Method for manufacturing a cathode, cathode and battery cell

Abstract

Method for manufacturing a cathode (22) for a battery cell (2), wherein a cathodic active material phase (42) and an electrolyte phase (15) are applied to a surface of a current collector (32) of the cathode (22) by means of inkjet printing, wherein the cathodic active material phase (42) in the form of active material lamellae (45) is applied to the surface of the current collector (32) of the cathode (22) in such a way, and the electrolyte phase (15) in the form of electrolyte lamellae (25) is applied to the surface of the current collector (32) of the cathode (22) in such a way that the lamellae (25, 45) are oriented at least approximately perpendicular to the surface of the current collector (32) of the cathode (22).

Description

[0001] The present invention relates to a method for producing a cathode for a battery cell, wherein a cathodic active material phase and an electrolyte phase are applied to a surface of a current collector by means of inkjet printing. The invention also relates to a cathode for a battery cell comprising a current collector, a cathodic active material phase, and an electrolyte phase. Furthermore, the invention relates to a battery cell comprising at least one cathode according to the invention. State of the art

[0002] Electrical energy can be stored using batteries. Batteries convert chemical reaction energy into electrical energy. A distinction is made between primary and secondary batteries. Primary batteries are only functional once, while secondary batteries, also known as accumulators, are rechargeable. A battery consists of one or more battery cells.

[0003] Lithium-based battery cells, especially lithium-ion battery cells, are primarily used in accumulators. These are characterized by, among other things, high energy density, good thermal stability, and extremely low self-discharge. Lithium-ion battery cells are used in motor vehicles, particularly in electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs).

[0004] Such lithium-based battery cells have a positive electrode, also called the cathode, and a negative electrode, also called the anode, as well as a separator between the anode and cathode. The cathode and the anode each comprise an electrically conductive current collector, onto which an electrode layer is applied. The electrode layer, which contains active material, optionally binders and conductive additives, as well as electrolyte and other auxiliary materials, can be applied to the current collector, for example, by inkjet printing.

[0005] The active material for the cathode is, for example, one or more lithium-intercalating metal oxides, such as nickel and / or cobalt and / or manganese oxide, for example nickel-cobalt-manganese oxide (NMC), or sulfur-polyacrylonitrile composite, or a sulfur-containing material. The active material for the anode is lithium-intercalating material, for example, graphite and / or lithium-alloyable material, for example, silicon and / or metallic lithium.

[0006] Lithium atoms are embedded in the active material of the anode. During operation of the battery cell, i.e., during a discharge process, electrons flow in an external circuit from the anode to the cathode. This oxidizes the lithium-containing active material at the anode. Inside the battery cell, lithium ions migrate from the anode to the cathode during discharge. During charging, the lithium ions migrate from the cathode to the anode.

[0007] CN 105 098 227 A discloses a lithium-ion battery and an associated manufacturing process. In this process, an active material layer is applied to a current collector by means of inkjet printing, and an electrolyte layer is applied to the active material layer.

[0008] US patent 2013 / 0129914A1 discloses an electrode for a lithium-ion battery and an associated manufacturing process. In this process, several active material layers are applied to a current collector using inkjet printing. The individual active material layers have different active material densities. An electrolyte layer is applied to the active material layers.

[0009] A method for achieving resolutions of less than one micrometer in inkjet printing is described in the article “Printing sub-micrometer lines based on Electrohydrodynamics” from IEEE, 2012, pages 316 to 319.

[0010] Further state of the art is known from US 2004 / 0 126 655 A1, US 2012 / 0 282 530 A1 and US 2014 / 0 186 519 A1. Disclosure of the invention

[0011] A method for manufacturing a cathode for a battery cell, in particular for a lithium-based battery cell, is proposed, wherein a cathodic active material phase and an electrolyte phase are applied to a surface of a current collector by means of inkjet printing.

[0012] The cathodic active material phase is applied to the surface of the current collector in the form of active material lamellae, and the electrolyte phase is applied to the surface of the current collector in the form of electrolyte lamellae. The cathodic active material phase and the electrolyte phase are applied to the surface of the current collector in such a way that the active material lamellae and the electrolyte lamellae are oriented at least approximately perpendicular to the surface of the current collector. A direction perpendicular to the surface of the current collector is also referred to as the vertical direction in the following.

