WO2014040791A1

WO2014040791A1 - Battery cell with a rupture disc integrated into a housing cover plate

Info

Publication number: WO2014040791A1
Application number: PCT/EP2013/065975
Authority: WO
Inventors: Oliver Gerundt; Andreas Eichendorf; Markus Feigl; Rene Deponte
Original assignee: Robert Bosch Gmbh
Priority date: 2012-09-14
Filing date: 2013-07-30
Publication date: 2014-03-20
Also published as: DE102012216479A1

Abstract

The invention relates to a battery cell, in particular a lithium-ion battery cell, in which the number of components can be reduced compared to conventional battery cells. In said battery cell, a metal housing, in which a winding element, two electrodes and electrolyte are accommodated, is sealed in a gas-tight and pressure-tight manner by means of a cover arrangement. The cover arrangement includes, inter alia, a cover plate (23) by means of which an opening in the housing is largely sealed. According to the invention, a predefined rupture region (31) that is less thick than the surrounding regions of the cover plate (23) is formed in said cover plate (23). Owing to this reduced thickness and aided, if necessary, by additionally further thinned weakened regions (35), the predefined rupture region (31) can be designed to burst when there is increased internal pressure in the housing of the battery cell. The predefined rupture region (31) and the weakened regions (35) can be produced by locally stamping a metal sheet used for the cover plate (23) so that the predefined rupture region (31) can be integral with the rest of the cover plate (23) and no additional components such a foil-like rupture disc need to be provided and installed.

Description

Description title

Field of the Invention The present invention relates to a battery cell, in particular a lithium-ion battery cell. The invention further relates to a motor vehicle with such a battery cell.

PRIOR ART Battery cells, sometimes also referred to as accumulator cells, serve for the chemical storage of electrically provided energy. Even today, battery cells are used to power a variety of mobile devices. In the future, battery cells will be used, among other things, to supply energy to mobile devices

Electric vehicles or hybrid vehicles, both on land and on water, or for stationary intermediate storage of electricity derived from alternative energy sources.

For this purpose, a plurality of battery cells is usually assembled into battery packs. In order to utilize an available package volume as efficiently as possible, primarily battery cells with a prismatic,

used for example a cuboid-like shape.

Because of their possible high energy density, thermal stability and lack of memory effect is used for demanding applications such as

Storage solutions for motor vehicles usually used a lithium-ion battery technology, which is currently being intensively developed due to the high economic importance of a future electric mobility.

There are already many different types of battery cells, in particular lithium-ion battery cells, and furthermore in particular battery cells with a prismatic shape. However, such conventional battery cells usually have a complex structure on, in which the assembly of the entire battery cell a variety of different items is used. Such a variety of parts with different shapes, functions and consisting of different materials requires the use of a variety of manufacturing technologies and equipment.

In addition, the large number of different individual components in the production of the battery cell must always be available in their entirety, which requires coordination of the production of the individual components and a suitable stocking. All of this can add to the increased cost of manufacturing the battery cell. Disclosure of the invention

With the aid of embodiments of the present invention, inter alia, the number of individual components necessary for assembling a battery cell can be reduced and / or an assembly of a battery cell can be simplified.

It is proposed a battery cell, in particular a lithium-ion battery cell having at least one winding element, an electrolyte, two current collector and a housing. The winding element consists of a wound stack of a first film coated with anode material, for example copper, a second film coated with cathode material, for example aluminum, and two plastic films serving as diaphragms. One of the current collector is electrically conductively connected, for example welded, to the first foil of the winding element. The second current collector is electrically conductively connected to the second foil of the winding element. The housing has a metallic container and a metallic one

Cover arrangement on. The container has an opening through which the Wckelelement and the two current collector can be introduced during the manufacture of the battery cell in the housing. The lid assembly is adapted to complete the opening of the container gas-tight and pressure-tight. For this purpose, the lid assembly, inter alia, a cover plate which can largely close the opening in the container and which for hermetically closing the housing with the

Container can be connected, for example by a weld. On the cover assembly, a feedthrough assembly is formed to pass electrically conductive contact assemblies, each in contact with one of the current collectors in the interior of the housing, out of the housing through the cover assembly. The proposed battery cell is characterized by in that the cover plate has a predetermined breaking area of reduced thickness, which is designed to burst at an increased internal pressure in the housing.

