Preparation method and application of in-situ gel electrolyte membrane

Abstract

The invention relates to a preparation method of an in-situ growth neutral gel electrolyte membrane regulated and controlled by ethanolamine and application of the neutral gel electrolyte membrane in negative electrode protection of an aqueous zinc ion battery. The gel is promoted to form a film on the surface of a zinc plate by utilizing the crosslinking effect of ethanolamine, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid and the strong bonding effect of ethanolamine and the zinc plate. The membrane can improve the problems of low ion transfer rate, high free water molecule content and high activity of the traditional gel electrolyte, effectively inhibit the generation of hydrogen evolution reaction, and improve the ion transfer number, thereby improving the stability of the negative electrode and the intestinal circulation performance of the battery. The method is simple and safe to operate and shows excellent electrochemical performance, and the invention provides the method for protecting the negative electrode of the aqueous zinc ion battery.

Description

[Technical Field]

[0001] This invention belongs to the field of negative electrode protection for aqueous zinc-ion batteries, specifically relating to a method for preparing an in-situ gel electrolyte membrane and its application in aqueous zinc-ion batteries. [Background Technology]

[0002] With rapid societal development, traditional energy sources play a decisive role. However, due to their non-renewable nature, new energy storage devices have become crucial for sustainable social development. Among these, aqueous zinc-ion batteries are considered the most promising rechargeable batteries due to their high theoretical specific capacity (820mAh / g), low redox potential (-0.76V vs. SHE (standard hydrogen electrode)), safety, and low cost.

[0003] However, traditional commercial zinc anodes suffer from poor stability, a major drawback hindering their commercial application. Developing multifunctional gel electrolytes to stabilize the electrode / electrolyte interface and thus improve performance is a common strategy for enhancing zinc-ion battery performance. To alleviate the dilemma of the incompatibility between ionic conductivity and mechanical properties in traditional gel electrolytes, researchers have focused on constructing double-crosslinked network structures to improve mechanical properties, building ion channels to increase ionic conductivity, and introducing polar functional groups to regulate desolvation structures. Nevertheless, traditional gel electrolytes are relatively thick and do not have a tight enough contact with the zinc plate, significantly reducing their ionic conductivity. Furthermore, the presence of a large number of free water molecules in the gel electrolyte can lead to hydrogen evolution and corrosion reactions, which are detrimental to the long-term cycle stability of zinc-ion batteries.

[0004] Therefore, constructing an in-situ gel electrolyte membrane on the zinc plate surface can reduce the interference of side reactions and increase the adhesion between the electrolyte and the zinc plate, which is a feasible strategy to improve the long-term cycle stability of zinc-ion batteries. [Summary of the Invention]

[0005] To address the problems of traditional commercial zinc anodes, one objective of this invention is to provide a gel electrolyte membrane grown in situ on a zinc plate. This membrane is characterized by being formed by copolymerization and crosslinking of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and an ethanolamine additive. The ethanolamine additive is one or a mixture of ethanolamine, diethanolamine, and triethanolamine. This electrolyte membrane is tightly bonded to the zinc plate, has a small thickness, and possesses specific zinc ion channels, enabling rapid movement and uniform deposition of zinc ions on the electrode / electrolyte surface.

[0006] The second objective of this invention is to provide a method for preparing an in-situ hydrogel electrolyte membrane, the specific steps of which are as follows:

[0007] 1) First, polish the surface of the commercial zinc foil to remove the dense passivated zinc oxide on the surface. Then, ultrasonically clean the polished zinc foil with ethanol, deionized water, and ethanol for 10 minutes each, and then dry it.

[0008] 2) Dissolve appropriate amounts of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), N,N'-methylenebisacrylamide and ammonium persulfate in 2M ZnSO4 solution and stir to obtain a homogeneous solution;

[0009] 3) Add an appropriate amount of ethanolamine additive to the above solution to adjust the pH to 7 to obtain the precursor solution;

[0010] 4) Add the solution obtained above dropwise onto the polished zinc sheet, at 60°C. ο After standing in an oven at C for 5 hours, a gel electrolyte membrane grown in situ on the surface of a zinc plate is obtained.

