Low-inductance electrochemical storage elements with integrated capacitive parallel path

Abstract

Battery module (1) comprising a first electrochemical storage element (3); a second electrochemical storage element (5); wherein the first and the second electrochemical storage element (3, 5) are each connectable to an external positive terminal (7) and an external negative terminal (9); characterized in that the battery module (1) further comprises a capacitive parallel path (11) which is connected in parallel to the electrochemical storage elements (3, 5), wherein the capacitive parallel path (11) is designed to set an externally acting impedance of the battery module (1) within a predefinable range of values.

Description

Prior ArtBattery cells, also referred to as rechargeable batteries, serve for the chemical storage of energy provided electrically. In this case, battery cells or battery modules can be used to supply energy to mobile devices.In order to increase a total storage capacity, for example, a multiplicity of battery cells can be assembled to form battery modules and connected or interconnected to one another. An efficient arrangement and circuit of a plurality of storage cells and battery modules can play a role in particular in the field of electromobility, for example in order to increase a range of vehicles. In this case, electrical storage cells can be connected in parallel and / or in series, in order to set the desired voltage levels, energy quantities and performance parameters, for example. In recent years, electrochemical storage cells, for example based on lithium ion technology, are becoming increasingly important because of special properties such as energy density. In most fields of application of electrical storage devices with electrochemical storage processes, apart from a low AC component, also referred to as ripple component, approximately DC current is drawn or fed in.As the alternating current component of the current increases, an influence of the distributed inductance of the battery cell increases. In this case, the inductive component of the impedance acts outwards, for example to the power electronics, and, in combination with high currents during switching operations, leads to high loss energies in semiconductor switches.DE 102012213945 A1 discloses an electrical energy storage cell having a low-inductance, capacitive parallel path connected between poles of the energy storage cell. This is designed as an integral component of the energy storage cell.Disclosure of the InventionThere may therefore be a need for an improved battery module and a corresponding manufacturing method, which make it possible in particular to minimize the inductance acting outwards.This need can be met by the subject matter of the present invention according to the independent claims. Advantageous embodiments of the present invention are described in the dependent claims.Features, details and possible advantages of a device according to embodiments of the invention are discussed in detail below.According to a first aspect of the invention, a battery module is presented. The battery module has a first and at least one second electrochemical storage element. The first and the second electrochemical storage element can each be connected to an external positive pole and an external negative pole. Furthermore, the battery module has a low-inductance capacitive parallel path which is connected in parallel with the electrochemical storage elements.In other words, the concept of the present invention is based on reducing the inductance of the battery module acting outwards by virtue of the fact that, for example, a capacitor which is connected in parallel with the poles of the battery cell is realized by the housing of the battery cells or by cell windings of a battery cell wound in opposite poles.The low-inductance, capacitive parallel path in the battery module advantageously leads, in particular at higher frequencies of the load current, to a lowering of the cell impedance and thus also to a lowering of the inductance acting outwards. In this way, power losses during charging and discharging of the battery module can be reduced or avoided. Overall, the efficiency of the individual batteries and of the entire battery module can thus be increased. Furthermore, the battery module with the capacitive parallel path can continue to be implemented cost-effectively.In this case, no additional lines are required for realizing the capacitive parallel path. Thus, no additional ohmic components and capacitive components are introduced into the battery module. Overall, the equivalent series resistance (ESR) and the equivalent series inductance (ESL) can thus be minimized.As explained in the following, no additional installation space or an only slightly increased installation space is required for the realization of the capacitive parallel path. Thus, the integration of a capacitive parallel path has no effects on modulus levels. That is to say, for example, no structural changes are necessary on the components of a battery pack, such as, for example, on a housing in which a plurality of battery modules are accommodated.In the present application, a battery module can be understood to mean, on the one hand, a module comprising a plurality of, in particular at least two, battery cells. On the other hand, a battery module can be understood to mean a single battery cell which has a housing in which at least two cell coils wound in opposite poles are arranged. Accordingly, the electrochemical storage elements can be embodied on the one hand as individual battery cells or as a cell winding of a battery cell.The first electrochemical storage element can be embodied here, for example, identically to the second electrochemical storage element. For example, both electrochemical storage elements can be embodied as lithium-ion battery