Manufacturing method of electrode / separator composite

Abstract

The invention relates to a method for manufacturing an electrode / separator composite ESV, which is a component of an electrode / separator laminate 1 for a battery cell, comprising at least one electrode layer E1, E2 and at least one separator layer S, the method comprising the steps of a superposition process in which the electrode layers E1, E2 and the separator layer S are superimposed on one another, and a joining process in which an adhesive bond is formed between these superimposed electrode layers E1, E2 and the separator layer S. According to the invention, this joining process comprises a plasma treatment in which the surface of the electrode layers E1, E2 and / or the separator layer S is activated by means of plasma, so that an adhesive bond is provided between the respective joining partners.

Description

[Technical field]

[0001] The present invention relates to a method for producing an electrode / separator composite according to the preamble of claim 1 or claim 9. [Background technology]

[0002] When manufacturing lithium-ion cells, one must build an electrode-separator stack, essentially consisting of a number of interleaved electrodes (anodes or cathodes), each insulated from the other by a separator. The manufacture of such electrode / separator stacks is particularly demanding in terms of cycle time and rejects due to the large number of their individual elements and the need for high positioning tolerances. An efficient way to accomplish these required steps is to manufacture composites of electrodes and separators (i.e., unit cells or monocells) and stack such electrode / separator composites into an electrode / separator stack. Thus, the electrode / separator composite constitutes the smallest unit in the electrode / separator stack.

[0003] The method of manufacturing such types of electrode / separator composites includes a lamination process in which electrode and separator layers are laminated together, and a bonding process in which an adhesive bond is formed between the laminated electrode and separator layers.

[0004] In the prior art, the bonding process is realized as a lamination process, where the individual elements of the electrode / separator composite (e.g. separator / anode / separator / cathode) are bonded together by pressure and temperature. Currently, this is done by depositing an individual anode on a continuous separator film, which is then covered with another separator film. On top of the separator / anode / separator composite, a separate cathode is then deposited.

[0005] The lamination process described above is characterized by the use of separators that are generally pre-coated on at least one side with an adhesion-promoting layer. This coating usually consists of PVDF, which melts in the framework of the lamination process, thus ensuring adhesion of the individual layers to each other. In a subsequent stacking process, the electrode / separator laminate is produced from the electrode / separator composite thus produced.

[0006] The use of a separator provided with an adhesion-promoting layer results in significant costs for the manufacture and application of such an insulating layer. Moreover, the bonding process can only be carried out under the simultaneous action of both temperature and pressure. Furthermore, the productivity of the lamination process, for example using a hot press, a double belt press or an equivalent process, is limited due to the process format, since the temperature and pressure regimes must be maintained. Furthermore, the energy efficiency of the lamination process is low, since the energy consumed in the lamination process is lost as waste heat. Due to environmental requirements (defined air conditioning conditions), the heat load on the machines and equipment for manufacturing the battery cells must be considered as significant.

[0007] From US Pat. No. 5,399,633 an apparatus for producing electrodes for lithium-ion batteries is known. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German Patent Publication No. 102020007718 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide a method for producing an electrode / separator composite for a battery cell, which is easier to construct in terms of process technology compared to the prior art. [Means for solving the problem]

[0010] This problem is solved by the features of claim 1 or claim 9. Advantageous embodiments are disclosed in the dependent claims.

[0011] The present invention relates to a method for producing an electrode / separator composite, which is a component of an electrode / separator laminate for a lithium-ion battery cell. This electrode / separator composite constitutes the smallest unit of the electrode / separator laminate and is also known as a monocell or unit cell. The electrode / separator composite according to the invention is composed of overlapping electrode layers with at least one separator layer arranged between them in a manner known per se. In general, this electrode / separator composite is produced by the following process steps, such that in the overlapping process the electrode and separator layers are superimposed on each other. In the bonding process a sufficiently large adhesive bond (cohesion) is formed between the overlapping electrode and separator layers. According to the characterizing part of claim 1, this bonding process is no longer realized as a lamination process with corresponding application of heat and pressure. Rather, this bonding process comprises a plasma treatment for activation of the surfaces of the electrode layers and / or the separator layers with plasma. This plasma treatment is used to provide a strengthened chemical adhesive bond, advantageously by covalent bonds, which causes a sufficiently large adhesion between the respective bonding partners.