Embodiments of the battery cell according to the invention are based inter alia on the following ideas and findings:

In battery cells, the winding element with its stack of different metal foils and intervening diaphragms together with this stack wetting electrolyte for chemical storage of energy, the chemically stored energy can be provided by suitable chemical reactions at the electrodes in the form of electrical energy.

Owing to excessively strong chemical reactions, which may occur, for example, during overcharging of the battery cell or during a short circuit of the same, reaction gases may be released and thus an increase in pressure within the housing of the battery cell. In order to prevent bursting of the entire battery cell due to such a caused increase in pressure, on the housing a

Provision can be made, which can act as a pressure relief valve and releases gas from the same upon the occurrence of excessive internal pressure in the housing.

While in conventional battery cells, a pressure relief valve assembly is usually realized using additional, separate components, it is now proposed to realize such functionality by specifically forming the already provided in the cover assembly of the battery cell cover plate. This cover plate, which except for a few intended for certain purposes, small openings on the container of the

Battery housing provided large opening completely closes and is hermetically sealed to the container, should have a predetermined breaking range, which due to a locally reduced material thickness when an increased

Internal pressure can burst in the housing. In other words, the cover plate should be made so thin-walled in a partial area, that when an increased

Internal pressure can break the wall forming this area of the cover plate locally and gas can escape from the interior of the housing before it can lead to an uncontrolled increase in pressure and ultimately bursting of the entire housing and, for example, an uncontrolled explosive release of electrolyte from the housing , The predetermined breaking region is preferably integrally integrated in the cover plate. In other words, the cover plate together with the predetermined breaking range forms a single component, so that it is possible to dispense with the provision and mounting of separate components, for example a separate rupture disk.

In order to be able to produce the cover plate to be provided for the battery housing in one piece with the predetermined breaking region to be integrated therein, suitably suitable manufacturing methods can be used. For example, in the cover plate, the predetermined breaking area of reduced thickness can be formed by embossing, i. with the help of a pressure deformation of a cover plate forming sheet. In particular, a sheet metal forming the cover plate can be stamped in such a way that the predetermined breaking range results. During embossing, material can be pressedly displaced from the predetermined breaking area to be formed into adjacent areas of the cover plate, so that a thickening area arises in the cover plate around the finished breaking area, whose material thickness is greater than an average thickness of the cover plate outside this predetermined breaking area.

In other words, during the production of the cover plate in addition to any necessary punching and bending operations, an embossing process can be performed in which no material is finally removed from the cover plate but material is only displaced out of an area that will later form the predetermined breaking area, out to adjacent areas. By such a material displacement, the material thickness is significantly reduced in the predetermined breaking area, for example, less than half the thickness of the cover plate forming sheet, whereas in the adjacent

Thickening areas, the thickness of the cover plate is increased locally. For example, the cover plate may have an average thickness of more than 1 mm, preferably more than 1.5 mm, whereas the predetermined breaking area may only have a thickness of less than 0.5 mm, preferably less than 0.3 mm. This allows the

Predetermined breaking area in contrast to the relatively rigid stable cover plate, a reduced strength, similar to a thin film obtained.

In order to further specifically weaken the strength of the predetermined breaking region, line-like weakening regions having a smaller thickness than the average thickness of the predetermined breaking region can be provided in the predetermined breaking region. In other words, the predetermined breaking region at such line-like weakening regions may have a further reduced thickness, so that the predetermined breaking region upon occurrence of a Excessive internal pressure in the housing along these weakened areas ruptures, thus releasing an opening for the escape of gas from the housing.

