A method for improving the adhesion between a hydrogel electrolyte and an electrode interface

Abstract

The present invention discloses a method for improving the interfacial adhesion between a hydrogel electrolyte and an electrode. The preparation method is as follows: The cathode material MXene / AgNWs&BC prepared by vacuum filtration film formation and the hydrogel electrolyte PAA-Fe synthesized by thermal polymerization 3+ -CS(PF-C) and the flexible zinc anode (Zn / CC) obtained by electrochemical deposition are bonded together in a stacked manner, and then immersed in an ammonium chloride and zinc chloride salt solution to prepare a flexible zinc-ion hybrid supercapacitor. Due to the presence of chloride ions and ammonium ions, the Hofmeister effect occurs in the polymer chitosan (CS) chains in the hydrogel electrolyte, resulting in the precipitation and folding of chitosan, and the hydrogel electrolyte PF-C is converted into PAA-Fe 3+ -CS / NH4Cl+ZnCl2 (PF-C / NZ), and its interfacial adhesion with the electrode increases. And by adding different contents of chitosan, the adhesion is changed. Therefore, the flexible zinc-ion hybrid supercapacitor can avoid energy loss caused by damage to the external environment due to bending and exhibits excellent mechanical durability.

Description

Technical Field

[0001] The present invention belongs to flexible energy storage devices, of the type of hybrid supercapacitors, and more particularly relates to how to improve its electrochemical performance by adjusting the adhesion between the electrolyte and the electrode interface. Background Art

[0002] Portable and wearable energy storage devices have received close attention. However, traditional energy storage devices, such as button batteries, cylindrical batteries, etc., which have a fixed shape and are not flexible, cannot meet the requirements of flexible wearability. At present, although lithium-ion batteries have a high energy density and mature manufacturing processes, making them widely used in fields such as smartphones and automobiles, they have certain safety hazards due to the leakage of organic electrolyte solutions under certain conditions, and they are expensive.

[0003] Metallic zinc is abundant on the earth, has a relatively high theoretical capacity, and its commonly used electrolyte is an aqueous electrolyte with high safety, and it can be worn without safety problems. Therefore, zinc-based energy storage devices have strong attraction in flexible wearable devices. At the same time, the interfacial adhesion between the hydrogel electrolyte and the electrode material is also extremely important, which is an important factor to ensure that the flexible wearable energy storage device can still continue to work after experiencing multiple mechanical deformations. However, in the past, flexible sandwich-type batteries were prone to separation and detachment after multiple bends due to the weak and loose bonding between the electrode and the electrolyte, resulting in their inability to work properly and reducing the application of flexible batteries in real life. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for improving the adhesion between the hydrogel electrolyte and the electrode interface, so that the flexible wearable device has excellent electrochemical performance and mechanical durability at the same time, not only has a high areal capacitance and energy density, but can also withstand damage and bending in daily life and still continue to work.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A method for improving the adhesion between the hydrogel electrolyte and the electrode interface, comprising the following steps:

[0007] (1) Preparation of the hydrogel electrolyte:

[0008] 7 mg of N,N'-methylenebisacrylamide and 0.1 g of ferric chloride hexahydrate were added to 5 - 20 mL of acrylic acid solution. 0 - 1 g of chitosan was uniformly dissolved in 10 - 50 mL of deionized water to form a precursor solution. Subsequently, the chitosan aqueous solution was poured into the previously prepared acrylic acid mixed solution, and nitrogen was introduced to remove oxygen in the solution. 0.07 g of initiator ammonium persulfate and 10 μL of catalyst tetramethylethylenediamine were added to the above solution. The bubbles in the solution were removed by ultrasonic treatment, and then the obtained solution was poured into a customized mold. It was placed in an oven and heated at 50 - 70 °C for 1 - 4 h to obtain the target product PAA-Fe 3+ -CS(PF-C); Different PF-Cs were prepared by changing the CS doping content to 0 g, 0.25 g, 0.5 g, 0.75 g, and 1 g X ;

[0009] (2) Preparation of MXene / AgNWs&BC cathode material:

[0010] Mix the AgNW S colloidal solution (1 mg / mL, 10 - 30 mL) with the BC solution (2 mg / mL, 10 - 30 mL), and add the MXene suspension (3 mg / mL, 10 - 30 mL) to the AgNW S &BC mixed solution under stirring, and continue stirring for 20 min; Subsequently, a film was prepared by vacuum filtration. It was placed on a hot plate at 40 °C and dried for 5 h. After drying, the hybrid film was torn off from the filter membrane, and the cathode material MXene / AgNWs&BC we needed was successfully prepared;

