Supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery for a high-voltage platform

Abstract

The present invention relates to the field of electrochemistry technology, and specifically relates to a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery on a high-voltage platform. Through the supramolecular interaction between the ionic liquid and polyvinyl alcohol molecules, the free water in the hydrogel is replaced, a water-poor ionic liquid polymer network is constructed, and zinc bromide is introduced as an ion carrier in the polymer network through the Hofmeister effect. By utilizing the chemical coupling effect between bromide ions and iodide ions, the preparation of a high-voltage solid-state zinc-iodine battery is ultimately realized; this solid electrolyte is made from an ionic liquid and a hydrogel solution, wherein the imidazole cation of the ionic liquid has a strong electron-withdrawing effect, and its anion combines with zinc ions and bromide ions to form a polyanion. Moreover, the water in the hydrogel is replaced by the ionic liquid, thereby preparing an ionic liquid gel electrolyte with good chemical stability, mechanical properties and electrochemical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly to a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery on a high-voltage platform. Background Art

[0002] Zinc metal has the characteristics of large theoretical capacity, low redox potential and rich resources. The aqueous zinc-ion battery prepared therefrom also has the advantages of high safety, low cost, environmental friendliness and high rate performance. Therefore, the aqueous zinc-ion battery has great application potential and research significance. Considering the disadvantages of poor safety and high hardness of current commercial lithium-ion batteries, which make them unsuitable for applications in flexible devices, it is necessary to develop solid-state batteries with high safety, excellent mechanical properties and excellent electrochemical performance and apply them to fields such as wearable fitness monitoring systems, artificial electronic skin, and flexible electronic screens. However, during the charging process of zinc-ion batteries, the hydrogen evolution potential is close to the zinc deposition potential, and the hydrogen evolution reaction and a series of side reactions inevitably occur, severely limiting the cycle life of aqueous zinc-ion batteries. For a series of problems of the zinc metal anode during operation, common solutions in existing technical solutions include the design of new electrodes, the optimization and modification of electrolytes, the modification of solid electrolytes and separators, etc.

[0003] The latest research results also disclose a new solution, that is, using a polymer electrolyte in the battery. The polymer electrolyte not only combines the advantages of the two methods of electrolyte modification and separator modification, and makes certain changes to the composition and function of the electrolyte, but also replaces the separator and directly becomes the medium between the positive and negative electrodes. This is because the polymer electrolyte uses polymers to build a three-dimensional network, and there are active sites on its molecular chain that can interact with ions. There are also ions and solvents that transport charges between molecular chains, and the transport mechanism of zinc ions is different from that of aqueous electrolytes. Therefore, the polymer electrolyte can not only regulate the zinc deposition behavior to achieve the effect of inhibiting dendrite growth, but also limit the activity of water molecules to inhibit the hydrogen evolution reaction. In addition, it has physical properties similar to those of a separator, so it can replace the separator to play the same role, thereby improving the zinc-ion battery to have a higher volume energy density. For example, through the bridging action of sulfate groups, uniform zinc-ion migration channels are formed between the helical gelatin chains in the thermoreversible hydrogel electrolyte to prepare a quasi-solid-state zinc-ion battery; this method successfully constructs a conformal electrode-electrolyte interface without an interface gap, guides uniform zinc-ion deposition, and inhibits water-related side reactions through the gelation effect. However, its Coulomb efficiency is not high enough, which results in mediocre performance in the full battery, and the long-cycle stability of the full battery is limited to a certain extent.

[0004] From the above research results and current processes, there is still a large room for improvement in using polymers to prepare electrolytes for zinc-ion batteries. While considering the cycle stability, it is also necessary to consider the compatibility with the cathode material.

[0005] Therefore, according to the relevant technologies mentioned above, it is urgent to develop a supramolecular ionic liquid gel electrolyte for solid-state zinc-iodine batteries on a high-voltage platform. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to propose a supramolecular ionic liquid gel electrolyte for solid-state zinc-iodine batteries on a high-voltage platform to solve the problems of poor chemical stability, mechanical properties, and electrochemical performance of ionic liquid gel electrolytes in the prior art.

