Elastic current collector printing ink, preparation method thereof and application thereof in 3D inkjet printing multi-directional stretchable battery

Abstract

The present application relates to a kind of elastic current collector printing ink and its preparation method and its application in 3D inkjet printing multi-directional stretchable battery, belong to wearable electronic device technical field.The present application discloses a kind of elastic current collector printing ink, the elastic current collector printing ink is made of carbon nanotube grafting graphene conductive composite material, polymer emulsion, surfactant, deionized water is mixed, wherein carbon nanotube grafting graphene conductive composite material is three-dimensional network structure, with Ni metal nanoparticles as node connects graphene, carbon nanotube.The present application further discloses a kind of positive / negative printing ink.The present application further discloses a kind of 3D inkjet printing multi-directional stretchable battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of wearable electronic devices and relates to an elastic current collector printing ink, a preparation method thereof, and its application in 3D inkjet-printed multi-directionally stretchable batteries. Background Art

[0002] In recent years, the consumer electronics industry has rapidly expanded, penetrating into key areas critical to people's quality of life, such as healthcare, sports and wellness, and infotainment. Applications include flexible displays, flexible electronic skin, smart electronic clothing, and micro-electromechanical systems. To ensure that wearable devices can adapt to diverse deformation scenarios, battery flexibility and stretchability are crucial. Traditional energy storage devices such as lithium-ion batteries, alkaline zinc-manganese batteries, and lead-acid batteries may have high energy density, but inherent drawbacks such as large size, heavy weight, and fixed shape make them incompatible with the energy storage needs of flexible wearable devices. Therefore, new flexible and stretchable batteries and related materials have become a hot topic for development.

[0003] Currently, research on flexible electrodes is primarily pursued through two approaches: extrinsic flexible structural design of rigid materials and improvements to intrinsic flexible materials. Inspired by biomimetics and origami, the flexible design of rigid materials utilizes microelementary / flexible design. Through ingenious structural designs such as kirigami, origami, island-bridge, wave, and coil spring structures, extrinsic flexible electrodes with macroscopic flexibility are achieved, significantly increasing the degree of deformation freedom of flexible batteries. The preparation of intrinsically flexible electrodes primarily relies on methods such as solvothermal, chemical deposition, and vacuum filtration. Active materials are loaded onto intrinsically flexible substrates, resulting in an integrated design that ensures the integrity of the electrode structure under complex deformations while maintaining stable battery performance. Key approaches include directly bonding metals to elastic substrates, combining highly conductive rigid materials with stretchable polymers, and processing carbon-based materials with excellent conductivity and inherent flexibility to serve as current collectors for stretchable electrodes.

[0004] The current collector is a core component of the battery. In order to maintain the stability of the electrochemical performance of the electrode under tension, it is crucial to ensure that the current collector still has excellent conductivity under synchronous deformation. Traditional current collectors (aluminum foil, copper foil, etc.) are no longer suitable for stretchable battery systems. The introduction of new elastic materials fundamentally changes the structure of electrodes and current collectors in traditional batteries. Stretchable conductive elastomers are prepared by compounding conductive fillers with elastic materials. Among them, the most widely used fillers are still graphite, graphene, carbon nanotubes, etc. The ultra-high aspect ratio and specific surface area of ​​carbon nanotubes and graphene lead to extremely strong van der Waals forces between single carbon nanotubes and between single-layer and few-layer graphene, which are prone to agglomeration and entanglement, affecting the formation of the conductive network inside the polymer and its stability under tension.

[0005] In order to achieve the goal of maintaining stable performance of electrodes under multi-directional stretching, bending and stretching, it is not possible to rely solely on non-intrinsic flexible structural design or the use of intrinsic flexible materials. This is because the use of non-intrinsic flexible structural design alone cannot cope with any stretching of the electrode body. The use of intrinsic flexible materials alone, especially intrinsic flexible electrodes with a single structural configuration, is difficult to effectively cope with multi-directional stretching conditions. Their microstructure and conductive network will still be destroyed, active substances will fall off, and the electrode and current collector will be peeled off, and the battery performance will drop sharply. Only by combining non-intrinsic flexible structural design and intrinsic flexible material performance improvement, and combining rigidity and flexibility, can the electrode be more effectively achieved to maintain stable energy output under multi-directional stretching and various deformation states. Summary of the Invention

