Preparation method of nanofiber-based anti-freezing composite hydrogel electrolyte for zinc ion battery

Abstract

The invention relates to a hydrogel electrolyte with an anti-freezing function based on a composite nanofiber membrane, preparation of the hydrogel electrolyte and application of the hydrogel electrolyte in an aqueous zinc ion battery. The preparation method mainly comprises the following steps: (1) preparation of an organic polymer nanofiber membrane: dissolving a polymer in a solvent to prepare a spinning solution, and preparing the nanofiber membrane through electrostatic spinning; (2) compounding of a polymer / zinc oxide nanofiber membrane: dipping the nanofiber membrane prepared in the step (1) in a culture dish containing a Zn (Ac) 2 solution, and then carrying out hydrothermal treatment to obtain a polymer / zinc oxide composite nanofiber membrane; and (3) loading the anti-freezing hydrogel electrolyte, namely adding a polymer monomer, a zinc salt, an anti-freezing agent and a cross-linking agent into deionized water, heating and stirring to obtain a colorless and transparent solution, putting the polymer / zinc oxide composite nanofiber membrane prepared in the step (2) into a mold, filling two sides of the membrane with the colorless and transparent solution, freezing and thawing in a refrigerator, and drying to obtain the anti-freezing hydrogel electrolyte. The nanofiber-based anti-freezing hydrogel electrolyte is obtained. The anti-freezing zinc ion battery provided by the invention can still keep relatively high discharge capacity at an extremely low temperature, the preparation process is simple, the cost is low, and a better development strategy is provided for energy storage of the wearable flexible zinc ion battery in a low-temperature environment.

Description

Technical Field

[0001] The invention belongs to the field of aqueous zinc ion battery electrolytes, and specifically relates to a method for preparing a nanofiber-based composite hydrogel with an antifreeze function and an application of the nanofiber-based composite hydrogel in aqueous zinc ion batteries. Background Art

[0002] Flexible energy storage devices, as a key technology for realizing wearable electronics, have become a research hotspot. At present, lithium-ion batteries dominate the power supply market for portable electronic products and electric vehicles, but they involve volatile, flammable, toxic and expensive organic electrolytes, which are not suitable for use in wearable electronic products, especially those in close contact with the human body. Flexible zinc-ion batteries have the advantages of high safety, low cost, high energy / power density, and environmental friendliness. Although they are still in their infancy, they are expected to become advanced energy storage devices that meet the energy supply needs of wearable electronic products. As an important component of flexible zinc-ion batteries, gel electrolytes can avoid the leakage problem of liquid electrolytes; they can maintain physical integrity and flexibility under various mechanical deformations; gel electrolytes with limited free water and good adsorption affinity can reduce the dissolution of positive active materials and inhibit the growth of zinc dendrites, thereby helping to improve electrochemical stability. Traditional gel electrolytes have problems such as poor mechanical strength, low dimensional stability, limited elasticity, and unsatisfactory ductility. In addition, when used as electrolytes, the free water they contain will cause the electrolyte to inevitably freeze at temperatures below 0°C, thereby limiting ion transport and limiting the use of zinc-ion batteries in cold climates. Therefore, it is necessary to improve the adaptability of gel electrolytes at low temperatures.

