A polymer hydrogel electrolyte with an interpenetrating network structure and its preparation method and application

Abstract

The invention discloses a polymer hydrogel electrolyte with an interpenetrating network structure, a preparation method thereof, and an application thereof. The preparation method comprises the following steps: preparing a spinning solution: weighing a polymer, dissolving it in an organic solvent, preparing a polymer solution, and stirring evenly; electrostatic spinning: injecting a precursor solution into a syringe for electrostatic spinning; rolling: spreading and fixing the precursor filaments, placing them in a roller press, and rolling them; preparing a polymer-zinc sulfate aqueous solution: weighing zinc sulfate heptahydrate, dissolving it in water to obtain a zinc sulfate aqueous solution, adding a polymer or a monomer thereof, and stirring evenly; casting: casting the polymer-zinc sulfate aqueous solution on the upper and lower surfaces of a polymer spinning membrane; and soaking: soaking the polymer interpenetrating membrane in the zinc sulfate aqueous solution.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc-iodine batteries, and in particular to a polymer hydrogel electrolyte with an interpenetrating network structure, a preparation method thereof, and applications thereof. Background Art

[0002] In recent years, rechargeable secondary ion batteries, as an important component of energy storage, have been widely used in portable electronic products and new energy vehicles. The active material reserves of aqueous zinc-iodine batteries are abundant, and the theoretical capacity of the negative electrode zinc metal is high (820mAh g -1 ), low electrochemical potential (-0.763 V vs. SHE), and good reaction kinetics, stability and reversibility in aqueous solution. The redox reaction of positive iodine can provide a considerable theoretical voltage (1.29 V) and theoretical capacity (211 mAh g -1 ), so aqueous zinc-iodine batteries have good application prospects in the field of large-scale energy storage. At present, the application of zinc-iodine batteries is still limited. The main reasons are as follows: (1) The shuttle effect of iodine species, that is, the soluble I generated during the charging process of zinc-iodine batteries 3- Ions can diffuse to the zinc metal negative electrode under the concentration gradient, causing the battery to self-discharge, which is manifested as low coulombic efficiency of the battery. (2) The zinc metal in the negative electrode is unevenly deposited during repeated deposition / stripping processes to form dendrites, which can easily pierce the diaphragm and cause a short circuit. In addition, zinc dendrites increase the contact area between the zinc negative electrode and the electrolyte, increasing the side reaction between the zinc metal and the aqueous electrolyte, causing corrosion of the zinc metal and hydrogen evolution, thereby reducing the coulombic efficiency and cycle performance of the battery.

[0003] A rationally designed semi-solid electrolyte can simultaneously alleviate the above-mentioned problems of zinc dendrites and iodine shuttle effects, and the development of semi-solid electrolytes with excellent performance can promote the development of flexible devices. In recent years, some semi-solid electrolytes have been developed to replace glass fiber separators and liquid electrolyte systems to improve the performance of zinc-iodine batteries. For example, Sonigara et al. [Sonigara KK, Zhao J, Machhi HK, et al. Self-assembled solid-state gelcatholyte combating iodide diffusion and self-discharge for a stable flexible aqueous Zn-I2 battery [J]. Advanced Energy Materials, 2020.] developed a PEO PPOPEO block copolymer gel electrolyte. This gel electrolyte blocks the diffusion of iodine in the microcrystalline structure through ion-selective hydrophilic / hydrophobic channels, and its micelle core can capture iodide, alleviating the self-discharge problem of zinc-iodine batteries. The zinc-iodine battery assembled using this gel electrolyte achieved a coulombic efficiency of 98.5% at a rate of 1C. Shang et al. [Shang W, Zhu J, Liu Y, et al. Establishing high-Performance quasi-solid Zn / I2 batteries with alginate-based hydrogel electrolytes [J]. ACS Applied Materials & Interfaces, 2021, 13 (21): 24756-24764.] developed an alginate-based solid electrolyte with a large number of anionic groups that can repel I3 - ions, optimized Zn 2+ The shuttle effect is effectively alleviated and the growth of zinc dendrites is reduced by the transmission of quasi-solid electrolyte. The zinc symmetric battery assembled with this quasi-solid electrolyte has a high conductivity at 2 mA cm -2 The assembled zinc-iodine battery was cycled for more than 500 h at a current density of 0.25 A g -1 The coulombic efficiency can reach over 95% at a current density of 1.5 %. The above electrolytes all effectively alleviate the self-discharge problem caused by the iodine shuttle effect and have good compatibility with the zinc negative electrode. However, the zinc ion transport performance of these electrolytes is poor, resulting in a decrease in the rate performance of the assembled zinc-iodine battery compared to conventional liquid system zinc-iodine batteries. Summary of the Invention

[0004] In response to the above problems, the present invention provides a polymer hydrogel electrolyte with an interpenetrating network structure, a preparation method and an application thereof. The polymer hydrogel electrolyte with an interpenetrating network structure has an iodine barrier effect, high mechanical strength and high zinc ion transmission performance.

