Dry electrode for lithium ion battery

Abstract

The present disclosure provides a dry electrode for a lithium ion battery. An electrode assembly for a lithium ion battery is provided. The electrode assembly may include a metal foil having thereon a conductive coating including a polymeric binder and a self-supporting electrode film having an active material and a fibrillated composite binder, the self-supporting electrode film being laminated with the metal foil such that the conductive coating is interposed between the metal foil and the self-supporting electrode film. The fibrillated composite binder may include carbon particles and the same polymeric binder.

Description

Technical Field

[0001] The present disclosure relates to dry electrodes for lithium-ion batteries and methods of making the same. Background Art

[0002] Lithium-ion batteries are rechargeable batteries in which lithium ions move from the negative electrode to the positive electrode during discharge, and move in the opposite direction when charged. Batteries typically include a separator between the electrodes to physically separate the electrodes.

[0003] Electrodes are typically constructed by applying active materials to current collectors in the presence of a binder that promotes cohesion between the active materials and adhesion to the current collector. Typical manufacturing processes include wet coating or slurry casting methods, in which a solvent or aqueous solution is used to dissolve the binder and mix with the active material to form a slurry. The slurry is then applied to the current collector. The current collector is then dried with the coating to remove the solvent from the electrode. Electrodes formed without the use of solvents can allow for easier mass production, but may affect the dispersion of the conductive agent. Summary of the invention

[0004] According to one embodiment, an electrode assembly is provided, comprising a metal foil having a conductive coating including a polymer binder, and a self-supporting electrode film of an active material and a fibrillated composite binder, the self-supporting electrode film being laminated with the metal foil such that the conductive coating is interposed between the metal foil and the self-supporting electrode film. The fibrillated composite binder comprises carbon particles and the same polymer binder.

[0005] In an alternative embodiment, a battery is provided, the battery comprising a separator and a pair of electrodes sandwiching the separator therebetween. At least one of the electrodes comprises a laminated layer of a metal foil having thereon a conductive coating comprising a polymer binder and a self-supporting electrode film of an active material and a fibrillated composite binder comprising carbon particles and the same polymer binder.

[0006] In yet another embodiment, a method for dry manufacturing a battery electrode is provided, the method comprising: hot pressing a dry electrode mixture of an active material and a fibrillated composite binder to form a self-supporting electrode film, the fibrillated composite binder having carbon particles and a polymer binder; and coating a current collector with a conductive coating to form a coated current collector, the conductive coating comprising carbon particles and the same polymer binder. The self-supporting electrode film is then laminated to the coated current collector to form a battery electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a cross-sectional view of a dry electrode according to one embodiment.

[0008] Figure 2is a cross-sectional view of a battery device including an exemplary dry electrode.

[0009] Figure 3 is a diagram of a method for manufacturing an electrode by a dry process according to one embodiment. DETAILED DESCRIPTION

[0010] Embodiments are described herein. However, it should be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The drawings are not necessarily drawn to scale. Some features may be enlarged or minimized to show details of particular components. Therefore, the specific structural details and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art.

[0011] The various features shown and described with reference to any one of the accompanying drawings may be combined with features shown in one or more other drawings to produce embodiments not explicitly shown or described. The combinations of features shown provide representative embodiments for typical applications. However, for specific applications or implementations, various combinations and modifications of features consistent with the teachings of the present disclosure may be desired.

[0012] One of the steps in battery manufacturing typically involves coating an active material on a metal foil to form an electrode. The electrode active material facilitates the movement of ions during the charge and discharge of the battery. The positive or cathode active material is typically a metal oxide, including lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), and lithium nickel manganese cobalt oxide (LiNiMnCoO2). The negative or anode active material is typically graphite, but also includes materials such as silicon and lithium titanate (Li4Ti5O 12 ) material. The metal foil is generally referred to as a current collector, and is usually an aluminum foil in the positive electrode or a copper foil in the negative electrode.

[0013] Manufacturing electrodes generally involves combining a binder material with an electrode active material and other additives and processing in a manner that forms an electrode film before coating the electrode film on a metal foil. Electrodes can be manufactured using either a wet process or a dry process. A wet process involves using a solvent to form a slurry containing a binder, an electrode active material, and other additives. The slurry can then be applied to a current collector and rolled to form an electrode, after which the electrode must be dried. Dry electrode processes reduce the time and energy required for manufacturing because they do not require a drying step.

