-ion battery (PAZIB) with light response ability.

[0069] In the comparative experiment, the prepared electrode still maintained a high capacity retention rate of up to 78%. Although the capacity decreased slightly at low temperatures, it was still higher than that of the traditional VOH sample, indicating that the process window of this system is relatively wide and has good controllability.

[0070] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention and is based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement of the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a carbon-coated potassium-intercalated hydrated vanadium pentoxide photocathode, characterized in that, The specific steps include: Step 1: Add vanadium pentoxide to deionized water, stir at room temperature, and simultaneously dropwise add hydrogen peroxide, and maintain stirring until a clear orange transparent solution is formed; Step 2: Dissolve potassium chloride and glucose in deionized water respectively to form a mixed solution, and slowly add it to the solution obtained in Step 1, and obtain a uniform precursor solution through ultrasonic treatment; Step 3: Transfer the obtained precursor solution to a sealed high-pressure reaction kettle, carry out hydrothermal reaction, after cooling, carry out suction filtration, alcohol-water washing and drying to obtain a carbon-coated potassium ion intercalated hydrated vanadium pentoxide composite material; Step 4: Mix the carbon-coated potassium ion intercalated hydrated vanadium pentoxide powder with the conductive agent acetylene black and the binder PVDF, add NMP solvent to form a uniform slurry, coat the slurry on a carbon paper current collector, and carry out vacuum drying to form a photoanode; Step 5: Based on an improved CR2032 button cell case with a light-transmitting window, sequentially assemble a photoanode, a Whatman glass fiber separator, a 3M Zn(CF3SO3)2 aqueous electrolyte, a zinc sheet cathode, a gasket and a stainless steel top cover, and encapsulate and press to obtain a light-assisted zinc ion battery.

2. The preparation method of a carbon-coated potassium intercalated hydrated vanadium pentoxide photoanode according to claim 1, characterized in that The molar ratio of vanadium pentoxide to potassium chloride is 1:

4.

3. The preparation method of a carbon-coated potassium intercalated hydrated vanadium pentoxide photocathode according to claim 1, wherein The hydrothermal reaction temperature is 180–220 °C, preferably 200 °C, and the reaction time is 3–5 hours.

4. A method for preparing a carbon-coated potassium-intercalated hydrated vanadium pentoxide photocathode according to claim 1, characterized in that, The electrode slurry is composed of C-KVOH, acetylene black and PVDF, and the mass ratio is 7:2:1, and the solvent is NMP.

5. The preparation method of a carbon-coated potassium intercalated hydrated vanadium pentoxide photoanode according to claim 1, wherein The active material loading of the optoelectrode is 1 mg / cm 2 , and the drying temperature is 60 °C.

6. A method for preparing a carbon-coated potassium-intercalated hydrated vanadium pentoxide photoanode according to claim 1, characterized in that, PAZIB works under the illumination condition of 100 mW·cm-2, the specific capacity reaches 347 mAh·g-1, and the capacity retention rate reaches 86% after 4000 cycles.

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