[0012] In a technically easy realization, this plasma treatment is carried out before the superposition process, in which case the electrode layers and / or separator layers pretreated with plasma can be superposed on one another in such a way that covalent bonds form between adjacent layers.

[0013] For mass production, it is advantageous to configure this method for manufacturing the electrode / separator composite as a continuous process. In this case, the electrode and separator layers are provided as an endless belt member and are guided together through the roller nip of a pair of pressure rollers, in particular in such a way as to form an endless layer composite. This composite is shortened to individual electrode / separator composites in a downstream cutting process.

[0014] In the combination of the above processes, it is advantageous to arrange at least one plasma source at the entrance to the roller nip of the pair of pressure rollers, by means of which activation of the surfaces of the electrode layer and / or the separator layer can be carried out.

[0015] In common practice, after the cutting process, a lamination process is carried out in which the individual electrode / separator composites are stacked as an electrode / separator laminate. In the prior art, this laminate must be stabilized by another process (e.g. a taping process) to ensure easy handling of the electrode / separator laminate for further process sequences. Instead of and / or in addition to the plasma treatment of the individual electrode and / or separator layers already mentioned above, a further plasma treatment can be provided. This is carried out before the lamination process and involves activation of the surface of each electrode / separator composite with plasma. This provides a strengthened adhesive bond by covalent bonds between the electrode / separator composites stacked on top of each other.

[0016] In the present invention, this surface activation can be performed by plasma treatment of one or both sides of each layer or each electrode / separator composite. This surface activation can be performed continuously or intermittently depending on the process control.

[0017] A major advantage of the plasma treatment according to the invention is that, unlike conventional lamination processes, it can be carried out at room temperature, i.e. without the application of high process temperatures, which produces crucial 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] In this plasma treatment, in a manner known per se, a gas discharge is carried out in a gas atmosphere, in which a process gas is made to flow through a discharge section, where it is excited and transferred into a plasma state. The plasma thus generated can be delivered to the surface of the electrode layer and / or separator layer to be treated through a plasma nozzle during further process progress. In order to increase the adhesive bond, it is advantageous to add additional auxiliary materials (i.e. precursors) to the process gas. For example, such precursors can be nitrogen compounds or silicate compounds. In another embodiment, a bonding auxiliary material that can possibly be activated by UV can also be added.

[0019] Overall, with the present invention the following key advantages are achieved: a very energy-efficient bonding process, cost advantages due to the use of starting materials (omission of the adhesion-promoting layer of the separator), a significant reduction in the thermal load on the bonding partners, integration of the pre-treatment and bonding processes, adjustable properties of the bonding bond due to the use of precursors, the realization of any cell structure, continuous (R2R) and discontinuous bonding (R2S, stacking) possible.

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. [Brief description of the drawings]

[0021] [Figure 1] Schematic diagram of an example of an equipment for producing an electrode / separator laminate 1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The electrode / separator laminate 1 can be incorporated into a cell housing (not shown) of a lithium-ion battery cell. The electrode / separator laminate 1 is composed of a number of electrode / separator composites ESV stacked on top of one another. Each electrode / separator composite 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.

