DE102021132285A1 - Process for preparing battery electrodes and battery electrode - Google Patents

Abstract

Method for processing battery electrodes, comprising the steps:- providing electrode material, the electrode material comprising carrier material which has a coating on one or both sides;- using infrared radiation to introduce heat into the coating for loosening, in particular partial or partial removal, the coating.

Description

The present invention relates to a method for preparing battery electrodes and a battery electrode.

For the recycling of energy storage cells, such as lithium-ion cells, or production rejects during their manufacture, the separation of the coating material from the current collector film plays a crucial role. The active material of the cathode is particularly valuable and, at around 40%, accounts for a significant proportion of the cell costs. According to the current status, the separation is implemented as a purely mechanical process, for example by shredding, grinding and sieving. Alternatively or additionally, solvents are used, which may achieve a higher separation efficiency than purely mechanical processes, but at the same time entail cost disadvantages and are not optimal in terms of occupational safety and sustainability. For example, for the separation of electrode substrate sheets and the coating DE 699 05 134 T2 suggest detaching the coating by bending the coated substrate with a sufficiently small bend radius. Working with solvents etc. is also suggested there. In the case of flexible current collector foils, however, bending is not successful, primarily because of the strong adhesion between the coating and the current collector foil. As already mentioned, the use of solvents entails additional disadvantages. The DE 10 2009 059 423 A1 relates to a method for recovering lithium from a lithium-containing feedstock, wherein the feedstock is heated in a reactor with carbon by directly inductively heating the carbon. However, the starting material is available as bulk material, which entails additional work steps and does not allow strip-shaped processing. In addition, the approach is energy-intensive and complex in terms of system technology.

It is therefore an object of the present invention to specify a method for preparing battery electrodes and a battery electrode, in which case the aforementioned disadvantages can be eliminated. In addition, the process should be inexpensive and easy to implement industrially.

• - Bereitstellen von Elektrodenmaterial, wobei das Elektrodenmaterial Trägermaterial, wie insbesondere eine Stromableiterfolie, umfasst, welche ein- oder beidseitig eine Beschichtung aufweist;
• - Verwenden von Infrarotstrahlung zum Einbringen von Wärme in die Beschichtung zum Lösen, insbesondere An- oder Ablösen, der Beschichtung.

Bei dem Trägermaterial handelt es sich insbesondere um eine Trägerfolie, auch Stromableiterfolie genannt, einer Elektrode einer elektrischen Energiespeicherzelle, vorliegend insbesondere um eine Aluminium- oder Kupferfolie, wie sie in Lithiumionenbatterien verwendet wird. Aluminium wird dabei oftmals für Kathoden verwendet, Kupfer für die Anode. Das Trägermaterial kann ein- oder beidseitig beschichtet sein. Das Beschichtungsmaterial umfasst zunächst gemäß einer Ausführungsform jeweils Aktivmaterial, Leitruß, (Lösungsmittel-)Binder und Additive. Für die Herstellung derartiger Batterieelektroden werden das Aktivmaterial, der Leitruß sowie der Binder in Lösungsmittel dispergiert und anschließend auf das Trägermaterial aufgebracht. Nach der Trocknung ist der Binder ausgehärtet und sorgt für die Adhäsion der Beschichtung am Trägermaterial. Die Elektroden werden im Anschluss kalandriert und im Rahmen der Zellassemblierung für den Einsatz in elektrifizierten Fahrzeugen fertiggestellt. Sobald die Batteriezelle das Ende ihrer Lebensdauer erreicht hat, wird sie recycelt. Das vorliegende Verfahren ist in gleicher Weise für Batterieelektroden geeignet, welche ohne Lösungsmittel hergestellt wurden, vorausgesetzt dass eine stoffschlüssige Adhäsion vorliegt, die durch eine thermische Behandlung neutralisiert werden kann. Zweckmäßigerweise wird vorliegend die Beschichtung unmittelbar oder direkt der Infrarotstrahlung bzw. einer Infrarotbestrahlung ausgesetzt. In der Folge kommt es zu einer Temperaturerhöhung der oder in der Beschichtung, welche so ausgeführt wird, dass deren Stoffzusammenhalt, zumindest bereichsweise, aufgelöst wird.This object is achieved by a method according to claim 1 and by a battery electrode according to claim 12. Further advantages and features emerge from the subclaims and the description and the attached figure. According to the invention, a method for preparing battery electrodes comprises the steps:

