An anode sheet based on ultraviolet light curing 3D printing, a preparation method and application thereof

Abstract

The present application relates to a kind of positive plate based on ultraviolet light curing 3D printing, preparation method and application, positive plate includes acrylate-based network structure and dispersed therein positive active material, conductive agent and binder, it is formed by direct writing type ultraviolet light curing 3D printing, and light initiator initiates acrylate monomer in situ polymerization to form acrylate-based network structure in printing process;Positive plate has mesh, serpentine or grid structure, is favorable to electrolyte infiltration and lithium ion transmission;Preparation method is to prepare the ink containing active material, conductive agent, binder, acrylate monomer, light initiator and solvent, by direct writing type 3D printing, layer-by-layer ultraviolet light curing and drying to obtain positive plate;The positive plate structure of the present application is adjustable, forming precision is high, and electrochemical performance is excellent, can be used in lithium ion battery, thick electrode battery and customizable battery electrode, is favorable to improve battery electrochemical performance, simplify manufacturing process and widen device structure design freedom degree.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a positive electrode sheet based on ultraviolet light curing 3D printing, its preparation method, and its application. Background Technology

[0002] With the development of wearable electronics, irregularly shaped electronic devices, and miniaturized electronic devices, energy storage devices no longer only need to meet basic power supply requirements, but also need to adapt to requirements such as lightweighting, miniaturization, structural designability, and simple manufacturing processes. Traditional lithium-ion batteries are widely used in portable electronic devices, electric vehicles, grid energy storage, aerospace, and medical devices. However, traditional electrodes are usually prepared using methods such as coating and rolling, which limits the shape and structural design of the electrodes, making it difficult to meet the fabrication requirements of complex-shaped electrodes, irregularly shaped batteries, and three-dimensional thick electrodes. Especially in the fields of wearable electronics and miniaturized electronic devices, energy storage devices often need to match the shape of the device itself, thus placing higher demands on the structural design and processing methods of the electrodes.

[0003] 3D printing is an additive manufacturing technology that forms specific structures by layer-by-layer material deposition. It features designable structures, a relatively simple fabrication process, high forming accuracy, and high material utilization. Compared to traditional electrode fabrication methods, 3D printing can construct electrode structures with specific geometric morphologies according to a pre-defined path, providing new ideas for the fabrication of complex electrode structures, thick electrodes, and customized battery devices. Among various 3D printing technologies, direct-write 3D printing is more suitable for multi-component functional material systems. This technology typically mixes active materials, conductive agents, and polymer components to form an ink with a certain degree of viscoelasticity, which is then extruded through a needle and deposited along a pre-defined path. Therefore, it is suitable for battery electrode inks composed of powdered active materials such as lithium iron phosphate and polymer systems.

[0004] For lithium-ion battery cathodes, lithium iron phosphate (LFP) exhibits good safety and cycle stability, making it a commonly used cathode active material. However, LFP itself is a powder material and cannot be formed alone in direct-write 3D printing; it needs to be combined with conductive agents and polymer components to form printable ink. The ink composition directly affects whether extrusion is successful during printing, whether the printed shape can be maintained, and whether the electrode maintains good structural integrity after drying. Therefore, in the fabrication of 3D-printed LFP cathode sheets, designing a suitable ink system is a crucial factor influencing the electrode structure and subsequent electrochemical performance.

[0005] On the other hand, while 3D printing technology can construct three-dimensional thick electrode structures, the increased electrode thickness also increases the diffusion path of lithium ions within the electrode, potentially affecting the electrochemical reaction rate and rate performance. Therefore, simply increasing the electrode thickness does not directly yield a better-performing electrode; a more continuous electron conduction network and ion transport channels need to be constructed within the electrode. Multi-walled carbon nanotubes can act as conductive agents in constructing the electron conduction network, while polymer components affect the connection state between active material particles, conductive agents, and binders within the electrode. For 3D-printed thick electrodes, a suitable polymer composition should not only aid in ink formation but also maintain the integrity of the printed electrode structure as much as possible and minimize performance loss caused by poor contact between solid components.

[0006] Polyacrylate materials possess characteristics such as photocurability, good adhesion, and tunable structure, making them suitable as polymer components in 3D printing electrode inks. Introducing photocurable acrylate monomers into lithium iron phosphate cathode inks and subjecting them to in-situ polymerization under ultraviolet light during printing allows for the formation of a polyacrylate-based network structure within the electrode. This network structure improves the formability of the printing ink and the structural integrity of the printed electrode, while also facilitating the formation of a more stable composite structure among lithium iron phosphate particles, multi-walled carbon nanotubes, and polyvinylidene fluoride. Previous experiments have demonstrated that introducing 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate into lithium iron phosphate 3D printing inks and preparing polymer-based 3D-printed lithium iron phosphate cathode sheets through layer-by-layer ultraviolet curing can be used to construct thick lithium iron phosphate electrodes with regular structures.

[0007] However, existing technologies still have the following shortcomings: First, the application of photocurable acrylate monomers in 3D printed electrodes remains relatively limited, and their impact on printability, electrode structural stability, and electrochemical performance still requires further research and optimization. Second, the composition of the cathode ink (such as the ratio of active materials, conductive agents, binders, monomers, and photoinitiators) lacks systematic optimization, resulting in problems such as unreasonable content ranges leading to printing difficulties or poor electrochemical performance. Third, the window for 3D printing process parameters (such as needle specifications, extrusion speed, number of printing layers, and illumination time) is narrow, lacking a wide range of process designs that can adapt to different electrode thicknesses and structural requirements.

[0008] Therefore, developing a UV-curable 3D-printed cathode sheet with scalable components, a reasonable content range, adjustable process parameters, and applicability to various cathode active materials, along with its preparation method, is of practical significance for improving the printability of 3D-printed cathode inks, enhancing the structural integrity of the printed electrode, and optimizing electron and ion transport in thick electrodes. This method has a relatively simple preparation process and strong structural design flexibility, providing a feasible solution for the fabrication of thick electrodes for lithium-ion batteries, customizable energy storage devices, and customized battery electrodes. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by providing a cathode sheet based on UV curing 3D printing, its preparation method, and its application. This addresses the difficulties that existing electrode preparation methods (especially traditional coating and rolling processes) face in achieving customized manufacturing of complex three-dimensional structures, irregular shapes, and thick electrodes. Furthermore, existing 3D printing cathode inks suffer from poor formability, structural instability, low electron / ion transport efficiency in thick electrodes, narrow components and process windows in the photocurable system, lack of systematic optimization of ink formulations, and limited compatibility with different cathode materials and solvent systems.