[0006] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and propose an elastic current collector printing ink, which can be used together with positive / negative electrode printing inks made from positive / negative electrode active materials to produce a 3D inkjet-printed multi-directional stretchable battery in which the electrodes can still maintain stable performance under multi-directional stretching (deformation) conditions.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] Disclosed is an elastic current collector printing ink, which is prepared by mixing a carbon nanotube-grafted graphene conductive composite material, a polymer emulsion, a surfactant, and deionized water. The carbon nanotube-grafted graphene conductive composite material is a three-dimensional network structure, and Ni metal nanoparticles are used as nodes to connect graphene and carbon nanotubes.

[0009] Preferably, the solid content of the carbon nanotube-grafted graphene conductive composite material in the elastic current collector printing ink is 2-20 wt %.

[0010] Preferably, the viscosity of the elastic current collector printing ink is 13-35 Pa·s.

[0011] Preferably, the mass ratio of the carbon nanotube-grafted graphene conductive composite material, the polymer emulsion, and the surfactant is (1-10): (0.5-20): (1-20).

[0012] The present invention connects graphene and carbon nanotubes, which have ultra-high conductivity, with ultra-high conductive Ni metal nanoparticles as nodes. This structure gives the material ultra-high conductivity, so that the elastic current collector printing ink containing this material also has excellent conductivity and expands the application field.

[0013] Preferably, the preparation method of the carbon nanotube-grafted graphene conductive composite material includes: mixing glucose monohydrate, ammonium chloride, divalent nickel inorganic acid salt and deionized water, drying and grinding to obtain a mixed powder, adding it to a binary salt system consisting of sodium chloride and potassium chloride and preheating it, transferring the preheated material to a tubular furnace and keeping it warm in an argon atmosphere, switching to an acetylene gas channel and continuing to keep it warm, then switching to an argon gas channel and cooling it to room temperature, washing and drying it to obtain the carbon nanotube-grafted graphene conductive composite material.

[0014] The present invention adopts a simple, low-cost and environmentally friendly molten salt method, in which a strong polar ionic liquid environment is used in a high-temperature KCl / NaCl eutectic salt ionic flux, which is conducive to sp 3 Hybrid CC or CX to sp 2 Hybrid CC conversion directly converts glucose into graphene materials. In the molten salt method, the conversion process of glucose to graphene is carried out. The lone pair electrons on the N atom doped on the aromatic ring small molecule fragment can form a conjugated structure with the π bond in the carbon ring, which is conducive to having a large number of sp 2 The aromatic ring fragments of the hybridized carbon are reorganized to form graphene. At the same time, in a high-temperature, highly polar ionic liquid environment, when glucose is converted into graphene, a reducing pyrolysis gas is generated, which can reduce the divalent nickel ions in the precursor to metallic nickel, and in situ generate Ni nanoparticles (Ni@Gr) on the graphene surface. Based on Ni@Gr, it is directly maintained in a high-temperature polar ionic liquid environment to promote the Ni@Gr graphene sheet to be in a stretched state. Acetylene gas is introduced to more efficiently grow carbon nanotubes (CNTs) with Ni nanoparticles as catalytic sites. The generated carbon nanotubes act as a scaffold to effectively stretch the graphene sheet (Gr), thereby producing a CNT-g-Gr conductive composite material with an integrated three-dimensional network structure with an ultra-high specific surface area.

[0015] Preferably, the mass ratio of the glucose monohydrate, ammonium chloride and divalent nickel inorganic acid salt is 100:(30-100):(2-15).

[0016] More preferably, the mass ratio of the mixed powder of glucose monohydrate, ammonium chloride, and divalent nickel inorganic acid salt to deionized water is 1:(0.5-1.5).

[0017] More preferably, the divalent nickel inorganic acid salt is one or more of nickel chloride and nickel nitrate.

[0018] Preferably, the mass ratio of sodium chloride to potassium chloride in the binary salt system is 1:(0.5-1.5).

[0019] Preferably, the mass ratio of glucose monohydrate to the binary salt system is 1:(10-100).

[0020] More preferably, the mass ratio of the mixed powder to the binary salt system is 1:(20-100).

[0021] Preferably, the preheating temperature is 100-200° C. and the preheating time is 5-24 hours.