• - Providing electrode material, wherein the electrode material comprises carrier material, such as in particular a current conductor foil, which has a coating on one or both sides;
• - Using infrared radiation to introduce heat into the coating to loosen, in particular to partially or detached, the coating.

The carrier material is, in particular, a carrier foil, also known as a current conductor foil, of an electrode of an electrical energy storage cell, in this case in particular an aluminum or copper foil, as is used in lithium-ion batteries. Aluminum is often used for the cathode and copper for the anode. The carrier material can be coated on one or both sides. According to one embodiment, the coating material initially comprises active material, conductive carbon black, (solvent) binders and additives. For the production of such battery electrodes, the active material, the conductive carbon black and the binder are dispersed in a solvent and then applied to the carrier material. After drying, the binder has hardened and ensures the adhesion of the coating to the substrate. The electrodes are then calendered and completed as part of cell assembly for use in electrified vehicles. Once the battery cell has reached the end of its useful life, it is recycled. The present method is equally applicable to battery electrodes made without solvent, provided there is a material bond that can be neutralized by thermal treatment. In this case, the coating is expediently exposed directly or directly to infrared radiation or infrared radiation. As a result, there is an increase in temperature of or in the coating, which is carried out in such a way that the material cohesion is broken, at least in certain areas.

Infrared radiation, also IR radiation, infrared, is electromagnetic radiation in the spectral range between visible light and longer-wave terahertz radiation. In the present case, light is meant in particular with a wavelength between 780 nm and 1 mm.

• - Zersetzen eines in der Beschichtung enthaltenen Binders durch das Einbringen der Wärme.

According to one embodiment, the heat input leads in particular to the binder contained in the coating decomposing. This leads to the dissolution of the material cohesion, at least in certain areas. According to one embodiment, the method comprises the step:

• - Decomposition of a binder contained in the coating due to the introduction of heat.

In other words, the heat is introduced in such a way that the binder contained in the coating is decomposed, as a result of which the above-described dissolution of the material cohesion is achieved.

Fluorine-containing polymers are usually used as binders, such as polyvinylidene fluoride homopolymer (PVDF) and polyvinylidene fluoride copolymer (PVDF copolymer), and any mixtures thereof.

Advantageously, the infrared radiation or infrared radiation is less energy-intensive than, for example, heating in an oven, since the particularly immediate or direct infrared radiation can achieve a sufficiently high energy input into the material in a very short time. This reduces the process time. In this way, scrap material in strip form can be heated and stripped of the coating in the throughput. In addition, the efficiency of infrared heating on black surfaces such as those found in battery electrodes, such as Li-ion cell cathodes, is at a high level because the emissivity is very high. Advantageously, the coating is not heated through for a long time, as would be the case in an oven. As a result, the process can be described as very gentle. Advantageously, in the present case it can be avoided, at least to a large extent, that any reactions which adversely affect the coating material, such as the formation of gaseous hydrogen fluoride (HF), take place. This reacts, for example, with the lithium from the cathode active material to form inactive lithium fluoride (LiF), which reduces the capacity of the active material.

• - Zuführen des Elektrodenmaterials einer Qualitätskontrolle;
• - Zuführen des Elektrodenmaterials einer Aufbereitungsanlage zum Aufbereiten von als defekt erkanntem Elektrodenmaterial.

