A quasi-solid-state electrolyte based on ionic liquid, its preparation method and application

Abstract

The present invention discloses a quasi-solid-state electrolyte based on ionic liquid, its preparation method and application, belonging to the technical field of energy materials. The quasi-solid-state electrolyte of the present invention is a PAM@MMT gel material prepared by a condensation reaction of N-N methylenebisacrylamide, acrylamide, potassium persulfate, dimethyl sulfoxide, montmorillonite, potassium hydroxide, and zinc salt. It has excellent mechanical strength, flexibility and tensile properties, meeting the actual application requirements of flexible zinc-air batteries. At the same time, the PAM@MMT quasi-solid-state electrolyte has excellent ionic conductivity and small diffusion resistance, which is conducive to the rapid transport of active species. The flexible zinc-air battery assembled with the PAM@MMT gel material as the electrolyte shows high open-circuit voltage, foldable stability and charge-discharge cycle stability. The synthesis method of the present invention is simple and easy to implement, and the raw materials are easily available, which is conducive to implementation and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy materials, and particularly relates to a quasi-solid electrolyte based on ionic liquid, a preparation method thereof, and an application thereof. Background Art

[0002] With the important demands of people for high-quality material life, flexible wearable electronic devices such as foldable mobile phones and sensors are developing rapidly, which also puts forward necessary requirements for energy storage devices such as ultra-thin, high energy density, and stable structure. Zinc-air batteries have received extensive attention due to their high theoretical energy density, low cost, and excellent stability. For zinc-air batteries, to achieve their flexible structure, the electrolyte is a key component.

[0003] As one of the necessary components in the battery, the electrolyte plays important roles such as an electrode spacer layer and ion conduction. The ion conduction of the electrolyte has a great influence on the working electrochemical performance of the battery. The gel quasi-solid electrolyte has higher safety and environmental protection performance compared with the traditional electrolyte. Its good mechanical properties and flexibility can effectively avoid the environmental pollution problems caused by battery electrolyte leakage. At the same time, compared with all-solid electrolytes (such as Nafion resin, etc.), the gel quasi-solid electrolyte also has higher ionic conductivity, and currently can basically reach 10 -3 S·cm -1 order of magnitude, and its structural flexibility and stability are also better after assembling the battery. At the same time, the polymer itself is a completely insulating material, and this semi-solid gel matrix can also effectively isolate the electrodes, with high safety.

[0004] Currently, researchers have conducted a large number of studies on flexible zinc-air batteries. The results show that the tolerance of most flexible zinc-air batteries to bending, twisting, folding, stretching, etc. is still limited, and they can only withstand dozens to hundreds of charge-discharge cycles, and it is still difficult to carry out large-scale commercial applications of wearable electronic devices. There are still the following difficulties in the development and application of quasi-solid electrolytes:

[0005] (1) The tolerance of the electrolyte to external forces is not good, and more stable polymer matrices need to be explored to prepare quasi-solid electrolytes with stronger mechanical properties; (2) On the premise of ensuring mechanical properties, improve the ionic conductivity and water retention performance of the electrolyte to avoid the decline of battery performance caused by water loss problems; (3) To solve the contact problem between the electrolyte and the electrode. And due to the poor wettability of the quasi-solid electrolyte, the performance of the catalyst on the air cathode is difficult to reach the level equivalent to that of the liquid state. Therefore, the development of highly efficient, stable, and excellent mechanical property quasi-solid electrolytes has become one of the important directions of current flexible energy storage devices. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

[0007] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0008] Therefore, an object of the present invention is to overcome the deficiencies in the prior art and provide a quasi-solid electrolyte based on ionic liquid, including that the quasi-solid electrolyte based on ionic liquid is obtained by a condensation reaction of N-N methylene bisacrylamide, acrylamide, potassium persulfate, dimethyl sulfoxide, montmorillonite, potassium hydroxide, and zinc salt.

[0009] Another object of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for a quasi-solid electrolyte based on ionic liquid.

[0010] To solve the above technical problems, the present invention provides the following technical solutions: including,

[0011] Using acrylamide, N-N methylene bisacrylamide, and potassium persulfate as solutes, and a mixed solution of ultrapure water and dimethyl sulfoxide as a solvent, ultrasonic stirring is performed to obtain a uniform mixed solution I;

[0012] Montmorillonite is added to the mixed solution I, and ultrasonic stirring is performed to obtain a uniform mixed solution II;

[0013] The mixed solution II is poured into a mold and placed in an oven for polymerization reaction to form a PAM@MMT gel;

[0014] Using potassium hydroxide and zinc salt as solutes, and ultrapure water as a solvent, stirring is performed to form an ionic liquid, which is added to the PAM@MMT gel cooled to room temperature, and left standing at room temperature to obtain a PAM@MMT quasi-solid electrolyte based on ionic liquid.

