A micro three-dimensional porous electrode prepared based on inkjet printing technology and application thereof

Abstract

This invention discloses a micro-three-dimensional porous electrode fabricated using inkjet printing technology and its applications, belonging to the field of wearable electronics and their fabrication. The fabrication of the micro-three-dimensional porous electrode in this invention includes: preparing rGO / Mxene composite powder, dispersing it in water, adding surfactants, thickeners, and defoamers to obtain an rGO / Mxene composite ink suitable for inkjet printing; printing interdigitated electrodes on a flexible substrate using inkjet printing technology, and then placing the interdigitated electrodes in a directional freezing device. The temperature gradient at both ends of the electrodes is controlled by adjusting the distance between the interdigitated electrodes and the cooling stage, resulting in an ordered arrangement of micro-three-dimensional porous electrodes. This micro-three-dimensional porous electrode has a large specific surface area and high ion transport efficiency. The micro-three-dimensional porous electrode on a flexible substrate can adapt to human movement by bending and twisting, exhibiting certain mechanical flexibility and stability, and has wide applications in smart wearable products.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of micro three-dimensional porous electrode based on inkjet printing technology preparation and its application, belong to wearable electronics and its preparation field. BACKGROUND

[0002] Wearable electronic products have wide and important applications in various fields such as medical monitoring, sensors and Internet of Things. However, traditional batteries, supercapacitors and other energy storage devices are too bulky and cannot be bent, which cannot be integrated with wearable devices and systems. In contrast, flexible micro-supercapacitors (MSCs) with high power output, fast charge and discharge rate, and long cycle life are receiving increasing attention and are considered as the ideal power source for the next generation of wearable electronic systems.

[0003] Compared with the traditional sandwiched supercapacitor multilayer structure, which is bulky, prone to short circuit and complex process, people prefer interdigital electrodes that can be easily integrated with other functional electronic devices / systems. The unique microscale structure of interdigital electrodes is very challenging to manufacture. So far, various methods have been developed to prepare fine interdigital electrodes, although these methods have their unique advantages, but the process usually involves photolithography, oxygen plasma etching, laser etching, high pressure pressing and mask-assisted strategies, which are complex, high cost and difficult to mass production. Therefore, there is an urgent need to develop a simple and economical method to construct high-performance interdigital electrodes.

[0004] Inkjet printing can easily manufacture micro-nano devices on non-planar or flexible substrates by dispersing active materials into a suspension, which is simple, low cost, high patterning capability and large area manufacturing, showing great prospects in manufacturing electronic devices. Reduced graphene oxide (rGO) has important materials in various fields due to its excellent physical and chemical properties, such as high flexibility, high specific surface area and excellent stability, making rGO one of the best materials in the energy storage field. However, rGO has poor mechanical properties and low conductivity, which limits its application in flexible energy storage. Transition metal carbide (Ti3C2T x , Mxenes) is a new type of two-dimensional (2D) material with excellent flexibility, excellent mechanical properties, high conductivity, large specific surface area, etc., which is a good choice to improve the performance of rGO. However, the structure of inkjet printed MSCs is dense, with small specific surface area and low ion diffusion efficiency, resulting in relatively low electrochemical performance. At the same time, two-dimensional materials such as rGO and Mxene are prone to aggregation and restacking during solvent evaporation.

[0005] Therefore, it is urgent to develop a micro three-dimensional porous electrode with flexibility, high conductivity, high specific capacity, high specific surface area and high processability. SUMMARY

[0006] In view of the defects and deficiencies of the prior art, the present application provides a micro three-dimensional porous electrode prepared based on inkjet printing technology and its application. The micro three-dimensional porous electrode has high conductivity, high specific capacity, high specific surface area and high processability. The flexible substrate of the micro three-dimensional porous electrode can be bent and twisted to adapt to human movement, and has a wide application prospect in the field of wearable electronic products.

