Method for manufacturing a battery cell, use of a cleaning agent, and a battery cell

Abstract

The invention relates to a method for producing a battery cell (18), comprising at least the following steps: a) continuously supplying at least a first material (5) and a second material (2); b) aggregating the first material (5) and the second material (2) into sub-stacks (6); c) arranging a plurality of sub-stacks (6) into a battery stack (14); wherein during at least one of steps a), b) or c) a step d) is performed, which comprises cleaning at least the first material (5). Furthermore, a use of a cleaning agent for producing a lithium-ion battery cell and a battery cell are proposed.

Description

Technical Field

[0001] The invention relates to a method for producing a battery cell, to the use of a cleaning agent in the context of production, and to a battery cell itself, in particular a battery cell for a motor vehicle. Background Art

[0002] In general, a battery cell has at least three layers. These are the negative electrode, the positive electrode and the separator. The separator has the task of separating the electrodes electrically and mechanically from one another. The quality of the layers used is particularly important in the case of lithium-ion batteries and lithium polymer batteries. Lithium-ion batteries react sensitively to contamination. For example, LiOH (lithium hydroxide) causes a demonstrable and significant deterioration in the performance and life of the battery cell.

[0003] In the case of lithium-ion cells, the cathode, ie the negative electrode, is therefore usually designed as a so-called insertion electrode. This means that the cathode contains the active material in its interior in such a way that it is ready for electrochemical exchange with the electrolyte during charging and discharging of the cell. In the case of lithium-ion cells and lithium polymer cells, the anode is generally a graphite-based insertion electrode, in the interior of which the metal ions are accommodated during charging of the cell.

[0004] In particular, in the case of nickel-rich cathodes, contaminants may occur, for example, in the form of LiOH, Li2CO3, NiCO3 and Ni(OH)2, which are formed when the cathode active material is exposed to water before final sealing of the cell. Here, it is sufficient that few traces of water come into contact with the cathode.

[0005] The contaminants listed above contribute to the side reaction of the cathode active material with the electrolyte. In the event of a side reaction, the electrolyte may be decomposed and electrolyte substitution products may be formed in the battery. The electrolyte substitution products formed may cause worse performance and life of the battery.

[0006] Attempts to reduce the proportion of nickel in the active material of the cathode always have the disadvantage that the energy density of the cell is reduced.

[0007] Another approach is to treat the nickel-rich cathode in a drying chamber in order to avoid water exposure of the cathode in each process step. However, this is a very cost-intensive approach.

[0008] A method for producing an electrochemical cell is known from EP 1 665 447 B1, in which hydroxide ions are removed from the surface of an electrode for optimization. For this purpose, a cleaning agent containing a first cleaning component that reacts with hydroxide ions is brought into contact with the electrode in such a way that the hydroxide ions to which it is attached are released from the electrode surface by reaction with the first cleaning component. Subsequently, the cleaning agent or components of the reaction products that may interfere with the function of the cell must then be removed from the electrode. The known method can achieve the necessary cleaning effect, but it is complex, slow and cost-intensive in practical application. Summary of the invention

[0009] The object of the present invention is therefore to at least partially solve the problems arising from the prior art. In particular, a method for producing a battery cell is to be specified, with which rapid and cost-effective production is possible and the properties of the battery cell produced in this way are not negatively affected by contaminants.

[0010] The method, use and battery cell according to the invention contribute to the achievement of these objects. The features listed separately in the invention can be combined with one another in a technically meaningful manner and can be supplemented by the actual conditions explained in the description and / or by details according to the drawings, wherein further embodiments of the invention are indicated.

[0011] A method for manufacturing a battery cell is currently proposed, which comprises at least the following steps:

[0012] a) continuously supplying at least a first material and a second material;

[0013] b) combining the first material and the second material into a partial pile;

[0014] c) arranging the plurality of sub-stacks into a battery stack;

[0015] Therein, step d) comprising cleaning at least the first material is performed during at least one of steps a), b) or c).

[0016] For cost-effective production, it is important to be able to produce a high number of battery cells in a short time unit. For this purpose, it is necessary to rationalize and, in particular, automate the production process. The goal is to create a production process that is as continuous as possible, in such a way that the materials required for the battery cells are supplied as continuously as possible. Continuous in this context means that the materials are supplied step by step, either at a substantially constant speed or at a shorter cycle time. In this case, the cycle time is then in the range of a few seconds up to 5 minutes.

