BATTERY FOR AN AT LEAST PARTIALLY ELECTRICALLY OPERATED/DRIVEN FUNCTIONAL DEVICE AND FUNCTIONAL DEVICE

Abstract

A battery for an at least partially electrically operated functional device, including at least one battery cell module, in each of which a predetermined number of battery cells is clamped by a mechanical clamping device to form a cell stack. The clamping device transmits a traction force or a contact pressure corresponding to the traction force to the cell stack by delimiting elements and traction elements. A frame element is arranged in each case between at least two or some or each of the battery cells and/or the respective terminal battery cell and the delimiting element is arranged adjacent to the respective terminal battery cell and associated with it. The frame element includes a circumferential part and a free volume delimited by the circumferential part.

Claims

1. A battery for an at least partially electrically operated functional device, comprising: at least one battery cell module, in each of which a predetermined number of battery cells are clamped to form a cell stack by a mechanical clamping device, wherein the clamping device has a first and at least one further delimiting element, wherein the first and the at least one further delimiting element are arranged on a respective battery cell of the two ends of the cell stack arranged opposite to one another and the clamping device is designed to transmit a traction force to the delimiting elements by traction elements and to pull them toward one another, whereby a contact pressure corresponding to the traction force is transmitted to the cell stack, wherein a frame element is arranged in each case between at least two or some or each of the battery cells and/or a respective terminal battery cell and the delimiting element arranged adjacent to the respective terminal battery cell and associated with it, wherein each two adjacent ones of the battery cells are spaced apart from one another by the respective frame element and/or the respective terminal battery cell is spaced apart from the delimiting element associated with it, wherein the respective frame element includes a circumferential part and a free volume delimited by the circumferential part and is designed to transmit the contact pressure to the respective battery cell spaced apart by the frame element by the circumferential part and to keep the free volume delimited by the circumferential part free of the contact pressure.

2. The battery as claimed in claim 1, wherein a pressure-maintaining element is arranged in the free volume, and is designed to counteract in the free volume a swelling pressure caused by an operational swelling of the adjacent battery cells spaced apart from one another by the respective frame element with a counter pressure different from the contact pressure.

3. The battery as claimed in claim 2, wherein the counter pressure is greater than an atmospheric pressure prevailing in an environment of the battery and is less than the contact pressure.

4. The battery as claimed in claim 2, wherein an aerogel and/or a mechanical spring element is arranged in the free volume as the pressure-maintaining element.

5. The battery as claimed in claim 2, wherein the pressure-maintaining element is embodied as a compression film arranged on at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

6. The battery as claimed in claim 1, wherein the battery cells each have a housing having housing edges and the circumferential part extends along the housing edges.

7. The battery as claimed in claim 1, wherein the respective frame element is formed at least in sections as a part of an outer shell of at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

8. The battery as claimed in claim 1, wherein a respective traction element is designed as a side plate extending in the direction of the traction force along the cell stack and the respective frame element is connected in a friction-locked and/or formfitting and/or materially-bonded manner to the side plate in a predetermined connection region.

9. The battery as claimed in claim 8, wherein a plurality of frame elements is connected to the side plate, wherein the individual frame elements are each arranged spaced apart from one another at a predetermined distance, wherein the distance corresponds to a width of the respective battery cell of the cell stack.

10. The battery as claimed in claim 1, wherein the battery cells are designed as prismatic battery cells or pouch cells.

11. The battery as claimed in claim 3, wherein an aerogel and/or a mechanical spring element is arranged in the free volume as the pressure-maintaining element.

12. The battery as claimed in claim 3, wherein the pressure-maintaining element is embodied as a compression film arranged on at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

13. The battery as claimed in claim 4, wherein the pressure-maintaining element is embodied as a compression film arranged on at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

14. The battery as claimed in claim 2, wherein the battery cells each have a housing having housing edges and the circumferential part extends along the housing edges.

15. The battery as claimed in claim 3, wherein the battery cells each have a housing having housing edges and the circumferential part extends along the housing edges.

16. The battery as claimed in claim 4, wherein the battery cells each have a housing having housing edges and the circumferential part extends along the housing edges.