[0007] The first object of the present application is to provide a method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, which comprises the following steps:

[0008] (1) preparing rGO / Mxene composite powder;

[0009] (2) ultrasonic dispersion of the rGO / Mxene composite powder prepared in step (1) in water, addition of a surfactant, a thickening agent and a defoaming agent, ultrasonic stirring and mixing to obtain rGO / Mxene composite ink suitable for inkjet printing;

[0010] (3) printing an interdigital electrode on a flexible substrate by using inkjet printing technology, vertically fixing the flexible substrate carrying the interdigital electrode on an iron stand in a directional freezing device, controlling the distance between the interdigital electrode and the cold source for freezing, and then freeze-drying in a freezing machine to obtain an ordered micro three-dimensional porous electrode.

[0011] In one embodiment, the preparation of rGO / Mxene composite powder in step (1) specifically comprises the following steps:

[0012] Polydimethyl diallyl ammonium chloride (PDDA) is added dropwise to the Mxene dispersion liquid and ultrasonic stirring is performed, followed by centrifugation and collection of the precipitate. The modified Mxene is ultrasonic dispersed in water, then added dropwise to the rGO dispersion liquid, mixed and stirred, centrifuged, washed with water, and the precipitate is collected and freeze-dried to obtain the rGO / Mxene composite powder.

[0013] In one embodiment, the mass concentration of PDDA is 0.1-5wt%, the concentration of Mxene dispersion liquid is 1-2mg / mL, and the volume ratio of PDDA to Mxene dispersion liquid is 1:10-1:50.

[0014] In one embodiment, the ultrasonic stirring time is 6-24h.

[0015] In one embodiment, the concentration of the rGO dispersion liquid is 0.5-2mg / mL, and the mass ratio of rGO to modified Mxene is 1:1-9:1.

[0016] In an embodiment, the stirring mixing time is 1-4 h.

[0017] In an embodiment, the solid content of rGO / Mxene in the rGO / Mxene composite ink of step (2) is 1-5 wt%.

[0018] In an embodiment, the surfactant of step (2) comprises one or more of fatty alcohol polyoxyethylene ether (AEO), alkyl phenol polyoxyethylene ether (TX), polyethylene glycol octylphenyl ether Triton X100, polyol polyoxyethylene ether fatty acid ester.

[0019] In an embodiment, the amount of surfactant of step (2) is 0.1-1 wt% based on the total amount of the composite ink.

[0020] In an embodiment, the thickening agent of step (2) is one or more of ethylene glycol, 1,2-propanediol, and glycerol.

[0021] In an embodiment, the amount of thickening agent of step (2) is 1-10 wt% based on the total amount of the composite ink.

[0022] In an embodiment, the defoaming agent of step (2) is one or more of MD-4, DF69, DF104, DF126, and DF3400.

[0023] In an embodiment, the amount of defoaming agent of step (2) is 0.05-0.2 wt% based on the total amount of the composite ink.

[0024] In an embodiment, the flexible substrate of step (3) comprises one or more of plasma-treated polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polyimide (PI), polyethylene (PE), polyurethane (PU), and A4 paper, polyester, cotton cloth.

[0025] In an embodiment, the interdigital electrode of step (3) is divided into A, B, and C parts, wherein the length of A part is 0.5-1 cm and the width is 2-6 mm; the length of B part is 7.5-26 mm and the width is 1-3 mm; the length of the "finger part" of C part is 1-2 cm and the width is 0.5-1 mm, and the spacing between the four fingers is 1.5-6 mm; the spacing between B part and the "finger part" of C part is 0.5-2 mm, and the thickness of the electrode is 20-100 μm.

[0026] In an embodiment, the directional freezing device of step (3) is sequentially from top to bottom: a heat preservation cover, a heat preservation box body, a fixed iron stand and a cold source device; wherein the distance between the interdigital electrode and the cold source is 1-6 cm, and the time is 2-5 min; by controlling the distance between the interdigital electrode and the cold source device, the temperature gradient at both ends of the electrode can be controlled, and the temperature difference is 10±2 ℃ / cm; the distance freezing temperature interval is-140 ℃--80 ℃.

[0027] In an embodiment, the cold source is liquid nitrogen.