[0010] To achieve the above objectives, in a first aspect, the present invention provides a positive electrode sheet based on ultraviolet light curing 3D printing, the positive electrode sheet comprising: an acrylate-based network structure, and a positive electrode active material, a conductive agent, and a binder dispersed in the acrylate-based network structure.

[0011] The positive electrode is formed by direct-write UV curing 3D printing; the acrylate-based network structure is formed by in-situ polymerization of acrylate monomers initiated by a photoinitiator during the direct-write UV curing 3D printing process.

[0012] Preferably, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium manganese oxide.

[0013] The conductive agent includes one or more of the following: multi-walled carbon nanotubes, single-walled carbon nanotubes, acetylene black, Ketjen black, superconducting carbon black, carbon fiber, or graphene.

[0014] The adhesive includes one or more of the following: polyvinylidene fluoride, sodium carboxymethyl cellulose, polyacrylic acid, styrene-butadiene rubber, polyimide, polyvinylpyrrolidone, or polyethylene glycol.

[0015] Preferably, the photoinitiator comprises one or more of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoin dimethyl ether, 1-(4-dodecanephenyl)-2-hydroxy-2-methyl-1-propanone, or 2-hydroxy-2-methyl-1-[4-(tert-butyl)phenyl]-1-propanone.

[0016] The acrylate monomers include one or more of the following: 2-phenoxyethyl acrylate, ethoxyethoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, o-phenoxyethyl acrylate, isobornyl acrylate, cyclotrimethylolpropane methyl acetal acrylate, dicyclopentenyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, hydroxy-functional monoacrylate, aromatic monoacrylate, oxyethylated acrylate monomer, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, or propoxylated glycerol triacrylate.

[0017] Preferably, the positive electrode includes any one of a mesh structure, a serpentine structure, or a grid structure.

[0018] Preferably, the positive electrode further includes a current collector; the current collector includes any one of aluminum foil, aluminum alloy foil, or carbon-coated modified aluminum foil.

[0019] In a second aspect, the present invention provides a method for preparing a positive electrode sheet based on ultraviolet light curing 3D printing as described in the first aspect above, the method comprising:

[0020] The preparation of a positive electrode ink for UV curing 3D printing includes: using positive electrode active material, conductive agent, binder, and acrylate monomer as raw materials, mixing them evenly with a photoinitiator and a solvent to obtain the positive electrode ink.

[0021] The positive electrode ink is transferred into the injection tube of the 3D printing equipment, and ultraviolet light curing 3D printing is performed according to the preset path. During the 3D printing process, the printed layer is irradiated with ultraviolet light, so that the photoinitiator initiates the in-situ polymerization of the acrylate monomers to form an acrylate-based network structure, thereby obtaining a 3D printed electrode sheet.

[0022] The 3D-printed electrode sheet is dried to obtain a positive electrode sheet based on UV curing 3D printing.

[0023] Preferably, the raw materials include: 80 wt.% to 85 wt.% of positive electrode active material, 5 wt.% to 10 wt.% of conductive agent, 1 wt.% to 5 wt.% of binder, and 5 wt.% to 8 wt.% of acrylate monomers.

[0024] The solvent includes one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), or dimethyl sulfoxide (DMSO).

[0025] The mass ratio of the raw material to the solvent is 1:1 to 1.5:1.

[0026] The mass of the photoinitiator is 0.3% to 0.5% of the total mass of the positive electrode ink.

[0027] Preferably, the injection tube for the direct-write 3D printing uses a 20G to 30G needle with an inner diameter of 100μm to 600μm and an extrusion speed of 0.1mm. 3 / s~5mm 3 The printing speed is 1mm / s to 10mm / s, the number of printing layers is 2 to 5, each layer is exposed to ultraviolet light for 5 to 100 seconds, and then vacuum dried at 100℃ to 120℃ for 24 to 48 hours.

[0028] The positive electrode sheet is prepared by multi-layer direct-write 3D printing, with a thickness of 200μm to 380μm; the preset path includes any one of serpentine path, mesh path or grid path; the ultraviolet curing 3D printing controls the morphology, thickness and pore structure of the positive electrode sheet by adjusting the printing path and the number of printing layers.

[0029] Preferably, the positive electrode is a self-supporting positive electrode or a positive electrode loaded on the surface of the current collector.

[0030] Thirdly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode sheet based on ultraviolet light curing 3D printing as described in the first aspect.

[0031] The present invention provides a positive electrode sheet based on ultraviolet light curing 3D printing, its preparation method and application, which has the following technical effects.

[0032] (1) The method for preparing a positive electrode sheet based on UV curing 3D printing provided by the present invention involves mixing positive electrode active material, conductive agent, binder, acrylate monomers, photoinitiator and solvent in a certain proportion to obtain a positive electrode ink suitable for direct-write 3D printing; then transferring the obtained positive electrode ink into the injection tube of a 3D printing device, and using direct-write 3D printing technology, printing layer by layer according to a preset mesh, serpentine or grid path. During the printing process, after each layer is completed, it is immediately irradiated with ultraviolet light to induce the in-situ polymerization of acrylate monomers by the photoinitiator to form an acrylate-based network structure; finally, the printed electrode sheet is vacuum dried to remove residual solvent, resulting in a positive electrode sheet with a complete structure and a regular three-dimensional porous structure based on UV curing 3D printing. The positive electrode sheet can be self-supporting or directly printed on the surface of current collectors such as aluminum foil or carbon-coated aluminum foil.

[0033] The preparation method provided by this invention can flexibly construct positive electrode sheets with various regular three-dimensional structures such as mesh, serpentine, and grid according to a preset path. The electrode thickness can be precisely controlled by adjusting the number of printing layers, so as to realize the on-demand design of electrode morphology, pore structure and thickness, and meet the customized needs of different application scenarios such as irregularly shaped batteries, customizable electronic devices and high-load thick electrodes.

[0034] (2) The present invention introduces photocurable acrylate monomers into the positive electrode ink, and combines them with photoinitiators and layer-by-layer ultraviolet curing process to make the acrylate monomers polymerize in situ during the printing process to form a polyacrylate network structure. This network works synergistically with the binder to make the positive electrode ink have the characteristics of continuous extrusion and good shape retention, which significantly improves the printability of the positive electrode ink and greatly improves the structural integrity of the electrode after drying, effectively avoiding problems such as cracking and collapse.