17. The battery as claimed in claim 5, wherein the battery cells each have a housing having housing edges and the circumferential part extends along the housing edges.

18. The battery as claimed in claim 2, wherein the respective frame element is formed at least in sections as a part of an outer shell of at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

19. The battery as claimed in claim 3, wherein the respective frame element is formed at least in sections as a part of an outer shell of at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

20. The battery as claimed in claim 4, wherein the respective frame element is formed at least in sections as a part of an outer shell of at least one of the adjacent battery cells spaced apart from one another by the respective frame element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Exemplary embodiments of the invention are described hereinafter. In the figures:

[0037] FIG. 1 shows a schematic top view of a battery according to the invention arranged in a functional device according to one preferred embodiment;

[0038] FIG. 2 shows a side schematic exploded view of a battery cell, a frame element, and a pressure-maintaining means;

[0039] FIG. 3 shows a schematic illustration of a battery having undeformed battery cells and a schematic illustration of a battery having battery cells deformed by swelling in comparison.

[0040] The exemplary embodiments explained hereinafter are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention to be considered independently of one another, which each also refine the invention independently of one another. Therefore, the disclosure is also intended to include combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

[0041] In the figures, the same reference numerals each designate elements that have the same function.

DETAILED DESCRIPTION

[0042] FIG. 1 shows a schematic illustration of a functional device 10 having a battery 12 according to the invention. The functional device 10 can be designed as an at least partially electrically driven motor vehicle. For the sake of simplicity, the complete battery 12 is not shown in detail in FIG. 1, but rather only a cell stack 16, which comprises four battery cells 14 here by way of example. The cell stack 16 is delimited on each of two opposing sides in the embodiment shown in FIG. 1 by a delimiting element 18. The cell stack 16 is enclosed on each of two further sides, which are also opposite to one another, by a traction element 20. The delimiting elements 18 and the traction elements 20 are embodied as parts of a clamping device 22 which mechanically clamps the battery cells 14.

[0043] Frame elements 24 are also arranged between the battery cells 14 and between a respective terminally arranged battery cell 14 and a delimiting element 18 arranged adjacent to the terminally arranged battery cell 14. In other words, for the cell stack 16 shown in FIG. 1, an alternation results of frame elements 24 and battery cells 14. A frame element 24 is also arranged between the delimiting element 18 arranged on the outside left in FIG. 1 and the terminally arranged battery cell 14 on the outside left in FIG. 1. In a similar way, a frame element 24 is also arranged between the delimiting element 18 arranged on the outside right in FIG. 1 and the terminally arranged battery cell 14 on the outside right. In one preferred embodiment, for example, a frame element 24 can only be arranged between every second battery cell 14 and the adjacent battery cells 14. In other words, a change from a double pack of two battery cells 14 and one frame element 24 would then result in each case. The respective frame element 24 would have to be correspondingly thicker in this embodiment.

[0044] Each of the frame elements 24 comprises a circumferential part 26 and a free volume 28 delimited by the respective circumferential part 26. A pressure-maintaining means 30 in the form of a compression film or compression compensation film is arranged by way of example in each of the free volumes 28 in FIG. 1. For the sake of clarity, only one pressure medium 30 is identified in FIG. 1. As described above, the compression film is compressed in FIG. 1 in one of the free volumes 28 as a result of an operational swelling of the adjacent battery cells 14 and assumes a biconcave shape.

[0045] FIG. 2 shows, with reference to the components shown and described in conjunction with FIG. 1, a schematic side exploded view of an exemplary arrangement consisting of a battery cell 14, a circumferential part 26, a free volume 28 encompassed by the circumferential part 26, and a pressure-maintaining means 30. The circumferential part 26 and the free volume 28 are components of a frame element 24 here. In contrast to the embodiment of the pressure-maintaining means 30 in the form of a compression film shown in FIG. 1, FIG. 2 shows a substance filling the free volume 28, for example, a fluid or a gel, as the pressure-maintaining means 30. The pressure-maintaining means 30 can also be designed as an aerogel. An aerogel is a highly porous solid based on silicate, in which up to 99.98 percent of the volume consists of pores. The pressure-maintaining means 30 can, however, also be implemented by a foam or a polyurethane foam or a rubber. The pressure-maintaining means 30 can also be implemented as a mechanical spring element.