[0022] During the preheating stage, glucose monohydrate and ammonium chloride undergo Maillard reaction to generate graphene precursors.

[0023] Preferably, the temperature for insulation in an argon atmosphere is a first temperature, and the insulation time is a first insulation time; the temperature for insulation in an acetylene gas is a second temperature, and the insulation time is a second insulation time.

[0024] More preferably, the first temperature is higher than the second temperature; wherein the first temperature is 800-1300°C, and the second temperature is 750-1000°C.

[0025] More preferably, the first insulation time is 30-120 min, and the second insulation time is 5-60 min.

[0026] Preferably, the heating rate in the tube furnace is 5-30°C / min.

[0027] The present invention also discloses a method for preparing elastic current collector printing ink, which comprises: adding a polymer emulsion dropwise into a dispersion consisting of a carbon nanotube-grafted graphene conductive composite material, a surfactant, and deionized water, and adjusting the viscosity to obtain the elastic current collector printing ink.

[0028] More preferably, the polymer includes one or more of polystyrene-ethylene-butylene-styrene, polystyrene-polymethyl acrylate-polystyrene, polystyrene-polybutyl acrylate-polystyrene, polyimide, polyvinylidene fluoride, polytetrafluoroethylene, and polydimethylsiloxane.

[0029] The polymer emulsion can be prepared from the polymer by conventional methods.

[0030] Preferably, the surfactant is sodium dodecyl sulfate.

[0031] Preferably, the carbon nanotube-grafted graphene conductive composite material is first prepared with deionized water into a solution with a concentration of 5-15 mg / mL.

[0032] Preferably, the mass ratio of the carbon nanotube-grafted graphene conductive composite material to the surfactant in the dispersion is 1:(1-10).

[0033] Preferably, the dispersion is prepared by sequentially subjecting it to magnetic stirring and ultrasound.

[0034] The invention also discloses a positive / negative electrode printing ink, which is made of positive / negative electrode active materials, a conductive agent, a binder, and a dispersant.

[0035] Preferably, the mass ratio of the positive / negative electrode active material, the conductive agent, and the binder is (70-80): (10-20): (10-20).

[0036] Preferably, the mass ratio of the positive electrode to the negative electrode in the positive / negative electrode active material is (1:10):1.

[0037] More preferably, any two of the positive and negative electrode active materials can be assembled into a battery.

[0038] The changes in the conductivity of batteries assembled using conventional different positive and negative electrode materials in the present invention all conform to the rules described in the present invention, and the changes in their surface conductivity remain basically consistent after being stretched at different angles.

[0039] Preferably, the area of ​​the stretchable battery is 0.4-16 cm 2 ;

[0040] Preferably, the printing thickness of the current collector is 50 μm-150 μm, and the printing thickness of the positive electrode and the negative electrode is 50 μm-200 μm;

[0041] Preferably, the conductive agent is SuperP.

[0042] Preferably, the binder is the above-mentioned polymer emulsion.

[0043] More preferably, the binder is the same as the polymer emulsion in the elastic current collector printing ink.

[0044] Preferably, the dispersion medium is deionized water.

[0045] The present invention further discloses a 3D inkjet-printed multi-directional stretchable battery, comprising:

[0046] Flexible substrate;

[0047] An elastic current collector printing ink layer is printed on the surface of a flexible substrate;

[0048] Positive / negative electrode printing ink layer, which is printed on the surface of the elastic current collector printing ink layer;

[0049] and a gel electrolyte filling layer, which is filled between the positive / negative electrode lines.

[0050] Preferably, the 3D inkjet-printed multi-directional stretchable battery is produced by controlling the movement of the printing nozzle through software to form the elastic current collector printing ink on the surface of the flexible substrate, then covering it with the positive / negative electrode printing ink to obtain the positive / negative electrode, and filling the positive / negative electrode circuits with a gel electrolyte, and then encapsulating it.

[0051] The 3D printing technology used in the present invention is based on digital model files and accurately controls the morphology through layer-by-layer printing. Its greatest advantage lies in the design and manufacture of the electrode microstructure. The 3D printing technology used to prepare electrodes can ensure the content of energy storage active materials, effectively shorten the distance between the positive and negative electrodes, and increase the energy density per unit area. In terms of electrode structure configuration, the shorter the ion transmission distance, the more conducive it is to low resistance and rapid ion diffusion dynamics. In the periodic configuration design, the fractal curve continuously stretches, compresses, and twists the spatial object without changing the dimension. The regular fractals in the fractal curve have strict self-similarity and tight space filling properties, and have the characteristics of high clustering and strong continuity, achieving the goal of optimizing the energy density of the electrode in a given area, while providing a stable structural guarantee for the electrode and giving the electrode multi-directional stretchability.