[0007] Based on the above purpose, the present invention provides a supramolecular ionic liquid gel electrolyte for solid-state zinc-iodine batteries on a high-voltage platform.

[0008] A supramolecular ionic liquid gel electrolyte for solid-state zinc-iodine batteries on a high-voltage platform, characterized in that it comprises an ionic liquid and a hydrogel solution;

[0009] The ionic liquid is prepared from 1-butyl-3-methylimidazolium bromide and zinc bromide;

[0010] The hydrogel solution is prepared from zinc bromide, ultrapure water, and polyvinyl alcohol.

[0011] Preferably, the preparation method of the ionic solution is as follows:

[0012] Zinc bromide is added to 1-butyl-3-methylimidazolium bromide, and then stirred at 75 - 77 °C for 24 - 25 h to obtain the ionic liquid.

[0013] Preferably, the dosage ratio of 1-butyl-3-methylimidazolium bromide to zinc bromide is 50 - 55:51.3 - 56.4.

[0014] Preferably, the preparation method of the hydrogel solution is as follows:

[0015] Step A1. Dissolve anhydrous zinc bromide in ultrapure water to obtain a zinc bromide solution;

[0016] Step A2. Add polyvinyl alcohol to the zinc bromide solution, and then stir evenly at 85 - 90 °C to obtain the hydrogel solution.

[0017] Preferably, in step A1, the mass ratio of zinc bromide to ultrapure water is 112.6 - 135.1:100 - 120.

[0018] Preferably, the dosage ratio of the zinc bromide solution to polyvinyl alcohol in step A2 is 100 mL: 11.2 - 11.5 g.

[0019] Preferably, the preparation method of the supramolecular ionic liquid gel electrolyte is as follows:

[0020] Drop the hydrogel solution into an electrolyte mold, dry it, and then immerse it in an ionic liquid to obtain a supramolecular ionic liquid gel electrolyte after soaking.

[0021] Preferably, the temperature during drying is 40 - 45 °C.

[0022] Preferably, the temperature during soaking is 28 - 30 °C, and the duration is 60 - 65 h.

[0023] Advantages of the present invention:

[0024] The present invention provides a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery on a high-voltage platform. By utilizing the supramolecular solvent exchange property of the ionic liquid, multifunctional ionic liquids are introduced inside the polyvinyl alcohol network, and a stable ionic liquid gel is constructed through non-coordination bonds. This enables the gel electrolyte to not only have excellent physical properties but also resist a certain amount of external force to avoid deformation, forming a self-supporting solid electrolyte network;

[0025] The present invention utilizes the Hofmeister effect to introduce a low concentration of zinc halide salt in the ionic liquid gel as the ion source for charge transfer, enabling the ionic liquid gel electrolyte to function as a zinc ion conductor. The active sites on the polymer segments and the supramolecular interaction of the ionic liquid jointly regulate the conduction of zinc ions, achieving the stability of the zinc metal electrode interface and the cycle stability of the battery;

[0026] A large number of bromide ions still exist in the ionic liquid gel electrolyte prepared by the present invention, which can catalyze the coupling of iodine, enabling the positive valence conversion reaction of iodide ions to occur. The lower concentration of the halide salt enables the zinc-iodine battery to exhibit a higher theoretical capacity and a higher working voltage;

[0027] The ionic liquid added during the preparation process of the present invention also has a super-solvent effect, which can reduce the water molecules in the network, and the polymer segments also restrict the activity of water molecules, inhibiting the hydrogen evolution reaction and also preventing the products of iodine positive valence conversion from being decomposed by water, achieving a high voltage and a long cycle life for the zinc-iodine battery system;

[0028] Adding polyvinyl alcohol with a polymerization degree of 170,000 - 220,000 to the hydrogel solution of the present invention enables the ionic liquid gel to also have good mechanical properties such as tensile stress and elongation at break;

