Ink direct-writing 3D printing planar interdigital lithium ion capacitor and preparation method thereof

Abstract

The invention discloses an ink direct-writing 3D printing planar interdigital lithium ion capacitor, which comprises a flexible substrate, a battery material finger electrode, a double-electrode-layer material finger electrode, a gel electrolyte and a packaging layer, the flexible substrate is provided with a battery material finger-type electrode and a double-electrode-layer material finger-type electrode side by side in the same plane, and the battery material finger-type electrode and the double-electrode-layer material finger-type electrode are opposite interdigital structure electrodes; a gel electrolyte is filled between the battery material finger-type electrode and the double-electrode-layer material finger-type electrode; the encapsulation layer encapsulates the battery material finger-type electrode, the double-electrode layer material finger-type electrode and the gel electrolyte on the flexible substrate; the flexible substrate, the battery material finger-type electrode, the double-electrode-layer material finger-type electrode, the gel electrolyte and the packaging layer are all obtained in an ink direct-writing 3D printing mode. The manufacturing process is simple, the cost is low, the device can be effectively compatible and integrated with different types of portable and wearable electronic devices, and the device has wide market application prospects.

Description

Technical Field

[0001] The present application relates to an ink direct writing 3D printed planar interdigitated lithium ion capacitor and a preparation method thereof, and belongs to the technical field of manufacturing lithium ion capacitors. Background Art

[0002] With the advancement of technology, various wearable and portable electronic devices continue to emerge, stimulating the demand for electrochemical energy storage devices. Lithium-ion capacitors are a type of battery-capacitor hybrid energy storage device composed of a lithium-ion battery negative electrode and a double-layer capacitor positive electrode connected in series. They combine the characteristics of high energy density of batteries and high power density of capacitors, and are expected to achieve a balance between energy density, power density and cycle stability. They are a class of very promising electrochemical energy storage devices. Lithium-ion capacitors can be divided into stacked and planar types according to their configuration. Among them, planar interdigitated lithium-ion capacitors can not only form a planar electrode geometry on a substrate, but also shorten the ion diffusion path by shortening the distance between interdigitated fingers, and do not require a diaphragm, making them a competitive power source. Ink direct writing 3D printing technology has the characteristics of low cost, scalability, customizable size and shape, and easy integration, making it a good choice for large-scale preparation of electrochemical energy storage devices. Summary of the invention

[0003] According to one aspect of the present application, an ink direct writing 3D printed planar interdigitated lithium ion capacitor is provided, providing a very potential electrochemical energy storage device.

[0004] This application adopts the following technical solutions:

[0005] An ink direct writing 3D printed planar interdigitated lithium ion capacitor, comprising a flexible substrate, a battery material interdigitated electrode, a double electric layer material interdigitated electrode, a gel electrolyte, and a packaging layer;

[0006] The flexible substrate places the battery material finger-shaped electrodes and the double-electric layer material finger-shaped electrodes side by side in the same plane, and the battery material finger-shaped electrodes and the double-electric layer material finger-shaped electrodes are opposite interdigital structure electrodes;

[0007] The battery material finger-shaped electrodes and the double-layer material finger-shaped electrodes are filled with gel electrolyte;

[0008] The encapsulation layer encapsulates the battery material finger-shaped electrodes, the double-electric layer material finger-shaped electrodes, and the gel electrolyte on the flexible substrate;

[0009] The flexible substrate, the finger-shaped electrodes of the battery material, the finger-shaped electrodes of the double-electric layer material, the gel electrolyte and the encapsulation layer are all obtained by ink direct writing 3D printing.

[0010] Optionally, the dimensions of the interdigitated structure are as follows: the interdigitated length is 5 to 20 mm, the width is 2 to 10 mm, and the interdigitated distance is 0.1 to 5 mm.

[0011] Optionally, the length of the interdigitated fingers of the interdigitated structure is 8 to 12 mm.

[0012] Optionally, the width of the interdigitated structure is 2 to 5 mm.