[0015] As a preferred scheme of the quasi-solid electrolyte based on ionic liquid of the present invention, wherein: the mass ratio of acrylamide, N-N methylene bisacrylamide, and potassium persulfate in the mixed solution I is 1000:1:(2-3).

[0016] As a preferred scheme of the quasi-solid electrolyte based on ionic liquid of the present invention, wherein: the volume ratio of ultrapure water to dimethyl sulfoxide in the mixed solution I is 1:1.

[0017] As a preferred scheme of the quasi-solid electrolyte based on ionic liquid of the present invention, wherein: the concentration of potassium persulfate in the mixed solution I is 0.2-0.3 g / mL.

[0018] As a preferred embodiment of the ionic liquid-based quasi-solid electrolyte of the present invention, wherein: the mass ratio of montmorillonite to potassium persulfate in the mixed solution II is (1 to 1.5):1.

[0019] As a preferred embodiment of the ionic liquid-based quasi-solid electrolyte of the present invention, wherein: for the ionic liquid, the concentration of potassium hydroxide is 5 to 7 mol / L, and the concentration of zinc salt is 0.15 to 0.4 mol / L.

[0020] As a preferred embodiment of the ionic liquid-based quasi-solid electrolyte of the present invention, wherein: the zinc salt includes one of zinc oxide and zinc acetate.

[0021] As a preferred embodiment of the ionic liquid-based PAM@MMT quasi-solid electrolyte of the present invention, the volume of the ionic liquid is 1 / 5 of that of the PAM@MMT gel.

[0022] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of an ionic liquid-based quasi-solid electrolyte, including using a zinc foil as the negative electrode, a carbon cloth coated with commercial Pt / C and RuO 2 catalyst as the air electrode, and the quasi-solid electrolyte as the electrolyte. After assembling the negative electrode, the electrolyte, and the air electrode, a flexible zinc-air battery is obtained.

[0023] Advantages of the present invention:

[0024] (1) The ionic liquid-based quasi-solid electrolyte prepared by the present invention has excellent mechanical properties, with excellent mechanical strength and tensile properties, and can effectively avoid damage during use; at the same time, it has a small diffusion resistance and excellent ionic conductivity. When applied to a flexible zinc-air battery, it can obtain long-term cycle stability and a high open-circuit voltage, and can maintain normal discharge at different folding angles.

[0025] (2) The ionic liquid-based quasi-solid electrolyte of the present invention can effectively stabilize the deposition of zinc species and inhibit the growth of zinc dendrites, thereby improving the reliability and cycle life of the battery.

[0026] (3) By adding montmorillonite in the present invention, the cations therein can undergo ion exchange with other particles in the ionic liquid, thereby increasing the ion transport channels and accelerating mass transfer; at the same time, the mass ratio of montmorillonite to potassium persulfate is optimized to improve the ion exchange performance, thereby promoting the transport of ions in the electrolyte and improving the conductivity of the battery.

[0027] (4) The synthesis method of the present invention is simple and easy to implement. The electrolyte can be obtained through the condensation reaction of simple raw materials, which solves the deficiencies of the existing technology in complex synthesis and difficult large-scale preparation. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments 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. Among them:

[0029] Figure 1 It is the electrochemical impedance diagram of the electrolyte prepared in Example 1 of the present invention;

[0030] Figure 2 It is a physical photo of the flexible zinc-air battery device assembled with the electrolyte prepared in Example 1 of the present invention lighting an LED.

[0031] Figure 3 It is a physical photo of the flexible zinc-air battery device assembled with the electrolyte prepared in Example 1 of the present invention lighting an LED at different folding angles.

[0032] Figure 4 It is the stress-strain curve of the electrolytes prepared in Example 1 and Example 2 of the present invention;

[0033] Figure 5 It is the Young's modulus data diagram of the PAM@MMT quasi-solid gel electrolytes prepared in Examples 1 to 4 of the present invention;

[0034] Figure 6 It is the elongation at break data diagram of the PAM@MMT quasi-solid gel electrolytes prepared in Examples 1 to 4 of the present invention; Detailed Embodiments

[0035] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the embodiments of the specification.

