DOUBLE LAYER ANODE

Abstract

An electrode assembly for lithium-ion batteries is presented. The electrode assembly comprises a metal foil current collector with an adherent laminated active material layer and an aligned active material layer on top. The laminated layer maintains adhesion to the current collector during electrochemical cycling of the electrode assembly, while the aligned layer provides lithium-ion diffusion pathways.

Description

AREA OF TECHNOLOGY

[0001] The disclosure concerns anode materials for lithium-ion batteries. GENERAL STATE OF THE ART

[0002] One challenge in the development and optimization of lithium-ion batteries is to achieve fast charging capability without compromising the thickness of the electrode material loading.

[0003] Graphite undergoes physical changes during the charging and discharging cycles of a lithium-ion (Li-ion) battery. During the charging process, known as lithiation, graphite expands as it absorbs Li-ions. Conversely, during the discharging process, known as delthiation, graphite contracts as it releases Li-ions. SUMMARY

[0004] In one aspect of the disclosure, an electrode assembly is presented. The electrode assembly comprises a metal foil current collector with a laminated active material layer adhered to the metal foil current collector and an aligned active material layer deposited on top of the laminated active material layer, configured to provide diffusion pathways for lithium ions during electrochemical cycling of the electrode. The metal foil current collector can be made of copper, aluminum, nickel, or titanium. The laminated active material layer can further contain a binder. The binder can be carboxymethylcellulose, styrene-butadiene rubber, or polyvinylidene fluoride. The laminated active material layer can further contain a solvent. The solvent can be N-methyl-2-pyrrolidone, an aqueous solvent, an organic solvent, or other suitable solvents.In some configurations, the electrode assembly may also include a protective layer on the aligned active material layer.

[0005] In another aspect of the disclosure, a method for forming an electrode is presented. The method involves coating an active material slurry onto a metal foil current collector, laminating the active material slurry with the metal foil current collector, forming a laminated layer on the metal foil current collector, and applying a magnetic field to active material particles deposited on a surface of the laminated layer such that the active material particles align and project away from the laminated layer, resulting in a laminated-aligned double-layer electrode. The method may further include drying the active material slurry on the foil current collector after coating. A magnetic field from a neodymium magnet may be used to align the active material particles. In some configurations, the magnetic field used to align the active material particles may be an electromagnet.The metal foil current collector can be made of copper, aluminum, nickel, or titanium. The active material slurry can also contain a binder. The binder can be carboxymethylcellulose, styrene-butadiene rubber, or polyvinylidene fluoride. In other configurations, the active material slurry can also contain a solvent. The solvent can be N-methyl-2-pyrrolidone, a water-based solvent, or an organic solvent. In yet another configuration, the process can involve applying a protective layer to the top of the laminated, aligned bilayer electrode.

[0006] In yet another aspect of the disclosure, a lithium-ion battery is presented. The lithium-ion battery includes a positive electrode, a separator positioned adjacent to the positive electrode, and a negative electrode connected to the separator. A metal foil current collector is also included, with an active material layer laminated onto the metal foil current collector and an aligned active material layer deposited on top of the active material layer to define direct diffusion pathways for lithium ions during electrochemical cycling of the lithium-ion battery. The active material layer and the aligned active material layer can be graphite-based. The aligned active material layer can be aligned using a magnetic field source. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of lithium ion diffusion pathways in an anode with laminated graphite; Fig. Figure 2 is a schematic diagram of lithium ion diffusion pathways in an anode with aligned graphite; Fig. Figure 3 is a schematic diagram of laminated graphite in a delithiated state; Fig. Figure 4 is a schematic diagram of laminated graphite in a lithiated state; Fig. Figure 5 is a schematic diagram of aligned graphite in a delithiated state; Fig. Figure 6 is a schematic diagram of aligned graphite in a lithiated state; Fig. Figure 7 is a schematic diagram of an electrode according to one or more aspects of the disclosure; Fig. Figure 8 is a flowchart of a process for forming an electrode according to one or more aspects of the disclosure; and Fig. Figure 9 is a schematic diagram of a battery according to one or more aspects of the revelation. DETAILED DESCRIPTION

[0007] This document describes embodiments. However, it is understood that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale. Some features may be enlarged or reduced to show details of specific components. Therefore, specific design and functional details disclosed in this document are not to be interpreted as limiting, but merely as a representative basis for teaching the person skilled in the art.

