Bipolar battery cell stack and method for its manufacture

Abstract

Method for producing a stack of bipolar battery cells (1), comprising alternating stacking of - Bipolar collectors (101, 102, ...), - a first active material (121, 122, ...), - Separators (141, 142, ...) and - a second active material (161, 162, ...), so that in stacking direction R S growing bipolar battery cell stack (1) oriented in a direction perpendicular to the stacking direction (R S ) the standing expansion plane extends in a plate-like manner until a defined stacking height is reached, wherein before each stacking of a bipolar electrode unit (181, 182, ...), each formed from one of the bipolar collectors with the first active material applied on one side and the second active material applied on the other side (101, 102, ...) - Sealing material of a first sealing edge arrangement (221, 222, ...) is applied to the respective bipolar collector (101, 102, ...), - the respective separator (141, 142, ...) is inserted into the sealing material, - the sealing material over an activation period t A1 is hardened, then - Sealing material of a second sealing edge arrangement (241, 242, ...) is applied to the first sealing edge arrangement (221, 222, ...) and - the sealing material of the second sealing edge arrangement (241, 242, ...) over a period of time t compared to the activation period A1 shorter activation period t A2 is hardened, the hardening of the sealing material results in the two sealing edge arrangements (221, 222, ..., 24) 1,242, ...) to seals between the respective bipolar collectors (101, 102, ...) of adjacent bipolar electrode units (181, 182, ...) so that an electrolyte filling can be retained within the space formed by the bipolar collectors (101, 102, ...) and the respective associated seal (201, 202, ...).

Description

[0001] The invention relates to a method for manufacturing a stack of bipolar battery cells 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, which can also be called bipolar batteries, are based on a bipolar principle known from the field of fuel cells. The bipolar collector is a metallic foil coated on both sides with active material to form a bipolar electrode assembly. The active material is imprinted with the properties of a negative electrode on one side of the bipolar collector and a positive electrode on the other side through appropriate material selection. The unit, consisting of a bipolar collector and the active material arranged or applied to both sides, can be called a bipolar electrode assembly.

[0003] A bipolar battery cell is created by arranging two bipolar electrode assemblies opposite each other with respect to their active materials. This means that the negative electrode of one bipolar electrode assembly is positioned in a plane relative to the positive electrode of the other, with a separator in between. A seal is required between adjacent bipolar electrode assemblies to ensure that the battery cell, formed by two halves of the bipolar electrode assemblies, can be filled with electrolyte and that this electrolyte is retained within each cell. This plane-like arrangement of bipolar electrode assemblies, also known as stacking, continues until a defined stack height is reached.

[0004] The bipolar battery cells are stacked on top of each other in a large, plate-like arrangement, ideally vertically, although this is not mandatory. 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 cell, considerably lowering electrical resistance and increasing efficiency. The battery cells can quickly release their stored energy and rapidly recharge it during a single charging cycle.

[0005] In the prior art, the sealing between adjacent bipolar electrode assemblies of the electrolyte filling in the battery cell is described as a problem. Applying this sealant during the production of the bipolar battery cell stack has proven problematic. Firstly, an incorrect application of the sealing material can cause the bipolar collectors, between which the sealing material is inserted, to contact each other, resulting in a short circuit in one of the bipolar battery cells. Secondly, a problem can arise during operation of the bipolar battery if the sealant applied between the bipolar collectors runs inwards, i.e., into the battery cell, so that it no longer adheres to the uppermost bipolar collector. Such a problem is described in US 2016 / 0104913 A1.Furthermore, in connection with bipolar batteries, the document DE 10 2014 210 803 A1 should be mentioned.

[0006] US Patent 2012 / 0171567 A1 discloses a method for manufacturing a stack of bipolar battery cells in which the edge seal between two adjacent bipolar electrode units is achieved by means of a circumferential, multilayered wall extending in the stacking direction. This wall consists of a thermosetting and a thermoplastic component. The opposing bipolar collectors are each directly coated with a layer of the thermosetting component, upon which a layer of the thermoplastic component then rests, either in or against the stacking direction. When two such modules of bipolar electrode units with the edge-applied, two-layered sealing wall are stacked, the two thermoplastic layers come into contact with each other, with the outer edge of a separator being clamped between their radially inner edges.During the subsequent hot pressing process, the thermosetting components harden, while the thermoplastic components melt superficially and bond together. This process is extremely complex and prone to errors, both in terms of mechanical design and chemically correct material selection, as well as temperature control. Furthermore, the required precise temperature control makes the production of larger stacks particularly difficult.

