Chiral hydrogel electrolyte based on supramolecular assembly and preparation method thereof

Abstract

The application belongs to the technical field of chemical energy storage batteries, and particularly provides a chiral hydrogel electrolyte based on supramolecular assembly and a preparation method thereof, so as to solve the problems of ion channel disorder and insufficient free water binding of traditional non-chiral gel electrolytes; the application introduces single pure configuration chiral guest molecules into a non-chiral polymer substrate, forms a supramolecular chiral film based on stereodirectional supramolecular assembly, and obtains a chiral hydrogel electrolyte after swelling and saturation in an aqueous electrolyte; the chiral guest molecules reshape the topological network of the polymer as topological guests, form a stereodirectional network, and make the energy storage modulus of the gel jump, so that the gel has the ability to resist dendrite penetration; at the same time, the chiral guest molecules can realize interface stabilization of the negative electrode and further inhibit the negative electrode dendrite; in addition, the stereodirectional network can greatly limit the activity of free water molecules and eliminate the corrosion of free water molecules on the vanadium positive electrode and vanadium dissolution.

Description

Technical Field

[0001] This invention belongs to the field of chemical energy storage battery technology, specifically providing a chiral hydrogel electrolyte based on supramolecular assembly and its preparation method. Background Technology

[0002] In the global acceleration of the green energy transition, aqueous zinc-ion batteries (AZIBs) have advantages such as intrinsic safety, low manufacturing cost, and environmental friendliness, showing great commercial potential in the field of large-scale energy storage. However, in practical applications, especially under high-rate (e.g., 5 A / g) operating conditions, aqueous zinc-ion batteries face severe dual-domain interface instability. On the positive electrode side, highly active free water molecules frequently attack the crystal framework of the vanadium-based positive electrode, leading to severe vanadium dissolution and phase structure collapse, causing irreversible capacity decay. At the same time, zinc ions in a highly solvated state face an extremely high desolvation energy barrier when intercalating into the positive electrode interface, resulting in extremely slow ion transport dynamics at high rates. On the negative electrode side, free water molecules easily induce severe hydrogen evolution reaction (HER) and interface corrosion, and zinc ions undergo disordered three-dimensional aggregation, forming sharp zinc dendrites that rapidly pierce the separator, causing internal short circuits in the battery.

[0003] To address these issues, researchers have widely employed hydrogel electrolytes (such as polyacrylamide and polyvinyl alcohol) to bind free water molecules and act as physical membranes. However, existing gel systems and electrolyte modifiers largely rely on common additive molecules, whose fatal flaw lies in their ability to provide only isotropic one-dimensional chemical affinity, such as simple polar adsorption or disordered hydrogen bond networks, thus creating insurmountable technological blind spots. On the one hand, within the gel phase, traditional achiral polymers can only form disordered, randomly coiled three-dimensional networks, and these pores severely hinder the absorption of Zn. 2+ The rapid migration of these molecules cannot support high-current, high-rate discharge, and their loose network cannot achieve ultimate topological binding of water molecules. On the other hand, at the electrode interface, ordinary additive molecules can only spread out on the metal surface and cannot accurately identify and deeply fill the microscopic high-energy defect sites with three-dimensional asymmetry, thus making it difficult to effectively control dendrite growth and ion transport.

[0004] In supramolecular chemistry and biology, the specific binding of macromolecules to substrates is highly dependent on the lock-and-key model generated by chiral molecules with three-dimensional spatial asymmetry. Based on this, introducing the spatial stereorecognition mechanism of chiral molecules into the design of gel electrolytes holds promise for reshaping polymer topological networks and precisely controlling interfacial reactions across the entire electrode domain through their geometric interlocking effect. However, blindly introducing chiral mixtures into the gel system without considering the racemic self-quenching effect in stereochemistry (Wallach's rule: heterochiral molecules readily self-aggregate and lose their cross-linking ability) not only fails to fully utilize the interfacial regulation role of chiral molecules but also negatively impacts the macroscopic properties of the gel and the cycle life of the battery. Therefore, this invention proposes a chiral hydrogel electrolyte based on supramolecular assembly, its preparation method, and its applications, which is expected to solve many problems in aqueous zinc-ion batteries. Summary of the Invention

