Flexible zinc ion battery dual-network repairable gel electrolyte and preparation method and application thereof

Abstract

The invention discloses a double-network repairable gel electrolyte of a flexible zinc ion battery as well as a preparation method and application of the double-network repairable gel electrolyte. The gel electrolyte is prepared from polyacrylic acid (PAA), polyvinyl alcohol (PVA), zinc salt, water and a humectant. A first network is formed through dynamic coordination of PAA carboxyl and Zn < 2 + >, a second network is formed through hydrogen-bond interaction between PVA molecular chains, and the electrolyte is endowed with excellent mechanical strength and flexibility through the double networks. The preparation method comprises the following steps: dissolving and mixing PAA and PVA, adding a zinc salt solution to induce coordination, strengthening a hydrogen bond network through freezing-melting circulation, and finally swelling and activating in a zinc salt electrolyte. The gel electrolyte prepared by the invention has high ionic conductivity, rapid self-repairing capability and good interface stability, can effectively inhibit the growth of zinc dendrites, and is suitable for flexible aqueous zinc ion batteries and wearable energy storage devices.

Description

Technical Field

[0001] This invention belongs to the technical field of electrochemical energy storage materials and flexible energy devices, specifically relating to a flexible zinc-ion battery dual-network repairable gel electrolyte, its preparation method, and its applications. More specifically, it relates to a dual-network gel electrolyte based on a polyacrylic acid-zinc ion coordination network / polyvinyl alcohol hydrogen bonding network, which can be used in high-safety energy storage devices such as flexible aqueous zinc-ion batteries and flexible zinc-air batteries. Background Technology

[0002] With the rapid development of foldable smart devices, flexible sensors, and smart wearable equipment, energy storage units are required to simultaneously possess: bendable and stretchable mechanical properties, high ionic conductivity, high safety, stable electrochemical performance, good air stability, and resistance to water loss. Aqueous zinc-ion batteries have become an important candidate system for flexible energy storage due to their advantages such as safety, low cost, and environmental friendliness. However, to achieve truly wearable, bendable, and even stretchable structures, traditional liquid electrolytes can no longer meet the following requirements: liquid systems are prone to leakage and are not suitable for bendable structures; water evaporation leads to a decrease in conductivity and increased electrode polarization; they are difficult to withstand structural damage caused by external forces; the interface with zinc metal is unstable, easily accelerating dendrite growth and corrosion; mechanical damage is irreversible, leading to irreversible battery failure; and existing single-network gels struggle to balance flexibility and mechanical strength.

[0003] Current research on gel electrolytes mainly includes PVA gels, PAM gels, and natural polymer backbones, but they have the following shortcomings: simple network structure with limited load-bearing capacity; lack of dynamic reversible bonds, resulting in poor self-healing ability; insufficient moisture retention, making them prone to cracking upon exposure to air; and poor Zn... 2+ The poor coordination adaptability of zinc dendrites makes it impossible to suppress them. While dual-network gels have been used in recent years to improve the mechanical properties of flexible materials, common dual networks are mostly used in hydrogel sensors or impact-resistant materials; their systems cannot be directly used in electrolytes and lack specific targeting capabilities for Zn. 2+ The design of adaptability and electrochemical stability is crucial. For example, the report "A Self-Healing Integrated All-in-One Zinc-Ion Battery" describes a PVA-based self-healing electrolyte prepared through freeze-thaw cycling. Although a certain degree of physical self-healing is achieved by utilizing hydrogen bonding between PVA molecular chains, its network structure is simple, making it difficult to control the balance between mechanical strength and toughness. More importantly, the Zn content in this system... 2+It exists only as a migrating ion in the electrolyte and does not participate in the construction of the cross-linked network. Furthermore, its application scenarios are different. From the beginning, it has been designed for integrated battery devices. The PVA / Zn(TFSI)2 solution is a precursor coated on the electrode. During the preparation process, the electrode and electrolyte layers are cured simultaneously. The electrolyte is not designed as an independent material platform that can be used in a variety of zinc-based batteries; there is no limitation or expansion of the application scope of the electrolyte alone.

[0004] In addition, patent CN202310377755.2 discloses a PVA reference solid electrolyte and its preparation method and application. Although zinc salt and iodine salt are introduced, its system involves a strongly alkaline environment, which is extremely corrosive to the highly chemically active zinc anode. Moreover, this technology is also limited to the construction of a single PVA network and does not solve the problem of reconstructing the conductive channels after the gel breaks.

[0005] To enhance the mechanical strength of gels, existing technologies often employ chemical cross-linking strategies. For example, patent CN202510809690.3 discloses a multi-network hydrogel for flexible zinc-ion batteries, whose preparation process requires the introduction of an initiator (APS) and a chemical cross-linking agent (MBAA) to form an interpenetrating network of sodium polyacrylate and PVA through a chemical reaction. While this chemical cross-linking network significantly improves mechanical strength, the breaking of covalent bonds is usually irreversible. This means that once the material is mechanically damaged, its structural integrity and ion transport channels cannot be restored, leading to permanent battery failure. Furthermore, residual chemical initiators may introduce impurities, affecting the battery's electrochemical window and interfacial stability. In such technologies, zinc ions still only enter the gel as an electrolyte component through swelling, failing to realize their potential as structural cross-linking points.

[0006] In the aforementioned prior art, the construction of the gel framework and ion transport are usually independent. That is, the framework provides mechanical support, while the ionic liquid provides electrical conductivity. When the gel breaks, even with physical re-contact, the ion transport channels are difficult to rebuild effectively, resulting in a low recovery rate of ion conductivity after self-repair, which severely affects the cycling stability of the device.