[0008] Various features illustrated and described with respect to any one of the figures can be combined with features illustrated in one or more other figures to create embodiments not expressly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of the features, consistent with the teachings of this disclosure, may be desirable for specific applications or implementations.

[0009] To address the cycling stability of aligned active material electrodes, a laminated-aligned double-layer active material electrode is presented. This configuration delineates an electrode material coating in two layers: a lower laminated active material layer, which can be attached to a current collector, and an upper layer, which can be an aligned active material layer. The active material can be any suitable active material, such as graphite.

[0010] The electrode is manufactured by first coating the laminated active material layer onto the current collector. Depending on the specific design requirements of the lithium-ion battery, the current collector can be composed of various metal foils, such as copper, aluminum, or nickel. The configurability of metal foils allows for individual customization based on factors such as electrical conductivity, mechanical strength, and chemical stability. After coating and drying the laminated active material layer, the aligned active material layer is then applied on top of the laminated active material layer.

[0011] The alignment of the active material platelets in the aligned active material layer can be achieved using a magnet, such as a neodymium magnet placed beneath the current collector. The diamagnetism of active material particles, such as graphite, along the hexagonal axis of their lattice relative to the ground plane causes the ground plane to orient parallel to the magnetic field. This alignment ensures that the active material platelets remain vertically aligned relative to the current collector. The top aligned layer is then dried using heat or vacuum drying techniques, preserving the vertical alignment of the active material platelets established by the magnetic field. The alignment of the active material particles in this layer enables efficient lithium-ion diffusion pathways, thereby enhancing fast-charging capabilities.

[0012] Additionally, various solvents and binder systems can be used in the manufacturing process to optimize the coating and alignment of the active material platelets. Solvents such as N-methyl-2-pyrrolidone, water-based systems, and other organic solvents can be used depending on the desired electrode properties. These solvents facilitate the uniform distribution and proper adhesion of the active material particles to the current collector. Binder systems can include, among others, polyvinylidene fluoride, carboxymethylcellulose, or styrene-butadiene rubber. These binder systems also contribute to the structural integrity of the electrode during the lithiation and delthiation cycles.

[0013] For potential manufacturing applications, the magnetic field required for alignment can be provided by electromagnets that can be adapted to the needs of lithium-ion battery production processes. This approach not only maintains the fast-charging capability of the aligned active material layer but also addresses problems of horizontal strain that can lead to delamination and mechanical separation in single-layer electrodes. The adaptability of the proposed manufacturing process allows for scaling up production while maintaining the precision required for effective graphite alignment.

[0014] Fig. Figures 1-2 are schematic diagrams of lithium-ion diffusion pathways in electrodes. Fig. Figure 1 shows a laminated graphite anode. The active material layer of the anode is a laminated active material layer with horizontally oriented graphite particles on a current collector, which can be a metal foil current collector. The horizontal orientation of the laminated particles results in a longer, less direct Li-ion diffusion path. Fig. Figure 2 shows an aligned graphite anode. The active material layer of the anode is a vertically aligned graphite platelet layer on a current collector, which can also be a metal foil current collector. The vertical alignment of the graphite platelets creates a shorter, more direct Li-ion diffusion path. The direct diffusion paths due to the vertically aligned graphite platelet layer in the aligned graphite anode contrast with the indirect diffusion paths of the horizontally aligned graphite particles in the laminated layer.

