Heat exchanger for battery cells of a high-voltage storage system

Abstract

The invention relates to a heat exchange device (10) for battery cells (20) of a high-voltage storage system, comprising at least two wall elements (11) which are connected to each other in such a way that the wall elements (11) form a flow space (12) for a fluid (F) and at least one of the wall elements (11) is flexible, wherein the heat exchange device (10) has at least one spacer element (14).

Description

[0001] The invention relates to a heat exchange device for battery cells of a high-voltage storage system, comprising at least two wall elements which are connected to each other in such a way that the wall elements form a flow space for a cooling fluid and at least one of the wall elements is flexible.

[0002] High-voltage storage systems, also known as traction batteries or accumulators, are used to provide electrical energy for powering electric vehicle drives. The performance and lifespan of lithium-ion batteries, in particular, are temperature-dependent. In high-voltage storage structures of electric vehicles, battery cells are cooled and / or heated, for example, by means of cooling coils containing coolant located between or on the battery cells. To facilitate heat exchange between these cooling coils and the battery cells, they are typically made of metal and therefore require electrical insulation. Coolers made of plastic are also known. In the future, flexible cooling solutions, such as flexible coolers or pouch coolers, which can be manufactured using a similar production process to pouch battery cells, are becoming increasingly prevalent.In this process, film properties such as bendability can be used.

[0003] A battery structure, or jelly roll, undergoes volume growth during the charge-discharge cycle and over its lifetime. In cylindrical battery cells, this growth manifests inwards, particularly due to the high mechanical integrity of their casing. In pouch and prismatic battery cells, the forces caused by this volume growth, which can deform the casing or encapsulation and thus act outwards, must be absorbed.

[0004] Against this background, an object of the invention is to improve a heat exchange device for battery cells of a high-voltage storage system. In particular, such a heat exchange device is to be improved in order to enable improved heat exchange with the high-voltage storage system.

[0005] This problem is solved by a heat exchange device for battery cells of a high-voltage storage system with the features of claim 1, a battery cell arrangement for a high-voltage storage system with the features of claim 9, and a high-voltage storage system for a motor vehicle with the features of claim 11. The dependent claims relate to advantageous embodiments of the invention.

[0006] According to a first aspect, a heat exchange device for battery cells of a high-voltage storage system is specified, comprising at least two wall elements which are connected to each other in such a way that the wall elements form a flow space for a cooling fluid and at least one of the wall elements is designed to be flexible, wherein the heat exchange device has at least one spacer element which is configured to provide at least sectionally a predetermined minimum flow cross-section for the flow space.

[0007] The flexible design of at least one wall element allows for maximizing the common surface area of ​​the wall element, and thus of the flow chamber, with at least one adjacent battery cell. This increases the heat transfer surface and improves cooling performance. By incorporating the spacer element, a minimum cross-sectional area for coolant flow can be provided, particularly when external forces act on the heat exchanger and / or the flow chamber. This minimum flow cross-section can be dimensioned to ensure a consistently high flow rate of coolant, thereby enabling necessary temperature control of the battery cells, especially in cases of degenerative cell deformation ("swelling").

[0008] According to a further aspect, a battery cell arrangement for a high-voltage storage system is specified, comprising a number of battery cells, wherein at least one heat exchanger according to one of the preceding claims is arranged for heat transfer on one of the battery cells, the battery cells being designed in particular as prismatic battery cells and / or pouch cells. In such battery cells, swelling effects can affect the external geometry or volume of the battery cell, which can in particular cause an increase in the external geometry or volume, such that an outwardly acting force must be supported. Swelling in battery cells refers in particular to a phenomenon in which a battery cell experiences an increase in volume due to internal chemical reactions during the charging and discharging process.This swelling frequently occurs in lithium-ion batteries, particularly due to the formation of gases or the deposition of solids within the cell. This can exert force or pressure on one or more heat exchangers located on the battery cell(s), thereby reducing the cross-sectional area through which fluid can flow.

[0009] The invention is based, among other things, on the idea of ​​providing at least one spacer element on and / or in the heat exchanger to ensure that a minimum flow cross-section is provided within the heat exchanger and / or its flow space, even when battery cells expand. The spacer element is specifically designed to maintain a predetermined spatial separation between the walls so that the flow of (temperature control) fluid is not impaired by undesirable constrictions. The at least one spacer element can have various shapes, such as rings, struts, or grids, and is strategically positioned to maintain the necessary cross-section for the flow. This allows the spacer element to prevent, in particular, the flexible or...movable wall, compressed by pressure or force from expanding battery cells and obstructing the flow.