[0007] Based on this, the object of the present invention is to provide a simpler and less error-prone method for manufacturing a stack of bipolar battery cells, the sealing of which of the respective battery cells is stable over the long term and hermetically seals against an environment.

[0008] This problem is solved according to the invention by a method for producing a stack of bipolar battery cells (1), comprising an alternating stacking of - Bipolar collectors, - a first active material, - Separators and - a second active material, so that in stacking direction R S A growing stack of bipolar battery cells is formed, extending in a plate-like shape in an expansion plane perpendicular to the stacking direction, until a defined stacking height is reached. wherein before each stacking of a bipolar electrode unit, each formed from one of the bipolar collectors with the first active material applied on one side and the second active material applied on the other side - Sealing material of a first sealing edge arrangement is applied to the respective bipolar collector, - the respective separator is inserted into the sealing material, - the sealing material over an activation period t A1 is hardened, then - Sealing material of a second sealing edge arrangement is applied to the first sealing edge arrangement and - the sealing material of the second sealing edge arrangement over a period of time t compared to the activation period A1 shorter activation period t A2 is hardened, through the hardening of the sealing material, the two sealing edge arrangements become seals between the respective bipolar collectors of adjacent bipolar electrode units, so that an electrolyte filling can be retained within the space formed by the bipolar collectors and the respective associated seal.

[0009] Here, an activation period is defined as the timeframe during which the sealing material is subjected to a suitable curing process. This is distinct from the period during which the sealing material cross-links, triggered by prior activation, and fully cures. Ideally, the activation period should be no longer than the curing period. However, depending on the specific sealing material, the activation period can also be significantly shorter than the curing period, as rapid or accelerated curing is not always necessary or desirable.

[0010] A preferred embodiment of the process involves curing the sealing material by UV irradiation. UV curing is advantageous because it does not introduce heat into the adjacent materials. Alternatively, however, a targeted and locally directed thermal curing process could also be used.

[0011] A preferred embodiment of the method provides that, after the application of the sealing material to the first sealing edge arrangement, a filling support for subsequent evacuation and filling with an electrolyte is inserted into the sealing material.

[0012] A preferred embodiment of the method provides that the first bipolar collectors and the first active material to be stacked are supplied via a pre-assembled unit in conjunction with a conductor base plate.

[0013] A preferred embodiment of the method provides that a surge arrester cover plate is stacked on top once the defined stacking height is reached.

[0014] The invention is explained below with further features, details, and advantages with reference to the accompanying figures. The figures merely illustrate exemplary embodiments of the invention. Herein, they show Fig. 1: a basic structure of bipolar battery cell stacks; Fig. 2a) to 5b) Process steps for the production of a bipolar battery cell stack.

[0015] The Fig. Figure 1 shows a basic structure of a bipolar battery cell stack 1, which is also referred to as a bipolar battery in the following. The bipolar battery 1 extends in a stacking direction R. Sand comprises a repeating sequence of approximately rectangular, plate-shaped elements. Each of the plate-shaped elements extends in a plane of extension perpendicular to the stacking direction R. S The repeating 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 as purely exemplary examples, with one bipolar collector 105 being provided. A surge arrester base plate 26 is located below the stack of bipolar battery cells 1 and a surge arrester cover plate 28 is located above the stack of bipolar battery cells 1. The surge arrester base plate 26 and the surge arrester cover plate 28 are preferably electrically conductive, for example, made of metal plates.

[0016] Within the bipolar battery cell stack 1, R form in the stacking direction. S Each of the following is considered: a second active material 161, 162, ..., a bipolar collector 101, 102, ... and a first active material 124, 122, ... a so-called bipolar electrode unit 181, 182, ... Here, the bipolar collector 101, 102 consists of an electrically conductive material, preferably aluminum. The bipolar battery cell stack 1 further comprises respective connections between adjacent bipolar electrode units 181, 182, ... in the stacking direction R SThe seals 201, 202, ... extend and lie in the plane of expansion. Each seal 201, 202, ... is located between the bipolar collectors 101, 102, ... of the adjacent bipolar electrode units 181, 182, ... The bipolar collectors 101, 102, ... and the seals 201, 202, ... are held in an electrolyte filling (not shown in detail). 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 by the respective seal 201, 202, ...