[0005] The present invention provides a method for preparing a polymer hydrogel electrolyte with an interpenetrating network structure, comprising the following steps:

[0006] Prepare spinning solution: weigh the polymer and dissolve it in the organic solvent to prepare a polymer solution, and mix it to obtain a precursor solution;

[0007] Electrospinning: injecting the precursor solution into a syringe with a stainless steel needle, adjusting the voltage, temperature, relative humidity, propulsion speed, receiving distance and receiver speed, and performing electrospinning to obtain precursor filaments;

[0008] Rolling: The precursor filaments are spread and fixed, placed in a roller press, and the roller gap and roller speed are adjusted to roll to obtain a polymer spinning membrane;

[0009] Preparation of polymer-zinc sulfate aqueous solution: adding polymer or its monomer to zinc sulfate aqueous solution and mixing to obtain polymer-zinc sulfate aqueous solution;

[0010] Casting: Casting the polymer-zinc sulfate aqueous solution on the upper and lower surfaces of the polymer spinning membrane, and after standing and penetrating to complete, solidifying the polymer-zinc sulfate aqueous solution to obtain a polymer interpenetrating membrane;

[0011] Soaking: Soaking the polymer interpenetrating membrane in the zinc sulfate aqueous solution and waiting for swelling equilibrium to obtain a polymer hydrogel electrolyte with an interpenetrating network structure.

[0012] Furthermore, the polymer in the spinning solution is any one or more of polyacrylonitrile, polypropylene, polyvinyl pyrrolidone, polyacrylonitrile, polyvinylidene fluoride and polyimide.

[0013] Furthermore, the syringe in electrospinning is a syringe with a stainless steel needle, the stainless steel needle is a high-throughput stainless steel needle, the specification of the high-throughput stainless steel needle is 12G~20G, the voltage is adjusted to 20~30kV, the temperature is adjusted to 45±2℃, the relative humidity is adjusted to 45±2%rh, the propulsion speed is 3~6mL / h, the receiving distance is adjusted to 10~20cm, and the receiver speed is adjusted to 100~500rpm / min.

[0014] Furthermore, the roller gap during rolling is adjusted to 0-1.5 mm, and the roller speed is adjusted to 0-50 mm / s.

[0015] Furthermore, the concentration of the zinc sulfate aqueous solution in the prepared polymer-zinc sulfate aqueous solution is 0.08-0.25 mol / L.

[0016] Furthermore, the polymer in the prepared polymer-zinc sulfate aqueous solution is any one or more of polyvinyl alcohol, polyacrylic acid and polyacrylamide, and the mass percentage of the polymer is 5-15wt%.

[0017] Furthermore, the stirring method in the preparation of the polymer-zinc sulfate aqueous solution is magnetic stirring.

[0018] Furthermore, the concentration of the zinc sulfate aqueous solution during immersion is 0.5-2.0 mol / L.

[0019] The present invention also provides a polymer hydrogel electrolyte with an interpenetrating network structure, which is prepared using the above-mentioned preparation method.

[0020] The present invention also provides an aqueous zinc-iodine battery, wherein the polymer hydrogel electrolyte with the interpenetrating network structure is used as a semi-solid electrolyte component of the aqueous zinc-iodine battery.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The method for preparing an interpenetrating network structured polymer hydrogel electrolyte provided by the present invention has the following advantages: 1) the present invention utilizes two simple processes, spinning and casting, to combine the advantages of polymers with different characteristics to prepare a semi-solid electrolyte; 2) the raw materials used in the present invention are inexpensive, thereby reducing production costs.