[0010] Because the spacer element can maintain a constant flow cross-section, at least in certain sections, the flow velocity and / or pressure loss in the heat exchanger and / or heat exchange system can remain predictable. This can increase the service life of the battery cell and / or high-voltage storage system. Careful design and / or positioning of this spacer element can be crucial for the overall system's functionality. Examples are described below.

[0011] According to a further aspect, a high-voltage storage device for a motor vehicle is proposed, comprising at least one battery cell arrangement and / or at least one heat exchanger as described herein. The high-voltage storage device is, in particular, an energy storage device or a traction battery for a motor vehicle, which comprises several battery cells. A housing of the high-voltage storage device defines an internal storage space in which, in particular, prismatic battery cells and / or pouch cells are accommodated or arranged. The prismatic battery cells and / or pouch cells are, in particular, arranged or provided in a packing arrangement or cell packing described herein.

[0012] A high-voltage storage system is, in particular, an energy storage device or traction battery for a motor vehicle, comprising multiple battery cells. The housing of the high-voltage storage system defines an interior space in which the battery cells or battery cell array are housed. Prismatic battery cells and / or pouch cells are primarily used, which can be provided in a packing arrangement or cell pack. When installed in a motor vehicle, the high-voltage storage system and / or the battery cells can be arranged such that the vertical axes or side walls of the battery cells are parallel to a vehicle vertical axis.

[0013] A pouch cell is a battery cell that has a flexible and / or flat casing, packaging, or encapsulation, such as an aluminum-plastic foil. This design allows for high volumetric and gravimetric energy density because the casing is very light and takes up little space. Pouch cells can, however, tend to develop visible deformations and, in particular, an increase in volume when experiencing swelling or gas formation. A prismatic battery cell is a battery cell design that has a rigid, essentially rectangular casing, usually made of metal or plastic. This casing can form a stable structure that protects the battery cell against mechanical influences and / or improves heat dissipation and temperature control. Prismatic cells are generally densely packed, which can lead to a higher energy density per unit volume.Due to their structure, they can withstand greater stress during thermal expansion or swelling compared to more flexible battery cells.

[0014] The proposed heat exchange device can be arranged to be located on or adjacent to at least one battery cell in such a way that heat transfer or the transport of energy in the form of heat is enabled between the battery cells and the heat exchange device and / or to a fluid flowing in the heat exchange element or its flow chamber. In particular, heat conduction through mechanical contact is provided, although in some embodiments heat transfer by convection and / or thermal radiation may also be provided.

[0015] The heat exchange device can, for example, be designed as an at least partially flexible or malleable heat exchange device, in particular a heat exchange pouch, with at least one flexible wall that can be arranged in a space between the cells, and / or it can be designed as a heat exchange plate that can be arranged at the end face of the battery cells of the cell pack. In particular, the at least one heat exchange device can be connected to, or is connected to, a heat sink outside the cell pack or the high-voltage storage module via a fluid flowing therein, so that heat can be dissipated from the cell pack or the high-voltage storage module by means of the fluid. The positive connection to the battery cell can be provided by the malleability of the flexible wall, and in some embodiments, a thermally conductive paste can be arranged between the wall and the battery cell.To improve the positive locking, for example, a high coolant pressure can be applied from the inside, especially once at the beginning of the service life, at intervals or permanently.

[0016] In one embodiment, the spacer element is configured to provide a minimum distance between the two wall elements, at least partially predetermined. The spacer element can be designed as a rigid structure configured to partially or completely prevent physical compression of the wall elements or walls, thus allowing fluid flow in the flow chamber. The spacer element can be configured to create a predetermined distance between the flow chamber or flow cross-section in its flow direction and / or in the transverse direction. Furthermore, the at least one spacer element can be configured to absorb a mechanical load that may act on the heat exchanger or flow chamber from the battery cells.

[0017] In one embodiment, both wall elements are flexible. The heat exchange device can be designed, in particular, as a pouch cooler or pouch cooling device, wherein a pouch cooler has a flexible and / or flat housing or casing, which can be formed from the wall elements connected, in particular by means of joints, and fastened or welded together to form the flow space between the wall elements. Such a pouch cooling device can be arranged to be in direct contact with a battery cell in order to exchange thermal energy, in particular uniformly, across a surface of the battery cell.The inclusion of at least one spacer element thus enables a minimum flow cross-section and / or a uniform fluid distribution within the flow space, thereby maintaining a constant fluid flow and thus a constant temperature control performance.

[0018] In one embodiment, at least one of the wall elements is designed as a foil, in particular an aluminum-plastic composite foil. This allows thermal conductivity and mechanical flexibility to be utilized for heat transfer. The foils can be arranged parallel to each other in their surface area and connected at least circumferentially and / or at further connection points to form the flow chamber. The connection points, particularly along the longitudinal extent of the heat exchanger, can be arranged parallel to each other to enable a meandering flow pattern via the flow chamber or the spacer elements.

