Current collector-free, self-supporting three-dimensional lithium-ion batteries and 3D printing method thereof

Abstract

This invention provides a current collector-free, self-supporting three-dimensional lithium-ion battery, comprising a positive electrode and a negative electrode. The positive and negative electrodes have an internal cross structure and extend outward in a rectangular spiral pattern. During the extension process, the positive and negative electrodes remain parallel, and the distance between them remains constant. This invention also provides a 3D printing method for the aforementioned current collector-free, self-supporting three-dimensional lithium-ion battery. The advantages of this invention are: it provides a current collector-free, self-supporting three-dimensional lithium-ion battery, eliminating the need for current collectors such as copper or aluminum foil; the manufacturing process has good scalability; and it can significantly increase the proportion of active materials in the lithium-ion battery, thereby improving energy density and power density.

Description

Technical Field

[0001] This invention relates to 3D printed lithium-ion batteries, and more particularly to a current collector-free, self-supporting three-dimensional lithium-ion battery and its 3D printing method. Background Technology

[0002] Lithium-ion batteries are among the most important energy storage devices currently available. How to manufacture lithium-ion batteries with higher energy density and power density is a key focus of the industry.

[0003] Existing lithium-ion batteries employ a coating method to coat active materials onto copper or aluminum foil. Examples of positive electrode active materials include LiFePO4, LiMn2O4, LiCoO2, Ni-Co-Mn, and Ni-Co-Al ternary materials, which are coated onto aluminum foil to prepare the positive electrode sheet. Negative electrode active materials include graphite and Li4Ti5O4. 12 Silicon and its oxides are coated onto copper foil to prepare the negative electrode sheet; the positive electrode sheet, separator, and negative electrode sheet are then stacked or wound to form a battery. In this type of battery, the thickness of the active material on the positive and negative electrode sheets is less than 100 micrometers. When the thickness is greater than 100 micrometers, the diffusion distance of lithium ions in the electrode increases and the diffusion rate slows down, which seriously affects the power density.

[0004] Because the active material on the electrode is less than 100 micrometers thick, a large amount of copper and aluminum foil, each about 10 micrometers thick, is needed as current collectors. A large amount of separator, about 25 micrometers thick, is also required to separate and insulate the positive and negative electrodes, preventing short circuits. Both the current collectors and separators are inactive materials that do not provide effective energy, but they occupy battery volume and weight, severely impacting energy density and power density.

[0005] 3D-printed three-dimensional lithium-ion batteries alter the electrode structure, changing the diffusion path of lithium ions within the electrodes. This increases the thickness of the active material while minimizing or preventing the increase in lithium ion diffusion distance, thereby achieving the goal of simultaneously improving energy density and power density.

[0006] Currently, the two most common three-dimensional lithium-ion battery structures are: ① Using a mesh-like porous three-dimensional electrode, that is, introducing vertically penetrating holes in an electrode with a thickness of mm to serve as a fast channel for lithium-ion diffusion, avoiding the diffusion of lithium-ions inside the tortuous electrode; ② Using a cross-type structure of positive and negative electrodes, which allows lithium-ions to diffuse laterally between the positive and negative electrodes. When the electrode thickness increases, the lithium-ion diffusion distance remains unchanged, thereby effectively improving the lithium-ion diffusion rate and increasing the power density.

[0007] While the two types of three-dimensional lithium-ion batteries mentioned above can alleviate the contradiction between energy density and power density to some extent, they still have significant drawbacks. For the mesh-like porous three-dimensional electrode, the disadvantage is that although the vertical pores introduced into the electrode can improve the diffusion rate of lithium ions, the presence of these pores simultaneously reduces the energy density of the battery; therefore, the introduction of pores is a double-edged sword. For the positive and negative electrode cross-type battery, the disadvantages are that the assembly of the positive and negative electrodes is difficult, and the assembly process can easily cause electrode damage. In addition, this structure makes it difficult to stack and wind the electrode sheets, resulting in poor process scalability. Summary of the Invention

[0008] To address the problems in the prior art, this invention provides a current collector-free, self-supporting three-dimensional lithium-ion battery and its 3D printing method. It eliminates the need for current collectors such as copper foil and aluminum foil, has good scalability in manufacturing processes, and can significantly increase the proportion of active materials in lithium-ion batteries, thereby improving energy density and power density.