[0013] Optionally, the interdigital structure has a finger spacing of 0.2 to 1 mm.

[0014] According to another aspect of the present application, another method for preparing the above-mentioned ink direct writing 3D printed planar interdigital lithium ion capacitor is provided, characterized in that it includes the following steps:

[0015] S1, using ink I containing battery materials, conductive agents, and binders to 3D print battery material finger-shaped electrodes on a flexible substrate;

[0016] S2, using ink II containing double-layer material, conductive agent, and binder to 3D print double-layer material finger-shaped electrodes on the flexible substrate in step S1, and matching them with the battery material finger-shaped electrodes in step S1 to form interdigital structure electrodes;

[0017] S3, freeze-drying the interdigital structure electrode in step S2, and then 3D printing and filling the interdigital structure electrode with gel electrolyte, encapsulating, to obtain the ink direct writing 3D printed planar interdigital lithium ion capacitor.

[0018] The preparation method of the present application is to print the battery material and the double-layer material on the substrate respectively by ink direct writing 3D printing and ink extrusion to manufacture the negative (positive) electrode finger and the positive (negative) electrode finger, and then 3D print the gel electrolyte, and obtain the planar interdigitated lithium ion capacitor after packaging. The planar interdigitated lithium ion capacitor with ink direct writing 3D printing has a simple manufacturing process and low cost, and can be effectively compatible and integrated with different types of portable and wearable electronic devices. The planar interdigitated lithium ion capacitor with ink direct writing 3D printing manufactured by the present invention can achieve size control and large-scale production, and has broad market application prospects.

[0019] Optionally, in step S1, the material of the flexible substrate is a flexible high molecular polymer.

[0020] Optionally, the flexible substrate is polyethylene terephthalate.

[0021] Optionally, in step S1, the battery material is selected from at least one of vanadium pentoxide, niobium pentoxide, lithium titanate, lithium cobaltate, natural graphite, and titanium dioxide.

[0022] Optionally, in step S1 and step S2, the conductive agent is independently selected from at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, and electrochemically exfoliated graphene.

[0023] Optionally, in step S1 and step S2, the binder is independently selected from at least one of hydroxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, and polyvinylidene fluoride.

[0024] Optionally, in step S2, the double-layer material is selected from at least one of activated carbon and graphene.

[0025] Optionally, in step S3, the gel electrolyte is selected from at least one of bis(trifluoromethanesulfonyl)imide lithium salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, polyvinylidene fluoride-hexafluoropropylene copolymer, lithium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, polyvinylidene fluoride-hexafluoropropylene copolymer, bis(trifluoromethanesulfonyl)imide lithium salt, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, and polyvinylidene fluoride-hexafluoropropylene copolymer.

[0026] Optionally, the freeze-drying time is 18 to 36 hours.

[0027] Optionally, in step S1 and step S2, the solvent in ink I and ink II is independently selected from at least one of water and N-methylpyrrolidone. ;

[0028] Optionally, in step S1 and step S2, the content of the binder in the ink I and the ink II is independently 2-15%.

[0029] Optionally, in step S1 and step S2, the content of the binder in the ink I and ink II is independently selected from any value among 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15% or any range between two values.

[0030] Optionally, in step S1 and step S2, the content of the conductive agent in the ink I and the ink II is independently 5-30%.

[0031] Optionally, in step S1 and step S2, the content of the conductive agent in the ink I and ink II is independently selected from any value among 5%, 10%, 15%, 20%, 25%, 30%, or any range between the two.

[0032] Optionally, in step S1 and step S2, the solid contents of ink I and ink II are independently 0.3 to 1.5 g / mL.

[0033] Optionally, in step S1 and step S2, the solid contents of ink I and ink II are independently 0.4-1 g / mL.

[0034] Optionally, in step S1 to step S3, the conditions for 3D printing include: using ink direct writing 3D printing method, the pressure is 20 to 50 psi, and the printing speed is 3 to 10 mm / s.

[0035] Where 1psi=0.006894757MPa.

