Round cell battery including dissipation element and insulating thermoplastic elastomer

A round cell rechargeable battery includes a plurality of round cells arranged next to one another and a dissipation element that is electrically insulated from the round cells and connects a group of round cells in thermally-conductive fashion so as to dissipate heat. The dissipation element is in the form of a rod and is bent in such a way that it runs in zigzag fashion alternately in each case along a lower side, an adjoining side wall, and an upper side of the round cells. The battery also includes an electrically-insulating, thermally-conductive, rubber-elastic thermoplastic elastomer, which is arranged at least partially between the dissipation element and the round cells to insulate the dissipation element electrically from the round cells and to dissipate heat from the round cells to the dissipation element.

BACKGROUND

The present application relates to a round cell rechargeable battery. More specifically, the present application relates to a battery that includes an element for dissipating heat from a plurality of cells in the battery.

EP 0 917 230 B1 has disclosed a rechargeable battery with a temperature stabilizer.

DE 102 23 782 B4 has disclosed a battery with at least one electrochemical storage cell and a cooling device, through which a liquid cooling medium flows. The storage cells are accommodated in openings in the cooling devices and are partially in force-fitting contact with in each case one outer surface, which is curved in a direction perpendicular to the longitudinal axis of the storage cell. An expansion joint is provided in the regions of the force-fitting contact.

DE 10 2007 009 315 A1 has disclosed a device for cooling electrical elements with conductor bodies, which are in thermal contact with side faces of the electrical elements so as to dissipate heat.

In an electrical rechargeable battery with round cells, there is the problem of heat dissipation. This problem is intensified by the fact that the can of the cells are at an electrical potential.

It would be advantageous to provide an improved round cell rechargeable battery that better addresses this issue.

SUMMARY

An exemplary embodiment relates to a round cell rechargeable battery that includes a plurality of round cells arranged next to one another and a dissipation element that is electrically insulated from the round cells and connects a group of round cells in thermally-conductive fashion so as to dissipate heat. The dissipation element is in the form of a rod and is bent in such a way that it runs in zigzag fashion alternately in each case along a lower side, an adjoining side wall, and an upper side of the round cells. The battery also includes an electrically-insulating, thermally-conductive, rubber-elastic thermoplastic elastomer, which is arranged at least partially between the dissipation element and the round cells to insulate the dissipation element electrically from the round cells and to dissipate heat from the round cells to the dissipation element.

Another exemplary embodiment relates to a rechargeable battery comprising a plurality of round cells and a dissipation element that is electrically insulated from the round cells and connects a group of round cells in thermally-conductive fashion so as to dissipate heat. The dissipation element is in the form of a rod and runs in zigzag fashion along a lower side, an adjoining side wall, and an upper side of the round cells. The battery also includes a thermoplastic elastomer provided at least partially between the dissipation element and the round cells.

DETAILED DESCRIPTION

According to an exemplary embodiment, a round cell rechargeable battery includes a plurality of round cells arranged next to one another and a dissipation element that is electrically insulated from the round cells and connects a group of round cells in thermally-conductive fashion so as to dissipate heat. The dissipation element is in the form of a rod and is bent in such a way that it runs in zigzag fashion alternately in each case along a lower side, an adjoining side wall, and an upper side of the round cells. The battery also includes an electrically-insulating, thermally-conductive, rubber-elastic thermoplastic elastomer, which is arranged at least partially between the dissipation element and the round cells to insulate the dissipation element electrically from the round cells and to dissipate heat from the round cells to the dissipation element.

The dissipation receptacle elements arranged and designed in accordance with an exemplary embodiment described herein fulfill a plurality of functions.

Firstly, the thermoplastic elastomer provides the electrical insulation between the round cells and the dissipation elements, which are produced from copper, aluminum or steel, for example, and guide a suitable coolant. Suitable dissipation elements are in particular extruded parts. Suitable coolants are tetrafluoroethane (R134a) and carbon dioxide (R744), for example.

