Preparation method of zinc-air battery gel electrolyte

Abstract

The preparation method of the zinc-air battery gel electrolyte comprises the following steps: dissolving an acrylamide monomer in a mixed solution of deionized water and dimethyl sulfoxide to obtain an acrylamide solution; sequentially adding an alkaline ion solution, N, N '-methylene bisacrylamide and a persulfate initiator into the acrylamide solution, and uniformly mixing to obtain a reaction solution; and adding a catalyst into the reaction liquid, and continuously reacting for a period of time at a preset temperature to obtain the gel electrolyte. According to the preparation method, the alkaline ion solution is directly introduced into the gel preparation process, and the novel gel electrolyte with high ionic conductivity and stable mechanical property can be prepared without additional soaking, so that the technological process is remarkably simplified; the problems of uncontrollable volume expansion, non-uniform ion distribution and insufficient environmental adaptability caused by soaking of the gel electrolyte can be avoided, the performance of the gel electrolyte is improved, resource waste and cost are reduced, and a new solution is provided for large-scale production of the gel electrolyte battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a preparation method of a gel electrolyte for a zinc-air battery. Background Art

[0002] Due to advantages such as high energy density, environmental friendliness, and low cost, zinc-air batteries are widely used in fields such as portable electronic devices, electric vehicles, and energy storage systems. The battery performance largely depends on the properties of the electrolyte. As an improved form of liquid electrolyte, gel electrolyte has excellent mechanical stability, anti-leakage ability, and high ionic conductivity, and is widely used in zinc-air batteries. The preparation of traditional gel electrolytes usually uses polymer materials (such as polyvinyl alcohol, polyacrylic acid, chitosan, etc.) as the matrix, forms a three-dimensional network structure through cross-linking agents or physical and chemical modifications, and is prepared by photopolymerization or high-temperature polymerization. During the preparation process, affected by the structure and properties of the gel itself, the prepared gel needs to be immersed in an electrolyte solution such as an alkaline solution (such as KOH, NaOH) to absorb enough alkaline solution to improve conductivity. In this case, a neutral gel needs to be synthesized first, and then the alkaline solution is absorbed by the immersion method. During immersion, the polymer matrix is likely to absorb too much water or electrolyte solution, resulting in a significant expansion of the gel volume. The uncontrollable expansion of the gel volume will affect the mechanical matching of the battery components, increase the resistance at the interface between the gel and the catalyst material, and hinder ion transport, thereby affecting the structural stability and cycle life of the battery. Secondly, the traditional immersion process is difficult to ensure the uniform distribution of ions in the gel. Especially for thick gel electrolytes, the existence of an inner and outer layer ion concentration gradient will lead to insufficient local conductivity of the gel electrolyte, restricting the rate performance and discharge stability of the battery. Moreover, traditional gel electrolytes have poor stability under high temperature, high humidity, or other complex environmental conditions, and are prone to problems such as swelling failure or decline in mechanical properties, resulting in a decrease in battery stability and cycle performance attenuation; due to the long time-consuming immersion step, the feasibility of its large-scale industrial production is also limited. In addition, a large amount of electrolyte solution is required during the immersion process of traditional gel electrolytes, and the part of the electrolyte solution not absorbed by the gel is usually wasted, increasing raw material consumption and environmental burden, and also increasing the manufacturing cost. Summary of the Invention

[0003] Based on this, in view of the above deficiencies, it is necessary to provide a preparation method of a gel electrolyte for a zinc-air battery that can achieve high ionic conductivity and excellent mechanical stability without an additional immersion step.

[0004] A preparation method of a gel electrolyte for a zinc-air battery includes the following steps:

[0005] S1. Dissolve acrylamide monomers in a mixed solution of deionized water and dimethyl sulfoxide to obtain an acrylamide solution;

[0006] S2. Sequentially add an alkaline ion solution, N,N'-methylenebisacrylamide, and a persulfate initiator to the acrylamide solution and mix well to obtain a reaction solution;

[0007] S3. Add a catalyst to the reaction solution and continuously react at a preset temperature for a period of time to obtain a gel electrolyte.

[0008] In one embodiment, in the mixed solution of deionized water and dimethyl sulfoxide, the volume ratio of deionized water to dimethyl sulfoxide is 1:1.

[0009] In one embodiment, in the reaction solution, the volume ratio of dimethyl sulfoxide to the alkaline ion solution is 4:1 - 32:1, and the concentration of the alkaline ion solution is 0.1 mol / L.