[0035] (3) The positive electrode sheet based on UV curing 3D printing provided by the present invention, on the one hand, the conductive agent such as multi-walled carbon nanotubes constructs a continuous three-dimensional electron conduction network inside the electrode; on the other hand, the regular pore structure formed by 3D printing provides a smooth channel for electrolyte wetting and rapid migration of lithium ions; the two work together to achieve high active material loading and thick electrode, while helping to improve the electron and ion transport process in the thick electrode and reduce electrode polarization.

[0036] (4) The preparation method provided by this invention adopts a process combining direct-write 3D printing and layer-by-layer ultraviolet curing, which can realize electrode structure forming and in-situ polymerization of acrylate monomers during the printing process; at the same time, the 3D printing manufacturing method has high material utilization, reduces slurry waste, and can be adapted to multi-nozzle parallel printing, with good potential for large-scale production. The obtained positive electrode sheet can be directly used in various devices such as button cells, pouch cells, customizable lithium-ion batteries, energy storage batteries for wearable electronic devices, or high-load thick electrode batteries.

[0037] (5) Through the synergistic optimization of components and processes, the present invention enables the prepared positive electrode to have good structural integrity and electrochemical performance, and can maintain good rate performance and cycle stability under high active material loading and thick electrode structure. Attached Figure Description

[0038] Figure 1 This is a flowchart of the preparation method of positive electrode sheet based on ultraviolet light curing 3D printing provided in the embodiments of the present invention.

[0039] Figure 2 The preparation process of the polymer-based lithium iron phosphate cathode based on ultraviolet light curing 3D printing provided in Embodiment 1 of the present invention, wherein... Figure 2 (a) is a physical image of 3D printed positive electrode ink. Figure 2 (b) is a process diagram of direct writing 3D printing using positive electrode ink following a preset path. Figure 2 (c) is a process diagram of UV curing during the printing process. Figure 2 (d) is a physical image of the resulting mesh-like polymer-based lithium iron phosphate cathode after printing.

[0040] Figure 3 The image shows a cross-sectional scanning electron microscope (SEM) image of the polymer-based lithium iron phosphate cathode prepared in Example 1 of this invention. The thickness of the cathode is 380 μm.

[0041] Figure 4 The images show a comparison of the surface morphology of the pure-LFP cathode sheet (without photocurable acrylate monomers) in Comparative Example 1 and the uv-3DP-LFP-1-1 cathode sheet (with photocurable acrylate monomers) in Example 1, obtained using scanning electron microscopy.

[0042] Figure 5 The charge-discharge curves of the button cells assembled in Examples 1-5 and Comparative Example 1 of this invention are shown at 0.2C.

[0043] Figure 6 The diagram shows the rate performance of the button cells assembled in Examples 1-5 and Comparative Example 1 of this invention.

[0044] Figure 7 This is a long-cycle curve of the button cells assembled in Embodiments 1, 2, 3 and 5 of the present invention at 0.5C.

[0045] Figure 8 Thermogravimetric analysis diagram of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 provided in Example 6 of the present invention.

[0046] Figure 9Differential scanning calorimetry (DSC) curve of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 provided in Example 6 of this invention.

[0047] Figure 10 The infrared spectrum of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 provided in Example 6 of the present invention.

[0048] Figure 11 The photopolymer 3DP-PB-co-PA-1-1 provided in Example 6 of this invention has a hydrogen nuclear magnetic resonance spectrum. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0050] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0051] This invention provides a positive electrode sheet based on UV-curing 3D printing, comprising: an acrylate-based network structure, and a positive electrode active material, a conductive agent, and a binder dispersed in the acrylate-based network structure. The positive electrode sheet is formed by direct-write UV-curing 3D printing.

[0052] The acrylate-based network structure is formed by in-situ polymerization of acrylate monomers initiated by a photoinitiator during the direct-write UV curing 3D printing process.

[0053] The positive electrode active material includes one or more of the following: lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium manganese oxide.

[0054] Conductive agents include one or more of the following: multi-walled carbon nanotubes, single-walled carbon nanotubes, acetylene black, Ketjen black, superconducting carbon black, carbon fiber, or graphene.

[0055] The adhesive includes one or more of the following: polyvinylidene fluoride, sodium carboxymethyl cellulose, polyacrylic acid, styrene-butadiene rubber, polyimide, polyvinylpyrrolidone, or polyethylene glycol.

[0056] Photoinitiators include one or more of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoin dimethyl ether, 1-(4-dodecanephenyl)-2-hydroxy-2-methyl-1-propanone, or 2-hydroxy-2-methyl-1-[4-(tert-butyl)phenyl]-1-propanone; Acrylic monomers include one or more of the following: 2-phenoxyethyl acrylate, ethoxyethoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, o-phenoxyethyl acrylate, isobornyl acrylate, cyclotrimethylolpropane methyl acetal acrylate, dicyclopentenyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, hydroxyl-functional monoacrylate, aromatic monoacrylate, oxyethylated acrylate monomer, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, or propoxylated glycerol triacrylate. The hydroxyl-functional monoacrylates include one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxybutyl acrylate; the aromatic monoacrylates include one or more of 2-phenoxyethyl acrylate, benzyl methacrylate, ethoxylated nonylphenol acrylate, and ethoxylated phenol acrylate; and the oxyethylated acrylate monomers include one or more of ethoxyethoxyethyl acrylate, ethoxyethyl acrylate, methoxytriethylene glycol acrylate, ethoxylated bisphenol A diacrylate, and ethoxylated trimethylolpropane triacrylate.

[0057] The positive electrode includes any one of the following: mesh structure, serpentine structure or grid structure.

[0058] The positive electrode also includes a current collector; the current collector includes any one of aluminum foil, aluminum alloy foil or carbon-coated modified aluminum foil.

[0059] This invention provides a method for preparing the above-mentioned positive electrode sheet based on ultraviolet light curing 3D printing, such as... Figure 1 As shown, the specific steps include:

[0060] Step 110, preparing a positive electrode ink for UV curing 3D printing, includes: using positive electrode active material, conductive agent, binder, and acrylate monomer as raw materials, mixing them evenly with photoinitiator and solvent to obtain positive electrode ink.

[0061] The raw materials include: 80wt.% to 85wt.% of positive electrode active material, 5wt.% to 10wt.% of conductive agent, 1wt.% to 5wt.% of binder, and 5wt.% to 8wt.% of acrylate monomers.