[0007] Therefore, it is necessary to develop a method that combines high mechanical strength, good flexibility, stretchability, self-healing ability, and suitability for Zn. 2+ The electrochemical properties, high humidity stability, strong resistance to water loss, and dual-network gel electrolyte that inhibits zinc dendrite formation are key scientific issues and engineering challenges in the field of flexible zinc-ion batteries. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention proposes a flexible zinc-ion battery dual-network repairable gel electrolyte, its preparation method, and its applications. This gel electrolyte utilizes PAA-Zn... 2+The synergistic effect of the coordination network (first network) and the PVA hydrogen bond network (second network) constructs a dual-network structure, which not only has excellent mechanical properties, but also good ionic conductivity, air stability and self-healing ability, which can significantly improve the cycle life and mechanical damage resistance of flexible zinc-ion batteries.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A flexible zinc-ion battery dual-network repairable gel electrolyte is prepared from raw materials comprising: polyacrylic acid (PAA); polyvinyl alcohol (PVA); zinc salt; water; and optionally a humectant.

[0011] The gel electrolyte has a dual-network structure:

[0012] (1) A dual-network repairable gel electrolyte is provided, which utilizes Zn 2+ The dynamic coordination with PAA constructs a reversible network, enabling the gel electrolyte to have rapid self-repair capabilities.

[0013] (2) A preparation method is provided, which combines solution preparation, coordination induction and freeze-thaw crosslinking to construct a second hydrogen bond network of PVA, thereby obtaining a gel structure with high strength, flexibility and fatigue resistance.

[0014] The gel electrolyte is activated by swelling in a zinc-ion-containing electrolyte. This gel electrolyte is provided for applications in flexible zinc-ion batteries, including flexible Zn / Zn symmetric batteries, flexible Zn-MnO2 batteries, and flexible Zn-Air batteries.

[0015] A flexible zinc-ion battery dual-network repairable gel electrolyte is formed from the following components: 100 parts PAA; 10-60 parts PVA; zinc salt (in Zn) 2+ (by weight) 2-40 parts; humectant 0-30 parts; deionized water 200-800 parts. Among them: humectant improves the water retention and air stability of the system.

[0016] A method for preparing a dual-network gel electrolyte, comprising:

[0017] (1) Add PAA and PVA to water or a water-alcohol mixture and heat to dissolve them to obtain a homogeneous solution;

[0018] (2) Prepare an aqueous solution of zinc salt and slowly add it dropwise to the above mixed solution under stirring, so that Zn 2+ The first network was constructed by in-situ coordination with the PAA molecular chain to obtain a homogeneous precursor solution;

[0019] (3) Inject the precursor solution into the mold and perform 1 to 3 freeze-thaw cycles to promote the formation of PVA hydrogen bond network and prepare a double network gel.

[0020] (4) Place the gel in Zn 2+ Once the swelling reaches equilibrium in the electrolyte, a double-network gel electrolyte is obtained.

[0021] Furthermore, in step (1), as a preferred embodiment, the PAA is polyacrylic acid or an aqueous solution thereof, and the weight-average molecular weight of the PAA is 5 × 10⁻⁶. 4 ~1×10 6 (Preferred 1×10) 5 ~5×10 5 ).

[0022] As a preferred embodiment, the degree of polymerization of the PVA is 500-2500 (preferably 1500-2000), and the degree of hydrolysis is 80-99% (preferably 87-89%).

[0023] As preferred options, PAA and PVA are key raw materials for constructing the dual-network framework, and Zn 2+ It serves as the dynamic crosslinking center of the first network; when PAA or Zn is lacking. 2+ During the coordination process, the self-healing conductivity recovery ability of the gel decreased significantly (see Comparative Example 3 for details).

[0024] Furthermore, in step (1), the heating and stirring temperature is 60-95 ℃ (preferably 75-90 ℃), and the stirring time is 0.5-2 h until the solution is clear and homogeneous.

[0025] Furthermore, in step (2), as a preferred embodiment, the zinc salt is a water-soluble divalent zinc salt, including but not limited to ZnSO4·7H2O, Zn(CH3COO)2·2H2O, ZnCl2, Zn(NO3)2, Zn(CF3SO3)2 [i.e., Zn(TFSI)2 or Zn(OTf)2 systems that can provide Zn] 2+ One or more of the following salts: ZnSO4·7H2O or Zn(CH3COO)2·2H2O.

[0026] Furthermore, the humectant is an optional additive component used to improve the gel's water retention, flexibility, and long-term stability under ambient or low-humidity conditions. Even without the addition of a humectant, the gel can still form a stable dual-network structure and achieve ion conduction and self-repair functions. In some embodiments, the humectant is selected from one or more of glycerin, urea, sorbitol, polyethylene glycol (PEG200-PEG2000), or ionic liquids, and its addition amount is 0-30 wt% (preferably 5-20 wt%) of the total gel mass.

[0027] Preferably, PAA:PVA:Zn 2+ =100:(20~50):(5~25).

[0028] Preferably, after adding zinc salt solution during the coordination induction stage, the Zn in the precursor system... 2+ The concentration is 0.2–2.0 mol / L (preferably 0.5–1.5 mol / L); the Zn²⁺ concentration in the electrolyte during the swelling and activation stage is 1–3 mol / L (preferably 1.5–2.0 mol / L).

[0029] Preferably, the humectant is selected from one or more of glycerin, urea, sorbitol, polyethylene glycol (PEG200-PEG2000) or ionic liquid, and the amount added is 2-30 wt% (preferably 5-20 wt%) of the total mass of the gel.

