Method for manufacturing a stack of bipolar battery cells

Abstract

Method for producing a stack of bipolar battery cells (1), comprising the process steps that - Bipolar collectors (101, 102, ...), - a first active material (121, 122, ...), - Separators (141, 142, ...) and - a second active material (161, 162, ...), stacked alternately, so that in one stacking direction R S A growing stack of bipolar battery cells (1) is formed until a defined stack height is reached, wherein adjacent first active material (121, 122, ...) and second active material (161, 162, ...) with the respective interposed bipolar collector (101, 102, ...) form a bipolar electrode unit (181, 182, ...) and between adjacent bipolar electrode units (181, 182, ...) a [missing information] is formed between the respective bipolar collectors (101, 102, ...) in the stack direction R San extending and in the expansion plane sealing edge arrangement (221, 222, ...) is applied for sealing, wherein - Sealing material of the sealing edge arrangement (221, 222, ...) is applied to the respective bipolar collector (101, 102, ...), - at least one filling nozzle (301, 302, ...) and the respective separator (141, 142, ...) are inserted into the sealing material, - the sealing material with a recess in the area of ​​the sealing material surrounding the filling nozzle (301, 302, ...) for an activation period t A1 is hardened to create seals (201, 202, ...) between the respective bipolar collectors (101, 102, ...) of adjacent bipolar electrode units (181, 182, ...) through the hardened sealing material of the sealing edge arrangements (221, 222), - an electrolyte filling is filled via the filling nozzles (301, 302, ...) into the respective space enclosed by the sealing edge arrangement (221, 222, ...) and - the filling nozzles (301, 302, ...) are removed from the respective sealing edge arrangements (221, 222, ...).

Description

[0001] The invention relates to a method for producing a bipolar battery cell stack with a recurring sequence of plate-shaped elements, namely bipolar collectors, a first active material, separators and a second active material.

[0002] Bipolar battery cell stacks, also known as bipolar batteries, are constructed according to a bipolar principle familiar from fuel cell technology. The bipolar collector is a metallic foil coated on both sides with active material. The active material is given the properties of a negative electrode on one side of the bipolar collector and a positive electrode on the other side of the bipolar collector through appropriate material selection. The unit, consisting of a bipolar collector and active material arranged or applied on both sides, can be referred to as a bipolar electrode unit.

[0003] A bipolar battery cell is created by arranging two bipolar electrode units so that their active materials are diametrically opposed, i.e., the negative electrode of one bipolar electrode unit is arranged flat against the positive electrode of the other bipolar electrode unit, with a separator as an intermediate layer. A seal is required between adjacent bipolar electrode units so that the battery cell, formed by two respective halves of the bipolar electrode units, can be filled with electrolyte, and this electrolyte can be retained within each battery cell. This flat, arranging of bipolar electrode units against one another, which can also be referred to as stacking, is continued until a defined stack height is reached.

[0004] The bipolar battery cells are stacked on top of each other over a large area or in a plate-like configuration. Vertical stacking is ideal, but this is not a mandatory stacking direction. If no surrounding housing is used, the space required is significantly reduced. Furthermore, the direct connection between the individual battery cells allows current to flow across the entire surface of each battery cell, which significantly reduces electrical resistance and increases efficiency. The battery cells can quickly release the energy stored in them and also quickly recharge it during a charging cycle.

[0005] In the prior art, the sealing between adjacent bipolar electrode units of the electrolyte filling in the battery cell is described as a problem. This affects both the direct sealing of the adjacent bipolar electrode units and the area of ​​the seal in which so-called filling nozzles were inserted into the bipolar electrode unit during stacking in order to evacuate the space between the bipolar electrode units and fill with electrolyte. Following filling with electrolyte, the filling nozzles are usually cut flush with the seal and the inner channel of the filling nozzle is either glued or fused or destroyed by heat. A disadvantage here is that the remainder of the filling nozzle, however sealed, remains in the seal and fundamentally represents a weak point.US 6174337 B1, for example, shows a bipolar battery cell stack with such filling nozzles. US 2011 / 0171503 A1 also describes a discrete electrolyte filling device that must be connected to the battery to fill the electrolyte chamber.