[0003] It is reported that the addition of antifreeze agents such as ethylene glycol, glycerol and sorbitol can significantly improve the antifreeze property of the gel, and various low-temperature resistant functional organic hydrogels have been successfully prepared. For example, by covalently cross-linking acrylamide and acrylic acid monomers in a glycerol-water binary solvent system and combining them with polydopamine-modified carbon nanotubes, Han et al. successfully prepared an antifreeze conductive hydrogel. Thanks to the strong hydrogen bonding between glycerol and water molecules, the water molecules are firmly anchored in the polymer network, and the hydrogel still has excellent antifreeze performance and long-term stability at -20°C, verifying the feasibility of introducing glycerol as an antifreeze agent into the hydrogel. [L. Han, K. Z. Liu, M. H. Wang, K. F. Wang, L. M. Fang, H. T. Chem, J. Zhou, X. Lu, Mussel-Inspired Adhesive and Conductive Hydrogel with Long-Lasting Moisture and Extreme Temperature Tolerance, Advanced Functional Materials 28(3)(2018)1704195]. In order to further improve the electrochemical performance of gel electrolytes at low temperatures, Zhi et al. [2] proposed an antifreeze double cross-linked gel electrolyte based on ethylene glycol aqueous anionic polyurethane acrylate and PAM, in which the hydroxyl groups of ethylene glycol are covalently bonded to the isocyanate groups. This double cross-linked hydrogel electrolyte has excellent ionic conductivity (14.5 mS cm) at low temperatures (-20 °C). -1 ) and 226mAh·g -1 [FNMo, GJLiang, QQMeng, ZXLiu, HFLi, J.Fan, CYZhi, A flexible rechargeable aqueous zinc manganese-dioxide battery working at -20℃, Energy & Environmental Science 12(2)(2019)706-715]. However, the synthesis conditions of the hydrogel electrolyte in this study were strict and needed to be carried out under a nitrogen atmosphere.

[0004] Based on the above, the present invention provides a convenient and simple method for preparing a nanofiber-based composite hydrogel electrolyte with antifreeze function, which still has good flexibility in a low-temperature environment, and the zinc ion battery using the electrolyte can still maintain a high discharge capacity and electrochemical stability at -20°C. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that aqueous zinc ion batteries cannot work normally under low temperature environment, and provide a method for preparing a nanofiber-based antifreeze hydrogel electrolyte membrane for low-temperature aqueous zinc ion batteries. The composite hydrogel electrolyte prepared by the method can effectively improve the ion transmission rate of aqueous zinc ion batteries under cold conditions, and effectively alleviate the dissolution of metal elements in manganese and vanadium-based positive electrode materials in water, thereby improving the cycle stability and electrochemical performance of the overall battery.

[0006] The purpose of the present invention can be achieved by the following scheme:

[0007] A method for preparing a nanofiber-based antifreeze composite hydrogel electrolyte for a zinc ion battery, characterized in that it comprises the following steps:

[0008] (1) Preparation of organic polymer nanofiber membrane: 100-300 parts of polymer are dissolved in 700-900 parts of solvent to prepare spinning solution, and nanofiber membrane is prepared under electrospinning parameters of voltage 10-40 kV and receiving distance 10-30 cm;

[0009] (2) Composite of polymer / zinc oxide nanofiber membrane: The nanofiber membrane prepared in the above step (1) is immersed in a Zn(Ac)2 solution, and then subjected to hydrothermal treatment in a reactor at 100-240°C to obtain a polymer / zinc oxide composite nanofiber membrane;

[0010] (3) Loading of antifreeze hydrogel electrolyte: Add polymer monomer, zinc salt, 20-100 parts of antifreeze agent and 0.02-0.3 parts of cross-linking agent into deionized water, heat and stir at 50-100°C for 1-8h to obtain a colorless and transparent solution, then place the polymer / zinc oxide composite nanofiber membrane prepared in the above step (2) in a mold and fill the colorless and transparent solution on both sides of the membrane, then place it in a refrigerator and freeze-thaw for 2-5 times to obtain a nanofiber-based antifreeze hydrogel electrolyte.

[0011] Furthermore, the polymer in step (1) is one or more of poly(m-phenylene isophthalamide), polyamide, polyvinyl alcohol, polyurethane, polyvinyl pyrrolidone, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyimide, or a combination thereof;

[0012] Furthermore, the solvent in step (1) is one or more combinations of N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, dimethyl sulfoxide, cyclohexane, isobutanol, dichloromethane, toluene, and ethyl acetate.

[0013] Furthermore, the polymer monomer in step (3) includes one or more combinations of polyvinylidene fluoride, vinylidene fluoride hexafluoropropylene copolymer, polyethylene oxide, polypropylene, polymethyl methacrylate, polyacrylonitrile, and polyvinyl alcohol;

[0014] Furthermore, the zinc salt in step (3) is a combination of one or more of zinc acetate, zinc sulfate, zinc perchlorate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethylsulfonyl)imide.