[0036] Optionally, in step S1 to step S3, the apertures of the ink extrusion needles used in 3D printing are independently 150 to 600 μm.

[0037] Optionally, in step S1 to step S3, the apertures of the ink extrusion needles used for 3D printing are independently 200 to 500 μm.

[0038] The beneficial effects of this application include:

[0039] The ink direct writing 3D printed planar interdigitated lithium ion capacitor described in the present application has its positive and negative electrodes naturally separated on a PET substrate, does not require a diaphragm, is easy to operate, and uses a gel electrolyte. There is no risk of electrolyte leakage and it has high safety. At the same time, the ink direct writing 3D printing technology can increase the load of active materials by increasing the number of printed layers of the lithium ion capacitor electrodes within a limited plane area, thereby greatly improving the surface capacity and surface energy density of the lithium ion capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 .Example of ink direct writing 3D printing planar interdigitated lithium ion capacitor in Example 1 of the present application: Schematic diagram of a planar interdigitated lithium ion capacitor manufactured on a PET substrate. DETAILED DESCRIPTION

[0041] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0042] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0043] Example 1

[0044] Vanadium pentoxide (battery material), activated carbon (double-layer material), carbon nanotubes (conductive agent), and sodium carboxymethyl cellulose (binder) are used as raw materials. Vanadium pentoxide, carbon nanotubes, and sodium carboxymethyl cellulose solids are evenly mixed, dispersed in deionized water and ground for 1 hour to form vanadium pentoxide ink. The solid content of vanadium pentoxide ink is 0.4g / mL, and the mass fractions of battery material, conductive agent, and binder are 60wt%, 30wt%, and 10wt%, respectively. Activated carbon, carbon nanotubes, and sodium carboxymethyl cellulose solids are evenly mixed, dispersed in deionized water and ground for 1 hour to form activated carbon ink. The solid content of activated carbon ink is 0.35g / mL, and the mass fractions of double-layer material, conductive agent, and binder are 60wt%, 30wt%, and 10wt%, respectively. This embodiment ( Figure 1 ) The finger length of the interdigital model of the ink direct writing 3D printing is 8mm, the width is 3mm, and the finger spacing is 0.6mm. First, the vanadium pentoxide interdigital negative electrode is printed on the PET substrate, with a printing speed of 5mm / s, an extrusion pressure of 25psi, and an extrusion needle aperture of 340μm; then the activated carbon interdigital positive electrode is printed with a printing speed of 3mm / s, an extrusion pressure of 30psi, and an extrusion needle aperture of 340μm. After freeze-drying for 24 hours, the interdigital electrode is printed with LiTFSI / P 14 TFSI / PVDF-HFP gel electrolyte, and finally encapsulation to obtain ink direct writing 3D printed planar interdigital lithium ion capacitor. The obtained planar interdigital lithium ion capacitor can work stably under a voltage window of 3V and 1mA cm -2 The constant current charge and discharge test was carried out at a current density of 1.15 mWh cm -2 .

[0045] Example 2

[0046] Lithium titanate (battery material), graphene (double-layer material), conductive carbon black (conductive agent), and polyvinylidene fluoride (binder) are used as raw materials. Lithium titanate, conductive carbon black, and polyvinylidene fluoride solids are mixed evenly, dispersed in N-methylpyrrolidone and ground for half an hour to form lithium titanate negative electrode ink. The solid content of lithium titanate ink is 1g / mL, and the mass fractions of battery materials, conductive agents, and binders are 70wt%, 20wt%, and 10wt%, respectively. Graphene, conductive carbon black, and polyvinylidene fluoride solids are mixed evenly, dispersed in N-methylpyrrolidone and ground for half an hour to form graphene positive electrode ink. The solid content of lithium titanate ink is 0.7g / mL, and the mass fractions of double-layer materials, conductive agents, and binders are 70wt%, 20wt%, and 10wt%, respectively. First, the lithium titanate interdigital negative electrode was printed on the PET substrate at a printing speed of 4 mm / s, an extrusion pressure of 33 psi, and an extrusion needle aperture of 340 μm; then the graphene interdigital positive electrode was printed at a printing speed of 6 mm / s, an extrusion pressure of 26 psi, and an extrusion needle aperture of 340 μm. The interdigital electrode was dried in a vacuum oven at 100 ° C for 12 hours, and the LiBF4 / EMIMBF4 / PVDF-HFP gel electrolyte was printed. Finally, the ink direct writing 3D printed planar interdigital lithium ion capacitor was obtained, and its configuration was similar to that of the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 6mm, a width of 2mm, and a finger spacing of 0.6mm. The obtained planar interdigital lithium ion capacitor can work stably in a voltage window of 3V and a current of 1mA cm -2 The constant current charge and discharge test was carried out at a current density of 1.08 mWh cm -2 .