[0052] Preferably, the gel electrolyte includes one or more of a PMMA-based polymer gel electrolyte and a PVDF-HFP / NPGDA polymer gel electrolyte.

[0053] More preferably, the initiator accounts for 0.1-1.0 wt % in the raw materials of the gel electrolyte.

[0054] Preferably, the flexible substrate is polydimethylsiloxane (PDMS).

[0055] Preferably, the battery system applicable to the 3D inkjet-printed multi-directional stretchable battery includes one or more of lithium-ion batteries, sodium-ion batteries, zinc-ion batteries, and lithium-sulfur batteries.

[0056] Preferably, the printed circuit configuration in the 3D inkjet-printed multi-directional stretchable battery includes one or more of a concentric circle type, a Peano curve type, a Hilbert curve type, a square type, and a spiral type.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] 1. The elastic current collector printing ink of the present invention uses a carbon nanotube-grafted graphene conductive composite material with a three-dimensional network structure of graphene and carbon nanotubes connected by Ni metal nanoparticles as nodes as a raw material, which gives the material ultra-high conductivity while giving it good deformation ability and stretchability.

[0059] 2. The elastic current collector printing ink of the present invention needs to adjust the viscosity so that it can meet the conditions of 3D printing.

[0060] 3. The elastic current collector printing ink of the present application can be mixed with positive / negative active materials to prepare positive / negative printing ink, which together constitute a battery.

[0061] 4. The preparation method adopted by the present application is simple, highly operable and low in cost, avoids the generation of strong acid waste liquid in the process of preparing graphene by traditional redox method, and is beneficial to large-scale production.

[0062] 5. The present application adopts 3D printing technology, reasonably plans the path configuration of positive and negative electrodes based on fractal curves with high clustering and strong continuity, realizes the goal of optimizing the energy density of electrodes in a given area, at the same time provides stable structural guarantee for electrodes, and endows electrodes with multi-directional stretchability. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 TEM electron micrograph of the carbon nanotube grafted graphene conductive composite material prepared in Example 1 of the present application.

[0064] Figure 2 Schematic diagram of the integrated carbon nanotube grafted graphene conductive composite material prepared in Example 1 of the present application.

[0065] Figure 3 Schematic diagram of the printing structure configuration of the Hilbert fractal curve structure adopted in Example 1 of the present application.

[0066] BRIEF DESCRIPTION OF DRAWINGS: 1. Carbon nanotube, 2. Metal nickel nanoparticles, 3. Graphene. DETAILED DESCRIPTION

[0067] The following are specific embodiments of the present application, which further describe the technical solutions of the present application, but the present application is not limited to these embodiments.

[0068] Example 1

[0069] Weigh 1.98g of glucose, 0.35g of nickel nitrate, and 1.51g of ammonium chloride in a mortar and grind them evenly. Add an equal amount of deionized water, stir thoroughly, dry in the shade, and continue drying in a vacuum drying oven at 60°C for 12 hours. Transfer the resulting mixed powder to a mortar and grind it evenly to obtain a mixed powder. Weigh 53.6g of potassium chloride and 46.5g of sodium chloride and add them to an agate ball mill at 300 rpm. Grind for 1 hour to obtain a binary salt system. After ball milling, mechanically stir the materials from the first two steps in the mortar. After mixing evenly, transfer them to a square quartz boat and preheat them in a forced air dryer at 100°C for 8 hours. Then, the sample was transferred to a tube furnace and rapidly heated to a first temperature of 1000°C at a rate of 5°C / min in an argon atmosphere. The sample was kept at this temperature for 60 minutes, and then the heating was stopped. The sample was naturally cooled to 950°C, and the acetylene gas channel was switched to. The heating was restarted and the sample was kept at a second temperature of 950°C for 30 minutes. The sample was then stopped and switched to the argon gas channel again until it dropped to room temperature. The entire cooling process was protected by an argon atmosphere. The product was removed and washed with deionized water five times to remove salt. The sample was vacuum annealed at 80°C for 24 hours to obtain a carbon nanotube-grafted graphene conductive composite material (CNT-g-Gr). The TEM image of the composite is shown in FIG. Figure 1 As shown; its schematic diagram is as Figure 2 Then, 16.5 mg of carbon nanotube-grafted graphene conductive composite (CNT-g-Gr) and 50 mg of sodium dodecylbenzenesulfonate were taken, and 10 mL of deionized water was measured. After magnetic stirring, the mixture was ultrasonicated at 300 W for 30 minutes to prepare a CNT-g-Gr dispersion. Then, a polystyrene-polymethyl acrylate-polystyrene emulsion was slowly added dropwise to the CNT-g-Gr dispersion to adjust the CNT-g-Gr solid content in the conductive elastomer to 5 wt%. The mixture was magnetically stirred for 15 minutes, and the viscosity was adjusted to 30 Pa·s to obtain an elastic current collector printing ink.

