Individual battery cell, filling device, and method for filling the individual battery cell with electrolyte

Abstract

The invention relates to an individual battery cell (1) comprising a housing (2) and an electrode-separator assembly which is arranged in the housing (2), said housing (2) having at least one filling opening (10, 11) for an electrolyte (E). The individual battery cell according to the invention is characterized in that the housing (2) has at least one discharge opening (12, 13) for the electrolyte (E), said discharge opening being arranged on the face lying opposite the filling opening (10, 11). The invention additionally relates to a filling device (22) for filling such an individual battery cell (1) with electrolyte (E) and to a method for same.

Description

[0001] Single battery cell, filling device and method for filling the single battery cell with electrolyte

[0002] The invention relates to a single battery cell with a housing as defined in more detail in the preamble of claim 1. Furthermore, the invention relates to a filling device for filling such a single battery cell with electrolyte. The invention also relates to a method for filling such a single battery cell with electrolyte using such a filling device.

[0003] Such individual battery cells are known from the general state of the art. They consist, for example, of a coil or stack as an electrode-separator arrangement, with at least one such electrode-separator arrangement arranged in the housing.

[0004] In current practice, the housings for the individual battery cells are evacuated and heated before being filled with electrolyte, before the electrolyte is then added via a filling opening. Inside the cell is then one or more electrode-separator assemblies, for example in the form of an electrode stack, which are then wetted with electrolyte. Capillary forces draw the electrolyte from the outside to the inside into this stack. The electrolyte is essentially "sucked in." In this context, DE 10 2010 052 397 A1 describes a method and a device for filling an electrochemical cell, in which the filling of the electrolyte is intended to be improved by subjecting the housing to varying pressures.

[0005] 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 sides. 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.

[0006] DE 102021 204659 A1, similar to US 2018 / 0309114 A1, describes a high-voltage battery system in which an external circuit for an electrolyte is provided. Accordingly, the individual battery cells have openings connected to an electrolyte supply and an electrolyte discharge, allowing electrolyte to continuously flow through the circuit during operation.

[0007] DE 102014221300 A1 also discloses a device and method for removing particles from individual battery cells. After production, the individual battery cells are rinsed with a rinsing medium, for example, the electrolyte that will later be used, to remove potential residues from the production of the individual battery cells from the housings before the actual filling of the individual battery cells with the electrolyte. Electrolyte can be used as the rinsing medium, which must be cleaned and treated after the battery cell has been rinsed.

[0008] For further prior art, reference can also be made to DE 102011 115495 A1, which shows a complex method for pretreating precursors for an electrochemical cell, wherein these precursors can comprise electrodes pre-wetted with electrolyte, which are pre-processed electrically and mechanically.

[0009] The object of the present invention is to provide an improved structure for a single battery cell which facilitates uniform filling with electrolyte. It is also the object to provide a filling device for filling such a single battery cell and a suitable method for this purpose. According to the invention, this object is achieved by a single battery cell having the features in claim 1, and in particular in the characterizing part of claim 1. A filling device according to the invention which achieves the above-mentioned object is found in claim 3. Claim 5 specifies a method according to the invention for filling a single battery cell according to the invention using a filling device according to the invention. Advantageous embodiments and further developments of claims 1, 3 and 5 arise from the subclaims dependent thereon.

[0010] The single battery cell according to the invention is provided not only with at least one filling opening for the electrolyte, as is also common in the prior art. Rather, the single battery cell according to the invention has at least one discharge opening for electrolyte on its housing on a side opposite the filling opening. Such a discharge opening for electrolyte now creates the possibility of filling the electrolyte via the filling opening not in a "dead-end" manner, but also of partially discharging it again if necessary. The electrolyte can therefore be added in excess in order to always provide sufficient electrolyte so that the electrode-separator arrangement can absorb it accordingly.Unused electrolyte flows out of the housing through the drain opening, ensuring that no flow channels are blocked by electrolyte that has not been drawn into the electrode-separator assembly by capillary forces. This leaves enough space to absorb gases from the electrode-separator assembly or to discharge them with the excess electrolyte. This prevents them from becoming trapped inside the electrode-separator assembly, and the assembly is evenly saturated. Such even saturation ensures good performance and a long service life for the individual battery cell, as critical areas in terms of performance and, in particular, aging, where electrolyte-soaked areas of the active material are located adjacent to non-soaked areas of the active material, can be avoided.It is precisely these boundary areas that cause faster aging due to the high potential differences that occur in a very small space during operation, which can lead to corrosion of the active material. The drain opening can, for example, be positioned at the bottom, in the direction of gravity, so that the electrolyte drains off automatically. It can then be collected and refilled. A recirculation system with its own conveying system can be particularly advantageous here.