According to one embodiment, the method comprises the steps:

• - Supplying the electrode material to a quality control;
• - Supplying the electrode material to a processing plant for processing electrode material identified as defective.

The method can be used, for example, as a downstream component of quality control when sorting out NiO coating sections (NiO - not OK). The strip material is sorted out and fed directly into the separation.

• - Einbringen der Wärme über die ganze Breite der Beschichtung.

Conveniently, the method includes the step:

• - Introduction of the heat over the entire width of the coating.

The carrier material or the carrier foil is transported along a conveying direction. The aforesaid width of the coating extends transversely to the aforesaid conveying direction.

• - Entlangführen des Trägermaterials an einer Vorrichtung zur Infrarotbestrahlung.

According to one embodiment, the method comprises the step:

• - Leading the carrier material along a device for infrared radiation.

According to one embodiment, the carrier material is passed under a device for infrared radiation. The carrier material is expediently guided through or along along the aforementioned conveying direction. The heating advantageously takes place only in sections along the longitudinal direction/conveying direction of the electrode material. As a result, a lean system structure can be achieved. Since the process is designed as a continuous process, large quantities can still be processed. In particular, the method can also be integrated into existing production plants with little effort.

• - Verwenden mechanischer und/oder pneumatischer Verfahren zum Entfernen der gelösten Beschichtung.

According to one embodiment, the method comprises the step:

• - Using mechanical and/or pneumatic methods to remove the loosened coating.

In order to achieve complete detachment or removal of partially or detached coating material, other alternative methods, such as pneumatic and/or mechanical methods, can be used.

• - Bestrahlen des Elektrodenmaterials mit Druckluft zum Entfernen der gelösten Beschichtung.

According to one embodiment, the method comprises the step:

• - Blast the electrode material with compressed air to remove the dissolved coating.

Abrasive materials can also be used with compressed air blasting. According to one embodiment, snow jet irradiation also takes place, which, as a method that is particularly gentle on the material, has advantages.

• - Verwenden einer Absaugung zum Sammeln des separierten Beschichtungsmaterials.

According to one embodiment, the method comprises the step:

• - Using suction to collect the separated coating material.

The separated coating material is collected, for example, in a suitable collection container.

• - Aufbereiten und Wiederverwenden des separierten Beschichtungsmaterials.

Soweit möglich oder nötig, wird das Beschichtungsmaterial in seine einzelnen Bestandteile zerlegt. Alternativ kann das Beschichtungsmaterial auch als solches weiterverwendet werden. Gemäß der ersten Alternative wird das gewonnene Beschichtungsmaterial beispielsweise einer hydrometallurgischen Aufarbeitung zugeführt, bei der eine Abtrennung der einzelnen Elemente des Aktivmaterials erfolgt. Bei einer NMC-Elektrode werden entsprechend Nickel (N), Mangan (M) und Cobalt (C) sowie Lithium in Reinform gewonnen und anschließend in einer Materialsynthese wieder zu NMC verarbeitet. Gemäß der zweiten Alternative kann das gewonnen Beschichtungsmaterial/Aktivmaterial auch direkt (ohne Hydrometallurgie) wieder- oder weiterverwendet werden. Bei End-of-Life-Zellen ist hierbei mit Kapazitätsverlust zu rechnen, für Produktionsausschuss wäre dies theoretisch nicht der Fall, da das Aktivmaterial noch nicht gealtert ist, sondern direkt aus der Produktion kommt.Conveniently, the method includes the step:

• - Processing and reuse of the separated coating material.

As far as possible or necessary, the coating material is broken down into its individual components. Alternatively, the coating material can also be reused as such. According to the first alternative, the coating material obtained is fed, for example, to hydrometallurgical processing, in which the individual elements of the active material are separated off. With an NMC electrode, nickel (N), manganese (M) and cobalt (C) as well as lithium are obtained in their pure form and then processed back into NMC in a material synthesis. According to the second alternative, the coating material/active material obtained can also be reused or reused directly (without hydrometallurgy). In the case of end-of-life cells, a loss of capacity is to be expected, but this would theoretically not be the case for production rejects, since the active material has not yet aged but comes directly from production.