[0019] In one embodiment, the spacer element is arranged at least partially between the two wall elements. This allows the at least one spacer element to be located in or within the flow chamber(s), with the two wall elements together with the at least one spacer element forming the flow chamber or a flow path. The spacer element can, for example, be designed with a meandering geometry to form a flow path for a fluid flowing in the flow chamber and / or to serve as a flow element. In other embodiments, the at least one spacer element can be designed as a pin, which in particular penetrates both wall elements and is partially located outside the wall elements or the flow chamber, with the at least one pin being fluid-sealed to or enclosed by the wall element(s).This at least one pin can, especially in its longitudinal extension, provide mechanical stability to the outside in order to counteract compression or stress from the battery cells.

[0020] In one embodiment, the at least one spacer element is arranged outside the two wall elements. Here, the spacer element can, for example, be designed as a frame that can be arranged on an outer cross-section of the heat exchanger in order to avoid mechanically influencing it or the flow chamber and simultaneously to provide stabilization against externally acting pressure forces. In other embodiments, the at least one spacer element can be arranged outside the flow chamber in such a way that its flow geometry can be predetermined by the at least one spacer element.

[0021] In one embodiment, the at least one spacer element is arranged in the area of ​​at least one connection point of the wall elements. Here, for example, if the wall elements are welded together, such weld points or areas can be designated as connection points. The at least one spacer element can be arranged at the connection point or area before and / or after the welding process in order to enhance a flow geometry of the heat exchanger and / or to avoid influencing it.

[0022] In one embodiment, the spacer element has a predetermined stiffness and / or compressive strength. Here, the compressive strength can describe the spacer element's resistance to pressure-induced deformation and indicate the degree to which the spacer element can be compressed before it undergoes, in particular, permanent deformation or failure. This allows the force profile of the at least one spacer element to be adjustable in order to counteract compressive forces exerted by the battery cells, especially those caused by swelling. For example, this allows the deformation of the spacer element to be designed to be adjustable in order to provide a swelling-resistant heat exchanger or pouch cooler. In other embodiments, the at least one spacer element can have defined deformation properties to prevent pressure-induced damage to the battery cells.

[0023] In one embodiment, a heat exchanger is arranged between two battery cells of the battery cell assembly. This allows the heat exchanger and / or the battery cells to be in contact, for example, at their sides with the largest cross-sectional area, thus facilitating thermal exchange. In particular, several heat exchangers can be arranged parallel to each other and between battery cells, for example, to be supplied with fluid via a supply and return line on both sides of the heat exchanger. In some embodiments, the supply and return lines can be located on one side of the heat exchanger. By providing at least one spacer element in and / or on the heat exchanger, such an arrangement can, in particular, counteract the simultaneous load of two adjacent battery cells on the heat exchanger.

[0024] According to a further aspect, a motor vehicle is proposed comprising a high-voltage storage device described herein, at least one heat exchanger described herein, and / or at least one battery cell arrangement described herein. The effects and / or advantages, particularly regarding extended service life, can be utilized by means of such a motor vehicle.

[0025] Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the figures. Fig. Figure 1 shows a schematic representation of an embodiment of a heat exchange device for battery cells of a high-voltage storage system according to the present invention. Fig. Figures 2a and b each show an embodiment of a heat exchange device for battery cells of a high-voltage storage system according to the present invention. Fig. Figure 3 shows a schematic representation of an embodiment of an arrangement of heat exchange devices for battery cells according to the present invention.

[0026] Fig. Figure 1 shows a heat exchange device 10 for a high-voltage storage device with a plurality of battery cells according to a first embodiment of the present invention in a schematic sectional view.

[0027] The heat exchanger 10 has a first wall element 11 and a second (not shown) wall element, which are connected to each other by means of connection points 13 such that they form a flow chamber 14 for a fluid F. In the present embodiment, both wall elements 11 are flexible or made of a film, so that the heat exchanger 10 is designed as a pouch cooler. Here, the fluid F can flow, for example, via an inlet 112 along a flow direction, defined here by a meandering flow chamber 12, to an outlet 212 in order to enable thermal exchange with battery cells arranged on the heat exchanger 10.

[0028] Spacer elements 14 are arranged at the connection points 13. These spacers are designed to provide a predetermined minimum flow cross-section for the flow chamber 12 or to maintain a predetermined minimum distance between the two wall elements 11. This allows the spacer elements 14 to maintain a flowable cross-section, particularly when an external force is applied to the flow chamber 12, thus enabling the temperature control of thermally connected battery cells, especially continuously. This can improve the service life, particularly in the event of swelling of the battery cells, the heat exchanger, or a high-voltage storage system.