[0011] The single battery cell according to the invention provides for two filling openings at opposite ends of a first side, with two discharge openings at opposite ends of a second side facing away from the first side. In this particularly advantageous embodiment, two filling openings are provided on one side, each at different ends of this side, for example, at the top right and left of the side used as the lid, in the direction of gravity. Accordingly, corresponding discharge openings can also be provided on the right and left of the opposite side, in this case the bottom.This allows the mechanism described above to be used on both sides, so that the two lateral edge channels serve to provide electrolyte, with excess electrolyte being drained through the drain openings as described above until the electrode-separator assembly is completely saturated with electrolyte.

[0012] This advantageous embodiment of the single battery cell according to the invention can provide that the electrode-separator arrangement is surrounded on at least four sides in the housing by an edge channel, wherein the at least one filling opening and the at least one discharge opening are located in the region of this edge channel. As a result, electrolyte can be metered into the edge channel at the center of gravity and excess electrolyte can be discharged from the edge channel. If electrolyte is now continuously made available in the region of the edge channel, it can be absorbed very evenly by the electrode-separator arrangement. Electrolyte that is not required at the time of use escapes from the edge channel or the housing via the discharge opening and can be made available again via the filling opening when required, as already indicated above.

[0013] A filling device for filling a single battery cell with electrolyte provides that, for a single battery cell as described above, at least one electrolyte source and one supply line are provided. The supply line is configured to connect the electrolyte source to the at least one filling opening, so that the electrolyte can enter the housing of the single battery cell via the filling opening. The filling device also comprises at least one discharge line with a conveying device in the discharge line. The discharge line is configured to connect the at least one discharge opening of the single battery cell to the electrolyte source to form an electrolyte circuit.As already explained above, such an electrolyte circuit can provide excess electrolyte, which can then be absorbed by the electrode-separator assembly to impregnate the active material of the electrodes. At the same time, the electrolyte circulation allows excess electrolyte to be removed again, thus preventing channels and areas from being flooded with electrolyte, which may still be needed to allow moisture or gases to escape from the electrode-separator assembly. This allows for very uniform impregnation without trapping any gases in the electrode-separator assembly.

[0014] As already mentioned, according to a very advantageous embodiment of the filling device according to the invention, the conveying device can be designed to suck electrolyte through the discharge openings and part of the discharge line. Thus, the electrolyte is not simply allowed to drain, which would in principle also be possible by gravity and without the use of the filling device, but is actively sucked out to actively counteract its spread into undesired areas and thus prevent the electrode-separator assembly from being completely surrounded by electrolyte.

[0015] The filling device is designed such that a separate electrolyte circuit is provided for each of the pairs of filling openings and discharge openings. Thus, with this particularly advantageous embodiment of the individual battery cell according to claim 3, using a particularly advantageous embodiment of the filling device, two circuits can be provided. These can preferably be arranged to the right and left of the battery housing, with the filling openings being arranged at the top in the direction of gravity, i.e. in the cover of the housing, and the discharge openings correspondingly at the bottom, i.e. in the base of the housing. Overall, this allows the electrolyte to be provided in the right and left edge channels, while the lower and upper edge channels remain open to absorb moisture, gases, and the like as needed.

[0016] The inventive method for filling a single battery cell according to one of claims 1 or 2 with electrolyte, using a filling device according to claim 3 or 4, provides that electrolyte is supplied to the interior of the housing of the single battery cell via the at least one filling opening, wherein at least in a first temporal phase of the filling, electrolyte is discharged from the at least one discharge opening and recirculated. In the first temporal phase of the filling, a corresponding excess of electrolyte is therefore provided in the method, wherein this first temporal phase of the filling ideally lasts until the electrode-separator arrangement is largely completely impregnated with electrolyte. A time frame for this can, for example, be determined empirically or estimated by simulation.

