High-modulus leather / eutectic gel composite electrolyte and preparation method and application thereof

Abstract

The invention discloses a high-modulus leather / eutectic gel composite electrolyte and a preparation method and application thereof, and belongs to the technical field of energy storage. The preparation method comprises the following steps: 1) preparing a eutectic gel solution containing polyvinyl alcohol, zinc salt, small molecular polyol and water; 2) carrying out vacuum impregnation to obtain leather fibers containing a eutectic gel solution; and (3) obtaining the leather / eutectic gel composite electrolyte with the imitated reinforcing steel bar-concrete structure through freeze-thaw circulation.The composite electrolyte effectively solves the problem that an existing gel electrolyte is low in modulus and difficult to effectively deal with extreme mechanical deformation, and the cycle life of the water-based zinc ion battery is remarkably prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy storage, and particularly relates to a high-modulus leather / eutectic gel composite electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Aqueous zinc-ion batteries have the characteristics of high safety, low cost, and ecological friendliness, and show great application value and research significance in large-scale energy storage. Zinc anode exhibits good electrochemical reversibility and high theoretical capacity in aqueous electrolyte, and is an ideal electrode material. However, the zinc anode has side reactions such as dendrite, hydrogen evolution, corrosion and passivation, which limit the performance and life of the battery. In particular, zinc dendrites can cause the cycle capacity of the battery to decrease, the cycle life to be shortened, and even cause the battery to short circuit, which seriously hinders the commercialization process of aqueous zinc-ion batteries.

[0003] Gel electrolyte has the advantages of both liquid and solid electrolytes, which can provide excellent ion conductivity and mechanical flexibility, and has significant advantages in inhibiting side reactions such as dendrite growth, hydrogen evolution and corrosion. Therefore, it has attracted widespread attention in aqueous zinc-ion batteries. The interaction between zinc ions and functional groups in gel electrolyte can adjust the solvation structure of zinc ions and induce uniform deposition of zinc ions. However, the inherent high water content of gel electrolyte makes it difficult to achieve high modulus, and it cannot effectively resist extreme mechanical deformation such as tearing, piercing and crushing, which to some extent limits the application scenarios of flexible aqueous zinc-ion batteries. The Chinese patent with the application number 202111461059.7, a flexible eutectic gel and its preparation method and application, a strain sensor, adds polyvinyl alcohol and gel reinforcing agent into the eutectic solvent, and repeatedly freezes and thaws to obtain a flexible eutectic gel. However, the conductivity, toughness and strength of the eutectic gel electrolyte are not high. The Chinese patent with the application number 202411148575.8, a conductive polymer / hydrogel layered composite electrolyte for aqueous zinc-ion batteries, proposes a method of cross-linking sodium alginate and zinc sulfate on a non-woven fabric substrate to form a sodium alginate gel film, and coating it on a polymer solution to prepare a flexible aqueous zinc-ion battery. However, the flexible aqueous zinc-ion battery prepared by this method still cannot withstand high mechanical force.

[0004] Therefore, it is of great significance to design a gel electrolyte with high modulus to overcome the growth stress of zinc dendrites through mechanical inhibition effect for the research and application of aqueous zinc-ion batteries. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the present application aims to provide a high-modulus leather / eutectic gel composite electrolyte and a preparation method and application thereof, to solve the technical problem that the modulus of the existing gel electrolyte is low and it is difficult to effectively cope with extreme mechanical deformation, thereby limiting its application in the field of flexible batteries and the like.

[0006] To achieve the above object, the present application adopts the following technical solutions: One of the purposes of the present application is: The present application provides a high modulus leather / eutectic gel composite electrolyte, which comprises a eutectic gel and leather, wherein the components of the eutectic gel comprise zinc salt, small molecule polyol, water and polyvinyl alcohol (type 1799); and the high molecular network of the eutectic gel and the fiber network of the leather form a three-dimensional network structure of mutual interpenetration.

[0007] Preferably, the mass ratio of the zinc salt, small molecule polyol, water and polyvinyl alcohol (type 1799) in the eutectic gel is (1-2):(2-10):(10-18):(1-5).

