DE102017207169A1 - cell stack - Google Patents

Abstract

The invention relates to a cell stack (1) comprising electrode layers (2) of a first type and electrode layers (4) of a second type, which are spaced apart by separator layers (3), the electrode layers (2, 4) each having a layer provided with electrochemically active material the first part (8) and a second part not provided with electrochemically active material, the second part not provided with electrochemically active material forming a current conductor (6) for the electrode layer (2, 4), the electrode layers (2, 4) and the separator layers (3) are arranged with respect to a stacking direction (s) such that the first parts (8) provided with electrochemically active material come over one another and form an electrochemically active region (10) of the cell stack (1) and wherein the current conductors (6 ) to the electrode layers (2, 4) of a type on top of each other and form a joining region (12) of the cell stack (1), wherein the current conductor (6) are each electrically connected to the electrode layers (2, 4) of a type in the joining region (12). It is provided that the current conductors (6) in the joining region (12) are formed or reshaped such that they form a joining structure there, wherein the joining structure with respect to the stacking direction (s) is made thicker than the sum of the individual film thicknesses of the current conductors ( 6).

Description

The invention relates to a cell stack comprising electrode layers of a first type and electrode layers of a second type, which are spaced apart by separator layers.

State of the art

Out US 2013/0011720 A1 Such a cell stack is known, which comprises electrode layers of a first type and electrode layers of a second type, which are spaced apart by separator layers. The electrode stack has an electrically conductive terminal, which receives and aligns the current conductors of the individual electrodes of one type.

US 2015/0111091 A1 discloses light absorbing components which are placed on or below surfaces of current conductors to space the current conductors apart.

It is an object of the invention to minimize the space requirement for the joint for the current conductors of the electrodes in a cell stack, to allow a uniform heat dissipation through the electrodes and to produce a joining geometry, which can be finally joined by a variety of different methods, preferably also using non-thermal joining methods.

Disclosure of the invention

An inventive cell stack comprises electrode layers of a first type and electrode layers of a second type, which are spaced apart by separator layers. Such a cell stack is also referred to as a stacked cell. The cell stack is built up in layers of electrode layers, alternating cathode layers and anode layers. Between cathodes and anodes are electrolytes, which may be, for example, liquid, gel, powder or solid. This structure provides a high interface, which on the one hand causes a high capacity of the battery, on the other hand, a space-saving arrangement. In order to ensure the function of the battery, the anode and cathode layers are each electrically combined.

The electrode layers are preferably designed as partially coated with electrochemical material films and thereby each have a provided with electrochemically active material first part and a non-electrochemically active material provided with the second part, which is not provided with electrochemically active material second part of a current conductor for forms respective electrode layer.

The electrode layers and the separator layers are arranged with respect to a stacking direction such that the first parts provided with electrochemically active material come over one another and form an electrochemically active region of the cell stack. The current conductors to the electrode layers of one type also come on top of each other and form joining areas of the cell stack. In the joining regions, the current collectors are electrically connected to the electrode layers of one type each, so that electric charge and heat generated during charging and discharging can be effectively dissipated.

Furthermore, it is provided that the current conductors in the joining region are formed or reshaped such that they form a joining structure there, wherein the joining structure is made thicker with respect to the stacking direction of the cell stack than the sum of the individual foil thicknesses of the current conductors. In other words, a total thickness of the current conductors in the joining region is greater than the sum of all individual film thicknesses of the uncoated electrode layers.

Thus, the area between two electrode layers of the same type is at least partially filled in volume. Thus, the joining region with respect to the stacking direction is thinner or thicker than the electrochemically active region of the cell stack, preferably of the same thickness as the electrochemically active region of the cell stack.

The gap occurring in the layer structure of the films to be joined is filled with material. The distance between the foils to be joined is filled or bridged, which is preferably done not with the help of other components, but with the help of the electrode layers themselves, namely with the help of the current conductor of the respective electrode layers. As a result, a complicated and spatially greatly expanded merging the individual slides is obsolete.