[0005] The purpose of this invention is to provide a chiral hydrogel electrolyte based on supramolecular assembly and its preparation method, in order to solve the problems of disordered ion channels and insufficient free water binding in traditional achiral gel electrolytes. This invention introduces a single pure configuration chiral guest molecule (pure R configuration or pure S configuration) with specific spatial asymmetry into an achiral polymer substrate as a topological guest template. Stereo-oriented supramolecular assembly is achieved using the host-guest stereomatching mechanism of supramolecular chemistry to form a supramolecular chiral membrane. After swelling and saturation in an aqueous electrolyte, a chiral hydrogel electrolyte is obtained by introducing chiral molecules with different configurations. A single, pure chiral guest molecule (pure enantiomer) acts as a topological guest, reshaping the polymer topological network to form a stereo-oriented network. This causes a sudden leap in the storage modulus (G') of the gel, resulting in extremely strong resistance to dendrite penetration. Simultaneously, the free, single, pure chiral guest molecule can achieve interfacial stability at the negative electrode, further suppressing dendrite formation. Furthermore, the stereo-oriented network, while constructing ordered ion channels, greatly restricts the activity of free water molecules, achieving topological binding and eliminating the erosion of the vanadium cathode by free water molecules and the dissolution of vanadium.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A chiral hydrogel electrolyte based on supramolecular assembly includes: an aqueous electrolyte and a supramolecular chiral membrane, wherein the supramolecular chiral membrane is immersed in the aqueous electrolyte and swells to saturation to form a chiral hydrogel electrolyte; the supramolecular chiral membrane is composed of a non-chiral polymer substrate and chiral guest molecules, wherein the chiral guest molecules are pure enantiomers, and the chiral guest molecules account for 1 wt% to 7 wt% of the non-chiral polymer substrate by mass.

[0008] Furthermore, the non-chiral polymer substrate is one or two of polyurethane acrylate (PUA), polyethylene glycol diacrylate (PEGDA), hydroxyethyl methacrylate (HEMA), acrylamide (AM), N-isopropylacrylamide (NIPAM), and polyvinyl alcohol (PVA).

[0009] Furthermore, the non-chiral polymer substrate is a mixture of two polymer monomers with a mass ratio between 1:1 and 4:1. It should be noted that, taking polymer monomer A and polymer monomer B as an example, the mass ratio of polymer monomer A to polymer monomer B is between 1:1 and 4:1, or the mass ratio of polymer monomer B to polymer monomer A is between 1:1 and 4:1. By adjusting the mass ratio, the three-dimensional cavity size and polar microenvironment of the polymer network can be changed to achieve perfect host-guest stereo matching with chiral guest molecules.

[0010] Furthermore, the chiral guest molecule is one of (R)-(+)-3-chloro-1-phenyl-1-propanol, (S)-(-)-3-chloro-1-phenyl-1-propanol, (R)-1-phenylethanol, and (S)-1-phenylethanol.

[0011] Furthermore, the aqueous electrolyte is an aqueous zinc electrolyte, wherein the concentration of zinc salt is 0.5 mol / L to 3 mol / L.

[0012] Furthermore, the zinc salt is one or more of zinc methanesulfonate, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonate)imide, zinc hexafluorophosphate, zinc perchlorate, and zinc nitrate.

[0013] Meanwhile, this invention provides a method for preparing the above-mentioned chiral hydrogel electrolyte based on supramolecular assembly, comprising the following steps:

[0014] Step 1: Select a non-chiral polymer substrate precursor, add it to a solvent and stir to dissolve it, forming a non-chiral polymer substrate solution with a large number of hydrogen bond donor and acceptor sites;

[0015] Step 2: Add chiral guest molecules to the non-chiral polymer substrate solution, then add crosslinking initiator, and stir at 15℃~35℃ for 6 h~24 h under light-protected conditions to allow the chiral guest molecules to complete the spatial three-dimensional pre-assembly with the micro-cavities of the non-chiral polymer substrate, and obtain the gel prepolymer solution.