[0008] The amount of each component of the eutectic gel of the present application needs to be accurately controlled. Because in the present system, too little amount of zinc salt leads to poor conductivity, and too much amount of zinc salt increases the viscosity of the electrolyte system, thereby affecting the battery dynamics and increasing the cost; too much amount of alcohol leads to dehydration of the leather fibers, affecting ion transmission; too much amount of polyvinyl alcohol leads to too large viscosity of the gel solution, which is not easy to penetrate into the pores of the leather fibers, and too little amount of polyvinyl alcohol makes it difficult to fill the pores of the leather fibers and cannot form a steel-reinforced concrete structure.

[0009] Preferably, the zinc salt is selected from any one or more of zinc chloride, zinc sulfate, zinc acetate, zinc perchlorate and zinc triflate; and the small molecule polyol is any one or more of ethylene glycol, glycerol, 1,2-propanediol and sorbitol.

[0010] Preferably, the leather is any one of cowhide, pigskin, goat skin and sheepskin, and the thickness of the leather is 1.0-2.0 mm.

[0011] Preferably, the mass ratio of the leather to the eutectic gel is (4.6-11):(46-55), which can better realize vacuum impregnation and will not waste too much raw material.

[0012] The technical problems solved by the present application include how to simultaneously achieve the mechanical properties and electrical conductivity of the electrolyte, and improve the performance of the electrolyte in both aspects. The ion conductivity of polyvinyl alcohol (PVA) gel depends on its hydration structure and ion migration path, and the woven structure of leather endows it with excellent mechanical properties, but the addition of leather fibers may hinder ion migration and thus reduce electrical conductivity. By adjusting the amount of zinc salt to ensure sufficient crosslinking of PVA molecular chains, the loose gel structure or ion transport channel caused by the introduction of leather fibers can be avoided. By adjusting the ratio of components of the eutectic gel and controlling the amount ratio of the eutectic gel and leather, the electrical and mechanical properties of the high modulus leather / eutectic gel composite electrolyte of the present application can be effectively improved.

[0013] The second object of the present application is to provide a preparation method of the high modulus leather / eutectic gel composite electrolyte. The present application provides a preparation method of the high modulus leather / eutectic gel composite electrolyte, comprising the following steps: S1, uniformly mixing zinc salt, small molecule polyol, water and polyvinyl alcohol (type 1799), heating and stirring until the components are dissolved to form a eutectic gel solution; S2, vacuum impregnating the leather with the eutectic gel solution to obtain leather containing eutectic gel; S3, after the leather containing eutectic gel is subjected to multiple freeze-thaw cycles, a high modulus leather / eutectic gel composite electrolyte with a simulated steel-reinforced concrete structure is prepared.

[0014] Preferably, in step S1, the heating temperature is 85-95℃.

[0015] Preferably, in step S2, the vacuum impregnation pressure is 0.078-0.088 MPa, and the time is 4-12 h, so as to improve the penetration speed and degree of the eutectic gel in the leather.

[0016] Preferably, in step S3, in the freeze-thaw cycle, the freezing temperature is -25 to -15℃, the thawing temperature is room temperature, the freeze-thaw cycle number is 2-5 times, the freezing time is 6-12 h each time, and the thawing time is 2-6 h.

[0017] The third object of the present application is to provide an application of the high modulus leather / eutectic gel composite electrolyte. The present application also provides an application of the high modulus leather / eutectic gel composite electrolyte, which can be used as a battery electrolyte for aqueous zinc ion batteries.

