Electrode with patterned conductive coating

Abstract

The present disclosure provides an electrode with a patterned conductive coating. An electrode includes: a current collector; a conductive dot pattern, each conductive dot comprising an aggregate of conductive particles and a binder, the conductive dots being imprinted on the current collector; and a self-supporting solvent-free electrode film comprising conductive particles, a fibrillated polymer binder, and an active material, the self-supporting solvent-free electrode film being laminated onto the conductive dots and the current collector.

Description

Technical Field

[0001] The present disclosure relates to an electrode structure for a lithium-ion battery. Background Art

[0002] In the context of energy storage technologies, the fabrication of solvent-free dry electrodes for anodes and cathodes is an area of ongoing research. Summary of the Invention

[0003] An electrode having a current collector has a pattern of conductive dots imprinted thereon. The conductive dots comprise agglomerates of conductive particles and a binder. Additionally, a self-supporting solvent-free electrode film comprising conductive particles, a fibrillated polymer binder, and an active material is laminated onto the conductive dots and the current collector, thereby forming a cohesive self-supporting electrode. In this electrode, the binder used in the conductive dots includes polyvinylidene fluoride. The binder in the electrode can be selected from the group including polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or carboxymethyl cellulose. The conductive particles used in the electrode can be carbon-based. Specifically, these carbon-based conductive particles can be carbon black or carbon nanotubes. The diameter of the conductive dots in the electrode can be designed to be less than 100 microns. More preferably, the diameter of these conductive dots can be less than 10 microns. The height of the conductive dots in the electrode can be less than 10 microns. Additionally, the height of these conductive dots can be less than 5 microns. The current collector component of the electrode can be made of a metal foil. In particular, this metal foil used as the current collector can be made of copper. Alternatively, the current collector can be made of aluminum foil. The fibrillated polymer binder used in the electrode can be polytetrafluoroethylene.

[0004] A method for forming an electrode involves laminating a solvent-free self-supporting electrode film comprising conductive particles, a fibrillated polymer binder, and an active material onto a current collector. The current collector is patterned with imprinted conductive dots, each imprinted conductive dot consisting of an agglomerate of conductive particles and a binder, thereby forming a self-supporting electrode. The method can also include dot-printing the imprinted conductive dots onto the current collector. In this method, polytetrafluoroethylene can be used as the fibrillated polymer binder.

[0005] An electrode with a solvent-free self-supporting structure is formed from a solvent-free self-supporting electrode membrane. The membrane contains conductive particles, fibrillated polymer binders, and active materials, and is laminated onto conductive points. These points each contain aggregates of a mixture of conductive particles and fluorinated and non-fluorinated binders, and are imprinted onto the current collector. The fluorinated binders used in the electrode can be selected from the group including: polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, perfluoroalkoxy polymer, ethylene-tetrafluoroethylene, fluorinated propylene-methylenecopolymer, and perfluoropolyether. The non-fluorinated binders in the electrode can be selected from options such as polyethylene, carboxymethyl cellulose, polymethyl methacrylate, and polyurethane. The conductive points in the electrode can have a diameter of less than 10 microns and a height of less than 5 microns. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A is an exploded view of an electrode according to one embodiment;

[0007] Figure 1B is a side view of an electrode according to one embodiment;

[0008] Figure 2 is a schematic diagram of a conductive point according to one embodiment;

[0009] Figure 3 is a schematic diagram of a self-supporting solvent-free electrode membrane according to one embodiment; and

[0010] Figure 4 is a flowchart of an assembly process according to one embodiment. DETAILED DESCRIPTION

[0011] Embodiments are described herein. However, it should be understood that the disclosed embodiments are merely examples and other embodiments may take different and alternative forms. The drawings are not necessarily to scale. Some features may be enlarged or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching one of ordinary skill in the art.

[0012] The various features shown and described in any one of the reference drawings can be combined with features shown in one or more other drawings to produce embodiments not explicitly shown or described. Combinations of the shown features provide representative embodiments for typical applications. However, for a particular application or implementation, various combinations and modifications of the features may be desirable that are consistent with the teachings of this disclosure.

[0013] The fabrication of solvent-free dry electrodes typically involves mixing a polytetrafluoroethylene (PTFE) binder with a conductive agent such as carbon black or carbon nanotubes (CNTs) and an active electrode material. The mixture is then hot-pressed to form a cohesive self-supporting electrode film, which is laminated onto a current collector. This method has gained attention for its potential to reduce the reliance on solvents in electrode production.