[0011] The third objective of this invention is that the described gel electrolyte membrane can be used as an electrolyte and separator in aqueous zinc-ion batteries. A complete battery is assembled in sequence from a CR2032 negative electrode shell, a zinc negative electrode with a 14mm diameter grown gel electrolyte, a prepared positive electrode with a 12mm diameter, a gasket, a spring, and the CR2032 positive electrode shell.

[0012] Compared with traditional electrolyte materials, the present invention has the following main advantages and beneficial effects:

[0013] 1. The in-situ synthesis method used in this invention is safe and simple to operate, requires less precursor solution per electrode, is low in cost, and is easy to prepare in large quantities.

[0014] 2. The gel electrolyte membrane synthesized in this invention is closely connected to the zinc negative electrode, avoiding the problem of low ionic conductivity caused by poor contact between the traditional gel electrolyte and the electrode. At the same time, the electrolyte membrane can also replace the separator to prevent direct contact between the positive and negative electrodes.

[0015] 3. Compared with traditional gel electrolytes, gel electrolyte membranes have lower water content and a pH value closer to neutral, which can effectively inhibit water-related side reactions such as hydrogen evolution reaction and corrosion reaction.

[0016] 4. The novel negative electrode with a gel electrolyte membrane prepared by this invention can achieve performance far exceeding that of traditional commercial zinc negative electrodes in stability tests, and exhibits excellent reversibility, and can stabilize the output of the battery in practical applications of full cells.

[0017] Therefore, the gel electrolyte membrane synthesized using the method of the present invention has excellent electrochemical performance, high stability, and good reversibility, providing a new method for synthesizing gel electrolytes in aqueous zinc-ion batteries. [Attached Image Description]

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 This is a cross-sectional electron microscope image of the in-situ grown electrolyte membrane prepared in Example 1.

[0020] Figure 2 These are photographs of Comparative Example 1 and Example 1 grown in situ on zinc plates.

[0021] Figure 3 This is a comparison of the zinc ion transfer numbers of the gel electrolytes and gel electrolyte membranes synthesized in Comparative Example 2 and Example 1.

[0022] Figure 4 This is a comparison of the Tafel curves of Example 1 and Comparative Example 2.

[0023] Figure 5 Example 1 at 1mA cm -2 and 1mAh cm -2 The constant current charge-discharge cycle diagram under the given conditions.

[0024] Figure 6 It is the ion transfer number of the gel electrolytes synthesized in Comparative Examples 2 and 3.

[0025] Figure 7 These are the gel electrolyte membranes prepared in Comparative Examples 4 and 5.

[0026] Figure 8 It is the gel electrolyte membrane prepared in Examples 2 and 3.

Detailed Implementation Methods

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028]

Example 1

[0029] The preparation method of the in-situ grown gel electrolyte membrane described in Example 1 includes the following steps:

[0030] 1. First, polish the surface of the commercial zinc foil to remove the dense passivated zinc oxide. Then, ultrasonically clean the polished zinc foil with ethanol, deionized water, and ethanol for 10 minutes each, and then dry it.

[0031] 2. Dissolve appropriate amounts of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), N,N'-methylenebisacrylamide and ammonium persulfate in 2M ZnSO4 solution and stir to obtain a homogeneous solution;

[0032] 3. Add an appropriate amount of triethanolamine (TEA) to the above solution to adjust the pH to 7 to obtain the precursor solution;

[0033] 4. Add the solution obtained above dropwise onto the polished zinc sheet, at 60°C. ο After standing in an oven at C for 5 hours, a gel electrolyte membrane grown in situ on the surface of a zinc plate is obtained.

