DE102010055604A1 - Bipolar flat cell for use in lithium-ion battery utilized as energy storage unit of electric drive assembly of e.g. hybrid vehicle, has opening, and shell bottom formed in region of recess corresponding to housing frame edge - Google Patents

Abstract

The cell (2) has a housing side part (8), a cladding metal sheet (9), an opening, and a housing frame (7) formed by a housing. The housing is provided with a pressure relief device. The housing side part is formed as shell-shaped, and the housing frame comprises a recess (16) at a housing frame edge (15). A height of the housing frame edge is reduced through the recess, and a shell bottom is formed in a region of the recess corresponding to the housing frame edge. A set of arc-shaped raised formations is attached at another shell bottom (18). An independent claim is also included for a battery comprising a pole plate.

Description

The invention relates to a single cell for a battery according to the features of the preamble of claim 1. The invention further relates to a battery of a plurality of single cells according to the features of the preamble of claim 7.

Batteries, in particular high-voltage batteries for use in a vehicle, which have a multiplicity of individual cells connected in series and / or in series, are known from the prior art. In this case, the individual cells are generally arranged together with a control and / or monitoring electronics and a cooling device in a common battery housing. For the single cells different types are known and in use.

For example, a bipolar flat cell, which is also referred to below as a single cell, is known, which has a single cell housing, which is formed of two electrically and thermally conductive, substantially parallel opposite arranged Hüllblechen and arranged therebetween, edge peripheral and electrically insulating frame. The envelopes are electrically isolated from each other by the frame. At least part of the electrically insulating frame is made of a thermoplastic material and in particular plastic. The cohesive closure of the single cell or the connection of the Hüllbleche with the thermoplastic frame is achieved by means of known hot pressing process.

In this case, the cladding sheets, in particular made of a metal, are designed, on the one hand, as an electrical pole and, on the other hand, as a heat-conducting sheet. A heat arising during charging and discharging of the flat cell can be dissipated to the outside via the correspondingly thickened cladding sheets. The heat can be supplied to a cooling plate through which an air-conditioning coolant and / or a cooling liquid can flow. In the area of the cooling plate, the cladding can be angled parallel to the cooling plate by 90 ° in order to improve the heat conduction.

For electrically insulating the Hüllbleche of the cooling plate made of metallic material, an electrically insulating heat-conducting foil is arranged between Hüllblech and cooling plate.

Inside the single cell, cathode and anode foils coated with electrochemically active materials are combined to form an electrode foil stack, wherein the cathode and anode foils are electrically separated from one another by means of a separator. A respective edge region of the electrode foil stack is connected, for example, by welding to the cladding sheet forming the electrical pole.

A plurality of individual cells formed in this way can be arranged next to one another and parallel to one another to form a cell stack. In each case, two cladding sheets connected to an electrical pole abut each other, so that the respective two cladding sheets are electrically conductively and non-positively connected and the individual cells are connected in series.

At the respective ends of the cell stack formed in this way, electrically conductive pole plates are arranged, which are non-positively connected in each case to a cladding sheet and thus form the two high-voltage terminals of different polarity of the battery.

For non-positive and / or positive connection between the individual cells of the cell composite with each other and between the pole plates and the respective adjacent individual cells clamping elements are provided, such as the cell stack encircling straps and / or in the cell stack threaded tie rods by means of which the pole plates and the individual cells in a perpendicular to the cell stack extending axial direction are pressed together.

Overloading of the single cell or a short circuit can lead to an increased internal pressure within the single cell. In individual and unpressed individual cells, the cladding bumps already at a relatively small increase in the present within the individual cell internal pressure. If this increased internal pressure reaches a certain value, the cohesive connection between the cladding sheet and the frame is released due to a peel tension caused by the increased internal pressure.

In the cell stack in the cell stack by means of the clamping element and the pole plates axially compressed individual cells is pressed by the increase in internal pressure, the hot press connection between the frame and Hüllblech only on thrust, so that a release of the frame of the Hüllblech takes place only at high pressures.