[0029] Therefore, compared with the prior art, the supramolecular ionic liquid gel electrolyte of the solid-state zinc-iodine battery for high-voltage platforms prepared in the present invention has better chemical stability, mechanical properties, and electrochemical properties, as well as a broader application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the descriptions of the embodiments or the prior art. Obviously, the drawings in the following descriptions are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 Schematic diagram of the preparation process of the supramolecular ionic liquid gel electrolyte in the present invention;

[0032] Figure 2 1H NMR spectra of the supramolecular ionic liquid gel electrolyte and polyvinyl alcohol prepared in Example 1 and Comparative Example 1 of the present invention;

[0033] Figure 3 Fourier transform infrared spectra of ionic liquid 1 and the supramolecular ionic liquid gel electrolyte prepared in Example 1 of the present invention, and ionic liquid 2 and the supramolecular ionic liquid gel electrolyte prepared in Comparative Example 1 of the present invention;

[0034] Figure 4 Cycling curve of the supramolecular ionic liquid gel electrolyte prepared in Example 1 and Comparative Example 1 of the present invention after being assembled into a zinc symmetric battery at a current density of 0.2 mA cm -2 ;

[0035] Figure 5 SEM photograph of the metal negative electrode after 100 charge-discharge cycles of the supramolecular ionic liquid gel electrolyte prepared in Example 1 of the present invention after being assembled into a zinc symmetric battery at a current density of 0.1 mA cm -2 and a deposition capacity of 0.1 mA cm -2 ;

[0036] Figure 6 Relationship diagram between the Coulombic efficiency and the number of cycling circles during charge-discharge cycling of the supramolecular ionic liquid gel electrolyte prepared in Example 1 and Comparative Example 1 of the present invention after being assembled into a zinc-copper battery;

[0037] Figure 7 After the supramolecular ionic liquid gel electrolyte prepared in Example 1 of the present invention is assembled into a zinc-iodine battery, at 0.05 Ag -1 , 0.1 Ag -1 , 0.2 Ag -1 and 0.3 Ag-1 Charge-discharge curve at a current density;

[0038] Figure 8 After the supramolecular ionic liquid gel electrolyte prepared in Example 1 of the present invention was assembled into a zinc-iodine battery, at 0.1 Ag -1 Graph of the relationship between the number of capacity cycles during cycling at a current density;

[0039] Figure 9 After the supramolecular ionic liquid gel electrolyte prepared in Example 1 of the present invention was assembled into a zinc-iodine battery, the voltammogram at a scanning rate of 0.2 mV / s. Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0041] The sources and properties of some raw materials used in the present invention are as follows:

[0042] 1-Butyl-3-methylimidazolium bromide was purchased from Shandong Dyke Biotechnology Co., Ltd., CAS: 85100-77-2; zinc bromide was purchased from Weifang Luzhe New Materials Co., Ltd., CAS: 7699-45-8; ammonium persulfate was purchased from Jinan Jinhao Chemical Co., Ltd., CAS: 7727-54-0; polyvinyl alcohol was purchased from Shaanxi Shangping Pharmaceutical Excipients Co., Ltd., CAS: 9902-89-5, and the degree of polymerization was 170,000 - 220,000.

[0043] Example 1: A preparation method of a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery with a high voltage platform is as follows:

[0044] S1. Add 51.3 g of zinc bromide to 50 g of 1-butyl-3-methylimidazolium bromide, and then stir at 75 °C for 24 h to obtain an ionic liquid;

[0045] S2. Dissolve 112.6 g of zinc bromide in 100 mL of ultrapure water to obtain a zinc bromide solution;

[0046] S3. Add 11.2 g of polyvinyl alcohol to 100 mL of the zinc bromide solution, and then stir evenly at 85 °C to obtain a hydrogel solution;