[0036] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] Second, the "one embodiment" or "embodiment" referred to herein means a specific feature, structure or characteristic that may be included in at least one implementation manner of the present invention. The "in one embodiment" appearing in different places in this specification does not all refer to the same embodiment, nor is it an individual or selectively mutually exclusive embodiment with other embodiments.

[0038] The electrolyte prepared by the present invention is assembled into a flexible zinc-air battery device according to the following steps, specifically:

[0039] Using a zinc foil as the negative electrode, the prepared PAM@MMT quasi-solid-state gel as the electrolyte, and a carbon cloth coated with a commercial Pt / C+RuO 2 catalyst as the air electrode to assemble a flexible zinc-air battery device.

[0040] The present invention uses an electronic universal testing machine to characterize the mechanical properties of the prepared PAM@MMT quasi-solid-state gel; a CH Instrument 760E electrochemical workstation is used for ion conductivity testing.

[0041] Example 1

[0042] This example provides a preparation method of a quasi-solid-state electrolyte based on ionic liquid, specifically:

[0043] Weigh 10 g of acrylamide, 10 mg of N-N methylene bisacrylamide, and 25 mg of potassium persulfate and dissolve them in a mixed solvent of 100 mL of ultrapure water and dimethyl sulfoxide. Ultrasonic for 0.6 h and stir for 1 h to form a uniform mixed solution I with a concentration of 0.25 g / mL;

[0044] Weigh 30 mg of montmorillonite and dissolve it in the mixed solution I. Ultrasonic for 0.6 h and stir for 1 h to form a uniform mixed solution II;

[0045] Pour the mixed solution II into a mold and place it in a drying oven at 60 °C for polymerization reaction to form a PAM@MMT gel;

[0046] Using potassium hydroxide and zinc acetate as solutes and ultrapure water as the solvent, prepare an ionic liquid of 5.5 M potassium hydroxide + 0.25 M zinc acetate; add it to the PAM@MMT gel cooled to room temperature, with an added volume of 1 / 5 of the PAM@MMT gel, and let it stand at room temperature for 4 h to obtain the PAM@MMT quasi-solid-state electrolyte based on ionic liquid.

[0047] Figure 1 This is the electrochemical impedance diagram of the PAM@MMT quasi-solid-state gel electrolyte prepared in Example 1 of the present invention. It can be seen that the diffusion resistance of the PAM@MMT quasi-solid-state gel electrolyte prepared based on ionic liquid in Example 1 is small, which is beneficial to electron transfer and thus promotes reaction kinetics.

[0048] The electrolyte prepared in this example was assembled into an air battery. It was Figure 2 visible that the battery could light up an LED screen, demonstrating its practical value; Figure 3 It was shown that it could light up the LED lamp group at different folding angles, indicating that this electrolyte had excellent mechanical properties and ionic conductivity.

[0049] Example 2

[0050] This example provided a preparation method of an ionic liquid-based quasi-solid electrolyte, specifically as follows:

[0051] Weigh 7.5 g of acrylamide, 7.5 mg of N-N methylene bisacrylamide, and 20 mg of potassium persulfate, dissolve them in a mixed solvent of 100 mL of ultrapure water and dimethyl sulfoxide, ultrasonicate for 0.5 h, and stir for 1 h to form a uniform mixed solution I with a potassium persulfate concentration of 0.20 g / mL;

[0052] Weigh 24 mg of montmorillonite and dissolve it in the mixed solution I, ultrasonicate for 0.5 h, and stir for 2 h to form a uniform mixed solution II;

[0053] Pour the mixed solution II into a mold, and place it in a drying oven at 60 °C to undergo a polymerization reaction to form a PAM@MMT gel;

[0054] Using potassium hydroxide and zinc acetate as solutes and ultrapure water as the solvent, prepare an ionic liquid of 5 M potassium hydroxide + 0.4 M zinc acetate; add it to the PAM@MMT gel cooled to room temperature, with an added volume of 1 / 5 of the PAM@MMT gel, and let it stand at room temperature for 5 h to obtain the ionic liquid-based PAM@MMT quasi-solid electrolyte.