[0006] Based on this, the object of the present invention is to provide a method with which a continuous seal can be achieved between the bipolar electrode units despite electrolyte filling via filling nozzles.

[0007] The problem is solved by a method for producing a bipolar battery cell stack with a recurring sequence of - Bipolar collectors, - a first active material, - separators and - a second active material.

[0008] This creates a stacking direction R Sgrowing bipolar battery cell stack is formed until a defined stack height is reached.

[0009] Adjacent first active material and second active material form a bipolar electrode unit with the respective bipolar collector arranged therebetween, and between adjacent bipolar electrode units a bipolar collector is arranged between the respective bipolar collectors in the stacking direction R S extending and lying in the expansion plane, the sealing edge arrangement is applied for sealing.

[0010] Either before each stacking of a bipolar electrode unit or after stacking all bipolar electrode units, i.e. after reaching the defined stack height, - Sealing material of the sealing edge arrangement is applied to the respective bipolar collector, - at least one filling nozzle and the respective separator are inserted into the sealing material, - an electrolyte filling is filled via the filling nozzles into the respective space enclosed by the sealing edge arrangement and - the filling nozzles are removed from the respective sealing edge arrangements.

[0011] The method according to the invention allows the filler nozzles to be reused and thus do not remain as foreign bodies in the seal of the bipolar electrode units. This eliminates the disadvantages of the prior art, such as reduced mechanical stability and impaired sealing in the area where the filler nozzles are located. This, in turn, opens up the possibility of using multiple filler nozzles for each bipolar electrode unit and using these multiple filler nozzles to evacuate the bipolar electrode unit and fill it with electrolyte. This allows for a reduced cycle time, particularly for the evacuation and filling process steps.Filling with electrolyte via several filling nozzles also ensures a more even distribution of the electrolyte in the bipolar electrode unit from the outset, so that subsequent active distribution of the electrolyte in the bipolar electrode unit, for example by shaking, milling or corresponding storage, can be dispensed with.

[0012] In an embodiment of the method according to the invention, the sealing material is cured over an activation period tA1, leaving out the area of ​​the sealing material surrounding the filling nozzle, in order to create the seals between the respective bipolar collectors of adjacent bipolar electrode units by means of the cured sealing material of the sealing edge arrangements.

[0013] Alternatively, it can also be provided that the sealing material is a non-curing adhesive, for example butyl rubber, so that the filling nozzle is pulled out of the sealing material and then the bipolar battery cell stack is pressed together in the stacking direction in order to close the remaining hole after the filling nozzle has been pulled out.

[0014] For the two process steps of filling with electrolyte and removing the filling nozzles from the sealing edge arrangement, it can be provided that these take place either successively during the stacking process or alternatively after reaching the defined stack height. An advantageous embodiment of the process provides that the surrounding areas of the previously removed filling nozzles of the sealing material are treated for an activation period t A2The sealing material is preferably cured using UV radiation. A curing process using UV radiation is advantageous in that it does not introduce heat into the adjacent materials. Alternatively, however, a targeted and locally directed thermal curing process could also be used. Curing can also occur gradually during the stacking process or after the defined stack height has been reached.

[0015] An advantageous embodiment of the method provides that the surrounding areas of the previously removed filling nozzles are removed from a direction substantially transverse to the stacking direction R SThis allows the bipolar electrode units to be stacked up to their defined stacking height, and the final hardening of the areas containing the filler necks can only take place at the end of the process from a lateral direction.

[0016] An advantageous embodiment of the method provides that the respective space enclosed by the sealing edge arrangement is evacuated via the filling nozzles before the electrolyte filling is introduced.

[0017] An advantageous embodiment of the method provides for the use of stainless steel cannulas as filling nozzles. Due to their properties, stainless steel cannulas are particularly well-suited for repeated use. In particular, the cannulas are intended to have a diameter of 0.3 mm to 0.4 mm.

