In-situ gel electrolyte for aqueous zinc ion capacitor and preparation method and application thereof

Abstract

This invention discloses an in-situ gel electrolyte for aqueous zinc-ion capacitors, its preparation method, and its application. The preparation method of the in-situ gel electrolyte includes the following steps: uniformly dispersing graphene oxide in an aqueous solution containing organic polymer monomers, a crosslinking agent, and zinc salt to obtain a precursor dispersion; uniformly coating the precursor dispersion onto the surface of a zinc foil after oxide removal; and polymerizing the precursor dispersion on the zinc foil using ultraviolet irradiation to obtain the in-situ gel electrolyte. The in-situ gel electrolyte of this invention has a stable interface, low impedance, and can effectively prevent dendrite growth. Using graphene oxide as a photoinitiator, it is stable, non-toxic, and pollution-free, and the process is simple, efficient, and has mild reaction conditions with strong controllability.

Description

Technical Field

[0001] This invention relates to the field of gel electrolyte technology, and in particular to an in-situ gel electrolyte for aqueous zinc ion capacitors, its preparation method, and its application. Background Technology

[0002] In recent years, with the increasing severity of fossil fuel shortages and environmental pollution, the demand for energy storage devices with high energy / power density, high safety, and low cost has become increasingly urgent. Hybrid capacitors, which combine the advantages of capacitors and metal-ion batteries, have attracted widespread attention. Zinc-ion capacitors, in particular, have significant advantages in terms of high energy density and low cost.

[0003] However, using zinc metal as the negative electrode in hybrid capacitors currently suffers from severe problems such as dendrite growth, hydrogen evolution corrosion, and the generation of inactive byproducts. Polymer gel electrolytes can alleviate these problems to some extent, but they still have inherent limitations, including complex preparation processes, low ion transport efficiency, and poor electrolyte-electrode interfaces, hindering their practical application. Patent CN113782844B discloses a method for preparing a hydrogel electrolyte for an aqueous zinc-ion energy storage battery. This method involves heating and polymerization followed by immersion in the electrolyte, resulting in a complex process and poor electrochemical performance. Furthermore, patent CN118213636A discloses a method for preparing a transparent, flexible zinc-ion hydrogel electrolyte, which also employs thermally initiated polymerization, leading to a complex process and poor mechanical and electrochemical performance.

[0004] Therefore, it is necessary to develop a convenient, efficient, environmentally friendly, and low-cost process to prepare gel electrolytes with stable interfaces and high ion transport efficiency for high-performance zinc-ion capacitors, so as to promote their industrial application. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing an in-situ molding method for preparing gel electrolytes and its application in zinc-ion capacitors. This method utilizes graphene oxide as a structurally stable, non-toxic, pollution-free, and low-cost ultraviolet photoinitiator. Using ultraviolet irradiation, oxygen-containing groups on the graphene oxide are detached to form free radicals, which guide the polymerization of organic polymer monomers into chains. Under the condition that the crosslinking agent monomers participate in the reaction, a gel network is formed on the zinc foil surface. This invention provides a simple and effective method with rapid molding and a stable interface.

[0006] This invention also provides applications of this in-situ gel electrolyte.

[0007] The objective of this invention is achieved by at least one of the following technical solutions.

[0008] The first aspect of this invention is to provide a method for preparing an in-situ gel electrolyte, comprising the following steps:

[0009] (1) Graphene oxide was uniformly dispersed in an aqueous solution of zinc salt containing organic polymer monomers and crosslinking agent monomers by magnetic stirring and ultrasonic dispersion to obtain a precursor dispersion.

[0010] (2) The precursor dispersion is uniformly coated on the surface of zinc foil after oxide removal;

[0011] (3) The precursor dispersion was polymerized on zinc foil by ultraviolet irradiation to obtain in-situ gel electrolyte.

[0012] The method for preparing in-situ gel electrolyte according to the first aspect of the present invention has at least the following beneficial effects:

[0013] This invention utilizes graphene oxide as a photoinitiator to generate free radicals that guide the polymerization of organic polymer monomers. Graphene oxide, as a photoinitiator, is stable, non-toxic, and pollution-free. The precursor dispersion is directly polymerized on the zinc foil surface to form a gel electrolyte, resulting in a stable electrolyte-electrode interface with low interfacial impedance. This method for in-situ UV-curing of the gel electrolyte is simple, efficient, and has mild reaction conditions with strong controllability. Furthermore, the graphene oxide remaining in the gel electrolyte after curing is stable, and the unremoved oxygen-containing functional groups, due to their affinity for zinc ions, can regulate the electric field distribution inside the gel electrolyte, thereby effectively slowing down zinc dendrite growth.