[0016] Step 3: Inject the gel prepolymer into the mold, cure it under ultraviolet light, and then dry it to obtain a supramolecular chiral membrane; during the ultraviolet curing process, the wavelength of the ultraviolet lamp is 254 nm ~ 365 nm, and the irradiation time is 5 min ~ 60 min; during the drying process, the drying temperature is 60℃ ~ 90℃.

[0017] Step 4: Immerse the supramolecular chiral membrane in an aqueous electrolyte solution until it swells and becomes saturated to obtain a chiral hydrogel electrolyte.

[0018] Furthermore, in step 1, the solvent is one or more of anhydrous ethanol, methanol, and N,N-methyleneformamide; in step 2, the crosslinking initiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). To reduce the damage to the chiral carbon molecules caused by free radical hydrogen abstraction during UV curing and the interference of background light absorption, the amount of TPO added is 0.1 wt% to 0.5 wt% of the mass of the non-chiral polymer substrate.

[0019] Furthermore, in step 3, the amount of gel prepolymer injected into the mold is 50 μl to 500 μl.

[0020] Based on the above technical solution, the beneficial effect of the present invention is to provide a chiral hydrogel electrolyte based on supramolecular assembly and its preparation method, which has the following advantages:

[0021] 1) Macroscopic mechanical transition: This invention introduces a single pure configuration chiral guest molecule (pure R configuration or pure S configuration) with specific spatial asymmetry as a topological guest template, which not only overcomes the racemic self-quenching effect, but also achieves perfect host-guest three-point stereo matching in the polymer substrate, significantly increasing the effective crosslinking point density of the supramolecular transient network, causing a sudden leap in the storage modulus (G') of the gel, thereby possessing strong mechanical properties and achieving resistance to dendrite penetration;

[0022] 2) Topologically Remodeled Ion Channels: Single, pure-configuration chiral guest molecules act as topological guests, remodeling the polymer topological network to form a stereo-oriented network, constructing high-speed ion channels with low desolvation energy barriers, thus providing Zn... 2+ Provides a migration channel to enable Zn 2+ The rapid migration of the molecules allows aqueous zinc-ion batteries to exhibit exceptional kinetic performance and cycle retention even at extreme rates of 5 A / g.

[0023] 3) Topological binding of free water molecules: The stereo-oriented network can greatly limit the activity of free water molecules, converting them into water bound by strong hydrogen bonds, thus fundamentally eliminating the erosion and dissolution of vanadium cathode by free water molecules;

[0024] 4) Crystal plane geometry specific anchoring: More favorable pure configuration chiral guest molecules, with their unique 3D spatial asymmetry, can specifically lock into and passivate the defect sites of zinc anode like a lock-and-key mechanism, induce dense, horizontal epitaxial deposition of zinc ions and generate Zn(002) crystal planes, further suppress dendrite growth and achieve interface stability of anode. Attached Figure Description

[0025] Figure 1 The images show the circular dichroism spectra of the hydrogel electrolytes in Examples 1 and 4 and Comparative Example 1 of this invention.

[0026] Figure 2 This is a schematic diagram of the polymer network structure and zinc dendrite growth of the hydrogel electrolyte in Example 1 of the present invention.

[0027] Figure 3 This is a schematic diagram of the polymer network structure and zinc dendrite growth of the hydrogel electrolyte in Comparative Example 1 of the present invention.

[0028] Figure 4 The figures show the rheological test results of the hydrogel electrolytes in Examples 1 and 4 and Comparative Example 1 of this invention.

[0029] Figure 5 The image shows the infrared (ATR-FTIR) test results of the hydrogel electrolyte in Example 1 and Comparative Example 1 of this invention.

[0030] Figure 6 The graph shows the cycle life test results of the symmetrical batteries in Examples 1 and 4 and Comparative Example 1 of this invention.