By this arrangement, the space required for merging the individual films can be reduced. The result is a planar heat conductor, through which the heat can be dissipated uniformly.

According to a preferred embodiment, the current conductors have identical dimensions to the electrodes of one type in the electrode stack. As a result, different lengths of connections between the end of the electrochemically active electrode and the joint are avoided, which otherwise leads to uneven temperature dissipation and temperature gradients within the cell, which adversely affect the capacity and the life of the battery. The thermal resistance of each current conductor in the electrode stack is therefore substantially the same.

According to a preferred embodiment, each two successive provided with electrochemically active material first parts of the electrode layers of the same type at a defined distance from each other. Due to the equidistant arrangement, different joining methods can be used for the final joining, for example methods such as pressing, pressing, forming or welding.

The current conductor can z. B. be designed in the manner of flags and stick out of the electrochemically active area.

According to a preferred embodiment, the joining regions of the current conductors to the electrode layers of both types are formed as disjoint regions. It may, for example, be provided that the current conductors to the electrode layers of both types protrude from the electrochemically active region opposite one another, or that they are arranged, for example, over the corner, for example at a right angle to one another. Alternatively it can be provided that the current conductors protrude to the electrode layers of one type on the same side but at opposite edges.

According to one embodiment, the current conductors have thickenings in the joining region which form the joining structure. The thickenings are designed so that the distance between the electrode layers in the region of the current conductor is greater than the sum of the individual foil thickness of the current conductor, preferably the same size as in the electrochemically active region. It can be provided that the thickening, for example, two to ten times the thickness of the electrode layer, d. H. either the thickness of the film or the thickness of the film with the active material, or for example, two to five times. The thickenings may extend flat or be present in sections. There may be one thickening or several thickenings per electrode layer. The thickenings can over the length, d. H. be in a direction of extension of the electrode layer, constant or variable. One or more thickenings may be provided per electrode layer.

The current conductors have in the joining region according to an embodiment on convolutions. Here, both compressed, d. H. subsequently pressed, folds be provided as well as loose folds. The convolutions can be generated in the same direction, also referred to as rolling convolutions, or generated in different directions, i. H. alternately, also referred to as zig-zag folds. The folds can be defined in sections or over the entire length, and more complex folds can be provided, in particular origami folds. One or more folds can be provided per electrode layer.

According to one embodiment, the current conductors in the joint area on reels. The reels can be compacted, i. H. be subsequently pressed, rolled up or loose curls, extend over one or more areas and be formed constant or variable over the length. One or more rolls can be provided per electrode layer.

According to one embodiment, spacer elements are arranged in the joining region between the electrode layers of the same type. The spacer elements can be made, for example, from a different material than the current conductors and be designed to be electrically conductive or electrically insulating. The spacers may have other physical properties and / or be used for monitoring and diagnostic purposes of the cell.

According to one embodiment, foils of two successive electrode layers of the same type are integrally formed with each other. In this case, the electrode layers of the same type are reshaped so that the electrode layers of the other type can be interposed therebetween, respectively. The deformation can z. B. by folding, but also by bending or rolling. In particular, it can be provided in this embodiment that spacing elements are arranged in the forming area.

According to a preferred embodiment, the electrode layers are formed as anodes and cathodes of a lithium-ion cell. Alternatively, the battery cells may be formed as nickel metal hydride battery cells. The terms "battery" and "battery cell" are used in the present description, the usual parlance used for battery or accumulator cell. The battery cell can be designed, for example, as a pouch cell or as a hard-case cell, although this is not restrictive.

The cell stacks are preferably spatially combined and interconnected in terms of circuitry into larger structures, for example connected in series or in parallel to a battery module or battery pack in order to provide the required power.

Applications of the cell stack may be in particular electric vehicle batteries, hybrid vehicle batteries or battery systems in general, which are modular and use a plurality of battery cells as energy storage.

Advantages of the invention

The invention makes it possible to minimize the space required for the joint for the current conductors of the electrodes and at the same time to allow a uniform heat dissipation via the electrodes. A complicated and spatially greatly expanded merging of the individual films or electrode layers is obsolete. The distance between the electrochemically active material provided with the first part of the electrode layer to the joining zone is the same for all electrode layers, which produces a uniform removal of heat.

