An aqueous polyurethane gel electrolyte, its preparation method and a zinc ion battery

Abstract

The present invention discloses an aqueous polyurethane gel electrolyte, a preparation method thereof, and a zinc ion battery, relating to the field of battery technology. The preparation method of the aqueous polyurethane gel electrolyte comprises the following steps: providing a first dispersion, the first dispersion being an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion; the anion-modified aqueous polyurethane dispersion being obtained by reacting the aqueous polyurethane dispersion with an anionic hydrophilic monomer having an amino group; and freeze-forming the first dispersion, and then immersing it in a zinc salt aqueous solution to induce the Hofmeister effect, thereby obtaining an aqueous polyurethane gel electrolyte. In the present invention, the aqueous polyurethane dispersion is freeze-formed, and then immersed in a zinc salt aqueous solution to form an aqueous polyurethane gel electrolyte. Simultaneously, the Hofmeister effect is utilized to induce the conversion of free water molecules within the aqueous polyurethane gel electrolyte into bound water, thereby preparing an aqueous polyurethane gel electrolyte having both a wide voltage window and high ionic conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an aqueous polyurethane gel electrolyte, a preparation method thereof, and a zinc ion battery. Background Art

[0002] Aqueous zinc-ion batteries (Zn-ion batteries) have developed rapidly due to their advantages, including high safety, large theoretical capacity, low redox potential, and abundant zinc resources. However, they face the challenge of low energy density because the stable electrochemical window of their aqueous electrolyte is only 1.23V. Exceeding this window triggers water decomposition reactions, reducing reversible capacity and leading to side reactions. This limits the development of Zn-ion batteries, especially high-voltage and high-energy-density Zn-ion batteries. Modulating the structure of aqueous electrolytes to improve their stability is a current research focus and is of great significance for the development of high-voltage Zn-ion batteries, such as flexible Zn-ion batteries.

[0003] Currently, the main strategies for broadening the electrochemical stability window of aqueous electrolytes include the water-in-salt strategy and the molecular crowding strategy. However, both strategies still face some challenges. The water-in-salt strategy can extend the electrochemical stability window, but it is highly corrosive, toxic, and expensive, making it unsuitable for large-scale application. The molecular crowding strategy, on the other hand, limits the activity of water molecules by adding organic matter to increase the operating voltage of the battery, but it faces challenges such as reduced conductivity, high cost, and environmental pollution.

[0004] Therefore, there is an urgent need to develop a low-cost, high-safety method to broaden the electrochemical window of aqueous electrolytes and inhibit the electrolyte water decomposition reaction to achieve the preparation of high-energy zinc-ion batteries. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide an aqueous polyurethane gel electrolyte, a preparation method thereof, and a zinc ion battery, aiming to solve the problem of the narrow electrochemical window of the existing zinc ion batteries using aqueous electrolytes.

[0006] The technical solutions of the present invention are as follows:

[0007] A first aspect of the present invention provides a method for preparing an aqueous polyurethane gel electrolyte, comprising the following steps:

[0008] Providing a first dispersion, wherein the first dispersion is an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion; the anion-modified aqueous polyurethane dispersion is obtained by reacting an aqueous polyurethane dispersion with an anionic hydrophilic monomer having an amino group;

[0009] The first dispersion is freeze-formed and then immersed in a zinc salt aqueous solution to induce a Hofmeister effect, thereby obtaining the aqueous polyurethane gel electrolyte.

[0010] Optionally, the preparation method of the aqueous polyurethane dispersion comprises the following steps:

[0011] Mixing a polyol, a diisocyanate, a catalyst, and an organic solvent, and reacting the mixture to obtain a first reaction liquid containing a polyurethane prepolymer;

[0012] adding a hydrophilic chain extender having a carboxyl group to the first reaction liquid, and reacting to obtain a second reaction liquid containing a polyurethane prepolymer having a carboxyl group;

[0013] adding a neutralizing agent to the second reaction liquid to obtain a polyurethane prepolymer having a hydrophilic group after reaction;

[0014] The polyurethane prepolymer with hydrophilic groups is dispersed in water to obtain the aqueous polyurethane dispersion.

[0015] Optionally, the preparation method of the anion-modified aqueous polyurethane dispersion comprises the following steps:

[0016] Mixing a polyol, a diisocyanate, a catalyst, and an organic solvent, and reacting the mixture to obtain a first reaction liquid containing a polyurethane prepolymer;

[0017] adding a hydrophilic chain extender having a carboxyl group to the first reaction liquid, and reacting to obtain a second reaction liquid containing a polyurethane prepolymer having a carboxyl group;

[0018] adding a neutralizing agent to the second reaction liquid to obtain a polyurethane prepolymer having a hydrophilic group after reaction;

[0019] dispersing the polyurethane prepolymer with hydrophilic groups into water to obtain the aqueous polyurethane dispersion;

[0020] The aqueous polyurethane dispersion is mixed with an anionic hydrophilic monomer having an amino group, and after reaction, the anionic modified aqueous polyurethane dispersion is obtained.