[0023] The interpenetrating network structure polymer hydrogel electrolyte prepared by the present invention has excellent ionic conductivity and mechanical properties, can effectively resist zinc dendrites, accelerate ion transmission and block the shuttle of iodine species, and its electronegative groups of polyacrylonitrile can effectively block the shuttle of iodine species. It can be used as a semi-solid electrolyte component of aqueous zinc-iodine batteries, significantly improving the charge and discharge efficiency and rate performance of aqueous zinc-iodine batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 This is a flow chart for preparing the interpenetrating network structure polymer hydrogel electrolyte of Example 1;

[0026] Figure 2 This is a graph showing the rate performance test of zinc-iodine batteries assembled in Example 1 and Comparative Examples 1, 2, 3, and 4;

[0027] Figure 3 These are tensile performance test diagrams for Example 1 and Comparative Examples 1, 2, 3, and 4. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. The present invention is described in detail below with reference to the specific embodiments.

[0029] An embodiment of the present invention provides a method for preparing a polymer hydrogel electrolyte having an interpenetrating network structure, comprising the following steps:

[0030] Prepare spinning solution: weigh a certain amount of polymer and dissolve it in an organic solvent to prepare a polymer solution of a certain concentration, and mix it to obtain a precursor solution;

[0031] Electrospinning: inject the precursor solution into a syringe with a stainless steel needle of different sizes, adjust the voltage, temperature, relative humidity, propulsion speed, receiving distance, receiver speed and other parameters, and perform electrospinning to obtain the precursor filament;

[0032] Rolling: The precursor filaments are spread and fixed, placed in a roller press, and the roller gap, roller speed and other parameters are adjusted to roll and press to obtain a polymer spinning membrane;

[0033] Preparation of polymer-zinc sulfate aqueous solution: adding a certain amount of polymer or its monomer to the zinc sulfate aqueous solution and mixing to obtain the polymer-zinc sulfate aqueous solution;

[0034] Casting: Casting the polymer-zinc sulfate aqueous solution on the upper and lower surfaces of the polymer spinning membrane, and after standing and penetrating to complete, solidifying the polymer-zinc sulfate aqueous solution to obtain a polymer interpenetrating membrane;

[0035] Soaking: Soaking the polymer interpenetrating membrane in the zinc sulfate aqueous solution and waiting for swelling equilibrium to obtain a polymer hydrogel electrolyte with an interpenetrating network structure.

[0036] Specifically, the polymer in the spinning solution is any one or more of polyacrylonitrile, polypropylene, polyvinyl pyrrolidone, polyacrylonitrile, polyvinylidene fluoride, polyimide, etc.

[0037] Specifically, the syringe in electrospinning is a syringe with a stainless steel needle, the stainless steel needle is a high-throughput stainless steel needle, the specification of the high-throughput stainless steel needle is 12G~20G, that is, the inner diameter of the needle is 0.6~2.2mm, the voltage is adjusted to 20~30kV, the temperature is adjusted to 45±2℃, the relative humidity is adjusted to 45±2%rh, the propulsion speed is 3~6mL / h, the receiving distance is adjusted to 10~20cm, and the receiver speed is adjusted to 100~500rpm / min.

[0038] Specifically, the roller gap during rolling is adjusted to 0-1.5 mm, and the roller speed is adjusted to 0-50 mm / s.

[0039] Specifically, the concentration of the zinc sulfate aqueous solution in the prepared polymer-zinc sulfate aqueous solution is 0.08-0.25 mol / L, preferably 0.2 mol / L.

[0040] Specifically, the polymer in the prepared polymer-zinc sulfate aqueous solution is any one or more of polyvinyl alcohol, polyacrylic acid, and polyacrylamide, and the mass percentage of the polymer is 5-15wt%, preferably 10wt%.

[0041] Specifically, the stirring method in the prepared polymer-zinc sulfate aqueous solution is magnetic stirring.

[0042] Specifically, the concentration of the zinc sulfate aqueous solution during immersion is 0.5-2.0 mol / L, preferably 1 mol / L.

[0043] An embodiment of the present invention further provides a polymer hydrogel electrolyte with an interpenetrating network structure, which is prepared using the preparation method described above.

[0044] An embodiment of the present invention further provides an aqueous zinc-iodine battery, wherein the polymer hydrogel electrolyte with the interpenetrating network structure described above is used as a semi-solid electrolyte component of the aqueous zinc-iodine battery.