[0047] Example 3

[0048] Vanadium pentoxide (battery material), activated carbon (double-layer material), Ketjen black (conductive agent), and sodium alginate (binder) are used as raw materials. Vanadium pentoxide, Ketjen black, and sodium alginate solids are mixed evenly, dispersed in deionized water and ground for 1 hour to form vanadium pentoxide ink. The solid content of vanadium pentoxide ink is 0.5g / mL, and the mass fractions of battery material, conductive agent, and binder are 75wt%, 20wt%, and 5wt%, respectively. Activated carbon, Ketjen black, and sodium alginate solids are mixed evenly, dispersed in deionized water and ground for 1 hour to form activated carbon ink. The solid content of activated carbon ink is 0.4g / mL, and the mass fractions of double-layer material, conductive agent, and binder are 80wt%, 15wt%, and 5wt%, respectively. First, the vanadium pentoxide interdigital negative electrode was printed on the PET substrate at a printing speed of 6 mm / s, an extrusion pressure of 42 psi, and an extrusion needle aperture of 260 μm; then the activated carbon interdigital positive electrode was printed at a printing speed of 8 mm / s, an extrusion pressure of 38 psi, and an extrusion needle aperture of 260 μm. After the interdigital electrode was freeze-dried for 24 hours, the LiTFSI / EMIMTFSI / PVDF-HFP gel electrolyte was printed, and finally packaged to obtain an ink direct writing 3D printed planar interdigital lithium ion capacitor, which has the same configuration as the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 10mm, a width of 3mm, and a finger spacing of 0.5mm. The resulting planar interdigital lithium ion capacitor can work stably at a voltage window of 3V and a current of 1mAcm -2 The constant current charge and discharge test was carried out at a current density of 0.98 mWhcm -2 .

[0049] Example 4

[0050] Lithium cobalt oxide (battery material), graphene (double-layer material), conductive carbon black (conductive agent), and polyvinylidene fluoride (binder) are used as raw materials. Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride solids are mixed evenly, dispersed in NMP and ground for 30 minutes to form lithium cobalt oxide positive electrode ink. The solid content of lithium cobalt oxide ink is 1.5g / mL, and the mass fractions of battery materials, conductive agents, and binders are 75wt%, 22wt%, and 3wt%, respectively. Graphene, conductive carbon black, and polyvinylidene fluoride solids are mixed evenly, dispersed in NMP and ground for 30 minutes to form graphene negative electrode ink. The solid content of graphene ink is 0.8g / mL, and the mass fractions of double-layer materials, conductive agents, and binders are 90wt%, 8wt%, and 2wt%, respectively. First, the lithium cobalt oxide positive electrode was printed on the PET substrate at a printing speed of 3 mm / s, an extrusion pressure of 50 psi, and an extrusion needle aperture of 410 μm; then the graphene interdigitated negative electrode was printed at a printing speed of 5 mm / s, an extrusion pressure of 25 psi, and an extrusion needle aperture of 340 μm. After the interdigitated electrodes were dried in a vacuum oven for 12 hours, LiTFSI / P 14 TFSI / PVDF-HFP gel electrolyte, and finally encapsulation to obtain ink direct writing 3D printed planar interdigitated lithium ion capacitor, the configuration of which is similar to the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 12 mm, a width of 5 mm, and a finger spacing of 1 mm. The resulting planar interdigital lithium ion capacitor can operate stably in a voltage window of 3 V and has a current of 1 mA cm -2 The constant current charge and discharge test was carried out at a current density of 1.13 mWh cm -2 .