[0014] In some embodiments of the present invention, the zinc salt includes one or more of zinc sulfate, zinc chloride, zinc perchlorate, and zinc acetate; preferably, the zinc salt is zinc sulfate; the concentration of the aqueous solution of the zinc salt is 0.5–6 mol / kg. -1 The organic polymer monomer includes one or more of acrylamide monomers, acrylate monomers, styrene monomers, and methyl methacrylate monomers; preferably, the organic polymer monomer is an acrylamide monomer; the ratio of the organic polymer monomer to the zinc salt aqueous solution is (1-3) g: 10 mL, and the mass of the crosslinking agent is 1-2% of the mass of the organic polymer monomer; preferably, the crosslinking agent is N,N'-methylenebisacrylamide.

[0015] In some embodiments of the present invention, the graphene oxide sheet has a diameter of 50 nm to 5 μm and a mass of 0.5% to 5% of the mass of the acrylamide monomer.

[0016] In some embodiments of the present invention, the zinc foil may be square, round, or other shapes; the method for removing oxides may be one or more of grinding and polishing or acid leaching; the grinding and polishing may utilize tools such as sandpaper, grinding wheel, and polishing machine; the acid leaching may utilize one or more of hydrochloric acid, sulfuric acid, acetic acid, and citric acid, with a concentration of 5-20%.

[0017] In some embodiments of the present invention, the ultraviolet wavelength of the ultraviolet irradiation method is 300-400 nm, the power of the ultraviolet light source is 5-120 W, and the irradiation polymerization time is 0.5-2 h.

[0018] A second aspect of the present invention is to provide an in-situ gel electrolyte prepared by the above method.

[0019] A third aspect of the present invention is to provide a zinc-ion capacitor containing the above-described in-situ gel electrolyte.

[0020] In some embodiments of the present invention, the zinc ion capacitor of the in-situ gel electrolyte includes the zinc foil and the in-situ gel electrolyte formed thereon, as well as a positive electrode with capacitive properties; the positive electrode and the zinc foil sandwich the gel electrolyte in the middle to form a sandwich structure, and finally encapsulate it into a zinc ion capacitor.

[0021] In some embodiments of the present invention, the positive electrode sheet can be coated or molded onto a conductive substrate by means of coating, roll forming, spraying, or other processes. The electrode paste consists of electrode material, conductive additives, and binders. The electrode material can be one or more of activated carbon materials or metal oxides such as vanadium pentoxide and manganese dioxide. The conductive additives can be carbon black such as Super P and acetylene black. The binders can be polymer binders such as PVDF, PVA, and PVP. The conductive substrate can be materials such as aluminum foil, copper foil, stainless steel foil, carbon paper, and carbon cloth.

[0022] In some embodiments of the present invention, the packaging method may be button cell battery casing or soft pack packaging.

[0023] A fourth aspect of the present invention is to provide a method for manufacturing the above-described zinc-ion capacitor, comprising the following steps.

[0024] (1) The precursor dispersion was coated on the negative electrode and the positive electrode respectively, and then irradiated with ultraviolet light to a semi-formed state. Specifically, the fluidity of the precursor dispersion decreased and the inverted electrode did not drip.

[0025] (2) Turn the zinc negative electrode over and cover it on the positive electrode, and continue to irradiate it with ultraviolet light from the side until it is fully formed, thus obtaining a sandwich structure;

[0026] (3) Package and test the obtained sandwich structure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Compared with traditional initiators, such as persulfides, acrylates, ketone amines, and benzophenone derivatives, some of these initiators have poor water solubility, while others are unstable and easily decompose. In this invention, graphene oxide is used as a photoinitiator, which is stable, non-toxic, and pollution-free. Furthermore, due to the abundant oxygen-containing groups on the carbon skeleton of graphene oxide, it has good water solubility; after gel polymerization, the sheet-like graphene oxide is uniformly distributed inside the gel, and the remaining oxygen-containing groups have zinc ion-loving properties, which can further form ion channels, regulate the zinc ion transport path, reduce internal impedance, and improve ionic conductivity.