[0018] Compared with the prior art, the present application has the following beneficial effects: The application provides a high-modulus leather / eutectic gel composite electrolyte and a preparation method and application thereof. The leather / eutectic gel composite electrolyte has a reinforced concrete structure: 1) the modulus can be significantly improved: the leather fiber acts as a skeleton in the composite electrolyte, and its weaving structure is like a steel bar in reinforced concrete, providing stable mechanical support for the gel electrolyte. When subjected to external force, the leather fiber can withstand and disperse part of the external force through its deformation characteristics and efficient stress transmission mechanism, thereby enhancing the modulus of the leather / eutectic gel composite electrolyte, making it have stronger resistance when facing external mechanical stress, and greatly improving the stability and reliability of the gel electrolyte in practical application; 2) the growth of dendrites can be inhibited: during the charging and discharging process of the aqueous zinc ion battery, Zn 2+ Uneven deposition on the surface of the zinc negative electrode is the main reason for the formation of zinc dendrites. The continuous growth of zinc dendrites not only pierces the separator to cause short circuit of the battery, but also reduces the cycle stability and service life of the battery. In the leather / eutectic gel composite electrolyte proposed in the application, the high-density weaving structure of the leather can act as a physical barrier to effectively inhibit the growth of zinc dendrites. When zinc ions are deposited on the surface of the negative electrode, the pores and channels of the leather fiber can guide the directional transmission of Zn 2+ , so that Zn 2+ is uniformly deposited on the surface of the zinc negative electrode, avoiding the formation of sharp dendrites. At the same time, the high modulus of the leather fiber further enhances its resistance to zinc dendrite piercing, significantly improving the safety of the battery; 3) the environmental tolerance can be enhanced: in the leather / eutectic gel composite electrolyte proposed in the application, small molecule polyols and water act as hydrogen bond donors, and zinc salts act as hydrogen bond acceptors, forming a polyol-water-zinc salt eutectic system through intermolecular hydrogen bonding. The small molecule polyol molecule contains multiple hydroxyl groups, which can provide abundant hydrogen bond donor sites and form strong hydrogen bonds with water molecules; and the metal ions in the zinc salt can also form coordination bonds with the oxygen atoms in the polyol and water molecules, further stabilizing the eutectic structure. This stable structure makes the leather / eutectic gel composite electrolyte proposed in the application have excellent environmental tolerance. In extreme temperature environments, the low freezing point and non-volatile characteristics of the leather / eutectic gel composite electrolyte proposed in the application enable the electrolyte to maintain stable composition and performance under various environmental conditions, reducing the performance degradation of the battery caused by changes in the electrolyte, thereby improving the applicability and stability of the aqueous zinc ion battery under different environments.

[0019] The application further provides a preparation method of the leather / eutectic gel composite electrolyte. The method simulates a steel skeleton with a three-dimensional network structure of leather and simulates concrete with eutectic gel, and prepares the leather / eutectic gel composite electrolyte with a steel-concrete structure by vacuum impregnation and freeze-thaw cycle technology. Specifically, leather fibers are immersed in a eutectic gel solution, and the gel solution is uniformly infiltrated into the hierarchical structure of the leather fibers by utilizing the pore structure and porous characteristics of the leather fibers. Then, the eutectic gel solution between the pores of the leather fibers is solidified by freeze-thaw cycle to obtain the leather / eutectic gel composite electrolyte. In this process, the polymer network of the eutectic gel and the fiber network of the leather are interpenetrated to form an interpenetrated network structure. Meanwhile, the hydroxyl groups, carboxyl groups and zinc ions in the polymer network of the eutectic gel can form multiple hydrogen bond interactions and electrostatic interactions with active functional groups (such as hydroxyl groups, carboxyl groups and amino groups) on the surface of the leather fibers, thereby enhancing the binding strength between the eutectic gel and the leather fibers and ensuring the stability and reliability of the leather / eutectic gel composite electrolyte under various use conditions. The leather / eutectic gel composite electrolyte has simple operation steps, excellent comprehensive performance and wide practical application potential.