[0051] Example 5

[0052] Niobium pentoxide (battery material), activated carbon (double-layer material), electrochemically exfoliated graphene (conductive agent), hydroxymethyl cellulose and hydroxyethyl cellulose (binder) are used as raw materials. Niobium pentoxide, electrochemically exfoliated graphene, hydroxymethyl cellulose and hydroxyethyl cellulose are mixed evenly, dispersed in deionized water and ground for 1 hour to form niobium pentoxide ink. The solid content of niobium pentoxide ink is 0.9g / mL, and the mass fractions of battery material, conductive agent and binder are 80wt%, 10wt% and 10wt% respectively. Activated carbon, electrochemically exfoliated graphene, hydroxymethyl cellulose and hydroxyethyl cellulose solids are mixed evenly, dispersed in deionized water and ground for 1 hour to form activated carbon ink. The solid content of activated carbon ink is 0.85g / mL, and the mass fractions of double-layer material, conductive agent and binder are 80wt%, 10wt% and 10wt% respectively. First, the niobium pentoxide interdigital negative electrode was printed on the PET substrate at a printing speed of 4 mm / s, an extrusion pressure of 36 psi, and an extrusion needle aperture of 340 μm; then the activated carbon interdigital positive electrode was printed at a printing speed of 4 mm / s, an extrusion pressure of 34 psi, and an extrusion needle aperture of 340 μm. After the interdigital electrode was freeze-dried for 24 hours, the LiBF4 / EMIMBF4 / PVDF-HFP gel electrolyte was printed, and finally packaged to obtain an ink direct writing 3D printed planar interdigital lithium ion capacitor, which has the same configuration as the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 9 mm, a width of 4 mm, and a finger spacing of 0.7 mm. The resulting planar interdigital lithium ion capacitor can operate stably in a voltage window of 3 V and has a current of 1 mA cm -2 The constant current charge and discharge test was carried out at a current density of 1.04 mWh cm -2 .

[0053] Example 6

[0054] Natural graphite (battery material), activated carbon (double-layer material), acetylene black (conductive agent), and sodium hydroxymethyl cellulose (binder) are used as raw materials. Natural graphite, acetylene black, and sodium hydroxymethyl cellulose are mixed evenly, dispersed in deionized water and ground for 1 hour to form natural graphite negative electrode ink. The solid content of natural graphite ink is 0.55g / mL, and the mass fractions of battery material, conductive agent, and binder are 60wt%, 36wt%, and 4wt%, respectively. Activated carbon, acetylene black, and sodium hydroxymethyl cellulose solids are mixed evenly, dispersed in deionized water and ground for 1 hour to form activated carbon ink. The solid content of activated carbon ink is 0.75g / mL, and the mass fractions of double-layer material, conductive agent, and binder are 76wt%, 20wt%, and 4wt%, respectively. First, the niobium pentoxide interdigital negative electrode was printed on the PET substrate at a printing speed of 5 mm / s, an extrusion pressure of 22 psi, and an extrusion needle aperture of 260 μm; then the activated carbon interdigital positive electrode was printed at a printing speed of 4 mm / s, an extrusion pressure of 37 psi, and an extrusion needle aperture of 340 μm. After freeze-drying for 24 hours, the interdigital electrode was printed on the LiTFSI / P 14 TFSI / PVDF-HFP gel electrolyte, and finally encapsulation to obtain ink direct writing 3D printed planar interdigitated lithium ion capacitor, the configuration of which is similar to the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 8mm, a width of 2mm, and a finger spacing of 0.5mm. The obtained planar interdigital lithium ion capacitor can work stably in a voltage window of 3V and a current of 1mA cm -2 The constant current charge and discharge test was carried out at a current density of 1.1 mWh cm -2 .