[0034] The obtained zinc anode was used for the assembly of symmetrical cells and full cells, as follows:

[0035] Assembly of a symmetrical battery: The CR2032 negative electrode shell, the 14mm diameter negative electrode, the 14mm diameter negative electrode, the gasket, the spring, and the CR2032 positive electrode shell are assembled into a symmetrical battery in sequence.

[0036] Assembly of the full cell: The CR2032 negative electrode shell, the negative electrode with a diameter of 14mm, the prepared positive electrode with a diameter of 12mm, the gasket, the spring, and the CR2032 positive electrode shell are assembled into a full cell in sequence.

[0037] Figure 1 This is a cross-sectional electron microscope image of the in-situ grown electrolyte membrane prepared in Example 1. As can be seen from the image, the electrolyte membrane is tightly bonded to the zinc plate, and the thickness of the electrolyte membrane is approximately 50 μm, much smaller than the 1-2 mm thickness of ordinary gel electrolytes.

[0038]

Example 2

[0039] The synthesis steps of Example 2 are similar to those of Example 1, except that triethanolamine is replaced with ethanolamine to adjust the pH to 7, and the obtained precursor solution is dropped onto a zinc plate.

[0040]

Example 3

[0041] The synthesis steps of Example 3 are similar to those of Example 1, except that triethanolamine is replaced with diethanolamine to adjust the pH to 7, and the obtained precursor solution is dropped onto a zinc plate.

[0042] Figure 8These are the gel electrolyte membranes prepared in Examples 2 and 3. It was found that all the alkanolamine analogs could form films on the zinc plate, with similar film-forming effects and electrochemical properties to triethanolamine. This indicates that these three alkanolamine analogs not only meet the requirements for pH control but also have a strong bonding ability with the zinc plate. Furthermore, they can crosslink with AM and AMPS to form hydrogen bonds, thus forming a tightly connected electrolyte membrane on the zinc plate surface.

[0043] Comparative Example 1

[0044] The synthesis steps of Comparative Example 1 are similar to those of Example 1, except that triethanolamine is not added; that is, the precursor solution obtained in step 2 is directly dropped onto a zinc plate.

[0045] Figure 2 These are photographs of the in-situ growth of Comparative Example 1 and Example 1 on a zinc plate. As can be seen from the figures, compared to the noticeably smooth film of Example 1, the surface of Comparative Example 1 is relatively rough, with obvious cracks, and poor contact with the electrode surface. This is mainly because triethanolamine has many hydroxyl groups, which can crosslink with AM and AMPS to form a film. Furthermore, it has a large adsorption capacity for the zinc plate, thus enabling film formation on the zinc plate surface. In contrast, the AM and AMPS solutions in Comparative Example 1 have lower concentrations on the zinc plate surface, resulting in lower crosslinking degrees, making film formation difficult, and their adsorption capacity for the zinc plate is weak, preventing growth on the zinc plate surface.

[0046] Comparative Example 2

[0047] The synthesis steps of Comparative Example 2 are similar to those of Example 1, except that instead of in-situ growth on a zinc plate, the precursor solution obtained in step 3 is directly placed into a polytetrafluoroethylene mold and heated to 60°C. ο After standing in an oven at temperature C for 5 hours, gel electrolyte is obtained.

[0048] Figure 3 This comparison shows the zinc ion transfer number of the gel electrolyte and gel electrolyte membrane synthesized in Comparative Example 2 and Example 1. It can be seen that the ion transfer number of the gel electrolyte membrane (0.85) is higher than that of the gel electrolyte (0.8). This is mainly due to the thinner electrolyte membrane and the covalent bond between the electrolyte membrane and the zinc plate, ensuring close contact and facilitating ion transport.