[0021] Optionally, the polyol includes at least one of polyethylene glycol, polycaprolactone diol, polyethylene glycol dimethacrylate and diethylene glycol;

[0022] The diisocyanate comprises at least one of isophorone diisocyanate, hexamethylene diisocyanate, lysine diisocyanate and diphenylmethane diisocyanate;

[0023] The catalyst comprises at least one of dibutyltin dilaurate, dimethyltin dihydroxyacetate, N,N-dimethylcyclohexylamine and triethyl phosphate;

[0024] The hydrophilic chain extender with a carboxyl group includes at least one of 2,2-dimethylol propionic acid and 2,2-dimethylol butyric acid;

[0025] The neutralizing agent includes at least one of triethanolamine and NaOH.

[0026] Optionally, the anionic hydrophilic monomer having an amino group includes at least one of carbamate, sulfamate and methyl carbamate.

[0027] Optionally, the zinc salt includes at least one of zinc sulfate, zinc perchlorate, zinc trifluoromethanesulfonate and zinc fluoroborate; and the concentration of the zinc salt in the zinc salt aqueous solution is 0.05-1.0 mol / L.

[0028] Optionally, the mass ratio of the polyol, the diisocyanate, the catalyst, the hydrophilic chain extender with a carboxyl group, and the neutralizer is 1: (1.4-1.85): 0.01: (0.4-0.8): (0.4-0.8);

[0029] In the aqueous polyurethane dispersion, the mass ratio of the polyurethane prepolymer with hydrophilic groups to water is (1-3):1.

[0030] Optionally, the mass ratio of the aqueous polyurethane dispersion to the anionic hydrophilic monomer with an amino group is (1-3):1.

[0031] In a second aspect of the present invention, an aqueous polyurethane gel electrolyte is provided, wherein the aqueous polyurethane gel electrolyte is prepared by the preparation method of the present invention as described above.

[0032] A third aspect of the present invention provides a zinc ion battery, wherein the zinc ion battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte located between the positive electrode sheet and the negative electrode sheet, and the electrolyte is the aqueous polyurethane gel electrolyte as described above in the embodiment of the present invention.

[0033] Beneficial Effects: The present invention freeze-forms an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion, then immerses it in a zinc salt aqueous solution to form an aqueous polyurethane gel electrolyte. Simultaneously, the Hofmeister effect is utilized to form strong hydrogen bonds between the hydrophilic groups of the aqueous polyurethane, zinc salt anions, and water molecules in the aqueous polyurethane gel electrolyte, inducing the conversion of free water molecules within the aqueous polyurethane gel electrolyte into bound water. This results in an aqueous polyurethane gel electrolyte with a wide voltage window and high ionic conductivity, enabling zinc-ion batteries to achieve a higher voltage platform and energy density. Furthermore, the preparation method provided by the present invention is low-cost and highly safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the preparation mechanism of aqueous polyurethane gel electrolyte in an embodiment of the present invention.

[0035] Figure 2 Schematic diagrams of zinc ion deposition on the surfaces of different electrolytes, where (a) is a traditional hydrogel electrolyte and (b) is an aqueous polyurethane gel electrolyte in an embodiment of the present invention.

[0036] Figure 3 This is a physical picture of the aqueous polyurethane gel electrolyte prepared in Example 1 of the present invention.

[0037] Figure 4 This is a linear sweep voltammetry curve of the aqueous polyurethane gel electrolyte prepared in Example 1 of the present invention.

[0038] Figure 5 This is a cyclic voltammetry curve of the flexible zinc ion battery prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The present invention provides an aqueous polyurethane gel electrolyte, a preparation method thereof, and a zinc ion battery. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] An embodiment of the present invention provides a method for preparing an aqueous polyurethane gel electrolyte, which comprises the following steps:

[0042] S1. Providing a first dispersion, wherein the first dispersion is an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion; the anion-modified aqueous polyurethane dispersion is obtained by reacting an aqueous polyurethane dispersion with an anionic hydrophilic monomer having an amino group;

[0043] S2. After freeze-forming the first dispersion, immersing the dispersion in a zinc salt aqueous solution to induce a Hofmeister effect, thereby obtaining the aqueous polyurethane gel electrolyte.