[0015] Furthermore, the antifreeze agent in step (3) includes one or a combination of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, ethylene glycol butyl ether, propylene glycol butyl ether, ethylene glycol butyl ether acetate, formamide, and sodium acetate.

[0016] Furthermore, the crosslinking agent in step (3) is one or a combination of NN′-methylenebis(acrylamide), divinylbenzene, 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, 1,4-butanediol diacrylate, and ethylene glycol dimethacrylate.

[0017] Compared with the prior art, the present invention has the following advantages and gain effects:

[0018] Compared with the traditional hydrogel electrolyte, the nanofiber membrane combined with the electrospun membrane and zinc oxide in the present invention can effectively improve the mechanical properties of the gel electrolyte, increase the ion transmission channel, and accelerate the ion transmission rate. The antifreeze hydrogel electrolyte can effectively solve the side reaction problems such as zinc dendrites, corrosion and passivation, thereby improving the electrochemical performance and safety of aqueous zinc ion batteries. Among them, the addition of antifreeze causes the hydrogen bonds to interact strongly with water molecules, thereby destroying the hydrogen bonds between water molecules, achieving the effect of hindering the formation of ice crystals and lowering the freezing point. Therefore, the combination of inorganic composite diaphragm and antifreeze gel electrolyte can better improve the safety, water retention, stability and electrochemical performance of aqueous zinc ion batteries, and provide a more effective strategy for the flexible wearable field of aqueous zinc ion batteries in low temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the macroscopic morphology of the nanofiber-based antifreeze composite hydrogel electrolyte obtained in Example 1.

[0020] Figure 2 This is the microscopic morphology of the nanofiber-based antifreeze composite hydrogel electrolyte obtained in Example 1.

[0021] Figure 3 The tensile stress-strain curves of the nanofiber-based antifreeze composite hydrogel electrolyte obtained in Example 1 at different temperatures.

[0022] Figure 4 The long cycle performance of the nanofiber-based antifreeze composite hydrogel electrolyte obtained in Example 1 at different temperatures.

[0023] Figure 5This is a flow chart for the preparation of the nanofiber-based antifreeze composite hydrogel electrolyte obtained in Example 1. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] PMIA was added to DMAc solvent and stirred for 6 hours to prepare a PMIA electrospinning solution with a mass fraction of 15%. Subsequently, the PMIA spinning solution was transferred to a 20 mL pipette. The inner diameter of the spinning needle was 0.45 mm. The bottom of the pipette was connected to a microinjection pump through a catheter. The needle was connected to a high-voltage power supply, and the spinning voltage was 30 kV. The extrusion rate of the PMIA electrospinning solution was set to 0.8 mL.h -1 , the receiving distance is 20cm. Finally, the PMIA electrospun nanofiber membrane collected on the receiving roller was placed in a vacuum oven (50℃) and dried for 24h to remove the residual solvent. The PMIA nanofiber membrane obtained in the previous step was cut into 5cm×5cm samples, and fully immersed in a culture dish containing 1.5mol / L Zn(Ac)2 solution for 24h. After being taken out and dried in the shade, it was transferred to a vacuum oven at 130℃ for 12h heat treatment to obtain a nanofiber membrane composited with zinc oxide and PMIA. 25wt% PVA and 1.5mol / L Zn(CF3SO3)2 were added to a mixed solvent of deionized water and 45wt% glycerol, and magnetically stirred for 3h at room temperature to fully swell the PVA; then it was placed in a water bath and heated and stirred at 90℃ for 6h to completely dissolve the PVA. 5 μL of 4 wt% boric acid solution was added to the PVA solution, and stirring was continued for 0.5 h; then the stirring was turned off and heating was continued for 0.5 h to eliminate the small bubbles generated during the stirring process, and a colorless and transparent PVA mixed solution was obtained. Finally, the ZnO@PMIA composite nanofiber membrane was placed in a polytetrafluoroethylene mold and the PVA mixed solution was filled on both sides of the membrane. The excess PVA was removed by scraping with a glass rod and the PVA mixed solution was immersed in the ZnO@PMIA composite nanofiber membrane. It was placed in a -20°C refrigerator and frozen for 12 h and then thawed for 6 h, and repeated three times to finally obtain a nanofiber-based antifreeze composite hydrogel electrolyte.