[0013] The cathodic active material phase consists, for example, of active material, possibly binder, possibly conductive additives, possibly electrolyte and possibly other auxiliary materials, especially to improve viscosity.

[0014] According to a preferred embodiment of the invention, the cathodic active material phase and the electrolyte phase are applied alternately in a horizontal direction to the surface of the current collector. The horizontal direction extends parallel to the surface of the current collector.

[0015] Preferably, the cathodic active material phase and the electrolyte phase are applied to the surface of the current collector in a horizontal direction in the form of strips with a width in a range between 1 µm (micrometer) and 25 µm, alternating and immediately adjacent to each other.

[0016] According to an advantageous embodiment of the invention, the cathodic active material phase and the electrolyte phase are applied to the surface of the current collector in several successive layers. Each applied layer is partially or completely dried before the application of the following layer, for example by infrared irradiation.

[0017] A cathode for a battery cell, particularly for a lithium-based battery cell, is also proposed, comprising a current collector, a cathodic active material phase, and an electrolyte phase.

[0018] According to the invention, the cathodic active material phase is applied to the surface of the current collector in the form of active material lamellae, and the electrolyte phase is applied to the surface of the current collector in the form of electrolyte lamellae. The active material lamellae and the electrolyte lamellae of the cathode are oriented at least approximately perpendicular to the surface of the current collector. A direction perpendicular to the surface of the current collector is hereinafter also referred to as the vertical direction.

[0019] According to a preferred embodiment of the invention, the active material lamellae and the electrolyte lamellae are applied alternately in a horizontal direction to the surface of the cathode current collector. The horizontal direction extends parallel to the surface of the current collector.

[0020] Preferably, the active material lamellae have a horizontal extent in a range between 1 µm and 25 µm. The horizontal extent of the active material lamellae is defined as their extent in the horizontal direction.

[0021] Preferably, the electrolyte lamellae have a horizontal extent in a range between 1 µm and 25 µm. The horizontal extent of the electrolyte lamellae is defined as their extent in the horizontal direction.

[0022] According to an advantageous embodiment of the invention, the active material lamellae of the cathode have a vertical extent in a range between 10 µm and 150 µm. The vertical extent of the active material lamellae is the extent of the active material lamellae in the vertical direction.

[0023] According to an advantageous embodiment of the invention, the electrolyte lamellae of the cathode also have a vertical extent in a range between 10 µm and 150 µm. The vertical extent of the electrolyte lamellae is the extent of the electrolyte lamellae in the vertical direction.

[0024] Furthermore, a battery cell is proposed which comprises at least one cathode according to the invention. The battery cell according to the invention preferably also comprises an anode and a separator which separates the cathode from the anode.

[0025] A battery cell according to the invention is advantageously used in an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or a consumer electronics product. However, other applications are also conceivable. Advantages of the invention

[0026] The method according to the invention allows the production of a cathode in a relatively short cycle time and at relatively low cost. Furthermore, the composition of the cathodic active material and the electrolyte can be flexibly changed as needed and adapted to special requirements.

[0027] By applying the cathodic active material and electrolyte to the current collector using inkjet printing, a lamellar microstructure can be created in the cathode. This results in a shortening of the ion transport paths in the vertical direction. Consequently, higher effective conductivity and diffusivity of the conducting salt in the electrolyte are achieved. This allows for a higher charging and discharging rate of the battery cell, as well as a higher energy density due to a reduction in the electrolyte content in the cathode. A further advantage is the reduction in the need for conductive additives and binders, as these are preferably only used in the active material phase. Brief description of the drawings

[0028] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0029] They show: Fig. 1: a schematic representation of a battery cell, Fig. 2: a schematic representation of an inkjet printing process for the production of a cathode and Fig. 3: A schematic representation of a cathode after the manufacturing process. Embodiments of the invention

[0030] In the following description of embodiments of the invention, identical or similar elements are designated by the same reference numerals, and repeated descriptions of these elements are omitted in individual cases. The figures represent the subject matter of the invention only schematically.