[0018] An advantageous embodiment of the method provides for the filling nozzles to be pulled out of the respective sealing edge arrangements in their axial direction. This minimizes stress on the area of ​​the sealing edge arrangement from which the respective filling nozzle is pulled out, thus eliminating the risk of unnecessary widening of the through hole of the filling nozzle during the withdrawal process.

[0019] The invention will be explained below with further features, details, and advantages with reference to the accompanying figures. The figures illustrate merely exemplary embodiments of the invention. Fig. 1 a basic structure of a bipolar battery cell stack and the Fig. 2a) to 5b) Process steps for producing a bipolar battery cell stack.

[0020] The Fig. 1 shows a basic structure of a bipolar battery cell stack 1. The bipolar battery 1 extends in a stacking direction R S and comprises a recurring sequence of approximately rectangular, plate-shaped elements. Each of the plate-shaped elements extends in an extension plane perpendicular to the stacking direction R SThe recurring sequence of elements is formed by bipolar collectors 101, 102, ..., a first active material 121, 122, ..., separators 141, 142, ... and a second active material 161, 162, ... Four of these elements are shown here purely as examples, with a fifth bipolar collector 105 being provided. A collector base plate 26 is located below the bipolar battery cell stack 1, and a collector cover plate 28 is located above the bipolar battery cell stack 1. The collector base plate 26 and the collector cover plate 28 are preferably designed to be electrically conductive, for example as metal plates.

[0021] Within the bipolar battery cell stack 1, in the stack direction R Sconsiders a second active material 161, 162, ..., a bipolar collector 101, 102, ... and a first active material 121, 122, ... a so-called bipolar electrode unit 181, 182, ... Here, the bipolar collector 101, 102 consists of an electrically conductive material, preferably of aluminum, nickel, stainless steel, a corrosion-resistant copper alloy or corrosion-resistant nickel alloy or a bimetal made of two of the above-mentioned materials or one of the above-mentioned and copper. The bipolar battery cell stack 1 further comprises respective between adjacent bipolar electrode units 181, 182, ... extending in the stacking direction R Sextending and lying in the expansion plane seals 201, 202, .... Each seal 201, 202, ... lies between the bipolar collectors 101, 102, ... of the adjacent bipolar electrode units 181, 182, .... An electrolyte filling (not shown in detail) is held in an electrolyte chamber 241, 242, ... between the bipolar collectors 101, 102, ... and the seals 201, 202, .... Thus, an electrochemical cell is formed between the respective bipolar collectors 101, 102, ... via the two active materials 121, 122, ..., 161, 162, ... and the electrolyte filling. The electrochemical cell is hermetically sealed from the environment via the respective seal 201, 202, ....

[0022] Each seal 201, 202,... is secured by a SA sealing edge arrangement 221, 222, ... is formed. For the sealing edge arrangement 221, 222, ... of the seals 201, 202, ..., a sealant / adhesive that can be crosslinked by UV radiation can be used as the sealing material. Preferably, the respective separator 141, 142, ... projects beyond the first active material 121, 122, ... and the second active material 161, 162, ... in the expansion plane and is at least partially received in the respective seal 201, 202, ... with this projection.

[0023] The Fig. 2a) to 5b) show the process steps for producing a bipolar battery cell stack 1. The process is described only using the most important process steps, but all intermediate steps not described in detail are also intended to be included. Furthermore, no devices or systems are described by which the individual elements of the bipolar battery 1 can be handled during the production process. Fig. 2a) is representative for all further representations a stacking direction R S symbolized by an arrow, which in this case points vertically upwards. This vertical direction is purely for the sake of simplicity and can also point in another spatial direction.

[0024] The Fig. 2a) initially shows a pre-assembled unit consisting of a collector base plate 26, a bipolar collector 101, and a first active material 121. This pre-assembled unit can, for example, be manufactured in one or more preceding manufacturing steps. The pre-assembled unit is placed in a suitable stacking station and prepared there for the subsequent process steps. Fig. 2b) shows the next or one of the next process steps, in which the sealing material of the sealing edge arrangement 221 is applied to the lowermost bipolar collector 101. Here, the sealing material is applied around the first active material 121. It may be provided that the sealing material is applied in a single application process as a single bead of material or, alternatively, that a multiple application process takes place, wherein the required amount of sealing material is applied by applying several beads of material multiple times.

