POUCH CELL

Abstract

A pouch cell having at least one connection electrode via which the pouch cell can be electrically contacted, wherein the pouch cell includes a current interrupter configured, by virtue of a thermally induced change in its geometric dimensioning, at least temporarily to interrupt drawing of current via the connection electrode. Preferably, the current interrupter includes a material having a negative coefficient of thermal expansion, wherein the thermally induced change in its geometric dimensioning is brought about by a change in a pouch cell temperature.

Claims

1-12. (canceled)

13. A pouch cell comprising: at least one connection electrode, the pouch cell being electrically contactable via the at least one connection electrode; a current interrupter configured, by virtue of a thermally induced change in a geometric dimensioning of the current interrupter, at least temporarily to interrupt drawing of current via the connection electrode.

14. The pouch cell as recited in claim 13 wherein the current interrupter includes a material having a negative coefficient of thermal expansion and the thermally induced change in the geometric dimensioning is brought about by a change in a pouch cell temperature.

15. The pouch cell as recited in claim 13 wherein the current interrupter is arranged at the connection electrode or is part of the connection electrode.

16. The pouch cell as recited in claim 13 wherein the current interrupter is configured in such a way that a current interruption is brought about by thermal shrinkage of a material of the current interrupter.

17. The pouch cell as recited in claim 16 wherein the current interruption occurs if a pouch cell temperature exceeds a predefined temperature threshold.

18. The pouch cell as recited in claim 13 wherein the connection electrode includes an inner portion and an outer portion, wherein the inner portion surrounded by an outer enclosure of the pouch cell and the outer portion, at least in sections, is situated outside the outer enclosure.

19. The pouch cell as recited in claim 18 wherein the inner portion is completely surrounded by the outer enclosure.

20. The pouch cell as recited in claim 18 wherein the inner portion and the outer portion are positionally fixed in relation to the outer enclosure or positionally fixed with respect to one another.

21. The pouch cell as recited in claim 13 wherein the current interrupter is part of an electrical circuit into which the pouch cell itself is electrically integrated.

22. The pouch cell as recited in claim 13 wherein the current interrupter is in series connection in the electrical circuit.

23. The pouch cell as recited in claim 14 wherein the material includes zirconium tungstate.

24. The pouch cell as recited in claim 14 wherein the material has an electrical conductivity of greater than 1×10{circumflex over ( )}5 siemens per meter.

25. The pouch cell as recited in claim 13 wherein the current interrupter is configured to reversibly interrupt drawing of current via the connection electrode.

26. A rechargeable battery pack comprising the pouch cell as recited in claim 13

27. An electrical hand-held power tool comprising the rechargeable battery pack as recited in claim 26.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the figures, components which are the same and components of the same type are denoted by the same reference signs. In the figures:

[0019] FIG. 1a shows a first preferred exemplary embodiment of a pouch cell according to the invention having a current interrupter;

[0020] FIG. 1b shows a schematic illustration of a hand-held power tool having a rechargeable battery pack and a pouch cell;

[0021] FIGS. 2A and 2B shows the pouch cell from FIG. 1a with the temperature threshold having been undershot (FIG. 2A) and with the temperature threshold having been exceeded (FIG. 2B);

[0022] FIG. 3 shows a second preferred exemplary embodiment of a pouch cell according to the invention with the temperature threshold having been undershot; and

[0023] FIG. 4 shows the exemplary embodiment from FIG. 3 with the temperature threshold having been exceeded.

DETAILED DESCRIPTION

[0024] A first preferred exemplary embodiment of a pouch cell 10 according to the invention is illustrated in FIG. 1a. The pouch cell 10 has a connection electrode 1 via which the pouch cell 10 can be electrically contacted. To put it more precisely, the connection electrode 1 is electrically connected to an active layer 8 of the pouch cell 10. The active layer 8 is completely surrounded by an outer enclosure 9 of the pouch cell 10.

[0025] The connection electrode 1 comprises an inner portion 2 and an outer portion 3, wherein the inner portion 2 is completely surrounded by the outer enclosure 9 of the pouch cell 10 and the outer portion 3 is situated predominantly outside said outer enclosure 9.

[0026] The pouch cell 10 comprises a current interrupter 5 configured, by virtue of a thermally induced change in its geometric dimensioning, at least temporarily to interrupt drawing of current via the connection electrode 1. In the exemplary embodiment illustrated in the present case, the current interrupter 5 is part of the connection electrode 1, wherein the current interrupter 5 is situated between the inner portion 2 and the outer portion 3 in the sense of a mechanical and electrical series connection.

[0027] The inner portion 2 and the outer portion 3 are incorporated into the outer enclosure 9, for example by being welded therein, in each case in a manner positionally fixed in relation to the outer enclosure 9. Furthermore, the inner portion 2 and the outer portion 3 are arranged in a manner positionally fixed with respect to one another. This applies in particular to the sections of the inner portion 2 and of the outer portion 3 which are closest to one another. The term “positionally fixed” takes into account a certain inherent flexibility of the pouch cell 10.