[0009] This invention provides a current collector-free, self-supporting three-dimensional lithium-ion battery, comprising a positive electrode and a negative electrode. The positive and negative electrodes have an internal cross structure and an external rectangular spiral extending outward. During the extension process, the positive and negative electrodes remain parallel and the distance between them remains constant.

[0010] As a further improvement of the present invention, the interior of the positive electrode is a positive electrode rectangular serration with at least two fins, and the interior of the negative electrode is a negative electrode rectangular serration with at least two fins and an opening direction opposite to that of the positive electrode rectangular serration. The positive electrode rectangular serration is inserted into the groove formed by the negative electrode rectangular serration.

[0011] As a further improvement of the present invention, the outer part of the positive electrode is a positive rectangular spiral extending from the inside to the outside, and the outer part of the negative electrode is a negative rectangular spiral extending from the inside to the outside. The positive rectangular spiral is inserted into and nested within the spiral groove formed by the negative rectangular spiral.

[0012] As a further improvement of the present invention, both the positive electrode and the negative electrode adopt a three-dimensional self-supporting structure and are not attached to the current collector.

[0013] As a further improvement of the present invention, the positive and negative electrodes contain sufficient conductive agents, which have excellent conductivity, and the electrodes themselves can be used as current collectors.

[0014] As a further improvement of the present invention, a membrane is filled between the positive electrode and the negative electrode. The membrane can separate the positive electrode and the negative electrode to prevent them from directly contacting each other and causing a short circuit.

[0015] As a further improvement of the present invention, the linewidth of both the positive and negative electrodes is 50 micrometers to 300 micrometers, and the gap between the positive and negative electrodes is 20 micrometers to 200 micrometers.

[0016] As a further improvement of the present invention, the combined structure formed by the positive electrode, the negative electrode, and the separator is called a battery cell, and its total thickness is 500 micrometers to 10 millimeters.

[0017] This invention also provides a 3D printing method for the aforementioned current collector-free, self-supporting three-dimensional lithium-ion battery, comprising the following steps:

[0018] S1. The positive electrode is printed using positive electrode paste;

[0019] S2. Using negative electrode paste, the negative electrode is printed in the gap between the positive electrodes;

[0020] S3. Using diaphragm slurry, a diaphragm is printed between the positive and negative electrodes.

[0021] As a further improvement of the present invention, the positive electrode slurry includes:

[0022] The active material has a mass percentage of 40wt% to 70wt%, the conductive agent has a mass percentage of 20wt% to 50wt%, and the adhesive has a mass percentage of 2wt% to 5wt%.

[0023] The negative electrode slurry comprises: 40wt% to 70wt% active material, 20wt% to 50wt% conductive agent, and 2wt% to 5wt% binder.

[0024] The diaphragm slurry comprises: 5 wt% to 8 wt% polyvinylidene fluoride hexafluoropropylene copolymer, 90 wt% acetone, and 1 wt% to 3 wt% deionized water.

[0025] As a further improvement of the present invention, the active material of the positive electrode slurry is any one or any combination of LiFePO4, LiMn2O4, LiCoO2, Ni-Co-Mn, and Ni-Co-Al.

[0026] As a further improvement of the present invention, the conductive agent of the positive electrode slurry is any one of carbon black, carbon nanotubes, graphene, or any combination thereof.

[0027] As a further improvement of the present invention, the binder of the positive electrode slurry is any one or any combination of polyvinylidene fluoride, sodium hydroxymethyl cellulose, and styrene-butadiene rubber.

[0028] As a further improvement of the present invention, the active material of the negative electrode slurry is graphite or Li4Ti5O. 12Any one or any combination of silicon and its oxides.

[0029] As a further improvement of the present invention, the conductive agent of the negative electrode slurry is any one or any combination of carbon black, carbon nanotubes, and graphene.

[0030] As a further improvement of the present invention, the binder of the negative electrode slurry is any one of sodium hydroxymethyl cellulose and styrene-butadiene rubber, or any combination thereof.