The increased internal pressure must be relieved by exceeding a threshold value by controlled opening of the cell to prevent an exothermic chain reaction of the cell ("thermal runaway") and / or an explosion. For this purpose, the single-cell housing usually has a bursting device, a so-called venting opening, in which a part of the single cell housing surrounding the individual cell is weakened so as to form a predetermined breaking point. If the internal pressure reaches or exceeds the limit value, this bursts Single cell housing at the predetermined breaking point and gases can escape from the interior of the single cell.

In the US 2009/0098443 A1 a flat single cell is described, which has a predetermined breaking opening in the cell bottom.

The invention has for its object to provide an improved single cell for a battery with an integrated venting device and a comparison with the prior art improved battery of a plurality of single cells with integrated venting device.

The object is achieved by a single cell with the features of claim 1. With regard to the battery, the object is achieved by the features specified in claim 7.

Preferred embodiments and further developments of the invention are specified in the dependent claims.

In the individual cell with a housing formed from a housing side, a Hüllblech and a housing frame in which an electrolyte and an electrochemically active electrode foil stack are arranged, wherein the housing has an overpressure protection, according to the invention the housing side part is formed cup-shaped, wherein in a shell bottom of a cell interior groundbreaking raised formations are introduced and / or arranged on the shell bottom outside raised formations and / or the housing frame on at least one housing frame edge has a recess through which a height of this housing frame edge is reduced, wherein the shell bottom is formed in the region of the recess corresponding to the housing frame edge.

In single cells of a battery, in particular a lithium-ion battery, a temperature and an internal cell pressure in case of malfunction of the single cell, for example in the case of a short circuit or overcharge, increases considerably, since an electrochemically active mass, for example nickel oxide, contained in the individual cells is thermal is unstable and decomposes irreversibly above a certain temperature in an exothermic reaction. By this decomposition process, the single cell heats up even further and the internal cell pressure continues to rise. This can lead to such a single cell or a battery equipped with these single cells exploding and / or inflaming.

To prevent this, it is ensured by means of the inventive solution that a sealed seam of a single cell in a cell stack is not fully loaded with a resulting from the frictional arrangement of the individual cells in the cell stack mechanical pressure, so that the seal seam in case of concern a critical pressure in the cell interior can open.

Thus eliminates the need to insert a predetermined breaking point and / or bursting opening in the housing in the production of individual cells. As a result, a particularly cost-effective production of the individual cells is made possible in particular. In addition, the individual cells produced in this way have an increased mechanical robustness compared with single cells with burst openings, predetermined breaking points and / or partial weakening of the housing of the single cell.

Expediently, the raised formations are arranged in the region of a tensioning device, which compresses the individual cells arranged next to one another to form a cell stack. Thus, a frictional connection between the adjacent individual cells in the cell stack by means of the raised formations.

Particularly suitably, the raised formations are formed arcuate. Thus, the formations are formed corresponding to the clamping means or adapted to this.

Advantageously, the shell bottom is set back in the region of the recess with respect to the remaining shell bottom in the direction of the enveloping sheet to form a step-shaped edge.

Particularly advantageously, a sealing seam is subjected to a peeling stress in the case of a critical internal pressure in the cell interior, which causes a partial or sectional failure of the sealed seam and resulting pressure equalization of the cell interior with an environment of the individual cell. As a result, a critical internal pressure applied in the interior of the cell can be dissipated in a defined manner into the environment of the individual cell and bursting of the individual cell is reliably avoided.

In a particularly advantageous embodiment, the sealing seam may be formed in the region of the housing frame edge having the recess with a predefinable weakening. This makes it possible to specify at which point the sealed seam opens at a critical internal pressure present in the cell interior.

A battery comprises a plurality of individual cells connected electrically in series and / or in parallel, wherein the individual cells, in particular flat cells, are preferably arranged closely one behind the other and aligned parallel to one another. As a result, an optimal space-saving arrangement of the individual cells is achieved. Since cell poles of the individual cells lie on the housing side part and the cladding of the housing, the individual cells are preferably connected to one another by pressing together the housing side parts and the cladding sheets, wherein in each case a housing side part are contacted with a cladding sheet and have a different polarity, electrically connected to one another in series. In this way, an optimal contacting of the individual cells can be achieved and a production of the battery considerably facilitated.