[0030] Furthermore, in step (3), during the freeze-thaw cycle, the freezing temperature is −10 to −30 °C (preferably −18 to −20 °C), and the freezing time is 8 to 24 h; the melting temperature is 20 to 30 °C, and the melting time is 8 to 24 h; the number of cycles is 1 to 3. By inducing the formation of microcrystalline domains and hydrogen bond rearrangement in PVA through freezing, the second network is enhanced and the fracture toughness is improved.

[0031] Furthermore, in step (4), the swelling activation uses a Zn-containing... 2+ Aqueous electrolyte, Zn 2+ The concentration is 1–3 mol / L (preferably 1.5–2.0 mol / L), the swelling time is 2–24 h (preferably 8–12 h), and the temperature is 20–30 ℃. After swelling, the gel reaches a stable ion-conducting state.

[0032] Applications of a dual-network gel electrolyte include, but are not limited to: flexible Zn / Zn symmetric batteries; flexible Zn-MnO2 batteries; flexible Zn-Air batteries; wearable electronic devices under bending, twisting, and deformation conditions; and energy units for smart skin power supplies and flexible stress sensors.

[0033] The beneficial effects of this invention are:

[0034] (1) The flexible zinc-ion battery dual-network repairable gel electrolyte prepared in this invention has self-healing ability, which is due to PAA-Zn 2+ Due to the dynamic coordination and PVA hydrogen bond reconstruction, the gel can self-heal within 30–300 seconds after mechanical cutting, restoring 70–90% of its conductivity.

[0035] (2) The flexible zinc-ion battery prepared by the present invention has excellent flexibility and mechanical properties of the dual-network repairable gel electrolyte. The dual-network structure improves the tensile properties and fracture strength of the gel, and can stably withstand external forces such as bending, stretching and compression.

[0036] (3) The flexible zinc-ion battery dual-network repairable gel electrolyte prepared by the present invention has high ionic conductivity. Under the synergistic effect of dual networks and swelling activation, it can achieve a high conductivity of 1 to 10 mS / cm.

[0037] (4) The flexible zinc-ion battery dual-network repairable gel electrolyte prepared by this invention can effectively inhibit zinc dendrite growth, and the network structure is similar to that of Zn. 2+ Uniform distribution can improve the negative electrode interface and extend cycle life.

[0038] (5) The flexible zinc-ion battery dual-network repairable gel electrolyte prepared by the present invention enhances air stability. The moisturizer and network structure enable the gel to maintain a high water content under air exposure conditions, thus avoiding cracking and failure.

[0039] (6) The flexible zinc-ion battery dual-network repairable gel electrolyte prepared by the present invention has a simple preparation process, can be scaled up, adopts a controllable physical cross-linking process, and is mild, safe and reliable, which is convenient for industrial scale-up. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0041] Figure 1 Pure PAA gel, PAA / PVA gel, and PAA / PVA-Zn 2+ FTIR characterization test images of three sets of samples.

[0042] Figure 2 This refers to the gel electrolyte severance and self-repair process described in this invention.

[0043] Figure 3 The stress-strain curve of the dual-network gel electrolyte prepared in Example 1 of this invention is shown.

[0044] Figure 4 This is a comparison chart of the ionic conductivity of the dual-network gel electrolyte prepared in Example 1 of the present invention.

[0045] Figure 5 The tensile stress-strain curve of the gel prepared in Example 2 is shown.

[0046] Figure 6 This is a comparison chart of the ionic conductivity of the dual-network gel electrolyte prepared in Example 2 of the present invention.

[0047] Figure 7 This is a comparison chart of gel mass loss rates in Example 1 (without glycerin) and Example 3 (with glycerin).

[0048] Figure 8 The graph shows the effect of the number of freeze-thaw cycles on the mechanical properties of the gel.

[0049] Figure 9 The effect of freeze-thaw cycles on the cycle performance of Zn / Zn symmetric cells is shown in the figure.

[0050] Figure 10 This is a stability test diagram for Zn / Zn symmetric cells. Detailed Implementation

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0052] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0053] Without departing from the spirit and essence of this invention, those skilled in the art can make various changes or equivalent substitutions to the following embodiments, and all such changes or substitutions should fall within the protection scope of this invention. Unless otherwise stated, the raw materials used in the embodiments are all commercially available conventional reagents, and the water used is deionized water. Specifically, PAA can be a commercially available aqueous solution of polyacrylic acid (e.g., solid content 30-40 wt%); PVA can be a commercially available polyvinyl alcohol (e.g., degree of polymerization 1700-1800, degree of alcoholysis 87-89%); and zinc salts can be analytical grade or battery-grade reagents. The above raw material models are merely examples and are not intended to limit the protection scope of this invention.

[0054] Example 1

[0055] This embodiment provides a method for preparing a flexible zinc-ion battery dual-network repairable gel electrolyte. The gel electrolyte preparation process of this invention includes four steps: solution preparation, coordination induction, freeze-thaw cycle, and swelling activation. Specifically:

[0056] Based on a PAA solid content of 100 parts, the ingredients are: PAA: 100 parts, PVA: 30 parts, moisturizer: 0 parts, zinc salt (as Zn) 2+26 samples of deionized water and 800 samples of deionized water.