[0017] Each seal 201, 202,... is formed by a first sealing edge arrangement 221, 222, ... and a sealing edge arrangement 221, 222, ... on the first sealing edge arrangement 221, 222, ... in the stacking direction R S constructive second seal edge arrangement 24 1,242, ... formed. The two seal edge arrangements 221, 222, ..., 24 are shown here. 1, 242, ... preferably adhesively bonded together, which is in the Fig. 1 is symbolized by the adjacent crosses. For the two sealing edge arrangements 221, 222, ..., 241, 242, ... of the seals 201, 202,... a UV-curable sealant / adhesive can be used as the sealing material. Preferably, the respective separator 141, 142, ... extends beyond the first active material 121, 122, ... and the second active material 161, 162, ... in the expansion plane and is at least partially incorporated into the seal 201, 202,... with this overhang.

[0018] The respective height of the first seal edge arrangement 221, 222, ... and second seal edge arrangement 24 1, 242, ... in stacking direction R Sdiffer preferably in that the height of the first seal edge arrangement 221, 222, ... is greater than the height of the second seal edge arrangement 24 1, 242, .... With otherwise the same height in the stacking direction R S For the first active material 121, 122, ... and the second active material 161, 162, ... this means that the first sealing edge arrangement 221, 222, ... extends beyond the first active material 121, 122, ... in height. This, in turn, leads to the respective separator 141, 142, ... being at least partially incorporated into the first sealing edge arrangement 221, 222, ... with its overhang in the plane of expansion above the first active material 121, 122, ... and the second active material 161, 162, ... . For the two sealing edge arrangements 221, 222, ..., 24 1,242, ... it is also conceivable that these have the same height in the stacking direction. If the two active materials 121, 122, ..., 161, 162, ... continue to have the same height in the stacking direction, this would mean that the respective separator 141, 142, ... is located in the transition area between the two sealing edge arrangements 221, 222, ..., 24 1, 242, .... is recorded.

[0019] The Fig. Figures 2a) to 5b) show the process steps for manufacturing a stack of bipolar battery cells 1. Although the process is described only by way of the most important process steps, all intermediate steps not described in detail are also implied. Furthermore, no devices or systems are described that could be used to handle the individual elements of the bipolar battery 1 during the manufacturing process. Fig. 2a) represents a stacking direction R for all other representations SThis is symbolized by an arrow, which in this case points vertically upwards. This vertical direction is merely for the sake of simplicity and can also point in a different spatial direction.

[0020] The Fig. Figure 2a) shows a pre-assembled unit consisting of a current collector base plate 26, a bipolar collector 101, and a first active material 121. This pre-assembled unit can be manufactured, for example, 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. Figure 2b) shows the next or one of the next process steps in which the sealing material of the first sealing edge arrangement 221 is applied to the lowest bipolar collector 101. Here, the sealing material is applied around the first active material 121, whereby it may be provided that the sealing material is applied as a single bead in a single application process, or alternatively, that multiple application processes take place, whereby the required amount of sealing material is applied by repeatedly applying several beadfuls of material. Fig. 2c) shows the next or one of the next process steps in which a tubular filling nozzle 301 is inserted into the sealing material of the first sealing edge arrangement 221 in order to evacuate the electrochemical cell via this in a later process step and then to provide it with an electrolyte filling.