[0047] S4. Drop the hydrogel solution into an electrolyte mold, dry it at 40 °C, and then immerse it in the ionic liquid at 28 °C for 60 h to obtain a supramolecular ionic liquid gel electrolyte;

[0048] Example 2: A preparation method of a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery with a high voltage platform is as follows:

[0049] S1. Add 52.5 g of zinc bromide to 52 g of 1-butyl-3-methylimidazolium bromide, and then stir at 76 °C for 24.3 h to obtain an ionic liquid;

[0050] S2. Dissolve 124 g of zinc bromide in 107 mL of ultrapure water to obtain a zinc bromide solution;

[0051] S3. Add 11.3 g of polyvinyl alcohol to 100 mL of the zinc bromide solution, and then stir evenly at 87 °C to obtain a hydrogel solution;

[0052] S4. Drop the hydrogel solution into an electrolyte mold, dry it at 42 °C, and then immerse it in the ionic liquid at 29 °C. After soaking for 62 h, a supramolecular ionic liquid gel electrolyte is obtained;

[0053] Example 3: A method for preparing a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery for a high-voltage platform is as follows:

[0054] S1. Add 54.5 g of zinc bromide to 54 g of 1-butyl-3-methylimidazolium bromide, and then stir at 76 °C for 24.7 h to obtain an ionic liquid;

[0055] S2. Dissolve 128 g of zinc bromide in 112 mL of ultrapure water to obtain a zinc bromide solution;

[0056] S3. Add 11.4 g of polyvinyl alcohol to 100 mL of the zinc bromide solution, and then stir evenly at 89 °C to obtain a hydrogel solution;

[0057] S4. Drop the hydrogel solution into an electrolyte mold, dry it at 44 °C, and then immerse it in the ionic liquid at 29 °C. After soaking for 64 h, a supramolecular ionic liquid gel electrolyte is obtained;

[0058] Example 4: A method for preparing a supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery for a high-voltage platform is as follows:

[0059] S1. Add 56.4 g of zinc bromide to 55 g of 1-butyl-3-methylimidazolium bromide, and then stir at 77 °C for 25 h to obtain an ionic liquid;

[0060] S2. Dissolve 135 g of zinc bromide in 120 mL of ultrapure water to obtain a zinc bromide solution;

[0061] S3. Add 11.5 g of polyvinyl alcohol to 100 mL of the zinc bromide solution, and then stir evenly at 90 °C to obtain a hydrogel solution;

[0062] S4. Drop the hydrogel solution into the electrolyte mold, dry it at 45 °C, and then immerse it in an ionic liquid at 30 °C. After soaking for 65 h, a supramolecular ionic liquid gel electrolyte is obtained;

[0063] Comparative Example 1:

[0064] Compared with Example 1, in this comparative example, only "zinc bromide" is replaced by "zinc chloride", and the remaining steps and parameters are the same. This comparative example will not be repeated here, and finally a supramolecular ionic liquid gel electrolyte is obtained;

[0065] Comparative Example 2:

[0066] Compared with Example 1, in this comparative example, only "51.3 g of zinc bromide" is replaced by "102.58 g of zinc bromide", and the remaining steps and parameters are the same. This comparative example will not be repeated here, and finally a supramolecular ionic liquid gel electrolyte is obtained;

[0067] Comparative Example 3:

[0068] Compared with Example 1, in this comparative example, "51.3 g of zinc bromide" added in the ionic liquid preparation process is replaced by "102.58 g of zinc bromide", and at the same time, "112.6 g of zinc bromide" added in the zinc bromide solution preparation process is replaced by "22.52 g of zinc bromide", and the remaining steps and parameters are the same. This comparative example will not be repeated here, and finally a supramolecular ionic liquid gel electrolyte is obtained.