[0025] The Fig. 2c) shows the next or one of the next process steps, in which a tubular or cannula-like filling nozzle 301 is inserted into the sealing material of the sealing edge arrangement 221 in order to evacuate the electrochemical cell via this nozzle in a later process step and subsequently fill it with an electrolyte. The filling nozzle 301 can be introduced into the sealing material in various ways, which is symbolized by the horizontally inward-pointing arrow. For example, it is conceivable that the filling nozzle 301 is pierced through the sealing material from the side in its axial direction.Alternatively, it is also conceivable that the sealing material, as already described, is applied in a multiple application process over several material beads, and that the filling nozzle 301 is placed on the already applied sealing material between the application of two material beads and is enclosed by the subsequently applied material beads. It is crucial for the filling nozzle 301 that it extends so far into the interior of the bipolar electrode unit 18 that it pierces the sealing material and ends in the electrolyte chamber 241.

[0026] The Fig. 3a) shows the next or one of the next process steps, in which the separator 141 is inserted essentially vertically from above onto the first active material 121 and at the edge into the sealing material of the sealing edge arrangement 221. The Fig. 3b) shows the next or one of the next process steps, in which a bipolar electrode 181, consisting of the two active materials 122, 161 and a bipolar collector 102, is placed on the already placed separator 141 and the applied sealing material of the sealing edge arrangement 221, which is preferably done vertically from above and is symbolized by the two arrows pointing vertically downwards. By placing a bipolar electrode 18, an electrolyte chamber 241 is created. Fig. 3c) shows the next or one of the next process steps, in which the sealing material of the sealing edge arrangement 221 is activated and cured by means of a UV radiation source 32. This curing process by means of the UV radiation source 32 can continue until the sealing material has become hard enough for processing. The period of this curing can be referred to as the activation period t A1The decisive factor here is that a shading device 34 is provided for the UV radiation source 32, so that the shading device 34 can be used to specifically exclude the UV radiation from the sealing edge arrangement 22. According to the invention, the area of ​​the sealing edge arrangement 22 into which the filling nozzle 301, 302, ... was previously inserted is excluded from UV radiation. The aim is to use the shading device 34 to ensure that the area of ​​the sealing edge arrangement 22 through which the filling nozzle 301, 302, ... passes does not harden or is kept flexible, so that in a later method step the filling nozzles 301, 302, ... can be removed from the sealing edge arrangement 221, 222, ... without damaging or impairing it, as will be described later.In particular, the shading device 34 can be designed to be largely freely movable relative to the UV radiation source 32. Thus, the shading device 34 can also be completely removed from the beam path of the UV radiation.

[0027] For the purpose of simplified representation, the Fig. 4a), after the defined stack height has been reached, the placement of a likewise preconfigured unit, consisting of a second active material 16 n , a bipolar collector 10 n and a surge arrester cover plate 28. The Fig. 4b) finally shows a method step in which the electrochemical cells of the bipolar battery cell stack 1 are first evacuated via the filling nozzles 301, 302, ... and then the respective electrolyte chamber 241, 242 is provided with an electrolyte filling.