cells. Alternatively, the storage elements can be designed differently. For example, the storage elements can be designed as wound cell coils wound in opposite poles.The battery module can be used for supplying energy to mobile devices, in particular motor vehicles. For example, the battery module may be used in electric vehicles and / or in hybrid vehicles. Furthermore, the battery module can serve for the stationary intermediate storage of electrical energy.For example, the battery module can store electrical energy originating from alternative energy sources, such as solar cells.According to one exemplary embodiment of the invention, the capacitive parallel path is designed to minimize an inductance of the battery module acting outwards.According to the invention, the capacitive parallel path is designed to set an outwardly acting impedance of the battery module in a predeterminable value range. That is, the capacitive parallel path is configured to adjust the impedance according to a desired specification. For this purpose, switching elements can be provided on the battery module, which only allow the individual electrochemical storage elements to be switched on and off in such a way that the impedance of the battery module acting outwards lies in a predefined value range.According to a further exemplary embodiment of the invention, the battery module further comprises a first insulating element. The first insulating element is arranged between the first electrochemical storage element and the second electrochemical storage element and electrically isolates the two storage elements from one another.If the electrochemical storage elements are embodied as battery cells, the first insulating element can be arranged between the housings of the battery cells. If, on the other hand, the electrochemical storage elements are designed as cell coils, also referred to as electrode stacks, the first insulating element can be arranged between the cell coils. The first insulating element serves to maximize the capacitance arising between the electrochemical storage elements.According to a further exemplary embodiment of the invention, the first insulating element is embodied as a foil. In this case, the first insulating element can be made thin, for example, in comparison with the dimensions of the electrochemical storage elements. As a result, the first insulating element can be integrated into the battery module without increasing the installation space. Furthermore, the first insulating element can be flexible. In this way, the first insulating element can be optimally adaptable to the geometric characteristics of the electrochemical storage elements.Alternatively, the first insulating element can be embodied as a material layer, in particular as a thin material layer. For example, the first insulating element can be embodied as a lacquer layer.According to a further exemplary embodiment of the invention, the first insulating element has a dielectric constant Eε R > >1. That is to say that the first insulating element has a very high dielectric constant which is substantially greater than 1. For example, the first insulating element could have or consist of tantalum pentoxide with a dielectric constant of ε R= 27. Furthermore, the first insulating element could comprise or consist of titanium dioxide having a dielectric constant of ε R= 80. Furthermore, the first insulating element could comprise or consist of barium titanate with a dielectric constant between Eε R= 1000 and Eε R= 10000. Furthermore, the first insulating element can comprise a combination of the materials mentioned with one another and optionally with further materials. A first insulating element with a high dielectric constant increases the capacitive effect of the parallel path.According to a further exemplary embodiment of the invention, the first electrochemical storage element is arranged in a first electrically conductive housing and the second electrochemical storage element is arranged in a second electrically conductive housing. The capacitive parallel path is realized by the connectivity of the first housing to the external positive pole and the second housing to the external negative pole.In this exemplary embodiment, the first electrochemical storage element is designed as a first battery cell and the second electrochemical storage element is designed as a second battery cell. The battery cells each have a housing which can also be referred to as a cell casing. For example, the housings can comprise a metal or consist thereof. Alternatively, the housings can be made of plastic with integrated electrically conductive elements. The electrically conductive elements can be arranged in the interior of the housing or on the outer periphery of the housing. Alternatively or additionally, the electrically conductive elements can be integrated into the housing. That is to say that the electrically conductive elements can be surrounded by the housing wall.The first electrically conductive housing is electrically insulated from the second electrically conductive housing. For example, this insulation can be realized or supplemented by the first insulating element. The first housing can be arranged spatially in the immediate vicinity of the second housing. The first housing or a part of the first housing can form a first capacitor plate, for example. The second housing or a part of the second housing can form a second capacitor plate. The capacitive parallel path to the electrochemical storage elements arises due to the connection of these capacitor plates to the external positive or negative pole.According to a further exemplary embodiment of the invention, the first electrochemical element is electrically insulated from the first housing by a second insulating element. Furthermore, the second electrochemical element is electrically insulated from the second housing by