[0055] Example 3

[0056] This example provided a preparation method of an ionic liquid-based quasi-solid electrolyte, specifically as follows:

[0057] Weigh 15 g of acrylamide, 15 mg of N-N methylene bisacrylamide, and 30 mg of potassium persulfate, dissolve them in a mixed solvent of 100 mL of ultrapure water and dimethyl sulfoxide, ultrasonicate for 0.7 h, and stir for 1.2 h to form a uniform mixed solution I with a concentration of 0.3 g / mL;

[0058] Weigh 30 mg of montmorillonite and dissolve it in the mixed solution I, ultrasonicate for 0.5 h, and stir for 1.5 h to form a uniform mixed solution II;

[0059] Pour the mixed solution II into a mold, and place it in a drying oven at 50 °C to undergo a polymerization reaction to form a PAM@MMT gel;

[0060] Using potassium hydroxide and zinc acetate as solutes and ultrapure water as the solvent, an ionic liquid of 6.5 M potassium hydroxide + 0.3 M zinc acetate was prepared; it was added to the PAM@MMT gel cooled to room temperature, with the added volume being 1 / 5 of the PAM@MMT gel, and left to stand at room temperature for 5 h to obtain the ionic liquid-based PAM@MMT quasi-solid electrolyte.

[0061] Example 4

[0062] This example provides a preparation method for an ionic liquid-based quasi-solid electrolyte, specifically as follows:

[0063] Weigh 15 g of acrylamide, 15 mg of N,N'-methylenebisacrylamide, and 30 mg of potassium persulfate and dissolve them in a mixed solvent of 100 mL of ultrapure water and dimethyl sulfoxide. Sonicate for 0.7 h and stir for 1.2 h to form a homogeneous mixed solution I with a concentration of 0.3 g / mL.

[0064] Weigh 45 mg of montmorillonite and dissolve it in the mixed solution I. Sonicate for 1 h and stir for 2 h to form a homogeneous mixed solution II.

[0065] Pour the mixed solution II into a mold and place it in a drying oven at 70 °C to undergo a polymerization reaction to form a PAM@MMT gel.

[0066] Using potassium hydroxide and zinc oxide as solutes and ultrapure water as the solvent, an ionic liquid of 7 M potassium hydroxide + 0.25 M zinc oxide was prepared; it was added to the PAM@MMT gel cooled to room temperature, with the added volume being 1 / 5 of the PAM@MMT gel, and left to stand at room temperature for 5 h to obtain the ionic liquid-based PAM@MMT quasi-solid electrolyte.

[0067] Figures 4 to 6 They are respectively the stress-strain curve diagram, Young's modulus data diagram, and elongation at break data diagram of the electrolyte prepared in the above examples. From the above results, it can be seen that the electrolyte prepared in the embodiments of the present invention has good mechanical strength, flexibility, and tensile properties, and can meet the foldable wire requirements of flexible zinc-air battery devices.

[0068] Example 5

[0069] This example is used to explore the influence of the mass ratio of montmorillonite to potassium persulfate on the performance of the prepared electrolyte, specifically as follows: Adjust the mass ratio of montmorillonite to potassium persulfate to 0:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1 respectively. The rest of the preparation processes are the same as those in Example 1. Assemble the prepared products into flexible zinc-air batteries and conduct open-circuit voltage tests. The results are shown in Table 1.

[0070] Table 1 Influence of different mass ratios of montmorillonite to potassium persulfate on the performance of the electrolyte

[0071]

[0072] As can be seen from Table 1, with the increase of the mass ratio of montmorillonite to potassium persulfate, the open-circuit voltage of the assembled battery device shows a trend of first increasing and then decreasing. When the mass ratio of montmorillonite to potassium persulfate is 1.2:1, the open-circuit voltage of the assembled battery device is the largest.

[0073] This is mainly because an appropriate mass ratio of montmorillonite to potassium persulfate can promote the uniform distribution of active substances in the electrode, improve the efficiency of the electrochemical reaction; at the same time, montmorillonite has good ion exchange performance, which can promote the ion transport in the electrolyte and improve the conductivity of the battery; further, the addition of montmorillonite in the scheme of the present invention can also promote the air permeability of the air cathode, improve the diffusion rate of oxygen in the air cathode, thereby increasing the output power of the battery.

[0074] Example 6

[0075] This example is used to explore the influence of the concentration of potassium hydroxide on the performance of the prepared electrolyte. Specifically: adjust the concentration of potassium hydroxide in the ionic liquid to be 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L respectively, and the rest of the preparation processes are the same as those in Example 1. Measure the ionic conductivity of the prepared products, and the results are shown in Table 2.

