Layer structure for a solid-state battery and method for producing such a layer structure

Abstract

The invention relates to a layered structure (1) for a solid-state battery comprising a first electrode (2), a separator (3) arranged thereon in the form of a solid electrolyte, and a current collector (4) on the side of the separator (3) facing away from the first electrode. The layered structure according to the invention is characterized in that the current collector (4) has a coating (6) on its side facing the separator (3), wherein the coating comprises conductive carbon black and at least one metal, and wherein the coating (6) is lithium-free. During the first charging of a solid-state battery with this layered structure (1), a lithium layer (11) is formed in situ between the separator (3) and the current collector (4).

Description

[0001] The invention relates to a layer structure for a solid-state battery according to the type defined in more detail in the preamble of claim 1. The invention also relates to a method for producing such a layer structure.

[0002] Layered structures for solid-state batteries are known from the state of the art. They typically comprise a first electrode, such as the cathode, and a separator based on solid electrolyte compounds, which are usually based on sulfides. This is then followed by a thin lithium foil and a discharge foil arranged on top of it. Usually, all materials are in foil form and are layered on top of one another. This is done, for example, in the form of four individual foils or frequently by combining the cathode and separator, as well as the lithium foil and the discharge foil, in advance, since thin lithium foil is extremely difficult to handle. It tears very easily and exhibits strong plastic flow properties, making it difficult to process.

[0003] EP 3 819 962 A1 describes such a structure and attempts to dispense with a lithium foil. Instead, composite materials are proposed, which contain metallic lithium on the one hand and inorganic compounds such as lithium salts or salt-like substances such as lithium hydroxide on the other.

[0004] However, the cost of production is still very high.

[0005] The object of the present invention is therefore to provide an improved layer structure for a solid-state battery which enables simple and efficient production.

[0006] According to the invention, this object is achieved by a layered structure having the features of claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments of this layered structure emerge from the dependent claims. Claim 5 specifies a method for producing such a layered structure, which also achieves the object. Here, too, advantageous embodiments and further developments emerge from the dependent claims dependent on this method claim.

[0007] The layer structure according to the invention comprises, as is also common in the prior art, a first electrode with a separator arranged thereon in the form of a solid electrolyte and a conductor on the side of the separator facing away from the first electrode, typically the cathode. According to the invention, the conductor has a coating on its side facing the separator, which comprises conductive carbon black and at least one metal other than lithium. The coating itself is thus free of lithium. No lithium is provided in the conductor either.

[0008] Such a structure can now be constructed simply and efficiently without the lithium foil, which is very difficult to handle during production. Eliminating the lithium foil simplifies production considerably. The lithium required for the functionality of the layered structure of the solid-state battery between the separator and the collector is generated in-situ during the first charge of the solid-state battery in the layered structure according to the invention, so that a thin lithium layer forms between the separator and the collector with lithium from the first electrode, i.e., the cathode. This thin layer, which only forms when the solid-state battery is put into operation, requires no additional manufacturing effort.At the same time, the layer is correspondingly thin and forms spontaneously between the boundary layers involved, thus establishing very good electrical contact with both the separator on one side and the conductor on the other. The electrical properties of this connection are far better than would be possible with a lithium foil and the conventional pressing of the individual layers of the layered structure.

[0009] According to a very advantageous development of the layer structure according to the invention, the at least one metal comprises a metal that forms an alloy with lithium. Such metals can, according to a very advantageous development, include, for example, gold, silver, zinc, tin, or the like, although metals such as platinum, palladium, magnesium, aluminum, or bismuth are also possible. The semimetal silicon could also be used here and would be encompassed by the term "metal" within the meaning of the present claims.

[0010] According to a particularly advantageous embodiment of the layer structure according to the invention, it is provided that the first electrode, i.e., the cathode, the separator, and / or the conductor provided with the coating, are in the form of foils. Such foils, preferably when all layers involved are in the form of a single foil, are correspondingly easy to handle and can be fed from rolls, for example, and combined easily and efficiently during production.