[0031] As a further improvement of the present invention, it also includes step S4: coating the end positions of the positive and negative electrodes with conductive silver paste, connecting the tabs to the coated conductive silver paste, and curing at a temperature of 60°C to 80°C to form a battery cell.

[0032] As a further improvement of the present invention, step S5 is also included: using an aluminum-plastic film shell to soft-pack the battery cell and injecting sufficient electrolyte into the package.

[0033] As a further improvement of the present invention, the positive electrode, negative electrode and separator are all manufactured by extrusion 3D printing.

[0034] The beneficial effects of this invention are: it provides a current collector-free, self-supporting three-dimensional lithium-ion battery that does not require current collectors such as copper foil or aluminum foil, has good scalability in manufacturing process, and can significantly increase the proportion of active materials in lithium-ion batteries, thereby improving energy density and power density. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other solutions can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of a current collector-free, self-supporting three-dimensional lithium-ion battery according to the present invention.

[0037] Figure 2 This is a flowchart of the main process of a 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery according to the present invention.

[0038] Figure 3 This is a complete flowchart of a 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery according to the present invention. Detailed Implementation

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 As shown, a current collector-free, self-supporting three-dimensional lithium-ion battery includes a positive electrode 1, a negative electrode 2, and a separator 3. The positive electrode 1 and the negative electrode 2 have an internal cross structure, and the positive electrode 1 and the negative electrode 2 extend outward in a rectangular spiral on the outside. During the extension process, the positive electrode and the negative electrode always remain parallel, and the distance between the positive electrode and the negative electrode remains unchanged.

[0044] The interior of the positive electrode 1 is a rectangular serration 101 with multiple (at least two) fins, and the interior of the negative electrode 2 is a rectangular serration 201 with multiple (at least two) fins, with the opening direction opposite to that of the rectangular serration 101. The rectangular serration 101 is inserted into the groove formed by the rectangular serration 201, forming an intersecting structure between the interiors of the positive electrode 1 and the negative electrode 2.

[0045] The number of fins in the positive rectangular serration 101 can be designed as needed, and the number of fins in the negative rectangular serration 201 can be designed as needed. The fins of the two are arranged in a cross structure.

[0046] The positive electrode 1 is surrounded by a rectangular spiral 102 extending from the inside out, and the negative electrode 2 is surrounded by a rectangular spiral 202 extending from the inside out. The rectangular spiral 102 is nested within the spiral groove formed by the rectangular spiral 202.

[0047] Positive electrode 1 and negative electrode 2 have a three-dimensional self-supporting structure and do not need to be attached to the current collector.

[0048] The positive electrode 1 and the negative electrode 2 contain sufficient conductive agent and have excellent conductivity. The electrodes themselves can be used as current collectors.

[0049] The diaphragm 3 fills the gap between the positive electrode 1 and the negative electrode 2, separating the positive and negative electrodes and preventing them from directly contacting each other and causing a short circuit.

[0050] The linewidth of both the positive and negative electrodes is 50 micrometers to 300 micrometers, preferably 50 micrometers, 100 micrometers, 200 micrometers or 300 micrometers.

[0051] The gap between the positive and negative electrodes is 20 micrometers to 200 micrometers, preferably 20 micrometers, 80 micrometers, 100 micrometers or 200 micrometers.

[0052] like Figures 2 to 3 As shown, a 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery mainly includes the following processes:

[0053] The first step is to load the positive electrode printing paste 10 into the printing nozzle, and then print layer by layer according to the structure of the positive electrode to complete the manufacturing of the positive electrode 1;

[0054] The second step is to load the negative electrode printing paste 20 into the printing nozzle, and then print layer by layer according to the negative electrode structure to complete the manufacturing of the negative electrode 2.

[0055] The third step is to load the diaphragm slurry 30 into the printing nozzle, and then print layer by layer according to the diaphragm structure to complete the manufacturing of the diaphragm 3.

[0056] The fourth step is to coat the head positions reserved for positive electrode 1 and negative electrode 2 with conductive silver paste 4.