In an advantageous embodiment, the individual cells are arranged side by side in the cell stack in such a way that the housing side part of a first single cell rests completely on a cover plate of an adjacent single cell, the recessless housing frame edges of the adjacent individual cells abutting one another. Due to the recess in a housing frame edge extending in the region of this recess sealing seam is not subjected to mechanical pressure of neighboring cells and can open freely in the cell interior adjacent critical internal pressure and reduce the internal pressure.

In a further advantageous embodiment, the individual cells are arranged side by side in the cell stack such that in each case the raised formations formed in the first housing side part of a first single cell abut against a cladding plate of an adjacent individual cell, so that the individual cells are arranged at a distance from one another in the cell stack. Thus, the frictional connection between the adjacent cells arranged in the cell stack is achieved by means of the raised formations, whereby the sealing seam of the single cell is not subjected to mechanical pressure of the neighboring cells and can open freely.

For electrical contacting of the battery, a pole plate is arranged at each end of the cell stack, with raised formations pointing in the direction of the adjacent individual cell being arranged on at least one of these pole plates. Thus, the pole plate is spaced from the adjacent single cell, whereby the sealed seam of Einzellzelle can open freely.

Such a trained battery is particularly suitable as energy storage unit of an electric drive unit of a motor vehicle. For example, the battery may be used in a hybrid vehicle or an electric vehicle.

Embodiments of the invention are explained in more detail below with reference to drawings.

Showing:

1 1 is a schematic exploded view of a cell stack of a plurality of single cells according to the prior art;

2 schematically a perspective view of a single cell according to the invention,

3 schematically a perspective view of a portion of a cell stack,

4 schematically a plan view of an individual cell according to the invention,

5 schematically a sectional view through an individual cell according to the invention 4 .

6 schematically a sectional view through an arched single cell according to 4 .

7 schematically a sectional view through an open single cell according to 4 , and

8th schematically a perspective view of an alternative embodiment of a single cell according to the invention.

Corresponding parts are provided in all figures with the same reference numerals.

In 1 is a schematic exploded view of a cell stack 1 from a plurality of single cells 2 represented according to the prior art. There are several single cells 2 , which are formed as Rahmenflachzellen and not shown separate Ventingöffnungen arranged side by side and electrically connected to each other in series. End of the cell stack 1 each is a pole plate 3 arranged, which is an electrical contacting of the cell stack 1 enable. The single cells 2 and the pole plates 3 are by means of a plurality of tie rods 5 , which in correspondingly shaped recesses 4 of the single cells 2 and the pole plates 3 are arranged, positively and / or non-positively coupled. On the appropriately shaped tie rods 5 is at the end of a conventional mother 6 screwed, whereby the individual cells of the cell stack are pressed together over the entire surface.

In 2 is a schematic perspective view of a single cell according to the invention 2 and in 3 is a schematic perspective view of a portion of a cell stack 1 from several individual cells according to the invention 2 shown. In 4 is a schematic plan view of the single cell according to the invention 2 shown. In 5 is a schematic sectional view through a Single cell according to the invention 2 according to 4 shown.

The single cell 2 For example, a lithium-ion cell comprises a housing frame 7 , a housing side part 8th and a wrapper 9 , One is the housing side part 8th The edge is completely encircling 10 on the housing side part 8th molded and opposite the cladding 9 Angled at right angles, so that the housing side part 8th is formed shell-shaped. Side cover 8th and cladding 9 are arranged substantially parallel to each other, wherein the cladding 9 by means of a circumferential sealing seam 11 with the housing side part 8th is connected form, material and / or non-positively. This is by housing side part 8th and cladding 9 a gas-tight closed cell interior 12 educated. Within the cell interior thus formed 12 is an electrode foil stack 13 arranged, which consists of a plurality of electrochemically active and stacked electrode films. The individual electrode films are separated from each other in a manner not shown by means of a separator. A plurality of pole contacts of the electrode foil stack 13 one polarity is to one arrester flag 14 summarized. A first arrester flag 14 the single cell 2 is by means of known material, force and / or positive connections and in particular a welded joint with the housing side part 8th electrically conductive connectable. A not shown further arrester flag of the single cell 2 is by means of known material, force and / or positive connections and in particular a welded joint with the cladding 9 electrically conductive connectable, so that in each case one pole of the single cell 2 on the housing side part 8th and another pole on the cladding 9 lies.