[0029] The Fig. 2a and Fig. Figure 2b shows partial sections of a battery cell arrangement 30 for a high-voltage storage system with a heat exchanger 10 for a high-voltage storage module with a number of battery cells 20 according to the first and a second embodiment in a schematic cross-sectional view along an exemplary section AA. Fig. 1.

[0030] This shows Fig. 2a, that a heat exchanger 10 is arranged between two battery cells 20, which are prismatically shaped as an example, in order to transfer thermal energy between the heat exchanger 10 and the battery cells 20. It can be seen that spacer elements 14 are arranged adjacent to each other in the transverse direction at the connection points 13 of the wall elements 11. The spacer elements 14, together with the connection point 13, form a mechanical stabilization in the transverse direction in order to absorb a pressure load, in particular a swelling-related pressure load S originating from the battery cells 20, on the heat exchanger 10 or its wall elements 11 and to provide a minimum cross-section for the flow space 12 or flow spaces 12.It may be provided that the spacer elements 14 are applied during the welding process to create the connection points 13, or that the spacer elements 14 are subsequently arranged as separate components in the area of ​​the connection points 13 in order to provide at least a predetermined minimum distance between the two wall elements 11 in sections.

[0031] Fig. Figure 2b shows a heat exchanger 10 arranged between two battery cells 20, which are exemplary pouch cells in this illustration, to transfer thermal energy between the heat exchanger 10 and the battery cells 20. It can be seen that the connection points 13 of the wall elements 11 are arranged transversely adjacent to the spacer elements 14 to provide a minimum cross-section for the flow chamber 12 or chambers 12. The spacer elements 14 are arranged between the two wall elements 11 to also facilitate flow guidance within the flow chamber 12.

[0032] Fig. Figure 3 shows an arrangement of heat exchange devices 10 for a battery cell arrangement 30 for a high-voltage storage system according to an exemplary embodiment in a schematic perspective view.

[0033] The heat exchange devices 10, connected by means of a supply line 31 (inlet) and a discharge line 32 (return) for fluid F, are arranged parallel to one another, with at least one battery cell 20 being able to be arranged in the space between each pair of adjacent heat exchange devices 10. This allows a battery cell arrangement 30 to be provided for a high-voltage storage system, which, in particular through the design of the spacer elements 14 on or in the heat exchange devices 10, can ensure improved cooling and / or heat exchange performance and thus extend the service life of the high-voltage storage system. REFERENCE MARK LIST 10 Heat exchanger 11 wall element 12 Flow chamber 13 liaison point 14 spacer element 20 battery cells 30 battery cell arrangement 31 Supply line 32 Drain line 112 Admission 212 Outlet F Fluid S pressure load

Claims

[1] Heat exchange device (10) for battery cells (20) of a high-voltage storage system, comprising at least two wall elements (11) connected to each other in such a way that the wall elements (11) form a flow space (12) for a fluid (F) and at least one of the wall elements (11) is flexible, wherein the heat exchange device (10) has at least one spacer element (14) which is configured to provide at least sectionally a predetermined minimum flow cross-section for the flow space (12). [2] Heat exchange device (10) according to the preceding claim, wherein the spacer element (14) is configured to provide at least a predetermined minimum distance between the two wall elements (11) in sections. [3] Heat exchange device (10) according to one of the preceding claims, wherein both wall elements (11) are designed to be flexible. [4] Heat exchange device (10) according to one of the preceding claims, wherein at least one of the wall elements (11) is designed as a foil. [5] Heat exchange device (10) according to one of the preceding claims, wherein the spacer element (14) is arranged at least partially between the two wall elements (11). [6] Heat exchange device (10) according to one of claims 1 to 4, wherein the spacer element (14) is arranged outside the two wall elements (11). [7] Heat exchange device (10) according to one of the preceding claims, wherein the spacer element (14) is arranged in the area of ​​at least one connection point (13) of the wall elements (11). [8] Heat exchange device (10) according to one of the preceding claims, wherein the spacer element (14) has a predetermined stiffness. [9] Battery cell arrangement (30) for a high-voltage storage device, comprising a number of battery cells (20), wherein at least one heat exchange device (10) according to one of the preceding claims is arranged for heat transfer on one of the battery cells (20), wherein the battery cells (20) are in particular designed as prismatic battery cells and / or pouch cells. [10] Battery cell arrangement (30) according to the preceding claim, wherein the heat exchange device (10) is arranged between two battery cells (20) of the battery cell arrangement (30). [11] High-voltage storage device for a motor vehicle, comprising at least one battery cell arrangement (30) according to one of the three preceding claims and / or at least one heat exchange device (10) according to one of claims 1 to 7.

Images