[0044] like Figure 1 As shown, in the embodiments of the present invention, an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion is freeze-formed and then immersed in a zinc salt aqueous solution to induce the Hofmeister effect. During the reaction, when the zinc salt anions in the zinc salt aqueous solution come into contact with the amphiphilic molecular chains with a protein-like structure in the aqueous polyurethane, the aggregation state of the aqueous polyurethane molecular chains is increased, and their solubility in water is reduced, thereby causing salting out and obtaining an aqueous polyurethane gel electrolyte. At the same time, strong hydrogen bonds form between the hydrophilic groups of the polyurethane molecular chains, the zinc salt anions, and the water molecules, forming isolated "hydrophilic cages" that can induce the aqueous polyurethane gel electrolyte (i.e., Figure 1 The free water molecules inside the gel matrix (in the electrolyte) are converted into bound water, thereby inhibiting the water decomposition reaction and widening the electrochemical stability window of the electrolyte. In addition, the aqueous polyurethane gel electrolyte obtained based on the Hofmeister effect contains a large amount of zinc salt anions, which can form ion channels, promote the transmission and uniform deposition of zinc ions, and thus have high ionic conductivity. The Hofmeister effect can cause the hydrophobic molecular groups of the amphiphilic polymer chain to migrate and aggregate to the external interface, thereby improving the surface adhesion of the aqueous polyurethane gel electrolyte, which is beneficial to improving the interfacial stability between the electrolyte and the electrode of the zinc ion battery. Therefore, the preparation method provided by the present invention can be used to prepare an aqueous polyurethane gel electrolyte with a wide voltage window (i.e., electrochemical stability window), high ionic conductivity and high stability, thereby enabling the zinc ion battery to obtain a higher voltage platform and energy density. The preparation method provided by the present invention is low in cost and high in safety.

[0045] In addition, because the Hofmeister effect is formed by the formation of strong hydrogen bonds between zinc salt anions, water molecules and hydrophilic groups of polyurethane molecular chains, Figure 2 As shown in (b), the introduction of anionic functional groups on the polymer molecular chain (i.e., the use of anionic modified waterborne polyurethane) can optimize the hydrophilicity of the waterborne polyurethane gel electrolyte and regulate the local concentration of bound water. More importantly, Figure 2As shown in (a), the conventional hydrogel electrolyte has low ionic conductivity and is prone to zinc dendrite problems. However, in the present invention, Figure 2 As shown in (b), the anions introduced into the anion-modified waterborne polyurethane can complex with zinc ions to form ion channels, promote zinc ion transport through electrostatic forces, and induce uniform deposition of zinc ions.

[0046] In step S1, in some embodiments, the method for preparing the aqueous polyurethane dispersion comprises the following steps:

[0047] S11, mixing a polyol, a diisocyanate, a catalyst, and an organic solvent, and reacting to obtain a first reaction liquid, wherein the first reaction liquid contains a polyurethane prepolymer;

[0048] S12, adding a hydrophilic chain extender having a carboxyl group to the first reaction liquid, and after reaction, obtaining a second reaction liquid, wherein the second reaction liquid contains a polyurethane prepolymer having a carboxyl group;

[0049] S13, adding a neutralizing agent to the second reaction liquid, and after reaction, obtaining a polyurethane prepolymer with a hydrophilic group;

[0050] S14, dispersing the polyurethane prepolymer with hydrophilic groups into water to obtain the aqueous polyurethane dispersion.

[0051] In some embodiments, the method for preparing the anion-modified aqueous polyurethane dispersion includes steps S11 to S14 above, and further includes the following steps:

[0052] S15, mixing the aqueous polyurethane dispersion with an anionic hydrophilic monomer having an amino group, and reacting to obtain the anionic modified aqueous polyurethane dispersion.

[0053] In step S11 , the hydroxyl groups (-OH) in the polyol and the isocyanate groups (-NCO) in the diisocyanate undergo a polyaddition reaction to generate carbamate groups, also known as polyurethane groups (-NH-COO-), thereby forming a polyurethane prepolymer.

[0054] The reaction formula is: R-NCO+R'-OH→R-NH-COO-R';

[0055] Wherein: R-NCO represents a diisocyanate molecule, wherein R is an organic group of the diisocyanate; R'-OH represents a polyol molecule, wherein R' is an organic group in the polyol.

[0056] In step S12, a hydrophilic chain extender with a carboxyl group (such as 2,2-dimethylolpropionic acid) is subjected to a chain extension reaction with the end groups of the polyurethane prepolymer molecular chain, namely, the isocyanate group (-NCO) (after the reaction in step S11, the -NCO has basically reacted to form R-NH-COO-R', but the end groups at both ends of the obtained polyurethane prepolymer molecular chain are still -NCO groups), to form a polyurethane prepolymer with a carboxyl group (the end groups of which are still -NCO).