[0011] The method according to the invention for producing such a layer structure provides that the first electrode is layered with the separator and the coated conductor, after which the layer arrangement is cut to size and after which a lithium layer is formed in-situ between the separator and the conductor during the first charging of the battery cell thus produced.

[0012] As already mentioned, according to an advantageous development of the method according to the invention, it can be provided that the first electrode, the separator and the arrester are stored as foils on rolls and stacked to form the layer structure.

[0013] The coating with the conductive carbon black and the at least one metal other than lithium can be applied during the manufacturing process, so that before the separator or the combination of first electrode and separator is placed on the arrester, the surface of the arrester facing the separator is provided with the coating. This can be done, for example, using a screen printing process, spraying, doctoring, printing, or the like.

[0014] According to a very advantageous embodiment of the method according to the invention, however, it can also be provided that the coated arrester is kept as a semi-finished product, in order to be able to produce the layered structure simply and efficiently without having to integrate the coating process into the direct production of the layered structure. In this case, it is advisable to coat the arrester accordingly and not the separator, which would also be possible in principle with regard to the production process. However, by applying the coating to the arrester, the risk of chemical interaction between the coating and the separator material during storage and inventory is prevented.

[0015] According to a particularly advantageous embodiment of the method according to the invention, the metallic lithium layer created in-situ during the first charge can be formed as a metallic lithium layer with a layer thickness of less than 100 µm, preferably less than 10 µm. This results in a correspondingly compact structure, in which the full functionality of the solid-state battery can be achieved even with a very thin metallic lithium layer. In larger structures, this ultimately allows for volume savings and correspondingly increases the performance in terms of both the overall volume and the mass of the solid-state battery.

[0016] According to a preferred embodiment of the method according to the invention, the stacking, cutting, and pressing of the layered arrangement takes place sequentially in a manufacturing process, which, according to a very advantageous development of the method according to the invention, can also be followed by the introduction of the pressed layered structure into a housing, the clamping, and the forming of the solid-state battery. Starting from the layered structure according to the invention, the entire battery can thus be manufactured simply and efficiently in a preferably continuous manufacturing process. The housing itself can, for example, be formed from a film bag, thus creating a so-called pouch cell.

[0017] Further advantageous embodiments of the layer structure and of the method also emerge from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0018] Showing: Fig. 1 a first possible variant for stacking the layer structure according to the invention; Fig. 2 a second possible variant for stacking the layer structure according to the invention; Fig. 3 the further processing of the stacked layer structure into a single battery cell; and Fig. 4 a representation analogous to that in the Fig. 1 and Fig. 2 before and after commissioning of the single battery cell.

[0019] In the presentation of the Fig. Figure 1 shows a first possibility for stacking a layer structure according to the invention, designated 1. A cathode foil, designated 2, is fed as the first electrode from rolls not shown here. A separator foil 3 is fed from another roll, also not shown, and a conductor foil 4 is fed from another roll. These are stacked together and form the Fig. 1 Layer structure 1 shown on the right from these films.

[0020] The special feature here is that between the supply of the individual foils 2, 3, 4 from the rolls not shown (shown on the left) and the finished stacked layer structure 1 shown on the left, a coating 6 of the conductor foil 4 is applied, indicated here by a roller 5. This coating 6 contains, in addition to conductive carbon black, metals that can form an alloy with lithium, for example gold, silver, tin, zinc, or other metals known in principle for this purpose, such as magnesium, aluminum, bismuth, or semi-metals such as silicon.

[0021] The applied coating 6 is indicated by dashed lines and can be seen in the stack arrangement 1 between the separator foil 3 and the conductor foil 4.

[0022] In the presentation of the Fig. 2, the cathode foil 2 and the separator foil 3 are supplied as prefabricated semi-finished products, as is the already pre-coated conductor foil 4. These two combinations are then stacked accordingly without the intermediate coating step, since the conductor foil 4 is already provided with the coating 6 as a semi-finished product, and ultimately lead to the same stack arrangement 1 as in the variant according to Fig. 1.

