Electrode for a single battery cell, single battery cell and method for filling with electrolyte

Abstract

The invention relates to an electrode (10) for a single battery cell (1) having a metallic substrate (14) coated with an active material (15) on at least one of its sides. The electrode according to the invention is characterized in that the active material (15) has at least one peripherally open opening (12). The invention also describes a single battery cell (1) having such an electrode (10), and a method for filling this single battery cell (1) with electrolyte (E).

Description

[0001] Electrode for a single battery cell, single battery cell and method for filling with electrolyte

[0002] The invention relates to an electrode for a single battery cell according to the type defined in more detail in the preamble of claim 1. Furthermore, the invention relates to a single battery cell with an arrangement of separators and such electrodes in a prismatic housing. Finally, the invention also relates to a method for filling such a single battery cell with electrolyte.

[0003] The production of electrodes for single battery cells is known from the prior art. Typically, for example, for single battery cells in lithium-ion technology, metallic substrates are used, made of copper or aluminum depending on the pole, and coated with an active material on at least one side. These electrodes are then stacked or rolled up, alternating in polarity with separators arranged between them, to form an electrode-separator arrangement. They are then impregnated in a battery housing with the electrolyte required for the cell chemistry used.

[0004] The basic structure of a single battery cell, referred to there as a converter cell, including its manufacturing process, is described, for example, in DE 102012 012 790 A1. The disclosure therein shows the manufacture of the housing and the converter cell as such, without going into any great detail about the structure of the individual electrodes and the electrolyte impregnation.

[0005] In current practice, however, the housings for the individual battery cells are evacuated and heated before being filled with electrolyte. One or more electrode-separator assemblies are then located inside the cell, for example in the form of an electrode stack, which is then wetted with electrolyte. Capillary forces draw the electrolyte from the outside to the inside into this stack. The electrolyte is essentially "sucked in". 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. Corresponding images of an individual battery cell during filling with electrolyte are shown.These images show that, for a certain time after filling the housing, the electrolyte surrounds the entire electrode stack and is evenly drawn into the electrode stack from all sides. In practice, this leads to any moisture and gases remaining in the electrode stack, despite the evacuation, concentrating in the center of the electrode stack at the end of the filling process. Such areas, which are not or not completely saturated with the electrolyte, then impair the performance of the individual battery cell and reduce its service life.

[0006] From DE 102018216 523 A1 and very similarly also from JP 2015 032 389 A it is known to provide continuous degassing channels in the area of ​​a single battery cell between the active material, i.e. the electrode, and the electrical conductor.

[0007] The object of the present invention is to provide an improved electrode for a single battery cell and a single battery cell constructed therewith. Furthermore, the object of the invention is to provide a method for filling with electrolyte that is suitable for constructing a single battery cell with such an electrode.

[0008] According to the invention, this object is achieved with regard to the device by an electrode having the features in claim 1, and here in particular in the characterizing part of claim 1. Furthermore, a single battery cell according to claim 7 achieves the object. Advantageous embodiments of the electrode arise from the subclaims dependent on claim 1. With regard to the method, the object is achieved by a method according to claim 8. Here too, an advantageous embodiment arises from the dependent subclaim. The electrode for a single battery cell has, as is also customary in the prior art, a metallic substrate which is coated on at least one of its sides with an active material, wherein the active material has at least one open-edged opening.Such an open-edged opening in the active material is an opening which, in a plan view of the surface of the active material, is designed such that it is openly connected to a side edge of the planar coating of the active material. According to the invention, two aligned open-edged openings are provided, which are open on opposite side edges. They therefore protrude from the two opposite side edges into the surface of the electrode coated with the active material, without the mutually facing ends of the two open-edged openings touching. The open-edged openings, which preferably run through the entire thickness of the active material, therefore do not divide the surface of the active material into two separate regions.

[0009] According to a very advantageous development, the open-edge opening can extend across the entire thickness of the active material, so that in the area of ​​the open-edge opening, the substrate can be seen when looking at the coated surface. The opening can therefore be free of active material. In principle, however, it is sufficient if the open-edge opening is designed in such a way that the thickness of the active material in its area is so significantly reduced compared to the surrounding areas that a corresponding opening or depression is created.

[0010] According to an advantageous embodiment of the electrode according to the invention, at least one of the open-edged openings can be designed as a linear channel. Such a linear channel can, for example, extend from the central region of the surface of the coated material to one of the side edges and thus connect one end region of the opening with the opposite open-edged region of the opening or channel, thus creating a flow-through opening, for example, from the central region of the active material to its edge. A linear channel enables this connection with minimal space requirements.

[0011] The open-edge opening can preferably end centrally in one of the side edges, i.e., it is arranged centrally with respect to the coated surface, at least in the region of its open-edge end. At least one of the open-edge openings can preferably be created by laser ablation on the electrode already coated with the active material, so that the coating of the active material is completely or at least partially removed again by laser processing in the region of the desired open-edge opening.