[0057] In step S13, a neutralizing agent (such as triethanolamine, NaOH) neutralizes the carboxyl groups in the polyurethane prepolymer with carboxyl groups to generate a waterborne polyurethane prepolymer with hydrophilic groups (the terminal groups at both ends of the polyurethane prepolymer are still -NCO).

[0058] In step S15, the amino groups in the anionic hydrophilic monomer with an amino group directly react with the terminal isocyanate groups in the waterborne polyurethane molecular chain to form urea groups (-NH-CO-NH-) for end-capping to obtain an anionic modified waterborne polyurethane prepolymer.

[0059] For example, an amino group reacts directly with an isocyanate group to form a urea linkage, and the reaction process is as follows:

[0060] R''-NCO+R'''-NH2→R''-NH-CO-NH-R''';

[0061] Among them, R''-NCO represents an organic molecule containing an isocyanate group; R'''-NH2 represents an organic molecule containing an amino group.

[0062] The resulting product R''-NH-CO-NH-R''' is a urea compound containing a urea group (-NH-CO-NH-).

[0063] In step S11, in some embodiments, the reaction temperature is 60-80° C., and the reaction time is 12-24 hours. For example, the reaction temperature can be 60° C., 65° C., 70° C., 75° C., or 80° C., and the reaction time can be 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0064] In step S11, in some embodiments, the polyol includes at least one of polyethylene glycol, polycaprolactone diol, polyethylene glycol dimethacrylate, and diethylene glycol, but is not limited thereto.

[0065] In some embodiments, the diisocyanate includes at least one of isophorone diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, and diphenylmethane diisocyanate, but is not limited thereto.

[0066] In some embodiments, the catalyst includes at least one of dibutyltin dilaurate, dimethyltin dihydroxyacetate, N,N-dimethylcyclohexylamine, and triethyl phosphate, but is not limited thereto.

[0067] In some embodiments, the organic solvent includes at least one of acetone and methyl ethyl ketone, but is not limited thereto.

[0068] In step S12, in some embodiments, the hydrophilic chain extender with a carboxyl group includes at least one of 2,2-dimethylol propionic acid and 2,2-dimethylol butyric acid, but is not limited thereto.

[0069] In step S12, in some embodiments, the reaction temperature is 60-80° C., and the reaction time is 2-5 hours. For example, the reaction temperature can be 60° C., 65° C., 70° C., 75° C., or 80° C., and the reaction time can be 2 hours, 3 hours, 4 hours, or 5 hours.

[0070] In step S13 , in some embodiments, the neutralizing agent includes at least one of triethanolamine (TEA) and NaOH, but is not limited thereto.

[0071] In step S13, in some embodiments, the reaction temperature is 60-80° C., and the reaction time is 2-5 hours. For example, the reaction temperature can be 60° C., 65° C., 70° C., 75° C., or 80° C., and the reaction time can be 2 hours, 3 hours, 4 hours, or 5 hours.

[0072] In step S14, in some embodiments, the anionic hydrophilic monomer having an amino group includes at least one of carbamate (such as sodium carbamate), sulfamate (such as sodium sulfamate) and methyl carbamate (sodium methyl carbamate), but is not limited thereto.

[0073] In some specific embodiments, the anionic hydrophilic monomer with an amino group includes at least one of 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 2-acrylamido-2-methylpropanesulfonic acid, and vinylbenzenesulfonate ammonium, but is not limited thereto.

[0074] In step S14, in some embodiments, the reaction temperature is 60-80° C., and the reaction time is 2-5 hours. For example, the reaction temperature can be 60° C., 65° C., 70° C., 75° C., or 80° C., and the reaction time can be 2 hours, 3 hours, 4 hours, or 5 hours.

[0075] In steps S11 and S12, in some embodiments, the mass ratio of the polyol, the diisocyanate, the catalyst, the hydrophilic chain extender with a carboxyl group, and the neutralizer is 1: (1.4-1.85): 0.01: (0.4-0.8): (0.4-0.8), for example, it can be 1: 1.4: 0.01: 0.4: 0.4, 1: 1.45: 0.01: 0.4: 0.4, 1: 1.65: 0.01: 0.6: 0.6, or 1: 1.85: 0.01: 0.8: 0.8, etc.

[0076] In step S14, in some embodiments, in the aqueous polyurethane dispersion, the mass ratio of the polyurethane prepolymer with hydrophilic groups to water is (1-3):1, for example, 1:1, 2:1, or 3:1.

[0077] In step S15, in some embodiments, the mass ratio of the aqueous polyurethane dispersion to the anionic hydrophilic monomer having an amino group is (1-3):1, for example, 1:1, 2:1, or 3:1.

