A method for rapid preparation of gel electrolytes via controlled polymerization mechanism

Abstract

This invention belongs to the field of energy storage material preparation, and particularly relates to a method for rapidly preparing hydrogel electrolytes through a controllable polymerization mechanism. The specific steps are as follows: Nanomaterials are dispersed in an electrolyte salt solution to obtain a dispersion; unsaturated monomers containing double bonds are dissolved in the dispersion; then an initiator and a crosslinking agent are added. At room temperature, a hydrogel electrolyte with controllable gelation time is prepared in one step. This invention can further adjust the gelation time by changing the concentration of the electrolyte salt solution, the monomer content, and the system temperature to adapt to different processing and assembly requirements. The controllable accelerated polymerization mechanism proposed in this invention is applicable to the preparation process of hydrogel electrolytes synthesized from unsaturated organic small molecules with double bonds, and effectively solves the problem of poor dispersibility in the nanomaterial composite process. This method has low energy consumption, short processing time, and strong controllability. The prepared hydrogel electrolyte has a quantitative electrolyte content, a uniform and stable structure, and excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of energy storage material preparation, and particularly relates to a method for rapidly preparing gel electrolytes through a controllable polymerization mechanism. Background Technology

[0002] The government is vigorously promoting the diversified applications of electrochemical energy storage and the development of new energy storage technologies. Lithium-ion batteries, with their high energy density and cycle stability, have dominated the electrochemical energy storage field since their commercialization in the last century. However, lithium-ion batteries suffer from high cost and significant environmental hazards, further limiting their application. Compared to organic lithium-ion batteries, aqueous batteries have broad application prospects due to their low cost, high safety, and high ionic conductivity. Among them, aqueous zinc-ion batteries have a low redox potential (-0.76V vs. SHE) and a high theoretical specific capacity (820mAh g / g). -1 With its advantages such as environmental friendliness and ease of assembly, it has become one of the most competitive alternatives to lithium-ion batteries. Meanwhile, flexible and wearable electronics have become a booming market, and ideal flexible devices require components with high mechanical flexibility and good mechanical properties. However, traditional aqueous separators exhibit only limited flexibility; they are not flexible enough to adapt to various deformations during actual movement. Furthermore, these separators have poor mechanical properties and cannot withstand severe external impacts, meaning they are easily affected or even fail.

[0003] Compared to aqueous separators, hydrogel electrolytes are increasingly showing promising application potential as electrolyte materials and separators in aqueous zinc-ion batteries. Hydrogels are composed of cross-linked polymer chains and water filling them, typically exhibiting a soft, moist state. The charged functional groups on the polymer chains can effectively attract electrolyte ions, while water molecules impart liquid-like ionic conductivity. More importantly, they possess solid-like stability, preventing electrolyte leakage under stress. Simultaneously, hydrogel electrolytes exhibit excellent stretchability, processability, and self-healing properties, thus resisting bending, deformation, and unpredictable external mechanical stress. However, the preparation of traditional hydrogels requires external energy (light, heat, etc.) to induce the formation of free radicals in the initiator, which then initiates the polymerization of unsaturated monomers. This process is time-consuming, increasing the preparation cost of hydrogel electrolytes. Furthermore, the mechanical properties of gel electrolytes affect battery cycle stability. The unique organic / inorganic network structure formed by nanocomposite gels endows them with excellent mechanical properties; however, some nanomaterials suffer from poor dispersibility, leading to aggregation and sedimentation during prolonged gelation, resulting in an uneven gel structure and affecting overall performance. Simultaneously, the method of introducing electrolyte salts into the gel via immersion inevitably leads to irreversible deformation of the gel structure, and the introduced electrolyte salts cannot be quantified. All of these factors significantly limit the further application of gel electrolytes in aqueous zinc-ion batteries.

[0004] Therefore, it is of great significance to prepare gel electrolytes with excellent mechanical properties, uniform and stable structure, and controllable gelation time using a relatively simple and feasible method. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a method for rapidly preparing hydrogel electrolytes through a controllable polymerization mechanism. The specific steps are as follows: Nanomaterials are dispersed in an electrolyte salt solution to obtain a dispersion; unsaturated monomers containing double bonds are dissolved in the dispersion; then an initiator and a crosslinking agent are added. At room temperature, a hydrogel electrolyte with controllable gelation time is prepared in one step. This invention allows for further adjustment of the gelation time by changing the concentration of the electrolyte salt solution, the monomer content, and the system temperature to adapt to different processing and assembly requirements. The controllable accelerated polymerization mechanism proposed in this invention is applicable to the preparation of hydrogel electrolytes from unsaturated organic small molecules with double bonds, and effectively solves the problem of poor dispersibility during nanomaterial composite processes. This method is energy-efficient, time-saving, and highly controllable. The prepared hydrogel electrolyte has a quantitative electrolyte content, a uniform and stable structure, and excellent mechanical properties.