In the area of the sealed seam 11 is the case frame 7 the housing side part 8th arranged circumferentially. The enclosure encloses 7 by means of a respective housing frame edge 15 the single cell 2 edge. At least one frame border 15 is a recess 16 arranged, through which a height H of this housing frame edge 15 is reduced to a height G. In the area of this recess 16 in the frame border 15 is a shell bottom 17 of the housing side part 8th opposite the remaining shell bottom 18 in the direction of the cladding 9 recessed to form a step-shaped edge. The electrode foil stack 13 is by means of the arrester flag 14 on the recessed tray bottom 17 contacted.

Conventionally, they are the cell stack 1 arranged single cells 2 over the entire surface frictionally against each other. This is the sealed seam 11 subjected to mechanical pressure of neighboring cells. Due to the recess according to the invention 16 in the frame border 15 will be in the area of this recess 16 running seal 11 not subjected to mechanical pressure of neighboring cells.

In 6 is a schematic sectional view through a single vaulted cell 2 according to 4 shown. This is due to an increased internal pressure in the cell interior 12 the cover sheet 9 partially arched outward. Because the sealed seam 11 and whose environment is not subjected to mechanical pressure of neighboring cells, the cladding can 9 bulge. This causes the increased internal pressure in the cell interior 12 , which on the cover plate 9 especially in the area of the recess 16 acts, a peeling tension K on the sealed seam 11 , Exceeds the increased internal pressure in the cell interior 12 a predetermined limit, occurs a partial or sectional failure of the seal 11 one. This opens the seal 11 and thus the connection between the Hüllblech 9 and the housing side part 8th , This is the cell interior 12 in the direction of an environment of the single cell 2 opened, whereby a pressure balance of the cell interior with the environment of the single cell 2 is effected and the venting gases from the cell interior 12 be discharged into the environment of the single cell.

In 7 is a schematic sectional view through an open single cell 2 according to 4 shown. This was the seal 11 by the peel tension K, which by the applied critical internal pressure in the cell interior 12 caused, opened. The failure of the sealed seam 11 causes an opening 19 between the cover plate 9 and the housing side part 8th , Through this opening 19 can the critical internal pressure causing Ventinggase in the direction of R in the environment of the single cell 2 escape, whereby a pressure equalization is effected. This causes a rupture of the single cell 2 and / or an explosion avoided.

In other words, by the invention, a deformation space for the Hüllblech 9 allows, with this deformation space through the recess 16 the frame border 15 is created.

In 8th is a schematic perspective view of an alternative embodiment of the single cell 2 shown. Here are the bottom of the bowl 18 from the cell interior 12 groundbreaking raised formations 20 arranged or directly into the shell bottom 18 brought in. For example, the raised formations 20 in a conventional deep-drawing process for the production of the housing side part 8th directly into the shell bottom 18 of the housing side part 8th brought in. The raised formations 20 are preferably arcuate and in the region of the clamping device arranged. The formations protrude beyond this 20 the case frame 7 ,

This causes the formations 20 in the juxtaposition of single cells 2 to the cell stack 1 a spacing of the adjacent single cells 2 to each other, so that the adhesion and the electrical contact between the adjacent in the cell stack 1 arranged single cells 2 by means of the raised formations 20 takes place, causing the sealed seam 11 the single cell 2 not with mechanical pressure of the neighboring cells, in particular of the housing frame 7 , is loaded and can open freely.

In this embodiment of the invention are on at least one end of the cell stack 1 arranged pole plate 3 in the direction of the adjacent single cell 2 arranged facing raised formations. This is an unobstructed opening of the sealed seam 11 the end-side single cell 2 allows.

Particularly advantageously, an exposed individual cell according to the invention opens 2 which are not in a cell stack 1 installed and thus compressed, in one in the cell interior 12 adjacent critical internal pressure, which compared to a critical internal pressure of the cell stack 1 clamped single cell 2 is reduced. This will be at an exposed single cell 2 , which is not surrounded by a protective cover, for example, during production, transport and assembly, defined already reduced low internal pressures, resulting in a lower energy content of the venting gas and an immediate interruption of the thermal chain reaction results. In the cell stack 1 built and / or compressed single cells 2 , which are surrounded by a stable battery housing, which degrades pressure and temperature of the venting gases, open only at a higher critical internal pressure. Thus, a high robustness of the cell stack 1 formed battery allows against mechanical stress.