The proposed structure improves the volumetric capacity (capacity per volume) of the cell stack.

By avoiding connections of different lengths between the end of the electrochemically active regions of the electrode layers and the joint, uneven temperature discharges of the individual electrode layers are avoided. Thus, the capacity and the life of the battery are improved. Temperature gradients from electrode layer to electrode layer are thus largely minimized.

The invention also provides a joining geometry which is compatible with a variety of different joining methods, such as welding, but also with non-thermal joining methods, eg. B. pressing, pressing, or forming.

list of figures

• 1 eine schematische Darstellung eines Zellenstapels in seitlicher Schnittansicht,
• 2 eine schematische Darstellung eines Zellenstapels in perspektivischer Ansicht,
• 3 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß dem Stand der Technik,
• 4 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß dem Stand der Technik,
• 5 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß dem Stand der Technik in seitlicher Schnittansicht,
• 6 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß einer ersten Ausführungsform der Erfindung in seitlicher Schnittansicht,
• 7 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß einer zweiten Ausführungsform der Erfindung in seitlicher Schnittansicht,
• 8 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß einer dritten Ausführungsform der Erfindung in seitlicher Schnittansicht,
• 9 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß einer vierten Ausführungsform der Erfindung in seitlicher Schnittansicht,
• 10 eine schematische Darstellung eines Fügebereichs eines Zellenstapels gemäß einer fünften Ausführungsform der Erfindung in seitlicher Schnittansicht.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it

• 1 a schematic representation of a cell stack in lateral sectional view,
• 2 a schematic representation of a cell stack in perspective view,
• 3 a schematic representation of a joining region of a cell stack according to the prior art,
• 4 a schematic representation of a joining region of a cell stack according to the prior art,
• 5 a schematic representation of a joining region of a cell stack according to the prior art in a side sectional view,
• 6 a schematic representation of a joining region of a cell stack according to a first embodiment of the invention in a side sectional view,
• 7 a schematic representation of a joining region of a cell stack according to a second embodiment of the invention in a sectional side view,
• 8th a schematic representation of a joining region of a cell stack according to a third embodiment of the invention in a sectional side view,
• 9 1 is a schematic representation of a joining region of a cell stack according to a fourth embodiment of the invention in a lateral sectional view;
• 10 a schematic representation of a joining region of a cell stack according to a fifth embodiment of the invention in side sectional view.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar components and elements are denoted by the same or similar reference numerals, wherein a repeated description of these components or elements is dispensed with in individual cases.

The figures illustrate the subject matter of the invention only schematically.

1 shows an example of a cell stack 1 in lateral sectional view. The cell stack 1 includes here by way of example three electrode layers 2 a first type and three electrode layers 4 of a second type, which passes through five separator layers 3 spaced apart from each other.

Every electrode layer 2 . 4 has a first part provided with electrochemically active material 8th on and a not provided with electrochemically active material second part, which in the following as a current conductor 6 referred to as. Typically, the electrode layer comprises 2 . 4 in the case of lithium-ion cells as anodes, copper foils which are current conductors 6 form and which in provided with electrochemically active material first part 8th may be coated with any anode active material. The cathode typically comprises the first part provided with electrochemically active material 8th an aluminum foil coated with a cathode active material.

From the side sectional view shows that the cell stack 1 an electrochemically active region 10 in which the first parts provided with electrochemically active material 8th come together, as well as joining areas 12 , which are arranged opposite to each other in the illustrated embodiment, and in which the current collector 6 come over each other.

The in 1 illustrated cell stacks 1 is built up so regularly that in each case two electrode layers 2 . 4 of the same type is a constant distance d in the stacking direction n, ie, can be assigned to the layer arrangement as normal.