[0023] The two variants can of course also be combined with each other, so that, for example, in the representation of the Fig. 1 could be worked with a semi-finished product made of cathode foil 2 and separator foil 3, or accordingly in the representation in Fig. 2 the coating 6 could only be applied to the conductor foil 4 during production in a corresponding coating station 5.

[0024] Typically, the following occurs, and so it is in the presentation of the Fig. 3, then a cutting or punching of the layer structure 1, which in a continuous production according to the Fig. 1 and Fig. 2 is present as an endless belt. In the representation of the Fig. 3, the layer structure 1 is shown on the left, followed by a punching station designated 7 and subsequent pressing of the individual films 2, 3, 4 and the coating 6 together. This pressing is indicated by the arrows labeled F, which are intended to represent the forces, for example, of a press or a roller assembly pressing the layers. This is followed by packaging in a housing in the station designated 8, for example, the layer structure 1 is packaged in a film bag after pressing, so that a pouch cell is formed. This is followed by clamping in the production station designated 9 and the subsequent forming immediately afterwards and in the same production line. The forming is indicated by station 10.

[0025] In Fig. 4 on the left shows the finished layer structure 1, comprising the cathode 2, the separator 3, the coating 6 and the conductor 4. After the first charging, i.e. after commissioning of the battery cell with the layer structure 1, a lithium layer 11 has formed in the area in which the coating 6 was previously arranged, in addition to this coating or in combination with this coating. This in the Fig.4 shown on the right. This lithium layer 11 is correspondingly thin, for example, with a thickness of a few µm or a few tens of µm, and, due to its in-situ formation in the layer structure 1, has a very low-resistance and mechanically stable electrical contact with both the conductor foil 4 and the separator foil 3, thus achieving a thin lithium layer with ideal electrical and mechanical properties and a very low layer thickness. This enables ideal electrical properties of the layer structure 1 in a solid-state battery. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 819 962 A1

[0003]

Claims

[1] Layer structure (1) for a solid-state battery with a first electrode (2), a separator (3) arranged thereon in the form of a solid electrolyte and a conductor (4) on the side of the separator (3) facing away from the first electrode, characterized by that the arrester (4) has a coating (6) on its side facing the separator (3), wherein the coating comprises conductive carbon black and at least one metal, wherein the coating (6) is free of lithium. [2] Layer structure (1) according to claim 1, characterized by that it is free of a lithium foil. [3] Layer structure (1) according to claim 1 or 2, characterized by that the at least one metal is a metal that alloys with lithium. [4] Layer structure (1) according to claim 1, 2 or 3, characterized by that the first electrode (2), the separator (3) and / or the conductor (4) is in the form of a foil. [5] Method for producing a layer arrangement according to one of claims 1 to 4, wherein the first electrode (2) is layered with the separator (3) and the conductor (4) provided with the coating (6), after which the stack arrangement (1) is cut to size, and after which a lithium layer (11) is automatically formed between the separator (3) and the conductor (4) during the first charging of a solid-state battery comprising the layer arrangement (1). [6] Method according to claim 5, characterized by that at least the first electrode (2), the separator (3) and the conductor (4) are stored as foils on rolls and stacked to form the stack arrangement (1). [7] Method according to claim 5 or 6, characterized by that the arrester foil (4) is stored as a semi-finished product consisting of the actual arrester (4) and the coating (6) and is fed into the process. [8] Method according to one of claims 5, 6 or 7, characterized bythat the metallic lithium layer is formed with a layer thickness of less than 100 µm, preferably less than 10 µm. [9] Method according to one of claims 5 to 8, characterized by that the stacking, cutting and pressing of the stack arrangement (1) takes place one after the other in a manufacturing process. [10] Method according to claim 9, characterized by that in the same manufacturing process, at least one pressed stack arrangement (1) is introduced into a housing, the clamping of the same and the formation of the solid-state battery takes place.

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