In particular, by suitable choice of the geometry such as the depth of such weakening areas with respect to a surface of the remaining predetermined breaking area and / or the extension of the weakened areas along the surface of the

Breaking range can be influenced, which force is required to the

Rupture breaking area along the weakened areas burst. Of the

For example, the predetermined breaking range can be specifically designed to burst at an increased internal pressure in the housing of more than 5000 hPa.

The described possible features of the battery cell and configurations of the components of the battery cell, in particular the integrated design of a predetermined rupture disc acting in the cover plate of the housing of the battery cell, are particularly suitable for use in battery cells whose housing has a prismatic shape.

The cover plate provided with the integrated predetermined breaking region can bring several advantages both in the production of the battery cell and for the finished battery cell. For example, in the production of the battery cell, the mounting of an additional pressure relief valve assembly, for example, the welding of an additional, provided as a separate metallic component rupture disk, omitted. In particular, conventionally used welding processes can be dispensed with in this context. Even defects that may arise in such welding processes can be avoided. Due to the overall possible savings of components, the manufacturing process can be made simpler and cheaper.

The described features of the battery cell and embodiments of the components of the battery cell, in particular the cover plate, are particularly suitable for use in battery cells whose housing has a prismatic shape.

It should be noted that possible features and benefits of a

battery cell of the invention herein with reference to different ones

Embodiments are described. A person skilled in the art understands that the individual features can be suitably combined or exchanged with one another, to arrive in this way to further embodiments and possibly synergy effects.

Brief description of the drawings

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, wherein neither the description nor the

Drawings are to be construed as limiting the invention. Fig. 1 shows an exploded view of a lithium-ion battery cell.

Figure 2 shows a perspective view of a cover plate for a battery cell according to an embodiment of the present invention. FIG. 3 shows a perspective partial view of a cover plate for a battery cell cut off along the line B-B shown in FIG. 2, according to an embodiment of the present invention.

FIG. 4 shows a cross-sectional view along the line A-A shown in FIG. 2 of a cover plate for a battery cell according to an embodiment of the present invention

Invention.

FIG. 5 shows a motor vehicle with a battery according to an embodiment of the present invention.

The figures are only schematic and not to scale. Like reference numerals designate the same or similar features in the figures.

Embodiments of the invention

Fig. 1 shows a conventional lithium-ion battery cell in an exploded view. It can be seen that the battery cell consists of a plurality of individual components, which are kept separately and must be assembled consuming during manufacture. Only the understanding of

Embodiments of the invention necessary components and their features

described, a description of the remaining components of the battery cell is omitted. The battery cell 1 comprises a winding element 3 with a wound stack 5 of a copper foil coated with anode material and an aluminum foil coated with cathode material, and intervening plastic films serving as diaphragms.

For electrical contacting, the copper foil and the aluminum foil along the winding axis in the opposite direction slightly staggered stacked, so that the copper foil on a narrow side and the aluminum foil on a

slightly overhanging the opposite narrow side over a respective edge of the Wckelelements. To a protruding portion 4 of the copper foil, a current collector 7 made of copper is welded, so that this current collector is electrically connected to the anode of Wckelelements. To an opposite projecting portion of the aluminum foil, a second current collector 9 made of aluminum is welded to make electrical contact with the cathode of the winding element 3.

The winding element 3 provided with the two current collectors 7, 9 as well as a cover arrangement 15 are then introduced through an opening 14 into an upwardly open, cuboidal container 13. Subsequently, the opening 14 of the container 13 with a cover plate 23 of the lid assembly 15 is connected gas-tight and pressure-tight. Through an opening 26 in the lid assembly 15 in the container 13, a liquid electrolyte is filled, which thus comes into contact with the provided on the metal foils of the wakelelements anode and cathode materials, so that it to the

Interfaces to desired chemical reactions between these materials and the electrolyte and corresponding to the implementation of chemical energy into electrical energy and vice versa can come. The container 13 is formed of sheet metal to withstand, inter alia, the chemically aggressive electrolyte. The cover assembly 15 consists of a plurality of components. The components are needed to perform several different functions using the

Cover assembly 15 for the entire battery cell 1 to implement. For example, by means of the lid assembly 15, the container 13 should not only be sealed gas- and pressure-tight, but it should also contact arrangements 19 allow a connection between the interior of the container 13 and the external environment and thereby an electrical connection between each of the current collector 7, the 9th on the one hand and from the outside to be contacted contact elements 21 on the other hand.