[0031] A battery cell 2 is in Fig. Figure 1 shows a schematic representation. The battery cell 2 comprises a cell housing 3, which is prismatic, in this case cuboid. The battery cell 2 includes a negative terminal 11 and a positive terminal 12. A voltage supplied by the battery cell 2 can be tapped via terminals 11 and 12. Furthermore, the battery cell 2 can also be charged via terminals 11 and 12.

[0032] Within the cell housing 3 of the battery cell 2, an electrode winding is arranged, which has two electrodes, namely an anode 21 and a cathode 22. The anode 21 and the cathode 22 are each made of foil and wound to the electrode winding with a separator 23 in between. Alternatively, the anode 21 and the cathode 22 can also be stacked to form an electrode stack with the separator 23 in between.

[0033] The anode 21 and the cathode 22 are thus separated from each other by the separator 23. The separator 23 is film-like. The separator 23 is electrically insulating but ionically conductive, i.e., permeable to lithium ions. The separator 23 consists, for example, of a porous polymer and a liquid electrolyte containing a solvent and a lithium salt, and optionally other additives, and / or of a ceramic lithium-ion conductor and / or a solid conductor consisting of a polymer (e.g., polyethylene oxide (PEO), polystyrene-polyethylene oxide block copolymer (PS-b-PEO)) and a lithium salt, and optionally other additives.

[0034] The anode 21 comprises an anodic electrode layer 41 and a current collector 31, which are laid flat against each other and connected to one another. The current collector 31 of the anode 21 is electrically conductive and made of a metal, for example copper, and is electrically connected to the negative terminal 11 of the battery cell 2.

[0035] The cathode 22 comprises a current collector 32, a cathodic active material phase 42, and an electrolyte phase 15. The current collector 32 of the cathode 22 is electrically conductive and made of a metal, for example, aluminum. The current collector 32 of the cathode 22 can also be made of another material, for example, carbon. The current collector 32 of the cathode 22 is electrically connected to the positive terminal 12 of the battery cell 2. The electrolyte phase 15 and the cathodic active material phase 42 are connected to the current collector 32 of the cathode 22.

[0036] Fig. Figure 2 shows a schematic representation of an inkjet printing process for manufacturing the cathode 22 of battery cell 2.

[0037] Several electrolyte nozzles 51 and several active material nozzles 52 are arranged side by side on a printhead 50. The printhead 50 is arranged at a defined distance from the current collector 32 of the cathode 22, and the electrolyte nozzles 51 and the active material nozzles 52 are directed towards the surface of the current collector 32 of the cathode 22.

[0038] An active material ink, containing an active material, is sprayed from the active material nozzles 52 onto the current collector 32 of the cathode 22. The active material ink may also contain other components dissolved or dispersed in a solvent. For example, the active material ink comprises the following components (specified in wt%, based on the dried active material phase): Active material: 50-95% Solid electrolyte: 0-40% Key additive: 0-10% Binder: 0-10% Possibly other excipients: 0-10%

[0039] The active material includes, for example, sulfur-polyacrylonitrile composite (SPAN), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), overlithiated transition metal oxides, high-voltage spinels, or lithium iron phosphate (LFP). The active material is in the form of particles, each with an effective diameter ranging from 0.5 µm (micrometers) to 5 µm.

[0040] The solid electrolyte is preferably a polymer and / or inorganic solid electrolyte, for example polyethylene oxide (PEO). A lithium-containing conducting salt, for example lithium bis(trifluoromethane)sulfonimide (LiTFSI), is dissolved in or mixed with the polymeric solid electrolyte.

[0041] The main additive is preferably carbon black, soot and / or graphite and / or carbon fibers.

[0042] The optional binder is, for example, polyvinylidene fluoride (PVDF). The binder serves to improve contact and mechanical stability in the cathodic active material phase 42, particularly when a relatively high proportion of active material is contained in the active material ink.

[0043] Furthermore, the active material ink contains a solvent or dispersant in which the aforementioned components are dissolved and / or dispersed. The viscosity and drying rate of the active material ink can be adjusted by means of the solvent or dispersant, and optionally other additives.