a second insulating element.For example, the electrodes and the current collectors of the battery cells are electrically insulated from the respective housing. The second insulating element can be embodied, for example, similar to the first insulating element. In particular, the second insulating element can be embodied as a film, in particular as a plastic film. The second insulating member may be attached to the inner wall of the housings, for example, respectively.According to a further exemplary embodiment of the invention, the first housing and optionally also the second housing have a surface structure which maximizes the surface of the respective housing. That is, the surface of the housings is designed such that the active area facing the other housing is increased. For example, the housings can be designed meandering in cross section or concertina-like. In particular, the housings can have depressions and elevations on the housing side facing the respectively adjacent housing.According to a further exemplary embodiment of the invention, the first electrochemical element and the second electrochemical element are embodied as cell coils. The cell coils each have a positive and a negative conductor foil. The capacitive parallel path is realized in this case in that the positive conductor foil of the first electrochemical element can be or is connected to the external positive pole and the negative conductor foil of the second electrochemical element can be or is connected to the external negative pole.In this exemplary embodiment, the electrochemical storage elements are designed as cell coils which are designed, for example, as part of a common battery cell. For example, the first cell coil and the second cell coil may be arranged in a common housing, which is referred to as a third housing.The cell coils can also be referred to as stacks. In the case of lithium-ion battery cells, the cell windings can also be referred to as jellyrolls. The respective adjacent cell coils are wound in opposite polarity. For example, the first electrochemical storage element is constructed from the inside to the outside as follows: negative conductor foil, anode, separator, cathode, positive conductor foil. The second electrochemical storage element can be constructed from the inside to the outside as follows: positive conductor foil, cathode, separator, anode, negative conductor foil.According to a further exemplary embodiment of the invention, the battery module furthermore has control electronics which are integrated into the battery module. The control electronics comprise e.g. power semiconductor switches. The direct integration of the control electronics into the battery module enables the most efficient possible charging and discharging of the electrochemical storage elements.According to a second aspect of the invention, a method of manufacturing a battery module described above is presented. The method comprises the following steps: providing a first electrochemical storage element; providing a second electrochemical storage element; configuring the first and the second electrochemical storage element such that they can be connected to an external positive pole and an external negative pole, respectively; providing a capacitive parallel path which is connected in parallel with the electrochemical storage elements.Further features and advantages of the present invention will become apparent to a person skilled in the art from the following description of exemplary embodiments, which, however, should not be interpreted as limiting the invention, with reference to the enclosed drawings. FIG. 1 shows a schematic illustration of a battery module according to an exemplary embodiment of the invention FIG. 2 shows a plastic view of a battery module according to a further exemplary embodiment of the invention FIG. 3 shows a cross section through the plane indicated in FIG. 2 FIG. 4 shows plan views of different interconnections of the electrochemical storage elements of the battery module FIG. 5 shows a cross section through a battery module according to a further exemplary embodiment of the inventionAll the figures are merely schematic representations of apparatuses according to the invention or their constituent parts according to exemplary embodiments of the invention. In particular, distances and size relationships are not reproduced to scale in the figures. In the various figures, corresponding elements are provided with the same reference numerals.The embodiments illustrated in the figures are based inter alia on the following findings and ideas: as the alternating component of the current through a battery module increases, the influence of the distributed inductance in the storage system increases as a function of frequency. For example, in the case of a rapid change of the current conduction through a battery module, an alternating current component can be generated in addition to the direct current component. Frequencies of such alternating current components can lie in the kilohertz range, for example between 1 and 100 kHz.The inductive portion of the cell impedance can act to the outside of the power electronics and, in combination with high currents during the switching operations, can cause high loss energies in the semiconductor components. In certain switching operations, avalanche breakdown may occur in the semiconductor, driven by the electrical energy stored in the inductances, which is also referred to as avalanche operation. Such effects can lead to increased degradation of the relevant components. In the case of serial connection of the battery cells in a module, the individual cell inductances and the inductances of the cell connectors add up. This can lead to a correspondingly higher avalanche energy and thus to a higher power loss.In general, a high inductance of a battery module can result in relatively strong