[0029] (2) Compared with the non-in-situ gel polymerization process, the present invention uses an in-situ initiated polymerization process. The in-situ polymerization process is simple, the interface is stable, the interface impedance is low, the growth of dendritic crystals is slowed down, and problems such as hydrogen evolution corrosion and electrode passivation caused by high gel water content are reduced.

[0030] (3) Compared with thermally initiated polymerization, this invention uses ultraviolet (UV) initiated polymerization, which is highly efficient and controllable, and produces high-quality gels. Furthermore, UV polymerization allows for precise control of the light source to locate and regulate the polymerization reaction, and avoids the potential impact of high temperatures on electrolytes or other components. It is also less susceptible to changes in environmental conditions or fluctuations in control conditions, resulting in higher stability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the preparation process of UV in-situ gel electrolyte based on zinc foil;

[0032] Figure 2 This is a photograph of an ultraviolet in-situ gel electrolyte based on zinc foil.

[0033] Figure 3 SEM image of in-situ gel electrolyte;

[0034] Figure 4a This is a diagram of the electrode-electrolyte interface in Example 1;

[0035] Figure 4b This is a diagram of the electrode-electrolyte interface for Comparative Example 1.

[0036] Figure 5 The initial deposition potential diagrams for Example 1 and Comparative Example 1 are shown.

[0037] Figure 6 The constant current charge-discharge (1 mA cm) of Example 1 (Figure a) and Comparative Example 1 (Figure b) is shown. -2 / 1mAh cm -2 Long-cycle test chart;

[0038] Figure 7a 1mA cm-2 / 1mAh cm -2 Surface morphology of the zinc anode in Example 1 after 100 hours of cycling;

[0039] Figure 7b 1mA cm -2 / 1mAh cm -2 Surface morphology of zinc anode in Comparative Example 1 after 100 hours of cycling;

[0040] Figure 8 Cyclic voltammetry curves (scan rate 30 mV / s) of zinc-ion capacitors in Example 2 and Comparative Example 2. -1 );

[0041] Figure 9 Long-cycle testing (current density 1 A g) of zinc-ion capacitors in Example 2 and Comparative Example 2. -1 );

[0042] Figure labels: 1. Zinc foil; 2. In-situ gelled electrolyte precursor dispersion; 3. In-situ gelled electrolyte; 4. Ultraviolet light source; Step ①: Uniformly coat the precursor dispersion onto the zinc foil; Step ②: Ultraviolet irradiation until the precursor gels. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0044] Example 1

[0045] This embodiment 1 provides an ultraviolet-initiated in-situ polymer gel electrolyte and applies it to the assembly of a coin-type zinc symmetric battery. The specific operation steps are as follows:

[0046] (1) Dissolve 0.5g acrylamide (AM) and 2.5mg N,N-methylenebisacrylamide (MBA, crosslinking agent) in 5mL of 1M zinc sulfate (ZnSO4) electrolyte and stir for 30min; add 5mg of graphene oxide (GO) with a sheet diameter of 50-200nm to obtain a mixture; stir the obtained mixture magnetically for 3h and sonicate for 1h to obtain a uniformly dispersed precursor dispersion.

[0047] (2) Take two pieces of zinc foil (diameter) Thickness h = 100 μm), polish the surface with 2000-mesh sandpaper, then immerse it in 10% hydrochloric acid solution until uniform bubbles are generated on the zinc foil surface. Rinse with deionized water and wipe dry with lint-free paper to obtain the treated zinc foil. Take 100 μL of the precursor dispersion obtained in step (1) and drop it evenly onto the surface of the treated zinc foil. Irradiate it with a UV lamp (365 nm, 60 W) for 10 minutes to allow the precursor dispersion to polymerize in situ on the zinc foil but not completely polymerize, and it has a certain viscosity and adheres to the zinc foil.

[0048] like Figure 2 As shown, the rheological properties of the precursor dispersion coated on zinc foil are significantly reduced after ultraviolet irradiation, and it can be picked up with tweezers and adhered to the zinc foil.

[0049] (3) Invert one of the zinc foils with the incompletely polymerized precursor dispersion obtained in step (2) and cover it on the other zinc foil so that the dispersion between the two zinc foils is fully mixed. Then irradiate it with a UV lamp for 10 minutes to allow it to fully polymerize.

[0050] like Figure 3 As shown, the SEM image of the UV in situ gel electrolyte reveals the interconnected pore structure and network structure.