[0044] An electrolyte ink, containing the electrolyte, is sprayed from the electrolyte nozzles 51 onto the current collector 32 of the cathode 22. The electrolyte ink may also contain other components dissolved and / or dispersed in a solvent. For example, the electrolyte ink comprises the following components (specified in wt%, wt% based on the dried electrolyte phase 15): Solid electrolyte: 80-100% Key additive: 0-10% Binder: 0-10% Possibly other excipients: 0-10%

[0045] Preferably, however, the electrolyte ink is free of the conductive additive and free of the binder.

[0046] The solid electrolyte is preferably a polymer and / or inorganic solid electrolyte, for example polyethylene oxide (PEO). A lithium-containing conducting salt, for example lithium bis(trifluoromethane)sulfonimide (LiTFSI), is dissolved in or mixed with the polymeric solid electrolyte.

[0047] The optional leading additive preferably consists of carbon black, soot and / or graphite and / or carbon fibers.

[0048] The optional binder is, for example, polyvinylidene fluoride (PVDF). The binder serves to improve contact, particularly at the interfaces with the cathodic active material phase 42.

[0049] Furthermore, the electrolyte ink contains a solvent or dispersant in which the aforementioned components are dissolved and / or dispersed. The viscosity and drying rate of the electrolyte ink can be adjusted by means of the solvent or dispersant.

[0050] The active material ink containing the cathodic active material is applied to the surface of the current collector 32 of the cathode 22 by means of inkjet printing. Likewise, the electrolyte ink containing the electrolyte is applied to the surface of the current collector 32 of the cathode 22 by means of inkjet printing.

[0051] The active material ink with the cathodic active material and the electrolyte ink with the electrolyte are applied alternately in a horizontal direction to the surface of the current collector 32 of the cathode 22. The cathodic active material phase 42 and the electrolyte phase 15 are applied horizontally in the form of strips, approximately 10 µm wide, directly adjacent to each other on the surface of the current collector 32 of the cathode 22. This width corresponds to the distance between each electrolyte nozzle 51 and the adjacent active material nozzle 52 on the printhead 50.

[0052] The active material ink with the cathodic active material and the electrolyte ink with the electrolyte are applied in several successive layers to the surface of the current collector 32 of the cathode 22. Each applied layer is partially or completely dried, for example by infrared irradiation, before the next layer is applied. This prevents the active material ink from mixing with the electrolyte ink.

[0053] Fig. Figure 3 shows a schematic representation of a cathode 22 after the manufacturing process.

[0054] Applying the active material ink with the cathodic active material to the current collector 32 of the cathode 22 creates active material lamellae 45, which are oriented perpendicular to the surface of the current collector 32 of the cathode 22. Applying the electrolyte ink with the electrolyte to the current collector 32 of the cathode 22 creates electrolyte lamellae 25, which are also oriented perpendicular to the surface of the current collector 32 of the cathode 22.

[0055] The active material lamellae 45 and the electrolyte lamellae 25 are applied alternately in a horizontal direction to the surface of the current collector 32 of the cathode 22. The active material lamellae 45 have a horizontal extent D2 of approximately 10 µm. The electrolyte lamellae 25 have a horizontal extent D1 of approximately 10 µm. The active material lamellae 45 and the electrolyte lamellae 25 each have a vertical extent L in a range between 10 µm and 150 µm.

[0056] In an alternative embodiment of the cathode 22, an additional intermediate lamella (not shown here) is inserted between each active material lamella 45 and each electrolyte lamella 25. The intermediate lamellae have the same vertical extent L as the active material lamellae 45 and the electrolyte lamellae 25.

[0057] In this case, an intermediate nozzle is provided on the printhead 50 between each electrolyte nozzle 51 and an active material nozzle 52. An intermediate material ink is injected from the intermediate nozzle onto the surface of the current collector 32 of the cathode 22.

