CELL COIL FOR A LITHIUM-ION ACCUMULATOR

Abstract

The invention relates to a cell coil (30, 40, 50, 60, 100, 200) for a lithium-ion battery, comprising at least two sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82), which are wound in a space-saving manner and are thermally coupled to each other. According to the invention, the at least two sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) are electrically connected in parallel in normal operation, and, in the event of a fault, in particular in the event of an internal short circuit in at least one defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82), at least one defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) can be electrically separated from the at least one intact sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82). Because of the at least one defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) that can be immediately electrically separated from the intact sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) by means of an electronic monitoring device (36) in the “event of a fault”, a high level of robustness of the cell coil (30, 40, 50, 60, 100, 200) in respect of internal short circuits is achieved. Among other things, the intact sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) act, because of the thermal coupling between the sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82), as a damage-reducing heat sink for the waste heat that is released during the fast discharge of the affected defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) generally occurring in the event of a short circuit.

Claims

1. A cell coil (30, 40, 50, 60, 100, 200) for a lithium ion accumulator having at least two sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) which are wound in a space-saving fashion and thermally coupled to one another, characterized in that the at least two sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) are connected electrically in parallel in a normal operating mode, and in the case of a fault, at least one defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) can be electrically disconnected from an at least one intact sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82).

2. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 1, characterized in that each sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) has a cathode (12) which is coated at least partially with a first active material (14) and an anode (16) which is coated at least partially with a second active material (18), and a separation layer (20) runs between the first and the second active materials (14, 18).

3. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 2, characterized in that the cathode (12) and/or the anode (16) of at least one sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) are provided with an insulating layer (26, 72) which disconnects the sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) from at least one further sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82).

4. The cell coil (40) as claimed in claim 1, characterized in that the at least two sub-cells (42, 44) are wound in an essentially serpentine shape in order to form a prismatic shape of the cell coil (40).

5. The cell coil (50) as claimed in claim 1, characterized in that the at least two sub-cells (52, 54) are wound in an essentially helical shape in order to form a cylindrical shape of the cell coil (50).

6. The cell coil (60) as claimed in claim 4, characterized in that in each case an electrically and/or mechanically and/or thermally insulating separation layer (66) is provided between at least two sub-cells (52, 54).

7. The cell coil (60) as claimed in claim 1, characterized in that the cell coil (60) has an inner winding (62) and an outer winding (64) which surrounds the inner winding, wherein the inner winding (62) and the outer winding (64) are each formed with a wound sub-cell (68, 70).

8. The cell coil (60) as claimed in claim 7, characterized in that at least one further outer winding (64) which contains a further sub-cell (68, 70) is wound onto the outer winding (64).

9. The cell coil (60) as claimed in claim 7, characterized in that in each case an electrically and/or mechanically and/or thermally insulating separation layer (66) is provided between the inner winding (62) and the outer winding (64) and/or between the at least two outer windings (64).

10. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 1, characterized in that each sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) has in the an unwound state an essentially web-shaped form with a width (B).

11. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 1, characterized in that the cathode (12) and the anode (16) of each sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) have, for the formation of electrical contact, at least one cathode lug (K.sub.11, K.sub.12, K.sub.21, K.sub.22) and one anode lug (A.sub.11, A.sub.12, A.sub.21, A.sub.22) lying opposite one another, wherein the at least one cathode lug (K.sub.11, K.sub.12, K.sub.21, K.sub.22) and the at least one anode lug (A.sub.11, A.sub.12, A.sub.21, A.sub.22) each project beyond, in each case, one of the two longitudinal edges (86, 88, 90, 92) of the sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) by a width (b), transversely with respect to a longitudinal axis (84) of the sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82).

12. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 11, characterized in that at least two cathode lugs (K.sub.11, K.sub.12, K.sub.21, K.sub.22) and at least two anode lugs (A.sub.11, A.sub.12, A.sub.21, A.sub.22) are formed axially offset with respect to one another by a distance (L.sub.1, L.sub.2) on each longitudinal edge (86, 88, 90, 92) of the sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82).

13. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 12, characterized in that the distance (L.sub.1, L.sub.2) is varied in each case such that in the wound state of each sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) the cathode lugs (K.sub.11, K.sub.12, K.sub.21, K.sub.22) and the anode lugs (A.sub.11, A.sub.12, A.sub.21, A.sub.22) lie essentially congruently one on top of the other in order to form a cathode contact (102, 104, 202, 204, 206, 208) and an anode contact.