[0028] A second object of the present application is to provide a micro three-dimensional porous electrode prepared by the above-mentioned method.

[0029] A third object of the present application is to provide an application of the above-mentioned micro three-dimensional porous electrode in the preparation of intelligent wearable products.

[0030] The beneficial effects of the present application are:

[0031] The present application provides a method for preparing a micro three-dimensional porous electrode based on inkjet printing technology. The micro three-dimensional porous electrode has a large specific surface area and high ion transmission efficiency. The micro three-dimensional porous electrode with a flexible substrate can adapt to human motion and be bent and twisted, and has certain mechanical flexibility and stability. The specific advantages are as follows:

[0032] 1) The present application vertically places the inkjet printed interdigital electrode in a directional freezing device to prepare a micro porous electrode with directional arrangement. The principle is to use the oriented ice crystals in the freezing process as a template to prepare a porous material. In the freeze-drying process, the distance between the interdigital electrode and the cold table device can be controlled to control the temperature gradient at both ends of the electrode, so as to form a directional temperature gradient in the solution, and the ice crystals will quickly nucleate and grow at the freezing surface. Since the solubility of the conductive ink particles in the ice crystals is low, they are expelled into the ice crystal interstitial space. Then, the solid ice crystals are dried and removed, and the original ice crystal position will form an oriented porous structure, thereby obtaining a porous electrode with an ordered structure.

[0033] 2) The water-based rGO / Mxene composite conductive ink material used in the present application is easy to handle, purify and recycle, thereby avoiding environmental pollution and resource waste. At the same time, the rGO / Mxene composite material has excellent mechanical properties, high conductivity, high specific capacity, high specific surface area and high processability, and the obtained micro three-dimensional porous electrode has good electrochemical performance.

[0034] 3) The present application uses an inkjet printing method to prepare an interdigital electrode, which can meet the requirements of modern flexible wearable electronic products in terms of patterning, miniaturization and fine processing. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1It is a schematic diagram of interdigital electrode, divided into A, B, C three parts;

[0036] Figure 2 It is a schematic diagram of directional freezing device; (1) heat preservation cover, (2) heat preservation box body, (3) fixed iron stand, (4) cold source device;

[0037] Figure 3 It is a SEM diagram of interdigital electrode prepared in example 1 and comparative examples 1-4; (a) is example 1; (b) is comparative example 1; (c) is comparative example 2; (d) is comparative example 3; (e) is comparative example 4. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below.

[0039] The directional freezing device used in the examples and comparative examples of the present application is as follows:

[0040] The schematic diagram of the directional freezing device is as shown in Figure 2 (1) heat preservation cover, (2) heat preservation box body, (3) fixed iron stand, (4) cold source; wherein, the iron stand is connected at the edge of the center of the cold source, and the clamp on the iron stand is used to fix the frozen sample.

[0041] Example 1

[0042] A method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, comprising the following steps:

[0043] (1) 5mL of 1wt% polydimethyl diallyl ammonium chloride (PDDA) was added dropwise to 100mL of Mxene dispersion (1mg / mL) and ultrasonically stirred for 24h, then centrifuged at 12000rpm for 10min, washed with water three times, and the precipitate was reserved; the positively charged Mxene precipitate was ultrasonically dispersed in 100mL of water, and 20mL of the dispersed Mxene solution was added dropwise to 100mL of stirring rGO dispersion (2mg / mL), mixed and stirred for 2h, centrifuged at 3000rpm for 10min, washed with water three times, and the precipitate was collected and freeze-dried at-40℃ to obtain rGO / Mxene composite powder;

[0044] (2) The rGO / Mxene composite powder obtained in step (1) was ultrasonically dispersed in 50mL of water (rGO / Mxene solid content was 2wt%), 0.5wt% polyethylene glycol octylphenyl ether Triton X100, 10wt% ethylene glycol and 0.05wt% DF69 defoaming agent were added, and ultrasonic stirring was carried out to obtain rGO / Mxene composite ink suitable for inkjet printing;

