Apparatus for saturating a sheet electrode

Abstract

The present invention relates to an apparatus (4) for saturating a sheet electrode (1) composed of a metal substrate (2) and aactive material (3) of a galvanic cell with electrolyte (E). According to the invention, this apparatus comprises a feed opening (6) for pressurized electrolyte (E) in an electrolyte chamber (5). The electrolyte chamber is closed on one of its sides by means of a porous material (7) which forms a planar closure and which is thermally conductively connected to a heat energy source (+dQ / dt). To saturate the electrode (1), said apparatus (4) may be pressed onto said electrode, whereupon electrolyte (E) is fed into the electrolyte chamber (5), and evaporated in the region of the porous material (7), in order to saturate the active material (3) of the electrode (1) with electrolyte (E).

Description

[0001] Device for impregnating a sheet-shaped electrode

[0002] The invention relates to a device for impregnating a sheet-shaped electrode according to the type defined in more detail in the preamble of claim 1. Furthermore, the invention relates to a method for impregnating a sheet-shaped electrode using such a device. Finally, the invention also relates to a method for producing an electrode-separator assembly for a galvanic cell according to the type defined in more detail in the preamble of claim 8.

[0003] The impregnation of electrode-separator assemblies for galvanic cells, such as lithium-ion battery cells, typically takes place within the housing of the respective individual battery cell, into which the electrode-separator assembly is inserted. For this purpose, the housing is typically evacuated and often additionally heated. Afterward, the electrolyte is supplied from one side through an electrolyte filling opening, impregnating the electrode-separator assembly with the electrolyte. The electrolyte is essentially absorbed by the electrode-separator assembly through capillary forces.

[0004] Such a process is described in the article "Visualization of electrolyte filling process and influence of vacuum during filling for hard case prismatic lithium ion cells by neutron imaging to optimize the production process" by Weydanz et al. in the Journal of Power Sources 380 (2018) 126-134. The article shows corresponding images of a single battery cell during filling with electrolyte. These images show that, for a certain time after being filled into the housing, the electrolyte surrounds the entire electrode stack and is evenly sucked into the electrode stack from all ends. In practice, this leads to any moisture and gases that may still be present in the electrode stack, despite the evacuation, concentrating in the center of the electrode stack at the end of the filling process.In practice, such areas that are not or not completely saturated with the electrolyte then impair the performance of the individual battery cell and reduce its service life.

[0005] The object of the present invention is to provide a device and a method for impregnating a sheet-shaped electrode and a method for producing an electrode-separator arrangement for a galvanic cell, by means of which the impregnation of the electrode-separator arrangement is improved.

[0006] According to the invention, this object is achieved by a device having the features in claim 1, and in particular in the characterizing part of claim 1. Furthermore, the object is achieved by a method for impregnating a sheet-shaped electrode according to claim 4. Finally, a method for producing an electrode-separator arrangement for a galvanic cell according to claim 8 also achieves the object. Advantageous embodiments and further developments of the device and of the two methods emerge from the subclaims dependent thereon.

[0007] The device according to the invention for impregnating a sheet-shaped electrode made of a metallic substrate and an active material, which is typically arranged on both sides of the substrate, provides an electrolyte chamber having an electrolyte supply opening on one side and a side made of a porous material that closes the electrolyte chamber on the other. The structure can, for example, be designed, viewed in cross-section, as a hollow stamp, through whose stamp handle the electrolyte is supplied, and whose stamp surface is made of a porous material. This is placed adjacent to the active material of the electrode. The porous material is in thermally conductive contact with a heat energy source to evaporate the electrolyte. The vaporous electrolyte can then penetrate very easily and very evenly from the porous material into the active material and flow through it evenly.The electrolyte condenses in the active material of the electrode, ensuring a very homogeneous impregnation of the electrode with the electrolyte. The typical structure of the electrode plays a very advantageous role here. The metallic substrate on the side of the active material facing away from the porous material is a very good thermal conductor. Cooling will therefore occur first in the area of ​​the substrate, so that the active material, starting from its contact surface with the substrate, becomes increasingly impregnated with the electrolyte evaporated in the area of ​​the device, condensing from this side.

[0008] This device is ideal for impregnating the active material of an electrode with electrolyte. This is especially true if, according to a very advantageous development of the device according to the invention, the surface area of ​​the porous material corresponds to the surface area of ​​the sheet-shaped electrode to be impregnated. The device then allows the entire surface of the electrode to be wetted and saturated with electrolyte at once. This can be done without a vacuum, although a vacuum or negative pressure is also optionally possible here.