[0031] Figure 7 The graph shows the high-rate cycling performance test results of the full cells in Examples 1 and 4 and Comparative Example 1 of this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Example 1: This example provides a chiral hydrogel electrolyte based on supramolecular assembly, prepared by the following steps:

[0034] Step 1: Weigh 0.2 g of polyurethane acrylate (PUA) and 0.1 g of acrylamide (AM), add them to 2 mL of N,N-dimethylformamide solvent and stir to dissolve, forming a non-chiral polymer substrate solution with a large number of hydrogen bond donor and acceptor sites;

[0035] Step 2: Add 50 mg of pure enantiomeric (R)-3-chloro-1-phenyl-1-propanol as a chiral guest molecule to the achiral polymer substrate solution, followed by 9 mg of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). Stir at room temperature under light-protected conditions until the pure chiral guest molecule and the microscopic cavity of the achiral polymer substrate complete spatial stereo pre-assembly to obtain the gel prepolymer solution.

[0036] Step 3: Take 300 μL of gel prepolymer solution and inject it into a special mold. Irradiate it with a UV lamp with a wavelength of 365 nm for 10 min to complete the photocuring and crosslinking. Then transfer the gel to an oven and dry it at 80 °C to remove the solvent and obtain a supramolecular chiral membrane.

[0037] Step 4: Immerse the chiral membrane in an aqueous electrolyte containing zinc trifluoromethanesulfonate (concentration of 3 mol / L) for 24 h. After swelling and saturation, a chiral hydrogel electrolyte is obtained.

[0038] Furthermore, based on the aforementioned chiral hydrogel electrolyte, it is assembled together with a zinc negative electrode and a vanadium dioxide positive electrode to form an aqueous zinc-ion battery.

[0039] Example 2: This example also provides a chiral hydrogel electrolyte based on supramolecular assembly. The difference between this example and Example 1 is that in step 1, 0.3 g of polyurethane acrylate (PUA) and 0.1 g of acrylamide (AM) are weighed and added to N,N-dimethylformamide solvent and stirred to dissolve.

[0040] Example 3: This example also provides a chiral hydrogel electrolyte based on supramolecular assembly. The difference between this example and Example 1 is that in step 1, 0.2 g of polyurethane acrylate (PUA) and 0.1 g of polyvinyl alcohol (PVA) are weighed and added to 2 mL of methanol solvent and stirred to dissolve.

[0041] Example 4: This example also provides a chiral hydrogel electrolyte based on supramolecular assembly. The difference between this example and Example 1 is that in step 2, 50 mg of pure enantiomer (S)-3-chloro-1-phenyl-1-propanol is added to the non-chiral polymer substrate solution as a chiral guest molecule.

[0042] Example 5: This example also provides a chiral hydrogel electrolyte based on supramolecular assembly. The difference between this example and Example 1 is that in step 2, 50 mg of pure enantiomer (R)-1-phenylethanol is added to the non-chiral polymer substrate solution as a chiral guest molecule.

[0043] Example 6: This example also provides a chiral hydrogel electrolyte based on supramolecular assembly. The difference between this example and Example 1 is as follows: In step 3, 150 μL of gel prepolymer solution is injected into a special mold and irradiated with a 302 nm ultraviolet lamp for 15 min to complete photocuring and crosslinking. Then, the gel is transferred to an oven and dried at 60 °C to remove the solvent and obtain a supramolecular chiral membrane. In step 4, the chiral membrane is immersed in an aqueous electrolyte containing zinc hexafluorophosphate (concentration of 3 mol / L) for 24 h. After swelling and saturation, the chiral hydrogel electrolyte is obtained.

[0044] The beneficial effects of the present invention will be described in detail below with reference to the test. During the electrochemical performance test, the chiral hydrogel electrolytes prepared in Examples 1 to 6 were assembled to form button cells and symmetrical cells. In the button cells, the negative electrode is a zinc negative electrode sheet, and the positive electrode can be a vanadium pentoxide positive electrode sheet, a vanadium dioxide positive electrode sheet, or a sodium metavanadate positive electrode sheet. In the symmetrical cells, both the negative electrode and the positive electrode are zinc electrode sheets.

[0045] In addition, to more intuitively demonstrate the beneficial effects of the present invention, the present invention also provides a comparative example; Comparative Example 1 provides a hydrogel electrolyte, which differs from Example 1 in that: in step 2, 50 mg of racemate (Race, i.e., a 1:1 mixture of R and S configurations) is added to the non-chiral polymer base solution as a guest molecule.