[0057] (1) Weigh 1.0 g of polyacrylic acid (PAA, based on solid content; the PAA used is an aqueous solution with a mass fraction of approximately 35 wt%, so approximately 2.86 g of this aqueous solution is actually weighed) and 0.30 g of polyvinyl alcohol (PVA, degree of alcoholysis 87-89%, degree of polymerization 1700-1800), add 8.0 g of deionized water, and magnetically stir in an 80 ℃ water bath for 1 h until a homogeneous and transparent solution A is obtained. Cool to room temperature for later use. It should be noted that the polyacrylic acid aqueous solution is weakly acidic in the initial state. In subsequent steps, Zn is introduced... 2+ Zn 2+ It can coordinate with the carboxyl groups on the PAA molecular chain, thereby effectively reducing the acidity of free carboxyl groups in the system. This coordination process itself plays an in-situ regulatory role, and the present invention can achieve stable gel structure construction and ion conduction performance without the need for the addition of an alkaline neutralizing agent.

[0058] (2) Take 2.0 mL of 2 mol / L ZnSO4·7H2O aqueous solution and slowly add it dropwise to solution A under stirring. Continue stirring for 20 min to obtain a slightly viscous solution B. During this process, Zn 2+ It dynamically coordinates with the carboxyl group of the PAA chain segment, initially forming the first reversible coordination network.

[0059] (3) Pour solution B into a flat mold and seal it. Freeze it in a -20 ℃ refrigerator for 12 h. Then take it out and let it thaw naturally at room temperature (25±2 ℃, relative humidity 50±10%) for 12 h to complete one freeze-thaw cycle. Through this process, PVA segments form microcrystalline domains and interact with hydrogen bonds to construct a second physical cross-linked network, resulting in a double-network gel C.

[0060] (4) Take the double-network gel C out of the mold, cut it into sheets with a thickness of about 1.0 mm, immerse it in 2 mol / L ZnSO4 aqueous solution, and swell at room temperature (25±2 ℃) for 12 h to obtain the flexible zinc-ion battery double-network repairable gel electrolyte of Example 1.

[0061] The obtained gel was completely cut along the middle and immediately aligned for contact. It was then allowed to stand at room temperature (25±2 ℃, relative humidity 50±10%) for repair. After approximately 60 seconds, the sample could be lifted as a whole. After 10 minutes of repair, the gel's ionic conductivity recovered to approximately 80% of its initial value (see...). Figure 2 Initial σ0 = 10.6 mS·cm -1 This indicates that the gel has good room temperature self-healing ability.

[0062] Mechanical and electrochemical performance testing and methods:

[0063] (1) Mechanical properties: Uniaxial tensile tests were performed on the gel using an electronic universal testing machine at a tensile rate of 10 mm / min, and stress-strain curves were obtained (see Figure 3 (In this embodiment, the tensile strength of the gel is 0.5 MPa, and the elongation at break is 210%).

[0064] (2) Ionic conductivity: The electrochemical impedance spectroscopy (EIS) method was used for testing. The gel was cut into circular pieces with a thickness of L≈1.0 mm, clamped between two stainless steel blocking electrodes, and subjected to EIS testing on an electrochemical workstation. The frequency range was 1 MHz to 0.1 Hz, and the perturbation voltage was 5 to 10 mV. The bulk resistance R was obtained from the high-frequency intercept, and the ionic conductivity was calculated using σ = L / (R·S). In this embodiment, the initial ionic conductivity of the gel was σ0 = 10.6 mS·cm. -1 The conductivity after 10 minutes of self-healing is σ1≈7.4 mS·cm -1 (See Figure 4 ).

[0065] To verify Zn 2+ Whether it coordinates with the carboxyl groups on the PAA molecular chain affects pure PAA gel, PAA / PVA gel, and PAA / PVA-Zn gel. 2+ FTIR testing was performed on a dual-network gel, such as... Figure 1 As shown. Without the introduction of Zn 2+ In PAA / PVA gels, the asymmetric stretching vibration peak (–COO⁻) of the PAA carboxyl group is located at approximately 1710–1725 cm⁻¹. -1 ; Introducing Zn 2+ Subsequently, the characteristic peak shifted significantly towards lower wavenumbers to approximately 1680–1700 cm⁻¹. -1 Simultaneously, the peak shape broadens; the above redshift and broadening phenomena indicate that the carboxyl groups on the PAA molecular chain react with Zn. 2+ Coordination interactions occurred between them, leading to a decrease in the carboxyl bond energy, proving that Zn 2+ It participates in the construction of the first dynamic coordination network, rather than simply existing as a freely migrating ion. Unlike traditional physical mixing or post-soaking, this invention allows Zn to participate in the construction of the first dynamic coordination network before gelation. 2+ It occupies the carboxyl site of PAA, which is key to achieving a high self-repair rate.

[0066] Example 2

[0067] This embodiment investigates the effect of varying PAA / PVA mass ratio on the mechanical properties and self-healing electrical conductivity of a dual-network gel. In this embodiment, adjusting the PAA / PVA mass ratio is the primary variable, used to control the gel's flexibility and extensibility; increasing the number of freeze-thaw cycles is used as an auxiliary condition to ensure the full formation of the dual-network structure, and its effect on mechanical properties is relatively minor. The preparation steps are basically the same as in Example 1, except for the mass ratio of PAA to PVA, the zinc salt concentration, and the freeze-thaw conditions, as detailed below:

[0068] Based on a PAA solid content of 100 parts, the ingredients are: PAA: 100 parts, PVA: 50 parts, moisturizer: 0 parts, zinc salt (as Zn) 2+ 29 samples of deionized water and 750 samples of deionized water.

[0069] Weigh out 1.0 g of polyacrylic acid (PAA, based on solid content) and 0.50 g of polyvinyl alcohol (PVA, degree of alcoholysis 87-89%, degree of polymerization 1700-1800), add 7.5 g of deionized water, and stir to dissolve at 80 °C for 1 h to obtain a homogeneous and transparent solution A′.