[0015] Fig. Figures 3-4 show a laminated graphite anode in a delithiated or lithiated state. Fig. Figure 3 is a schematic diagram of a laminated graphite anode in a delithiated state. The laminated graphite particles remain horizontally aligned on the metal foil current collector. This alignment limits the efficiency of lithium-ion diffusion, as ions must follow a convoluted path through the horizontally aligned particles.

[0016] Fig. Figure 4 is a schematic diagram of a laminated graphite anode in a lithiated state. The laminated graphite particles still exhibit a horizontal orientation, but the expansion and contraction of graphite during lithiation and delithiation are evident. This vertical expansion and contraction generates stress within the electrode, which can lead to mechanical instability over repeated charge and discharge cycles.

[0017] Fig. Figures 5-6 show an aligned graphite anode in a delithiated or lithiated state. Fig. Figure 5 is a schematic diagram of an aligned graphite anode in a delithiated state. The vertically aligned graphite platelets are shown on the metal foil current collector. This vertical alignment allows for a more direct Li-ion diffusion path, thereby improving the efficiency of ion transport within the electrode.

[0018] Fig. Figure 6 is a schematic diagram of an aligned graphite anode in a lithiated state. The vertically aligned graphite platelets expand and contract horizontally during lithiation and delthiation, respectively. This horizontal strain, caused by the expansion and contraction of the graphite, can lead to potential displacement of graphite from the current collector surface, resulting in flaking and cracking. The proposed double-layer configuration mitigates this problem by using a laminated active material layer attached to the metal foil current collector to absorb horizontal strain while maintaining the integrity of the aligned graphite layer above and preserving its fast-charging capabilities.

[0019] Fig. Figure 7 is a schematic diagram of an electrode assembly 10 according to one or more aspects of the disclosure. The electrode assembly comprises a metal foil current collector 12, a laminated active material layer 14 adhering to the metal foil current collector 12, and an aligned active material layer 16 deposited on top of the laminated active material layer 14. A protective layer 18 is present on top of the aligned active material layer 16. The metal foil current collector 12 can be made of copper, aluminum, nickel, or titanium, depending on the specific application and design requirements of the electrode assembly 10. The metal foil current collector 12 provides a stable and conductive substrate for the laminated active material layer 14 and the aligned active material layer 16, maintaining efficient Li-ion electron transport during electrochemical cycling of the electrode assembly 10.

[0020] The laminated active material layer 14 is adhered to the metal foil pantograph 12. This laminated active material layer 14 contains active material particles, such as graphite, dispersed in a binder matrix. The binder can be carboxymethylcellulose, styrene-butadiene rubber, polyvinylidene fluoride, or other suitable binders that provide mechanical integrity and adhesion to the metal foil pantograph 12. The laminated active material layer 14 can also contain a solvent to facilitate the distribution and coating process. Suitable solvents include N-methyl-2-pyrrolidone, water-based solvents, organic solvents, or other appropriate solvents.

[0021] The aligned active material layer 16 can be deposited on top of the laminated active material layer 14. This aligned active material layer 16 contains active material particles that are aligned in a vertical orientation to enhance Li-ion diffusion pathways during electrochemical cycling. The vertical alignment creates direct diffusion pathways for Li-ions. The direct diffusion pathways in the aligned active material layer 16 enable more efficient lithium-ion transport, thereby improving the performance of the electrode assembly 10, especially during fast charge and discharge cycles. The alignment of the graphite particles can be achieved using various types of magnets. Neodymium magnets, known for their strong magnetic fields, can be used to effectively orient the graphite particles.Alternatively, electromagnets can be used that allow adjustable magnetic field strengths and the ability to switch the field on and off as needed during manufacturing. These magnets facilitate the alignment of the active material particles for increased performance of the electrode assembly 10. A protective layer 18 can be deposited on top of the aligned active material layer 16. This protective layer 18 can be composed of materials that prevent deterioration of the aligned active material layer 16 and provide additional mechanical stability to the electrode assembly 10.