[0023] It should be emphasized that the present invention is not limited to the electrode / separator composite ESV shown in the drawings. Instead, the electrode layers and the separator layers can be stacked in any other manner in the electrode / separator composite ESV. For example, the electrode / separator composite ESV can be composed of exactly one electrode layer and exactly one separator layer S. Alternatively, the electrode / separator composite ESV can be composed of one separator layer S, one electrode (A or K) and one separator layer S, as viewed in the stacking direction. Furthermore, the electrode / separator composite ESV can be composed of one separator layer S, a first electrode (A or K), one separator layer S and a second electrode of opposite polarity (K or A), as viewed in the stacking direction. Furthermore, mixed shapes of these are also conceivable.

[0024] In this figure, to produce an electrode / separator composite ESV, firstly two separator layers S and two anode layers A and a cathode layer K are provided as endless thin film tapes 3, 5, 7. A total of four of these endless thin film tapes are guided in the production direction F through the nip of a pressure roller pair 11. With this pressure roller pair 11, a continuous overlapping process is carried out, in particular in such a way that an endless layer composite 13 is produced at the outlet of the nip of the pressure roller pair 11. In this case, the two separator thin film tapes 3 are guided through the nip without a preceding cutting process, i.e. as continuous thin film tapes, while the two anode thin film tapes 5 and the cathode thin film tape 7 are separated into individual layers in a cutting station 15 connected upstream. Correspondingly, the separated anode layer A is placed below the intermediate separator thin film tape 3, while the separated cathode layer K is placed above it. Furthermore, these anode layers A overlap the separator thin film tape 3 underneath.

[0025] The essence of the invention is that a plasma treatment station with plasma sources 17 is placed before the pressure roller pair 11. These are arranged close to the entrance of the nip of the pressure roller pair 11. With these plasma sources 17, activation of the surfaces of the electrode and / or separator thin film tapes 3, 5, 7 is carried out. In this way, a sufficiently large adhesive bond is provided by covalent bonds between the layers S, A, S, K, which provides a sufficiently large adhesion in the endless layer composite 13 produced after passing through the nip.

[0026] The plasma treatment is carried out at approximately room temperature. In common practice, a gas discharge in a gas atmosphere is carried out in this plasma treatment. In this case, a process gas flows through a discharge section, where it is excited and passes into a plasma state. The plasma thus created is applied during further process steps through a plasma nozzle 19 to the surface of the respective electrode and / or separator thin film tape 3, 5, 7. Advantageously, auxiliary substances are added to the process gas, with which the adhesive bond of the endless layer composite 13 is strengthened.

[0027] In this figure, the pair of pressure rollers 11 is followed by a cutting station 21, in which the endless layer composite 13 is shortened into individual electrode / separator composites ESV. As shown, instead of or in addition to the first plasma treatment, the electrode / separator composites ESV can be fed to another plasma treatment station 23, in which activation of the surface of each electrode / separator composite ESV is carried out, also using a plasma source 17. This plasma treatment provides a strengthened adhesive bond by covalent bonds between the electrode / separator composites ESV. The electrode / separator composites ESV are then stacked on top of each other in a stacking station 25 to form an electrode / separator stack 1.

[0028] In particular, when adopting the plasma treatment performed in this plasma treatment station 23, it is relevant that the electrode / separator composite ESV is composed of an anode layer A, a separator layer S, a cathode layer K, a separator layer S and an anode layer A when viewed in the stacking direction. [Explanation of symbols]

[0029] 1. Electrode / separator laminate 3. Separator thin film tape 5 Anode Thin Film Tape 7 Cathode Thin Film Tape 11 Pressure roller pair 13 Endless Layer Complex 15 Cutting Station 17 Plasma Source 19 Plasma Nozzle 21 Cutting Station 23 Plasma Treatment Station 25 Lamination Station A Anode layer S separator layer K cathode layer ESV electrode / separator composite F Manufacturing direction E1, E2 General designations for electrode layers, i.e. anode and cathode layers

Claims

1. A method for manufacturing an electrode / separator composite (ESV) which is a component of an electrode / separator laminate (1) for a battery cell, the electrode / separator composite (ESV) being composed of at least one electrode layer and at least one separator layer (S), the method comprising: a step of a stacking process in which at least one electrode (E1, E2) and one separator layer (S) are stacked on top of each other; a step of a bonding process for forming an adhesive bond between at least one electrode layer (E1, E2) and a separator layer (S); In a method having the following structure: A method characterized in that the bonding process comprises a plasma treatment for activation of the surface of at least one electrode layer (E1, E2) and / or separator layer (S) with plasma, so that a strengthened adhesive bond is provided between the respective bonding partners, advantageously by covalent bonds.