[0014] A challenge encountered in using PTFE binders in this process is their low surface energy, which can lead to suboptimal adhesion to the current collector. Insufficient adhesion can cause the layers of the electrode to separate from the current collector, a condition that can increase the internal resistance within the battery cell and potentially lead to a gradual decrease in capacity. Maintaining a stable and durable bond between the electrode film and the current collector can also preserve the performance and lifespan of the batteries produced by this method.

[0015] This disclosure relates to methods for electrode construction in energy storage devices, with an emphasis on imprinting techniques for increasing the adhesion at the interface between an electrode active layer and a current collector foil such as copper (Cu) or aluminum (Al). The imprinted pattern consists of conductive dots, each formed from a mixture of conductive particles and a specific binder, thereby enhancing the adhesion of the active layer to the current collector. Patterned imprinting (also known as dot printing) is used to modify the surface area of the current collector, thus maintaining consistent adhesion to the electrode active layer.

[0016] The electrode composition is determined by blending conductive materials such as carbon black and carbon nanotubes (CNTs) with various binders. These conductive materials are specifically selected for their electrical conductivity properties. The binders range from fluorinated binders such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) to non-fluorinated binders including polyethylene (PE) and carboxymethyl cellulose (CMC). The selection of a particular binder or combination thereof depends on the desired properties of the final electrode, such as mechanical stability and conductivity. Each binder is chosen based on its properties, such as polyvinylidene fluoride, which provides a balance between mechanical strength and chemical stability.

[0017] For coatings utilizing PTFE, PVDF is considered a compatible imprinting coating binder. PVDF is preferred compared to other binders due to its adhesion characteristics. This preference is based on the similarity in the chemical structure of PVDF and PTFE and its ability to adhere to the current collector substrate. Compared to PTFE, PVDF tends to form a more stable bond with the current collector material, which can affect the lifespan and performance of the electrode.

[0018] The structure of the electrode is further defined by the physical properties of the conductive points patterned onto the current collector. These points are designed to have a diameter of less than 100 microns, and preferably less than 10 microns, while their height is constrained to be less than 10 microns, ideally less than 5 microns. These points (each containing an agglomeration of conductive particles and a binder) are imprinted onto the surface of the current collector to increase the adhesion of the active layer of the electrode. The conductive particles within these points are typically carbon-based, thus providing favorable electrical properties. The size of the conductive points is selected to be 100 microns or less in diameter, and more preferably, less than 10 microns. Similarly, the height is constrained to a maximum of 10 microns, with an optimal height of 5 microns or less. This precision of the point structure may contribute to maintaining uniformity on the electrode surface.

[0019] The lamination process involves covering the patterned current collector with a solvent-free self-supporting electrode film. This film, which contains conductive particles, a fibrillated polymer binder (such as polytetrafluoroethylene), and an active material, helps to form the self-supporting structure of the electrode. The film contains a mixture of conductive particles, a fibrillated polymer binder, and an active material (which together form the self-supporting electrode). The choice of binder in the film is complementary to the binder used in the conductive points to maintain the integrity of the electrode structure. Binder options include fluorinated types (which may have a structural similarity to PTFE) and non-fluorinated types, each selected based on their unique properties to fulfill a specific role within the electrode.

[0020] Reference is now made to Figure 1A , which is an exploded view of an electrode 10 according to one or more embodiments. The electrode 10 has a current collector 12 made of a metal foil (such as copper foil or aluminum foil), and the current collector is patterned with conductive points 14. These points are made of an agglomeration of conductive particles bound together with a binder and are directly imprinted onto the surface of the current collector 12. A self-supporting solvent-free electrode film 16 is laminated with the conductive points 14 and the current collector 12 and serves as the main structure and conductive layer of the electrode 10. Figure 1B is a side view of the electrode 10, with the self-supporting solvent-free electrode film 16 laminated with the conductive points 14 and the current collector 12.

[0021] The binder within the conductive points 14 can be a fluorinated or non-fluorinated binder selected from the group including but not limited to polyvinylidene fluoride. These binders can provide a balance between mechanical strength and chemical stability. The conductive particles embedded within the points can be selected for their conductivity and can include materials such as carbon black or carbon nanotubes. The size of the conductive points 14 is controlled, with the diameter controlled to be less than 100 microns, and more specifically, less than 10 microns. The height is controlled to be less than 10 microns, and more preferably less than 5 microns.