[0070] Positive / negative electrode active materials were weighed in a mass ratio of 7:1, SuperP was used as a conductive additive, polystyrene-polymethyl acrylate-polystyrene emulsion was used as a binder, and deionized water was used as a dispersion medium. Magnetic stirring was performed for a period of time. By adjusting the amount of binder and dispersion medium, the viscosity of the printing ink was 30 Pa·s to prepare the positive / negative electrode printing ink.

[0071] The SolidWorks software was used to establish the Hilbert fractal curve structure model, and the printer auxiliary software Repetier-Host was imported. The current collector printing ink was loaded into the needle cylinder, the movement of the printing nozzle was controlled through the software control, the ink was shaped on the surface of the polydimethylsiloxane (PDMS) flexible substrate, then the needle cylinder was replaced, and the positive / negative electrode printing ink was added respectively, and the printed current collector was covered with the printed positive / negative electrode of the Hilbert fractal curve configuration structure battery. The area of the printed electrode region was 2 cm x 2 cm, the printing thickness of the current collector was 100 μm, the printing thickness of the positive and negative electrodes was 100 μm and 110 μm respectively, the methyl methacrylate (MMA) monomer, methyl acrylate (MA) soft monomer and initiator azobis (isobutyrylnitrile) (ABVN) were weighed in a beaker according to the mass ratio of 9:1, the initiator accounted for 0.4wt% of the total mass, sealed with plastic wrap, and subjected to polymerization reaction in a 55°C oven for 5h, and then dried in a vacuum drying oven at 110°C to remove unreacted monomers. The material was cut into small pieces with a volume suitable for the circuit, soaked in 1 mol / L LiPF6 EC+DMC+EMC (1:1:1) electrolyte for 10 min, and PMMA-based polymer gel electrolyte was obtained. The gel electrolyte was filled between the positive / negative electrode lines, and finally packaged with a PDMS film to obtain a multi-directional stretchable battery with Hilbert fractal curve structure configuration. The structure, current collector, positive / negative electrode printing line configuration structure diagram is shown in Figure 3

[0072] The performance of the prepared multi-directional stretchable battery was tested, and the change of the surface conductivity remained basically the same after being stretched at different angles. The initial capacity of the battery was 3.57 mAh without stretching, the capacity remained 95.6% when the stretching deformation was 30%, and the capacity remained 60.7% when the stretching deformation was 100%.

[0073] Example 2

[0074] Compared with Example 1, the difference lies in that the polymer emulsion in the elastic current collector printing ink and the positive / negative electrode printing ink is polystyrene-ethylene-butylene-styrene emulsion. The performance of the prepared multi-directional stretchable battery was tested, and the change of the surface conductivity remained basically the same after being stretched at different angles. The initial capacity of the battery was 3.42 mAh without stretching, the capacity remained 92.1% when the stretching deformation was 30%, and the capacity remained 55.6% when the stretching deformation was 100%.

[0075] Example 3

[0076] ​Compared to Example 1, the difference lies in the configuration of the printed electrode structure of the elastic current collector as a Peano fractal curve. The resulting multi-directionally stretchable battery was subjected to performance testing, and the changes in its surface conductivity remained essentially consistent after being stretched at different angles. When unstretched, the battery had an initial capacity of 3.35 mAh. When stretched to 30%, the battery retained 93.3% of the capacity; when stretched to 100%, it still retained 59.4% of the capacity.