[0057] Fifth step, connect the positive electrode tab 5 to the conductive silver paste at the positive electrode position, and connect the negative electrode tab 6 to the conductive silver paste at the negative electrode position;

[0058] The sixth step is to cure the combined structure consisting of positive electrode 1, negative electrode 2, separator 3, conductive silver paste 4, positive electrode tab 5 and negative electrode tab 6 at a temperature of 60℃~80℃, preferably at a temperature of 60℃, 70℃ or 80℃.

[0059] Step 7: Install tab adhesive 7 between the positive electrode tab 5 and the negative electrode tab 6 to form a complete cell structure;

[0060] The eighth step is to encapsulate the cell structure using a soft-pack packaging method, fill the inside of the battery with electrolyte, and complete the battery manufacturing process.

[0061] The first to third steps described above all use extrusion 3D printing.

[0062] This invention proposes a 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery. The printing paste involved and its composition are as follows:

[0063] 1. The positive electrode slurry composition is as follows: the active material is LiFePO4, LiMn2O4, LiCoO2, Ni-Co-Mn, Ni-Co-Al ternary materials, etc., with a mass percentage of 40wt%~70wt%, preferably 40wt%, 60wt% or 70wt%; the conductive agent is carbon black, carbon nanotubes, graphene, etc., with a mass percentage of 20wt%~50wt%, preferably 20wt%, 30wt% or 50wt%; the binder is polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, etc., with a mass percentage of 2wt%~5wt%, preferably 2wt%, 3wt% or 5wt%;

[0064] 2. The composition of the negative electrode printing paste is: the active material is graphite and Li4Ti5O. 12 Silicon and its oxides, etc., with a mass percentage of 40wt%~70wt%, preferably 40wt%, 60wt% or 70wt%; conductive agents such as carbon black, carbon nanotubes, graphene, etc., with a mass percentage of 20wt%~50wt%, preferably 20wt%, 30wt% or 50wt%; binders such as sodium carboxymethyl cellulose, styrene-butadiene rubber, etc., with a mass percentage of 2wt%~5wt%, preferably 2wt%, 3wt% or 5wt%.

[0065] 3. The diaphragm slurry consists of: polyvinylidene fluoride hexafluoropropylene copolymer, with a mass percentage of 5wt%~8wt%, preferably 5wt%, 6wt% or 8wt%; acetone, with a mass percentage of 90wt%; and deionized water, with a mass percentage of 1wt%-3wt%, preferably 1wt%, 2wt% or 3wt%.

[0066] This invention proposes a self-supporting lithium-ion battery structure without a current collector and its 3D printing manufacturing method. The battery cell consists of a positive electrode, a negative electrode, and a separator. The internal core of the positive and negative electrodes has a cross-shaped structure, while the outer surface has a rectangular spiral structure. As the positive and negative electrodes spiral outwards, they remain parallel. The separator fills the gap between the positive and negative electrodes, always separating them and preventing short circuits. This type of electrode achieves self-support without a current collector. The elimination of a current collector significantly reduces the weight of the battery cell, effectively improving the specific gravimetric energy density. Furthermore, since the battery is mostly composed of active materials, the specific volumetric energy density is effectively improved. The battery is manufactured using 3D printing, and the electrodes incorporate 20wt%-50wt% conductive agent to ensure good conductivity, with the electrodes themselves acting as current collectors. The lithium-ion battery structure proposed in this invention has the advantage of high energy density.

[0067] The present invention proposes a 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery, the specific implementation steps of which are as follows:

[0068] Implementation Step 1 – Slurry Preparation

[0069] (1) Preparation of cathode material: First, LFP powder was ball-milled using a horizontal planetary ball mill for 4 hours at 16 Hz, 2 hours at 24 Hz, and then 12 hours at 16 Hz, for a total of about 24 hours. This reduced the particle size of the LFP powder, which was then filtered through an 80-mesh sieve to obtain LFP powder. CMC was used as a binder, and solvent was measured at a ratio of 1:3 (deionized water to dioxane) and placed in a beaker for mixing. The mixture was stirred using a magnetic stirrer. During the stirring process, an appropriate amount of carbon nanotube dispersant was added, and after mixing evenly, MWCNTs were weighed and placed in the beaker. After stirring for five minutes, the MWCNTs solution was ultrasonically dispersed, with the ultrasonic cycle being 3 seconds on and 3 seconds off, for a total of 40 minutes. The beaker was then removed, an appropriate amount of CMC was added, and the beaker was sealed with sealing glue. The mixture was then placed in a magnetic stirrer and stirred for 12 hours. After 12 hours, the evenly mixed solution was placed in a vacuum mixing tank, and the ball-milled and sieved LFP powder was weighed and mixed. Stir at 100 rpm for 90 min, 300 rpm for 120 min, and 600 rpm for 45 min. After stirring, remove the mixing tank, add an appropriate amount of SBR solution, and manually stir with a glass rod until evenly mixed. Then continue vacuum stirring at 150 rpm for 50 min. Finally, remove the mixture to obtain a uniformly stirred three-dimensional lithium-ion battery cathode slurry with suitable viscosity.