[0062] The positive electrode active material includes one or more of the following: lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium manganese oxide.

[0063] Conductive agents include one or more of the following: multi-walled carbon nanotubes, single-walled carbon nanotubes, acetylene black, Ketjen black, superconducting carbon black, carbon fiber, or graphene.

[0064] The adhesive includes one or more of the following: polyvinylidene fluoride, sodium carboxymethyl cellulose, polyacrylic acid, styrene-butadiene rubber, polyimide, polyvinylpyrrolidone, or polyethylene glycol.

[0065] The photoinitiator includes one or more of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoin dimethyl ether, 1-(4-dodecanephenyl)-2-hydroxy-2-methyl-1-propanone, or 2-hydroxy-2-methyl-1-[4-(tert-butyl)phenyl]-1-propanone. The photoinitiator accounts for 0.3% to 0.5% of the total mass of the positive electrode ink, and can be any value within this range, such as 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0066] Acrylic monomers include one or more of the following: 2-phenoxyethyl acrylate, ethoxyethoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, o-phenoxyethyl acrylate, isobornyl acrylate, cyclotrimethylolpropane methyl acetal acrylate, dicyclopentenyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, hydroxyl-functional monoacrylate, aromatic monoacrylate, oxyethylated acrylate monomer, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, or propoxylated glycerol triacrylate.

[0067] The preferred acrylate monomers are 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate. Both 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate contain acrylate groups that can participate in the UV curing reaction, enabling them to polymerize under the action of a photoinitiator and form a polyacrylate network structure between the positive electrode active material, conductive agent, and binder. When these two monomers are used together, the characteristics of the phenoxy structure in 2-phenoxyethyl acrylate and the ether oxygen segment in ethoxyethoxyethyl acrylate are combined, which is beneficial for balancing ink formability, print structure retention, and overall electrode integrity.

[0068] The structural formula of 2-phenoxyethyl acrylate is: .

[0069] The structural formula of ethoxyethyl acrylate is: .

[0070] Solvents include one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), or dimethyl sulfoxide (DMSO).

[0071] The mass ratio of raw materials to solvent is 1:1 to 1.5:1.

[0072] Step 120: Transfer the positive electrode ink into the injection tube of the 3D printing equipment, and perform ultraviolet curing 3D printing according to the preset path. During the 3D printing process, the printed layer is irradiated with ultraviolet light to cause the photoinitiator to initiate the in-situ polymerization of acrylate monomers to form an acrylate-based network structure, thereby obtaining the 3D printed electrode sheet.

[0073] The direct-write 3D printing injection tube uses a 20G–30G needle with an inner diameter of 100μm–600μm and an extrusion speed of 0.1mm. 3 / s~5mm 3 The printing speed is 1 mm / s to 10 mm / s, the number of printing layers is 2 to 5, and each layer is exposed to ultraviolet light for 5 to 100 seconds. Preferably, the injection tube for direct-write 3D printing uses a 25G needle with an inner diameter of 250 μm, and the extrusion speed is 1 mm / s. 3 The printing speed is 4 mm / s, the number of printing layers is 4, and each layer is exposed to ultraviolet light for 15 seconds.

[0074] Step 130: Dry the 3D-printed electrode to obtain a positive electrode based on UV curing 3D printing.

[0075] The drying process involves placing the 3D-printed electrode in a vacuum dryer and drying it at 100℃~120℃ for 24 to 48 hours; preferably, the vacuum drying temperature is 120℃ and the vacuum drying time is 24 hours.

[0076] The positive electrode is prepared by multilayer direct-write 3D printing with a thickness of 200μm to 380μm. It can be any value within this range, such as 200μm, 220μm, 240μm, 260μm, 280μm, 300μm, 320μm, 340μm, 360μm, 380μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0077] The preset path includes any one of the following: serpentine path, mesh path, or grid path; UV curing 3D printing controls the morphology, thickness, and pore structure of the positive electrode by adjusting the printing path and the number of printing layers.

[0078] The positive electrode is a self-supporting positive electrode; in an optional scheme, it can also be loaded onto the surface of the current collector and directly written 3D printed to obtain a positive electrode including the current collector.

[0079] The present invention provides a lithium-ion battery, which includes a positive electrode based on ultraviolet light curing 3D printing, according to a first aspect.

[0080] The positive electrode sheet prepared by the above preparation method provided in the embodiments of the present invention can be used as a positive electrode sheet in secondary batteries, and in particular, it can be assembled with a negative electrode sheet, a separator, and an electrolyte to form a lithium-ion battery.

[0081] The lithium-ion batteries provided in the embodiments of the present invention can be applied to electric vehicles, hybrid vehicles, electric bicycles, energy storage power stations, portable electronic devices, mobile power supplies, drones, power tools, wearable devices, medical electronic devices, aerospace vehicles, marine power systems, or grid frequency regulation energy storage systems.

[0082] To better understand the technical solution provided by this invention, the following examples illustrate the preparation process and characteristics of the positive electrode sheet based on ultraviolet curing 3D printing.

[0083] Example 1 This embodiment provides a process for preparing a positive electrode based on ultraviolet light curing 3D printing, and the specific process is as follows.

[0084] (1) Preparation of positive electrode ink for UV curing 3D printing: Specifically, lithium iron phosphate, multi-walled carbon nanotubes, polyvinylidene fluoride, 2-phenoxyethyl acrylate and ethoxyethyl acrylate are used as raw materials, and mixed with photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone and solvent NMP in a high-speed ball mill. The mixture is ball-milled at 800 rpm for 30 min until it is homogeneous, and a uniform viscous positive electrode ink is obtained, which is denoted as uv-3DP-LFP-1-1.

[0085] The raw materials contain 80 wt.% lithium iron phosphate, 10 wt.% multi-walled carbon nanotubes, 5 wt.% polyvinylidene fluoride, 2.5 wt.% 2-phenoxyethyl acrylate, 2.5 wt.% ethoxyethyl acrylate, and 0.3% photoinitiator by mass. The mass ratio of 2-phenoxyethyl acrylate to ethoxyethyl acrylate is 1:1. The outer diameter of the multi-walled carbon nanotubes is 8 nm to 15 nm. The mass ratio of the solid component to NMP in the cathode ink is approximately 1.25:1.