[0055] Example 7

[0056] Lithium titanate (battery material), activated carbon (double-layer material), conductive carbon black (conductive agent), hydroxymethyl cellulose and hydroxyethyl cellulose (binder) are used as raw materials. Lithium titanate, conductive carbon black, hydroxymethyl cellulose and hydroxyethyl cellulose (mass ratio is 1:1) are mixed evenly, dispersed in deionized water and ground for 1 hour to form lithium titanate negative electrode ink. The solid content of lithium titanate ink is 0.6g / mL, and the mass fractions of battery materials, conductive agents and binders are 60wt%, 28wt% and 12wt% respectively. Activated carbon, conductive carbon black, hydroxymethyl cellulose and hydroxyethyl cellulose (mass ratio is 1:1) are mixed evenly, dispersed in deionized water and ground for 1 hour to form activated carbon ink. The solid content of activated carbon ink is 0.6g / mL, and the mass fractions of double-layer materials, conductive agents and binders are 78wt%, 10wt% and 12wt% respectively. First, the lithium titanate interdigital negative electrode was printed on the PET substrate at a printing speed of 4 mm / s, an extrusion pressure of 31 psi, and an extrusion needle aperture of 260 μm; then the activated carbon interdigital positive electrode was printed at a printing speed of 4 mm / s, an extrusion pressure of 35 psi, and an extrusion needle aperture of 340 μm. After the interdigital electrode was freeze-dried for 24 hours, the LiTFSI / EMIMTFSI / PVDF-HFP gel electrolyte was printed, and finally packaged to obtain an ink direct writing 3D printed planar interdigital lithium ion capacitor, which has the same configuration as the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 10mm, a width of 3mm, and a finger spacing of 1mm. The resulting planar interdigital lithium ion capacitor can work stably at a voltage window of 3V and a current of 1mAcm -2 The constant current charge and discharge test was carried out at a current density of 1.21 mWh cm -2 .

[0057] Example 8

[0058] Titanium dioxide (battery material), activated carbon (double-layer material), Ketjen black (conductive agent), and sodium carboxymethyl cellulose (binder) are used as raw materials. Titanium dioxide, Ketjen black, and sodium carboxymethyl cellulose are mixed evenly, dispersed in deionized water and ground for 1 hour to form titanium dioxide negative electrode ink. The solid content of titanium dioxide ink is 0.5g / mL, and the mass fractions of battery material, conductive agent, and binder are 63wt%, 30wt%, and 7wt%, respectively. Activated carbon, Ketjen black, and sodium carboxymethyl cellulose solids are mixed evenly, dispersed in deionized water and ground for 1 hour to form activated carbon ink. The solid content of activated carbon ink is 0.5g / mL, and the mass fractions of double-layer material, conductive agent, and binder are 85wt%, 12wt%, and 3wt%, respectively. First, the titanium dioxide interdigitated negative electrode was printed on the PET substrate at a printing speed of 6 mm / s, an extrusion pressure of 45 psi, and an extrusion needle aperture of 340 μm; then the activated carbon interdigitated positive electrode was printed at a printing speed of 6 mm / s, an extrusion pressure of 42 psi, and an extrusion needle aperture of 340 μm. After the interdigitated electrode was freeze-dried for 24 hours, the LiBF4 / EMIMBF4 / PVDF-HFP gel electrolyte was printed, and finally packaged to obtain an ink direct writing 3D printed planar interdigitated lithium ion capacitor, which has the same configuration as the attached Figure 1 The interdigital model of the ink direct writing 3D printing has a finger length of 11mm, a width of 4mm, and a finger spacing of 0.7mm. The obtained planar interdigital lithium ion capacitor can work stably in a voltage window of 3V and a current of 1mA cm -2 The constant current charge and discharge test was carried out at a current density of 1.07 mWh cm -2 .