electromagnetic fields being emitted during each switching operation, which can lead to interference of adjacent electronics.As shown in FIG. 1, thanks to the configuration of the battery module 1 according to the invention with a capacitive parallel path 11 connected in parallel with the electrochemical storage elements 3, 5, the impedance and thus the inductance of the battery module 1 acting outwards can be reduced. In this way, a power loss, in particular in integrated power semiconductor switches based on metal oxide semiconductor field effect transistor (MOSFET), can be minimized. Furthermore, the efficiency of the battery module can thus be increased cost-effectively, with the installation space remaining the same.The capacitance of the parallel path 11 is indicated in FIG. 1 by C P. The battery module 1 may have a battery cell array as shown in FIGS. 2 to 4 or a single battery cell having multiple cell coils as shown in FIG. 5.In FIG. 2, the battery module 1 is designed with three electrochemical storage elements 3, 5. The electrochemical storage elements 3, 5 are designed as battery cells with a positive pole 7 or a positive pole connection and a negative pole 9 or negative pole connection. The second electrochemical storage element 5 is arranged between two first electrochemical storage elements 3. Furthermore, in FIG. 2, the sectional plane of the illustration shown in FIG. 3 is indicated by dashed lines. The battery cells may be arranged in a module housing. This is not shown in FIG. 2.The cross section through the battery module 1 shown in FIG. 3 illustrates the realization of the capacitive parallel path 11 with the aid of the electrically conductive housings 17, 19 of the battery cells. That is, the parallel capacitance C P is realized structurally by the electrical connection of the housings 17, 19 to a current collector 35 and thus to one of the poles 7, 9. The current collector 35 can be connected to a cell connector 33, which in turn can be connected to external consumers or current collectors.In order to realize the most ideal possible capacitive behavior, a first insulating element 13 is arranged between the battery cells. The first insulating element 13 can be embodied, for example, as an electrically insulating layer or film. In this case, the first insulating element 13 can have a very high dielectric constant Eε R. In this way, the capacitance arising between the electrically conductive housings 17, 19 can be maximized. In addition, the structure of opposing surfaces of the housings 17, 19 may be designed such that the active area is increased. For example, the surface can each be made concertina-like in cross section.In order to keep the number of parallel-connected capacitors identical to that of the electrochemical storage elements 3, 5, an additional plate electrode 37 and an additional first insulating element 13 are inserted at one end of the series circuit in the exemplary embodiment in FIG. 3. This additional plate electrode 37 is electrically conductively connected to a homopolar housing 17. In the exemplary embodiment of FIG. 3, the additional plate electrode 37 is arranged at the left end of the series circuit opposite a part of the first housing 17 connected to the negative pole 9. Furthermore, it is connected to a part of the first housing 17 connected to the positive pole 7.The battery cells in the exemplary embodiment of FIG. 3 are designed in such a way that not only the current collectors 35 of the battery cells are electrically conductively connected to the poles 7, 9, but also the electrically conductive housings 17, 19 of the battery cells. The interior of the battery cell, such as the cell windings, is electrically insulated from the housing 17, 19 by a second insulating element 15. The second insulating element 15 can be embodied, for example, as a plastic film. The housing base 21 of the electrically conductive housings 17, 19 can likewise be designed to be electrically insulating. The further geometric structure of the battery cell within the housing 17, 19 can be comparable in the exemplary embodiment of FIG. 3 to the geometric structure of known battery cells.FIG. 4 shows plan views of different interconnections of the electrochemical storage elements 3, 5 of the battery module 1. In the exemplary embodiments of FIG. 4, the electrochemical storage elements 3, 5 are likewise embodied as battery cells.FIG. 4A shows an embodiment in which the housings 17, 19 of the individual battery cells are connected to a positive pole 7. In the exemplary embodiment of FIG. 4A, a capacitance C P or the capacitive parallel path 11 is formed between the housing 17, 19 and an external winding, which is situated on the outside and connected to the negative pole 9, in the interior of the battery cell. The battery cells can be designed, for example, as round cells, as shown in the right-hand region of FIG. 4A. In this case, the cell winding can run concentrically with respect to the housing 17, 19 in the interior of the battery cell.In the exemplary embodiment of FIG. 4B, the housings 17, 19 of the individual battery cells are alternately placed at different potentials. That is, the first housings 17 are connected to the negative pole 9, for example, and the second housings 19 are connected to the positive pole 7. The capacitance C P or the capacitive parallel path 11 is formed between the housings 17, 19.In FIG. 4C, an additional plate electrode 37 is provided in each case in the interior of the individual battery cells or within the housings 17, 19. This can be designed similar to that shown in FIG. 3. The additional plate electrode 37 is connected to the negative pole 9. The housings 17, 19 are, on the other hand, connected to the positive pole 7. The capacitance C P or the capacitive parallel path 11 is formed between the housings 17, 19 and the respective additional plate electrode 37.An