[0010] In one embodiment, the mass ratio of acrylamide monomers to N,N'-methylenebisacrylamide is 1000:1.

[0011] In one embodiment, the alkaline ion solution is potassium hydroxide solution, or sodium hydroxide solution, or a mixed solution of potassium hydroxide solution and sodium hydroxide solution.

[0012] In one embodiment, the persulfate initiator is ammonium persulfate or potassium persulfate.

[0013] In one embodiment, the catalyst is tetramethylethylenediamine.

[0014] In one embodiment, in step S3, the reaction temperature is 50 - 70 °C, and the reaction time is 6 - 12 h.

[0015] In one embodiment, in step S3, the reaction temperature is 60 °C, and the reaction time is 6 h.

[0016] In one embodiment, in step S3, introduce the reaction solution added with the catalyst into a glass plate and heat and polymerize it in a forced-air oven to obtain a gel electrolyte.

[0017] Implementing the preparation method of the zinc-air battery gel electrolyte of the present invention, introducing the alkaline ionic solution directly into the gel preparation process, a new gel electrolyte with high ionic conductivity and stable mechanical properties can be obtained without an additional soaking step. It significantly simplifies the technological process of gel electrolyte preparation, can avoid problems such as uncontrollable volume expansion, uneven ion distribution, and insufficient environmental adaptability caused by gel electrolyte soaking, improves the performance of the gel electrolyte, reduces resource waste in the gel electrolyte preparation process and lowers the cost, providing a new solution for the large-scale production of gel electrolyte batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flowchart of the preparation method of the zinc-air battery gel electrolyte in an embodiment of the present invention;

[0019] Figure 2 It is a reaction block diagram of the gel electrolyte preparation process in an embodiment of the present invention;

[0020] Figure 3 It is a comparison chart of CV curves of the batteries respectively assembled with the gel electrolytes of Example 2 and Comparative Example 1 of the present invention;

[0021] Figure 4 It is a comparison chart of EIS curves of the batteries respectively assembled with the gel electrolytes of Example 2 and Comparative Example 1 of the present invention;

[0022] Figure 5 It is a comparison chart of constant current charge and discharge cycles of the batteries respectively assembled with the gel electrolytes of Example 2 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] 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 made with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0024] Please refer to Figure 1 and Figure 2 , the present invention discloses a preparation method of a zinc-air battery gel electrolyte that can achieve high ionic conductivity and excellent mechanical stability without an additional soaking step. By introducing an alkaline ionic solution into the gel preparation process, it overcomes the deficiencies caused by gel electrolyte soaking. Specifically, the preparation method of the zinc-air battery gel electrolyte in this embodiment includes the following steps:

[0025] S1. Dissolve acrylamide monomer in a mixed solution of deionized water and dimethyl sulfoxide to obtain an acrylamide solution.

[0026] In this embodiment, both deionized water and dimethyl sulfoxide (DMSO) are polar solvents. Among them, deionized water is used to adjust the concentration of dimethyl sulfoxide so that the concentration of dimethyl sulfoxide in the mixed solution meets the requirements of the polymerization reaction. Preferably, in the mixed solution of deionized water and dimethyl sulfoxide, the volume ratio of deionized water to dimethyl sulfoxide is 1:1. After dissolving the acrylamide monomer in the mixed solution of deionized water and dimethyl sulfoxide, the mixed solution needs to be stirred to make the acrylamide monomer fully dissolve in the mixed solution to form a homogeneous solution.

[0027] S2. Sequentially add an alkaline ion solution, N,N'-methylenebisacrylamide (i.e., MBAA crosslinker), and a persulfate initiator to the acrylamide solution and mix well to obtain a reaction solution.

[0028] In this embodiment, after adding the alkaline ion solution, N,N'-methylenebisacrylamide, and the persulfate initiator to the acrylamide solution, the solution needs to be continuously stirred to make the alkaline ion solution, N,N'-methylenebisacrylamide, and the persulfate initiator fully dispersed in the acrylamide solution, so that N,N'-methylenebisacrylamide can fully contact with the acrylamide monomer for the reaction to proceed. In the reaction solution, the volume ratio of dimethyl sulfoxide to the alkaline ion solution is 4:1 - 32:1, and the concentration of the alkaline ion solution is 0.1 mol / L. When the volume ratio of deionized water to dimethyl sulfoxide and the concentration of the alkaline ion solution are determined, limiting the volume ratio of dimethyl sulfoxide to the alkaline ion solution can determine the addition amounts of dimethyl sulfoxide and the alkaline ion solution in the reaction solution. Further, the mass ratio of acrylamide monomer to N,N'-methylenebisacrylamide is 1000:1.