[0069] Performance test and data analysis:

[0070] Assemble the zinc metal symmetric battery with the supramolecular ionic liquid gel electrolytes prepared in the above Examples 1 - 4 and Comparative Examples 1 - 3, and then conduct charge and discharge tests on the performance. The test results are shown in Table 1:

[0071] Table 1

[0072] Item Cycle life / h Example 1 1250 Example 2 1247 Example 3 1256 Example 4 1252 Comparative Example 1 1174 Comparative Example 2 600 Comparative Example 3 350

[0073] As can be seen from Table 1, both the configuration ratio of 1-butyl-3-methylimidazolium bromide and zinc bromide in the ionic liquid and the concentration of the zinc bromide solution will affect the cycle life of the supramolecular ionic liquid gel electrolyte. By comparison, the supramolecular ionic liquid gel electrolyte prepared in the examples has the best performance;

[0074] Conduct ionic conductivity tests on the supramolecular ionic liquid gel electrolytes prepared in Examples 1 - 4 and Comparative Examples 1 - 3, and the calculated results are shown in Table 2:

[0075] Table 2

[0076] Item <![CDATA[Ionic conductivity / mS·cm -1 > Example 1 0.739 Example 2 0.732 Example 3 0.741 Example 4 0.734 Comparative Example 1 0.092 Comparative Example 2 0.698 Comparative Example 3 0.657

[0077] As can be seen from Table 2, the ionic conductivity of the supramolecular ionic liquid gel electrolyte prepared in the examples is higher, indicating that the examples can better promote the transport of zinc ions and have better ion-conducting ability;

[0078] The supramolecular ionic liquid gel electrolytes prepared in Examples 1-4 and Comparative Examples 1-3 were made into dumbbell shapes of 50 mm × 4 mm × 2 mm, and then fixed on the sample holder of a universal test tensile machine (Shenzhen Sansi Metrology Co., Ltd., CMT-6000), and tensile tests were carried out along the longitudinal axis direction. The calculated results are shown in Table 3:

[0079] Table 3

[0080] Item Tensile stress / kPa Elongation at break / % Example 1 2300 1210 Example 2 2473 1272 Example 3 2386 1315 Example 4 2397 1286 Comparative Example 1 1100 1350 Comparative Example 2 2079 1231 Comparative Example 3 1776 1200

[0081] As can be seen from Table 3, although the elongation at break of the examples and the comparative examples is similar, the stresses generated when stretched to similar multiples are quite different. A greater external force is required to pull the examples to the limit, indicating that the examples have better physical properties and are more advantageous in resisting stress;

[0082] After measuring the nuclear magnetic resonance hydrogen spectra of the supramolecular ionic liquid gel electrolyte and polyvinyl alcohol prepared in Example 1 and Comparative Example 1, Figure 2 , from Figure 2 it can be seen that the peak signals of the hydroxyl groups and the peak signals of the imidazole hydrogen ions of the ionic liquid in Example 1 and Comparative Example 1 are shifted, which may be due to the interaction between the prepared ionic liquid and the hydroxyl groups of polyvinyl alcohol;

[0083] After measuring the Fourier transform infrared spectra of ionic liquid 1 and the supramolecular ionic liquid gel electrolyte prepared in Example 1 and ionic liquid 2 and the supramolecular ionic liquid gel electrolyte prepared in Comparative Example 1 of the present invention, Figure 3 , after analyzing Figure 3 it can be known that the ionic liquid forms an ionic liquid gel with polyvinyl alcohol, but the performance of the ionic liquid gel prepared in Example 1 is relatively better;

[0084] After assembling the supramolecular ionic liquid gel electrolytes prepared in Example 1 and Comparative Example 1 into zinc symmetric batteries, the cyclic curves were measured at a current density of 0.2 mA cm -2 , and Figure 4 , after analyzing Figure 4 it can be known that Example 1 has more stable ion-conducting ability and longer cycle life;

[0085] After assembling the supramolecular ionic liquid gel electrolyte prepared in Example 1 into a zinc symmetric battery, at a current density of 0.1 mA cm -2 and a deposition capacity of 0.1 mA cm -2After 100 charge-discharge cycles under certain conditions, the metal negative electrode was scanned with a scanning electron microscope and obtained Figure 5 , from Figure 5 it can be seen that the zinc metal deposition on the surface of the zinc negative electrode is uniform and there is no significant dendritic growth;