[0076] Table 2 Influence of different potassium hydroxide concentrations on the performance of the electrolyte

[0077]

[0078] As can be seen from Table 2, in the ionic liquid, the concentration of potassium hydroxide has an important influence on the ionic conductivity of the electrolyte. Appropriate concentration of potassium hydroxide can promote the formation of good ion transport channels for K + and OH - ions, thus improving the ionic conductivity. When the concentration of potassium hydroxide is low, the transport channels for K + and OH - ions in the ionic liquid may not be sufficient, resulting in limited ionic conductivity; while when the concentration of potassium hydroxide is too high, although the transport channels are improved, the too high concentration of potassium hydroxide may lead to enhanced interactions between ions, such as solvation between solvent molecules and ions, Coulomb interactions between ions, etc., thus affecting the free migration of ions and making the ionic conductivity not reach the optimum.

[0079] Example 7

[0080] This example is used to explore the influence of zinc salt concentration on the performance of the prepared electrolyte. Specifically: the zinc salt concentrations in the ionic liquid are adjusted to 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, and 0.5 mol / L respectively. The remaining preparation processes are the same as those in Example 1. The ionic conductivity of the prepared products is measured, and the results are shown in Table 3.

[0081] Table 3 Influence of different zinc salt concentrations on the electrolyte performance

[0082]

[0083] As can be seen from Table 3, the zinc salt concentration in the present invention has an obvious influence on the conductivity of the electrolyte in the ionic liquid. This is because as the zinc salt concentration increases, the solubility of ions also increases, thereby increasing the ion concentration in the ionic liquid and improving the conductivity of the ionic liquid. At the same time, an appropriate zinc salt concentration can adjust the ion spacing in the ionic liquid to minimize the distance between ions, thereby improving the conductivity of the ionic liquid. An appropriate zinc salt concentration can also improve the stability of the ionic liquid, reduce the loss of ions in the ionic liquid, and further improve the conductivity of the ionic liquid.

[0084] In summary, the present invention provides a quasi-solid-state electrolyte based on ionic liquid, its preparation method and application. The preparation method is simple and easy to implement, and the raw materials are easily available, which is conducive to implementation and application, and solves the deficiencies of complex synthesis and difficult large-scale preparation in the prior art.

[0085] The PAM@MMT quasi-solid-state gel electrolyte prepared based on ionic liquid in the present invention has excellent mechanical strength, flexibility and tensile properties, which is beneficial to the practical application of flexible zinc-air batteries. At the same time, because it is synthesized based on ionic liquid, it has good ionic conductivity and diffusion resistance, and can accelerate the mass transfer of active species and electron transport.

[0086] Montmorillonite is added to the electrolyte of the present invention. The cations therein can undergo ion exchange with other particles in the ionic liquid, thereby increasing the ion transport channels and accelerating mass transfer. At the same time, the mass ratio of montmorillonite to potassium persulfate is optimized to improve the ion exchange performance, thereby promoting the transport of ions in the electrolyte and improving the conductive performance of the battery.

[0087] The flexible zinc-air battery assembled with the PAM@MMT quasi-solid-state gel electrolyte prepared based on ionic liquid in the present invention has excellent battery performance, including: open circuit voltage, foldable stability and charge-discharge cycle stability, and has excellent practical value.

[0088] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A quasi-solid-state electrolyte based on ionic liquid, Characterized in that: The preparation method of the quasi-solid-state electrolyte based on ionic liquid is as follows. Using acrylamide, N-N methylenebisacrylamide and potassium persulfate as solutes, and a mixed solution prepared by mixing ultrapure water and dimethyl sulfoxide in a volume ratio of 1:1 as the solvent, ultrasonic stirring is carried out to obtain a uniform mixed solution I. The mass ratio of acrylamide, N-N methylenebisacrylamide and potassium persulfate in the mixed solution I is 1000:1:(2-3), and the concentration of potassium persulfate is 0.2-0.3 g / mL. Montmorillonite is added to the mixed solution I, and ultrasonic stirring is carried out to obtain a uniform mixed solution II. The mass ratio of montmorillonite to potassium persulfate in the mixed solution II is (1-1.5):

1. The mixed solution II is poured into a mold and placed in an oven for polymerization reaction to form a PAM@MMT gel. Using potassium hydroxide and zinc salt as solutes, and ultrapure water as the solvent, stirring is carried out to form an ionic liquid with a potassium hydroxide concentration of 5.5 mol / L and a zinc salt concentration of 0.15 mol / L, which is added to the PAM@MMT gel cooled to room temperature. The volume of the added ionic liquid is 1 / 5 of the PAM@MMT gel, and it is left standing at room temperature to obtain the PAM@MMT quasi-solid-state electrolyte based on ionic liquid.

2. The preparation method of the quasi-solid-state electrolyte based on ionic liquid according to claim 1, Characterized in that: The zinc salt includes one of zinc oxide and zinc acetate.

Images