[0027] The macroscopic morphology of the nanofiber-based antifreeze composite hydrogel electrolyte prepared in this case is shown in Figure 1 shown.

[0028] The microscopic morphology of the nanofiber-based antifreeze composite hydrogel electrolyte prepared in this case is shown in Figure 2 shown.

[0029] The preparation process of the nanofiber-based antifreeze composite hydrogel electrolyte prepared in this case is as follows: Figure 5 shown.

[0030] The stress-strain curves of the nanofiber-based antifreeze composite hydrogel electrolyte at different temperatures were tested using an electronic fiber strength tester (YG005E). Figure 3 As shown, it can be found that its tensile properties do not change significantly with the decrease in temperature, confirming that the nanofiber-based antifreeze composite hydrogel electrolyte has good mechanical tensile properties.

[0031] The positive electrode that can react with zinc ions, the zinc negative electrode and the nanofiber-based antifreeze composite hydrogel electrolyte are assembled into the battery shell to obtain an antifreeze aqueous zinc ion battery. The long cycle performance of the aqueous zinc ion battery composed of the nanofiber-based antifreeze composite hydrogel electrolyte at different temperatures was investigated. Figure 4 As shown. At 1A·g -1 At a current density of , the zinc-ion battery can operate stably for more than 500 cycles at 10°C, and the specific capacity at the end of the cycle maintains 97.1% of the initial cycle specific capacity.

[0032] Example 2

[0033] PMIA was added to DMAc solvent and stirred for 6 h to prepare a PMIA electrospinning solution with a mass fraction of 15%. Subsequently, the PMIA spinning solution was transferred to a 20 mL pipette. The inner diameter of the spinning needle was 0.45 mm. The bottom of the pipette was connected to a microinjection pump through a catheter. The needle was connected to a high-voltage power supply, and the spinning voltage was 30 kV. The extrusion rate of the PMIA electrospinning solution was set to 0.8 mL·h -1, the receiving distance is 20cm. Finally, the PMIA electrospun nanofiber membrane collected on the receiving roller was placed in a vacuum oven (50℃) and dried for 24h to remove the residual solvent. The PMIA nanofiber membrane obtained in the previous step was cut into 5cm×5cm samples, and fully immersed in a culture dish containing 1.5mol / L Zn(Ac)2 solution for 24h. After being taken out and dried in the shade, it was transferred to a vacuum oven at 130℃ for 12h heat treatment to obtain a nanofiber membrane composited with zinc oxide and PMIA. 25wt% PVA and 1.5mol / L Zn(CF3SO3)2 were added to a mixed solvent of deionized water and 45wt% glycerol, and magnetically stirred for 3h at room temperature to fully swell the PVA; then it was placed in a water bath and heated and stirred at 90℃ for 6h to completely dissolve the PVA. 5 μL of 4 wt% boric acid solution was added to the PVA solution, and stirring was continued for 0.5 h; then the stirring was turned off and heating was continued for 0.5 h to eliminate the small bubbles generated during the stirring process, and a colorless and transparent PVA mixed solution was obtained. Finally, the ZnO@PMIA composite nanofiber membrane was placed in a polytetrafluoroethylene mold and the PVA mixed solution was filled on both sides of the membrane. The excess PVA was removed by scraping with a glass rod and the PVA mixed solution was immersed in the ZnO@PMIA composite nanofiber membrane. It was placed in a -20°C refrigerator and frozen for 12 h and then thawed for 6 h, and repeated three times to finally obtain a nanofiber-based antifreeze composite hydrogel electrolyte.