[0046] The hydrogel electrolytes prepared in the above examples and comparative examples were characterized by circular dichroism spectroscopy. Taking Examples 1, 4, and Comparative Example 1 as examples, the results are as follows: Figure 1 As shown in the figure, even after introducing the achiral polymer substrate, the gel system can still capture the typical Cotton effect signal from the R-configuration or S-configuration chiral guest molecules, proving that the achiral polymer substrate does not destroy the intrinsic stereoconfiguration of the chiral molecules. The guest molecules successfully maintain their three-dimensional spatial asymmetry in the complex supramolecular gel microenvironment, laying the structural foundation for subsequent interface stereo recognition and crystal facet regulation.

[0047] Independent gradient model nonvalent interaction (IGMH) analysis was performed on the hydrogel electrolytes prepared in the above examples and comparative examples. Taking Example 1 and Comparative Example 1 as examples, the results are as follows: Figure 2 and Figure 3 As shown in the figure, the pure R-type configuration (Example 1) constructs a highly spatially ordered molecular chiral framework through richer intermolecular interactions with the polymer. This structure optimizes ion transport channels, exhibiting significant electrochemical performance advantages. Furthermore, it effectively reduces the content of interfacial active water through steric hindrance, thereby suppressing side reactions. Simultaneously, this network can achieve Zn... 2+ The directional reconstruction of the solvation structure significantly reduces the desolvation energy barrier, promotes efficient ion conduction, and induces a uniform ion flux on the electrode surface, thereby suppressing the disordered growth of zinc dendrites and achieving uniform deposition of zinc ions on the electrode surface.

[0048] Rheological tests were performed on the hydrogel electrolytes prepared in the above embodiments and comparative examples. Taking Examples 1, 4, and Comparative Example 1 as examples, the results are as follows: Figure 4As shown in the figure, the pure R configuration forms the densest cross-linked network due to perfect spatial geometric resonance; while Race undergoes chiral self-sorting, internal association, and loss of cross-linking ability, proving the decisive role of stereotactic orientation in the construction of supramolecular networks, further verifying the accuracy of the visualization evidence of electron density at the microscopic level, and profoundly elucidating that the enantiomeric stereotactic interlocking effect is the underlying core of constructing high-strength and tough topological ionogel networks.

[0049] The aqueous zinc-ion batteries prepared in the above examples and comparative examples were subjected to crystallographic orientation and deposition morphology (GIWAXS) tests. The negative electrode surface after cycling was characterized by grazing incidence wide-angle X-ray scattering. Taking Example 1 and Comparative Example 1 as examples, the TC(002) result of the chiral hydrogel electrolyte in Example 1 was as high as 1.23, while the TC(002) of Comparative Example 1 was only 1.08. This proves that pure R-configuration chiral molecules can accurately identify and passivate three-dimensional high-energy defects, induce horizontal epitaxial deposition of zinc, and thus effectively suppress dendrite growth in the electrochemical process.

[0050] The hydrogel electrolytes prepared in the above examples and comparative examples were subjected to infrared spectroscopy (ATR-FTIR) testing. Taking Example 1 and Comparative Example 1 as examples, the infrared spectrum at 3000 cm⁻¹ was measured. -1 ~3600 cm -1 Gaussian peak fitting was performed on the region, and the results are as follows: Figure 5 As shown in the figure, the hydrogel electrolyte in Example 1, which introduced a pure R-configuration chiral shell molecule, exhibited a significantly higher proportion of strongly bound water peak area compared to Comparative Example 1, while the harmful free water peak was drastically reduced. This demonstrates that highly efficient topological binding of free water in the electrolyte is achieved, indicating that the introduction of a single pure configuration chiral guest molecule can improve the topological binding of Zn. 2+ Its solvation structure effectively suppresses free water.