[0011] (3) Preparation of flexible zinc anode (Zn / CC):

[0012] The flexible zinc anode was prepared by electrochemical deposition using carbon cloth as the substrate; First, the carbon cloth and zinc sheet were cut into the required size (2.5 cm * 1.5 cm) with a laser cutter; Then, it was stirred on a magnetic stirrer to prepare the required electroplating solution (1 M ZnSO 4 ·7H 2 O); The carbon cloth was used as the working electrode and the zinc sheet as the reference electrode; On the LAND 2001A battery test system, by the constant current method, electroplating was carried out at a current density of 5 mA / cm 2 for 1 - 4 h; Subsequently, it was placed in an oven for drying, and the flexible zinc anode (Zn / CC) we needed could be obtained. ;

[0013] (4) Preparation of flexible zinc ion hybrid supercapacitor with high electrochemical and mechanical durability:

[0014] The cathode material MXenen / AgNWs&BC, PF-C X The hydrogel and the anode material carbon cloth electroplated with zinc are processed into the required sizes and tightly bonded together to form a flexible zinc-ion hybrid supercapacitor. Subsequently, it is placed in NH 4 Cl + ZnCl 2 for immersion treatment. The adhesion between the PF-C x hydrogel electrolyte and the electrode interface is enhanced, and it is converted into PF-C x / NZ hydrogel electrolyte.

[0015] Preferably, the volume of the acrylic acid solution taken in step (1) is 10 mL.

[0016] Preferably, the added content of chitosan in step (1) is 0.75 g. However, we also explored different chitosan addition amounts, such as 0 g, 0.25 g, 0.5 g, 0.75 g, 1 g, to explore and compare their performances.

[0017] Preferably, the volume of deionized water in step (1) is 30 mL.

[0018] Preferably, the temperature set in the oven in step (1) is 60 °C, and the heat preservation time is 3 h.

[0019] Preferably, the required volumes of AgNW S , BC, and MXene in step (2) are all 15 mL.

[0020] Preferably, the electroplating time in step (3) is 2 h.

[0021] Preferably, in step (3), the concentration of NH 4 Cl is 2.5 mol / L, the concentration of ZnCl 2 is 0.5 mol / L, and the immersion time is 3 h.

[0022] Compared with the existing technologies, the present invention has the following beneficial effects:

[0023] The present invention assembles the PF-C solid hydrogel prepared by a simple thermal polymerization reaction with the cathode material MXene / AgNWs&BC and the flexible zinc anode to form a sandwich-type device. When it is immersed in the prepared mixed solution of ammonium chloride and zinc chloride, due to the Hofmeister effect, the adhesion at the electrode / electrolyte interface is changed, and the electrochemical performance is improved. By changing the addition content of chitosan in the hydrogel electrolyte, we further regulate its interfacial adhesion energy, and further improve the interfacial resistance and energy density. This also solves the problems existing in the daily use of flexible sandwich-type zinc-ion hybrid supercapacitors in wearable devices. The specific advantages are listed as follows:

[0024] (1) Through simple immersion, the Hofmeister effect occurs. This causes the chitosan polymer chains to bend and precipitate, improving the interfacial adhesion between the electrode material and the electrolyte, making the combination closer, reducing the interfacial charge transfer resistance, and enhancing the electrochemical performance.

[0025] (2) Different addition contents of chitosan (CS) result in changes in its interfacial adhesion and charge transfer resistance. By changing the addition amount of CS, we further improve its electrochemical performance.

[0026] (3) Due to the tight adhesion and firm contact between the electrode and the electrolyte, after destructive experiments such as hammering, needle pricking, and repeated bending, it can still effectively and continuously supply power without obvious capacity loss. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the flexible zinc-ion hybrid supercapacitor assembled in the present invention;

[0028] Figure 2 is an optical photograph of the contact between the hydrogel electrolyte and the anode and cathode before and after immersion and a comparison diagram of the adhesion measured by a 90° peeling experiment;

[0029] Figure 3 is a comparison of the adhesion measured by a 90° peeling experiment of the hydrogels with different CS addition amounts in the present invention, and a comparison diagram of the constant current charge-discharge performance of the assembled flexible zinc-ion hybrid supercapacitor at a current density of 0.5 mA cm -2 current density;

[0030] Figure 4 is a cycling diagram of the flexible zinc-ion hybrid supercapacitor assembled with the optimal ratio of 0.75 g of chitosan in the present invention;

[0031] Figure 5 is the FZHS assembled in the present invention after different degrees of destructive experiments, at 1.5 mA cm -2Comparison chart of constant current charge-discharge curves and capacity retention rate (hammer test, needle puncture test, bending test).