[0045] (3) Inkjet printing symmetrical interdigital electrodes (length of part A of the interdigital electrode is 0.6 cm, width is 0.8 mm; length of part B is 15 mm, width is 2 mm; length of the "finger part" of part C is 2 cm, width is 1 mm, spacing between the four fingers is 3 mm; spacing between part B and the "finger part" of part C is 1 mm; thickness of the electrode is 50 μm) on a PET substrate, then vertically fixing the PET substrate carrying the interdigital electrode on an iron stand of an orientation freezing device (as shown in the figure), freezing for 2 min at a distance of 2 cm from the surface of the cold source (liquid nitrogen), at this time the temperature of the lower end of the symmetrical interdigital electrode is -130 ℃, and the temperature of the upper end of the symmetrical interdigital electrode is -90 ℃, then placing the electrode in a freeze dryer and freezing at -40 ℃; Figure 2

[0046] (4) Adding 3 g of polyvinyl alcohol (PVA) to 20 mL of deionized water, heating and stirring at 95 ℃ until the PVA is completely dissolved; separately, slowly adding 3 g of concentrated sulfuric acid to 10 mL of deionized water, stirring uniformly, then slowly adding to the completely dissolved PVA solution, maintaining the temperature and stirring for 30 min; then taking the PVA / H2SO4 and adding to the surface of the freeze-dried interdigital electrode, and then forming and packaging.

[0047] Comparative Example 1

[0048] A method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, comprising the following steps:

[0049] (1) Adding 5 mL of 1 wt% polydimethyl diallyl ammonium chloride (PDDA) to 100 mL of Mxene dispersion liquid (1 mg / mL) dropwise, ultrasonic stirring for 24 h, then centrifuging at 12000 rpm for 10 min, washing with water three times, and retaining the precipitate; ultrasonic dispersion of the positively charged Mxene precipitate in 100 mL of water, taking 20 mL of the dispersed Mxene solution and adding it dropwise to 100 mL of stirring rGO dispersion liquid (2 mg / mL), mixing and stirring for 2 h, centrifuging at 3000 rpm for 10 min, washing with water three times, collecting the precipitate and freeze-drying at -40 ℃ to obtain rGO / Mxene composite powder;

[0050] (2) Ultrasonic dispersion of the rGO / Mxene composite powder obtained in step (1) in 50 mL of water (rGO / Mxene solid content is 2 wt%), adding 0.5 wt% polyethylene glycol octylphenyl ether Triton X100, 10 wt% ethylene glycol and 0.05 wt% DF69 defoaming agent, ultrasonic stirring and mixing to obtain rGO / Mxene composite ink suitable for inkjet printing;

[0051] ​(3) Inkjet printing symmetrical interdigital electrodes (length of A part of the interdigital electrode is 0.6 cm, width is 0.8 mm; length of B part is 15 mm, width is 2 mm; length of "finger part" of C part is 2 cm, width is 1 mm, spacing between four fingers is 3 mm; spacing between B part and "finger part" of C part is 1 mm; electrode thickness is 50 μm) on the PET substrate, then placing the PET substrate carrying the interdigital electrode into a refrigerator with a temperature of -20 ℃ to freeze for 2 h, and then placing the electrode into a freeze dryer to freeze dry at -40 ℃;

[0052] (4) Adding 3 g of polyvinyl alcohol (PVA) into 20 mL of deionized water, heating and stirring at 95 ℃ until the PVA is completely dissolved; separately, slowly adding 3 g of concentrated sulfuric acid into 10 mL of deionized water, stirring until uniform, and then slowly dropping into the completely dissolved PVA solution, maintaining the temperature and stirring for 30 min; then taking the PVA / H2SO4 and adding to the surface of the freeze-dried interdigital electrode, and then allowing it to form and encapsulate.