[0051] like Figure 4a As shown, the SEM cross-sectional image of the UV-Vis in-situ gel electrolyte reveals a tight electrode-electrolyte interface, while Figure 4b The intermediate heat-induced non-in-situ gel electrolyte has obvious gaps between itself and the electrode.

[0052] (4) Obtain the in-situ Zn||Zn structure and assemble it into a symmetrical cell (CR2025).

[0053] Performance testing

[0054] The initial deposition potential diagram of the symmetrical cell in Example 1 was obtained by measurement as follows: Figure 5 As shown, the voltage is 0.0684V, while Comparative Example 1 is 0.0985V. For example... Figure 6 The figure shown is 1mA cm -2 / 1mAh cm -2 The following long-cycle test diagram shows that Example 1 ran stably for 4100 hours, while Comparative Example 1 experienced unstable voltage and large fluctuations during the cycle, and failed due to short circuit in less than 1100 hours. Figure 7a and Figure 7b 1mA cm -2 / 1mAh cm -2 After cycling for 100 hours under the test conditions, the surface electron micrograph of the zinc foil obtained by peeling off the gel is shown in the figure. Figure 7a As shown, the deposition state of Example 1 is good, exhibiting a dense, uniform, and flat lamellar structure, while Figure 7bComparative Example 1 shows a loose, tilted, or upright intercalation.

[0055] Example 2

[0056] This embodiment 2 provides a UV-initiated in-situ polymer gel electrolyte and applies it to the assembly of a button-type zinc ion capacitor. The preparation process is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0057] (1) Weigh 0.1g of polyvinylidene fluoride (PVDF) and add it to 1mL of N-methylpyrrolidone (NMP). Mix them evenly in a planetary centrifugal mixer to obtain a viscous liquid. Weigh 0.2g of conductive carbon black (Super P) and 0.7g of activated carbon (AC), grind them in a mortar and mix them evenly to obtain a powder mixture. Add the powder mixture to 4mL of N-methylpyrrolidone (NMP) and mix it evenly in a planetary centrifugal mixer to obtain a dispersion. Mix the viscous liquid and the dispersion evenly in a planetary centrifugal mixer to obtain a coating slurry.

[0058] (2) The slurry obtained in step (1) is uniformly coated onto aluminum foil with a coating thickness of 150 μm. After coating, it is transferred to a vacuum oven and vacuum dried at 80°C for 24 hours. Subsequently, the obtained product is cut into pieces with a diameter of... The positive electrode sheet was obtained; the obtained AC positive electrode sheet was soaked in 1M ZnSO4 electrolyte solution for 6 hours to ensure that the electrolyte solution completely penetrated the electrode sheet.

[0059] (3) Further, the in-situ gel electrolyte was prepared using the same steps and assembled into a zinc ion capacitor. The difference between this Example 2 and Example 1 is that one of the zinc foils in step (2) of Example 1 was replaced with the AC positive electrode obtained in step (2) of Example 2, and finally an in-situ Zn||AC structure was obtained and assembled into a zinc ion capacitor (CR2025).

[0060] Performance testing

[0061] like Figure 8 The scan rate is 30 mV / s -1 The cyclic voltammetry curve, after data processing, yields the results for Example 2 at 30 mV / s. -1 It has 280.4 F g at a scan rate. -1 The specific capacity of [the sample] is higher than that of Comparative Example 2 (217.4 F g). -1 .like Figure 9 For current density 1A g -1 In long-cycle testing, Example 2 ran for over 1800 cycles, and the specific capacity remained at its initial capacity (172.6 mAh g). -1The efficiency of the first sample was 98.4%, and the coulomb efficiency remained at 92.4%, while the second sample failed after about 800 cycles.

[0062] Comparative Example 1

[0063] Comparative Example 1 relates to a thermally initiated in-situ polymer gel electrolyte and its application in assembling a coin-type zinc symmetric battery. The specific operation steps are as follows:

[0064] (1) Weigh 0.5g AM, 2.5mg MBA and 5mg potassium persulfate (KPS) and dissolve them completely in 5mL of 1M ZnSO4 solution to form a precursor solution; inject the precursor solution into a glass mold (diameter... (Depth h = 1 mm), and heated in an oven at 60°C for 2 hours to obtain gel electrolyte.