[0006] The technical concept of this invention is as follows:

[0007] By inhibiting the decay of free radicals through electrolyte salts, the controlled and rapid polymerization of unsaturated monomers is promoted. Furthermore, the gelation time can be significantly adjusted by changing the monomer content, electrolyte salt concentration, and system temperature to adapt to different processing and assembly requirements. The resulting gel electrolyte has a gelation time of only 5-600 seconds at room temperature, exhibiting a stable and uniform three-dimensional structure, typically a network structure. Nanomaterials can be further introduced to endow the hydrogel with more functional properties, enabling stable operation of aqueous batteries while effectively reducing energy and time consumption, lowering production costs, and promoting innovative development in energy storage technology.

[0008] The more specific technical solution of this invention is as follows:

[0009] A method for rapidly preparing gel electrolytes via a controlled polymerization mechanism, comprising the following steps:

[0010] (1) Disperse the nanomaterials in an electrolyte salt solution, stir and sonicate to obtain dispersion A;

[0011] The mass fraction of nanomaterials in dispersion A mentioned in step (1) is 5-40 mg / mL. -1 The preferred nanomaterial mass fraction is 25 mg / mL. -1 The mechanical properties are optimal at this time.

[0012] In step (1), the concentration of the electrolyte salt is 1-5 mol / L. -1 Furthermore, the higher the electrolyte salt concentration, the shorter the gelation time;

[0013] In step (1), the electrolyte salt refers to one or a mixture of two of zinc sulfate (ZnSO4) or zinc trifluoromethanesulfonate (Zn(CF3SO3)2);

[0014] (2) Dissolve the unsaturated monomer containing double bonds in the dispersion A prepared in step 1) to obtain solution B;

[0015] The unsaturated monomers mentioned above are organic monomers containing unsaturated bonds, specifically selected from monomers such as amides, carboxyl groups, and hydroxyl groups; the unsaturated monomers account for 3wt%-25wt% of the total mass of solution B;

[0016] More preferably, it is a mixture of one or more monomers selected from acrylamide, N-2-(hydroxyethyl)-acrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, sodium 2-acrylamido-2-methylpropanesulfonate, sodium acrylate, sodium p-vinylbenzenesulfonate, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide;

[0017] (3) Add the crosslinking agent and initiator to the dispersion B prepared in step 2) in sequence, vortex for a few seconds under environmental conditions, and let stand for 5-600 seconds to obtain the gel electrolyte.

[0018] The crosslinking agent is a compound containing two or more unsaturated double bonds within its molecule; specifically, it can be selected from N,N-methylenebisacrylamide or divinylbenzene.

[0019] The initiator is an inorganic peroxide initiator; specifically, it can be selected from one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0020] In step (3), the amount of initiator is 0.1wt%-0.6wt% of the total monomer mass, and the amount of crosslinking agent is 0.01wt%-0.2wt% of the total monomer mass. Too much will result in insufficient rigidity and flexibility of the gel, leading to a fragile gel, while too little will result in insufficient mechanical properties.

[0021] In further step (1) above, the nanomaterials are zero-dimensional, one-dimensional, or two-dimensional nanomaterials, such as nanoparticles like nano-silica, nanowires like nano-cellulose, and nanosheets like montmorillonite, which are organic or inorganic nanomaterials with a large specific surface area and can exist stably in water; and the size of the zero-dimensional material is between 1 and 100 nm; the diameter of the one-dimensional material is 1-100 nm and the length is greater than 1 μm; the average wafer thickness of the two-dimensional layered material is less than 25 nm.

[0022] The ultrasonic time in step (1) is 0.1-5h, the ultrasonic power is 100-300w, and the ultrasonic frequency is 20-100KHz to ensure the uniformity of the gel structure.