[0053] Comparative Example 2

[0054] A method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, comprising the following steps:

[0055] (1) Ultrasonic dispersion of rGO powder in 50 mL of water (rGO solid content is 2 wt%), adding 0.5 wt% of polyethylene glycol octylphenyl ether Triton X100, 10 wt% of ethylene glycol and 0.05 wt% of DF69 defoaming agent, ultrasonic stirring and mixing to obtain rGO ink suitable for inkjet printing;

[0056] (2) Inkjet printing symmetrical interdigital electrodes (length of A part of the interdigital electrode is 0.6 cm, width is 0.8 mm; length of B part is 15 mm, width is 2 mm; length of "finger part" of C part is 2 cm, width is 1 mm, spacing between four fingers is 3 mm; spacing between B part and "finger part" of C part is 1 mm; electrode thickness is 50 μm) on the PET substrate, then vertically fixing the PET substrate carrying the interdigital electrode on the iron stand of the directional freezing device, at a distance of 2 cm from the surface of the cold source (liquid nitrogen) to freeze for 2 min, at this time the temperature of the lower end of the symmetrical interdigital electrode is -130 ℃, and the temperature of the upper end of the symmetrical interdigital electrode is -90 ℃, and then placing the electrode into a freeze dryer to freeze dry at -40 ℃;

[0057] (3) Adding 3 g of polyvinyl alcohol (PVA) into 20 mL of deionized water, heating and stirring at 95 ℃ until the PVA is completely dissolved. Separately, slowly adding 3 g of concentrated sulfuric acid into 10 mL of deionized water, stirring until uniform, and then slowly dropping into the completely dissolved PVA solution, maintaining the temperature and stirring for 30 min. Then taking the PVA / H2SO4 and adding to the surface of the freeze-dried interdigital electrode, and then allowing it to form and encapsulate.

[0058] Comparative Example 3

[0059] A method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, comprising the following steps:

[0060] (1) Mxene is ultrasonically dispersed in 50 mL of water (rGO solid content is 2 wt%), 0.5 wt% polyethylene glycol octylphenyl ether Triton X100, 10 wt% ethylene glycol and 0.05 wt% DF69 antifoaming agent are added, and the mixture is stirred and mixed by ultrasonic stirring to obtain rGO ink suitable for inkjet printing;

[0061] (2) Symmetrical interdigital electrodes are inkjet printed on a PET substrate (the length of the A part of the interdigital electrode is 0.6 cm, the width is 0.8 mm; the length of the B part is 15 mm, the width is 2 mm; the length of the "finger part" of the C part is 2 cm, the width is 1 mm, and the spacing between the four fingers is 3 mm; the spacing between the B part and the "finger part" of the C part is 1 mm; the thickness of the electrode is 50 μm), and then the PET substrate carrying the interdigital electrodes is vertically fixed on the iron stand of the directional freezing device, at a distance of 2 cm from the surface of the cold source (liquid nitrogen) and is frozen for 2 min, at which time the temperature at the lower end of the symmetrical interdigital electrodes is -130°C, and the temperature at the upper end of the symmetrical interdigital electrodes is -90°C, and then the electrodes are placed in a freeze dryer and are freeze-dried at -40°C;

[0062] (3) 3 g of polyvinyl alcohol (PVA) is added to 20 mL of deionized water, and heated and stirred at 95°C until the PVA is completely dissolved. Separately, 3 g of concentrated sulfuric acid is slowly added to 10 mL of deionized water and stirred uniformly, and then slowly added dropwise to the completely dissolved PVA solution, and stirred for 30 min while maintaining the temperature. Subsequently, the PVA / H2SO4 is added to the surface of the freeze-dried interdigital electrodes, and after the encapsulation is formed, it is ready.

[0063] Comparative Example 4

[0064] A method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, comprising the following steps:

[0065] (1) 5 mL of 1 wt% polydimethyl diallyl ammonium chloride (PDDA) is added dropwise to 100 mL of Mxene dispersion (1 mg / mL) and ultrasonically stirred for 24 h, and then centrifuged at 12000 rpm for 10 min, and washed with water three times, and the precipitate is retained; the positively charged Mxene precipitate is ultrasonically dispersed in 100 mL of water, and 20 mL of the dispersed Mxene solution is added dropwise to 100 mL of stirring rGO dispersion (2 mg / mL), and mixed and stirred for 2 h, and then centrifuged at 3000 rpm for 10 min, and washed with water three times, and the precipitate is collected and freeze-dried at -40°C to obtain rGO / Mxene composite powder;