The cell stack 1 from a plurality of single cells 2 is not shown in detail to form a battery with a battery housing umbar.

LIST OF REFERENCE NUMBERS

1

cell stack

2

single cell

3

pole plate

4

recess

5

tie rods

6

mother

7

housing frame

8th

Side cover

9

skin panel

10

section

11

seal

12

Cell interior

13

Electrode foil stack

14

conductor lug

15

Housing frame edge

16

recess

17

recessed tray bottom

18

shell bottom

19

opening

20

formation

G, H

height

K

peel voltage

R

direction

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 2009/0098443 A1 [0013]

Claims (10)

Single cell ( 2 ) with one of a housing side part ( 8th ), a cladding sheet ( 9 ) and a housing frame ( 7 ), in which an electrolyte and an electrochemically active electrode foil stack ( 13 ), wherein the housing has an overpressure protection, characterized in that the housing side part ( 8th ) is formed shell-shaped, wherein in a shell bottom ( 18 ) of a cell interior ( 12 ) groundbreaking raised formations ( 20 ) are introduced and / or on the tray bottom ( 18 ) externally raised formations ( 20 ) are arranged and / or the housing frame ( 7 ) on at least one housing frame edge ( 15 ) a recess ( 16 ), through which a height (H) of this housing frame edge ( 15 ), the tray bottom ( 17 ) in the region of the recess ( 16 ) corresponding to the frame edge ( 15 ) is trained. Single cell ( 2 ) according to claim 1, characterized in that the raised formations ( 20 ) are arranged in the region of a clamping device, which the side by side to form a cell stack ( 1 ) arranged individual cells ( 2 ) pressed. Single cell ( 2 ) according to claim 1 or 2, characterized in that the raised formations ( 20 ) are arcuate. Single cell ( 2 ) according to claim 1, characterized in that the shell bottom ( 17 ) in the region of the recess ( 16 ) opposite the remaining tray bottom ( 18 ) in the direction of the cladding ( 9 ) is set back to form a stepped edge. Single cell ( 2 ) according to one of the preceding claims, characterized in that a sealed seam ( 11 ) between the housing side part ( 8th ) and the cladding sheet ( 9 ) at a cell interior ( 12 ) is applied with a peel stress (K), which is a partial or sectional failure of the sealed seam ( 11 ) and a resulting pressure equalization of the cell interior ( 12 ) with an environment of the single cell ( 2 ) causes. Single cell ( 2 ) according to one of the preceding claims, characterized in that the sealing seam ( 11 ) in the area of the recess ( 16 ) having housing frame edge ( 15 ) is formed with a predetermined weakening. Battery with a plurality of electrically connected in series and / or parallel single cells ( 2 ) according to one of claims 1 to 4. Battery according to claim 7, characterized in that the individual cells ( 2 ) so juxtaposed in the cell stack ( 1 ) are arranged, that in each case in the housing side part ( 8th ) of a first single cell ( 2 ) formed raised formations ( 20 ) on a cover plate ( 9 ) of an adjacent single cell ( 2 ), so that the individual cells ( 2 ) spaced apart in the cell stack ( 1 ) are arranged. Battery according to claim 7 or 8, characterized in that the end of the cell stack ( 1 ) each a pole plate ( 3 ) is arranged for electrical contacting of the battery, wherein at least one of these pole plates ( 3 ) in the direction of the adjacent single cell ( 2 ) pointing raised formations ( 20 ) are arranged. Battery according to claim 7, characterized in that the individual cells ( 2 ) so juxtaposed in the cell stack ( 1 ) are arranged, that the housing side part ( 8th ) of a first single cell ( 2 ) on a cover plate ( 9 ) of an adjacent single cell ( 2 ) is applied over the entire surface, wherein the housing frame edges ( 15 ) without recess of the adjacent single cells ( 2 ) abut each other.

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