[0078] In step S15, in some embodiments, the reaction temperature is 40-60° C., and the reaction time is 1-3 hours. For example, the reaction temperature can be 40° C., 45° C., 50° C., 55° C., or 60° C., and the reaction time can be 1 hour, 2 hours, or 3 hours.

[0079] In step S2, in some embodiments, the zinc salt includes at least one of zinc sulfate, zinc perchlorate, zinc trifluoromethanesulfonate and zinc fluoroborate, but is not limited thereto.

[0080] In some embodiments, the concentration of the zinc salt in the zinc salt aqueous solution is 0.05 to 1.0 mol / L, for example, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1.0 mol / L. The higher the concentration of the zinc salt in the zinc salt aqueous solution, the stronger the mechanical strength of the aqueous polyurethane gel electrolyte. This is because the zinc salt anions couple with water molecules and the hydrophilic groups of the aqueous polyurethane molecular chains through hydrogen bonds, thereby increasing the aggregation of the polyurethane molecular chains and thereby increasing the mechanical strength. Different zinc salt concentrations in the zinc salt aqueous solution will produce aqueous polyurethane gel electrolytes with different water contents.

[0081] In step S2, the first dispersion can be placed in a -50°C environment for freeze molding to obtain an aqueous polyurethane matrix, and the aqueous polyurethane matrix is immersed in a zinc salt aqueous solution for a period of time, so that the zinc salt aqueous solution penetrates into the aqueous polyurethane matrix to induce the Hofmeister effect. When the zinc salt anions come into contact with the amphiphilic molecular chains in the aqueous polyurethane, strong hydrogen bonds are formed between the zinc salt anions, water molecules and the hydrophilic groups of the polyurethane molecular chains, causing the molecular chains to cross-link until the polyurethane is solidified and forms an elastic gel material. The surface moisture is wiped off to obtain the aqueous polyurethane gel electrolyte.

[0082] An embodiment of the present invention further provides an aqueous polyurethane gel electrolyte, wherein the aqueous polyurethane gel electrolyte is prepared using the preparation method of the present invention as described above.

[0083] An embodiment of the present invention further provides a zinc ion battery, wherein the zinc ion battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte located between the positive electrode sheet and the negative electrode sheet, and the electrolyte is the aqueous polyurethane gel electrolyte described above in the embodiment of the present invention.

[0084] The zinc ion battery provided by the embodiment of the present invention has a high voltage platform and energy density. Of course, in the present invention, the positive electrode plate, the aqueous polyurethane gel electrolyte and the negative electrode plate can be arranged and then packaged by aluminum-plastic film or the like.

[0085] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode dressing layer located on the positive electrode current collector, the positive electrode current collector includes one of carbon cloth and graphite paper, and the positive electrode dressing layer includes a positive electrode active material (such as graphite), a conductive agent (conductive carbon black) and a binder (such as polyvinylidene fluoride, abbreviated as PVDF).

[0086] In some embodiments, the method for preparing the positive electrode sheet comprises the following steps:

[0087] providing a positive electrode current collector;

[0088] The positive electrode active material, the conductive agent and the binder are mixed in a preset ratio (e.g., a mass ratio of 8:1:1), and then an organic solvent (e.g., N-methylpyrrolidone) is added and mixed to obtain a positive electrode slurry;

[0089] The positive electrode slurry is coated on the positive electrode current collector and dried to obtain the positive electrode sheet.

[0090] In some embodiments, the negative electrode plate is zinc foil or the like.

[0091] The present invention will be further described below with reference to specific examples.

[0092] Example 1

[0093] This embodiment provides a method for preparing an aqueous polyurethane gel electrolyte, comprising the following steps:

[0094] 30 g of polyethylene glycol, 42 g of isophorone diisocyanate, 0.3 g of dibutyltin dilaurate, and 100 g of acetone were mixed and stirred, and reacted at 80° C. under a nitrogen atmosphere for 12 hours to obtain a first reaction liquid containing a polyurethane prepolymer;

[0095] 12 g of 2,2-dimethylolpropionic acid was added to the first reaction liquid, and the mixture was reacted at 80° C. for 2 h to obtain a second reaction liquid;

[0096] 12 g of TEA was added to the second reaction solution, and the mixture was reacted at 80° C. for 2 h to obtain a polyurethane prepolymer with a hydrophilic group.