[0029] In this embodiment, dimethyl sulfoxide is mainly used to dissolve acrylamide monomer and N,N'-methylenebisacrylamide (i.e., MBAA crosslinker, hereinafter, MBAA crosslinker is used to replace N,N'-methylenebisacrylamide) to provide a good reaction environment. In addition, dimethyl sulfoxide is also used as a functional additive to significantly enhance the solvation ability of the gel system and optimize the mechanical properties and ionic conductivity of the gel. The alkaline ion solution dissociates into metal cations and OH in the reaction solution. -Ions are used to adjust the alkaline environment of the reaction solution (system). Combining dimethyl sulfoxide with the alkaline ion solution can improve the uniformity of the distribution of the alkaline ion solution in the gel, effectively reduce the side reaction rate on the surface of the zinc electrode, and improve the cycle stability of the zinc-air battery. The persulfate initiator is used to initiate the cross-linking polymerization reaction to trigger the free radical polymerization reaction of acrylamide monomers and MBAA cross-linking agents under specific conditions. In one embodiment, the alkaline ion solution is a potassium hydroxide solution, or a sodium hydroxide solution, or a mixed solution of a potassium hydroxide solution and a sodium hydroxide solution. The persulfate initiator is ammonium persulfate or potassium persulfate. Preferably, the alkaline ion solution is a potassium hydroxide solution, and the persulfate initiator is ammonium persulfate.

[0030] S3. Add a catalyst to the reaction solution and continuously react at a preset temperature for a period of time to obtain a gel electrolyte. The catalyst is used to accelerate the polymerization reaction between acrylamide and the MBAA cross-linking agent. Preferably, the catalyst is tetramethylethylenediamine. In the reaction system, tetramethylethylenediamine catalyzes the persulfate initiator to form free radicals, so that the free radicals cause the polymerization between acrylamide and the MBAA cross-linking agent, thereby forming a gel matrix that can be used for screening macromolecules. In step S3, the reaction temperature is 50 - 70 °C, and the reaction time is 6 - 12 h. Preferably, in step S3, the reaction temperature is 60 °C, and the reaction time is 6 h. Additionally, in step S3, the reaction solution with the catalyst added is introduced into a glass plate and heated and polymerized in a forced-air oven to obtain the gel electrolyte. In this way, the heat absorption area of the reaction solution is increased, thereby accelerating the formation rate of the gel electrolyte.

[0031] During the reaction process of the above system, the reaction environment is provided by dimethyl sulfoxide and the alkaline ion solution, and the cross-linking polymerization reaction of acrylamide monomers and MBAA cross-linking agents is initiated by the persulfate initiator. Specifically, the persulfate initiator decomposes into sulfate radicals under heating conditions, and its reaction formula is shown in formula (1):

[0032] S 2 O 8 2- →2SO 4 ·- (1).

[0033] The sulfate radicals can further initiate the free radical polymerization reaction of acrylamide monomers and MBAA cross-linking agents, and its reaction formulas are shown in formulas (2)-(4):

[0034] SO 4 ·- +CH 2 =CHCONH 2 →CH 2 · —CHCONH 2(2);

[0035] CH 2 · —CHCONH 2 +n(CH 2 =CHCONH 2 )→[—CH2—CHCONH 2 —] n · (3);

[0036] [—CH2—CHCONH 2 —] n · +CH 2 =CHCONHCH 2 NHCOCH=CH 2

[0037] →[—CH 2 —CHCONH 2 —CHCONHCH 2 NHCOCH—] m (4).

[0038] The final reaction formula of the reaction system can be summarized as formula (5):

[0039] nCH2=CHCONH2 + mCH2=CHCONHCH 2 NHCOCH=CH 2 → Gel (5).

[0040] The gel generated above is a cross-linked three-dimensional network structure, which can efficiently fix the alkaline electrolyte, provide continuous ion conduction channels, and at the same time ensure that the gel has good mechanical strength and chemical stability.

[0041] The preparation process of the gel electrolyte of the zinc-air battery is described below with specific examples.