[0020] Test results show that the modulus of the leather / eutectic gel composite electrolyte provided by the application can reach 20.9 MPa, and the ionic conductivity is 16.1 mS·cm -1 , which proves that the introduction of leather fibers can enhance the modulus of the composite electrolyte. Based on the leather / eutectic gel composite electrolyte, a Zn-Zn symmetric battery is assembled, and under the test conditions of 1 mA cm -2 , 1 mAh cm -2 , the battery can be stably cycled for 400 h, which further proves the excellent performance of the composite electrolyte in practical application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 FIG. 1 is a SEM image of the leather / eutectic gel composite electrolyte prepared in Example 1 of the present application; Figure 2 FIG. 2 is a comparison of (a) modulus and (b) conductivity of the leather / eutectic gel composite electrolyte and the eutectic gel electrolyte prepared in Example 1 of the present application; Figure 3 FIG. 3 is a long cycle performance of the Zn-Zn symmetric battery assembled by the leather / eutectic gel composite electrolyte and the eutectic gel electrolyte prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0022] The following detailed description of various exemplary embodiments of the application should not be considered to be limiting of the application, but rather a description of certain embodiments of the application. It is understood that the terminology used herein is for the purpose of describing particular embodiments of the application only and is not intended to limit the application. Additionally, for a numerical range recited in the application, every narrower numerical range that falls within the broader numerical range is also specifically disclosed. The narrower ranges can be included in or excluded from the application as appropriate. The upper and lower limits of these narrower ranges can independently be included or excluded in the range.

[0023] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification prevails.

[0024] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that "comprise", "comprising", "include", "including", "contain", "containing", and the like are to be construed as open-ended terms, i.e., meaning "including, but not limited to".

[0025] The present application provides a high modulus leather / eutectic gel composite electrolyte, a preparation method thereof, specifically comprising the following steps: 1) uniformly mixing zinc salt, small molecule polyol, water and polyvinyl alcohol (type 1799) in a mass ratio of (2.0-10.0):(4.0-20.0):(20.0-36.0):(2.0-10.0), and then stirring at 90±5°C until all the components are completely dissolved to obtain a eutectic gel solution; The zinc salt is zinc chloride, zinc sulfate, zinc acetate, zinc perchlorate or zinc triflate. The small molecule polyol is ethylene glycol, glycerol, 1,2-propanediol or sorbitol.

[0026] 2) under room temperature conditions, taking leather and eutectic gel solution in a mass ratio of (4.6-11):(46-55), completely immersing the leather in the eutectic gel solution, and after vacuum impregnation treatment, obtaining leather containing eutectic gel solution; The leather is rawhide or leather, the thickness of the leather is 1.0-2.0 mm, and the type of the leather includes any one of cowhide, pigskin, goat skin or sheepskin; the pressure of vacuum impregnation is 0.078-0.088 MPa, and the time is 4-12 h.

[0027] 3) freezing the leather containing the eutectic gel solution in a-20 DEG C environment, then thawing at room temperature, and obtaining the leather / eutectic gel composite electrolyte after multiple freeze-thaw cycles.

[0028] The freeze-thaw cycle is 2-5 times, the freezing time is 6-12 h, and the thawing time is 2-6 h.

[0029] The leather / eutectic gel composite electrolyte prepared by the preparation method has a modulus of 4.6-20.9 MPa and an ionic conductivity of 4.8-16.1 mS.cm -1 .

[0030] The application is further described below in combination with specific examples. The following examples use conventional materials and equipment in the art. The experimental methods in the following examples, unless otherwise specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, are conventional commercially available products, and their specifications are conventional specifications in the art. In the specification of the application and the following examples, unless otherwise specified, "%" means weight percent, "parts" means weight parts, and the ratio means weight ratio.

[0031] Example 1 1) uniformly mixing 2 g of zinc chloride, 4 g of ethylene glycol, 36 g of water and 4 g of polyvinyl alcohol, then stirring at 90 DEG C until all the ingredients are completely dissolved, to obtain a eutectic gel solution; 2) completely immersing 4.6 g of leather (goat skin) with a thickness of 1.0 mm in 46 g of the eutectic gel solution at room temperature, vacuum impregnating for 4 h under a pressure of 0.078 MPa, to obtain leather containing the eutectic gel solution; 3) freezing the leather containing the eutectic gel solution in a-20 DEG C environment for 10 h, then thawing at room temperature for 2 h, and obtaining the leather / eutectic gel composite electrolyte after 3 freeze-thaw cycles.