[0051] The hydrogel electrolytes prepared in the above examples and comparative examples were tested for cycle life and high-rate cycling performance. Taking Examples 1, 4, and Comparative Example 1 as examples, the results are as follows: Figure 6 and Figure 7 As shown; by Figure 6 As can be seen, the symmetrical cell in Example 1 operates at a current density of 0.5 mA / cm². 2 The surface capacity is 0.5 mAh / cm². 2 Under these conditions, stable cycling of up to 5800 hours was achieved; Figure 7As can be seen, under an ultra-high current of 5 A / g, the full cell in Example 1 still maintained 81% discharge specific capacity and nearly 100% coulombic efficiency; thus, the chiral hydrogel electrolyte provided by the present invention can not only effectively suppress the dendrite problem of zinc anode, but also completely suppress the dissolution of vanadium-based cathode, achieving excellent universal global interface stability.

[0052] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A chiral hydrogel electrolyte based on supramolecular assembly, characterized in that, include: An aqueous electrolyte and a supramolecular chiral membrane, wherein the supramolecular chiral membrane is immersed in the aqueous electrolyte and swells to saturation to form a chiral hydrogel electrolyte; The supramolecular chiral membrane is composed of an achiral polymer substrate and chiral guest molecules. The chiral guest molecules are pure enantiomers, and the chiral guest molecules account for 1 wt% to 7 wt% of the mass of the achiral polymer substrate. The chiral guest molecules are one of (R)-(+)-3-chloro-1-phenyl-1-propanol, (S)-(-)-3-chloro-1-phenyl-1-propanol, (R)-1-phenylethanol, and (S)-1-phenylethanol.

2. The chiral hydrogel electrolyte based on supramolecular assembly according to claim 1, characterized in that, The non-chiral polymer substrate is one or two of polyurethane acrylate, polyethylene glycol diacrylate, hydroxyethyl methacrylate, acrylamide, N-isopropylacrylamide, and polyvinyl alcohol.

3. The chiral hydrogel electrolyte based on supramolecular assembly according to claim 2, characterized in that, The non-chiral polymer substrate is a mixture of two polymer monomers in a mass ratio between 1:1 and 4:

1.

4. The chiral hydrogel electrolyte based on supramolecular assembly according to claim 1, characterized in that, The aqueous electrolyte is an aqueous zinc electrolyte, wherein the concentration of zinc salt is 0.5 mol / L to 3 mol / L.

5. The chiral hydrogel electrolyte based on supramolecular assembly according to claim 4, characterized in that, The zinc salt is one or more of zinc methanesulfonate, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonate)imide, zinc hexafluorophosphate, zinc perchlorate, and zinc nitrate.

6. The method for preparing a chiral hydrogel electrolyte based on supramolecular assembly according to claim 1, characterized in that, Includes the following steps: Step 1: Select a non-chiral polymer substrate precursor, add it to a solvent and stir to dissolve it, forming a non-chiral polymer substrate solution; Step 2: Add chiral guest molecules to the non-chiral polymer base solution, then add crosslinking initiator, and stir at 15℃~35℃ for 6 h~24 h under light-protected conditions to obtain gel prepolymer solution; Step 3: Inject the gel prepolymer into the mold, cure it under ultraviolet light, and then dry it to obtain a supramolecular chiral membrane; during the ultraviolet curing process, the wavelength of the ultraviolet lamp is 254 nm ~ 365 nm, and the irradiation time is 5 min ~ 60 min; during the drying process, the drying temperature is 60℃ ~ 90℃. Step 4: Immerse the supramolecular chiral membrane in an aqueous electrolyte solution until it swells and becomes saturated to obtain a chiral hydrogel electrolyte.

7. The method for preparing a chiral hydrogel electrolyte based on supramolecular assembly according to claim 6, characterized in that, In step 1, the solvent is one or more of anhydrous ethanol, methanol, anhydrous acetonitrile, N,N-methyleneformamide, acetone, and ethyl acetate.

8. The method for preparing a chiral hydrogel electrolyte based on supramolecular assembly according to claim 6, characterized in that, In step 2, the crosslinking initiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and the amount of crosslinking initiator added is 0.1 wt% to 0.5 wt% of the mass of the non-chiral polymer substrate.

9. The method for preparing a chiral hydrogel electrolyte based on supramolecular assembly according to claim 6, characterized in that, In step 3, the amount of gel prepolymer liquid injected into the mold is 50 μl to 500 μl.

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