[0014] However, the dry solvent-free electrode manufacturing process may affect the dispersion of the conductive agent on the electrode active material in the electrode film. The fine conductive particles may agglomerate in the absence of solvents or other dispersants. As a result, the electrochemical performance of the battery cell including the electrode may be affected.

[0015] According to an embodiment, the influence of the dispersion of the conductive agent on the electrode active material in the dry manufacturing process can be alleviated by using a composite binder filled with a conductive agent. The composite binder may include a polymer binder and one or more conductive agents. The polymer binder may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene (PE), polyethylene oxide (PEO), an elastomer or a combination thereof. The conductive agent may include carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanostructures, graphene or a combination thereof. The composite binder may be dry mixed with the electrode active material, and then dry fibrillation may be performed. Due to the physical orientation of the fibrillated composite binder, dry fibrillation may provide a conductive agent with good dispersion and less aggregation relative to the electrode active material.

[0016] A self-supporting electrode film can then be formed by hot pressing a dry electrode mixture of an electrode active material and a fibrillated composite binder. In one embodiment, the self-supporting electrode film may include about 1 wt % to 30 wt % of a fibrillated composite binder and about 70 wt % to 99 wt % of an electrode active material. The self-supporting electrode film can then be laminated to a current collector to form an electrode.

[0017] According to another embodiment, the lamination and adhesion strength of the self-supporting electrode film on the current collector can be improved by using a thin conductive coating applied to the current collector before lamination. The conductive coating can provide a larger surface area and increased compatibility with the fibrillated composite binder. The conductive coating may include a binder and conductive particles. The binder may have a surface energy similar to the fibrillated composite binder of the electrode film, and may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof. Similar surface energies can enhance the lamination and adhesion strength of the electrode film on the current collector. The conductive particles may be carbon particles having an average particle size of less than 2 μm, the carbon particles including carbon black, carbon nanostructures, or a combination thereof. In one embodiment, the conductive coating may include about 50% to 99% by weight of conductive particles and about 1% to 50% by weight of a binder. The conductive coating may have a thickness of less than 10 μm.

[0018] After applying the conductive coating to the current collector, the self-supporting electrode film and the coated current collector can be laminated to form a dry electrode with improved adhesion.

[0019] Figure 1 is a cross-sectional view of a dry electrode 10 according to one embodiment. The dry electrode 10 includes a metal foil 12 having a conductive coating 14 thereon and a self-supporting electrode film 16 laminated to the metal foil 12, wherein the conductive coating 14 is interposed between the metal foil 12 and the self-supporting electrode film 16. The metal foil 12 may be an aluminum foil or a copper foil and may be referred to as a current collector.

[0020] The self-supporting electrode film 16 includes an electrode active material and a fibrillated composite binder. The self-supporting electrode film 16 may include about 1% to 30% by weight of the fibrillated composite binder and about 70% to 99% by weight of the active material. The fibrillated composite binder includes carbon particles and a polymer binder. The polymer binder may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof, and the carbon particles may include carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanostructures, graphene, or a combination thereof.

[0021] Conductive coating 14 includes a polymer binder, which may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof. The polymer binder may be the same polymer binder as the fibrillated composite binder of the self-supporting electrode film 16. Conductive coating 14 may also include carbon particles, which include carbon black, carbon nanostructures, or a combination thereof. Conductive coating 14 may have about 50% to 99% by weight of carbon particles and about 1% to 50% by weight of polymer binder. Conductive coating 14 may have a thickness of 10 μm or less.

[0022] Figure 2 2 is a cross-sectional view of a battery device 200 including an exemplary dry electrode according to one embodiment. The battery device 200 includes a separator 202 between an electrode 204 and an electrode 206. In one variation, the electrode 204 can be a positive electrode and the electrode 206 can be a negative electrode. In another variation, the electrode 204 can be a negative electrode and the electrode 206 can be a positive electrode. As shown, the electrode 204 includes a metal foil 208 having a conductive coating 210 thereon and a self-supporting electrode film 212 laminated to the metal foil 208, wherein the conductive coating 210 is between the metal foil 208 and the self-supporting electrode film 212. The metal foil 208 can be an aluminum foil or a copper foil.