[0042] Example 1

[0043] Dissolve 4 g of acrylamide in 8 ml of deionized water and 8 ml of dimethyl sulfoxide solution and stir. Subsequently, add 2 ml of 0.1 mol / L KOH solution, 4 mg of MBAA crosslinker, and 10 mg of ammonium persulfate initiator in sequence and stir for 10 min. Among them, the volume ratio of deionized water, dimethyl sulfoxide, and KOH is 4:4:1. Wait until the solution is stirred until it becomes clear. Use a pipette to drop 200 μL of tetramethylethylenediamine into the solution, and then pour the solution into a glass plate and place it in a forced-air oven for polymerization. Control the heating temperature of the oven at 70 °C and the polymerization time at 6 h. After the solution is polymerized at 70 °C for 6 h, a KOH-DMSO gel electrolyte with certain mechanical flexibility is obtained.

[0044] Example 2

[0045] Dissolve 4 g of acrylamide in 8 ml of deionized water and 8 ml of dimethyl sulfoxide solution and stir. Subsequently, add 1 ml of 0.1 mol / L KOH solution, 4 mg of MBAA crosslinker, and 10 mg of ammonium persulfate initiator in sequence and stir for 10 minutes. Among them, the volume ratio of deionized water, dimethyl sulfoxide, and KOH is 8:8:1. Wait until the solution is stirred until it becomes clear. Use a pipette to drop 200 μL of tetramethylethylenediamine into the solution, and then pour the solution into a glass plate and place it in a forced-air oven for polymerization. Control the heating temperature of the oven at 60 °C and the polymerization time at 6 h. After the solution is polymerized at 60 °C for 6 h, a KOH-DMSO gel electrolyte with certain mechanical flexibility is obtained.

[0046] Example 3

[0047] Dissolve 4 g of acrylamide in 8 ml of deionized water and 8 ml of dimethyl sulfoxide solution and stir. Subsequently, add 1 ml of 0.1 mol / L KOH solution, 4 mg of MBAA crosslinker, and 10 mg of potassium persulfate initiator in sequence and stir for 10 minutes. Among them, the volume ratio of deionized water, dimethyl sulfoxide, and KOH is 16:16:1. Wait until the solution is stirred until it becomes clear. Use a pipette to drop 200 μL of tetramethylethylenediamine into the solution, and then pour the solution into a glass plate and place it in a forced-air oven for polymerization. Control the heating temperature of the oven at 50 °C and the polymerization time at 12 h. After the solution is polymerized at 50 °C for 12 h, a KOH-DMSO gel electrolyte with certain mechanical flexibility is obtained.

[0048] Example 4

[0049] Dissolve 4 g of acrylamide in 8 ml of deionized water and 8 ml of dimethyl sulfoxide solution and stir. Subsequently, add 1 ml of 0.1 mol / L NaOH solution, 4 mg of MBAA crosslinker and 10 mg of ammonium persulfate initiator in sequence and stir for 10 minutes. Among them, the volume ratio of deionized water, dimethyl sulfoxide and KOH is 32:32:1. Wait until the solution is stirred until it becomes clear, use a pipette to drop 200 μL of tetramethylethylenediamine into the solution, and then pour the solution into a glass plate and place it in a forced-air oven for polymerization. Control the heating temperature of the oven at 60 °C and the polymerization time at 6 h. After the solution is polymerized at 60 °C for 6 h, a KOH-DMSO gel electrolyte with certain mechanical flexibility is obtained.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that during the synthesis of the gel electrolyte, KOH solution is not added. After the gel electrolyte is polymerized, the gel is immersed in 6 mol / L KOH and 0.2 mol / L (CH 3 COO) 2 Zn solution for 24 h, and the others are the same as Example 1.

[0052] For the gel electrolytes prepared in Examples 1-4 and Comparative Example 1, soft-pack batteries are assembled with metal zinc sheets as the negative electrodes respectively. Under the condition of a test current of 20 mA, the charging and discharging processes are carried out for 1 h respectively to complete the constant-current charge and discharge cycle test of the battery. The battery test results are shown in the following table:

[0053]

[0054] As can be seen from the above table, for the soft-pack batteries prepared with the gel electrolytes prepared by the method of this solution, the discharge voltage of the battery after 10 cycles is significantly higher than that of the soft-pack batteries prepared with the gel electrolytes soaked in alkali solution, and the voltage difference after 10 cycles is significantly lower than that of the soft-pack batteries prepared with the gel electrolytes soaked in alkali solution. The service life of the battery is generally higher than that of the soft-pack batteries prepared with the gel electrolytes soaked in alkali solution.