[0017] After the first and second materials have been supplied continuously in step a), the first and second materials can be aggregated into a sub-stack in step b). Preferably, more than two materials can also be aggregated here. For example, the aggregation of three, four or five and more (different) materials is conceivable. In this way, for example, sub-stacks can be produced in which cathode, separator and anode are combined with each other in a three-layer arrangement. A four-layer arrangement can, for example, have a combination of separator, anode, separator and cathode. Finally, a five-layer arrangement can also be realized in which separator, anode, separator, cathode and yet another separator are combined into a sub-stack.

[0018] In step c), the sub-stacks thus produced are arranged one on top of the other to form a battery stack. In order to obtain a battery cell with long-lasting high performance, it is provided that at least the first material (i.e. at least one of the materials used, in particular the material of the cathode) is cleaned completely or as much as possible or approximately completely. It is particularly advantageous here that the entire execution (Abarbeitung) of the method steps is automatically implemented. In this case, the cleaning of at least the first material can also be preferably achieved in an automatic manner. The steps of the current method can therefore be performed in the case of a reasonable and cost-effective automatic manufacturing method. This allows the manufacture of battery cells that are cost-effective on the one hand and do not have performance losses due to contaminants on the other hand. In particular, the entire and at least a single-stage cleaning process in the cleaning device can be provided and implemented as an integral part of the manufacturing method. Alternatively, a multi-stage cleaning process can also be implemented in this way.

[0019] In particular, the presence of water during the production process of the battery cells leads to the formation of contaminants which were then still removed before the production of the battery cells. The necessary high expenditure for preventing the presence of water during the production process of the battery cells can thus be reduced or eliminated in the future. As an alternative, the temporary formation of contaminants is at least partially tolerated so that any contaminants that may have formed are then also removed before the production of the battery cells.

[0020] Steps a) to d) can be performed at least once in the order a), b), c) and d) described here. It is possible that these steps are performed with different frequencies and / or at least partially overlapping in time, wherein the execution of the steps can also take place at different locations if necessary. Step d) can be performed once or also multiple times at different times. In particular, step d) can also be performed simultaneously with one or more of the other steps a) to c).

[0021] In particular, it can be provided that the first material comprises the active material for the cathode (cathode material). This indicates that contamination occurs in particular at the cathode, which negatively affects the performance of the battery cell, for example with regard to the charge capacity and possible charge or discharge current. This can be reduced or avoided or eliminated by the proposed electrode washing at this point in the battery production process.

[0022] Furthermore, it can be provided that the second material comprises a separator medium (separator material) and the fourth material comprises an active material for the anode (anode material). It is thus possible to select the layer structure of the sub-stacks in such a way that they then only have to be arranged one above the other in the desired number and sequence to form the desired cell stack. In the case of a layer structure with more than three layers, it may also make sense to use a third material which then also comprises a separator medium (separator material).

[0023] Preferably, in step d), the contaminants typical for the respective material are also removed. It is indicated that different materials also tend to form different contaminants. This depends on different factors. In the case of cleaning carried out in step d), the cleaning process is then each adapted to the respective different contaminants in order to achieve an optimal cleaning effect.

[0024] In particular, the individual materials can be cleaned in a cleaning tank in step d). If necessary, a subsequent process, preferably carried out under drying conditions, can be connected thereto. This can be, for example, a sequence of cleaning tanks, physical treatments or drying processes.

[0025] As an alternative to the cleaning tank of individual or partially connected materials, in particular the battery stack can be additionally surrounded by a housing in step c) and step d) can be carried out in this housing. This can prevent the battery stack from coming into contact with moisture or other materials again after cleaning. It is advantageous for this to be carried out directly or at least immediately after cleaning, when the housing and the battery stack are filled with electrolyte. The same applies to the subsequent sealing of the battery cells. The shorter the duration between cleaning and filling or sealing of the housing of the battery cells, the less foreign matter and in particular moisture can come into contact with and react with the battery stack in the housing.

[0026] In particular, it is advantageous here if, in step d), a cathode washing is provided, since the cathode is most susceptible to contamination.

[0027] In particular, it can also be provided that drying is carried out in a step e) which is arranged downstream of step d). As a result, the necessary duration for drying can be reduced and the production speed of the battery cell production can be increased. Drying can be carried out, for example, by means of compressed air, hot air or another heat input. In particular, it should be ensured that the drying is carried out in a short time in order to ensure automated production of the battery cells at a high production speed.

[0028] It is also particularly advantageous if, in step d), at least one of the following components is eliminated: LiOH, Li 2 CO 3 , NiCO 3 and Ni(OH) 2 . These contaminants occur particularly frequently in lithium-ion cells.