[0086] (2) Transfer the positive electrode ink into the injection tube of the 3D printing equipment and assemble a 25G needle with an inner diameter of 250μm. Set the extrusion speed to 1 mm during the printing process. 3 The printing speed is 4 mm / s, and the electrodes are printed according to a preset serpentine or mesh path, for a total of four layers. After each layer is printed, the electrode is irradiated with a UV lamp for 15 seconds to allow 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate to undergo UV-curing in-situ polymerization under the action of a photoinitiator. Through layer-by-layer printing and layer-by-layer photocuring, the positive electrode ink gradually forms a structure with regularly arranged lines during the deposition process, resulting in a 3D printed electrode sheet.

[0087] (3) The 3D printed electrode was placed in a vacuum drying oven at 120°C for 24 hours to remove residual solvent and further stabilize the electrode structure, thus obtaining a polymer-based lithium iron phosphate cathode based on UV curing 3D printing, denoted as uv-3DP-LFP-1-1 cathode.

[0088] The specific preparation process of the positive electrode sheet provided in Example 1 is as follows: Figure 2 As shown, where Figure 2 (a) is a physical image of 3D printed positive electrode ink. Figure 2 (b) is a process diagram of direct writing 3D printing using positive electrode ink following a preset path. Figure 2 (c) is a process diagram of UV curing during the printing process. Figure 2 (d) is a physical image of the resulting mesh-like polymer-based lithium iron phosphate cathode after printing.

[0089] A cross-sectional SEM image of the uv-3DP-LFP-1-1 positive electrode prepared in Example 1 of this invention is shown below. Figure 3 As shown in the figure, the thickness of the positive electrode is 380 μm.

[0090] The surface SEM image of the uv-3DP-LFP-1-1 positive electrode prepared in Example 1 of this invention is shown below. Figure 4 As shown in (d).

[0091] The positive electrode sheet prepared in this embodiment was used to assemble a coin cell and then tested.

[0092] The assembly process of the coin cell is as follows: In an argon glove box (water and oxygen content <0.1ppm), the 3D-printed lithium iron phosphate positive electrode is used as the working electrode, the lithium metal sheet is used as the counter electrode, the separator is Celgard 2500, and the electrolyte is a solution of ethylene carbonate / dimethyl carbonate / propylene carbonate (EC:DMC:PC volume ratio of 1:1:1) containing 1mol / L lithium hexafluorophosphate. The electrolyte addition amount is 80μL, and the coin cell is assembled.

[0093] After battery assembly, the resulting coin cell half-cells underwent constant current charge-discharge testing: the testing equipment was a Blue Electric tester, and the electrochemical test voltage range was 2.5V to 4.0V. The rate test program was set as follows: 5 cycles at 0.1C, followed by 5 cycles each at 0.2C, 0.5C, and 1C, and finally 5 cycles at 0.1C. Long-cycle testing was conducted at 0.5C. The discharge specific capacity at 0.2C and the capacity retention rate at 0.1 / 0.5C are detailed in Table 2.

[0094] The charge-discharge curve of the coin cell assembled with the uv-3DP-LFP-1-1 positive electrode sheet provided in this embodiment at 0.2C is shown in the figure. Figure 5 As shown.

[0095] The rate performance diagram of the coin cell assembled with the uv-3DP-LFP-1-1 positive electrode sheet provided in this embodiment is as follows: Figure 6 As shown.

[0096] The cycling curve of the coin cell assembled with the uv-3DP-LFP-1-1 positive electrode sheet provided in this embodiment at 0.5C is shown in the figure. Figure 7 As shown.

[0097] Example 2 This embodiment provides a process for preparing a positive electrode sheet based on UV curing 3D printing. The difference from Example 1 is that the mass ratio of 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate in the positive electrode ink is 1:2. The positive electrode ink in Example 2 is designated as uv-3DP-LFP-1-2, and the prepared positive electrode sheet is designated as uv-3DP-LFP-1-2 positive electrode sheet. The preparation process for other positive electrode sheets is the same as in Example 1.

[0098] The positive electrode sheet prepared in this embodiment was used to assemble a coin cell and tested. The assembly process and testing methods were the same as in Example 1. The discharge specific capacity at 0.2C and the capacity retention rate at 0.1 / 0.5C are detailed in Table 2.

[0099] The charge-discharge curve of the coin cell assembled with the uv-3DP-LFP-1-2 positive electrode sheet provided in this embodiment at 0.2C is shown in the figure. Figure 5 As shown.

[0100] The rate performance diagram of the coin cell assembled with the uv-3DP-LFP-1-2 positive electrode sheet provided in this embodiment is as follows: Figure 6 As shown.

[0101] The cycling curve of the coin cell assembled with the uv-3DP-LFP-1-2 positive electrode provided in this embodiment at 0.5C is shown in the figure. Figure 7 As shown.

[0102] Example 3 This embodiment provides a process for preparing a positive electrode sheet based on UV curing 3D printing. The difference from Example 1 is that the mass ratio of 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate in the positive electrode ink is 2:1. The positive electrode ink in Example 3 is designated as uv-3DP-LFP-2-1, and the prepared positive electrode sheet is designated as uv-3DP-LFP-2-1 positive electrode sheet. The preparation process for other positive electrode sheets is the same as in Example 1.

[0103] The positive electrode sheet prepared in this embodiment was used to assemble a coin cell and tested. The assembly process and testing methods were the same as in Example 1. The discharge specific capacity at 0.2C and the capacity retention rate at 0.1 / 0.5C are detailed in Table 2.

[0104] The charge-discharge curve of the coin cell assembled with the uv-3DP-LFP-2-1 positive electrode provided in this embodiment at 0.2C is shown in the figure. Figure 5 As shown.

[0105] The rate performance diagram of the coin cell assembled with the uv-3DP-LFP-2-1 positive electrode sheet provided in this embodiment is as follows: Figure 6 As shown.

[0106] The cycling curve of the coin cell assembled with the uv-3DP-LFP-2-1 positive electrode provided in this embodiment at 0.5C is shown in the figure. Figure 7 As shown.

[0107] Example 4 This embodiment provides a process for preparing a positive electrode sheet based on UV-curing 3D printing. The difference from Example 1 is that the mass ratio of 2-phenoxyethyl acrylate to ethoxyethoxyethyl acrylate in the positive electrode ink is 1:4. The positive electrode ink in Example 4 is designated as uv-3DP-LFP-1-4, and the prepared positive electrode sheet is designated as uv-3DP-LFP-1-4 positive electrode sheet. The preparation process for other positive electrode sheets is the same as in Example 1.