[0023] In the above process, the acidic environment created by the hydrolysis of high-concentration zinc sulfate promotes the growth of S2O8. 2- Decomposes into SO4 ·- (S2O8 2- →2SO4 ·- However, SO4 ·- It will inevitably react with water, thus reducing SO4 levels. ·- The concentration of ZnSO4. Here, combining EPR testing and DFT calculations, it is further demonstrated that high concentrations of ZnSO4 inhibit the decay reaction of free radicals, thereby promoting a high free radical concentration in the system and initiating the polymerization of unsaturated monomers into polymer chains (such as...). Figure 1 (as shown in ac). In addition, CF3SO3 - and SO4 2-Having similar structures, they share the same mechanism of action. High concentrations of Zn(CF3SO3)2 can still initiate the decomposition of inorganic peroxides at room temperature and maintain a high free radical concentration, promoting rapid monomer polymerization to form a gel. Therefore, the higher the electrolyte salt concentration, the stronger the inhibitory effect on free radical decay. Thus, the gelation time of the system can be further altered by appropriately adjusting the concentration of the electrolyte salt to change the concentration of SO42-.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The controllable polymerization mechanism proposed in this invention simplifies the gelation conditions from heating at high temperature of 50-90℃ for tens of minutes to 5-600s at room temperature. Furthermore, the gelation time can be adjusted by regulating the concentration of electrolyte salt, monomer content, and system temperature. This preparation method has the advantages of saving resources, reducing costs, and being environmentally friendly and economical.

[0026] (2) Compared to traditional thermally initiated hydrogel preparation methods, which involve a slow solution-sol-gel transition, inorganic or organic nanomaterials may exhibit uneven dispersion and agglomeration due to gravity. The gel electrolyte prepared in this invention, with its short gelation time, effectively alleviates the problems of nanomaterial agglomeration and sedimentation caused by prolonged thermal polymerization in gel preparation (e.g., ...). Figure 2 (As shown). Furthermore, the prepared composite gel electrolyte exhibits good mechanical properties, effectively improving electrolyte stability and battery cycle performance. In addition, the introduction of nanomaterials further endows the gel electrolyte with self-healing, flexibility, elasticity, rigidity, antifreeze properties, chemical and structural stability, enhancing the battery's potential for multi-scenario applications. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the mechanism of gel preparation via controlled polymerization.

[0028] As shown in the figure, in H + (Source: Zn) 2+ Under the action of hydrolysis, S2O8 2- It can decompose into SO4 ·- Subsequently, the high concentration of ZnSO4 maintained a high SO4 content by inhibiting the decay of free radicals. ·- Concentration promotes gelation of the system;

[0029] Figure 2 The images show gel electrolytes prepared by controlled accelerated polymerization (left) and conventional addition polymerization. The images are inverted. As can be seen from the images, the gel prepared by conventional addition polymerization exhibits problems such as agglomeration and sedimentation, while the gel prepared by controlled accelerated polymerization has a uniform structure.

[0030] Figure 3 Photographs and SEM images of the composite hydrogel electrolyte prepared in Example 1.

[0031] in, Figure 3 Photo a is a composite gel electrolyte. Figure 3 b is the SEM image of the composite gel electrolyte;

[0032] Figure 4 A comparative graph showing the mechanical properties of the composite hydrogel electrolyte prepared in Example 1.

[0033] The introduction of inorganic nanomaterial montmorillonite in the figure significantly improves the mechanical properties of the hydrogel electrolyte;

[0034] Figure 5 The self-healing properties of the composite hydrogel electrolyte prepared in Example 1 of this invention

[0035] The light color in the picture is the original color of the composite gel electrolyte, while the dark color is the color after Prussian blue staining. After being divided, the gel electrolyte can heal and bear its own weight.

[0036] Figure 6 The DSC test curves of the composite hydrogel prepared in Example 1 of the present invention, the gel prepared without the addition of nanomaterials, and the electrolyte are shown.

[0037] Figure 7 This is a comparison of the electrochemical performance of the hydrogel electrolyte prepared in Example 5 of the present invention. Detailed Implementation

[0038] The invention will be further illustrated below with specific implementation examples. These examples are only intended to provide a complete and clear explanation of the invention, and are not intended to represent all possible implementations. All other implementations created based on this invention are within the scope of protection of this invention.

[0039] Example 1

[0040] Prepare a 3mol L solution using a volumetric flask. -1 Accurately weigh 0.25 g of sodium-based montmorillonite (MMT, 99% purity) and add it to 10 mL of 3 mol / L electrolyte solution. -1 In the ZnSO4 electrolyte salt, MMT and ZnSO4 were stirred at room temperature for 2 hours to ensure uniform mixing. Subsequently, the MMT-ZnSO4 dispersion was sonicated at 200 W power and 40 kHz frequency for 60 minutes to exfoliate and further disperse MMT.