[0022] The choice of material for the current collector 12 can vary and cover metals such as copper or aluminum, which are typically used in foil form to support the overlying electrode structure. Within the electrode film 16 is a fibrillated polymer binder, which can include materials for increasing the durability of the electrode 10, such as polytetrafluoroethylene.

[0023] Figure 2 is a schematic diagram of the conductive point 14. The conductive point 14 contains an agglomerate of conductive particles 18 mixed with a binder 20. The binder 20 can be solely a fluorinated binder or a non-fluorinated binder, or can be a mixture of one or more fluorinated binders or non-fluorinated binders. The choice of binder is based on the desired properties of the conductive point 14, such as adhesion to the current collector and compatibility with the conductive particles 18. Fluorinated binders may include options such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, perfluoroalkoxy polymer, ethylene-tetrafluoroethylene, fluorinated propylene-methylidene copolymer, and perfluoropolyether, while non-fluorinated binders may involve materials such as polyethylene, carboxymethyl cellulose, polymethyl methacrylate, and polyurethane. The conductive particles 16, which may include carbon black or carbon nanotubes, are selected based on their conductivity ability.

[0024] Figure 3 is a schematic diagram of the self-supporting solvent-free electrode film 16. The film 16 contains conductive particles 18, a fibrillated polymer binder 22, and an active material 24. It is designed to be laminated onto the conductive point 14 and the current collector 12, thereby forming part of the electrode structure 10. The conductive particles 18 in the film can include carbon-based materials such as carbon black or carbon nanotubes, which are used due to their conductivity properties.

[0025] The fibrillated polymer binder 22 in the film 16 can be a material such as polytetrafluoroethylene. The binder 22 is integrated with the conductive particles 18 and the active material 24 to form the electrode film 16. The lamination process involves applying the film onto the patterned conductive point 14 and the current collector 12, which can be made of a material such as a copper or aluminum film. The overall assembly of the electrode 10 involves aligning and fixing the imprinted current collector 12 with the electrode film 16 that contributes to the electrode structure.

[0026] Figure 4 is an illustration of a flowchart of an assembly process according to an embodiment. In block one 26, a solvent-free self-supporting electrode film containing conductive particles, a fibrillated polymer binder, and an active material is laminated onto a patterned current collector having imprinted conductive points. Each point has an agglomerate of conductive particles and a binder. After this lamination, a solvent-free self-supporting electrode is formed. The conductive points can be imprinted onto the current collector by dot printing. The fibrillated polymer binder can be polytetrafluoroethylene.

[0027] The algorithms, methods, or processes disclosed or proposed herein can be conveyed to or implemented by a computer, controller, or processing device, which can include any dedicated electronic control unit or programmable electronic control unit. Similarly, the algorithms, methods, or processes can be stored in various forms as data and instructions executable by a computer or controller, including but not limited to information permanently stored on a non-writable storage medium such as a read-only memory device and information changeably stored on a writable storage medium such as an optical disc, a random access memory device, or other magnetic and optical media. The algorithms, methods, or processes can also be implemented as software-executable objects. Alternatively, suitable hardware components, such as application-specific integrated circuits, field-programmable gate arrays, state machines, or other hardware components or devices, or firmware, a combination of hardware and software components, can be used to implement the algorithms, methods, or processes in whole or in part.

[0028] Although the exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are descriptive words rather than restrictive words, and it should be understood that various changes can be made without departing from the spirit and scope of the disclosed materials.

[0029] As previously described, the features of the various embodiments can be combined to form additional embodiments that may not be explicitly described or shown in the present disclosure. Although the various embodiments may have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art should recognize that one or more features or characteristics can be compromised to achieve the desired overall system attributes, depending on the specific application and implementation. These attributes can include, but are not limited to: strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. Thus, embodiments that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are within the scope of the present disclosure and may be desirable for a particular application.

[0030] According to the present invention, an electrode is provided, the electrode having: a current collector; a conductive dot pattern, each conductive dot comprising an agglomerate of conductive particles and a binder, the conductive dots being imprinted on the current collector; and a self-supporting solvent-free electrode film comprising conductive particles, a fibrillated polymer binder, and an active material, the self-supporting solvent-free electrode film being laminated to the conductive dots and the current collector to form a self-supporting electrode.