[0059] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An ink direct writing 3D printed planar interdigitated lithium ion capacitor, characterized in that: It includes a flexible substrate, a finger-shaped electrode of a battery material, a finger-shaped electrode of a double-layer material, a gel electrolyte, and a packaging layer; The flexible substrate places the battery material finger-shaped electrodes and the double-electric layer material finger-shaped electrodes side by side in the same plane, and the battery material finger-shaped electrodes and the double-electric layer material finger-shaped electrodes are opposite interdigital structure electrodes; The battery material finger-shaped electrodes and the double-layer material finger-shaped electrodes are filled with gel electrolyte; The encapsulation layer encapsulates the battery material finger-shaped electrodes, the double-electric layer material finger-shaped electrodes, and the gel electrolyte on the flexible substrate; The flexible substrate, the finger-shaped electrodes of the battery material, the finger-shaped electrodes of the double-electric layer material, the gel electrolyte and the encapsulation layer are all obtained by ink direct writing 3D printing.

2. The ink direct writing 3D printing planar interdigitated lithium ion capacitor according to claim 1, characterized in that: The dimensions of the interdigital structure are as follows: the interdigital length is 5 to 20 mm, the width is 2 to 10 mm, and the interdigital spacing is 0.1 to 5 mm.

3. The method for preparing the ink direct writing 3D printed planar interdigitated lithium ion capacitor according to claim 1 or 2, characterized in that: The steps include: S1, using ink I containing battery materials, conductive agents, and binders to 3D print battery material finger-shaped electrodes on a flexible substrate; S2, using ink II containing double-layer material, conductive agent, and binder to 3D print double-layer material finger-shaped electrodes on the flexible substrate in step S1, and matching them with the battery material finger-shaped electrodes in step S1 to form interdigital structure electrodes; S3, freeze-drying the interdigital structure electrode in step S2, and then 3D printing and filling the interdigital structure electrode with gel electrolyte, encapsulating, to obtain the ink direct writing 3D printed planar interdigital lithium ion capacitor.

4. The preparation method according to claim 3, characterized in that: In step S1, the material of the flexible substrate is a flexible high molecular polymer; Preferably, in step S1, the battery material is selected from at least one of vanadium pentoxide, niobium pentoxide, lithium titanate, lithium cobaltate, natural graphite and titanium dioxide.

5. The preparation method according to claim 3, characterized in that: In step S1 and step S2, the conductive agent is independently selected from at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, and electrochemically exfoliated graphene.

6. The preparation method according to claim 3, characterized in that: In step S1 and step S2, the binder is independently selected from at least one of hydroxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, and polyvinylidene fluoride.

7. The preparation method according to claim 3, characterized in that: In step S2, the double-layer material is selected from at least one of activated carbon and graphene.

8. The preparation method according to claim 3, characterized in that: In step S3, the gel electrolyte is selected from at least one of bis(trifluoromethanesulfonyl)imide lithium salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, polyvinylidene fluoride-hexafluoropropylene copolymer, lithium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, polyvinylidene fluoride-hexafluoropropylene copolymer, bis(trifluoromethanesulfonyl)imide lithium salt, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, and polyvinylidene fluoride-hexafluoropropylene copolymer; Preferably, the freeze-drying time is 18 to 36 hours.

9. The preparation method according to claim 3, characterized in that: In step S1 and step S2, the solvents in ink I and ink II are independently selected from at least one of water and N-methylpyrrolidone; Preferably, in step S1 and step S2, the content of the binder in the ink I and the ink II is independently 2-15%; Preferably, in step S1 and step S2, the content of the conductive agent in the ink I and the ink II is independently 5-30%; Preferably, in step S1 and step S2, the solid contents of ink I and ink II are independently 0.3-1.5 g / mL.

10. The preparation method according to claim 3, characterized in that: In step S1 to step S3, the conditions for 3D printing include: using ink direct writing 3D printing, a pressure of 20 to 50 psi, and a printing speed of 3 to 10 mm / s; Preferably, in step S1 to step S3, the apertures of the ink extrusion needles used in 3D printing are independently 150 to 600 μm.

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