[0108] The positive electrode sheet prepared in this embodiment was used to assemble a coin cell and tested. The assembly process and testing methods were the same as in Example 1. The discharge specific capacity at 0.2C and the capacity retention rate at 0.1 / 0.5C are detailed in Table 2.

[0109] The charge-discharge curve of the coin cell assembled with the uv-3DP-LFP-1-4 positive electrode provided in this embodiment at 0.2C is shown below. Figure 5 As shown.

[0110] The rate performance diagram of the coin cell assembled with the uv-3DP-LFP-1-4 positive electrode sheet provided in this embodiment is as follows: Figure 6 As shown.

[0111] Example 5 This embodiment provides a process for preparing a positive electrode sheet based on UV curing 3D printing. The difference from Example 1 is that the mass ratio of 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate in the positive electrode ink is 4:1. The positive electrode ink in Example 5 is designated as uv-3DP-LFP-4-1, and the prepared positive electrode sheet is designated as uv-3DP-LFP-4-1 positive electrode sheet. The preparation process for other positive electrode sheets is the same as in Example 1.

[0112] The positive electrode sheet prepared in this embodiment was used to assemble a coin cell and tested. The assembly process and testing methods were the same as in Example 1. The discharge specific capacity at 0.2C and the capacity retention rate at 0.1 / 0.5C are detailed in Table 2.

[0113] The charge-discharge curve of the coin cell assembled with the uv-3DP-LFP-4-1 positive electrode provided in this embodiment at 0.2C is shown below. Figure 5 As shown.

[0114] The rate performance diagram of the coin cell assembled with the uv-3DP-LFP-4-1 positive electrode sheet provided in this embodiment is as follows: Figure 6 As shown.

[0115] The cycling curve of the coin cell assembled with the uv-3DP-LFP-4-1 positive electrode provided in this embodiment at 0.5C is shown in the figure. Figure 7 As shown.

[0116] Figure 7 Cyclic test results at 0.5C are presented for coin cells assembled with the positive electrode sheets obtained in Examples 1, 2, 3, and 5, to illustrate the capacity changes of the corresponding cells during the test. The cell assembled with the uv-3DP-LFP-1-1 positive electrode sheet obtained in Example 1 has a discharge specific capacity of approximately 140.9 mAh / g in the first cycle and approximately 77 mAh / g after 100 cycles, corresponding to a capacity retention of approximately 54.6%.

[0117] Example 6 This embodiment characterizes the acrylate-based network structure separately.

[0118] Using the same 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate as in Example 1, they were mixed at a mass ratio of 1:1. The photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone was added and the mixture was further mixed until homogeneous. Under ultraviolet light irradiation, the same photocuring method as in Example 1 was used to photocur and polymerize 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate to form an acrylate-based network structure, resulting in a photocurable polyacrylate polymer, denoted as 3DP-PB-co-PA-1-1.

[0119] The obtained 3DP-PB-co-PA-1-1 was characterized by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and proton nuclear magnetic resonance spectroscopy.

[0120] Thermogravimetric analysis (TGA) curve of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 prepared in this embodiment is shown below. Figure 8 As shown, thermogravimetric analysis results indicate that the polymer undergoes significant decomposition at approximately 400℃, suggesting that the obtained 3DP-PB-co-PA-1-1 possesses a certain degree of thermal stability.

[0121] The differential scanning calorimetry (DSC) curve of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 prepared in this embodiment is shown below. Figure 9 As shown, the differential scanning calorimetry results indicate that the glass transition temperature of the polymer is approximately -28.22℃, suggesting that the obtained polymer has a certain chain segment mobility near room temperature.

[0122] The infrared spectrum of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 prepared in the embodiments of the present invention is as follows: Figure 10 As shown. The infrared spectrum was used to analyze the characteristic functional groups in 3DP-PB-co-PA-1-1. Figure 10 The test results show that C=O, COC and benzene ring related characteristic peaks can be observed in 3DP-PB-co-PA-1-1, indicating that the acrylate monomers form a polymer containing ester groups, ether bonds and aromatic structures after photocuring.

[0123] The 1H NMR spectrum of the photocurable polyacrylate polymer 3DP-PB-co-PA-1-1 prepared in the embodiments of the present invention is shown below. Figure 11 As shown. The proton nuclear magnetic resonance (NMR) spectrum was used to further analyze the signals of different hydrogen environments in the polymer structure, thereby helping to explain the polymer structure formed after photocuring of the two acrylate monomers. The horizontal axis represents the chemical shift (ppm). Through... Figure 11 As can be seen in the spectrum, characteristic hydrogen signals related to the target polymer structure appear: peak h at 7.0-7.5 ppm represents ortho- and para-hydrogens of the benzene ring; a weak peak i at 6.0-6.5 ppm represents meta-hydrogens of the benzene ring; multiple peaks f, g, and e in the 4.0-4.6 ppm range correspond to oxymethylene hydrogens linked to two types of ester groups; strong peak d and overlapping peaks b / c at 3.3-3.8 ppm belong to methylene hydrogens of the triethylene glycol ether segment; and peaks a, j, and k in the 1.0-1.8 ppm region correspond to terminal methyl groups, methylene groups in the polymer backbone, and methine hydrogens in the backbone, respectively. These characteristic signals are basically consistent with the polymer structure shown. Combined with the infrared spectroscopy results, it can be concluded that the two acrylate monomers, after UV curing, formed the polyacrylate polymer 3DP-PB-co-PA-1-1.

[0124] This embodiment illustrates that 2-phenoxyethyl acrylate and ethoxyethoxyethyl acrylate can undergo a polymerization reaction under ultraviolet light irradiation to form a polyacrylate-based polymer. Introducing this type of photocurable acrylate system into lithium iron phosphate 3D printing ink allows for the in-situ formation of a polymer network during the printing process, thereby affecting the structural integrity and electrochemical performance of the electrode.

[0125] To better illustrate the effects of the embodiments of the present invention, the following comparative examples are compared with the embodiments described above.

[0126] Comparative Example 1 This comparative example provides a common 3D printed positive electrode preparation process. The difference from Example 1 is that no photocurable acrylate monomers are introduced and no ultraviolet curing process is used. The specific preparation process is as follows.