14. The cell coil (30, 40, 50, 60, 100, 200) as claimed in claim 1, wherein the at least two sub-cells (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) are connected electrically in parallel in the normal operating mode, and in the case of an internal short-circuit in at least one defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82), at least one defective sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82) can be electrically disconnected from the at least one intact sub-cell (10, 32, 42, 44, 52, 54, 68, 70, 80, 82).

15. The cell coil (60) as claimed in claim 5, characterized in that in each case an electrically and/or mechanically and/or thermally insulating separation layer (66) is provided between at least two sub-cells (52, 54).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will be described in more detail below with reference to the drawing, in which:

[0026] FIG. 1 shows a schematic cross section through a sub-cell having an insulating layer,

[0027] FIG. 2 shows a basic illustration of an embodiment of a cell coil having two sub-cells and a monitoring device,

[0028] FIG. 3 shows an embodiment of a cell coil having a prismatic shape,

[0029] FIG. 4 shows an embodiment of a cell coil having a cylindrical shape,

[0030] FIG. 5 shows an embodiment of a cell coil having an inner winding and an outer winding surrounding the latter coaxially,

[0031] FIG. 6 shows a schematic plan view of two unrolled web-shaped sub-cells which lie one on top of the other and have cathode lugs and anode lugs for the electrical connection,

[0032] FIG. 7 shows a basic plan view of a cell coil having two sub-cells, and

[0033] FIG. 8 shows a basic plan view of an embodiment of a cell coil having four sub-cells.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a schematic cross section through a sub-cell 10 for use in a cell coil 30, 40, 50, 60, 100, 200 according to the invention for a lithium-ion accumulator (not illustrated in the drawings).

[0035] The sub-cell 10 comprises a cathode 12 which is provided with a first electrochemical active material 14, and a cathode 16 which is at least partially coated with a second electrochemical active material 18. The two active materials 14, 18 which run parallel one on top of the other in the unrolled or non-rolled state of the sub-cell 10 are disconnected from one another by a separation layer 20 made of micro-porous polyethylene and/or polypropylene. The cathode 12 and the anode 16 each form a first and a second current conductor 22, 24 for feeding current to the sub-cell 10. For example, the cathode 12 is provided here with an insulating layer 26 in order to avoid intercellular short-circuits during the winding of the sub-cell 10. The insulating layer 26 can, however, also be provided in the region of the anode 16 and in the region of the cathode 12 and the anode 16. The insulating layer 26 can be embodied here as a fixed component of the sub-cell 10 or can be positioned on the layered structure composed of the cathode 12 with the first active material 14, the separation layer 20 and the anode 16 with the second active material 18. The active materials 14, 18 can have a material composition of the same or of different substances, while the cathode 12 is formed with aluminum, and the anode 16 with copper. The unrolled, web-shaped sub-cell 10 here is preferably held in reserve as an “endless” semi-finished product in the form of a roll and can easily be processed to form cell coils 30, 40, 50, 60, 100, 200 with a wide variety of different shapes by winding or rolling.

[0036] Basically, any desired number of sub-cells 10 whose layered structure respectively corresponds to the structure of the sub-cell 10 described above can be stacked one on top of the other to form a structure which comprises a plurality of sub-cells 10.

[0037] FIG. 2 shows a basic illustration of a cell coil 30 with two sub-cells 10, 32 as well as with a monitoring device 36.

[0038] A cell coil 30 is formed with the sub-cell 10 in FIG. 1 and with a further sub-cell 32 which is of the same design, wherein an inner thermal coupling 34 is present between the sub-cells 10, 32 which lie one on top of the other. The two sub-cells 10, 32 are connected electrically in parallel in a “normal operating mode” of the cell coil 30. In “the case of a fault” such as e.g. a short circuit in one of the two sub-cells 10, 32, these can be electrically disconnected by means of a preferably electronic monitoring device 36. The electrical disconnection can be carried out e.g. with a switch 38 which is embodied as a normally closed switch and which can be actuated by means of the monitoring device 36. The switch 38 can be implemented with an electromechanical relay or with suitable power semiconductors, wherein in the latter case no galvanic or potential-free disconnection of the sub-cells 10, 32 is possible.

[0039] FIG. 3 shows an embodiment of a cell coil 40 with a prismatic shape.