[0029] Furthermore, it can be advantageously provided that in step d) a cleaning agent is used which contains at least ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), butylene carbonate, dipropyl carbonate, methylpropyl carbonate or ethylpropyl carbonate. These cleaning agents can also be used as electrolyte components, so that the presence of residues in the battery cell after the cleaning performed does not have a negative effect on the performance of the battery cell.

[0030] In a further advantageous manner, a cleaning agent is used which comprises at least one of the following components: ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), butylene carbonate, dipropyl carbonate, methylpropyl carbonate or ethylpropyl carbonate for the reduction of lithium hydroxide after electrode production or in the production of lithium-ion battery cells.

[0031] Battery cells produced according to the present disclosure have the advantage that they can be produced cost-effectively on the one hand and do not have performance losses due to contaminants on the other hand.

[0032] In particular, it is advantageous here if the amount of LiOH remaining after cleaning is less than or equal to 0.1 weight percent [wt %] relative to the active material.

[0033] The avoidance of performance losses also has a positive effect during operation of a motor vehicle equipped with at least one battery cell produced according to the invention.

[0034] It should be noted as a precaution that the numerals used here ("first", "second", . . .) are preferably (only) used to distinguish between a plurality of similar objects, variables or processes, i.e., in particular, the relationship and / or sequence of these objects, variables or processes to one another are not necessarily predetermined. If a relationship and / or sequence is necessary, this is explicitly stated here or becomes obvious to a person skilled in the art when studying the specifically described configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention and the technical field are explained in more detail below with the aid of the drawings. It should be pointed out that the invention is not to be restricted by the exemplary embodiments listed. Unless otherwise explicitly indicated, it is also possible in particular to extract partial aspects of the actual situation illustrated in the drawings and combine them with other components and knowledge according to the present description. It should be pointed out in particular that the drawings and in particular the dimensional ratios shown are only schematic. Among them:

[0036] Figure 1 : shows an apparatus for implementing a manufacturing process for a battery cell;

[0037] and

[0038] Figure 2 : A vehicle with a battery unit is shown. DETAILED DESCRIPTION

[0039] exist Figure 1 , an apparatus 1 with which the present invention can be implemented is shown. From the left, the apparatus 1 is supplied with four materials 2, 3, 4, 5. This means that the apparatus 1 is constructed for producing a sub-stack 6, which has a four-layer structure. In the case of the current embodiment, the second material 2, the third material 3 are respectively constructed as a separator 7. The first material 5 is constructed as a cathode 8 and the fourth material 4 is constructed as an anode 9. While the materials 2, 3, 4, 5 pass through the apparatus 1, these materials undergo sections I) to VI).

[0040] Section I) shows the supply of materials 2, 3, 4, 5.

[0041] In section II), the second material 2 and the fourth material 4 are gathered into a first sub-pile 10. Furthermore, the third material 3 and the first material 5 are gathered into a second sub-pile 11.

[0042] The following section III) shows the joining of the first partial stack 10 with the second partial stack 11 to form the finished partial stack 6 .

[0043] In section IV), the sub-stacks 6 which have been produced in a continuous cycle up to now are cut to the required length by means of a cutting device 12 .

[0044] In section V), a plurality of partial stacks 6 are then arranged one above the other in the storage chamber 13 to form a battery stack 14. The battery stack is then connected to form a battery pack 16 and then in section VI) is hermetically enclosed by a housing 15, thereby forming a battery cell 18.

[0045] The cleaning proposed by the invention can be carried out at almost any point in the course of the production process during sections I) to VI) and in the most different forms by means of the cleaning device 17. Figure 1 In FIG. 1 , possible positions of these cleaning devices 17 within the device 1 are indicated by means of triangles. At these positions, cleaning by means of the cleaning devices 17 can be carried out, for example.

[0046] In the case of a particularly simple embodiment, it may be sufficient to clean only one material at only one position by means of the cleaning device 17, while the cleaning of the materials 2, 3, 4, 5 can also be achieved at multiple different positions when necessary. Here, the cleaning device 17 is preferably constructed so that the materials 2, 3, 4, 5 to be cleaned, the first or second sub-stack 10, 11, the finished sub-stack 6, the battery stack 14 or the battery pack 16 are the elements to be cleaned. These elements are washed in a solution for this. The solution can be, for example, an EC / EMC washing solution. For this, the elements to be cleaned can be immersed in the washing solution and then dried. The cleaning device 17 can also be designed so that the elements to be cleaned undergo multiple solvent tanks arranged in series. Through the cleaning program implemented by the cleaning device 17, the elements to be cleaned and therefore also the battery cells 18 manufactured thereby are freed from contaminants such as LiOH (lithium hydroxide).