For this purpose, the cover assembly 15, inter alia, a cover plate 23 which can be connected at its lateral edges tightly connected to an edge of the opening 14 of the container 13, for example by welding. In order to be able to withstand the electrolyte to be accommodated inside the container 13, this cover plate 23 usually consists of a metal. In the cover plate 23 a plurality of openings are provided, which serve different tasks.

For example, apertures 25 are provided through which components of the contact assemblies 19, such as one on a current collector 7, 9

attached pin 27 can pass through. Further, an opening 26 is provided through which electrolyte can be filled into the interior of the housing 11 after the container 13 has been closed with the cover plate 23.

In addition, other components such as a potential plate 17 are provided to electrically connect one of the contact assemblies 19 with the cover plate 23 and in this way the cover plate 23 and the associated with this container 13 to the same electrical potential as that with this contact arrangement 19 in

Connecting current collector 7, 9. The cover plate 23 also has a large opening 29. This opening 29 is closed by a rupture disk 28 designed as a separate component. The rupture disk is a component in the form of a thin metal foil, which is welded at its edge to the cover plate 23 in a region around the opening 29 around. The rupture disk 28 is in this case designed to avoid a dangerous overpressure within the housing 11 by the thin film of the rupture disk 28 breaks when a threshold pressure is exceeded and thus gas can escape from the housing 1 1 out.

Figure 2 shows a modified cover plate 23 for a battery cell according to a

Embodiment of the present invention. The cover plate 23 has, in addition to the openings 25 for performing the contact assemblies 19 and the opening 26 to Charging the electrolyte on a predetermined breaking area 31. The entire cover plate 23 including the predetermined breaking area 31 is formed from a metal sheet. Of the

Predetermined breaking region 31 is thereby produced by displacing material from this region into adjacent regions by means of an embossing process, so that the predetermined breaking region has a reduced thickness in comparison to an average thickness of the cover plate 23.

As shown, for example, in the perspective view of FIG. 3 partially cut away along the line BB of FIG. 2 and the cross-sectional view of FIG. 4 taken along the line AA of FIG. 2, the predetermined breaking region 31 has a considerably smaller thickness d1 than the thickness d2 of FIG Cover plate 23 forming sheet. The thickness d1 of the predetermined breaking region 31 can be selected, for example, as a function of the material properties and the geometrical design of the predetermined breaking region such that the predetermined breaking region locally bursts when an increased internal pressure in the housing 11 occurs, for example, more than 5000 hPa, so that gas from the Housing 1 1 can escape. For example, the thickness d2 of the sheet used for the cover plate 23 can typically be between 1 and 3 mm, whereas the thickness d1 of the predetermined breaking range can be reduced to less than 0.5 mm to achieve the desired bursting properties.

In order to manufacture the cover plate 23 in one piece with the predetermined breaking region 31 formed integrally therein, for example, a stamp of suitable geometry can be embossed into the sheet metal forming the cover plate 23. The shape of this stamp is designed such that material is displaced out of the center of the area to be embossed out and displaced into adjacent areas. As a result, thickening regions 33 can arise at the edge around the predetermined breaking region 31, at which the cover plate 23 has a greater thickness than the original thickness d2 of the used

Metal sheet. Depending on the type and shape of the stamp used, the

Thickening regions 33, for example, have increased by 1 mm to 3 mm thickness.

The process of embossing the metal sheet to produce the predetermined breaking area 31 in the cover plate 23 can be carried out in a single embossing process and / or with a single embossing tool, but it can also be several separate

Embossing processes, for example, with different embossing tools or Stamping can be used to ultimately produce the desired shape and geometry for the predetermined breaking area 31.