2 shows an alternative embodiment of the cell stack 1 in which the joining areas 12 not as related to 1 described and illustrated on opposite sides of the electrochemically active region 10 stand out, but on the same side. In this case, the joining areas 12 nevertheless spatially separated from each other so that there is an open space between them 5 is provided. The separator layers 3 are not shown in this and the following figures.

The joining areas 12 the current conductor 6 to the electrode layers 2 . 4 Both types are formed as disjoint areas that are separated from each other by the clear width 5 are spaced.

The between the individual electrode layers 2 . 4 occurring distances are usually bridged by a certain number of electrode layers 2 . 4 summarized and then joined. This creates a large space between the end of the electrochemically active electrode surface and the actual joint 14 as related to 3 and 4 is described.

In 3 is for example a cell stack 1 shown in which ten electrode layers 2 , Here and below by way of example electrode layers of the first type, via a joint 14 are connected. The dissipation of heat one centered in the cell stack 1 arranged electrode layer (a) is different from one below in the cell stack 1 arranged electrode layer (b).

In 4 an alternative embodiment is shown, wherein in the joining area 12 three electrode layers each 2 . 4 be joined together. The heat dissipation is more uniform under the electrode layers 2 . 4 but not optimal.

5 shows a part of a cell stack 1 , in principle, from the above US 2015/0111091 A1 is known. The electrode layers 2 . 4 each have a first part provided with electrochemically active material 8th and a current collector 6 on. The first parts provided with electrochemically active material 8th come in the electrochemically active area 10 on top of each other, and the current collector 6 come in the joining area 12 one above the other. Between the electrode layers 2 each of the first type is a spacer 16 arranged, which is the distance between the two successive electrode layers 2 of the first type bridged. The spacer element 16 For example, as a square in cross-section formed spacer 16a , as a cross-sectionally round spacer element 16b or as a triangular in cross-section spacer 16c be educated. Alternatively, the spacer element 16 also be elliptical in cross-section or generally N-shaped, where N is an integer. The spacers 16 For example, they may be in the form of wire, tape, stencils or pieces.

In 6 to 10 are embodiments of a cell stack according to the invention 1 shown, where the current collector 6 in the joining area 12 are formed or formed so that they form there a joint structure, which is thicker in relation to the stacking direction n than the sum of the thicknesses of the electrode foils of the current collector 6 , The joining structure is preferably at least as thick as the electrochemically active region 10 educated. The related to 5 described spacers 16 are optionally included in the embodiments.

6 shows a cell stack 1 according to a first embodiment of the invention. In the illustrated embodiment, an electrode layer 2 first type around a spacer element 16 turned over, so that a forming area 18 forms. The forming areas 18 serve as a joint structure. The spacers 16 are optional, that is the electrode layer 2 of the first type can also without a spacer 16 be turned down.

The forming area 18 as well as the spacer elements 16 may be elliptical, round, square, rectangular, etc. In the illustrated embodiment, successive electrode layers are respectively 2 of the first type, more specifically, the films of these electrode layers 2 of the first type formed integrally with each other. The thickness of the forming area seen in the stacking direction n 18 may be smaller, equal or greater than the distance d, ideally equal to d.

7 shows a cell stack 1 according to a further embodiment of the invention, wherein the current conductor 6 in the joining area 12 folds 20 have, which serve as joining structures. The folds 20 For example, as zig-zag folds 20a or alternatively as roll-folds 20b be designed. It can be single or multiple folds 20 available. The folds 20 can be sharp or rounded. Also conceivable are rolled folds 20 and other mixed forms. The folds 20 can be condensed. The thickness of the folds seen in the stacking direction n 20 may be smaller, equal or greater than the distance d, ideally equal to d.

In the 8th illustrated embodiment includes current conductor 6 , which in the joining area 12 Rewinds 22 exhibit. The reels 22 for example, a round shape 22a or an elliptical shape 22b have or different forms. The reeling 22 can be condensed. The thickness of the reeling seen in the stacking direction n 22 may be less than, equal to, or greater than d, ideally equal to d.