[0028] The Fig. 5a) shows the next or one of the next process steps, in which the filling nozzles 301, 302, ... are removed from the sealing edge arrangement 32, which is symbolized by the horizontally outwardly directed arrow. It is preferred that the filling nozzles 301, 302, ... be pulled out of the sealing edge arrangement 32 in their axial direction by a suitable gripping device. Because the area of ​​the sealing edge arrangement 22 from which the respective filling nozzle 301, 302, ... was removed was not previously hardened, the sealing material is still sufficiently flexible so that the opening remaining after the removal of the filling nozzle 301, 302, ... can close. Fig.5b) shows the next or one of the next process steps, in which the not yet cured areas of the sealing edge arrangement 22, from which respective filling nozzles 301, 302, ... have been removed, are cured by UV irradiation by the UV radiation source 32. Each of these areas can be cured over an activation period t A2 be cured. In this case, it can be provided that the UV radiation source 32 is rotated such that its beam path is directed essentially horizontally and the UV irradiation occurs largely from the side in a horizontal direction onto the sealing edge arrangement 22. Additionally, it can be provided that the UV radiation source 32 can be moved in a vertical direction so that the areas of the sealing edge arrangement 32 that still need to be cured can be reached continuously. The vertical mobility is symbolized by the vertical double arrow. List of reference symbols 1 bipolar battery cell stack 101, 102, bipolar collector 121, 122, active material 141, 142, separator 161, 162, active material 181, 182, bipolar electrode unit 201, 202, sealing 221, 222, seal edge arrangement 241, 242, electrolyte chamber 26 arresters 28 arresters 301, 302, filling nozzle 32 UV radiation source 34 Shading device R S Stacking direction

Claims

[1] Method for producing a bipolar battery cell stack (1), comprising the method steps that - Bipolar collectors (101, 102, ...), - a first active material (121, 122, ...), - separators (141, 142, ...) and - a second active material (161, 162, ...), are stacked alternately, so that in a stacking direction R S growing bipolar battery cell stack (1) is formed until a defined stack height is reached, wherein adjacent first active material (121, 122, ...) and second active material (161, 162, ...) with the respective bipolar collector (101, 102, ...) arranged therebetween forms a bipolar electrode unit (181, 182, ...) and between adjacent bipolar electrode units (181, 182, ...) a between the respective bipolar collectors (101, 102, ...) in the stacking direction R Sextending and lying in the plane of extension sealing edge arrangement (221, 222, ...) is applied for sealing, wherein - sealing material of the sealing edge arrangement (221, 222, ...) is applied to the respective bipolar collector (101, 102, ...), - at least one filling nozzle (301, 302, ...) and the respective separator (141, 142, ...) are inserted into the sealing material, - the sealing material, excluding the area of ​​the sealing material surrounding the filling nozzle (301, 302, ...), over an activation period t A1 is cured to produce seals (201, 202, ...) between the respective bipolar collectors (101, 102, ...) of adjacent bipolar electrode units (181, 182, ...) by the cured sealing material of the sealing edge arrangements (221, 222), - an electrolyte filling is filled via the filling nozzles (301, 302, ...) into the respective space enclosed by the sealing edge arrangement (221, 222, ...) and - the filling nozzles (301, 302, ...) are removed from the respective sealing edge arrangements (221, 222, ...). [2] Method for producing the bipolar battery cell stack (1) according to claim 1, characterized by that the surrounding areas of the previously removed filling nozzles (301, 302, ...) of the sealing material each have an activation period t A2 be hardened. [3] Method for producing the bipolar battery cell stack (1) according to one of claims 1 to 2, characterized by that the electrolyte filling is filled via the filling nozzles (301, 302, ...) after the defined stack height has been reached and the filling nozzles (301, 302, ...) are then removed from the respective sealing edge arrangements (221, 222, ...). [4] Method for producing the bipolar battery cell stack (1) according to one of claims 1 to 3, characterized by that the sealing material is cured by UV radiation. [5] Method for producing the bipolar battery cell stack (1) according to one of claims 1 to 4, characterized by that the surrounding areas of the previously removed filling nozzles (301, 302, ...) are formed from a direction substantially transverse to the stacking direction R S direction of action. [6] Method for producing the bipolar battery cell stack (1) according to one of claims 1 to 5, characterized by that the respective space enclosed by the sealing edge arrangement (221, 222, ...) is evacuated via the filling nozzles before the electrolyte filling is introduced. [7] Method for producing the bipolar battery cell stack (1) according to one of claims 1 to 6, characterized by that stainless steel cannulas are used as filling nozzles (301, 302, ...). [8] Method for producing the bipolar battery cell stack (1) according to one of claims 1 to 7, characterized by that the filling nozzles (301, 302, ...) are pulled out in their axial direction from the respective sealing edge arrangements (221, 222).

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