Method for producing an electrode separator composite

Abstract

The invention relates to a method for producing an electrode separator composite (ESV), which is a component of an electrode separator stack (1) for a battery cell, and which electrode separator composite (ESV) is formed of at least one electrode layer (E1, E2) and at least one separator layer (S), wherein the method comprises the following steps: a laying process, in which the electrode and separator layers (E1, S, E2) are laid on top of one another; and a joining process, with which an adhesive connection is formed between the electrode and separator layers (E1, S, E2) laid on top of one another. According to the invention, the joining process involves a plasma treatment, in which there is a surface activation of the electrode and / or separator layers (E1, S, E2) using plasma, such that an adhesive connection is provided between the respective joining partners.

Description

[0001] Description

[0002] Process for producing an electrode-separator composite

[0003] The invention relates to a method for producing an electrode-separator composite according to the preamble of claim 1 or claim 9.

[0004] In the production of a lithium-ion cell, an electrode-separator stack must be constructed. This stack consists of a large number of alternating electrodes (anodes or cathodes), each of which is insulated from one another by a separator. Due to the high number of these individual elements and the necessary high positional tolerances, the production of such an electrode-separator stack is particularly critical in terms of cycle time and scrap. One way to make this necessary step productive is to manufacture an electrode-separator assembly (i.e., a unit cell or monocell) and stack such electrode-separator assemblies to form an electrode-separator stack. The electrode-separator assembly thus forms the smallest unit in the electrode-separator stack.

[0005] A generic method for producing an electrode-separator composite comprises a laying process in which the electrode and separator layers are placed on top of one another, and a joining process by means of which an adhesive connection is formed between the electrode and separator layers placed on top of one another.

[0006] The joining process is currently implemented as a lamination process. In this process, the individual elements of the electrode-separator assembly (e.g., separator / anode / separator / cathode) are bonded together using pressure and temperature. Currently, this is achieved by depositing individual anodes onto a continuous separator film and then covering them with another separator film. Individual cathodes are then deposited onto this separator / anode / separator assembly.

[0007] The special feature of the above lamination process is that separators are generally pre-coated with an adhesion-promoting layer on at least one side. The coating is usually made of PVDF, which melts during the lamination process, thus ensuring the adhesion of the individual layers to each other. The electrode-separator composites thus produced are then used to create the electrode-separator stack in a subsequent stacking process.

[0008] The use of separators with adhesion-promoting layers results in considerable costs in the production and use of such insulation layers. Furthermore, the joining process can only be carried out under the simultaneous influence of both temperature and pressure. Furthermore, the process principle limits the productivity of the lamination process using, for example, hot presses, double-belt presses, or similar processes, as a temperature-pressure regime must be maintained. Furthermore, the lamination process has low energy efficiency, as the energy used in the lamination process is lost as waste heat. Heat loads in machines and systems for battery cell production are considered critical due to the environmental requirements (defined air conditioning).

[0009] From DE 102020 007 718 A1 a device for producing electrodes for lithium-ion batteries is known.

[0010] The object of the invention is to provide a method for manufacturing an electrode-separator assembly for a battery cell, which is simpler in terms of process technology than the prior art.

[0011] The object is solved by the features of claim 1 or claim 9. Preferred embodiments are disclosed in the subclaims.

[0012] The invention relates to a method for producing an electrode-separator assembly that is a component of an electrode-separator stack for a lithium-ion battery cell. The electrode-separator assembly forms the smallest unit of the electrode-separator stack and is also known as a monocell or unit cell. The electrode-separator assembly according to the invention consists, in a conventional manner, of superimposed electrode layers with at least one separator layer arranged between them. Generally, the electrode-separator assembly is produced using the following process steps: In a laying process, the electrode and separator layers are placed on top of one another. In a joining process, a sufficiently strong adhesive bond (adhesion) is formed between the superimposed electrode and separator layers.According to the characterizing part of patent claim 1, this joining process is no longer implemented as a lamination process with corresponding heat and pressure application. Rather, the joining process involves a plasma treatment in which the surface of the electrode and / or separator layers is activated by plasma. The plasma treatment provides an enhanced chemical bond, preferably through covalent bonds, which ensure sufficiently strong adhesion between the respective joining partners.

[0013] In a simple technical implementation, plasma treatment precedes the deposition process. In this case, the plasma-pretreated electrode and / or separator layers can be superimposed during the deposition process, forming covalent bonds between adjacent layers.

[0014] With regard to large-scale production, it is preferred if the process for manufacturing the electrode-separator composite is designed as a continuous process. In this case, the electrode and separator layers are provided as continuous web material and are guided together through the nip of a pressure roller pair, forming a continuous layer composite. This is then cut to length into individual electrode-separator composites in a subsequent cutting process.

[0015] In the above process configuration, it is preferred if at least one plasma source is arranged at the roller gap inlet of the pressure roller pair, by means of which the surface activation of the electrode and / or separator layers can be carried out.