[0049] Figure 4 This is a comparison of the Tafel curves for Example 1 and Comparative Example 2. As can be seen from the graph, the gel electrolyte membrane has a higher corrosion voltage (-0.77V vs. -0.98V) compared to the gel electrolyte, indicating that the gel electrolyte membrane can effectively inhibit the hydrogen evolution reaction. This is mainly due to the lower free water content and lower water activity of the gel electrolyte membrane. Simultaneously, triethanolamine readily accepts H+. + The formation of a protonated structure can effectively suppress hydrogen evolution and corrosion reactions.

[0050] Comparative Example 3

[0051] The synthesis steps of Comparative Example 3 were similar to those of Comparative Example 2, except that triethanolamine was not added; instead, the precursor solution obtained in step 2 was directly placed into a polytetrafluoroethylene mold and heated to 60°C. ο After standing in an oven at temperature C for 5 hours, gel electrolyte is obtained.

[0052] Figure 5 Example 1 at 1mA cm -2 and 1mAh cm -2 The constant current charge-discharge cycle diagram under the specified conditions is shown in the figure. As can be seen from the figure, the symmetrical battery assembled in Example 1 can stably cycle for more than 3500 hours under these conditions, indicating its good cycle stability.

[0053] Figure 6 The figure shows the ion transfer numbers of the gel electrolytes synthesized in Comparative Examples 2 and 3. As can be seen from the figure, the ion transfer number of the gel electrolyte in Comparative Example 3 is smaller (0.52) compared to Comparative Example 2. This is because triethanolamine has a stronger binding affinity for zinc ions, effectively increasing the zinc ion transfer number.

[0054] Comparative Example 4

[0055] The synthesis steps of Comparative Example 4 were similar to those of Example 1, except that triethanolamine was replaced with ammonia to adjust the pH to 7, and the obtained precursor solution was dropped onto a zinc plate.

[0056] Comparative Example 5

[0057] The synthesis steps of Comparative Example 5 were similar to those of Example 1, except that triethanolamine was replaced with potassium hydroxide to adjust the pH to 7, and the obtained precursor solution was dropped onto a zinc plate.

[0058] Figure 7 These are the gel electrolyte membranes prepared in Comparative Examples 4 and 5. It was found that replacing triethanolamine with a common alkaline solution resulted in significant powdering and crystallization of the film on the zinc plate, greatly reducing transparency and weakening the bond with the zinc plate, which significantly impacted its electrochemical performance. Therefore, simply adjusting the pH level reduced the film-forming effect.

[0059] In summary, the addition of triethanolamine and other alkanolamine analogs not only forms an electrolyte film that grows in situ on the zinc plate surface, effectively improving zinc ion transfer efficiency, but also, compared to traditional gel electrolytes, the gel electrolyte film has lower free water activity, inhibiting hydrogen evolution and corrosion reactions, thus protecting the zinc anode.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A gel electrolyte membrane grown in situ on a zinc plate, characterized in that, It is formed by copolymerization and crosslinking of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and ethanolamine additive, wherein the ethanolamine additive is one or a mixture of ethanolamine, diethanolamine, and triethanolamine. The preparation method is as follows: 1) Grind the surface of commercial zinc foil to remove the passivation layer, then sonicate it for 10 minutes each with ethanol, deionized water, and ethanol, and then dry it. 2) Dissolve appropriate amounts of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), N,N'-methylenebisacrylamide and ammonium persulfate in 2M ZnSO4 solution and stir to obtain a homogeneous solution; 3) Add ethanolamine additive to the solution obtained in step (2) and adjust the pH to 7 to obtain the precursor solution; 4) Add the solution obtained in step (3) dropwise onto the polished zinc sheet, at 60°C. ο After standing in an oven at C for 5 hours, a gel electrolyte membrane grown in situ on the surface of a zinc plate is obtained.

2. The application of the gel electrolyte membrane grown in situ on a zinc plate as described in claim 1, characterized in that, It can be used as an electrolyte and separator in zinc-ion batteries to protect the zinc negative electrode.

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