[0032] Example 2 1) uniformly mixing 5 g of zinc sulfate, 20 g of 1,2-propanediol, 20 g of water and 10 g of polyvinyl alcohol, then stirring at 90 DEG C until all the ingredients are completely dissolved, to obtain a eutectic gel solution; 2) The leather (pigskin) with a thickness of 11 g was completely immersed in 55 g of the eutectic gel solution at room temperature, and the leather / eutectic gel composite electrolyte was obtained after vacuum impregnation for 12 h under a pressure of 0.082 MPa and 5 freeze-thaw cycles. 3) The leather with eutectic gel solution was frozen at -20 °C for 8 h, and then thawed at room temperature for 4 h, and the leather / eutectic gel composite electrolyte was obtained after 5 freeze-thaw cycles.

[0033] Example 3 1) 10 g of zinc acetate, 4 g of glycerol, 36 g of water and 2 g of polyvinyl alcohol were mixed uniformly, and then stirred at 90 °C until all the ingredients were completely dissolved to obtain a eutectic gel solution; 2) The leather (cowhide) with a thickness of 8 g was completely immersed in 52 g of the eutectic gel solution at room temperature, and the leather with eutectic gel solution was obtained after vacuum impregnation for 4 h under a pressure of 0.088 MPa; 3) The leather with eutectic gel solution was frozen at -20 °C for 6 h, and then thawed at room temperature for 6 h, and the leather / eutectic gel composite electrolyte was obtained after 3 freeze-thaw cycles.

[0034] Example 4 1) 3 g of zinc perchlorate, 4 g of ethylene glycol, 36 g of water and 4 g of polyvinyl alcohol were mixed uniformly, and then stirred at 90 °C until all the ingredients were completely dissolved to obtain a eutectic gel solution; 2) The leather (sheepskin) with a thickness of 6 g was completely immersed in 47 g of the eutectic gel solution at room temperature, and the leather with eutectic gel solution was obtained after vacuum impregnation for 12 h under a pressure of 0.079 MPa; 3) The leather with eutectic gel solution was frozen at -20 °C for 8 h, and then thawed at room temperature for 4 h, and the leather / eutectic gel composite electrolyte was obtained after 4 freeze-thaw cycles.

[0035] Example 5 1) 2 g of zinc triflate, 4 g of sorbitol, 36 g of water and 4 g of polyvinyl alcohol were mixed uniformly, and then stirred at 90 °C until all the ingredients were completely dissolved to obtain a eutectic gel solution; 2) The leather (goat skin) with a thickness of 5.2 g was completely immersed in 46 g of the eutectic gel solution at room temperature, and the leather with eutectic gel solution was obtained after vacuum impregnation for 4 h under a pressure of 0.078 MPa; 3) The leather containing eutectic gel solution was placed in a -20 ℃ environment for freezing for 10 h, and then thawed at room temperature for 2 h. After 5 freeze-thaw cycles, the leather / eutectic gel composite electrolyte was obtained.

[0036] The modulus and conductivity of the leather / eutectic gel composite electrolyte prepared in Examples 1-5 were determined by electrochemical impedance method and tensile test, respectively, and the results are shown in Table 1. As can be seen from the table, the leather / eutectic gel composite electrolyte has high modulus and conductivity, and the modulus can reach 20.9 MPa and the conductivity can reach 16.1 mS·cm -1 .

[0037] Table 1 Performance test of leather / eutectic gel composite electrolyte

[0038] For example, Example 1, Figure 1 is the SEM image of the prepared leather / eutectic gel composite electrolyte. As can be seen from the figure, the leather fiber acts as a steel skeleton and has a high-density three-dimensional weaving structure, which provides stable mechanical support for the leather / eutectic gel composite electrolyte. The eutectic gel is filled in the pore structure inside the leather fiber and forms a close combination with the leather fiber, which helps to improve the overall performance and stability of the composite electrolyte.