[0031] According to one embodiment, the binder comprises polyvinylidene fluoride.

[0032] According to one embodiment, the binder is selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or carboxymethyl cellulose.

[0033] According to one embodiment, the conductive particles are carbon-based.

[0034] According to one embodiment, the conductive particles are carbon black or carbon nanotubes.

[0035] According to one embodiment, the diameter of the conductive dots is less than 100 μm.

[0036] According to one embodiment, the diameter of the conductive dots is less than 10 μm.

[0037] According to one embodiment, the height of the conductive dots is less than 10 μm.

[0038] According to one embodiment, the height of the conductive dots is less than 5 μm.

[0039] According to one embodiment, the current collector is a metal foil.

[0040] According to one embodiment, the current collector is a copper foil.

[0041] According to one embodiment, the current collector is an aluminum foil.

[0042] According to one embodiment, the fibrillated polymer binder is polytetrafluoroethylene.

[0043] According to the present invention, a method includes: laminating a solvent-free self-supporting electrode film comprising conductive particles, a fibrillated polymer binder, and an active material onto a patterned current collector having an imprinted pattern of conductive dots, each imprinted conductive dot comprising an agglomerate of conductive particles and a binder, to form a self-supporting electrode.

[0044] In one aspect of the present invention, the method includes dot-printing the imprinted conductive dots onto the current collector.

[0045] In one aspect of the present invention, the fibrillated polymer binder is polytetrafluoroethylene.

[0046] According to the present invention, there is provided a battery component having: a solvent-free self-supporting electrode having a self-supporting solvent-free electrode film comprising conductive particles, a fibrillated polymer binder, and an active material, the self-supporting solvent-free electrode film being laminated onto conductive dots, each conductive dot having an agglomerate of conductive particles, a fluorinated binder, and a non-fluorinated binder, the conductive dots being imprinted on a current collector.

[0047] According to one embodiment, the fluorinated binder is selected from the group consisting of: polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, perfluoroalkoxy polymer, ethylene-tetrafluoroethylene, fluorinated propylene-methylenecopolymer, and perfluoropolyether.

[0048] According to one embodiment, the non-fluorinated binder is selected from the group consisting of polyethylene, carboxymethyl cellulose, polymethyl methacrylate, and polyurethane.

[0049] According to one embodiment, the diameter of the conductive point is less than 10 μm, and the height of the conductive point is less than 5 μm.

Claims

1. An electrode, comprising: Current collector; a conductive dot pattern, each conductive dot comprising an agglomerate of conductive particles and a binder, the conductive dot being stamped on the current collector; as well as A self-supporting solvent-free electrode film comprises conductive particles, a fibrillated polymer binder and an active material, wherein the self-supporting solvent-free electrode film is laminated onto the conductive dots and the current collector to form a self-supporting electrode.

2. The electrode of claim 1, wherein the binder comprises polyvinylidene fluoride.

3. The electrode of claim 1, wherein the binder is selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or carboxymethyl cellulose.

4. The electrode of claim 1, wherein the conductive particles are carbon based.

5. The electrode of claim 4, wherein the conductive particles are carbon black or carbon nanotubes. The electrode of claim 1 , wherein the conductive dots have a diameter less than 100 μm.

7. The electrode of claim 6, wherein the diameter of the conductive dots is less than 10 μm.

8. The electrode according to claim 1, wherein the height of the conductive dots is less than 10 μm.

9. The electrode of claim 8, wherein the height of the conductive dots is less than 5 μm.

10. The electrode of claim 1, wherein the current collector is a metal foil.

11. The electrode of claim 10, wherein the current collector is a copper foil.

12. The electrode of claim 11, wherein the current collector is aluminum foil.

13. The electrode of claim 1, wherein the fibrillated polymer binder is polytetrafluoroethylene.

14. A method comprising: A solvent-free self-supporting electrode film comprising conductive particles, a fibrillated polymer binder and an active material is laminated onto a patterned current collector having embossed conductive dots, each of which comprises an agglomerate of conductive particles and a binder, to form a self-supporting electrode.

15. The method of claim 14, further comprising dotting the embossed conductive dots onto the current collector.

Images