[0070] (2) Preparation of negative electrode material: The preparation process of negative electrode slurry is basically the same as that of positive electrode slurry. LTO powder was ball-milled using a planetary ball mill for 4 hours at 16 Hz, 2 hours at 24 Hz, and then 1 hour at 16 Hz, for a total of about 24 hours. CMC was used as a binder. A 50 mL beaker was used to measure deionized water and 1-4 dioxane as solvents and mixed. At the same time, CNT was ultrasonically dispersed. After dispersion, it was added to a 50 mL beaker and stirred with a magnetic stirrer for 12 hours. After stirring, it was removed and placed in a three-stage vacuum mixing tank. After stirring, the mixing tank was removed, SBR was added and mixed, and vacuum stirring was continued. Finally, the three-dimensional lithium-ion battery negative electrode slurry was obtained.

[0071] (3) Preparation of membrane material: The membrane is prepared using liquid phase separation method, with PVDF-HFP as the main material, acetone as the solvent, and deionized water as the non-solvent. A certain amount of acetone is measured, and a certain amount of PVDF-HFP is weighed and dissolved in acetone. After sealing with sealing glue, the membrane is placed in a magnetic stirrer for magnetic stirring. During the stirring process, 1-3 wt% of deionized water is added until the mixture is uniformly stirred to obtain a PVDF-HFP solution with a concentration of 5 wt% to 8 wt%.

[0072] Implementation Step 2 – Printing Process

[0073] Before printing, the printing chamber temperature was lowered to below -10℃. Custom printing parameters were set: printhead scanning speed of 6 mm / s, printhead extrusion speed of 0.003 mm / s, and layer thickness of 0.15 mm. The prepared positive and negative electrode slurries were drawn using a syringe. A diaphragm was taken, and the negative electrode was printed first on the diaphragm. After printing, the printhead was changed to a different slurry, and the printhead extrusion speed was changed to 0.004 mm / s. The positive electrode was continuously printed at low temperature until it formed a cross structure with the negative electrode. Finally, the printhead was changed again, the printhead scanning speed was changed to 3 mm / s, and the printhead extrusion speed was changed to 0.001 mm / s. The diaphragm was then printed in the gap between the positive and negative electrode cross structure. At this point, the current collector-less electrode structure was completely printed. The electrodes were then placed in a vacuum drying oven and removed after 12 hours. The printed substrate diaphragm was then separated from the electrodes.

[0074] Implementation Step 3 – Battery Packaging

[0075] Using a dropper, apply appropriate amounts of conductive silver paste to the extended ends of the positive and negative electrodes, respectively. Then, connect copper wires to the conductive silver paste to form tabs. The assembly consisting of the positive and negative electrodes, separator, conductive silver paste, and copper wires is then placed in a drying oven and cured at 60℃~80℃. After curing, remove the assembly and apply tab adhesive to the positive and negative tabs. Finally, use an aluminum-plastic film for soft-pack encapsulation. Inject sufficient electrolyte into the encapsulated battery to complete the battery manufacturing process.

[0076] The present invention proposes a current collector-free, self-supporting three-dimensional lithium-ion battery and its 3D printing method, which have the following advantages:

[0077] 1. The positive and negative electrodes of the battery proposed in this invention contain sufficient conductive agents, and the electrodes themselves have excellent conductivity, which can conduct electricity from the battery. There is no need for high-density metal materials such as copper foil and aluminum foil, which effectively reduces the weight of the battery and increases the specific energy density of the battery.