[0097] Dispersing 30 g of a polyurethane prepolymer having a hydrophilic group into 30 g of water to obtain an aqueous polyurethane dispersion;

[0098] 50 g of 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt and 50 g of the above aqueous polyurethane dispersion were mixed and reacted at 60° C. for 2 h to obtain an anion-modified aqueous polyurethane dispersion;

[0099] The anion-modified waterborne polyurethane dispersion is placed in a -50°C low-temperature box for freeze molding to obtain a waterborne polyurethane matrix;

[0100] The concentration is 0.05 mol·L -1 The aqueous solution of zinc sulfate was used to immerse the waterborne polyurethane matrix in 0.05 mol·L -1 The aqueous solution of zinc sulfate was immersed in the aqueous polyurethane for 1 hour to allow the aqueous solution of zinc sulfate to penetrate into the aqueous polyurethane matrix and induce the Hofmeister effect until the aqueous polyurethane solidified and formed an elastic gel material. The surface moisture was wiped off to obtain an aqueous polyurethane gel electrolyte (such as Figure 3 shown).

[0101] At the same time, the concentration of 0.1 mol·L -1 , 0.5 mol·L -1 and 1.0 mol·L -1 The above waterborne polyurethane matrix was immersed in 0.1 mol·L -1 , 0.5 mol·L -1 and 1.0 mol L -1The zinc sulfate aqueous solution was placed in the aqueous polyurethane matrix for 1 h to allow the zinc sulfate aqueous solution to penetrate into the aqueous polyurethane matrix and induce the Hofmeister effect until the aqueous polyurethane solidified and formed an elastic gel material. The surface moisture was wiped off to obtain three other aqueous polyurethane gel electrolytes, such as Figure 3 shown.

[0102] The linear sweep voltammetry curves of the above four aqueous polyurethane gel electrolytes were tested using an electrochemical workstation, and their electrochemical stability windows were measured. Specifically, a zinc sheet was used as the counter electrode and reference electrode, an inert stainless steel sheet was used as the working electrode, and the aqueous polyurethane gel electrolyte was placed between the zinc sheet and the stainless steel sheet to assemble into a button cell. The linear sweep voltammetry mode was set on the electrochemical workstation to test the electrochemical stability window of the button cell (i.e., the aqueous polyurethane gel electrolyte).

[0103] The results are as follows Figure 4 The results show that with the increase of zinc salt concentration, the voltage stability window of aqueous polyurethane gel electrolyte gradually widens, reaching up to 2.6 V (relative to Zn / Zn 2+ The standard electrode potential of the redox couple is 2.6 V, and the concentration of zinc salt used to prepare the aqueous polyurethane gel electrolyte is 1.0 mol·L -1 ), and the zinc salt concentration was 0.05 mol·L -1 The obtained aqueous polyurethane gel electrolyte was broadened by about 0.6V.

[0104] This embodiment also provides a method for preparing a flexible zinc ion battery, wherein an aqueous polyurethane gel electrolyte (composed of 1.0 mol·L -1 The flexible zinc ion battery is assembled by immersing the flexible zinc ion battery in an aqueous zinc sulfate aqueous solution. The flexible zinc ion battery is an aqueous secondary zinc ion battery system. The preparation of the flexible zinc ion battery includes the following steps:

[0105] (1) Preparation of flexible positive electrode sheets

[0106] A flexible conductive carbon cloth with a thickness of 0.2 mm was used as the positive electrode current collector, graphite was used as the positive electrode material, conductive carbon black was used as the conductive agent, and water-soluble PVDF was used as the binder. Graphite, water-soluble PVDF and conductive carbon black were mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone was added and fully ground to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on the flexible conductive carbon cloth and placed in an oven to dry to obtain a flexible positive electrode sheet.

[0107] (2) Battery assembly

[0108] A 0.2mm thick zinc sheet was used as the flexible negative electrode, and nickel tabs (specifications: thickness × width × length 0.1mm × 2mm × 20mm) were attached to the flexible positive and negative electrodes using white adhesive tape.

[0109] The flexible negative electrode sheet, aqueous polyurethane gel electrolyte and flexible positive electrode sheet are assembled in order to form a battery cell, and then the battery cell is encapsulated with an aluminum-plastic film through a vacuum heat sealing machine to obtain a flexible zinc-ion battery.

[0110] The cyclic voltammetry curve of the flexible zinc ion battery was tested by an electrochemical workstation, and its voltage platform was obtained. Figure 5 As shown, its voltage platform is about 2.06V.

[0111] Example 2

[0112] This embodiment provides a method for preparing an aqueous polyurethane gel electrolyte, comprising the following steps:

[0113] 30 g of polyethylene glycol, 49.5 g of isophorone diisocyanate, 0.3 g of dimethyltin dihydroxyacetate, and 100 g of acetone were mixed and stirred, and reacted at 80° C. under a nitrogen atmosphere for 12 hours to obtain a first reaction liquid containing a polyurethane prepolymer;

[0114] 18 g of 2,2-dimethylolpropionic acid was added to the first reaction liquid, and the mixture was reacted at 80° C. for 3 h to obtain a second reaction liquid;

[0115] 18 g of TEA was added to the second reaction solution, and the mixture was reacted at 80° C. for 3 h to obtain a polyurethane prepolymer with a hydrophilic group.