Secondly, the thermoplastic elastomer conducts the heat from the round cells to the dissipation elements, which transfer the heat to the coolant. Good thermal conduction is achieved if the thermoplastic elastomer has a thermal conductivity greater than one Watt per Kelvin-meter (i.e., >1 W/(mK)). Preferably, the thermal conductivity is greater than from two to three Watts per Kelvin-meter (i.e. >3 W/(mK)). Suitable thermoplastic elastomers are offered for sale by the company Cool Polymers, Inc., USA, under the designations CoolPoly® D8102 Thermally-conductive Thermoplastics Elastomer (TPE) and CoolPoly® D8104 Thermally-conductive Thermoplastics Elastomer (TPE).

Thirdly, the thermoplastic elastomer, owing to its rubber-elastic property, ensures good contact between the round cells and the dissipation elements. Air gaps which impair the thermal conduction from the round cells to the coolant are effectively avoided. In particular, the round cells being pressed against the dissipation elements during manufacture of the round cell rechargeable battery ensures that the heat transfer surfaces lie on one another in optimum fashion and air gaps are avoided. Thermoplastic elastomers with a Shore A hardness of from 20 to 100 have demonstrated good results in unofficial experiments.

In one embodiment, jackets in the form of flexible tubes and consisting of an electrically-insulating, thermally-conductive and rubber-elastic thermoplastic elastomer are provided, which have been drawn over the round cells. Dissipation receptacle elements can be arranged on the outer sides of the jackets. Preferably, six dissipation receptacle elements are provided on each jacket of an inner round cell and are arranged uniformly on the outer side, i.e. in 60° intervals. An inner round cell is surrounded completely by other round cells parallel to the longitudinal axis of said inner round cell, i.e. it is not at the edge of the round cell rechargeable battery. The jackets can be formed from the same material as the dissipation receptacle elements. In this case, the jackets and the dissipation receptacle elements are expediently designed to be integral.

In a further embodiment, the round cells are accommodated in at least one dissipation receptacle element, which is common to a group of round cells, said dissipation receptacle elements having a receiving contour which matches the side wall surfaces of the round cells, with the result that these side wall surfaces bear against the inner wall of an associated dissipation receptacle element, the dissipation receptacle elements furthermore having a receiving bore for receiving the rod-shaped dissipation elements. Preferably, the dissipation receptacle elements have cross sections which are triangular in the longitudinal direction and have concave sides. The dissipation receptacle elements in this case at the same time act as spacers between the round cells. Effective heat transfer between the round cells and the dissipation receptacle elements is achieved if those inner walls of the dissipation receptacle elements which adjoin the round cells are curved. Advantageously, the dissipation receptacle elements have notches, which protrude radially out of the receiving bore into the dissipation receptacle element. The notches improve the contact between the round cells and the dissipation receptacle elements, on the one hand, and the dissipation receptacle elements and the dissipation elements, on the other hand, when the round cell rechargeable battery is produced. In addition, the notches make it easier for the individual components to be joined together and therefore for the round cell rechargeable battery to be produced.

FIG. 1shows a jacket1in the form of a flexible tube and consisting of a thermoplastic elastomer, which is electrically-insulating, has good thermal conductivity and is (rubber-)elastic. The upper detail inFIG. 1illustrates a side view and the lower detail illustrates a plan view.

The jacket1has substantially the lateral surface shape of a circular cylinder. A longitudinal axis2coincides with the cylinder axis.

Six dissipation receptacle elements3are arranged on the outer surface of the jacket1. The dissipation receptacle elements3are arranged at uniform distances from one another, i.e. at angular distances of 60 degrees.

The dissipation receptacle elements3are in the form of rods and extend from an upper side4to a lower side5.

The dissipation receptacle elements3have curved cutouts6with a cross section in the form of a circular arc. These cutouts6act as guides for dissipation elements (not illustrated inFIG. 1) with cross sections in the form of circular cylinders.

FIG. 2shows the jacket1shown inFIG. 1which has been drawn over a round cell7. The round cell7has a known design, and in particular has a positive electrode8and a negative electrode9. The Figure also shows a degassing valve10. Owing to the rubber-elasticity of the jacket1, the jacket1sits firmly on the round cell7.

FIG. 3shows a perspective view of the situation shown inFIG. 2.

FIGS. 4 and 5show a plurality of round cells7arranged to form a stack or module11.FIG. 4shows a partial view in the direction IV.