[0021] The Fig. Figure 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 its edge into the sealing material of the first sealing edge arrangement 22. Fig. Figure 3b) shows the next or one of the next process steps, in which the sealing material of the first sealing edge arrangement 22 is activated and cured by means of a UV radiation source 32. This curing process using the UV radiation source 32 can continue until the sealing material has become hard enough for machining. The period of this curing can be referred to as the activation period t. A1 This means that the UV radiation source 32 remains in operation until the sealing material has reached sufficient toughness so that further build-up of the seal 20 can take place, as described below. Fig. Figure 3c) shows the next or one of the next process steps, in which the sealing material of the second sealing edge assembly 241 is applied to the already hardened first sealing edge assembly 221. Here, the sealing material is also applied around the first active material 121, but it extends beyond it. Just as described for the first sealing edge assembly 241, the sealing material of the second sealing edge assembly 241 can also be applied by a single application process of a single bead of material or, alternatively, by multiple application processes using several beads of material.

[0022] Preferably, the sealing material of the second sealing edge arrangement 241 is applied along the same circumferential contour as the sealing material of the first sealing edge arrangement 221.

[0023] The Fig. Figure 4a) shows the next or one of the next process steps, in which the sealing material of the second sealing edge arrangement 241 is activated by means of the UV radiation source 32. Here, activation means that the irradiation with the UV radiation source 32 initiates cross-linking within the sealing material to such an extent that further cross-linking and final curing of the sealing material proceed slowly on their own, so that the sealing material remains soft for a certain period of time. Depending on the properties of the sealing material, final curing then occurs after several seconds or even after a few minutes. Fig. 4b) 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 activated sealing material of the second sealing edge arrangement 241.

[0024] For the purpose of simplified presentation, the Fig. 5a), after the defined stacking height has been reached, the placement of a similarly pre-configured unit, consisting of a second active material 16 n , a bipolar collector 10 n and a surge arrester cover plate.28. The Fig.Figure 5b) shows a state of the bipolar battery cell stack 1 in which the electrochemical cells are first evacuated via the filling ports 301, 302, ... and then filled with electrolyte. In a subsequent process step, the outwardly projecting part of the filling port 301, 302, ... is cut off in a suitable manner, and the remainder of the filling port 301, 302, ..., which continues to be inserted into the seal 201, 202, ..., is sealed. Reference symbol list 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, Seal edge arrangement 26 drains 28 drains 301, 302, filling nozzle 32 UV radiation source RS Stacking direction

Claims

[1] Method for producing a stack of bipolar battery cells (1) comprising alternating stacking of - Bipolar collectors (101, 102, ...), - a first active material (121, 122, ...), - Separators (141, 142, ...) and - a second active material (161, 162, ...), so that in stacking direction R S growing bipolar battery cell stack (1) oriented in a direction perpendicular to the stacking direction (R S ) the standing expansion plane extends in a plate-like manner until a defined stacking height is reached, wherein before each stacking of a bipolar electrode unit (181, 182, ...), each formed from one of the bipolar collectors with the first active material applied on one side and the second active material applied on the other side (101, 102, ...) - Sealing material of a first sealing edge arrangement (221, 222, ...) is applied to the respective bipolar collector (101, 102, ...), - the respective separator (141, 142, ...) is inserted into the sealing material, - the sealing material over an activation period t A1 is hardened, then - Sealing material of a second sealing edge arrangement (241, 242, ...) is applied to the first sealing edge arrangement (221, 222, ...) and - the sealing material of the second sealing edge arrangement (241, 242, ...) over a period of time t compared to the activation period A1 shorter activation period t A2 is hardened, the hardening of the sealing material results in the two sealing edge arrangements (221, 222, ..., 24) 1,242, ...) to seals between the respective bipolar collectors (101, 102, ...) of adjacent bipolar electrode units (181, 182, ...) so that an electrolyte filling can be retained within the space formed by the bipolar collectors (101, 102, ...) and the respective associated seal (201, 202, ...). [2] Method according to claim 1, characterized by that the sealing material is hardened by UV irradiation. [3] Method according to any of the preceding claims, characterized by , that after the application of the sealing material of the first sealing edge arrangement (221, 222, ...) a filling support (301, 302, ...) is inserted into the sealing material for later evacuation and filling with an electrolyte filling. [4] Method according to any of the preceding claims, characterized by, that the first bipolar collectors (101, 102, ...) to be stacked and the first active material (121, 122, ...) to be stacked is provided via a pre-assembled unit in conjunction with a surge arrester base plate (26). [5] Method according to any of the preceding claims, characterized by , that upon reaching the defined stacking height a surge arrester cover plate (28) is stacked on top.

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