[0045] The following is an explanation with reference to specific embodiments:

[0046] Example 1

[0047] Prepare the interpenetrating network polymer hydrogel electrolyte as follows:

[0048] (1) Preparation of spinning solution: 1.0 g of polyacrylonitrile (PAN) was weighed and dissolved in 10 mL of N,N-dimethylformamide (DMF) solution at 60 °C and dispersed evenly to obtain a spinning precursor solution;

[0049] (2) Electrospinning: The precursor solution was injected into a syringe, and a stainless steel needle with an inner diameter of 1.6 mm was used. The voltage was adjusted to 20 kV, the temperature was controlled at 25 ± 2 °C, the relative humidity was controlled at 45 ± 2% rh, the propulsion speed was adjusted to 0.6 mL / h, the receiving distance was adjusted to 15 cm, and the receiver speed was adjusted to 400 rpm / min to perform electrospinning to obtain the precursor filament.

[0050] (3) Rolling: The precursor filaments were spread and fixed, placed in a roller press, and the roller gap was set to 0.05 mm and the roller speed was set to 50 mm / s. Rolling was performed to obtain a polymer spinning membrane with a thickness of 0.05 mm.

[0051] (4) preparing a polymer-zinc sulfate aqueous solution: weighing a certain amount of zinc sulfate heptahydrate and dissolving it in water to prepare a 0.2 M zinc sulfate aqueous solution, adding 10 wt % of polyvinyl alcohol (PVA), and stirring the mixture to obtain a polymer-zinc sulfate aqueous solution;

[0052] (5) Casting: Place the polymer spun film in a glass mold with a depth of 0.5 mm. Add appropriate amounts of polymer-zinc sulfate aqueous solution to the upper and lower surfaces of the polymer spun film. Press the glass mold cover flat on the glass mold until the solution fills the mold. Let it stand for 6 h. Freeze the glass mold at -20°C for 7 h and then thaw it for 3 h. Repeat the freeze-thaw process three times to solidify the polymer interpenetrating membrane.

[0053] (6) Soaking: Soak the polymer interpenetrating membrane in a 1 mol / L zinc sulfate aqueous solution for 3 h to obtain a polymer hydrogel electrolyte membrane with an interpenetrating network structure.

[0054] Comparative Example 1

[0055] This comparative example provides a polymer hydrogel electrolyte with an inorganic-interpenetrating network structure, which differs from Example 1 in that a commercial glass fiber membrane GF / A is used instead of the polymer spinning membrane.

[0056] Comparative Example 2

[0057] This comparative example provides a PAN polymer electrolyte membrane, which differs from Example 1 in that the polymer-zinc sulfate aqueous solution is not cast.

[0058] Comparative Example 3

[0059] This comparative example provides a PVA polymer electrolyte membrane, which differs from Example 1 in that no polymer spinning membrane is added, and the PVA-zinc sulfate aqueous solution is directly used to synthesize the polymer electrolyte membrane.

[0060] Comparative Example 4

[0061] This comparative example provides an inorganic fiber electrolyte membrane, which differs from Example 1 in that a commercial glass fiber membrane GF / D is directly used instead of the polymer interpenetrating membrane.

[0062] Zinc-iodine battery performance test: The electrolyte membranes prepared in Example 1 and Comparative Examples 1, 2, 3, and 4 were respectively pressed by a belt punch to obtain small discs with a diameter of 16 mm. Activated carbon (AC), conductive carbon, and polyvinylidene fluoride were mixed evenly in a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added dropwise. After uniform dispersion, an activated carbon slurry was obtained. The activated carbon slurry was evenly applied on graphite paper to prepare an activated carbon electrode. The activated carbon electrode was placed in iodine vapor for adsorption for 12 hours to obtain I2@AC, which was used as the positive electrode of the zinc-iodine battery. The battery CR2032 button-type Zn||I2 battery was assembled. The electrolyte membrane was punched into a 16 mm disc using the above steps. The negative electrode material was a zinc metal disc with a diameter of 14 mm. The positive electrode material was the 12 mm I2@AC obtained in the above steps. The supporting material was a stainless steel sheet and a stainless steel gasket with a diameter of 16 mm. The performance test was performed using a Xinwei battery test system at a voltage of 0.6-1.8 V and a gamma-ray diffraction curve of 0.1-4.2 Ag. -1 The rate performance test is carried out within the current density range, and the results are shown in Figure 2 . Compared with the zinc-iodine battery assembled with the electrolyte membranes prepared in Comparative Examples 1, 2, and 4, the zinc-iodine battery assembled with the electrolyte membrane prepared in Example 1 shows the best discharge specific capacity and coulombic efficiency at the same rate. Compared with the zinc-iodine battery assembled with the electrolyte membrane prepared in Comparative Example 3, the discharge specific capacity and rate performance of the zinc-iodine battery assembled with the electrolyte membrane prepared in Example 1 are slightly worse, but its stability and coulombic efficiency under low current are far better than those of the zinc-iodine battery assembled with the electrolyte membrane prepared in Comparative Example 3. The zinc-iodine battery assembled with the electrolyte membrane prepared in Comparative Example 3 fails after one cycle of charge and discharge from a high rate (20C) to a low rate (0.5C), while the zinc-iodine battery assembled with the electrolyte membrane prepared in Example 1 operates smoothly under the same test conditions. The above results show that the electrolyte membrane prepared in Example 1 has good zinc ion transport performance, stability and good I3 - Ion barrier effect.