alternative configuration of the capacitive parallel path 11 is illustrated in FIG. 5. In FIG. 5, the electrochemical storage elements 3, 5 are designed as cell coils of a battery cell. The cell coils can be arranged, for example, within a common housing 17, 19. The capacitive parallel path 11 is realized directly by the stringing together of cell coils wound with opposite poles. In FIG. 5, the positive conductor foil 23 is located on the first electrochemical storage element 3, i.e. on the first cell winding on the outer jacket of the cell winding. In the case of the second electrochemical storage element 5, i.e. in the case of the second cell winding adjacent to the first cell winding, the negative conductor foil 25 is located on the outer jacket of the cell winding. The conductor foils 23, 25 are connected to the positive pole 7 or to the negative pole 9.Between the cell coils, i.e. between the electrochemical storage elements 3, 5, a first insulating element 13 having a high dielectric constant is arranged. The parallel capacitance is already formed within the battery cell between the cell coils.FIG. 5 also shows an enlarged view of the structure of the cell coils wound in opposite poles. The first cell winding, also referred to as first electrochemical element 3, is constructed from the outside to the inside as follows: positive conductor foil 23, cathode 29, separator 31, anode 27 and negative conductor foil 25.In summary, a capacitive parallel path 11 is realized in the battery module 1. This takes place without the use of additional lines and thus without the introduction of additional ohmic or inductive components into the battery module 1.Finally, it is noted that terms such as "comprising" or the like are not intended to exclude that further elements or steps may be provided. It should also be noted that "a" or "an" do not exclude a plurality. In addition, features described in connection with the various embodiments may be combined with each other as desired. It is further noted that the reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

Battery module (1), the battery module (1) having a first electrochemical storage element (3); a second electrochemical storage element (5); wherein the first and the second electrochemical storage element (3, 5) can each be connected to an external positive pole (7) and an external negative pole (9); characterized in that the battery module (1) further has a capacitive parallel path (11) which is connected in parallel with the electrochemical storage elements (3, 5), wherein the capacitive parallel path (11) is designed to set an outwardly acting impedance of the battery module (1) in a predeterminable value range.The battery module (1) according to claim 1, wherein the capacitive parallel path (11) is configured to minimize an outwardly acting inductance of the battery module (1).The battery module (1) according to any one of claims 1 and 2, further comprising a first insulating member (13); wherein the first insulating member (13) is disposed between the first electrochemical storage element (3) and the second electrochemical storage element (5) and electrically isolates both from each other.The battery module (1) according to claim 3, wherein the first insulating member (13) is formed as a foil.The battery module (1) according to any one of claims 3 and 4, wherein the first insulating member (13) has a dielectric constant Ε R > >1.Battery module (1) according to one of Claims 1 to 5, wherein the first electrochemical storage element (3) is arranged in a first electrically conductive housing (17) and the second electrochemical storage element (5) is arranged in a second electrically conductive housing (19); wherein the capacitive parallel path (11) is realized by the connectivity of the first housing (17) to the external positive pole (7) and of the second housing (19) to the external negative pole (9).The battery module (1) according to claim 6, wherein the first electrochemical element (3) is electrically insulated from the first housing (17) by a second insulating member (15); wherein the second electrochemical element (5) is electrically insulated from the second housing (19) by a second insulating member (15).The battery module (1) according to any one of claims 6 and 7, wherein the first case (17) has a surface structure that maximizes the surface area of the first case (17).Battery module (1) according to one of Claims 1 to 5, wherein the first electrochemical element (3) and the second electrochemical element (5) are designed as cell windings; wherein the cell windings each have a positive conductor foil (23) and a negative conductor foil (25); wherein the capacitive parallel path (11) is realized in that the positive conductor foil (23) of the first electrochemical element can be connected to the external positive pole (7) and the negative conductor foil (25) of the second electrochemical element (5) can be connected to the external negative pole (9).The battery module (1) according to any one of claims 1 to 9, further comprising control electronics; wherein the control electronics is integrated into the battery module (1).Method for producing a battery module (1) according to one of Claims 1 to 10, the method having the following steps: providing a first electrochemical storage element (3); providing a second electrochemical storage element (5); configuring the first and the second electrochemical storage element (3, 5) in such a way that they can be connected in each case to an external positive pole (7) and an external negative pole (9); characterized in that the method furthermore has provision of a capacitive parallel path (11) which is connected in parallel with the electrochemical storage elements (3, 5), wherein the capacitive parallel path (11) is designed to set an outwardly acting impedance of the battery module (1) in a predeterminable value range.

Images