[0046] FIG. 2 additionally clearly shows the extension or the course of the circumferential part 26 along the housing edges 32 of the housing 34 of the battery cell 14. The flat, preferably large side surface 36 of the housing 34 is largely not concealed or covered by the circumferential part 26. The advantage thus results that the battery cell 14 can expand in the region of the free volume 28 delimited by the circumferential part 26. When expanding or swelling, the housing 34 is only opposed by the counter pressure exerted by the pressure-maintaining means 30. As described above, this counter pressure can preferably be greater than a prevailing atmospheric pressure and less than the contact pressure, i.e., less than the pressure applied by the traction forces of the traction elements 20.

[0047] FIG. 3 shows a cell stack 16 on the left side with reference to the components shown and described in conjunction with FIG. 1 and FIG. 2, wherein the battery cells 14 arranged in the cell stack 16 do not have deformation. On the right side, in contrast, FIG. 3 shows a cell stack 16, wherein the battery cells 14 arranged in the cell stack 16 display an operational swelling. The deformation of the battery cells 14 as a result of the swelling in the free volume 28 arranged in each case between the battery cells 14 is absorbed by the frame elements 24 according to the invention. In this way, a longitudinal expansion of the entire cell stack 16 is advantageously avoided.

[0048] As is known, for example, lithium-ion cells or battery cells having a different cell chemistry are installed in various packing forms in high-voltage batteries or batteries 12, which are generally used as electric energy accumulators for at least partially electrically driven functional devices 10, for example, for at least partially electrically driven motor vehicles. These battery cells 14 can be designed, for example, as round cells, as prismatic cells, or as pouch cells.

[0049] A defined or predetermined pressure on the battery cells 14 is necessary in order to enable controlled swelling of the battery cells 14. Unchecked swelling and also completely suppressed swelling result in a reduced service life of the battery cells 14.

[0050] Known and previously installed cell stacks 16 having prismatic battery cells 14 generally consist of a serial juxtaposition of battery cells 14, which are electrically and thermally insulated from one another, are adhesively bonded to one another, and are clamped between two end plates or delimiting elements 18. This cell stack 16 or this serial sandwich is held together by two external sheets or side plates or traction elements 20. The side plates or traction elements 20 are installed with a slight pre-tension and connected to the end plates. During the first charging procedure of a cell stack 16 thus assembled, the operational swelling of the battery cells 14 begins and the battery cells 14 inflate. The resulting pressure forces are absorbed by the side plates as traction forces. On the one hand, this results in a compression of all elastic materials within the cell stack 16, on the other hand in an elongation and thus extension of the side plates or traction elements 20. As a result, an elongation of the cell stack 16 results due to the swelling.

[0051] A disadvantage of this known arrangement is that, for example, due to a screw connection of the cell stack 16 to a bottom of the battery 12, swelling of the cell stack 16 is prevented on the bottom of the battery 12. The cell stack 16 having an originally rectangular cross section deforms into an isosceles trapezoid. Swelling and the resulting inclination have an adverse effect on the entire construction. For example, an inhomogeneous pressure load leads to faster aging within the battery cell 14. In addition, the deformations within the cell stack 16 add up, outer battery cells 14 are deformed more strongly than inner ones. The contact poles or cell poles or electrical terminals, which are electrically interconnected via busbars, move in relation to one another and result in plastic deformations of the busbars. The deformation forces of the busbars are introduced into the contact poles and result in deformations and possibly leaks in the interface between contact pole and battery cell 14. The relative movements mentioned of the cell stack 16 or of the entire battery cell modules within the battery must be compensated for by cell module connectors. In addition, the mechanical stability in the event of any mechanical force action, for example, vibration/shock or in case of crash (for example, as a result of an accident of a functional device 10 designed as an at least partially electrically driven motor vehicle) is dependent on the present swelling forces in the battery cell module or in the cell stack 16.