[0034] The positive electrode that can react with zinc ions, the zinc negative electrode and the nanofiber-based antifreeze composite hydrogel electrolyte are assembled into the battery shell to obtain an antifreeze aqueous zinc ion battery. -1 At a current density of , the zinc-ion battery can operate stably for more than 500 cycles at 0°C, and the specific capacity at the end of the cycle maintains 90.4% of the initial cycle specific capacity.

[0035] Example 3

[0036] PMIA was added to DMAc solvent and stirred for 6 h to prepare a PMIA electrospinning solution with a mass fraction of 15%. Subsequently, the PMIA spinning solution was transferred to a 20 mL pipette. The inner diameter of the spinning needle was 0.45 mm. The bottom of the pipette was connected to a microinjection pump through a catheter. The needle was connected to a high-voltage power supply, and the spinning voltage was 30 kV. The extrusion rate of the PMIA electrospinning solution was set to 0.8 mL·h -1, the receiving distance is 20cm. Finally, the PMIA electrospun nanofiber membrane collected on the receiving roller was placed in a vacuum oven (50℃) and dried for 24h to remove the residual solvent. The PMIA nanofiber membrane obtained in the previous step was cut into 5cm×5cm samples, and fully immersed in a culture dish containing 1.5mol / L Zn(Ac)2 solution for 24h. After being taken out and dried in the shade, it was transferred to a vacuum oven at 130℃ for 12h heat treatment to obtain a nanofiber membrane composited with zinc oxide and PMIA. 25wt% PVA and 1.5mol / L Zn(CF3SO3)2 were added to a mixed solvent of deionized water and 45wt% glycerol, and magnetically stirred for 3h at room temperature to fully swell the PVA; then it was placed in a water bath and heated and stirred at 90℃ for 6h to completely dissolve the PVA. 5 μL of 4 wt% boric acid solution was added to the PVA solution, and stirring was continued for 0.5 h; then the stirring was turned off and heating was continued for 0.5 h to eliminate the small bubbles generated during the stirring process, and a colorless and transparent PVA mixed solution was obtained. Finally, the ZnO@PMIA composite nanofiber membrane was placed in a polytetrafluoroethylene mold and the PVA mixed solution was filled on both sides of the membrane. The excess PVA was removed by scraping with a glass rod and the PVA mixed solution was immersed in the ZnO@PMIA composite nanofiber membrane. It was placed in a -20°C refrigerator and frozen for 12 h and then thawed for 6 h, and repeated three times to finally obtain an antifreeze composite hydrogel electrolyte.

[0037] The positive electrode that can react with zinc ions, the zinc negative electrode and the nanofiber-based antifreeze composite hydrogel electrolyte are assembled into the battery shell to obtain an antifreeze aqueous zinc ion battery. -1 At a current density of , the zinc-ion battery can operate stably for more than 500 cycles at -10°C, and the specific capacity at the end of the cycle maintains 83.8% of the initial cycle specific capacity.

[0038] Example 3

[0039] PMIA was added to DMAc solvent and stirred for 6 h to prepare a PMIA electrospinning solution with a mass fraction of 15%. Subsequently, the PMIA spinning solution was transferred to a 20 mL pipette. The inner diameter of the spinning needle was 0.45 mm. The bottom of the pipette was connected to a microinjection pump through a catheter. The needle was connected to a high-voltage power supply, and the spinning voltage was 30 kV. The extrusion rate of the PMIA electrospinning solution was set to 0.8 mL·h -1, the receiving distance is 20cm. Finally, the PMIA electrospun nanofiber membrane collected on the receiving roller was placed in a vacuum oven (50℃) and dried for 24h to remove the residual solvent. The PMIA nanofiber membrane obtained in the previous step was cut into 5cm×5cm samples, and fully immersed in a culture dish containing 1.5mol / L Zn(Ac)2 solution for 24h. After being taken out and dried in the shade, it was transferred to a vacuum oven at 130℃ for 12h heat treatment to obtain a nanofiber membrane composited with zinc oxide and PMIA. 25wt% PVA and 1.5mol / L Zn(CF3SO3)2 were added to a mixed solvent of deionized water and 45wt% glycerol, and magnetically stirred for 3h at room temperature to fully swell the PVA; then it was placed in a water bath and heated and stirred at 90℃ for 6h to completely dissolve the PVA. 5 μL of 4 wt% boric acid solution was added to the PVA solution, and stirring was continued for 0.5 h; then the stirring was turned off and heating was continued for 0.5 h to eliminate the small bubbles generated during the stirring process, and a colorless and transparent PVA mixed solution was obtained. Finally, the ZnO@PMIA composite nanofiber membrane was placed in a polytetrafluoroethylene mold and the PVA mixed solution was filled on both sides of the membrane. The excess PVA was removed by scraping with a glass rod and the PVA mixed solution was immersed in the ZnO@PMIA composite nanofiber membrane. It was placed in a -20°C refrigerator and frozen for 12 h and then thawed for 6 h, and repeated three times to finally obtain an antifreeze composite hydrogel electrolyte.