[0077] Example 4

[0078] Compared to Example 1, the difference lies in the CNT-g-Gr solid content of 2 wt%. The resulting multi-directionally stretchable battery was subjected to performance testing, and the changes in its surface conductivity remained essentially consistent after being stretched at different angles. When unstretched, the battery had an initial capacity of 3.52 mAh. When stretched to 30%, the battery retained 80.4% of its capacity, and when deformed to 100%, it still retained 50.1% of its capacity.

[0079] Example 5

[0080] Compared to Example 1, the difference lies in the CNT-g-Gr solid content of 10 wt%. The resulting multi-directionally stretchable battery was subjected to performance testing, and the changes in its surface conductivity remained essentially consistent after being stretched at different angles. When unstretched, the battery had an initial capacity of 3.55 mAh. When stretched to 30%, the battery retained 88.7% of its capacity, and when deformed to 100%, it still retained 56.4% of its capacity.

[0081] Example 6

[0082] Compared to Example 1, the difference lies in the CNT-g-Gr solid content of 20wt%. The resulting multi-directionally stretchable battery was subjected to performance testing, and the changes in its surface conductivity remained essentially consistent after being stretched at different angles. When unstretched, the battery had an initial capacity of 3.59 mAh. When stretched to 30%, the battery retained 72.8% of its capacity, and when deformed to 100%, it still retained 51.2% of its capacity.

[0083] Example 7

[0084] Compared to Example 1, the difference lies in the CNT-g-Gr solid content of 25wt%. The resulting multi-directionally stretchable battery was subjected to performance testing. After being stretched at different angles, the changes in its surface conductivity remained essentially the same. When the deformation reached 30%, the battery retained 50.7% of its capacity; at 100% deformation, the battery ceased to function properly.

[0085] Comparative Example 1

[0086] Compared with Example 1, the difference is that the nanotube-grafted graphene conductive composite material (CNT-g-Gr) is replaced by a graphene and metal nickel nanoparticle composite material. The preparation method of the graphene and metal nickel nanoparticle composite material includes: weighing 1.98g glucose, 0.22g nickel chloride, and 1.51g ammonium chloride in a mortar and grinding them evenly, adding an equal mass of deionized water, stirring thoroughly, drying in the shade, and then placing it in a vacuum drying oven at 60°C for further drying for 12h, transferring the resulting solid to a mortar, grinding evenly, and standby. Then weigh 53.6g potassium chloride and 44.6g sodium chloride, add them together to an agate ball mill, the ball mill speed is 300rpm, and grinding for 1h. After the ball milling is completed, the materials of the first two steps are mechanically stirred in a mortar, mixed evenly, and transferred to a square quartz boat, and pretreated at a constant temperature of 100°C in a blast dryer for 8h. Transfer to a tubular furnace, rapidly heat to 900°C at 5°C / min, treat for 60 minutes, then stop heating, cool naturally, and protect in an argon atmosphere throughout the process. Take out the product, wash it repeatedly with deionized water to remove salt, and vacuum dry it at 80°C for 24 hours to obtain a composite material of graphene and metal nickel nanoparticles. Then, a multi-directional stretchable battery was prepared according to the method of Example 1, and its performance was tested. When not stretched, the initial capacity of the battery was 3.54mAh. When the stretching deformation was 30%, the battery maintained 70.3% of its capacity; when the deformation was 100%, it still maintained 29.8% of its capacity.