[0016] After the cutting process, a stacking process is commonly performed in which the individual electrode-separator assemblies are stacked to form an electrode-separator stack. In the current state of the art, this stack must be stabilized in a further process (e.g., a taping process) to ensure easy handling of the electrode-separator stack for the subsequent process sequence. Alternatively and / or in addition to the plasma treatment of the individual electrode and / or separator layers described above, a further plasma treatment can be provided. This occurs prior to the stacking process and causes surface activation of the respective electrode-separator assemblies using plasma. This provides increased adhesive bonding through covalent bonds between stacked electrode-separator assemblies.According to the invention, surface activation can be carried out by plasma treatment on one or both sides of the respective layer or the respective electrode-separator composite. Depending on the process, surface activation can be carried out either continuously or in sections.

[0017] A key advantage of the plasma treatment according to the invention is that, unlike the conventional lamination process, it can be carried out at room temperature, i.e., without the influence of a high process temperature. This generates decisive advantages in terms of productivity and energy efficiency. Furthermore, more cost-effective, i.e., thermally unstable, starting materials can be used for the product.

[0018] During plasma treatment, a gas discharge occurs in a gas atmosphere in a well-known manner. The process gas flows past a discharge path, is excited there, and is converted into the plasma state. The plasma thus formed can then be directed through a plasma nozzle onto the surface of the electrode and / or separator layer to be treated. To enhance the bond, it is preferred to add additional additives (i.e., precursors) to the process gas. Examples of such precursors include nitrogen compounds or silate compounds. In another embodiment, UV-activated joining additives can also be added if necessary.

[0019] Overall, the invention achieves the following advantages, listed in bullet points: the joining process is extremely energy-efficient; cost advantages for the starting materials used (elimination of adhesion-promoting layers of the separator); significantly lower thermal loads on the joining partners; integrated pretreatment and joining process;

[0020] The properties of the joint can be adjusted through the use of precursors; any cell structure can be implemented; continuous (R2R) and discontinuous joining (R2S, stacking) is possible.

[0021] An exemplary embodiment of the invention is described below with reference to the attached figure. The figure shows an exemplary system diagram for producing an electrode separator stack 1. This can be installed in a cell housing (not shown) of a lithium-ion battery cell. The electrode separator stack 1 consists of a plurality of electrode separator assemblies (ESV) stacked one above the other. Each electrode separator assemblie (ESV) is composed of a lower separator layer S, a middle cathode layer K, a middle separator layer S, and an upper anode layer A.

[0022] It should be emphasized that the invention is not limited to the electrode-separator assembly ESV indicated in the figure. Instead, the electrode layers and the separator layers in the electrode-separator assembly ESV can be stacked in any other way. For example, the electrode-separator assembly ESV can be constructed from exactly one electrode layer and exactly one separator layer S. Alternatively, the electrode-separator assembly ESV can be constructed from a separator layer S, an electrode (A or K), and a separator layer S, viewed in the stacking direction. Furthermore, the electrode-separator assembly ESV can be constructed from a separator layer S, a first electrode (A or K), a separator layer S, and a second, opposite-polar electrode (K or A), viewed in the stacking direction. Mixed forms are also conceivable.

[0023] According to the figure, for the production of the electrode-separator composite ESV, the two separator layers S as well as the two anode and cathode layers A, K are initially provided as continuous foil webs 3, 5, 7. The total of four continuous foil webs are guided in a production direction F through a nip of a pressure roller pair 11. With the help of the pressure roller pair 11, a continuous laying process takes place, namely with the formation of an endless layer composite 13 at the nip exit of the pressure roller pair 11. The two separator foil webs 3 are guided through the nip without a preceding cutting process, i.e. as continuous foil webs, while the two anode foil webs 5 and the cathode foil web 7 are separated into individual layers in upstream cutting stations 15.Accordingly, the separated anode layers A are deposited on the underside of the middle separator foil web 3, while the separated cathode layers K are deposited on its upper side. The anode layers A are also covered with the lower separator foil web 3.

[0024] The core of the invention is that a plasma treatment station with plasma sources 17 is arranged upstream of the pressure roller pair 11. These are arranged directly at the nip inlet of the pressure roller pair 11. The plasma sources 17 activate the surfaces of the electrode and / or separator foil webs 3, 5, 7. In this way, a sufficiently strong adhesive connection is provided by covalent bonds between the respective layers S, A, S, K, which, after passing through the nip, provides sufficiently strong adhesion in the formed endless layer composite 13. The plasma treatment is carried out at approximately room temperature. In common practice, plasma treatment involves a gas discharge in a gas atmosphere. The process gas flows past a discharge path, is excited there, and converted into a plasma state.The plasma thus formed is applied to the surface of the respective electrode and / or separator foil web 3, 5, 7 through a plasma nozzle 19 during the further course of the process. Auxiliary materials are preferably added to the process gas to enhance the bonding in the continuous layer composite 13.

[0025] In the figure, a cutting station 21 is arranged downstream of the pressure roller pair 11, in which the endless layer composite 13 is cut to length into individual electrode-separator composites (ESV). As indicated in the figure, the electrode-separator composites (ESV) can, alternatively or in addition to the first plasma treatment, be fed to a further plasma treatment station 23, in which surface activation of the respective electrode-separator composite (ESV) also takes place with the aid of plasma sources 17. This plasma treatment provides increased adhesive bonding through covalent bonds between the electrode-separator composites (ESV). The electrode-separator composites (ESV) are then stacked one on top of the other in a stacking station 25 to form the electrode-separator stack 1.