The stack11has three rows12each having five round cells7. The rows12are arranged offset with respect to one another alternately through half a diameter of the round cells7perpendicular to the longitudinal direction2of the round cells7. This arrangement enables dense packing of the round cells. The stack11is not complete. It comprises only some of all of the round cells7of a round cell rechargeable battery.

The round cells7each have a jacket1. In each case six dissipation receptacle elements3are arranged uniformly on the outer side of the jackets1. This is expedient since, with this packing density of the round cells7, each round cell7has six directly adjacent round cells7. This applies in any case to round cells7which are not at the edge of the round cell rechargeable battery (inner round cell). For example, round cell13is an inner round cell7.

FIG. 4shows dissipation elements14. The dissipation elements14are each guided by three dissipation receptacle elements3, each of these three dissipation receptacle elements3being associated with a different round cell7. The dissipation elements14have a circular cross section. It can be seen that two adjacent round cells7are not in direct contact with one another, but are always separated from one another, in particular electrically insulated from one another, by two jackets1.

FIG. 6shows another embodiment of a dissipation receptacle element15.

The dissipation receptacle element15is in the form of a rod. It has a length which approximately corresponds to the length of the round cells7. The dissipation receptacle element15has a triangular cross section perpendicular to the longitudinal axis2(i.e., when viewed in the direction of the longitudinal axis); this can be seen in the lower detail inFIG. 6. The dissipation receptacle element15has a receiving contour16, which is matched to the side wall surfaces of the round cells7and comprises three circular arcs.

A receiving bore17as a guide for a dissipation element14with a circular cross section is provided in the center. Three notches18protrude radially out of the receiving bore17into the dissipation receptacle element15. In addition, a slot19is provided in the receiving contour16. Firstly, the dissipation element14can be introduced into the guide via the slot19. Secondly, disruptive air slots during compression of the round cell rechargeable battery are avoided. The slot19therefore also acts as an expansion joint during the compression.

FIG. 7shows the round cell7, with six dissipation receptacle elements15arranged uniformly over the circumference thereof adjacent to the side wall surface. The dissipation receptacle elements15are not in contact with one another; this can be seen from the gaps20.

FIG. 9shows a partial section through a stack21of round cells7with the dissipation receptacle elements15. It can be seen that the round cells7are not in contact with one another owing to the arrangement of the dissipation receptacle elements15. Since the dissipation receptacle elements15are produced from electrically-insulating thermoplastic elastomer, the round cells7are insulated electrically from one another. The dissipation receptacle elements15are not connected to one another.

FIG. 10shows an interlayer22, which is formed from dissipation receptacle elements15. The interlayer22consists of dissipation receptacle elements15arranged next to one another in a row. In each case two adjacent dissipation receptacle elements15are connected to one another. During the manufacture of the round cell rechargeable battery, the interlayer22is positioned between two adjacent rows12of round cells7. The interlayer22provides the advantage of simple manufacture of the round cell rechargeable battery.

FIG. 11shows a plan view of the dissipation element14, i.e. in the direction of the longitudinal axis2.

FIG. 12shows a side view of the dissipation element14shown inFIG. 11, i.e., perpendicular to the longitudinal axis2.

FIG. 13shows a perspective view of the dissipation element14shown inFIGS. 11 and 12.

It is apparent fromFIGS. 11,12and13that the dissipation element14runs in zigzag fashion in three dimensions, i.e. an imaginary axis of the tubular dissipation element14describes a three-dimensional serpentine curve.

FIGS. 14 to 19describe part of the fitting process for the round cell rechargeable battery.

First, the dissipation element14is inserted into a plastic part23(FIG. 14).

Then, the round cells7, which have been provided with the jacket1and the dissipation receptacle elements3, are positioned onto the dissipation element14in such a way that the dissipation element14is guided in the cutouts6in the dissipation receptacle elements3(FIG. 15).

The procedures fromFIGS. 14 and 15are repeated until a sufficient number of rows of round cells7has been formed.

It can be seen fromFIG. 19that the individual dissipation elements14are brought together at one end24of the stack11. They can be connected with a collector (not illustrated).

The round cell rechargeable battery is compressed via two mutually opposite terminating plates25, of which only one is shown. An optimum assembly of components for heat transfer is thus ensured.