[0009] According to the process, a sheet-shaped electrode is impregnated using a device such that the electrolyte chamber of the device containing the porous material is pressed onto the surface containing the active material of the electrode. The force applied during pressing presses the porous material against the active material of the electrode. The electrolyte is then added. Due to the high pressure drop of the porous material, it is distributed evenly over the entire surface and is heated in the porous material until it evaporates. It then flows out of the porous material in vapor form over the entire surface and can thus flow very homogenously into the active material of the respective electrode and distribute itself evenly throughout the active material, which is typically also porous. The homogeneously distributed electrolyte vapor then condenses, so that the active material is impregnated with liquid electrolyte.Condensation occurs—as explained above—from the metallic substrate. Thus, the flow paths facing the porous material remain filled with gas until the very end, allowing the vaporous electrolyte to spread optimally, thus achieving very uniform saturation.

[0010] According to a very advantageous development of the method according to the invention, the electrode is connected to a heat sink for condensing the vaporous electrolyte. The electrode, and in particular the metallic substrate of the electrode, is thus actively cooled in order to even better support the condensation of the electrolyte within the active material, starting from the contact surface with the substrate. As already mentioned, the method can be carried out without a vacuum, so that the entire impregnation device does not have to be kept within an evacuated space. Nevertheless, according to a very advantageous development of the method according to the invention, it can be provided that it is carried out in a volume having a pressure reduced compared to the ambient pressure.A vacuum is not necessary; rather, a slight reduction in pressure is sufficient, which in particular lowers the boiling point of the electrolyte and thus reduces the necessary heating energy of the heating energy source accordingly.

[0011] It is particularly advantageous if the method is applied in such a way that two of the devices are pressed onto the sheet-shaped electrode from both sides. Thus, with an electrode made of a metallic substrate, for example, copper or aluminum, depending on whether the cathode or the anode is being impregnated, and the active material applied to it, the electrode is pressed onto this active material on both sides. This allows for relatively high pressures, as there is no one-sided loading of the mechanically relatively vulnerable electrode. The structure can thus be impregnated very quickly and efficiently with a sufficient amount of electrolyte, after which both sides of the active material of the respective electrode are evenly and completely impregnated with the electrolyte.

[0012] The inventive method for producing an electrode-separator arrangement for a galvanic cell then provides for the use of two different sheet-shaped electrodes, each consisting of a metallic substrate and an active material applied to both sides, with a separator arranged between them. The respective electrodes are impregnated with electrolyte according to the invention using the method and device described above and are then stacked with the separator to form the electrode-separator arrangement. The already impregnated or pre-impregnated electrodes ensure that the entire electrode-separator arrangement is uniformly impregnated with the electrolyte. It is now fundamentally possible to use the impregnation according to the method described above purely as pre-impregnation, i.e., to re-impregnate the stack in its housing.However, if the individual electrodes are sufficiently impregnated, such a step can be omitted. According to a very advantageous development, a sheet-shaped separator can be used for the inventive method, so that individual sheets of electrodes, separators, etc., are stacked on top of one another. Alternatively, it would also be conceivable to use a band-shaped separator that is folded into a Z shape, after which the impregnated or pre-impregnated electrodes are laterally inserted into the pockets created by the Z-shaped fold. In this way, too, an electrode-separator arrangement can be produced as a stack in a conventional manner.

[0013] Further advantageous embodiments of the device according to the invention and of the method according to the invention also emerge from the exemplary embodiment which is illustrated in more detail below with reference to the figure.

[0014] The only attached figure 1 shows in three individual images the process for impregnating an electrode with electrolyte using a device according to the invention.

[0015] The illustration on the far left of Figure 1 shows an electrode 1. It consists of a metallic substrate 2, for example, copper or aluminum, depending on whether it is the anode or the cathode. This metallic substrate 2 is coated on both of its surfaces with an active material 3. The active material 3 on the substrate 2 in the illustration on the left of Figure 1 is unimpregnated.

[0016] In the next station, shown in the middle of Figure 1, electrolyte stamps 4 are now pressed onto the active material 3 of the electrode 1 from above and below onto this structure of the unwetted electrode 1 with a force indicated by the arrows F. Each of these electrolyte stamps 4 represents a device 4 for impregnating the active material 3 of the electrode 1 with electrolyte E. This electrolyte E is shown here with irregular cross-hatching. Each of the electrolyte stamps 4 comprises an electrolyte chamber 5, which merges into a hollow stamp shaft 6, which is designed as a supply opening 6 for the electrolyte E. In the direction of the electrode 1, the respective electrolyte chamber 5 is closed by a porous material 7.