2. 10. The method of claim 1 , The method according to claim 1, characterized in that the plasma treatment is carried out before a superposition process, so that in the superposition process, electrode layers (E) and / or separator layers (S) pretreated with plasma are superposed on one another.

3. The method according to claim 1 or 2, 10. A method according to claim 1, wherein the superposition process is a continuous process in which the electrode layer (E) and the separator layer (S), still separate from one another, are guided together as an endless thin-film tape through the nip of a pressure roller pair (11), in particular in such a way as to create an endless layer composite (13), which is shortened in a subsequent cutting process to individual electrode / separator composites (ESV).

4. 4. The method of claim 3, 2. A method according to claim 1, wherein at least one plasma source (17) is arranged before the pressing area (11) on the input side (which can also be a belt conveyor instead of a roller), by means of which activation of the surfaces of the electrode and / or separator endless tapes (3, 5, 7) is carried out.

5. The method according to claim 3 or 4, After the cutting process, a lamination process is performed in which the electrode / separator composites (ESVs) are stacked as an electrode / separator laminate (1); In particular, in order to stabilize the electrode / separator laminate (1), a separate plasma treatment is carried out prior to the lamination process, which involves activation of the surface of each electrode / separator composite (ESV) with plasma, thereby providing covalent adhesive bonds between the overlapping electrode / separator composites (ESV).

6. The method according to any one of claims 1 to 5, Said surface activation can be carried out by plasma treatment of one or both sides of the separator layer (S) and / or the electrode layers (A, K); and wherein the activation of the surface can be performed continuously or intermittently.

7. The method according to any one of claims 1 to 6, The plasma treatment is carried out at room temperature; and in the plasma treatment, a gas discharge is carried out in a gas atmosphere, and the process gas flows through a discharge section, where it is excited and transferred to a plasma state; the plasma thus produced is delivered during the further progress of the process through a plasma nozzle (19) to the surface of the electrode layer (E1, E2) and / or separator layer (S) to be treated, and auxiliary substances are added to the process gas, by means of which the adhesive bond between the joining partners is strengthened.

8. The method according to any one of claims 1 to 7, The electrode / separator composite (ESV) is composed of a separator layer (S), electrodes (E1, E2) and a separator layer (S) when viewed in the stacking direction, or The method is characterized in that the electrode / separator composite (ESV) is composed of, in the stacking direction, a separator layer (S), a first electrode (E1), a separator layer (S), and a second electrode of opposite polarity (E2).

9. A method for manufacturing an electrode / separator composite (ESV) which is a component of an electrode / separator laminate (1) for a battery cell, the electrode / separator composite (ESV) being composed of at least one electrode layer and at least one separator layer (S), the method comprising a lamination process step of stacking a plurality of electrode / separator composites (ESV) as the electrode / separator laminate (1), comprising: A method characterized in that, prior to this lamination process step, a plasma treatment is carried out, which involves activation of the surface of the electrode / separator composite (ESV) with plasma, as a result of which a reinforced adhesive bond is provided between the respective bonding partners, advantageously by covalent bonds.

10. 10. The method of claim 9, The electrode / separator laminate (1) produced by the plasma treatment is terminated at both ends of the laminate with an anode, In particular, the electrode / separator composite (ESV) is composed of, in the stacking direction, an anode layer, a separator layer (S), a cathode layer, a separator layer (S) and an anode layer.

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