[0017] Furthermore, the circulation is terminated at the beginning of a second time phase, after which the discharge openings are closed. The discharge openings are thus closed to prevent the electrolyte from flowing out. The circulation is terminated, but electrolyte can continue to be supplied, which can now fill the other areas of the edge channel. This ensures a sufficient excess of electrolyte in the housing so that any areas within the electrode-separator arrangement that are not fully saturated can absorb the electrolyte. The excess electrolyte then ensures that it is sufficiently available during operation.

[0018] During this second phase, electrolyte continues to be supplied to fill the remaining areas accordingly and ensure complete saturation of the entire electrode-separator assembly and at least a largely complete filling of the entire housing with electrolyte. After the second phase, the electrolyte supply is stopped, and the filling openings are closed.

[0019] A favorable embodiment of the method according to the invention can provide for the closure of the discharge openings and the filling openings, or alternatively, only one of the opening types, by welding in sealing plugs. Such welding of sealing plugs can be ideally used, for example, in a plastic housing, a composite housing, or a metal housing, particularly an aluminum housing, to seal the housing tightly and securely. For this purpose, sealing plugs can be inserted and secured in the corresponding openings using suitable welding processes, for example. This can be done, for example, by friction welding, but also by ultrasonic welding or the like.

[0020] Further advantageous embodiments of the individual battery cell according to the invention, the device and the method also emerge from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0021] Showing:

[0022] Fig. 1 shows the impregnation of an electrode-separator arrangement with electrolyte according to the aforementioned prior art from the “Journal of Power Sources”; and

[0023] Fig. 2 is a representation of the impregnation of an electrode-separator arrangement with electrolyte analogous to the representation in Fig. 1 , but with the housing and a device according to the invention.

[0024] 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 the example of a prismatic single battery cell 1 shown here is formed from several cuboid-shaped housing walls 3. Within this housing 2 is an electrode-separator arrangement 4, which here is designed as a stack of electrodes and separators, for example. 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 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 irregular cross-hatching. The electrolyte E is filled into the opening 7 according to the arrow shown, the housing 2 having been evacuated beforehand. The electrolyte E now begins to distribute 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 within the stack 4, so that the stack 4 is largely impregnated. If gases and / or moisture 9 remain in the stack 4 despite the evacuation and typically heating of the individual battery cell 1 prior to impregnation with the electrolyte E, these gases and / or moisture 9 are now enclosed within the stack by the electrolyte E sucked into the stack 4 from all sides and remain, as indicated by the white oval in the illustration 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 sucked 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 single battery cell 1.

[0025] In the illustration in Figure 1, the gases and / or moisture therefore remain in the area designated by 9. However, in order to ensure that as much gas and / or moisture as possible can escape from the interior of the stack 4 of the electrode-separator arrangement, it is necessary to avoid this stack 4 becoming wetted all around with the electrolyte E for as long as possible. A suitable filling device 22 is shown schematically in the illustration in Figure 2. Instead of the one filling opening 7 according to the prior art, there are now two filling openings 10, 11, which are arranged on the upper housing wall 3, i.e. the cover of the housing 2 of the individual battery cell 1, at opposite ends. They essentially correspond to the two sections of the edge channel 8 in the illustration in Figure 2, to the right and left of the side next to the stack 4. On the opposite housing wall 3, i.e. the underside orthe bottom of the housing 2, corresponding discharge openings 12, 13 are arranged. The two filling openings 10, 11 are each connected to an electrolyte source 16, 17 via filling lines 14, 15, whereby a single electrolyte source 16, 17, for example a common storage container for electrolyte, could also be used here. The corresponding discharge openings 12, 13 are each also connected to the respective electrolyte source 16, 17 via a discharge line 18, 19. Conveying devices 20, 21 are provided for sucking out the excess electrolyte E from the two right and left areas of the edge channel 8. This creates a circuit for the electrolyte E for one pair of filling opening 10 and discharge opening 12 as well as for the other pair of filling opening 11 and discharge opening 13.