[0032] In the figure: 1 is the flexible zinc anode (Zn / CC); 2 is the hydrogel electrolyte; 3 is the Mxene / AgNWs&BC cathode. Specific implementation mode

[0033] The technical solutions of the specific embodiments of the present invention will be clearly and completely described and elaborated below.

[0034] A method for improving the adhesion between the hydrogel electrolyte and the electrode interface mainly includes the following steps:

[0035] 1. Preparation of hydrogel electrolyte

[0036] 7 mg of N,N'-methylenebisacrylamide and 0.1 g of ferric chloride hexahydrate were added to 10 mL of acrylic acid solution, and 0.75 g of chitosan was uniformly dissolved in 30 mL of deionized water as a precursor solution; then the uniformly mixed chitosan aqueous solution was poured into the previously prepared acrylic acid mixed solution, and N 2 was introduced into it, aiming to remove O in the solution 2 . Then 0.07 g of initiator ammonium persulfate and 10 μL of catalyst tetramethylethylenediamine were added thereto (the solution was always in a stirred state); the solution was ultrasonically treated for 15 min to remove the bubbles, and then the obtained solution was poured into the custom-made mold; it was placed in an oven and heated at 70 °C for 6 h to obtain the target product PF-C; different contents of PAA-Fe 3+ -CS X (PF-C X ) hydrogels: Using the above method, different PF-Cs were prepared by changing the CS doping content to 0 g, 0.25 g, 0.5 g, 0.75 g, and 1 g X ;

[0037] 2. Preparation of MXene / AgNWs&BC cathode material

[0038] The AgNM colloidal solution (1 mg / mL, 15 mL) was mixed with the BC solution (2 mg / mL, 15 mL), and the Mxene suspension (3 mg / mL, 15 mL) was added to the AgNWS&BC mixed solution under stirring, and stirring was continued for 20 min. Then, a film was prepared by vacuum filtration. It was placed on a hot plate at 40 °C and dried for 5 h. After drying, the hybrid film was torn off from the filter membrane, and the required cathode material MXene / AgNWs&BC was successfully prepared;

[0039] 3. Preparation of flexible zinc anode (Zn / CC)

[0040] The flexible zinc anode is prepared by electrochemical deposition with carbon cloth as the substrate. First, the carbon cloth and zinc sheet are cut into the required size (2.5 cm * 1.5 cm) using a laser cutting machine. Then, it is stirred on a magnetic stirrer to prepare the required electroplating solution (1M ZnSO 4 ·7H 2 O). The carbon cloth serves as the working electrode and the zinc sheet serves as the reference electrode. On the LAND 2001A battery test system, electroplating is carried out at a current density of 5 mA cm -2 for 2 h by the constant current method. Subsequently, it is dried in an oven to obtain the required flexible zinc anode (Zn / CC);

[0041] 4. Preparation of a flexible zinc-ion hybrid supercapacitor with high electrochemical and mechanical durability

[0042] The above-prepared positive electrode material MXene / AgNWs&BC, hydrogel electrolyte PF-C x , and negative electrode material Zn / CC are adhesively bonded together from top to bottom in a stacked manner (the contact area between the gel electrolyte and the electrode is 2 cm 2 , 2 cm long and 1 cm wide). Subsequently, it is immersed in a mixed solution of 2.5 mol / L NH 4 Cl and 0.5 mol / L ZnCl 2 . The Hofmeister effect occurs during soaking for 3 h, improving the interfacial adhesion between the electrode material and the electrolyte, and a sandwich-type flexible zinc-ion hybrid supercapacitor is obtained.

[0043] Result analysis

[0044] From Figure 1 is a schematic diagram of the assembled flexible zinc-ion hybrid supercapacitor. Adopting a sandwich configuration, the electrode material is directly adhesively bonded to the gel electrolyte. Figure 2 It is demonstrated that compared with the unsoaked PF-C electrolyte, the PF-C / NZ hydrogel electrolyte obtained after soaking combines with the electrode material and both have stronger adhesion. From this, it can be seen that the generation of the Hofmeister effect enhances the adhesion at the interface between the hydrogel and the electrode. Figure 3 It is verified that the hydrogel electrolytes prepared by adding different amounts of chitosan have different adhesions, and the flexible zinc-ion hybrid supercapacitor prepared with the addition amount of chitosan having the best adhesion has the best electrochemical performance. This indicates that the interfacial adhesion can be regulated by changing the addition amount of chitosan, and the stronger the adhesion, the better the electrochemical performance. The flexible zinc-ion hybrid supercapacitor prepared by the present invention with the optimal proportion of chitosan addition amount has excellent cycling performance( Figure 4As shown, when it is subjected to various external damages, such as hammering, needle pricking, bending, etc., it can still work normally without obvious capacity loss. Figure 5 As shown.