[0041] Take 2 mL of the ultrasonically dispersed solution into a centrifuge tube and add 0.3 g of acrylamide and stir for 3 h. Then add 10 μL of 2 wt% N,N-methyleneacrylamide solution, vortex for a few seconds, add 20 μL of 3 wt% potassium persulfate, vortex for a few seconds, transfer a portion of the solution into a custom mold and let it stand at room temperature for 60 s to obtain the gel electrolyte.

[0042] The introduction of sodium-based montmorillonite with a two-dimensional layered structure enables acrylamide to polymerize in situ within the layered structure of MMT, and further stabilizes the gel structure through hydrogen bonding, thereby forming a three-dimensional network with a certain spatial structure. Figure 3 ab). The mechanical strength of the gel with added MMT was significantly improved compared to the gel without MMT, such as Figure 4 As shown, its mechanical strength reached 0.25 MPa. To further test the self-healing performance of the gel electrolyte, we divided the prepared gel electrolyte into several small segments under external force and simply bonded them together. It was found that a stable self-supporting hydrogel could be formed after a few minutes, indicating that the prepared gel has a certain degree of self-healing property. Figure 5 The introduction of MMT can effectively break the hydrogen bond network between water molecules, thereby improving the antifreeze properties of the gel electrolyte and enhancing the battery's potential for various applications. Figure 6 ).

[0043] Example 2

[0044] Prepare a 2.5 mol L solution using a volumetric flask. -1 Zn(CF3SO3)2 electrolyte salt. Accurately weigh 0.20 g of halloysite (HNTs) and add it to 10 mL of 2.5 mol / L solution. -1 In the Zn(CF3SO3)2 electrolyte salt, HNTs and Zn(CF3SO3)2 were stirred at room temperature for 2 hours to ensure uniform mixing. Subsequently, the HNTs-Zn(CF3SO3)2 dispersion was sonicated at 150W power and 28KHz frequency for 30 minutes to exfoliate and further disperse the HNTs.

[0045] Take 2 mL of the ultrasonically dispersed solution into a centrifuge tube and add 0.4 g of N-2-(hydroxyethyl)-acrylamide. Stir for 3 h, then add 15 μL of 2 wt% N,N-methyleneacrylamide solution. Vortex for a few seconds, then add 25 μL of 3 wt% ammonium persulfate. Vortex for a few seconds, then transfer a portion of the solution into a custom mold and let it stand at room temperature for 40 s to obtain the gel electrolyte.

[0046] Example 3

[0047] Prepare a 3mol L solution using a volumetric flask. -1ZnSO4 electrolyte salt. Accurately weigh 0.10 g of cellulose and add it to 10 mL of 3 mol / L solution. -1 In the ZnSO4 electrolyte salt, HNTs and ZnSO4 were stirred at room temperature for 4 hours to ensure uniform mixing. Subsequently, the HNTs-ZnSO4 dispersion was sonicated at 300W power and 40KHz for 180 minutes to further disperse the cellulose.

[0048] Take 2 mL of the ultrasonically dispersed solution into a centrifuge tube and add 0.3 g of sodium acrylate and 0.05 g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide. Stir for 3 h. Then add 15 μL of 2 wt% N,N-methyleneacrylamide solution and vortex for a few seconds. Add 25 μL of 3 wt% ammonium persulfate and vortex for a few seconds. Transfer a portion of the solution into a custom mold and let it stand at room temperature for 150 s to obtain the gel electrolyte.

[0049] Example 4

[0050] Prepare 2, 2.5, and 3 mol L solutions using volumetric flasks. -1 ZnSO4 electrolyte salt. Accurately weigh 0.15 g of hydrotalcite-like substances (LDHs) and add them to 10 mL of 3 mol / L solution. -1 In the ZnSO4 electrolyte salt, the mixture was stirred at room temperature for 2 hours to ensure homogeneity of the hydrotalcite-ZnSO4 mixture. Subsequently, the LDHs-ZnSO4 dispersion was sonicated at 200 W power and 25 kHz to exfoliate and further disperse the LDHs.

[0051] Take 2 mL of the ultrasonically dispersed solutions of different concentrations into centrifuge tubes and add 0.3 g of acrylamide, stirring for 3 h. Then, add 10 μL of 2 wt% N,N-methyleneacrylamide solution sequentially, vortex for a few seconds, add 25 μL of 3 wt% sodium persulfate, vortex for a few seconds, and transfer a portion of the solution into a custom mold. Allow it to stand at room temperature for different times to obtain gel electrolytes (LDHs-PAM). The gelation times of ZnSO4 electrolyte salts of different concentrations in this example are shown in Table 1.