[0127] (1) Weigh 2.4g of lithium iron phosphate, 0.3g of multi-walled carbon nanotubes and 0.3g of polyvinylidene fluoride, and add N-methylpyrrolidone to adjust the viscosity of the slurry. Mix evenly by high-speed ball milling to obtain a positive electrode ink without the addition of photocurable acrylate monomers, denoted as pure-LFP.

[0128] The raw materials contain 80 wt.% lithium iron phosphate, 10 wt.% multi-walled carbon nanotubes, and 10 wt.% polyvinylidene fluoride, with the outer diameter of the multi-walled carbon nanotubes ranging from 8 nm to 15 nm. In the cathode ink, the mass ratio of the solid component to NMP is approximately 1.25:1.

[0129] (2) Transfer the positive electrode ink into the injection tube of the 3D printing equipment and assemble a 25G needle with a diameter of 250μm. Set the extrusion speed to 1mm during the printing process. 3 The printing speed is 4mm / s. The electrode is printed according to the preset serpentine or mesh path. A total of four layers are printed. By printing layer by layer, the positive electrode ink gradually forms a structure with regularly arranged lines during the deposition process, resulting in a 3D printed electrode sheet.

[0130] (3) The 3D printed electrode is placed in a vacuum drying oven at 120°C and dried for 24 hours to remove residual solvent, and the 3D printed lithium iron phosphate positive electrode is obtained, which is called pure-LFP positive electrode.

[0131] The surface SEM image of the pure-LFP cathode prepared in Comparative Example 1 of this invention is shown below. Figure 4 As shown in (c). By Figure 4 (c) and Figure 4 The SEM images in (d) show that the particles on the surface of the pure-LFP cathode in Comparative Example 1 are loosely aggregated with a large number of large pores, and the particle distribution is more dispersed. In contrast, the particles on the surface of the uv-3DP-LFP-1-1 cathode in Example 1 are more densely aggregated, forming more regular clusters, with a more uniform pore structure and a significant reduction in large pores. These results indicate that the surface microstructure of the 3D-printed cathode is altered after introducing photocurable acrylate monomers and employing a UV curing process.

[0132] The pure-LFP cathode sheet prepared in this comparative example was used to assemble a coin cell and tested. The assembly process and testing methods were the same as in Example 1. The discharge specific capacity at 0.2C and the capacity retention rate at 0.1 / 0.5C are detailed in Table 2.

[0133] The charge-discharge curves of the coin cell assembled with the pure-LFP cathode provided in this comparative example are shown in the figure below at 0.2C. Figure 5As shown, the vertical axis represents voltage (V), and the horizontal axis represents specific capacity (mAh / g).

[0134] pass Figure 5 Comparing the charge-discharge curves of different acrylate monomer ratios (Examples 1-5) with the comparative example (pure-LFP) without the introduction of photocurable monomers at a rate of 0.2C, it can be seen that each example exhibits the flat charge-discharge platform characteristic of lithium iron phosphate cathode materials, and the voltage platform is stable at about 3.38V (when the specific capacity is 150 mAh / g). However, the discharge voltage of comparative example 1 (pure-LFP) has dropped significantly and is close to the cutoff voltage of 2.5V at the same specific capacity. This indicates that the electrode without the introduction of photocurable monomers exhibits severe polarization at 0.2C, and the rate performance is significantly degraded. Further comparison of the plateau spacing between the various embodiments reveals that uv-3DP-LFP-1-1 (PEA:EEEA=1:1) has the smallest charge-discharge plateau spacing, indicating the lowest degree of electrode polarization and the least resistance to lithium-ion transport within the electrode. This is attributed to the synergistic effect of the monomers in the 1:1 ratio. The rigid benzene ring structure of PEA provides sufficient mechanical support to maintain the integrity of the electrode structure, while the flexible ethoxy segments of EEEA construct a continuous lithium-ion transport channel. Together, they achieve an optimal balance between ion conduction and structural stability. In contrast, the plateau spacing of other ratios (such as 1:2, 2:1, 1:4, 4:1) is slightly larger, indicating that an imbalance in the monomer ratio weakens this synergistic effect, leading to an increase in electrode polarization. Overall, the above results clearly demonstrate that the photocurable acrylate monomers introduced in this invention significantly improve the electrochemical polarization behavior of the 3D printed cathode, and the electrode (Example 1) exhibits the best rate performance when PEA and EEEA are compounded in a 1:1 mass ratio. The rate performance diagram of the coin cell assembled with the pure-LFP cathode provided in this comparative example is as follows: Figure 6 As shown, the horizontal axis represents the number of cycles, and the vertical axis represents the specific capacity (mAh / g). The rate test program can evaluate the capacity change and rate recovery capability of different 3D printed lithium iron phosphate cathode sheets under different current densities.

[0135] pass Figure 6It can be seen that the batteries assembled from the positive electrode sheets prepared in Examples 1-5 generally exhibit higher discharge specific capacities at all rates than the pure-LFP of Comparative Example 1, indicating that the 3D-printed lithium iron phosphate positive electrode sheets show better rate performance after introducing photocurable acrylate monomers into the positive electrode ink. As the rate gradually increases from 0.1C to 0.2C, 0.5C, and 1C, the discharge specific capacity of each sample decreases, but samples with different monomer compositions and ratios show significant differences at high rates. Specifically, the uv-3DP-LFP-1-1 corresponding to Example 1 has a discharge specific capacity of approximately 110 mAh / g at 1C, which is also significantly higher than that of Comparative Example 1. In contrast, the discharge specific capacity of pure-LFP at 1C is only about 20-30 mAh / g, indicating that the positive electrode sheet without the introduction of photocurable acrylate monomers shows more significant capacity decay at high rates. When the rate was restored to 0.1C, the discharge specific capacity of all samples recovered to approximately 160 mAh / g, close to the capacity at the initial 0.1C stage, indicating that they still have good capacity recovery capability after high-rate charge and discharge. These results demonstrate that the introduction of photocurable acrylate monomers is beneficial to improving the rate performance of 3D-printed lithium iron phosphate cathode sheets, with different monomer compositions and ratios having a significant impact on capacity output at 1C.

[0136] Table 1 summarizes the component contents of the positive electrode inks prepared in Examples 1-5 and Comparative Example 1.

[0137] Table 1 Table 2 summarizes the electrochemical performance test data of Examples 1-5 and Comparative Example 1.