[0063] Mechanical strength test: The electrolyte membranes prepared in Example 1 and Comparative Examples 1, 2, 3, and 4 were cut into elongated rectangles, and their initial lengths and cross-sectional areas were recorded. Tensile tests were performed using a Xinsansi universal testing machine. The results are shown in Table 1. Figure 3 Compared with the electrolyte membranes prepared in Comparative Examples 1, 2, 3, and 4, the electrolyte membrane prepared in Example 1 has the highest corresponding stress when broken, showing excellent mechanical strength, indicating that it has the greatest potential in inhibiting zinc dendrite growth.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an interpenetrating network structured polymer hydrogel electrolyte, characterized in that: The following steps are involved: Prepare spinning solution: weigh a polymer and dissolve it in an organic solvent, with the mass volume ratio of the polymer to the organic solvent being (0.9-1.1):10, to prepare a polymer solution, and mix well to obtain a precursor solution; Electrospinning: injecting the precursor solution into a syringe, adjusting the voltage, temperature, relative humidity, propulsion speed, receiving distance and receiver speed, and performing electrospinning to obtain precursor filaments; Rolling: The precursor filaments are spread and fixed, placed in a roller press, and the roller gap and roller speed are adjusted to roll to obtain a polymer spinning membrane; Preparation of polymer-zinc sulfate aqueous solution: adding polymer or its monomer to zinc sulfate aqueous solution and mixing to obtain polymer-zinc sulfate aqueous solution; Casting: Casting the polymer-zinc sulfate aqueous solution on the upper and lower surfaces of the polymer spinning membrane, and after standing and penetrating to complete, solidifying the polymer-zinc sulfate aqueous solution to obtain a polymer interpenetrating membrane; Soaking: Soaking the polymer interpenetrating membrane in the zinc sulfate aqueous solution and waiting for swelling equilibrium to obtain a polymer hydrogel electrolyte with an interpenetrating network structure; Wherein, the polymer in the spinning solution is any one or more of polyacrylonitrile, polypropylene, polyvinyl pyrrolidone, polyvinylidene fluoride and polyimide; The polymer in the prepared polymer-zinc sulfate aqueous solution is any one or more of polyvinyl alcohol, polyacrylic acid and polyacrylamide, and the mass percentage of the polymer is 5-15 wt%.

2. The preparation method according to claim 1, wherein The syringe in the electrospinning is a syringe with a stainless steel needle, the stainless steel needle is a high-throughput stainless steel needle, the specification of the high-throughput stainless steel needle is 12 G~20 G, the voltage is adjusted to 20~30 kV, the temperature is adjusted to 45±2°C, the relative humidity is adjusted to 45±2%rh, the propulsion speed is 3~6 mL / h, the receiving distance is adjusted to 10~20 cm, and the receiver speed is adjusted to 100~500 rpm / min.

3. The preparation method according to claim 1, wherein During rolling, the roll gap is adjusted to 0.01-1.5 mm, and the roll speed is adjusted to 0.01-50 mm / s.

4. The preparation method according to claim 1, wherein The concentration of the zinc sulfate aqueous solution in the prepared polymer-zinc sulfate aqueous solution is 0.08-0.25 mol / L.

5. The preparation method according to claim 1, wherein The stirring method in the prepared polymer-zinc sulfate aqueous solution is magnetic stirring.

6. The preparation method according to claim 1, wherein The concentration of the zinc sulfate aqueous solution during soaking is 0.5-2.0 mol / L.

7. A polymer hydrogel electrolyte with an interpenetrating network structure, characterized in that: It is prepared using the preparation method according to any one of claims 1 to 6.

8. An aqueous zinc-iodine battery, characterized in that: The polymer hydrogel electrolyte with an interpenetrating network structure as claimed in claim 7 is used as a semi-solid electrolyte component of the aqueous zinc-iodine battery.

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