[0022] Fig. Figure 8 is a flowchart of a process 20 according to one or more aspects of the disclosure. Process 20 begins with step 22, which involves coating an active material slurry onto a metal foil pantograph. The metal foil pantograph may be composed of materials such as copper, aluminum, nickel, or titanium. The active material slurry may contain a binder, which may be one of carboxymethylcellulose, styrene-butadiene rubber, polyvinylidene fluoride, or another suitable binder. Additionally, the slurry may contain a solvent, such as N-methyl-2-pyrrolidone, a water-based solvent, an organic solvent, or another suitable solvent. After coating, the active material slurry is dried on the metal foil pantograph.

[0023] Next, in step 24, the active material slurry is laminated onto the metal foil current collector, forming a laminated layer. This laminated layer provides a base for the subsequent deposition of the aligned active material layer. In step 26, a magnetic field is applied to the active material particles deposited on the surface of the laminated layer using a magnetic field source. The magnetic field source can be a neodymium magnet or an electromagnet. The magnetic field aligns the active material particles so that they protrude away from the laminated layer, resulting in a laminated-aligned double-layer electrode. This alignment increases the Li-ion diffusion pathways and subsequently the electrode's performance during electrochemical cycling, particularly for fast-charge and discharge applications.Optionally, the method 20 can further include the application of a protective layer on top of the laminated-aligned double-layer electrode to prevent deterioration and to provide additional mechanical stability to the electrode assembly.

[0024] Fig.Figure 9 is a schematic diagram of a Li-ion battery 28 according to one or more aspects of the disclosure. The Li-ion battery 28 has a positive electrode 30, a separator 32 positioned adjacent to the positive electrode 30, and a negative electrode 34 abutting the separator 32. The negative electrode 34 includes the metal foil current collector 12 with the active material layer 14 laminated thereon to maintain adhesion of the laminated active material layer 14 to the metal foil current collector 12 during electrochemical cycling. Additionally, the aligned active material layer 16 is deposited on top of the laminated active material layer 14.

[0025] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the terms used in the description are descriptive and not limiting, and it is understood that various modifications can be made without deviating from the essence and scope of the invention. Moreover, the features of different implementing embodiments can be combined to form further embodiments of the invention.

[0026] Although the present disclosure is described with regard to certain embodiments and specific examples, it is understood that the invention is not limited to these embodiments and examples. A person skilled in the art can make various modifications, changes, and adaptations without deviating from the scope and essence of the present invention. For example, the specific types of active materials, solvents, binders, and current collectors described in this document can be varied based on the desired performance characteristics and application requirements.

[0027] The methods and systems described in this document are applicable to a wide variety of industrial applications, including, but not limited to, the manufacture of lithium-ion batteries, capacitors, and other electrochemical energy storage devices. The invention can be particularly advantageous for applications requiring high cycle stability, fast charging capabilities, and electrode performance.

[0028] According to the present invention, an electrode assembly is provided comprising: a metal foil current collector; a laminated active material layer adhering to the metal foil current collector; and an aligned active material layer deposited on top of the laminated active material layer, configured to provide diffusion pathways for lithium ions during electrochemical cycling of the electrode.

[0029] According to one embodiment, the metal foil current collector is made of copper, aluminum, nickel or titanium.

[0030] According to one embodiment, the laminated active material layer also contains a binder.

[0031] According to one embodiment, the binder is carboxymethylcellulose, styrene-butadiene rubber or polyvinylidene fluoride.

[0032] According to one embodiment, the laminated active material layer also contains a solvent.

[0033] According to one embodiment, the solvent is N-methyl-2-pyrrolidone, a water-based solvent, or an organic solvent.

[0034] According to one embodiment, the invention is further characterized by a protective layer on the aligned active material layer.

[0035] According to the present invention, a method for forming an electrode comprises the following: coating an active material slurry onto a metal foil current collector, laminating the active material slurry with the metal foil current collector, forming a laminated layer on the metal foil current collector, and applying a magnetic field to active material particles on a surface of the laminated layer such that the active material particles align and protrude away from the laminated layer, resulting in a laminated-aligned double-layer electrode.