[0138] Table 2 As can be seen from the test data in Table 2, the pure-LFP cathode sheet in Comparative Example 1, without the introduction of photocurable acrylate monomers, has a discharge specific capacity of 119.8 mAh / g at 0.2C and a capacity retention rate of 77.7% at 0.5C relative to 0.1C. In contrast, all examples (Examples 1-5) incorporating photocurable acrylate monomers exhibit higher discharge specific capacities and higher capacity retention rates at 0.5C relative to 0.1C than Comparative Example 1. Specifically, Examples 1-5 have discharge specific capacities of 137.0–149.9 mAh / g at 0.2C and capacity retention rates of 84.6%–91.1% at 0.5C relative to 0.1C; Example 1 achieves a discharge specific capacity of 149.9 mAh / g and a capacity retention rate of 91.1%, respectively. The above results indicate that after introducing photocurable acrylate monomers, the resulting 3D-printed lithium iron phosphate cathode can maintain a high capacity output under 0.2C and 0.5C conditions. Different monomer compositions and ratios will affect the discharge specific capacity and rate performance of the cathode.

[0139] In summary, this invention provides a method for preparing a positive electrode sheet based on UV-curing 3D printing. By combining direct-write 3D printing with layer-by-layer UV curing, acrylate monomers are polymerized in situ during the printing process to form a polyacrylate network, thereby assisting the layer-by-layer formation of the positive electrode ink and maintaining the printed structure. By adjusting the printing path, the number of printing layers, and the composition and ratio of acrylate monomers, 3D-printed positive electrodes with different structures and thicknesses can be prepared. Electrochemical test results show that the positive electrode sheet prepared by this method can maintain the typical charge-discharge characteristics of lithium iron phosphate materials and exhibits certain capacity output and rate recovery capabilities at different rates. Specifically, Example 1 shows a discharge specific capacity of 149.9 mAh / g at 0.2C, and a capacity retention rate of 91.1% at 0.5C compared to 0.1C.

[0140] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A positive electrode sheet based on ultraviolet light-cured 3D printing, characterized by, The positive electrode sheet comprises: an acrylate-based network structure, and a positive electrode active material, a conductive agent, and a binder dispersed in the acrylate-based network structure; The positive electrode is formed by direct-write UV curing 3D printing; the acrylate-based network structure is formed by in-situ polymerization of acrylate monomers initiated by a photoinitiator during the direct-write UV curing 3D printing process.

2. The positive electrode sheet based on ultraviolet light curing 3D printing according to claim 1, characterized by, The positive electrode active material includes one or more of the following: lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium manganese oxide. The conductive agent includes one or more of the following: multi-walled carbon nanotubes, single-walled carbon nanotubes, acetylene black, Ketjen black, superconducting carbon black, carbon fiber, or graphene. The adhesive includes one or more of the following: polyvinylidene fluoride, sodium carboxymethyl cellulose, polyacrylic acid, styrene-butadiene rubber, polyimide, polyvinylpyrrolidone, or polyethylene glycol.

3. The positive electrode sheet based on ultraviolet light curing 3D printing according to claim 1, characterized in that, The photoinitiator includes one or more of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoin dimethyl ether, 1-(4-dodecanephenyl)-2-hydroxy-2-methyl-1-propanone, or 2-hydroxy-2-methyl-1-[4-(tert-butyl)phenyl]-1-propanone; The acrylate monomers include one or more of the following: 2-phenoxyethyl acrylate, ethoxyethoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, o-phenoxyethyl acrylate, isobornyl acrylate, cyclotrimethylolpropane methyl acetal acrylate, dicyclopentenyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, hydroxy-functional monoacrylate, aromatic monoacrylate, oxyethylated acrylate monomer, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, or propoxylated glycerol triacrylate.

4. The positive electrode sheet based on ultraviolet light curing 3D printing according to claim 1, characterized in that, The positive electrode includes any one of the following: a mesh structure, a serpentine structure, or a grid structure.

5. The positive electrode sheet based on ultraviolet light curing 3D printing according to claim 1, characterized in that, The positive electrode also includes a current collector; the current collector includes any one of aluminum foil, aluminum alloy foil, or carbon-coated modified aluminum foil.

6. A method for preparing a positive electrode sheet based on ultraviolet light curing 3D printing as described in any one of claims 1-5, characterized in that, The preparation method includes: The preparation of a positive electrode ink for UV curing 3D printing includes: using positive electrode active material, conductive agent, binder, and acrylate monomer as raw materials, mixing them evenly with a photoinitiator and a solvent to obtain the positive electrode ink; The positive electrode ink is transferred into the injection tube of the 3D printing equipment, and ultraviolet light curing 3D printing is performed according to the preset path. During the 3D printing process, the printed layer is irradiated with ultraviolet light, so that the photoinitiator initiates the in-situ polymerization of the acrylate monomers to form an acrylate-based network structure, thereby obtaining a 3D printed electrode sheet. The 3D-printed electrode sheet is dried to obtain a positive electrode sheet based on UV curing 3D printing.

7. The preparation method according to claim 6, characterized in that, The raw materials include: 80 wt.% to 85 wt.% of positive electrode active material, 5 wt.% to 10 wt.% of conductive agent, 1 wt.% to 5 wt.% of binder, and 5 wt.% to 8 wt.% of acrylate monomers; The solvent includes one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), or dimethyl sulfoxide (DMSO); The mass ratio of the raw material to the solvent is 1:1 to 1.5:1; The mass of the photoinitiator is 0.3% to 0.5% of the total mass of the positive electrode ink.

8. The preparation method according to claim 6, characterized in that, The direct-write 3D printing injection tube uses a 20G–30G needle with an inner diameter of 100μm–600μm and an extrusion speed of 0.1mm. 3 / s~5mm 3 / s, printing travel speed is 1mm / s~10mm / s, printing layers are 2 to 5 layers, each layer is exposed to ultraviolet light for 5 seconds to 100 seconds, and then vacuum dried at 100℃~120℃ for 24 hours to 48 hours; The positive electrode sheet is prepared by multi-layer direct-write 3D printing, with a thickness of 200μm to 380μm; the preset path includes any one of serpentine path, mesh path or grid path; the ultraviolet curing 3D printing controls the morphology, thickness and pore structure of the positive electrode sheet by adjusting the printing path and the number of printing layers.

9. The preparation method according to claim 6, characterized in that, The positive electrode is a self-supporting positive electrode or a positive electrode loaded on the surface of the current collector.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet based on ultraviolet light curing 3D printing as described in any one of claims 1-5.

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