[0023] The self-supporting electrode film 212 includes an electrode active material and a fibrillated composite binder. The self-supporting electrode film 212 may include about 1% to 30% by weight of a fibrillated composite binder and about 70% to 99% by weight of an active material. The fibrillated composite binder includes carbon particles and a polymer binder. The polymer binder may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof, and the carbon particles may include carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanostructures, graphene, or a combination thereof.

[0024] Conductive coating 210 includes a polymer binder, which may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof. The polymer binder may be the same polymer binder as the fibrillated composite binder of the self-supporting electrode film 212. Conductive coating 210 may also include carbon particles, which include carbon black, carbon nanostructures, or a combination thereof. Conductive coating 210 may have about 50% to 99% by weight of carbon particles and about 1% to 50% by weight of polymer binder. Conductive coating 210 may have a thickness of 10 μm or less.

[0025] Electrode 206 includes metal foil 214 and self-supporting electrode film 216. Self-supporting electrode film 216 may include electrode active material and fibrillated composite binder. Self-supporting electrode film 216 may include about 1% by weight to 30% by weight of fibrillated composite binder and about 70% by weight to 99% by weight of active material. Fibrillated composite binder includes carbon particles and polymer binder. Polymer binder may include PTFE, PVDF, PE, PEO, elastomer or a combination thereof, and carbon particles may include carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanostructures, graphene or a combination thereof. In one embodiment, electrode 206 may also include a conductive coating between metal foil 214 and self-supporting electrode film 216.

[0026] Figure 3 38 is a diagram showing a method for dry manufacturing electrode 38. First, a dry electrode mixture of an electrode active material and a fibrillated composite binder is hot pressed to form a self-supporting electrode film 30. The fibrillated composite binder includes carbon particles and a polymer binder. The polymer binder may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof, and the carbon particles may include carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanostructures, graphene, or a combination thereof. The self-supporting electrode film 30 may include about 1% to 30% by weight of the fibrillated composite binder and about 70% to 99% by weight of the active material.

[0027] Next, the metal foil 32 is coated with a conductive coating 34 to form a coated current collector 36. The metal foil 32 may be an aluminum foil or a copper foil. The conductive coating 34 includes a polymer binder, which may include PTFE, PVDF, PE, PEO, an elastomer, or a combination thereof. The polymer binder may be the same polymer binder as the fibrillated composite binder of the self-supporting electrode film 30. The conductive coating 34 may also include carbon particles, which include carbon black, carbon nanostructures, or a combination thereof. The conductive coating 34 may have about 50% to 99% by weight of carbon particles and about 1% to 50% by weight of a polymer binder. The conductive coating 34 may have a thickness of 10 μm or less.

[0028] Finally, the self-supporting electrode film 30 is laminated onto the coated current collector 36 to form the electrode 38. Notably, the dry manufacturing method does not involve the use of solvents.

[0029] The algorithm, method or process disclosed herein can be delivered 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 algorithm, method or process can be stored in various forms as data and instructions that can be executed 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 that can be modified and stored on a writable storage medium such as an optical disk, a random access memory device or other magnetic and optical media. The algorithm, method or process can also be implemented by a software executable object. Alternatively, a suitable hardware component (such as an application-specific integrated circuit, a field programmable gate array, a state machine or other hardware component or device) or a combination of firmware, hardware and software components can be used to embody the algorithm, method or process in whole or in part.

[0030] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure.

[0031] As previously described, the features of the various embodiments may be combined to form additional embodiments of the invention that may not be explicitly described or shown. Although 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, it will be appreciated by those of ordinary skill in the art that one or more features or characteristics may be compromised to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, and the like. Thus, embodiments described as being less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of this disclosure and may be desirable for a particular application.

[0032] According to the present invention, an electrode assembly is provided: a metal foil having a conductive coating including a polymer binder thereon; and a self-supporting electrode film of an active material and a fibrillated composite binder, the fibrillated composite binder including carbon particles and the same polymer binder, the self-supporting electrode film being laminated with the metal foil so that the conductive coating is interposed between the metal foil and the self-supporting electrode film.

[0033] According to an embodiment, the carbon particles include carbon black and nanostructures.

[0034] According to an embodiment, the nanostructure is multi-walled, single-walled, graphene or a combination thereof.

[0035] According to an embodiment, the self-supporting electrode film has 1 wt% to 30 wt% of the fibrillated composite binder.

[0036] According to an embodiment, the self-supporting electrode film has 70 to 99 wt % of the active material.

[0037] According to an embodiment, the conductive coating further comprises carbon particles.