[0066] (2) The rGO / Mxene composite powder obtained in step (1) is ultrasonically dispersed in 50 mL of water (rGO / Mxene solid content is 2 wt%), 0.5 wt% of polyethylene glycol octylphenyl ether Triton X100, 10 wt% of ethylene glycol and 0.05 wt% of DF69 antifoam agent are added, and the mixture is stirred and mixed by ultrasonic agitation to obtain a rGO / Mxene composite ink suitable for inkjet printing;

[0067] (3) A symmetrical interdigital electrode is inkjet printed on a PET substrate (the length of the A part of the interdigital electrode is 0.6 cm, the width is 0.8 mm; the length of the B part is 15 mm, the width is 2 mm; the length of the "finger part" of the C part is 2 cm, the width is 1 mm, the spacing between the four fingers is 3 mm; the spacing between the B part and the "finger part" of the C part is 1 mm; the thickness of the electrode is 50 μm), and then the PET substrate carrying the interdigital electrode is vertically fixed on the iron stand of the directional freezing device, 8 cm away from the surface of the cold source (liquid nitrogen), and is frozen for 2 min, at which time the temperature at the lower end of the symmetrical interdigital electrode is -60°C, and the temperature at the upper end of the symmetrical interdigital electrode is -20°C, and then the electrode is placed in a freeze dryer at -40°C for freeze drying;

[0068] (4) 3 g of polyvinyl alcohol (PVA) is added to 20 mL of deionized water, and heated and stirred at 95°C until the PVA is completely dissolved; another 3 g of concentrated sulfuric acid is slowly added to 10 mL of deionized water and stirred uniformly, and then slowly added dropwise to the completely dissolved PVA solution, and stirred for 30 min while maintaining the temperature; then the PVA / H2SO4 is added to the surface of the freeze-dried interdigital electrode, and after it is shaped and encapsulated, it is ready.

[0069] Performance result determination

[0070] 1. Surface morphology characterization

[0071] Figure 3 (a), (b), (c), (d), (e) in the table are the SEM morphologies of the interdigital electrodes on the PET substrate obtained by Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, respectively; it can be seen that the surfaces of the electrodes subjected to directional freezing all have regular arrangement, especially in Example 1, the rGO and Mxene composite directional freezing presents a long-range ordered directional arrangement structure, exposing a large number of ion transport channels and active sites on the surface, which is conducive to the contact between the electrode material and the ions; while pure rGO or Mxene directional freezing still has a small part of aggregation, and it is difficult to form large-area regular directional arrangement. In comparison, the electrode surfaces placed in the refrigerator and frozen at a distance exceeding the directional freezing distance have very few holes and channels, and have no regular structure.

[0072] 2. Electrochemical performance test

[0073] The interdigital electrodes prepared in Example 1 and Comparative Examples 1-4 were assembled into supercapacitors, and electrochemical impedance (EIS) and storage capacity at a current density of 0.5 A / g were measured, and the results are shown in Tables 1 and 2:

[0074] Table 1. Electrochemical impedance (EIS) performance

[0075]

[0076] Table 2. Storage capacity

[0077]

[0078] From the data in Tables 1 and 2, it can be seen that the supercapacitor of Example 1 has low impedance and high capacity, because the long-range ordered channels not only accelerate ion transport, but also provide a large number of ion storage sites.

[0079] 3. Stability test

[0080] The interdigital electrodes prepared in Example 1 were assembled into supercapacitors, and the mass specific capacity of the supercapacitors at a current density of 0.5 A / g was measured at bending angles of 0°, 30°, 60°, 90°, and 120°, and the results are shown in Table 3:

[0081] Table 3. Capacities of supercapacitors at different bending angles

[0082]

[0083] From the data in Table 3, it can be seen that the capacity loss of the supercapacitors at different bending angles is not significant, which can be attributed to the close connection of the directional frozen rGO / Mxene and the layer-by-layer directional arrangement structure, which can eliminate most of the stress on the structure at different bending angles, thereby maintaining stable capacity.