[0045] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0046] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the adhesion between a hydrogel electrolyte and an electrode interface, characterized in that, the specific preparation process includes the following steps: (1) Preparation of the hydrogel electrolyte: 7 mg of N,N'-methylenebisacrylamide and 0.1 g of ferric chloride hexahydrate were added to 5 - 20 mL of acrylic acid solution. 0 - 1 g of chitosan was uniformly dissolved in 10 - 50 mL of deionized water to prepare a precursor solution. Subsequently, the chitosan aqueous solution was poured into the previously prepared acrylic acid mixed solution, and nitrogen was introduced to remove oxygen in the solution. 0.07 g of initiator ammonium persulfate and 10 μL of catalyst tetramethylethylenediamine were added to the above solution. The bubbles in the solution were treated by ultrasonic treatment, and then the obtained solution was poured into a customized mold. It was placed in an oven and heated at 50 - 70 °C for 1 - 4 h to obtain the target product PAA-Fe 3+ -CS(PF-C); By changing the CS doping content to 0 g, 0.25 g, 0.5 g, 0.75 g, 1 g, different PF-Cs were prepared X ; (2) Preparation of the MXene / AgNWs&BC cathode material: Mix the AgNW S colloidal solution (1 mg / mL, 10 - 30 mL) with the BC solution (2 mg / mL, 10 - 30 mL), and add the MXene suspension (3 mg / mL, 10 - 30 mL) to the mixed solution of AgNW S & BC under stirring, and continue stirring for 20 min; then, prepare a film by vacuum filtration, place it on a heating plate at 40 °C and dry for 5 h. After drying, tear the hybrid film off the filter membrane to successfully prepare the cathode material MXene / AgNWs&BC we need; (3) Preparation of the flexible zinc anode (Zn / CC): The flexible zinc anode is prepared by electrochemically depositing on a carbon cloth substrate; first, the carbon cloth and zinc sheet are cut into the required size (2.5 cm * 1.5 cm) with a laser cutting machine, and then stirred on a magnetic stirrer to prepare the required electroplating solution (1M ZnSO 4 ·7H 2 O); the carbon cloth serves as the working electrode and the zinc sheet serves as the reference electrode; on the LAND 2001A battery test system, by the constant current method, electroplating is carried out at a current density of 5 mA / cm 2 for 1 - 4 h; subsequently, it is placed in an oven for drying to obtain the flexible zinc anode (Zn / CC) we need; (4) Preparation of a flexible zinc-ion hybrid supercapacitor with high electrochemical and mechanical durability: The cathode material MXenen / AgNWs&BC, PF-C X The hydrogel and the anode material carbon cloth electroplated with zinc are processed into the required sizes and tightly bonded together to form a flexible zinc-ion hybrid supercapacitor, which is then placed in NH 4 Cl + ZnCl 2 The mixture solution for immersion treatment enhances the adhesion between the PF-C hydrogel electrolyte and the electrode interface and converts it into a PF-C / NZ hydrogel electrolyte.

2. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, in the step (1), the volume of the acrylic acid solution taken is 10 mL.

3. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, in the step (1), the addition content of chitosan is 0.75 g; at the same time, we also explore and compare its performance by adding different chitosan contents, such as 0 g, 0.25 g, 0.5 g, 0.75 g, 1 g.

4. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, in the step (1), the volume of deionized water is 30 mL.

5. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, in the step (1), the temperature set in the oven is 60 °C, and the heat preservation time is 3 h.

6. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, In the step (2), the required volumes of AgNW S , BC, and MXene are all 15 mL.

7. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, in the step (3), the electroplating time is 2 h.

8. The method for improving the adhesion between a hydrogel electrolyte and an electrode interface according to claim 1, characterized in that, In the step (4), the concentration of NH 4 Cl is 2.5 mol / L, and the concentration of ZnCl 2 is 0.5 mol / L. The soaking time is 3 h.

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