[0047] The cleaning device 17 shown in section VI) can also be designed in such a way that first an EC / EMC washing solution is introduced into the housing 15 by means of an electrolyte filling device (not shown in detail) and then sucked away again, wherein the battery pack 16 located in the housing 15 is cleaned of contaminants. This process can also be repeated multiple times and preferably automatically if necessary. It is particularly advantageous if this type of cleaning is carried out locally in a drying chamber, because here renewed contact with moisture can be prevented particularly effectively.

[0048] Additionally, during the cleaning process, in each case of cleaning performed by means of the cleaning device 17 , an electrical potential can be applied to the component to be cleaned or a lithium salt can be dissolved in the cleaning agent used.

[0049] The use of dissolved lithium salts in the cleaning solution and the use of dissolved lithium salts in the cleaning solution in combination with the application of an electric potential can contribute to the (pre)forming of the battery. Thus, the cleaning is already combined with the forming, which is a time and cost advantage in terms of the process. In addition, the cleaning solution / electrolyte substitution products formed during the cleaning / preforming are removed for the battery system. This leads to a reduction in parasitic reaction components in the battery. The cycle efficiency and life are thereby increased.

[0050] Another possibility for cleaning is to provide electrode washing of the cathode 8. This can be carried out as a post-process step of drying after the coating with active material has been achieved and before the process step of electrode stacking, that is to say the arrangement of the sub-stacks 6 one above the other. In particular, steps I) to IV) are provided for this purpose, in which the materials 2, 3, 4, 5 are still in the form of electrode rails or electrode sheets with a circulation length.

[0051] The invention allows already formed contaminants to be reliably removed, thereby eliminating the need for complex and not 100% reliable humidity control in extended production lines, thereby saving considerable costs.

[0052] Figure 2 Finally, a vehicle 19 is shown with a battery system 20, which comprises a plurality of battery cells 18. The battery system 20 makes electrical energy available to a control device 21, which, when required, sends this energy to an electric motor 22, which generates the driving force. The driving force is then in turn transmitted via a transmission 23 to wheels 24.

[0053] Reference Symbols List

[0054] 1 Device

[0055] 2 Secondary Material

[0056] 3. Third Material

[0057] 4 Fourth Material

[0058] 5 First Material

[0059] 6 Sub-heap

[0060] 7 Partition

[0061] 8 Cathode

[0062] 9 Anode

[0063] 10 First sub-pile

[0064] 11 Second sub-pile

[0065] 12 Cutting device

[0066] 13. Storage Room

[0067] 14 Battery stack

[0068] 15. Housing

[0069] 16 Battery Pack

[0070] 17 Cleaning device

[0071] 18 Battery Cells

[0072] 19 Vehicles

[0073] 20 Battery System

[0074] 21 Control device

[0075] 22 Electric Motor

[0076] 23 Transmission

[0077] 24 Wheels

Claims

1. A method for manufacturing a battery cell (18), comprising at least the following steps: a) continuously supplying at least a first material (5) and a second material (2); b) aggregating the first material (5) and the second material (2) and the third material and the fourth material into a sub-stack (6), wherein the first material comprises an active material for a cathode, the second material and the third material comprise a separator medium, and the fourth material comprises an active material for an anode; c) arranging the plurality of sub-stacks (6) into a battery stack (14); in, performing during at least one of said steps a), b) or c) a step d) comprising cleaning at least said first material (5), In this case, the cell stack (14) is additionally surrounded by a housing (15) in step c), and step d) is carried out in the housing (15).

2. A method according to any one of the preceding claims, wherein: In step d), contaminants typical for the respective material ( 2 , 3 , 4 , 5 ) are removed.

3. A method according to any one of the preceding claims, wherein: Step d) comprises cathode washing.

4. A method according to any one of the preceding claims, wherein: In a step e) following step d), drying is carried out.

5. A method according to any one of the preceding claims, wherein: In step d) at least one of the following components is removed: LiOH, Li2CO3, NiCO3 and Ni(OH)2.

6. A method according to any one of the preceding claims, wherein: In step d), a cleaning agent is used which contains at least ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), butylene carbonate, dipropyl carbonate, methylpropyl carbonate or ethylpropyl carbonate.

7. A battery cell (18) manufactured according to any of the preceding patent claims 1 to 6.

8. A vehicle (19) having at least one battery unit (18) according to the preceding patent claim.

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