[0058] The intermediate material ink contains several components that are dissolved and / or dispersed in a solvent. For example, the intermediate material ink comprises the following components (specified as a percentage by weight, based on the dried intermediate material phase): Active material: 0-40% Solid electrolyte: 0-40% Key ingredient: 30-90% Binder: 0-10% Possibly other excipients: 0-10%

[0059] The active material includes, for example, sulfur-polyacrylonitrile composite (SPAN), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), overlithiated transition metal oxides, high-voltage spinels, or lithium iron phosphate (LFP). The active material is in the form of particles, each with an effective diameter ranging from 0.5 µm (micrometers) to 5 µm.

[0060] The solid electrolyte is preferably a polymer and / or inorganic solid electrolyte, for example polyethylene oxide (PEO). A lithium-containing conducting salt, for example lithium bis(trifluoromethane)sulfonimide (LiTFSI), is dissolved in or mixed with the polymeric solid electrolyte.

[0061] The main additive is preferably carbon black, soot and / or graphite and / or carbon fibers.

[0062] The optional binder is, for example, polyvinylidene fluoride (PVDF). The binder serves to improve contact and mechanical stability in the intermediate ink, especially when the intermediate ink contains a relatively high proportion of active material.

[0063] The cathode 22 produced in this way can be used to manufacture the battery cell 2. First, a separator 23 is applied to the cathode 22. The anode 21 is then applied to the separator 23. The cathode 22, the anode 21, and the separator 23 are then wound into an electrode coil, which is then inserted into the cell housing 3 of the battery cell 2.

[0064] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, within the scope specified by the claims, a multitude of modifications are possible that fall within the bounds of what is considered skilled in the art.

Claims

[1] Method for producing a cathode (22) for a battery cell (2), wherein a cathodic active material phase (42) and an electrolyte phase (15) are applied to a surface of a current collector (32) of the cathode (22) by means of inkjet printing, wherein the cathodic active material phase (42) in the form of active material lamellae (45) is applied to the surface of the current collector (32) of the cathode (22) in such a way, and the electrolyte phase (15) in the form of electrolyte lamellae (25) is applied to the surface of the current collector (32) of the cathode (22) in such a way that the lamellae (25, 45) are oriented at least approximately perpendicular to the surface of the current collector (32) of the cathode (22). [2] Method according to claim 1, wherein the cathodic active material phase (42) and the electrolyte phase (15) are applied alternately in a horizontal direction to the surface of the current collector (32) of the cathode (22). [3] Method according to one of the preceding claims, wherein the cathodic active material phase (42) and the electrolyte phase (15) are applied in a horizontal direction in the form of strips with a width between 1 µm and 25 µm, each immediately adjacent to the other, onto the surface of the current collector (32) of the cathode (22). [4] Method according to one of the preceding claims, wherein the cathodic active material phase (42) and the electrolyte phase (15) are applied in several successive layers to the surface of the current collector (32) of the cathode (22), wherein each applied layer is partially or completely dried before the application of the following layer. [5] Cathode (22) for a battery cell (2), comprising a current collector (32), a cathodic active material phase (42) and an electrolyte phase (15), characterized by , that the cathodic active material phase (42) in the form of active material lamellae (45) is applied to the surface of the current collector (32) of the cathode (22), and the electrolyte phase (15) is applied to the surface of the current collector (32) of the cathode (22) in the form of electrolyte lamellae (25), and the lamellae (25, 45) are oriented at least approximately perpendicular to the surface of the current collector (32) of the cathode (22). [6] Cathode (22) according to claim 5, characterized by , that the active material lamellae (45) and the electrolyte lamellae (25) are applied alternately in a horizontal direction to the surface of the current collector (32) of the cathode (22). [7] Cathode (22) according to one of claims 5 to 6, characterized by, that the active material lamellae (45) and / or the electrolyte lamellae (25) have a horizontal extent (D1, D2) in a range between 1 µm and 25 µm. [8] Cathode (22) according to one of claims 5 to 7, characterized by , that the active material lamellae (45) and the electrolyte lamellae (25) have a vertical extent (L) in a range between 10 µm and 150 µm. [9] Battery cell (2) comprising at least one cathode (22) according to any one of claims 5 to 8. [10] Use of the battery cell (2) according to claim 9 in an electric vehicle (EV), in a hybrid vehicle (HEV), in a plug-in hybrid vehicle (PHEV) or in a consumer electronics product.

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