[0087] Comparative Example 2

[0088] Compared with Example 1, the difference is that the nanotube-grafted graphene conductive composite material (CNT-g-Gr) is replaced with a nitrogen-doped graphene material. The preparation method of the nitrogen-doped graphene material includes: weighing 1.98g glucose and 1.51g ammonium chloride in a mortar and grinding them evenly, adding equal mass deionized water, stirring thoroughly, drying in the shade, and then placing in a vacuum drying oven at 60°C and continuing to dry for 12h, the resulting solid is transferred to a mortar, ground evenly, and stand-by. Then weigh 53.6g potassium chloride and 45.6g sodium chloride, add them to an agate ball mill, the ball mill speed is 300rpm, and the ball mill is milled for 2h. After the ball milling is completed, the materials of the first two steps are mechanically stirred in a mortar, mixed evenly, and transferred to a square quartz boat, and pretreated at a constant temperature for 8h at 100°C in a blast dryer. Transfer to a tube furnace, rapidly heat to 800°C at 5°C / min, treat for 60min, then stop heating, cool naturally, and protect under argon atmosphere throughout the process. The product was removed, repeatedly washed with deionized water to remove salt, filtered, and vacuum-dried at 80°C for 24 hours to produce nitrogen-doped graphene. A multi-directionally stretchable battery was then prepared according to the method of Example 1 and its performance was tested. When unstretched, the battery had an initial capacity of 3.53 mAh. When stretched to 30%, the battery retained 60.8% of its capacity; when deformed to 100%, it still retained 26.4% of its capacity.

[0089] In summary, the elastic current collector printing ink of the present invention contains a carbon nanotube grafted graphene conductive composite material (CNT-g-Gr), so that the multi-directional stretchable battery obtained after subsequent 3D printing has excellent stretchability and can still maintain good conductivity under stretching (deformation) conditions.

[0090] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A 3D inkjet printed multi-directional stretchable battery, characterized in that: include: Flexible substrate; An elastic current collector printing ink layer is printed on the surface of a flexible substrate; Positive / negative electrode printing ink layer, which is printed on the surface of the elastic current collector printing ink layer; and a gel electrolyte filling layer, which is filled between the positive / negative electrode lines; The 3D inkjet-printed multi-directional stretchable battery is manufactured by controlling the movement of the printing nozzle through software to form an elastic current collector printing ink on the surface of a flexible substrate, then covering it with positive / negative electrode printing ink to obtain positive / negative electrodes, and filling the positive / negative electrode circuits with a gel electrolyte, and then encapsulating it. The preparation method of the elastic current collector printing ink comprises: adding a polymer emulsion dropwise into a dispersion liquid consisting of a carbon nanotube-grafted graphene conductive composite material, a surfactant, and deionized water, and adjusting the viscosity to obtain the elastic current collector printing ink; The carbon nanotube-grafted graphene conductive composite material is a three-dimensional network structure, with Ni metal nanoparticles as nodes connecting graphene and carbon nanotubes; The preparation method of the carbon nanotube-grafted graphene conductive composite material includes: mixing glucose monohydrate, ammonium chloride, divalent nickel inorganic acid salt and deionized water, drying and grinding to obtain a mixed powder, adding the mixed powder to a binary salt system consisting of sodium chloride and potassium chloride and preheating the mixed powder, transferring the preheated material to a tubular furnace and keeping it warm in an argon atmosphere, switching to an acetylene gas channel and continuing to keep it warm, then switching to an argon gas channel and cooling it to room temperature, washing and drying it to obtain the carbon nanotube-grafted graphene conductive composite material.

2. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The positive / negative electrode printing ink is made of positive / negative electrode active materials, a conductive agent, a binder, and a dispersant; The mass ratio of the positive / negative electrode active material, the conductive agent, and the binder is (70-80): (10-20): (10-20).

3. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The solid content of the carbon nanotube-grafted graphene conductive composite material in the elastic current collector printing ink is 2-20 wt %; and the viscosity of the elastic current collector printing ink is 13-35 Pa·s.

4. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The mass ratio of the carbon nanotube-grafted graphene conductive composite material, the polymer emulsion and the surfactant is (1-10): (0.5-20): (1-20).

5. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The preheating temperature is 100-200° C., and the preheating time is 5-24 hours.

6. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The temperature for insulation in argon gas atmosphere is the first temperature, and the insulation time is the first insulation time; the temperature for insulation in acetylene gas atmosphere is the second temperature, and the insulation time is the second insulation time.

7. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The polymer in the polymer emulsion includes one or more of polystyrene-ethylene-butylene-styrene, polystyrene-polymethyl acrylate-polystyrene, and polystyrene-polybutyl acrylate-polystyrene.

8. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The surfactant is sodium lauryl sulfate.

9. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The gel electrolyte includes one or more of a PMMA-based polymer gel electrolyte and a PVDF-HFP / NPGDA polymer gel electrolyte.

10. The 3D inkjet printed multi-directional stretchable battery according to claim 1, characterized in that: The flexible substrate is polydimethylsiloxane.

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