[0084] 4. Cycle stability test

[0085] The interdigital electrodes prepared in Example 1 and Comparative Examples 1-4 were assembled into supercapacitors, and cycle stability at a current density of 1 A / g was measured, and the results are shown in Table 4:

[0086] Table 4. Cycle stability

[0087]

[0088] As can be seen from the data in Table 4, the long-range order and close arrangement of the directional frozen rGO / Mxene ensure the stability of the structure during the cycle process, and the capacity can still reach 98.9% after 5000 cycles. At the same time, it can be seen that the capacity retention rate of the supercapacitor assembled by the interdigital electrode subjected to directional freezing during the cycle process is much higher than that of the supercapacitor assembled by the interdigital electrode not subjected to directional freezing.

[0089] The above provided examples are not intended to limit the scope covered by the present application, and the described steps are not intended to limit the execution order. The improvements of the present application made by those skilled in the art in combination with the existing common knowledge are also within the protection scope defined by the claims of the present application.

Claims

1. A method for preparing a micro three-dimensional porous electrode based on inkjet printing technology, characterized in that, The method comprises the following steps: (1) preparing rGO / Mxene composite powder; the preparation of rGO / Mxene composite powder specifically comprises the following steps: Polydimethyl diallyl ammonium chloride PDDA is added dropwise into the Mxene dispersion liquid under ultrasonic stirring, and then centrifuged to obtain the precipitate; the modified Mxene is ultrasonically dispersed in water, and then added dropwise into the rGO dispersion liquid, mixed and stirred, centrifuged, washed with water, and the precipitate is collected and freeze-dried to obtain the rGO / Mxene composite powder; (2) ultrasonically dispersing the rGO / Mxene composite powder prepared in step (1) in water, adding a surfactant, a thickening agent and a defoaming agent, and ultrasonically stirring and mixing to obtain a rGO / Mxene composite ink suitable for inkjet printing; (3) printing symmetrical interdigital electrodes on a flexible substrate by using inkjet printing technology, fixing the flexible substrate carrying the interdigital electrodes on the iron stand in the directional freezing device vertically along the finger extension direction, controlling the distance between the interdigital electrodes and the cold source for freezing, and then freeze-drying in the freezer to obtain an ordered array of micro three-dimensional porous electrodes; The directional freezing device comprises, from top to bottom, a heat preservation cover, a heat preservation box body, a fixed iron stand and a cold source device; wherein the distance between the interdigital electrodes and the cold source is 1-6 cm, the time is 2-5 min, and the temperature gradient at both ends of the electrode is controlled by controlling the distance between the interdigital electrodes and the cold source device; the distance freezing temperature interval is -140 ℃ to -80 ℃, and the temperature difference is 10±2 ℃ / cm.

2. The method of claim 1, wherein, The mass concentration of PDDA is 0.1-5 wt%, the concentration of Mxene dispersion liquid is 1-2 mg / mL, and the volume ratio of PDDA to Mxene dispersion liquid is 1:10-1:

50.

3. The method of claim 1, wherein, The concentration of the rGO dispersion liquid is 0.5-2 mg / mL, and the mass ratio of rGO to modified Mxene is 1:1-9:

1.

4. The method of claim 1, wherein, In step (2), the solid content of rGO / Mxene in the rGO / Mxene composite ink is 1-5 wt%.

5. The method of claim 1, wherein, In step (2), the surfactant includes one or more of fatty alcohol polyoxyethylene ether AEO, alkyl phenol polyoxyethylene ether TX, and polyol polyoxyethylene ether fatty acid ester.

6. The method of claim 1, wherein, In step (2), the thickening agent is one or more of ethylene glycol, 1,2-propanediol and glycerol.

7. The micro three-dimensional porous electrode prepared by the method of any one of claims 1-6.

8. The use of the micro three-dimensional porous electrode of claim 7 in the preparation of intelligent wearable products.

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