[0038] According to an embodiment, the carbon particles of the conductive coating include carbon black, nanostructures or a combination thereof.

[0039] According to an embodiment, the conductive coating has 50% to 99% by weight of the carbon particles of the conductive coating.

[0040] According to an embodiment, the conductive coating has 1 wt % to 50 wt % polymer binder.

[0041] According to an embodiment, the thickness of the conductive coating is 10 μm or less.

[0042] According to the present invention, there is provided a battery comprising: a separator; and a pair of electrodes sandwiching the separator, at least one of the electrodes comprising a laminated layer of: (i) a metal foil having thereon a conductive coating comprising a polymer binder and (ii) a self-supporting electrode film of an active material and a fibrillated composite binder comprising carbon particles and the same polymer binder.

[0043] According to an embodiment, the carbon particles include carbon black and nanostructures.

[0044] According to an embodiment, the nanostructure is multi-walled, single-walled, graphene or a combination thereof.

[0045] According to an embodiment, the self-supporting electrode film has 1 wt% to 30 wt% of the fibrillated composite binder.

[0046] According to an embodiment, the conductive coating has 1 wt % to 50 wt % polymer binder.

[0047] According to an embodiment, the conductive coating further comprises carbon particles.

[0048] According to an embodiment, the carbon particles of the conductive coating include carbon black, nanostructures or a combination thereof.

[0049] According to an embodiment, the thickness of the conductive coating is 10 μm or less.

[0050] According to the present invention, a method for dry manufacturing of battery electrodes includes: hot pressing a dry electrode mixture of an active material and a fibrillated composite binder to form a self-supporting electrode film, wherein the fibrillated composite binder has carbon particles and a polymer binder; coating a current collector with a conductive coating to form a coated current collector, wherein the conductive coating includes carbon particles and the same polymer binder; and laminating the self-supporting electrode film onto the coated current collector to form a battery electrode.

Claims

1. An electrode assembly, comprising: a metal foil having thereon a conductive coating comprising a polymer binder; and A self-supporting electrode film of active material and a fibrillated composite binder, the fibrillated composite binder comprising carbon particles and the same polymer binder, the self-supporting electrode film being laminated with the metal foil such that the conductive coating is interposed between the metal foil and the self-supporting electrode film.

2. The electrode assembly of claim 1, wherein the carbon particles comprise carbon black and nanostructures.

3. The electrode assembly of claim 2, wherein the nanostructure is multi-walled, single-walled, graphene, or a combination thereof.

4. The electrode assembly of claim 1, wherein the self-supporting electrode film has 1 wt% to 30 wt% of the fibrillated composite binder.

5. The electrode assembly of claim 1, wherein the self-supporting electrode film has 70 wt% to 99 wt% of the active material.

6. The electrode assembly of claim 1, wherein the conductive coating further comprises carbon particles.

7. The electrode assembly of claim 6, wherein the carbon particles of the conductive coating comprise carbon black, nanostructures, or a combination thereof.

8. The electrode assembly of claim 6, wherein the conductive coating has 50 wt% to 99 wt% of the carbon particles of the conductive coating.

9. The electrode assembly of claim 1, wherein the conductive coating has 1 wt% to 50 wt% of the polymer binder.

10. The electrode assembly of claim 1, wherein the conductive coating has a thickness of 10 μm or less.

11. A battery comprising: separators; and A pair of electrodes having the separator sandwiched therebetween, at least one of the electrodes comprising a laminate of (i) a metal foil having thereon a conductive coating comprising a polymer binder and (ii) a self-supporting electrode film of an active material and a fibrillated composite binder comprising carbon particles and the same polymer binder.

12. The battery of claim 11, wherein the carbon particles include carbon black and nanostructures.

13. The battery of claim 12, wherein the nanostructure is multi-walled, single-walled, graphene, or a combination thereof.

14. The battery of claim 11, wherein the self-supporting electrode film has 1 wt% to 30 wt% of the fibrillated composite binder.

15. A method for dry manufacturing of battery electrodes, comprising: hot pressing a dry electrode mixture of active material and a fibrillated composite binder having carbon particles and a polymer binder to form a self-supporting electrode film; coating the current collector with a conductive coating to form a coated current collector, the conductive coating comprising carbon particles and the same polymer binder; and The self-supporting electrode film is laminated to the coated current collector to form the battery electrode.

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