[0036] In one aspect of the invention, the method involves drying the active material slurry after coating.

[0037] In one aspect of the invention, the magnetic field is generated by a neodymium magnet.

[0038] In one aspect of the invention, the magnetic field is generated by an electromagnet.

[0039] In one aspect of the invention, the metal foil current collector is made of copper, aluminum, nickel or titanium.

[0040] In one aspect of the invention, the active material slurry further contains a binder.

[0041] In one aspect of the invention, the binder is carboxymethylcellulose, styrene-butadiene rubber or polyvinylidene fluoride.

[0042] In one aspect of the invention, the active material slurry further contains a solvent.

[0043] In one aspect of the invention, the solvent is N-methyl-2-pyrrolidone, a water-based solvent or an organic solvent.

[0044] In one aspect of the invention, the method involves applying a protective layer to the laminated-aligned double-layer electrode.

[0045] According to the present invention, a lithium-ion battery is provided comprising: a positive electrode; a separator positioned adjacent to the positive electrode; and a negative electrode in contact with the separator and comprising a metal foil current collector, wherein an active material layer is laminated onto the metal foil current collector and an aligned active material layer is deposited on the active material layer to define direct diffusion pathways for lithium ions during electrochemical cycling of the lithium-ion battery.

[0046] According to one embodiment, the active material layer and the aligned active material layer are graphite-based.

[0047] According to one embodiment, the aligned active material layer is aligned using a magnetic field source.

Claims

[1] Electrode assembly comprising: a metal foil pantograph; a laminated active material layer adhering to the metal foil current collector; and An aligned active material layer deposited on top of the laminated active material layer, configured to provide diffusion pathways for lithium ions during electrochemical cycling of the electrode. [2] Electrode assembly according to claim 1, wherein the metal foil current collector is made of copper, aluminium, nickel or titanium. [3] Electrode assembly according to claim 1, wherein the laminated active material layer further comprises a binder. [4] Electrode assembly according to claim 3, wherein the binder is one of carboxymethylcellulose, styrene-butadiene rubber, polyvinylidene fluoride or other suitable binders. [5] Electrode assembly according to claim 1, wherein the laminated active material layer further contains a solvent. [6] Electrode assembly according to claim 5, wherein the solvent is N-methyl-2-pyrrolidone, a water-based solvent, an organic solvent or other suitable solvents. [7] Electrode assembly according to claim 1, further comprising a protective layer on top of the aligned active material layer. [8] Method for forming an electrode, comprising: Coating an active material slurry onto a metal foil current collector; Laminating the active material slurry with the metal foil current collector, forming a laminated layer on the metal foil current collector; and Applying a magnetic field to active material particles deposited on a surface of the laminated layer such that the active material particles align themselves and protrude away from the laminated layer, resulting in a laminated-aligned double-layer electrode. [9] Method according to claim 8, further comprising drying the active material slurry on the foil current collector after coating. [10] Method according to claim 8, wherein the magnetic field used to align the active material particles is a neodymium magnet. [11] Method according to claim 8, wherein the magnetic field used to align the active material particles is an electromagnet. [12] Method according to claim 8, wherein the metal foil current collector is made of copper, aluminium, nickel or titanium. [13] Method according to claim 8, wherein the active material slurry further contains a binder. [14] Method according to claim 8, wherein the active material slurry further contains a solvent. [15] Lithium-ion battery, comprising: a positive electrode; a separator positioned adjacent to the positive electrode; and a negative electrode that rests against the separator, wherein an active material layer is laminated onto the metal foil current collector to maintain adhesion of the active material layer to the metal foil current collector during electrochemical cycling, and an aligned active material layer with diffusion pathways for lithium ions is deposited on top of the active material layer during electrochemical cycling of the lithium-ion battery.

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