[0012] A single battery cell according to the invention provides for an arrangement of separators and electrodes in one of the described embodiments to be arranged in a prismatic housing. The arrangement of separators and electrodes is surrounded in the housing by an edge channel into which the at least one open-edge opening of the electrodes opens. The open-edge opening is thus connected to the edge channel.

[0013] A very advantageous method for filling such a single battery cell with electrolyte provides that the open-edged openings face one of the sides of the housing or, preferably, two opposite sides of the housing, wherein the electrolyte is supplied on one of the sides to which at least one of the open-edged openings faces. The electrolyte is thus metered into the housing in a manner known per se. The open-edged openings are at least partially assigned to the side on which the electrolyte is supplied. They are therefore open at the edges in this direction. For example, individual electrodes can be designed with the open-edged sides in this direction and other electrodes with the open-edged sides in the opposite direction or a direction transverse thereto.All in all, when filled with electrolyte in this way, the open-edged openings ensure that gases and, if present, moisture that have accumulated in the active material can escape through them for a relatively long time. The open-edged openings thus improve the removal of gases and moisture from the active material, allowing the remaining active material to be better saturated with the electrolyte.

[0014] The open-edge openings do indeed dispense with some of the active material, as the area of ​​the open-edge openings contains no or only a very reduced amount of active material. However, the improved impregnation compensates for this apparent disadvantage in terms of area, because with a suitable design of the open-edge openings, the area required for them can be smaller than the area typically required, which in at least some electrodes is not wetted or is only very unevenly wetted in the center by trapped gases and moisture, and is therefore also not electrochemically active. Furthermore, the areas where the active material is present experience much more homogeneous wetting with the electrolyte. This prevents adverse effects at interfaces between wetted and unwetted areas of the active material, giving the cell better resistance to aging.

[0015] According to a very advantageous development of the method according to the invention, the electrolyte can be supplied centrally on one side of the housing, so that it spreads out from the center and the gases can escape very well, particularly on the opposite side, through an opening open at the edge.

[0016] Further advantageous embodiments of the electrode and the individual battery cell according to the invention as well as the improved impregnation of the electrode-separator arrangement with electrolyte to be achieved thereby also emerge from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0017] Showing:

[0018] Fig. 1 shows an illustration of the impregnation of an electrode-separator arrangement with electrolyte according to the prior art mentioned at the beginning from the “Journal of Power Sources”;

[0019] Fig. 2 is a representation of the first step of impregnating an electrode-separator assembly in a single battery cell according to the invention; and

[0020] Fig. 3 Sectional view along the line ll-ll in Fig. 2 through part of the electrode-separator arrangement.

[0021] The illustration in Figure 1, based on the article in the Journal of Power Sources 380 (2018) 126-134 mentioned at the beginning, shows how a conventional single battery cell 1 is impregnated with electrolyte. The single battery cell 1 consists of a housing designated 2, which in an example of a prismatic single battery cell 1 shown here is formed from several cuboid-shaped housing walls 3. Within this housing 2 there is an electrode-separator arrangement 4, which here is designed as an example as a stack of electrodes 10 and separators 11, some of which can be seen in Figure 3 in an embodiment according to the invention. It is therefore also referred to below as stack 4. Electrical connection lugs 5, 6 protrude from the single battery cell 1 through the housing wall 3 of the housing 2 shown here above.Between these connection lugs 5, 6 there is a filling opening designated 7 for electrolyte E, which is indicated here and in the following figures by an irregular cross-hatching.

[0022] The electrolyte E is filled into the opening 7 according to the arrow shown, the housing 2 having been previously evacuated. The electrolyte E now begins to distribute itself in an edge channel 8, which is formed between the end faces of the stack 4 and the housing walls 3, while at the same time it is sucked into the stack 4 by capillary forces from the areas where it is present in the edge channel 8. At the first time shown in Figure 1a), this occurs primarily from the side of the filling opening 7. At a somewhat later time in Figure 1b), the electrolyte E has already penetrated further into the edge channel 8 and into the stack 4. In the illustration in Figure 1c), the entire edge channel 8 is filled with electrolyte E and the electrolyte has largely distributed itself within the stack 4, so that the stack 4 is largely saturated.If, despite evacuating and typically heating the individual battery cell 1 prior to impregnation with the electrolyte E, gases and / or moisture 9 remain in the stack 4, these gases are now enclosed within the stack by the electrolyte E drawn into the stack 4 from all sides and remain, as indicated by the white oval in Figure 1c), within the stack, typically slightly below the center. In these areas, complete wetting of the active materials of the electrodes is then not achieved. Because the electrolyte E is drawn in from all sides, the gases and / or moisture cannot easily escape from the stack 4. In practice, this leads to a reduction in the capacity and service life of the individual battery cell 1.