[0116] Dispersing 30 g of a polyurethane prepolymer having a hydrophilic group into 20 g of water to obtain an aqueous polyurethane dispersion;

[0117] 10 g of 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt and 20 g of the above aqueous polyurethane dispersion were mixed and reacted at 60° C. for 3 h to obtain an anion-modified aqueous polyurethane dispersion;

[0118] The anion-modified waterborne polyurethane dispersion is placed in a -50°C low-temperature box for freeze molding to obtain a waterborne polyurethane matrix;

[0119] The concentration is 0.1 mol·L -1 The aqueous polyurethane matrix was immersed in a 0.1 mol·L zinc sulfate aqueous solution. -1The zinc sulfate aqueous solution was immersed in the aqueous polyurethane for 2 hours to allow the zinc sulfate aqueous solution to penetrate into the aqueous polyurethane matrix to induce the Hofmeister effect until the aqueous polyurethane was solidified and formed into an elastic gel material. The surface moisture was wiped off to obtain an aqueous polyurethane gel electrolyte.

[0120] This embodiment also provides a method for preparing a flexible zinc ion battery, which differs from Example 1 only in that the aqueous polyurethane gel electrolyte prepared in Example 2 is used.

[0121] Example 3

[0122] This embodiment provides a method for preparing an aqueous polyurethane gel electrolyte, comprising the following steps:

[0123] 30 g of polyethylene glycol, 54 g of isophorone diisocyanate, 0.3 g of N,N-dimethylcyclohexylamine, and 100 g of acetone were mixed and stirred, and reacted at 80° C. under a nitrogen atmosphere for 12 hours to obtain a first reaction liquid containing a polyurethane prepolymer;

[0124] 24 g of 2,2-dimethylolpropionic acid was added to the first reaction liquid, and the mixture was reacted at 80° C. for 4 h to obtain a second reaction liquid;

[0125] 24 g of TEA was added to the second reaction solution, and the mixture was reacted at 80° C. for 4 h to obtain a polyurethane prepolymer with a hydrophilic group.

[0126] Dispersing 30 g of a polyurethane prepolymer having a hydrophilic group into 10 g of water to obtain an aqueous polyurethane dispersion;

[0127] 10 g of 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt and 30 g of the above aqueous polyurethane dispersion were mixed and reacted at 60° C. for 3 h to obtain an anion-modified aqueous polyurethane dispersion;

[0128] The anion-modified waterborne polyurethane dispersion is placed in a -50°C low-temperature box for freeze molding to obtain a waterborne polyurethane matrix;

[0129] The preparation concentration is 1.0 mol·L -1 The aqueous solution of zinc sulfate was used to immerse the waterborne polyurethane matrix in 1.0 mol·L -1 The aqueous solution of zinc sulfate was immersed in the aqueous polyurethane for 0.5 h to allow the aqueous solution of zinc sulfate to penetrate into the aqueous polyurethane matrix and induce the Hofmeister effect until the aqueous polyurethane was solidified and formed into an elastic gel material. The surface moisture was wiped off to obtain an aqueous polyurethane gel electrolyte.

[0130] This embodiment also provides a method for preparing a flexible zinc ion battery, which differs from Example 1 only in that the aqueous polyurethane gel electrolyte prepared in Example 3 is used.

[0131] In summary, the present invention provides an aqueous polyurethane gel electrolyte, a preparation method thereof, and a zinc ion battery. The present invention freeze-forms an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion, then immerses it in a zinc salt aqueous solution to form a hydrogel matrix. Simultaneously, the Hofmeister effect is utilized to form strong hydrogen bonds between the hydrophilic groups of the aqueous polyurethane, zinc salt anions, and water molecules in the hydrogel matrix, inducing the conversion of free water molecules within the hydrogel matrix into bound water. This results in an aqueous polyurethane gel electrolyte with a wide voltage window and high ionic conductivity, thereby enabling zinc ion batteries to achieve a higher voltage platform and energy density. Furthermore, the method provided by the present invention is low-cost and highly safe.