[0070] Prepare a 1.5 mol / L ZnSO4 aqueous solution. Slowly add 3.0 mL of the solution to solution A′ and continue stirring for 30 min to allow the ZnSO4 to settle. 2+ It coordinates with PAA segments to form a precursor solution;

[0071] The obtained solution was poured into a mold and subjected to two freeze-thaw cycles of freezing at −18 to −20 °C for 10 h and thawing at room temperature (25±2 °C) for 10 h to enhance the formation of PVA hydrogen bond network and obtain a double network gel.

[0072] The gel was placed in a 1.5 mol / L ZnSO4 aqueous solution and swollen at room temperature for 8 h to obtain the flexible zinc-ion battery dual-network repairable gel electrolyte of Example 2.

[0073] Mechanical property testing: Uniaxial tensile testing was performed on the gel using an electronic universal testing machine (tensile rate 10 mm / min). The results are shown in (see...). Figure 5In this embodiment, the gel exhibits a tensile strength of approximately 0.58 MPa and an elongation at break of approximately 260%, demonstrating superior extensibility compared to Example 1. Comparing this to the results of Example 4, it can be seen that increasing the number of freeze-thaw cycles primarily enhances the rigidity and modulus of the gel. In this embodiment, the increased PVA content significantly enhances the number of reversible hydrogen bonds and the chain segment slippage ability within the network, with its flexibility effect playing a dominant role, thereby improving the overall extensibility of the gel. Therefore, the results of this embodiment indicate that, under the premise of reasonable control of freeze-thaw conditions, appropriately increasing the PVA ratio is beneficial for enhancing the flexibility and tensile strength of the dual-network gel.

[0074] Ionic conductivity and self-healing properties: The ionic conductivity of the gel was tested using AC impedance spectroscopy. In this example, the initial ionic conductivity of the gel was σ0 ≈ 10.4 mS·cm. -1 After complete disconnection and re-contact repair at room temperature for 10 minutes, its conductivity can recover to approximately 75% of its initial value (see [link to original text]). Figure 6 This indicates that while improving flexibility, the gel still maintains good ion transport capacity and self-healing conductivity.

[0075] Example 3

[0076] Based on Example 1, glycerin was introduced as a humectant to improve the water retention and air stability of the gel. The preparation method is as follows:

[0077] Based on a PAA solid content of 100 parts, the ingredients are: PAA: 100 parts, PVA: 30 parts, moisturizer: 50 parts, zinc salt (as Zn) 2+ 26 portions of total, and 700 portions of deionized water.

[0078] Weigh 1.0 g of polyacrylic acid (PAA, calculated solids content), 0.30 g of polyvinyl alcohol (PVA, degree of polymerization 1700-1800) and 0.50 g of glycerol, add 7.0 g of deionized water, and stir magnetically at 80 ℃ for 1 h to obtain a uniform and transparent solution A1.

[0079] Slowly add 2.0 mL of 2 mol / L ZnSO4 aqueous solution to solution A1, continue stirring for 20 min, and then pour the resulting solution into a flat mold.

[0080] The mold was frozen at −20 ℃ for 12 h, and then removed and allowed to thaw naturally at room temperature (25 ℃) for 12 h to complete one freeze-thaw cycle, yielding gel B1.

[0081] Gel B1 was removed and cut into sheet-like samples with a thickness of about 1.0 mm. The samples were then immersed in a 2 mol / L ZnSO4 aqueous solution to swell for 12 h, resulting in the flexible zinc-ion battery dual-network repairable gel electrolyte of Example 3.

[0082] To evaluate the effect of glycerol introduction on the air stability of the gel, the gel samples prepared in Example 3 and Example 1 were subjected to air exposure tests under the same conditions: ambient temperature 25±2 ℃; relative humidity 50±5%; exposure time 7 days. The initial mass m0 and the mass m7 after 7 days of exposure were recorded, and the mass loss rate was calculated using the following formula:

[0084] Test results (see) Figure 7 The results showed that the gel of Example 1 (without glycerin) had a mass loss rate of approximately 25% to 30% after 7 days of air exposure; the gel of Example 3 (with glycerin) had a mass loss rate reduced to ≤15% under the same conditions.

[0085] Example 4

[0086] This embodiment investigates the effect of freeze-thaw cycles on the network structure, mechanical properties, and interface stability of the dual-network gel electrolyte. The specific preparation process is as follows:

[0087] Based on a PAA solid content of 100 parts, the ingredients are: PAA: 100 parts, PVA: 30 parts, moisturizer: 0 parts, zinc salt (as Zn) 2+ 26 samples of deionized water and 800 samples of deionized water.

[0088] Weigh 1.0 g of polyacrylic acid (PAA, by solids content) and 0.30 g of polyvinyl alcohol (PVA), add them to 8.0 g of deionized water, and stir in an 80 ℃ water bath for 1 h to obtain a homogeneous and transparent solution A. Then add 2.0 mL of a 2 mol / L ZnSO4 aqueous solution to solution A, and continue stirring for 20 min to allow the Zn... 2+ It coordinates with the carboxyl group of PAA.

[0089] The obtained solution was poured into a mold and subjected to different numbers of freeze-thaw cycles. Freezing conditions: −20 ℃, 8 h; Melting conditions: room temperature (approximately 25 ℃), 8 h. The three freeze-thaw cycles were repeated three times under the above conditions to obtain gel B2.

[0090] Gel B2 was placed in a 2 mol / L ZnSO4 solution and swollen for 10 h to obtain the dual-network gel electrolyte described in this embodiment.