[0052] Table 1 Effect of electrolyte salt concentration on gelation time

[0053]

[0054] As shown in Table 1, the gelation time gradually decreases with the increase of electrolyte salt concentration.

[0055] Experimental Example

[0056] The electrochemical performance of an aqueous zinc-manganese battery was tested using the MMT-PAM gel electrolyte prepared in Example 1. A gel electrolyte without the inorganic nanomaterial MMT was prepared using the same method as a control group (PAM). The ionic conductivity and electrochemical performance are shown in the figures. The introduction of the two-dimensional layered MMT significantly improved zinc ion transport and increased its ionic conductivity (Figures 7a-b). During battery use, battery life is an important parameter for evaluating battery performance, but using 5-10 A g... -1 Even at higher current densities, a battery cycle life of ≥1000 cycles indicates a high cycle life, but this is not very significant in practical grid energy storage. Therefore, we chose 0.2A g. -1 Long-term cycle testing of the battery was conducted using a specific current density. The initial discharge specific capacity of the prepared MnO2 / MMT-PAM / Zn battery was 0.2 A g. -1 It reached 294mAh g -1 And it can stably cycle 2000 times. Figure 7 c). However, MnO2 / PAM / Zn batteries fail after only a few hundred cycles. The extremely high cycle life and stable discharge specific capacity indicate that the addition of MMT improves the battery's electrochemical stability.

[0057] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The description of the above embodiments can help understand the principles and methods of the present invention. However, the above embodiments are not unique and should not be construed as limiting the present invention. At the same time, those skilled in the art can make flexible changes to the specific implementation methods and application scope based on the principles and methods of the present invention.

Claims

1. A method for rapidly preparing gel electrolytes via a controlled polymerization mechanism, characterized in that, The specific steps are as follows: (1) Disperse the nanomaterials in an electrolyte salt solution, stir and sonicate to obtain dispersion A; The mass fraction of nanomaterials in dispersion A mentioned in step (1) is 5-40 mg / mL. -1 The concentration of the electrolyte salt is 2-5 mol / L. -1 Electrolyte salts refer to one or a mixture of two of zinc sulfate or zinc trifluoromethanesulfonate. (2) Dissolve the unsaturated monomer containing double bonds in the dispersion A prepared in step 1) to obtain solution B; wherein the unsaturated monomer is an organic monomer containing unsaturated bonds, specifically selected from amide, carboxyl, and hydroxyl monomers; (3) Add the crosslinking agent and initiator to the dispersion B prepared in step 2) in sequence, vortex for a few seconds under ambient conditions, and let stand for 5-600 s to obtain the gel electrolyte; In step (3), the amount of initiator is 0.1wt%-0.6wt% of the total monomer mass, and the amount of crosslinking agent is 0.01wt%-0.2wt% of the total monomer mass; the initiator is selected from one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

2. The method for preparing gel electrolytes according to claim 1, characterized in that, In step (1), the mass fraction of the nanomaterial is 25 mg / mL. -1 The unsaturated monomers are organic monomers containing unsaturated bonds, specifically selected from amide, carboxyl, and hydroxyl monomers; the unsaturated monomers account for 3 wt%-25 wt% of the total mass of solution B.

3. The method for preparing gel electrolytes according to claim 1, characterized in that, The unsaturated monomer is a mixture of one or more monomers selected from acrylamide, N-2-(hydroxyethyl)-acrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, sodium 2-acrylamido-2-methylpropanesulfonate, sodium acrylate, sodium p-vinylbenzenesulfonate, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide.

4. The method for preparing gel electrolytes according to claim 1, characterized in that, The crosslinking agent is a compound containing two or more unsaturated double bonds within its molecule.

5. The method for preparing gel electrolytes according to claim 4, characterized in that, The crosslinking agent is selected from N,N-methylenebisacrylamide or divinylbenzene.

6. The method for preparing gel electrolytes according to claim 1, characterized in that, The nanomaterials in step (1) are zero-dimensional, one-dimensional, and two-dimensional nanomaterials; and the size of the zero-dimensional material is between 1 and 100 nm; the diameter of the one-dimensional material is 1-100 nm and the length is greater than 1 μm; the average wafer thickness of the two-dimensional layered material is less than 25 nm.

7. The method for preparing gel electrolytes according to claim 1, characterized in that, The ultrasound time in step (1) is 0.1-5 h, the ultrasound power is 100-300 w, and the ultrasound frequency is 20-100 kHz.

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