[0132] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an aqueous polyurethane gel electrolyte, characterized in that: The steps include: Providing a first dispersion, wherein the first dispersion is an aqueous polyurethane dispersion or an anion-modified aqueous polyurethane dispersion, wherein the dispersion medium of the aqueous polyurethane dispersion is water, and the dispersion medium of the anion-modified aqueous polyurethane dispersion is water; the anion-modified aqueous polyurethane dispersion is obtained by reacting the aqueous polyurethane dispersion with an anionic hydrophilic monomer having an amino group; After the first dispersion is freeze-formed, it is immersed in a zinc salt aqueous solution to induce the Hofmeister effect, thereby obtaining an aqueous polyurethane gel electrolyte containing zinc salt anions. At the same time, hydrogen bonds are formed between the aqueous polyurethane hydrophilic groups, zinc salt anions and water molecules in the aqueous polyurethane gel electrolyte, thereby inducing the conversion of free water molecules in the aqueous polyurethane gel electrolyte into bound water.

2. The method for preparing an aqueous polyurethane gel electrolyte according to claim 1, wherein: The preparation method of the aqueous polyurethane dispersion comprises the following steps: Mixing a polyol, a diisocyanate, a catalyst, and an organic solvent, and reacting the mixture to obtain a first reaction liquid containing a polyurethane prepolymer; adding a hydrophilic chain extender having a carboxyl group to the first reaction liquid, and reacting to obtain a second reaction liquid containing a polyurethane prepolymer having a carboxyl group; adding a neutralizing agent to the second reaction liquid to obtain a polyurethane prepolymer having a hydrophilic group after reaction; The polyurethane prepolymer with hydrophilic groups is dispersed in water to obtain the aqueous polyurethane dispersion.

3. The method for preparing an aqueous polyurethane gel electrolyte according to claim 1, wherein: The preparation method of the anion-modified aqueous polyurethane dispersion comprises the following steps: Mixing a polyol, a diisocyanate, a catalyst, and an organic solvent, and reacting the mixture to obtain a first reaction liquid containing a polyurethane prepolymer; adding a hydrophilic chain extender having a carboxyl group to the first reaction liquid, and reacting to obtain a second reaction liquid containing a polyurethane prepolymer having a carboxyl group; adding a neutralizing agent to the second reaction liquid to obtain a polyurethane prepolymer having a hydrophilic group after reaction; dispersing the polyurethane prepolymer with hydrophilic groups into water to obtain the aqueous polyurethane dispersion; The aqueous polyurethane dispersion is mixed with an anionic hydrophilic monomer having an amino group, and after reaction, the anionic modified aqueous polyurethane dispersion is obtained.

4. The method for preparing an aqueous polyurethane gel electrolyte according to claim 2 or 3, characterized in that: The polyol comprises at least one of polyethylene glycol, polycaprolactone diol, polyethylene glycol dimethacrylate and diethylene glycol; The diisocyanate comprises at least one of isophorone diisocyanate, hexamethylene diisocyanate, lysine diisocyanate and diphenylmethane diisocyanate; The catalyst comprises at least one of dibutyltin dilaurate, dimethyltin dihydroxyacetate, N,N-dimethylcyclohexylamine and triethyl phosphate; The hydrophilic chain extender with a carboxyl group includes at least one of 2,2-dimethylol propionic acid and 2,2-dimethylol butyric acid; The neutralizing agent includes at least one of triethanolamine and NaOH.

5. The method for preparing an aqueous polyurethane gel electrolyte according to claim 1 or 3, characterized in that: The anionic hydrophilic monomer having an amino group includes at least one of carbamate, sulfamate and methyl carbamate.

6. The method for preparing an aqueous polyurethane gel electrolyte according to claim 1, wherein: The zinc salt includes at least one of zinc sulfate, zinc perchlorate, zinc trifluoromethanesulfonate and zinc fluoborate; and the concentration of the zinc salt in the zinc salt aqueous solution is 0.05-1.0 mol / L.

7. The method for preparing an aqueous polyurethane gel electrolyte according to claim 2 or 3, characterized in that: The mass ratio of polyol, diisocyanate, catalyst, hydrophilic chain extender with carboxyl group and neutralizer is 1: (1.4~1.85): 0.01:（0.4~0.8）:（0.4~0.8）； In the aqueous polyurethane dispersion, the mass ratio of the polyurethane prepolymer with hydrophilic groups to water is (1-3):

1.

8. The method for preparing an aqueous polyurethane gel electrolyte according to claim 3, wherein: The mass ratio of the aqueous polyurethane dispersion to the anionic hydrophilic monomer with an amino group is (1-3):

1.

9. An aqueous polyurethane gel electrolyte, characterized in that The aqueous polyurethane gel electrolyte is prepared by the preparation method according to any one of claims 1 to 8.

10. A zinc ion battery, characterized in that: The zinc ion battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte located between the positive electrode sheet and the negative electrode sheet, and the electrolyte is the aqueous polyurethane gel electrolyte according to claim 9.

Images