As can be seen most clearly in the sectional view of FIG. 4, additional line-like weakened regions 35 may be formed in the predetermined breaking region 31, which have a smaller thickness than the remaining predetermined breaking region 31. For example, a thickness d3 at such a weakened region 35 can be in the region of 0, 01 to 0.5 mm, preferably in the range of 0.05 to 0.2 mm. Upon occurrence of excessive internal pressure in the housing 1 1, such a dilute

Weakening range serve as a predetermined breaking line along which the predetermined breaking region 31 tears when bursting. The weakening regions 35, like the entire predetermined breaking region 31, can be produced by locally embossing material using a suitable embossing tool. 4 shows a motor vehicle 100 with a battery 102 which is composed of a plurality of the battery cells 1 described above.

Claims

claims

1. battery cell (1), in particular lithium-ion battery cell, comprising:

a winding element (3) consisting of a wound stack (5) of a first film coated with anode material, a second film coated with cathode material and two plastic films serving as diaphragms,

an electrolyte,

two current collectors (7, 9), one of which is electrically conductively connected to the first foil and one to the second foil,

a housing (11) with a metallic container (13) and a metallic one

Lid assembly (15),

wherein the container (13) has an opening (14) through which the winding element (3) and the two current collectors (7, 9) during manufacture of the battery cell (1) in the housing (1 1) can be introduced

wherein the lid assembly (15) has a cover plate (23) and the opening (14) of the container (13) gas-tight and pressure-sealed,

wherein on the cover assembly (15) has a feedthrough assembly (25) is formed for gas-tight passage of electrically conductive contact assemblies (19) which in each case with one of the current collector (7, 9) in the interior of the housing (1 1) in contact, through Cover plate (23) through out of the housing (1 1),

characterized in that

the cover plate (23) has a predetermined breaking region (31) of reduced thickness (d1), which is designed to burst at an increased internal pressure in the housing (11).

2. Battery cell according to claim 1, wherein the cover plate (23) around the predetermined breaking area (31) around a thickening region (33) having a thickness which is greater than an average thickness (d2) of the cover plate (23) outside the predetermined breaking area (31 ).

3. Battery cell according to claim 1 or 2, wherein the cover plate (23) has an average thickness (d2) of more than 1 mm and the predetermined breaking region (31) has a thickness (d1) of less than 0.5 mm.

4. Battery cell according to one of claims 1 to 3, wherein the predetermined breaking area (31) line-like weakening areas (35) with a smaller thickness (d3) than

average thickness (d1) of the predetermined breaking area (31).

5. Battery cell according to one of claims 1 to 4, wherein the predetermined breaking area (31) is adapted to burst at an elevated internal pressure of more than 5000 hPa in the housing (1 1).

6. Battery cell according to one of claims 1 to 5, wherein the cover plate (23)

including the predetermined breaking area (31) is produced by embossing a metal sheet.

7. Battery cell according to one of claims 1 to 6, wherein the predetermined breaking region (31) in the cover plate (23) is integrally integrated.

8. A method for manufacturing a housing for a battery cell with a metallic container (13) and a metallic lid assembly (15),

the container (13) having an opening (14) through which a winding element (3), two current collectors (7, 9) and an electrolyte can be introduced into the housing (11) during manufacture of the battery cell (1),

wherein the cover assembly (15) has a cover plate (23) and the opening (14) of the container (13) after completion of the housing gas-tight and pressure-tight manner, characterized in that

in the cover plate (23) is formed by embossing a predetermined breaking area (31) of reduced thickness (d1), which is adapted to be at an increased internal pressure in the

Burst housing (11).

9. The method of claim 8, wherein in the embossing material from the predetermined breaking region (31) in an adjacent thickening region (33) of the cover plate (23) is displaced by pressing.

10. Motor vehicle (100) comprising a battery cell (1) according to one of claims 1 to 9.