[0040] In order to construct a prismatic shape, a cell coil 40 is formed with a first and a second sub-cell 42, 44 which lie one on top of the other and are wound one into the other in an approximately serpentine shape. The structural design of the sub-cells 42, 44 corresponds in each case to that of the sub-cell 10 described in FIG. 1. The prismatic cell coil 40 is preferably provided with a cuboid housing for use for a lithium-ion accumulator. In contrast with the two sub-cells 42, 44 which are merely shown here by way of example, the cell coil 40 can also have three or more sub-cells 10, 42, 44. According to the invention, the two sub-cells 42, 44 of the cell coil 40 can be electrically disconnected from one another by means of the monitoring device 36 in FIG. 2.

[0041] In the “normal operating mode” of the cell coil 40, the two sub-cells 42, 44 are connected in parallel in order to ensure, in particular, uniform charging. In the “event of a fault” of the cell coil 40, which fault is present e.g. in the event of an internal short circuit in the sub-cell 42, the defective sub-cell 42 is immediately electrically disconnected from the still intact sub-cell 44 by means of the monitoring device 36. This electrical disconnection or switching off is carried out by means of the preferably electronic monitoring device 36 (illustrated schematically in FIG. 2) by means of a relay or using suitable power semiconductors. As a result of the electrical disconnection which takes place approximately in real time, the intact sub-cell 44 additionally functions as a heat sink for ohmic dissipated heat which is released during the rapid discharging of the defective sub-cell 42 which is generally initiated in order to limit damage in the case of a short circuit, wherein at the same time the full current-carrying capacity of the cell coil 40 can be utilized for the rapid discharging process, with the result that shortening of the rapid discharging time can be achieved.

[0042] FIG. 4 illustrates a further embodiment of a cell coil 50 with a cylindrical shape.

[0043] In order to construct a cylindrical shape, a cell coil 50 is formed with two sub-cells 52, 54 which lie one on top of the other and are wound approximately in a helical shape and whose structural design corresponds in turn in each case to the sub-cell 10 already explained in FIG. 1. The cell coil 50 is predominantly suitable for lithium-ion accumulators whose housing has a non-polygonal shape which deviates from the cuboid shape. In contrast to the first and second sub-cells 52, 54 which are merely exemplary here, the cell coil 50 can also have three or more sub-cells 10, 52, 54.

[0044] FIG. 5 illustrates a further embodiment of a cell coil 60 with an inner winding 62 and an outer winding 64 which surrounds the latter coaxially.

[0045] A cell coil 60 is formed with an inner winding 62 and an outer winding 64 which surrounds the latter coaxially, wherein an electrically insulating separation layer 66 is provided between the inner winding 62 and the outer winding 64. The inner winding 62 is formed with a wound first sub-cell 68 and the outer winding 64 is formed with a rolled second sub-cell 70. The rolled sub-cells 68, 70 each lie one on top of the other or against one another in the inner winding 62 and in the outer winding 64.

[0046] The separation layer 66 functions, in particular not only as an insulating layer 72 of the outer second sub-cell 70 but also as an additional electrical insulating means between the inner winding 62 and the outer winding 64. Where necessary, at least one further outer winding 64 can be wound onto the illustrated outer winding 64 with the intermediate positioning of a further separation layer 66.

[0047] FIG. 6 illustrates a schematic plan view of two unrolled web-shaped sub-cells 80, 82 which lie one on top of the other and have cathode lugs K.sub.11, K.sub.12, K.sub.21, K.sub.22 and anode lugs A.sub.11, A.sub.12, A.sub.21, A.sub.22 for electrical connection.

[0048] The two unrolled web-shaped or strip-shaped sub-cells 80, 82 which lie one on top of the other have in each case a width B over their common longitudinal axis 84 here. The layered structure of the two sub-cells 80, 82 corresponds in turn to the structural configuration of the sub-cell 10 which is already explained in FIG. 1.

[0049] On a first longitudinal edge 86 of the first sub-cell 80, for example two e.g. trapezoidal cathode lugs K.sub.11 and K.sub.12 are formed here as integral components of the metallic cathode 12 (not illustrated here in detail for sake of better clarity of the drawing) or of the first current conductor 22 of the first sub-cell 80 in each case transversely with respect to the longitudinal axis 84. Correspondingly, on a second longitudinal edge 88 of the first sub-cell 80 in each case two anode lugs A.sub.11 and A.sub.12 are constructed lying opposite the cathode lugs K.sub.11 and K.sub.12 or in a mirror-inverted fashion with respect to the longitudinal axis 84.