[0091] Mechanical property testing and result analysis: Uniaxial tensile tests (tensile rate 10 mm / min) were conducted on gels with different freeze-thaw cycles using an electronic universal testing machine. The results show (see...) Figure 8 As the number of freeze-thaw cycles increased from 1 to 3, the Young's modulus of the gel increased from approximately 0.18 MPa to approximately 0.30 MPa, and the tensile strength increased from approximately 0.42 MPa to approximately 0.55 MPa. The results indicate that increasing the number of freeze-thaw cycles promotes the further formation of hydrogen-bonded microcrystalline regions between PVA segments, making the second network more compact and significantly improving the overall rigidity and load-bearing capacity of the gel, but at the expense of some degree of ductility.

[0092] Performance comparison of Zn / Zn symmetric cells (see) Figure 9 Zn / Zn symmetric cells were assembled using samples that underwent a single freeze-thaw cycle and samples that underwent a triple freeze-thaw cycle as electrolytes, and compared under the same test conditions: current density 0.5 mA·cm⁻¹. -2 The test temperature was approximately 25 °C; the zinc plating / stripping method was constant current mode. Test results showed that the Zn / Zn symmetric cells of the single-freeze-thaw sample exhibited a significant increase in polarization voltage after approximately 250 h; the Zn / Zn symmetric cells of the triple-freeze-thaw sample could cycle stably for over 325 h, with the polarization voltage remaining within the range of approximately 60–80 mV and exhibiting minimal fluctuations.

[0093] Example 5

[0094] This embodiment is mainly used to verify the stability of the dual-network repairable gel electrolyte of the present invention at the zinc metal anode interface and its ability to regulate zinc deposition / stripping behavior. The specific steps are as follows:

[0095] The dual-network repairable gel electrolyte prepared in Example 3 was selected and cut into circular pieces with a diameter of 16 mm and a thickness of about 1.0 mm as electrolyte separators.

[0096] Commercially pure zinc foil (purity ≥99.9%) was cut into circular pieces of the same size as the gel, which served as the positive and negative electrodes of the symmetrical battery. The Zn sheet / gel electrolyte / Zn sheet were stacked in sequence and assembled into a coin cell case to obtain a Zn / Zn symmetrical battery.

[0097] Zinc plating / stripping test conditions: The assembled Zn / Zn symmetric cells were subjected to constant current zinc plating / stripping tests on an electrochemical workstation. Specific conditions were as follows: current density 0.5 mA·cm⁻¹ -2 The test temperature was 25 ℃ (room temperature); the plating / stripping method was constant current mode, with equal plating / stripping amounts; the test environment was normal pressure air environment. Test results (see...) Figure 10Under the above conditions, the Zn / Zn symmetric cell using the dual-network gel electrolyte of this invention can cycle stably for over 350 hours without any short circuits during the entire test. During long-term cycling, the polarization voltage of this symmetric cell remains consistently within the range of approximately 30–40 mV with minimal fluctuations, and no significant increase with cycling time was observed. These results demonstrate that the gel electrolyte of this invention can maintain stable ion transport channels at the zinc anode interface, which facilitates uniform zinc deposition and stripping processes, thereby effectively reducing interfacial polarization and delaying the risk of dendrite-induced failure.

[0098] Example 6

[0099] This embodiment is mainly used to verify the feasibility of applying the dual-network repairable gel electrolyte of the present invention in flexible full-cell devices, and focuses on examining its electrochemical stability under different bending states.

[0100] Positive electrode and battery assembly: γ-MnO2 powder, conductive carbon black, and polyvinylidene fluoride (PVDF) are mixed at a mass ratio of 7:2:1, and N-methylpyrrolidone (NMP) is used as a solvent to prepare a uniform slurry. The slurry is uniformly coated on the surface of a carbon cloth current collector, vacuum dried at 60 °C, and then pressed into a sheet to obtain a flexible MnO2 positive electrode sheet.

[0101] The dual-network repairable gel electrolyte prepared in Example 1 was selected, cut into thin slices matching the electrode size, and placed between the zinc foil negative electrode and the MnO2 / carbon cloth positive electrode.

[0102] A flexible Zn–MnO2 battery was fabricated by using a flexible plastic film as the encapsulation substrate, heat-sealing the battery, and leading out electrode leads.

[0103] The assembled flexible Zn–MnO2 battery was subjected to constant current charge-discharge testing on an electrochemical workstation under the following conditions: charge-discharge rate: 1 C (based on the theoretical capacity of the MnO2 positive electrode active material); test temperature: 25 ℃ (room temperature); test environment: ambient air pressure; bending states: straight, static 90° bend, and static 180° bend. In each bending state, a fixed bending angle was maintained, and multiple cycles of constant current charge-discharge testing were performed.

[0104] Test Results and Analysis: Under flat conditions, the initial discharge capacity of this flexible battery is approximately 280 mAh·g. -1 It can still maintain approximately 252 mAh·g after 200 cycles. -1 The capacity retention rate is approximately 90%, demonstrating good cycle stability. When tested under a 90° bend, its initial discharge capacity is approximately 275 mAh·g. -1 After 200 cycles, the capacity remained at approximately 245 mAh·g.-1 The capacity retention rate was approximately 89%. Compared to the flat state, the capacity decay rate did not show a significant acceleration. Further cycle testing with the battery bent at 180° revealed an initial discharge capacity of approximately 270 mAh·g. -1 It can still maintain approximately 238 mAh·g after 200 cycles. -1 The capacity retention rate was approximately 88%. Throughout the entire cycle, the battery did not exhibit any abnormal capacity drop or failure. Even at large bending angles, the dual-network repairable gel electrolyte of this invention maintained continuous and stable ion transport channels and good electrode / electrolyte interface contact, enabling the flexible Zn-MnO2 battery to maintain excellent cycle stability under mechanical bending disturbances.