[0086] After assembling the supramolecular ionic liquid gel electrolytes prepared in Example 1 and Comparative Example 1 into zinc-copper batteries, the relationship between the Coulombic efficiency and the number of cycle turns of charge-discharge cycles was analyzed and obtained Figure 6 , analysis Figure 6 shows that the cycle performance of the zinc-copper battery system formed in the example is more stable;

[0087] After assembling the supramolecular ionic liquid gel electrolyte prepared in Example 1 into a zinc-iodine battery, it was respectively at 0.05Ag -1 , 0.1Ag -1 , 0.2Ag -1 and 0.3Ag -1 After charge-discharge tests were carried out at the current density, it was obtained Figure 7 , from Figure 7 it can be seen that its charge-discharge curve has voltage platforms at 1.2V and 1.4V, indicating that the electrolyte successfully stimulated the positive valence conversion of iodine;

[0088] After assembling the supramolecular ionic liquid gel electrolyte prepared in Example 1 into a zinc-iodine battery, after testing and analyzing the relationship between the capacity cycle turns at a current density of 0.1A g -1 , it was obtained Figure 8 , from Figure 8 it can be seen that the example applied to the zinc-iodine battery shows excellent cycle stability and long cycle life;

[0089] After assembling the supramolecular ionic liquid gel electrolyte prepared in Example 1 into a zinc-iodine battery and scanning it at 0.2mV / s, a voltammogram was obtained Figure 9 , from Figure 9 it can be seen that the example has good electrochemical stability.

[0090] Those of ordinary skill in the art should understand that: The discussion of any above embodiment is only exemplary, and is not intended to imply that the scope of the present invention is limited to these examples; Under the idea of the present invention, the technical features between the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, and they are not provided in detail for the sake of brevity.

[0091] The present invention aims to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery for a high-voltage platform, characterized in that, It includes an ionic liquid and a hydrogel solution; The ionic liquid is prepared from 1-butyl-3-methylimidazolium bromide and zinc bromide; The hydrogel solution is prepared from zinc bromide, ultrapure water and polyvinyl alcohol; The mass ratio of the 1-butyl-3-methylimidazolium bromide to the zinc bromide is 50 - 55:51.3 - 56.4; The preparation method of the hydrogel solution is as follows: Step A1. Dissolve anhydrous zinc bromide in ultrapure water to obtain a zinc bromide solution; Step A2. Add polyvinyl alcohol to the zinc bromide solution, and then stir evenly at 85 - 90 °C to obtain a hydrogel solution; In Step A1, the mass ratio of the zinc bromide to the ultrapure water is 112.6 - 135.1:100 - 120; In Step A2, the dosage ratio of the zinc bromide solution to the polyvinyl alcohol is 100 mL:11.2 - 11.5 g; The preparation method of the supramolecular ionic liquid gel electrolyte is as follows: Drop the hydrogel solution into an electrolyte mold, dry it, and then immerse it in the ionic liquid. After soaking, a supramolecular ionic liquid gel electrolyte is obtained; The degree of polymerization of the polyvinyl alcohol is 170,000 - 220,000.

2. The supramolecular ionic liquid gel electrolyte for the solid-state zinc-iodine battery for a high-voltage platform according to claim 1, characterized in that, The preparation method of the ionic liquid is as follows: Add zinc bromide to 1-butyl-3-methylimidazolium bromide, and then stir at 75 - 77 °C for 24 - 25 h to obtain the ionic liquid.

3. The supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery for a high-voltage platform according to claim 1, wherein, The temperature during drying is 40 - 45 °C.

4. The supramolecular ionic liquid gel electrolyte for a solid-state zinc-iodine battery for a high-voltage platform according to claim 1, wherein The temperature during soaking is 28 - 30 °C, and the duration is 60 - 65 h.

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