[0078] 2. The positive and negative electrodes in the battery proposed in this invention are three-dimensional structures. The electrodes themselves have a self-supporting function and do not require metal current collectors such as copper foil and aluminum foil as support. They have excellent mechanical properties and mechanical strength, which can ensure that the battery has excellent structural stability.

[0079] 3. In the battery proposed in this invention, the positive and negative electrodes always maintain an equidistant and synchronous cross shape, and expand outward in an equidistant and synchronous spiral. Therefore, lithium ions can diffuse laterally between the positive and negative electrodes with the minimum distance, avoiding long-distance diffusion of lithium ions, which can improve the diffusion rate of lithium ions and help improve the power density of the battery.

[0080] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A current collector-free, self-supporting three-dimensional lithium-ion battery, comprising a positive electrode and a negative electrode, characterized in that: The positive and negative electrodes have an internal cross structure, and their external surfaces extend outward in a rectangular spiral. During this extension process, the positive and negative electrodes remain parallel, and the distance between them remains constant. The positive electrode has a rectangular serration with at least two fins inside, and the negative electrode has a rectangular serration with at least two fins inside, with the opening direction opposite to that of the positive electrode rectangular serration. The positive electrode rectangular serration is inserted into the groove formed by the negative electrode rectangular serration. The positive electrode has an outer rectangular spiral extending from the inside out, and the negative electrode has an outer rectangular spiral extending from the inside out. The positive rectangular spiral is nested within the spiral groove formed by the negative rectangular spiral. Both the positive and negative electrodes adopt a three-dimensional self-supporting structure and are not attached to the current collector. Both the positive and negative electrodes contain a conductive agent and can be used as current collectors.

2. The current collector-free, self-supporting three-dimensional lithium-ion battery according to claim 1, characterized in that: A membrane is filled between the positive electrode and the negative electrode, and the membrane can separate the positive electrode and the negative electrode.

3. A 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery as described in claim 1 or 2, characterized in that, Includes the following steps: S1. The positive electrode is printed using positive electrode paste; S2. Using negative electrode paste, the negative electrode is printed in the gap between the positive electrodes; S3. Using diaphragm slurry, a diaphragm is printed between the positive and negative electrodes.

4. The 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery according to claim 3, characterized in that: The positive electrode slurry includes: The active material has a mass percentage of 40wt% to 70wt%, the conductive agent has a mass percentage of 20wt% to 50wt%, and the adhesive has a mass percentage of 2wt% to 5wt%. The negative electrode slurry comprises: 40wt% to 70wt% active material, 20wt% to 50wt% conductive agent, and 2wt% to 5wt% binder. The diaphragm slurry comprises: 5 wt% to 8 wt% polyvinylidene fluoride hexafluoropropylene copolymer, 90 wt% acetone, and 1 wt% to 3 wt% deionized water.

5. The 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery according to claim 4, characterized in that: The active material of the positive electrode slurry is any one or any combination of LiFePO4, LiMn2O4, LiCoO2, Ni-Co-Mn, and Ni-Co-Al; The conductive agent in the positive electrode slurry is any one of carbon black, carbon nanotubes, and graphene, or any combination thereof. The binder for the positive electrode slurry is any one or any combination of polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-butadiene rubber. The active materials of the negative electrode slurry are graphite and Li4Ti5O. 12 Any one or any combination thereof of silicon and its oxides; The conductive agent in the negative electrode slurry is any one or any combination of carbon black, carbon nanotubes, and graphene. The binder for the negative electrode slurry is any one or any combination of sodium hydroxymethyl cellulose and styrene-butadiene rubber.

6. The 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery according to claim 5, characterized in that: The process also includes step S4, coating the ends of the positive and negative electrodes with conductive silver paste, connecting the tabs to the coated conductive silver paste, and curing at a temperature of 60℃~80℃ to form a battery cell.

7. The 3D printing method for a current collector-free, self-supporting three-dimensional lithium-ion battery according to claim 6, characterized in that: It also includes step S5, which involves using an aluminum-plastic film shell to soft-pack the battery cell and injecting sufficient electrolyte into the package.

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