[0055] Furthermore, please refer to Figure 3 , Figure 3 shows the comparison diagram of the CV curves of the batteries assembled with the gel electrolytes of Example 2 and Comparative Example 1 respectively. It can be seen that the current density of the gel directly doped with KOH is significantly higher than that of the gel electrolyte obtained by the soaking method in the whole potential range, which indicates that the battery assembled with the gel directly doped with KOH has higher electrochemical activity; at the same time, it shows more obvious oxidation-reduction peaks, which further reveals the obvious advantages of the battery assembled with this gel in the oxidation-reduction reaction. Figure 4The figure shows the comparison chart of the EIS curves of the batteries assembled with the gel electrolytes of Example 2 and Comparative Example 1 respectively. It can be seen that in the high-frequency region, the semicircle diameter of the battery assembled with the gel electrolyte directly doped with KOH is slightly smaller than that of the battery assembled with the gel electrolyte obtained by the soaking method, and it has a lower charge transfer resistance (Rct), indicating that the electrochemical reaction interface of Example 2 has higher reaction activity; while in the low-frequency region, the straight-line slope of Example 2 is steeper, reflecting its better ion diffusion ability; in contrast, Comparative Example 1 shows higher impedance. Overall, the optimization of the gel directly doped with KOH enables the entire battery system to have better conductivity and interfacial characteristics. Figure 5 The figure shows the comparison chart of the constant current charge and discharge cycles of the batteries assembled with the gel electrolytes of Example 2 and Comparative Example 1 respectively. It can be seen that the battery assembled with the gel electrolyte directly doped with KOH provides better ion conduction ability and a stable interfacial structure, thereby reducing the polarization effect and significantly improving the cycle performance of the battery.

[0056] Implementing the preparation method of the gel electrolyte for the zinc-air battery of the present invention, introducing the alkaline ion solution directly into the gel preparation process, a new gel electrolyte with high ion conductivity and stable mechanical properties can be obtained without an additional soaking step. It significantly simplifies the technological process of gel electrolyte preparation, can avoid problems such as uncontrollable volume expansion, uneven ion distribution, and insufficient environmental adaptability caused by gel electrolyte soaking, improves the performance of the gel electrolyte, reduces resource waste in the gel electrolyte preparation process, and lowers the cost, providing a new solution for the large-scale production of gel electrolyte batteries.

[0057] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0058] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A method for preparing a zinc-air battery gel electrolyte, characterized in that: The following steps are involved: S1, dissolving acrylamide monomer in a mixture of deionized water and dimethyl sulfoxide to obtain an acrylamide solution; S2, sequentially adding an alkaline ion solution, N,N'-methylenebisacrylamide, and a persulfate initiator to the acrylamide solution and mixing them to obtain a reaction solution; S3. Add a catalyst to the reaction solution and continue the reaction at a preset temperature for a period of time to obtain a gel electrolyte.

2. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: In the mixed solution of deionized water and dimethyl sulfoxide, the volume ratio of deionized water to dimethyl sulfoxide is 1:

1.

3. The method for preparing a zinc-air battery gel electrolyte according to claim 2, characterized in that: In the reaction solution, the volume ratio of dimethyl sulfoxide to the alkaline ion solution is 4:1-32:1, and the concentration of the alkaline ion solution is 0.1 mol / L.

4. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: The mass ratio of acrylamide monomer to N,N'-methylenebisacrylamide is 1000:

1.

5. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: The alkaline ion solution is a potassium hydroxide solution, a sodium hydroxide solution, or a mixture of a potassium hydroxide solution and a sodium hydroxide solution.

6. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: The persulfate initiator is ammonium persulfate or potassium persulfate.

7. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: The catalyst is tetramethylethylenediamine.

8. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: In step S3, the reaction temperature is 50-70° C. and the reaction time is 6-12 h.

9. The method for preparing a zinc-air battery gel electrolyte according to claim 8, characterized in that: In step S3, the reaction temperature is 60° C. and the reaction time is 6 h.

10. The method for preparing a zinc-air battery gel electrolyte according to claim 1, characterized in that: In step S3, the reaction solution to which the catalyst is added is introduced into the glass plate and heated and polymerized in a forced air oven to obtain a gel electrolyte.

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