[0023] In the illustration in Figure 1, the gases and / or moisture therefore remain in the area designated by 9. To remedy this problem, in the inventive design of the individual battery cell 1 or its electrodes 10, at least one edge-open opening 12 is provided in at least some of the electrodes 10, as can be seen in the illustration in Figure 2.

[0024] This shows a top view of the stack 4, analogous to the illustration in Figure 1a. The open-edge openings 12 are shown in dashed lines. They can, in particular, consist of open-edge channels, which are arranged centrally on the side of the stack 4 to which the electrolyte E is supplied through the filling opening 7, and correspondingly centrally on the opposite side. The open-edge openings 13 then protrude as rectilinear channels from the center of the respective side into the active material 13, which can be seen in the sectional view in Figure 3, but do not divide the surface of the active material 13 into two areas separated by the open-edge openings 12.

[0025] In the previously mentioned sectional view of Figure 3, one of the electrodes 10 is shown in the center of Figure 3 purely by way of example. Each of the electrodes 10 consists of a metallic substrate designated 14, to which the active material 13 is applied on at least one side, here preferably on both sides. In a lithium-ion battery single cell 1, the metallic substrate 14 consists, depending on which pole the electrode 10 forms, either of copper or a copper alloy or of aluminum or an aluminum alloy. The applied active material 13, which is applied on both sides in the view of Figure 3, now has the open-edged opening 12.This can, for example, be formed as a fine channel by laser ablation, so that the edge-open opening 12, which is preferably formed over the entire thickness of the active material 15, projects into the surface of the active material 13, as can be seen from the plan view according to Figure 2.

[0026] The size of the illustration in Figures 2 and 3 chosen to illustrate the invention is not to scale; rather, the edge-open openings 12, as well as the layer thickness in the illustration in Figure 3, are much smaller in reality, which also applies to the edge channel 8. This electrode 10 consisting of the substrate 14 and the active material 15 is then covered by the separator 11, after which another electrode 10 follows, this time that of the other pole of the individual battery cell 1, and immediately until the stack 4 described above as an electrode-separator arrangement consists of a plurality of such electrodes 10 and separators 11. In Figure 3, this is indicated by further separators 11 and electrodes 10 shown in dashed lines, as well as the continuation points.

[0027] If the electrolyte E is now drawn into the interior of the stack 4 by the capillary forces, then gas potentially still contained in the stack 4 and here typically in the porous active material 13 can escape through the fine channels of the edge-open openings 12 from the interior of the stack 4 into the edge channel 8, so that in contrast to the illustration in Figure 1, a complete impregnation of the stack 4 can be achieved, in which no unimpregnated areas 9 remain in the stack 4.

[0028] The use of such open-edge openings 12 does lead to a slight loss of capacity, since no active material is present in the laser-ablated areas of the open-edge openings 12, thereby reducing the total active area of ​​the single battery cell. However, in the areas where the active material 13 is present, wetting with the electrolyte E is much more homogeneous, so that adverse effects at interfaces between wetted and unwetted areas of the active material 13 are reduced or completely avoided. As a result, the single battery cell 1 exhibits improved performance and improved aging resistance, which far outweighs the slight area loss due to the open-edge openings 12.

Claims

Electrode (10) for a single battery cell (1) with a metallic substrate (14) coated on at least one of its sides with an active material (15), wherein the active material (15) has at least one open-edged opening (12), characterized in that two aligned open-edged openings (12) are provided, the open-edged ends of which lie on opposite side edges of the active material (15) without dividing the surface of the active material (13) into two regions separated by the open-edged openings (12). Electrode (10) according to claim 1, characterized in that at least one of the open-edged openings (12) is designed as a rectilinear channel. Electrode (10) according to claim 1 or 2, characterized in that the open-edged openings (12) each end centrally in one of the side edges.Electrode (10) according to one of claims 1 to 3, characterized in that at least one of the open-edge openings (12) is free of active material (15). Electrode (10) according to one of claims 1 to 4, characterized in that at least one of the open-edge openings (12) extends over the entire thickness of the. Active material (15). Electrode (10) according to one of claims 1 to 5, characterized in that at least one of the open-edge openings (12) is produced by laser ablation. Single battery cell (1) with an arrangement of separators (11) and electrodes (10) according to one of claims 1 to 6, in a prismatic housing (2), wherein the arrangement of separators (11) and electrodes (10) in the housing (2) is surrounded by an edge channel (8) into which the open-edge openings (12) of the electrodes (10) open. Method for filling a single battery cell (1) according to claim 7 with electrolyte (E), wherein the open-edged openings (12) face one of the sides of the housing (2) or two opposite sides of the housing (2), wherein the electrolyte (E) is supplied on one of the sides to which at least some of the open-edged openings (12) face.Method according to claim 8, characterized in that the electrolyte (E) is supplied via a filling opening (7) centrally in a side wall (3) of the side towards which at least some of the edge-open openings (12) face.

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