[0065] (2) The pretreated zinc foil is used as the two electrodes and sandwiched between the two sides of the gel electrolyte obtained in step (1) to form a Zn||Zn structure and assemble it into a symmetrical battery (CR2025).

[0066] Comparative Example 2

[0067] Comparative Example 2 relates to a thermally initiated in-situ polymer gel electrolyte and its application in assembling a button-type zinc-ion capacitor. The specific operation steps are as follows:

[0068] The difference between Comparative Example 2 and Example 2 is that the in-situ molded gel electrolyte in Example 2 is replaced with the gel electrolyte obtained in step (1) of Comparative Example 1, resulting in a Zn||AC structure, which is then assembled into a zinc ion capacitor (CR2025).

[0069] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an in-situ gel electrolyte for an aqueous zinc-ion capacitor, characterized in that: Includes the following steps: (1) Graphene oxide is uniformly dispersed in an aqueous solution of zinc salt containing organic polymer monomers and crosslinking agent monomers by stirring and ultrasonic dispersion to obtain a precursor dispersion; the crosslinking agent is N,N'-methylenebisacrylamide; the zinc salt in the aqueous solution includes one or more of zinc sulfate, zinc chloride, zinc perchlorate, and zinc acetate; the concentration of the aqueous solution of zinc salt is 0.5~6 mol kg. -1 The organic polymer monomer includes one or more of acrylamide monomers, acrylate monomers, styrene monomers, and methyl methacrylate monomers; the ratio of the organic polymer monomer to the zinc salt aqueous solution is (1~3) g: 10 mL, and the mass of the crosslinking agent monomer is 1~2% of the mass of the organic polymer monomer; (2) The precursor dispersion is uniformly coated on the surface of zinc foil after oxide removal; (3) The precursor dispersion was polymerized on zinc foil to a semi-formed state by ultraviolet irradiation to obtain in-situ gel electrolyte.

2. The method for preparing an in-situ gel electrolyte for an aqueous zinc-ion capacitor according to claim 1, characterized in that: In step (1), the graphene oxide sheet diameter is 50 nm to 5 μm, and the mass of the graphene oxide is 0.5 to 5% of the mass of the organic polymer monomer.

3. The method for preparing an in-situ gel electrolyte for an aqueous zinc-ion capacitor according to claim 1, characterized in that: In step (2), the zinc foil is square or round; the method of removing oxides is one or more of grinding and polishing or acid leaching; the acid leaching uses one or more of hydrochloric acid, sulfuric acid, acetic acid, and citric acid; the mass percentage concentration of the acid is 5% to 20%.

4. The method for preparing an in-situ gel electrolyte for an aqueous zinc-ion capacitor according to claim 1, characterized in that: In step (3), the ultraviolet wavelength of the ultraviolet irradiation method is 300~400 nm, the power of the ultraviolet light source is 5~120 W, and the irradiation polymerization time is 0.5~2 h.

5. The in-situ gel electrolyte for aqueous zinc ion capacitors is prepared by the preparation method according to any one of claims 1 to 4.

6. A zinc-ion capacitor, characterized in that: The zinc-ion capacitor comprises the in-situ gel electrolyte as described in claim 5.

7. A method for manufacturing a zinc-ion capacitor as described in claim 6, characterized in that: The preparation method includes the following steps: (a) The precursor dispersion was coated on the negative electrode and the positive electrode respectively, and then irradiated with ultraviolet light until it reached a semi-formed state. Specifically, the fluidity of the precursor dispersion decreased and the precursor dispersion did not drip when the electrode was inverted. (b) The zinc negative electrode is reversed and placed on the positive electrode, and ultraviolet irradiation is continued on the side until it is fully formed, thus obtaining a sandwich structure; (c) Package and test the resulting sandwich structure.

8. The method for manufacturing a zinc-ion capacitor according to claim 7, characterized in that: The positive electrode sheet is coated or formed onto a conductive substrate by coating, rolling, or spraying. The electrode paste consists of electrode material, conductive additives, and binder. The electrode material is one or more of activated carbon material or vanadium pentoxide and manganese dioxide metal oxide. The conductive additive is one or more of Super P and acetylene black. The binder is one or more of PVDF, PVA, and PVP polymer binders. The conductive substrate is made of aluminum foil, copper foil, stainless steel foil, carbon paper, or carbon cloth.

9. The method for manufacturing a zinc-ion capacitor according to claim 7, characterized in that: The packaging method uses a button cell battery case or a soft-pack battery case.

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