[0017] The porous material 7 forms a flat seal whose surface area corresponds to the surface of the electrode 1 to be wetted or its active material 3. On the one hand, the porous material 7 imposes such a high pressure drop on the electrolyte E that the electrolyte is evenly distributed over the entire surface of the porous material 7 and can be evaporated therein. For this purpose, the porous material 7 is connected to a heating energy source +dQ / dt. This heating energy source +dQ / dt supplies the heat required for evaporation.

[0018] The electrolyte stamps 4 are now pressed against the active material 3 of the electrode 1, as already indicated above and shown in the center by the force arrows F in Figure 1. The electrolyte E is then evaporated, so that it emerges in vapor form from the porous material 7 and flows evenly over the entire surface into the area of ​​the active material 3. The vaporous electrolyte E can be distributed evenly and very homogeneously in the likewise porous active material 3. The metallic substrate 2 of the electrode 1 is, due to its metallic design, very good thermal conductivity and can ideally be connected to a heat sink -dQ / dt. The substrate 2 and thus ultimately the electrode 1 are thereby actively cooled. This active cooling can be used in particular when the vapor of the electrolyte E has already penetrated the active material 3.Together with the existing heat dissipation through the substrate 2 and the additional optional cooling of the same via the heat sink -dQ / dt, this results in the vaporous electrolyte E condensing out from the contact surface between the active material 3 and the substrate 2 and completely and evenly saturating the active material in the direction of the electrolyte stamp 4. With sufficient residence time of the electrode 1 between the two electrolyte stamps 4, the entire active material 3 is very homogeneously saturated with electrolyte. This state of the electrode 1, whose active material 3 is completely saturated with the electrolyte E, is shown on the right in Figure 1.

[0019] An electrode-separator arrangement, which is not explicitly shown here, can then be stacked, for example, from such impregnated electrodes 1 of the respective polarity, alternating with separators arranged between them. This stack produced in this way can then be integrated into a housing to form the actual individual battery cell. This can preferably be implemented as a lithium-ion cell, which can be used, for example, in a traction battery for at least partially electrically powering a vehicle.

Claims

Patent claims Device (4) for impregnating a sheet-shaped electrode (1) made of a metallic substrate (2) and active material (3) for a galvanic cell with electrolyte (E), characterized in that a supply opening (6) for electrolyte (E) is provided in an electrolyte chamber (5), wherein the electrolyte chamber (5) is closed on one side by a porous material (7) which forms a planar closure of the electrolyte chamber (5) and which is in thermally conductive connection with a heating energy source (+dQ / dt). Device (4) according to claim 1, characterized in that the planar closure corresponds in its area to the area of ​​the active material (3) of the sheet-shaped electrode (1) to be impregnated. Device (4) according to claim 1 or 2, characterized in that the supply opening (6) in the electrolyte chamber (5) is arranged opposite the porous material (7).Method for impregnating a sheet-shaped electrode (1) made of a metallic substrate (2) and active material (3) by means of at least one device according to one of claims 1 to 3, characterized in that the electrolyte chamber (5) of the device (4) with the porous material (7) is pressed onto the electrode (1) and electrolyte (E) is supplied, while at the same time. the porous material (7) is heated by the heating energy source (+dQ / dt) in such a way that the electrolyte (E) leaves the porous material in vapor form in the direction of the electrode (1). Method according to claim 4, characterized in that the electrode (19) is connected to a heat sink (-dQ / dt) for condensing the vaporous electrolyte (E). Method according to claim 4 or 5, characterized by its implementation in a volume with a pressure reduced compared to the ambient pressure. Method according to one of claims 4 to 6, characterized in that two of the devices (4) are pressed onto the sheet-shaped electrode (1) from both sides thereof, after which electrolyte (E) is supplied to the electrolyte chambers (5) of the two devices (4).A method for producing an electrode-separator assembly for a galvanic cell, comprising two different sheet-shaped electrodes (1), each made of a metallic substrate (2) and active material (3), and separators arranged therebetween. The method according to claim 4 to 7 comprises impregnating or at least pre-impregnating the respective electrodes (1) with electrolyte (E) and then stacking them with the separators to form the electrode-separator assembly. The method according to claim 8 comprises using sheet-shaped separators. Method according to claim 8, characterized in that a band-shaped separator is folded in a Z-shape, after which the different electrodes (1) are inserted laterally into the folds.

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