[0028] In the exemplary embodiment illustrated in the present case, the current interrupter 5 comprises a material having a negative coefficient of thermal expansion, for example zirconium tungstate. Nickel components are incorporated in the material, such that besides a negative coefficient of thermal expansion, the material also has an electrical conductivity of greater than 1×10.sup.5 siemens per meter.

[0029] In FIG. 1a, a pouch cell temperature PT falls below a predefined temperature threshold TS, wherein the predefined temperature threshold is 60 degrees Celsius, for example. In this state, the inner portion 2 and the outer portion 3 are electrically contacted via the current interrupter 5, such that the pouch cell 10 can be charged or discharged.

[0030] FIG. 1b schematically illustrates an electrical hand-held power tool 1000, which is supplied via a rechargeable battery pack 100, wherein the rechargeable battery pack is equipped with at least one pouch cell 10.

[0031] FIG. 2A shows an excerpt from the pouch cell from FIG. 1a, wherein, as in FIG. 1a, the pouch cell temperature PT falls below the predefined temperature threshold TS. Consequently, the inner portion 2 and the outer portion 3 are electrically contacted via the current interrupter 5.

[0032] A current interruption will now be explained in more specific detail with reference to FIG. 2B. As already mentioned, the current interrupter 5 comprises a material having a negative coefficient of thermal expansion. A change in the geometric dimensioning of the current interrupter 5 is brought about by a change in the pouch cell temperature PT. By virtue of the fact that the inner portion 2 consists of metal, the inner portion 2 and the current interrupter 5 are thermally coupled, such that the current interrupter 5 experiences an increase in temperature of the active layer 8 via the inner portion 2.

[0033] In the exemplary embodiment illustrated, the current interruption is brought about by thermal shrinkage of the material if the pouch cell temperature PT exceeds a predefined temperature threshold TS. As is evident from FIG. 2B), the change in the geometric dimensioning of the material is a shortening of the material of the current interrupter 5 in the longitudinal direction L. Since the inner portion 2 and the outer portion 3 are positionally fixed in relation to the outer enclosure 9 and positionally fixed with respect to one another, shrinkage of the current interrupter 5 in the longitudinal direction L—indicated here by a gap SP that is formed—brings about electrical isolation of the outer portion 3 from the inner portion 2. Consequently, the pouch cell 10′ in an elevated temperature state can neither continue to be charged nor be discharged.

[0034] In the present case, the current interrupter 5 is configured to reversibly interrupt drawing of current via the connection electrode 1. If the pouch cell temperature PT falls below the predefined temperature threshold TS, a current flow is possible once again, cf. FIG. 2A.

[0035] FIG. 3 shows a second preferred exemplary embodiment of a pouch cell 10 according to the invention in a perspective illustration. The pouch cell 10 comprises two connection electrodes 1 in the form of a positive electrode and a negative electrode, via which the pouch cell 10 can be electrically contacted in each case.

[0036] The connection electrodes 1 comprise in each case an inner portion 2 and in each case an outer portion 3, wherein the inner portions 2 are completely surrounded by the outer enclosure 9 of the pouch cell 10 (dashed illustration). The respective outer portions 3 lie predominantly outside said outer enclosure 9.

[0037] Each of the connection electrodes 1 has a current interrupter 5 comprising a material having a negative coefficient of thermal expansion, such that, if the pouch cell temperature PT exceeds a predefined temperature threshold TS (cf. FIG. 4), a current interruption is brought about by thermal shrinkage of the material.

[0038] As can be gathered from FIG. 3, the current interrupters 5 are part of an electrical circuit 20 into which the pouch cell 10 itself is integrated electrically in series connection. The electrical circuit serves for the electrical supply of an electric motor 30 of a hand-held power tool 1000 (see FIG. 1b).

[0039] A current interruption will now be explained in more specific detail with reference to FIG. 4. As already mentioned, the current interrupters 5 comprise a material having a negative coefficient of thermal expansion. A change in the geometric dimensioning of the current interrupter 5 is brought about by a change in the pouch cell temperature PT.

[0040] As is evident from FIG. 4, the change in the geometric dimensioning of the material is a shortening of the material of the current interrupters 5 in the longitudinal direction L. Since the inner portion 2 and the outer portion 3 are in each case positionally fixed in relation to the outer enclosure 9 and in each case positionally fixed with respect to one another, shrinkage of the current interrupters 5 in the longitudinal direction L—indicated here by a gap SP that is formed in each case—brings about electrical isolation of the respective outer portion 3 from the respective inner portion 2. Consequently, the pouch cell 10′ in an elevated temperature state can neither continue to be charged nor be discharged.

LIST OF REFERENCE SIGNS

[0041] 1 Connection electrode [0042] 2 Inner portion [0043] 3 Outer portion [0044] 5 Current interrupter [0045] 8 Active layer [0046] 9 Outer enclosure [0047] 10 Pouch cell (normal temperature) [0048] 10′ Pouch cell (temperature threshold exceeded) [0049] 20 Electrical circuit [0050] 30 Electric motor [0051] 100 Rechargeable battery pack [0052] 1000 Hand-held power tool [0053] L Longitudinal direction [0054] PT Pouch cell temperature [0055] SP Gap [0056] TS Temperature threshold