[0105] Table 1:

[0106] Bending state <![CDATA[Initial discharge capacity (mAh·g -1 )]]> <![CDATA[Capacity after 200 cycles (mAh·g -1 )]]> Capacity retention flat ≈280 ≈252 ≈90% Bending 90° ≈ 275 ≈245 ≈89% Bending 180° ≈270 ≈238 ≈88%

[0107] Comparative Example 1:

[0108] A single-network gel containing only PVA was prepared for comparison.

[0109] The ingredients are: PAA: 0 parts, PVA: 30 parts, moisturizer: 0 parts, zinc salt (as Zn) 2+ 0 portions of deionized water and 800 portions of deionized water.

[0110] The preparation method is as follows: without adding PAA, weigh out 0.30 g PVA, add 8.0 g of deionized water, stir at 80 ℃ for 1 h, without adding zinc salt, freeze at -20 ℃ for 12 h / thaw at room temperature for 12 h, repeat once, and then soak in 2 mol / L ZnSO4 solution for 12 h.

[0111] The test performance comparison results are as follows: tensile strength ≈ 0.25 MPa; elongation at break ≈ 220%; initial ionic conductivity ≈ 3.0 mS·cm -1 The conductivity recovery rate after 10 minutes of cutting is less than 30%; the sample cannot be lifted as a whole after multiple cuts.

[0112] The results show that the single-network PVA gel relies solely on physical cross-linking via hydrogen bonds. After mechanical breakage, the network is difficult to reconstruct effectively, and the ion transport channels cannot be continuously restored, exhibiting significantly inferior self-healing conductivity compared to the dual-network gel of this invention.

[0113] Comparative Example 2:

[0114] Chemically cross-linked PAA / PVA gels were prepared for comparison. Based on the formulation of Example 1, APS (0.1 wt%) and MBAA (0.05 wt%) were added, and the mixture was heated at 60 °C for 2 h to form a covalently cross-linked network. The freeze-thaw step was not performed, resulting in the Comparative Example 2 sample.

[0115] (1) Weigh 1.0 g of polyacrylic acid (PAA, based on solid content) and 0.30 g of polyvinyl alcohol (PVA), add them to 8.0 g of deionized water, and stir for 1 h in a water bath at 80 ℃ to obtain a homogeneous and transparent solution;

[0116] (2) Add the initiator ammonium persulfate (APS, added at 0.1 wt% of the total mass of monomer / polymer) and the chemical crosslinking agent N,N'-methylenebisacrylamide (MBAA, added at 0.05 wt%) to the above solution, and 2.0 mL of 2 mol / L ZnSO4 aqueous solution. Stir well and then pour into the mold.

[0117] (3) Place the mold in a 60 ℃ oven and heat for 2 h to allow the system to undergo a chemical cross-linking reaction to form a covalent network;

[0118] (4) After the reaction is complete, the gel is removed and without freezing-thawing, it is immersed in 2 mol / L ZnSO4 solution for 2 h to equilibrate, thus obtaining the chemically cross-linked gel electrolyte described in Comparative Example 2.

[0119] index Example 1 (Physical Dual Network) Comparative Example 2 (Chemical Crosslinking) Tensile strength ≈0.45 MPa ≈0.45 MPa Self-repair after severance Within 60 seconds Unrecoverable conductivity recovery rate 70–90% <10% Repeated cut Multiple times One failure

[0120] The performance results are shown in Table 2. The results indicate that the covalent network formed by chemical cross-linking cannot undergo structural reconstruction after breakage, resulting in a permanent interruption of the conductive channels. In contrast, the dual-network system based on dynamic coordination and hydrogen bond reconstruction of this invention achieves simultaneous self-repair of conductivity and structure while ensuring mechanical properties, demonstrating irreplaceable technical advantages.

[0121] Comparative Example 3

[0122] Preparation of non-in-situ coordinated Zn 2+ The gels were compared. The preparation method followed the steps of Example 1, but without the addition of zinc salt. First, a gel was formed by PAA / PVA + freeze-thaw; then, the gel was soaked in a 2 mol / L ZnSO4 solution for 24 h.

[0123] (1) Weigh 1.0 g of polyacrylic acid (PAA, based on solid content) and 0.30 g of polyvinyl alcohol (PVA), add them to 8.0 g of deionized water, and stir for 1 h in a water bath at 80 ℃ to obtain a homogeneous and transparent solution;

[0124] (2) Without adding zinc salt solution, pour the above mixed solution directly into the mold;

[0125] (3) Freeze the mold at -20 ℃ for 12 h, then thaw it at room temperature for 12 h, and perform one freeze-thaw cycle to form a single PVA physical gel skeleton;

[0126] (4) Take out the prepared gel and soak it in 2 mol / L ZnSO4 solution to swell for 24 h, so that Zn²⁺ enters the gel through diffusion, and obtain the gel electrolyte described in Comparative Example 3.

[0127] Test comparison results show that due to the lack of Zn 2+ Due to in-situ coordination with the PAA carboxyl group, the mechanical strength of the gel is lower than that of Example 1. Initial conductivity ≈ 5.0 mS·cm -1 ;

[0128] After cutting: When the gel was cut and re-contacted, the gel fracture surface showed only weak surface adhesion. After standing for 10 minutes, the sample easily broke again at the cut when lifted, unable to withstand its own weight; the conductivity recovery rate (10 minutes) was ≈40-45%. This proves that although the sample in Comparative Example 3 adsorbed Zn later... 2+ It can increase ion concentration, but it does not participate in the construction of the gel backbone and cannot form a Zn-based gel. 2+ This is a dynamic coordination network of crosslinking points. Therefore, this system is significantly inferior to the present invention in terms of structural reconstruction and conductive channel recovery, demonstrating that Zn... 2+ In-situ coordination during the gelation stage is key to achieving self-healing conductivity.