[0050] The cathode lugs K.sub.11 and K.sub.12 as well as the anode lugs A.sub.11 and A.sub.12 each project beyond the longitudinal edges 86, 88 of the first sub-cell 80 by a width b, transversely with respect to the longitudinal axis 84. Between the cathode lugs K.sub.11 and K.sub.12 as well as between the anode lugs A.sub.11 and A.sub.12 there is, related in each case to their center in the axial direction, an axial distance of L.sub.1. The first sub-cell 80 has a multiplicity of cathode lugs K.sub.11 and K.sub.12 and anode lugs A.sub.11, A.sub.12 (not shown here) which are constructed in accordance with the cathode lugs K.sub.11, K.sub.12 and the anode lugs A.sub.11, A.sub.12 and the distances L.sub.1 between which vary in each case in such a way that the cathode lugs K.sub.11, K.sub.12 and the anode lugs A.sub.11, A.sub.12 lie, in the wound state of the first sub-cell 80, ideally in each case in a congruent fashion one on top of the other on the circumferential side in order to provide sufficiently mechanically stable and current-carrying-capable cathode contacts 102 and anode contacts (cf. FIGS. 7 and 8) for the formation of electrical contact or for the connection of the cell coil 100, 200.

[0051] Correspondingly, a multiplicity of correspondingly configured cathode lugs K.sub.21, K.sub.22 and anode lugs A.sub.21, A.sub.22 are formed on both longitudinal edges 90, 92 of the second sub-cell 82, of which cathode lugs and anode lugs in each case only two cathode lugs K.sub.21, K.sub.22 and anode lugs A.sub.21, A.sub.22 are indicated with dashed lines in a way which is representative of all the others. Between the cathode lugs K.sub.21, K.sub.22 and the anode lugs A.sub.21, A.sub.22 there is a distance of L.sub.2. The distances L.sub.2 between the individual cathode lugs K.sub.21, K.sub.22 and anode lugs A.sub.11, A.sub.12 vary along the longitudinal extent of the second sub-cell 82, in particular as a function of the coil geometry, e.g. helical or serpentine, used, such that the cathode lugs K.sub.21, K.sub.22 and anode lugs A.sub.21, A.sub.22 in the wound state of the second sub-cell 82 ideally lie one on top of the other or lie one against the other again in a congruent fashion.

[0052] FIG. 7 shows a highly simplified plan view of a prismatic cell coil 100 with two sub-cells 10, 32, 42, 44, 52, 54, 68, 70, 80, 82 which can be electrically disconnected from one another by means of the monitoring device 36.

[0053] An exemplary, in turn prismatic, cell coil 100 has on both sides a multiplicity of cathode lugs K.sub.11, K.sub.12, K.sub.21, K.sub.22 and anode lugs A.sub.11, A.sub.12, A.sub.21, A.sub.22 which are not denoted individually and which together form the two upper-side cathode contacts 102, 104 which can be seen here, while two anode contacts lying at the bottom cannot be seen in the illustration in FIG. 6. The first and the second sub-cells 10, 32, 42, 44, 52, 54, 68, 70, 80, 82 of the cell coil 100 are electrically connected independently of one another and actuated via the total of four cathode contacts 102, 104 and anode contacts, wherein the sub-cells 10, 32, 42, 44, 52, 54, 68, 70, 80, 82 are continuously automatically monitored in the “normal operating mode” of the cell coil 100 by means of the automatic monitoring device 36, and in “the event of a fault” can be electrically disconnected from one another immediately by means of said monitoring device 36.

[0054] FIG. 8 shows a basic plan view of an embodiment of a cell coil 200 with four sub-cells 10, 32, 42, 44, 52, 54, 68, 70, 80, 82.

[0055] The cell coil 200 is constructed here by way of example with four sub-cells 10, 32, 42, 44, 52, 54, 68, 70, 80, 82, the cathode lugs K.sub.11, K.sub.12, K.sub.21, K.sub.22 and anode lugs A.sub.11, A.sub.12, A.sub.21, A.sub.22 of which are combined to form four upper-side cathode contacts 202, 204, 206 and 208 which can be seen here, while four lower-side anode contacts are in turn concealed or not visible here.