[0052] Further concepts for the arrangement are known, which provide, for example, a compensation element or a compressible intermediate layer within the cell stack 16, which can be arranged between the outer battery cells 14 and the end plates or delimiting elements 18. In these concepts, the external dimensions are constant and there is no inclination of possibly provided fastening screws. However, the problem of the deformation forces on the bus bars, the introduction of force into the cell poles, and the inhomogeneous pressure loading on the battery cells 14 remain unchanged.

[0053] In one preferred embodiment of the invention, the basic structure of a cell stack 16 is similar to that in known concepts, but the elastic insulating foils (for example aerogel and/or spring element and/or pressure-maintaining means 30 formed from other materials) are inserted between the battery cells 14 within a rigid frame or frame element 24. This rigid frame element 24 is preferably supported on the side walls of the battery cell 14. Due to the rigid frame or frame elements 24, each battery cell 14 is fixed in its position within the cell stack 16. The swelling of each individual battery cell 14 is preferably absorbed via the pressure-maintaining means 30 between the battery cells 14, namely in the described free volume 28. The pressure-maintaining means 30 fills the cavity or the free volume 28 within the circumferential part 26 of the frame element 24. The pressure forces resulting due to the swelling equalize between the battery cells 14, the respective first and last battery cell 14 of a cell stack 16 dissipate the pressure to the end plates or delimiting elements 18 here. The side plates or traction elements 20 designed as side plates connect the end plates and are thus subjected to traction forces.

[0054] The side plates are preferably connected to the end plates in a pre-tensioned state. If, for example, swelling forces of 25 kN are expected, the side plates can be installed on the end plates with a pre-tension of 25 kN. In this way, the serial composite of end plates or delimiting elements 18, adhesive films or pressure-maintaining means 30 designed as compression films, frame or frame element 24, and battery cells 14 is subjected to a pre-tension of 25 kN. Swelling forces up to 25 kN within the cell stack 16 are absorbed by the pre-tension of the side plates, without the outer dimensions of the cell stack 16 changing or the position of the cell poles shifting in relation to one another.

[0055] In one preferred embodiment of the invention, the frame elements 24 can be components of the battery cells 14. The frame elements 24 can also be components of the side plates or can be connected to them. The pre-tensioning by the side plates can preferably only partially compensate for the swelling forces, for example, up to 50%. The expansion of the cell stack 16 is reduced by only 50% in this way. The frame elements 24 can be manufactured from a rigid or a non-rigid or elastic material. The compression films can preferably be subjected to a pre-tension of 2 kN, which can increase to up to 25 kN in the course of the service life of the cell stack 16 or the individual battery cells 14. The spacer frames or frame elements 24 are preferably pressurized with an active pressure of greater than 25 kN over the entire service life of the battery 12.

[0056] The invention results in multiple advantages. Thus, the swelling of the battery cells 14 takes place largely homogeneously, since each battery cell 14 has the same environmental conditions (results in extended service life, less risk of failure). The outer dimensions of a respective cell stack 16 (or a respective battery cell 14) do not change, or change only minimally, in the region of the screwing points of the cell stack 16 on a bottom of the battery 12, depending on how much pre-tension is applied to the side plates. In addition, the cell poles of the battery cells 14 are not subjected to forces due to relative movements over the service life of the battery 12. The module connectors between the battery cell modules within the battery 12 do not have to compensate for movements due to swelling. The screws for fixing the battery cell modules or cell stack 16 in the battery 12 do not become inclined. The cell stack 16 is also less sensitive to vibration, since all the individual parts of the cell stack 16 are held together with a constantly high force over the entire service life of the battery 12. With a suitable construction of the intermediate layers or frame elements 24 between the battery cells 14, it is possible to limit the maximum pressure force to a defined value in order to prevent a reduction in performance due to excessively high pressures (closure of the pores in the separator film).

[0057] Overall, the examples show how the invention can prevent a relative movement between the cell poles of respective battery cells 14 clamped together to form a cell stack 16. In addition, the examples show how it is possible for the invention to prevent external dimensions of a cell stack 16 from changing or only changing insignificantly as a result of swelling over the service life of the battery cells 14. An equal mechanical load of all battery cells 14 of the cell stack 16 can thus advantageously be achieved.