[0026] In a first temporal phase of filling the housing 2 with the electrolyte E, these two circuits can now be operated accordingly, in which electrolyte is supplied in quasi-excess via the electrolyte sources 16, 17 and at the same time a portion of this electrolyte E is sucked out again via the conveyor devices 20, 21 and the discharge lines 18, 19 through the discharge openings 12, 13. This continues until the stack 4 is largely saturated with the electrolyte E. The circulation and in particular the suction via the discharge openings 12, 13 ensure that the areas of the edge channel 8 located above and below the stack 4 in the illustration in Figure 2 are not completely filled with electrolyte, so that gases and / or moisture can escape unhindered from the stack 4 into these areas.

[0027] Once, after this first phase of circulation, the stack 4 is now completely or at least largely impregnated with the electrolyte E, the two circuits or the conveyor devices 20, 21 can be switched off and the discharge openings closed, for example by welding in sealing plugs. Subsequently, in a second phase, a certain amount of the electrolyte E can still be supplied from the electrolyte sources 16, 17 in order to be metered into the housing 2 as excess, so that previously unfilled areas of the housing 2 are also filled with electrolyte. At the end of this second phase, this additional supply of electrolyte E is also switched off and the filling openings 10, 11 are closed, for example also by welding in sealing plugs.The stack 4 of the single battery cell 1 can thus be almost completely impregnated with the electrolyte E without, as in the prior art shown in Figure 1c), areas 9 containing gases and / or moisture remaining within the stack 4. Rather, a uniform and homogeneous impregnation of all the electrodes in the electrode-separator arrangement of the stack 4 is achieved by means of the filling device 22 shown in Figure 2.

Claims

Patent claims Single battery cell (1) with a housing (2) and an electrode-separator arrangement which is arranged in the housing (2), wherein the housing (2) has at least one filling opening (10, 11) for an electrolyte (E), wherein the housing (2) has at least one discharge opening (12, 13) for the electrolyte (E) arranged on a side opposite the filling opening (10, 11), characterized in that two of the filling openings (10, 11) are provided at opposite ends of a first side, wherein two discharge openings (12, 13) are provided at opposite ends of a second side which is opposite the first side.Single battery cell (1) according to claim 1, characterized in that the electrode-separator arrangement is surrounded on at least four sides in the housing (2) by an edge channel (8), wherein the at least one filling opening (10, 11) and the at least one discharge opening (12, 13) open into the region of the edge channel (8). Filling device (22) for filling a single battery cell (1) according to one of claims 1 or 2 with electrolyte (E), which has at least one electrolyte source (16, 17) and at least one supply line (14, 15) for the electrolyte (E), which is designed to connect the electrolyte source (16, 17) to the at least one filling opening (10, 11), wherein at least one discharge line (18, 19) and a conveying device (20, 21) arranged therein are provided, wherein the discharge line (18, 19) is designed to connect the at least one discharge opening (12, 13) to the electrolyte source (16, 17) to form an electrolyte circuit, characterized in that a separate electrolyte circuit is provided for each of the pairs of filling opening (10, 11) and discharge opening (12, 13). Filling device (22) according to claim 3, characterized in that the at least one conveying device (20, 21) is provided for sucking electrolyte (E) through the discharge opening (12, 13) and a portion of the discharge line (18, 19).Method for filling an individual battery cell (1) according to one of claims 1 or 2 with electrolyte (E) using a filling device (22) according to one of claims 3 or 4, wherein electrolyte (E) is supplied to the interior of the housing (2) of the individual battery cell (1) via the at least one filling opening (10, 11), wherein at least in a first temporal phase of the filling, electrolyte (E) is discharged from the at least one discharge opening (12, 13) and returned to the circuit, characterized in that the circulation is ended at the beginning of a second temporal phase, after which the at least one discharge opening (12, 13) is closed, wherein in the second temporal phase, electrolyte (E) continues to be supplied to the housing (2), wherein after the second temporal phase, the supply of the electrolyte (E) is stopped and the at least one filling opening (10, 11) is closed.Method according to claim 5, characterized in that the closure of the discharge opening (12, 13) and / or the filling opening (10, 11) is effected by welding in a closure plug.

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