[0026] Especially when using a plasma treatment in the plasma treatment station 23, it is relevant that the electrode-separator assembly ESV is constructed from an anode layer A, a separator layer S, a cathode layer K, a separator layer S and an anode layer A, viewed in the stacking direction.

[0027] List of reference symbols

[0028] 1 electrode separator stack

[0029] 3 separator film webs

[0030] 5 Anode foil web

[0031] 7 Cathode foil track

[0032] 11 pair of pressure rollers

[0033] 13 endless layer composite

[0034] 15 cutting stations

[0035] 17 Plasma source

[0036] 19 Plasma nozzle

[0037] 21 Cutting station

[0038] 23 Plasma treatment station

[0039] 25 stacking stations

[0040] A anode layer

[0041] S separator layer

[0042] K Cathode layer

[0043] ESV electrode separator composite

[0044] F Production direction

[0045] E1 , E2 general designation for electrode layers, ie anode layer and cathode layer

Claims

Claims: Method for producing an electrode-separator assembly (ESV) that is part of an electrode-separator stack (1) for a battery cell, which electrode-separator assembly (ESV) is composed of at least one electrode layer and at least one separator layer (S), wherein the method comprises the following process steps: - a laying process in which at least one electrode (E1, E2) and one separator layer (S) are placed on top of each other; and - A joining process by means of which an adhesive bond is formed between at least one electrode layer (E1, E2) and a separator layer S, characterized in that the joining process includes a plasma treatment in which the surface of at least one electrode (E1, E2) and / or separator layer (S) is activated by means of plasma, so that an enhanced adhesive bond, preferably by covalent bonds, is provided between the respective joining partners. The method according to claim 1, characterized in that the plasma treatment is carried out before the laying process, so that in the laying process the plasma-pretreated electrode and / or separator layers (E, S) are laid on top of each other.A method according to claim 1 or 2, characterized in that the laying process is a continuous process in which the still separate electrode and separator layers (E, S) are guided together as continuous film webs through a roller gap of a pressure roller pair (11), in particular forming a continuous layer composite (13) which is cut to length in a subsequent cutting process to form individual electrode-separator composites (ESV). A method according to claim 3, characterized in that at least one plasma source (17) is located upstream of the pressure area (which may also be a conveyor belt instead of a roller) (11) at the input side, by means of which the surface activation of the electrode and / or separator continuous webs (3, 5, 7) is carried out. A method according to claim 3 or 4, characterized in that a stacking process takes place after the cutting process in which the electrode-separator composites (ESV) are stacked to form an electrode-separator stack (1), and in particular, to stabilize the electrode-separator stack (1), a further plasma treatment is performed prior to the stacking process, in which the surface of the respective electrode-separator assembly (ESV) is activated by plasma, so that an adhesive bond is provided by covalent bonds between stacked electrode-separator assemblies (ESV). A method according to one of the preceding claims, characterized in that the surface activation by plasma treatment can be carried out on one or both sides of a separator layer (S) and / or on an electrode layer (A, K), and / or that the surface activation can be carried out continuously or section by section.A method according to one of the preceding claims, characterized in that the plasma treatment is carried out at room temperature, and / or that a gas discharge takes place in a gas atmosphere during the plasma treatment, wherein the process gas flows past a discharge section, is excited there and is converted into the plasma state, and that the plasma thus formed is subsequently directed through a plasma nozzle (19) onto the surface of the electrode (E1, E2) and / or separator layer (S) to be treated, and / or that additives are added to the process gas with the help of which the adhesive bond between the joining partners is increased.A method according to one of the preceding claims, characterized in that the electrode-separator assembly (ESV), viewed in the stacking direction, is composed of a separator layer (S), an electrode (E1, E2), and a separator layer (S), or that the electrode-separator assembly (ESV), viewed in the stacking direction, is composed of a separator layer (S), a first electrode (E1), a separator layer (S), and a second, oppositely polarized electrode (E2). A method for producing an electrode-separator assembly (ESV) that is a component of an electrode-separator stack (1) for a battery cell, which electrode-separator assembly (ESV) is composed of at least one electrode layer and at least one separator layer (S), wherein the method comprises a stacking process step in which a plurality of electrode-separator assemblies (ESV) are stacked to form the electrode-separator stack (1), characterized in that. The stacking process step is preceded by a plasma treatment in which the surface of the electrode-separator composites (ESCs) is activated by plasma, resulting in an increased adhesive bond, preferably through covalent bonds, between the respective joining partners. The method according to claim 9 is characterized in that the electrode-separator stack (1) produced by plasma treatment terminates at both stack ends with an anode, and / or that, in particular, the electrode-separator composite (ESC), viewed in the stack direction, is composed of an anode layer, a separator layer (S), a cathode layer, a separator layer (S), and an anode layer.

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