[0040] The positive electrode that can react with zinc ions, the zinc negative electrode and the nanofiber-based antifreeze composite hydrogel electrolyte are assembled into the battery shell to obtain an antifreeze aqueous zinc ion battery. -1 At a current density of , the zinc-ion battery can operate stably for more than 500 cycles at -20°C, and the specific capacity at the end of the cycle maintains 80.1% of the initial cycle specific capacity.

Claims

1. A method for preparing a nanofiber-based antifreeze hydrogel electrolyte for zinc ion batteries, It is characterized in that The specific steps include (1) Preparation of organic polymer nanofiber membrane: 100-300 parts of polymer are dissolved in 700-900 parts of solvent to prepare spinning solution, and nanofiber membrane is prepared under electrospinning parameters of voltage 10-40 kV and receiving distance 10-30 cm; (2) Composite of polymer / zinc oxide nanofiber membrane: The nanofiber membrane prepared in step (1) above is immersed in Zn(Ac) 2 The solution is then subjected to hydrothermal treatment in a reactor at 100-240° C. to obtain a polymer / zinc oxide composite nanofiber membrane; (3) Loading of antifreeze hydrogel electrolyte: Add polymer monomer, zinc salt, 20-100 parts of antifreeze agent and 0.02-0.3 parts of cross-linking agent into deionized water, heat and stir at 50-100°C for 1-8h to obtain a colorless and transparent solution, then place the polymer / zinc oxide composite nanofiber membrane prepared in the above step (2) in a mold and fill the colorless and transparent solution on both sides of the membrane, then place it in a refrigerator and freeze-thaw for 2-5 times to obtain a nanofiber-based antifreeze hydrogel electrolyte.

2. According to claim 1, the polymer is any one or more of poly(m-phenylene isophthalamide), polyamide, polyvinyl alcohol, polyurethane, polyvinyl pyrrolidone, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyimide; The solvent is one or more combinations of N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, dimethyl sulfoxide, cyclohexane, isobutyl alcohol, dichloromethane, toluene, and ethyl acetate; the polymer monomer includes one or more combinations of polyvinylidene fluoride, vinylidene fluoride hexafluoropropylene copolymer, polyethylene oxide, polypropylene, polymethyl methacrylate, polyacrylonitrile, and polyvinyl alcohol; The zinc salt is any one or more combinations of zinc chloride, zinc nitrate, zinc acetate, zinc sulfate, zinc perchlorate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethylsulfonyl)imide; The antifreeze agent includes one or more combinations of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, ethylene glycol butyl ether, propylene glycol butyl ether, ethylene glycol butyl ether acetate, formamide, and sodium acetate; The crosslinking agent is one or more combinations of NN′-methylenebis(acrylamide), divinylbenzene, 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane, 1,4-butanediol diacrylate, and ethylene glycol dimethacrylate.

3. A nanofiber-based antifreeze hydrogel electrolyte for aqueous zinc ion batteries according to claim 1, Features It is a combination of nanofibers and hydrogel electrolytes, with a nanofiber filling rate of 1%-90% and a durable temperature of -20℃-40℃.

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