• - Aufbereiten und Weiter- oder Wiederverwenden des Trägermaterials.

Vorteilhafterweise wird das Trägermaterial wieder- oder zumindest weiterverwendet.According to one embodiment, the method comprises the step:

• - Processing and further or reuse of the carrier material.

Advantageously, the carrier material is reused or at least reused.

The invention also relates to a battery electrode comprising materials obtained by the method according to the invention. The battery electrode is part of an electrical energy storage cell, such as a lithium ion cell. Battery electrodes or energy storage cells of the type in question are used, for example, for traction batteries in motor vehicles, in particular passenger cars, motorcycles or commercial vehicles.

Further advantages and features result from the following description of an embodiment of the method with reference to the attached figure.

• 1: eine schematische Ansicht einer Ausführungsform des Verfahrens.

It shows:

• 1 : a schematic view of an embodiment of the method.

1 shows a schematic view of a battery electrode, comprising a carrier material 10 on which a coating 20 is applied, in the present case only on one side. The carrier material 10 is transported along a conveying direction F. Numeral 30 denotes an infrared irradiation device such as an infrared module or an infrared cassette. In the present case, the binder present in the coating 20 is expediently decomposed by means of infrared radiation. Advantageously, the infrared radiation is less energy-intensive than, for example, heating in an oven, since the infrared radiation can already achieve a sufficiently high energy input into the material in a very short time. This reduces the process time. In this way, scrap material in strip form can expediently be heated and stripped of the coating in the throughput. In addition, the efficiency of infrared heating on black surfaces such as those presented here is at a very high level because the emissivity is very high. The processing as a strip material enables the carrier material 10 to be heated evenly and, as a result, a high separation efficiency. Expediently, further methods can be combined here in order to achieve complete detachment of the coating 20, such as B. compressed air irradiation. The coating material obtained from the separation can then be processed and reused. The invention aims in particular at locally thermally decomposing the PVDF binder used in the manufacture of cathodes.

reference list

10

carrier material

20

coating, coating material

30

Device for infrared radiation

f

conveying direction

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 69905134 T2 [0002]
• DE 102009059423 A1 [0002]

Claims (12)

Method for preparing battery electrodes, comprising the steps: - Providing electrode material, the electrode material comprising carrier material (10) which has a coating (20) on one or both sides; - Using infrared radiation to introduce heat into the coating (20) to loosen, in particular to partially or detached, the coating (20). procedure after claim 1 , comprising the step of: - decomposing a binder contained in the coating (20) by introducing the heat. procedure after claim 1 or 2 , the steps include: - supplying electrode material to a quality control; - Supplying the electrode material to a processing plant for processing electrode material identified as defective. Method according to one of the preceding claims, comprising the step: - Introduction of the heat over the entire width of the coating (20). Method according to one of the preceding claims, in which the heat is applied to the carrier material (10) from one side or from two sides. Method according to one of the preceding claims, comprising the step: - Passing through the carrier material (10) under a device (30) for infrared radiation, in particular an infrared module or an infrared cassette. Method according to one of the preceding claims, comprising the step: - Using mechanical and/or pneumatic methods to remove the dissolved coating (20). procedure after claim 7 , comprising the step of: - blasting the electrode material with compressed air to remove the dissolved coating (20). Method according to one of the preceding claims, comprising the step: - Using a suction device to collect the separated coating material (20). Method according to one of the preceding claims, comprising the step: - Processing and reuse of the separated coating material (20). Method according to one of the preceding claims, comprising the step: - Processing and further or reuse of the carrier material (10). Battery electrodes comprising materials obtained by a method according to any one of the preceding claims.

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