[0129] In summary, this invention provides a flexible zinc-ion battery dual-network repairable gel electrolyte, its preparation method, and its application. The preparation process of this invention is mild and simple, the process is controllable, the raw materials are widely available, and it is suitable for large-scale production. It effectively solves the technical bottlenecks of existing flexible electrolytes, such as poor mechanical properties, weak self-healing ability, insufficient interface stability, and difficulty in being applied to high-safety zinc-based energy storage devices.

[0130] PAA-Zn prepared by this invention 2+ The dual-network structure of coordination network / PVA hydrogen bond network endows the gel electrolyte with high mechanical strength, excellent flexibility, and rapid self-healing ability, significantly improving the stable operation of flexible batteries under complex conditions such as bending, stretching, and cutting. Through Zn... 2+ Through dynamic coordination with PAA carboxyl groups and hydrogen bond recombination of PVA segments, the gel of this invention exhibits rapid self-healing properties at room temperature. After self-healing, the conductivity can be restored to 70% to 90% of the original value, effectively extending the service life of flexible devices.

[0131] The gel electrolyte of this invention, after swelling and activation, exhibits high ionic conductivity and continuous, uniform ion migration channels, which significantly improves the nucleation and deposition behavior on the zinc anode surface, thereby inhibiting zinc dendrite growth and enhancing the cycle stability of Zn / Zn symmetric batteries. In some embodiments, the introduction of functional components such as glycerol further enhances the gel's moisture retention, electrochemical stability, and resistance to interfacial polarization, enabling it to demonstrate excellent steady-state discharge characteristics and bending tolerance in various types of zinc-based batteries, including flexible Zn-MnO2 and Zn-Air batteries.

[0132] The flexible zinc-ion battery assembled with the dual-network repairable gel electrolyte prepared by this invention exhibits high open-circuit voltage, excellent charge-discharge cycle stability, and good bending adaptability under various working stresses, and has high application prospects and practical value.

[0133] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art can make various equivalent substitutions or improvements without departing from the spirit and substance of the present invention, and such substitutions or improvements should all fall within the protection scope of the claims of the present invention.

Claims

1. A flexible zinc-ion battery dual-network repairable gel electrolyte, characterized in that, The gel electrolyte is prepared from raw materials comprising the following components: polyacrylic acid (PAA), polyvinyl alcohol (PVA), zinc salt, and water; The raw material composition of the gel electrolyte is as follows, based on parts by weight: PAA: 100 copies; PVA: 10-60 parts; Zinc salts, with Zn 2+ Mass meter: 2-40 parts; Moisturizer: 0-30 parts; Deionized water: 200-800 parts; The gel electrolyte has a dual-network structure, wherein: PAA and Zn 2+ The PVA molecules form a first reversible coordination network through coordination interactions; the PVA molecular chains form a second physical cross-linking network through hydrogen bonding; and the gel electrolyte is activated by swelling in an electrolyte containing zinc ions.

2. The flexible zinc-ion battery dual-network repairable gel electrolyte according to claim 1, characterized in that, The weight-average molecular weight of the PAA is 5 × 10⁻⁶. 4 ~1×10 6 The degree of polymerization of the PVA is 500-2500, and the degree of hydrolysis is 80-99%; the zinc salt is selected from one or more of zinc sulfate, zinc acetate, zinc chloride, zinc nitrate, and zinc trifluoromethanesulfonate.

3. The flexible zinc-ion battery dual-network repairable gel electrolyte according to claim 1, characterized in that, The humectant is selected from one or more of glycerin, urea, sorbitol, polyethylene glycol or ionic liquid; when the humectant is added, the amount added is 2 to 30 wt% of the total mass of the gel.

4. A method for preparing the flexible zinc-ion battery dual-network repairable gel electrolyte according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Add PAA and PVA to a solvent and dissolve them under heating and stirring conditions to obtain a mixed solution; (2) Add zinc salt solution to the mixed solution in step (1) and stir to allow Zn to form a solution. 2+ It coordinates with the PAA molecular chain to obtain a precursor solution; (3) Place the precursor solution in a mold and perform at least one freeze-thaw cycle to form a double network gel; (4) Immerse the gel obtained in step (3) in a Zn-containing solution. 2+ The electrolyte is swollen and mixed to obtain the dual-network repairable gel electrolyte.

5. The preparation method according to claim 4, characterized in that, The heating temperature in step (1) is 60-95℃.

6. The preparation method according to claim 4, characterized in that, After adding zinc salt solution in step (2), the Zn in the system 2 + The concentration is 0.2–2.0 mol / L.

7. The preparation method according to claim 4, characterized in that, The specific conditions for the freeze-thaw cycle in step (3) are: freezing at -10 to -30 °C for 8 to 24 h, followed by thawing at 20 to 30 °C for 8 to 24 h; the number of cycles is 1 to 3.

8. The preparation method according to claim 4, characterized in that, The Zn-containing component mentioned in step (4) 2+ Zn in electrolyte 2+ The concentration is 1–3 mol / L, and the swelling time is 2–24 h.

9. The application of the flexible zinc-ion battery dual-network repairable gel electrolyte according to any one of claims 1-3 in flexible electrochemical energy storage devices.

10. The application according to claim 9, characterized in that, The flexible electrochemical energy storage device includes a flexible zinc-ion battery, a flexible zinc-air battery, or a flexible zinc-manganese dioxide battery. Or flexible Zn / Zn symmetric cells.

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