[0039] Figure 2 is the comparison of (a) modulus and (b) conductivity of the eutectic gel electrolyte and the leather / eutectic gel composite electrolyte prepared in Example 1. As can be seen from the figure, the modulus of the eutectic gel electrolyte is 20.9 MPa and the conductivity is 15.1 mS·cm -1 . When combined with leather fibers, the modulus of the leather / eutectic gel composite electrolyte is increased to 20.9 MPa, which is increased by 553% compared with the eutectic gel electrolyte. In addition, the conductivity of the leather / eutectic gel composite electrolyte is 15.1 mS·cm -1 , which is similar to that of the eutectic gel electrolyte. These results show that the introduction of leather fibers can significantly improve the modulus of the leather / eutectic gel composite electrolyte without adversely affecting its conductivity.

[0040] The eutectic gel and leather / eutectic composite gel prepared in Example 1 were used as electrolytes, and soft-pack Zn-Zn symmetric batteries were assembled with Zn as the symmetric electrode, and battery tests were carried out on the Bluecell battery test system. Figure 3 is the long cycle performance of the symmetric battery. As can be seen from the figure, at a current density of 1 mA cm -2 , the specific capacity of the battery is 1 mAh cm -2Under the test conditions, the Zn-Zn symmetric battery based on the eutectic gel electrolyte shows a large fluctuation of voltage and a cycle life of less than 50 h. The Zn-Zn symmetric battery based on the leather / eutectic gel composite electrolyte can be stably cycled for 400 h, showing excellent cycle performance.

[0041] The above merely illustrates the technical idea of the present application and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A high modulus leather / eutectic gel composite electrolyte characterized in that, The eutectic gel comprises a zinc salt, a small-molecule polyol, water and polyvinyl alcohol, and the high-molecular network of the eutectic gel and the fiber network of the leather form an interpenetrating three-dimensional network structure.

2. The high modulus leather / eutectic gel composite electrolyte of claim 1, wherein, The mass ratio of the zinc salt, the small-molecule polyol, water and polyvinyl alcohol in the eutectic gel is (1-2):(2-10):(10-18):(1-5).

3. The high modulus leather / eutectic gel composite electrolyte of claim 1, wherein, The zinc salt is selected from any one or more of zinc chloride, zinc sulfate, zinc acetate, zinc perchlorate and zinc triflate; the small-molecule polyol is any one or more of ethylene glycol, glycerol, 1,2-propanediol and sorbitol.

4. The high modulus leather / eutectic gel composite electrolyte of claim 1, wherein, The mass ratio of the leather to the eutectic gel is (4.6-11):(46-55).

5. The high modulus leather / eutectic gel composite electrolyte according to any one of claims 1-4, characterized in that, The leather is any one of cowhide, pigskin, goat skin and sheepskin, and the thickness of the leather is 1.0-2.0 mm.

6. Process for the preparation of the high modulus leather / eutectic gel composite electrolyte according to any one of claims 1-5, characterized in that, The method comprises the following steps: S1, uniformly mixing a zinc salt, a small-molecule polyol, water and polyvinyl alcohol, heating and stirring until the components are dissolved to form a eutectic gel solution; S2, using the eutectic gel solution to perform vacuum impregnation treatment on leather to obtain leather containing eutectic gel; S3, performing multiple freeze-thaw cycles on the leather containing eutectic gel to obtain high-modulus leather / eutectic gel composite electrolyte with a structure similar to reinforced concrete.

7. The production method according to claim 6, characterized by, In the step S1, the heating temperature is 85-95℃.

8. The production method according to claim 6, characterized by, In the step S2, the vacuum impregnation pressure is 0.078-0.088 MPa, and the impregnation time is 4-12 h.

9. The production method according to claim 6, characterized by, In the step S3, in the freeze-thaw cycle, the freezing temperature is -25--15℃, the thawing temperature is room temperature, the freeze-thaw cycle number is 2-5, the freezing time is 6-12 h each time, and the thawing time is 2-6 h.

10. Use of the high modulus leather / eutectic gel composite electrolyte according to any one of claims 1 to 5, characterized in that, The eutectic gel is applied to a water-based zinc ion battery as a battery electrolyte.

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