9 shows a further embodiment of a cell stack 1 according to the present invention, wherein the electrode layer 2 . 4 at the respective end a loose fold 24 has, which serves as a joint structure. The loose fold 24 may include single or multiple folds, which may be formed sharp or rounded. Conceivable are zig-zag folds, rolled folds, mixed forms or the like. The loose folds 24 can be precompacted. The loose folds 24 can lie asymmetrically on each other, as well as in foil 9 shown. Hierarchical loose folds 24 are conceivable. Also complex loose folds 24 may be used in this embodiment, for example origami folds. "Origami" folds are characterized by the fact that they have a high mechanical strength and stability at relatively low weight. The thickness of the loose fold seen in the stacking direction n 24 may be less than, equal to, or greater than d, ideally equal to d.

10 shows a further embodiment of the invention, wherein asymmetric electrode layers 2 of the first type, ie those which have at least one thickening at one end 26 exhibit. The thickening 26 which serves as a joining structure can be produced for example by a rolling process or by a deformation of the film. The thickness of the thickening seen in the stacking direction n 26 may be less than, equal to, or greater than d, ideally equal to d. The thickening 26 can vary in all spatial directions. The thickening 26 can occur abruptly or be designed as a transition. The thickening 26 can be linear or in any function. Tapering is also conceivable, especially in the context of non-monotonous thickening 26 ,

As further embodiments, combinations of the above embodiments are possible, for. For example, the cathodes may be designed differently than the anodes, or else any or every other electrode layer 2 . 4 different.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2013/0011720 A1 [0002]
• US 2015/0111091 A1 [0003, 0040]

Claims (10)

Cell stack (1) comprising electrode layers (2) of a first type and electrode layers (4) of a second type which are spaced apart by separator layers (3), the electrode layers (2, 4) each having a first part (8) provided with electrochemically active material ) and a second part not provided with electrochemically active material, the second part not provided with electrochemically active material forming a current conductor (6) for the electrode layer (2, 4), the electrode layers (2, 4) and the separator layers ( 3) are arranged with respect to a stacking direction (s) such that the first parts (8) provided with electrochemically active material come over one another and form an electrochemically active region (10) of the cell stack (1), and wherein the current conductors (6) to the electrode layers (2, 4) of a type on top of each other and form a joining region (12) of the cell stack (1), wherein the current conductor (6) to the electrode layers (2 , 4) of a type in the joint area (12) are each electrically connected to each other, characterized in that the current conductors (6) in the joining region (12) are formed or reshaped to form a joint structure there, the joint structure with respect to Stacking direction (s) is formed thicker than the sum of the individual film thicknesses of the current collector (6). Cell stack (1) after Claim 1 , characterized in that the current conductors (6) to the electrode layers (2, 4) of a type in the electrode stack have identical dimensions, so that the thermal resistance of each Stromableiters (6) in the electrode stack is substantially the same. Cell stack (1) according to one of the preceding claims, characterized in that in each case two successive provided with electrochemically active material first parts (8) of the electrode layers (2, 4) have a defined distance from one another. Cell stack (1) according to one of the preceding claims, characterized in that the joining regions (12) of the current conductors (6) to the electrode layers (2, 4) of both types are disjoint regions. Cell stack (1) according to one of the preceding claims, characterized in that the current conductors (6) in the joining region (12) have thickenings (26) which form the joining structure. Cell stack (1) according to one of the preceding claims, characterized in that the current conductors (6) in the joining region (12) have folds (20, 24) and / or reels (22) which form the joining structure. Cell stack (1) after Claim 6 , characterized in that the current conductors (6) in the joining region (12) have compressed folds (20) and / or compressed reels (22) which form the joining structure. Cell stack (1) according to one of the preceding claims, characterized in that spacer elements (16) are arranged in the joining region (12) between the electrode layers (2, 4) of the same type. Cell stack (1) according to one of the preceding claims, characterized in that films of two successive electrode layers (2, 4) of the same type are formed integrally with each other. Cell stack (1) according to one of the preceding claims, characterized in that the electrode layers (2, 4) form anodes and cathodes of a lithium-ion cell.

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