Battery cell and motor vehicle for a battery module

Abstract

The invention relates to a cell for a battery module of an electric vehicle, the cell comprising a plurality of electrodes having a bottom side and at least one side face, at least one cooling element having an abutment face, at least one spacer element and at least one heat-conducting element. The cooling element is thermally connected to the heat-conducting element by means of the abutment face. The bottom side of the electrodes is several times the width of the at least one side face of the electrodes. The spacer element is arranged between the two bottom sides of two adjacent electrodes. The electrodes are thermally connected to the cooling element by means of the heat-conducting element. The at least one cooling element is arranged such that the at least one side face of the electrodes faces in the direction of the abutment face. The at least one heat-conducting element is arranged between the bottom side of the electrodes and the spacer element. The heat-conducting element is designed to have at least two legs. One leg lies flat against one of the bottom sides, while the other leg is designed to be parallel to the abutment face of the cooling element. The width of the abutment face is at least 80% of the width of the side face associated with the abutment face.

Description

Technical Field

[0001] The present invention relates to a battery cell for a battery module of the type given in the preamble of claim 1 and a motor vehicle of the type given in the preamble of claim 10. Background Technology

[0002] Efficiently cooling the battery cells is a key challenge in the development of battery systems for electric vehicles (EVs). Due to increased energy density, compact cell geometry, and dynamic load characteristics, reliable thermal management is crucial for ensuring battery safety, performance, and lifespan. This is especially true for the electrodes where electrochemical reactions occur, which are subjected to intense thermal loads. Insufficient heat dissipation can lead to performance degradation, power loss, and, in the worst case, thermal runaway, jeopardizing battery safety.

[0003] One of the biggest challenges in battery cooling is the uneven heat distribution within cells and between cells in a battery module. Different temperature ranges accelerate the aging of individual cells, leading to imbalances within the battery system. Furthermore, the increased energy density of modern batteries increases thermal resistance, while limited structural space in motor vehicles makes integrating cooling systems difficult. In addition, the dynamic charging and discharging processes require flexible cooling solutions that can adapt to the corresponding thermal loads.

[0004] Typically, heat transfer within a battery cell occurs through the larger sides of the cell's casing. However, the shape of the cell creates narrow sections at its edges, thus interfering with heat transfer. Furthermore, the increased cell wall size results in unfavorable values ​​for the ratio of cell energy content to weight, or the ratio of energy content to total volume.

[0005] As is well known, heat-conducting elements are used for the thermal connection between the battery cell or electrode and the cooling element.

[0006] It is known that, for cooling purposes, additional thermal elements are placed between the cells in the battery system for thermal connection with a cooling plate. This is disclosed in US 2021 / 0313634 A1.

[0007] US 2024 / 0291079 A1 discloses an additional heating element mounted at an electrode, wherein the ends of the additional heating element are connected to a cooling plate.

[0008] In US 2022 / 0021057 A1, additional heating elements are arranged between the cells, and laterally extending fins are connected to cooling elements.

[0009] Due to the rapid development in the battery cell field and the growing demand for more powerful battery systems, further improvements in heat dissipation within battery cells are crucial. Summary of the Invention

[0010] Therefore, the object of this invention is to improve the battery cell of a battery module in such a way that more efficient heat dissipation is ensured while the cell design saves structural space. Furthermore, it should be possible to integrate it into existing cell structures as easily as possible.

[0011] The objective is achieved by combining the features of the feature portion of claim 1 with the features of its preceding portion.

[0012] Advantageous embodiments of the invention are described in dependent claims 2 to 9.

[0013] In a known manner, a cell for a battery module includes multiple electrodes having a bottom surface and at least one side surface, at least one cooling element having a contact surface, at least one separator element, and at least one thermally conductive element. The cooling element is thermally connected to the thermally conductive element via the contact surface. The area of ​​the bottom surface of the electrode is several times the area of ​​the at least one side surface. The electrodes are arranged within a housing of the cell. Separators are arranged between the two bottom surfaces of two adjacent electrodes. The electrodes are thermally connected to the cooling element via the thermally conductive element. At least one cooling element is arranged such that at least one side surface of the electrode faces the contact surface. At least one thermally conductive element is arranged between the bottom surface of the electrode and the separator element. The thermally conductive element is designed to have at least two legs / sides / feet.

[0014] According to the present invention, one leg rests flat against one of the bottom surfaces, while the other leg is designed to be parallel to the resting surface of the cooling element. Here, the width of the resting surface is at least 80% of the width of the side surface. The design of the heat-conducting element ensures that, on the one hand, a large effective heat dissipation area is designed at the electrodes, and on the other hand, a large effective area is designed for connection with the cooling element.

[0015] Preferably, the thermally conductive element is designed as a graphite foil or graphene film. Graphite foil has very high thermal conductivity, especially in-plane thermal conductivity, achieving values ​​exceeding 1000 W / m·K. This ensures rapid heat dissipation within the battery cell. Its high isotropic conductivity in the plane allows for efficient compensation of temperature differences within the battery cell. Furthermore, the thermally conductive element is thus designed to withstand mechanical stresses, such as those generated during temperature cycling, while maintaining its thermal conductivity.

[0016] According to an advantageous design according to the invention, the heat-conducting element is designed as a heat pipe plate or a vapor chamber. Thus, by using the phase change mechanism of these designs, efficient heat removal and uniform temperature distribution are ensured. Here, the heat-conducting element exhibits high thermal conductivity, low space requirements, and high energy efficiency.

[0017] Preferably, the legs of the heat-conducting element are interconnected via rounded corner joints. These rounded corner joints ensure that the heat-conducting element is designed without sharp edges. Sharp edges on the heat-conducting element can lead to uneven heat distribution, potentially causing hot spots or localized overheating. This, in turn, ensures a uniform heat distribution at the transition between the two legs.

[0018] Preferably, a thermally conductive gap-filling element is arranged between the thermally conductive element leg associated with the cooling element and the electrode side surface associated with the cooling element's contact surface. The thermally conductive gap-filling element abuts not only the electrode side surface but also the leg. This allows the fillet radius of the intermediate part to be larger. The gap between the thermally conductive element leg associated with the cooling element and the electrode side surface can be filled by the thermally conductive gap-filling element or gap filler. This eliminates air gaps that insulate against heat and improves thermal conductivity between the electrode side surface and the thermally conductive element leg associated with the cooling element.

[0019] According to another advantageous embodiment of the invention, the electrodes are arranged to form a prismatic cell. Due to its rectangular or cuboid structural form, the prismatic cell can be arranged in a space-saving manner within the battery system. This enables more efficient use of available structural space, particularly in electric vehicle (EV) battery packs. The parallel faces and edges of the prismatic cell facilitate integration and stacking within the battery module, thereby achieving high energy density at the system level. The cell can also be designed as a pouch cell.

[0020] Preferably, the cooling element is designed as a two-piece unit. A first partial cooling element is positioned above the electrode, and a second partial cooling element is positioned below the electrode. A heat-conducting element is thermally connected to one or both partial cooling elements. Thus, by connecting both sides of the electrode to the partial cooling elements, the effective heat dissipation surface is doubled, significantly improving heat dissipation. Furthermore, the additional heat-conducting surface, aided by corresponding heat-conducting element legs connected to the partial cooling elements, enables more efficient cooling, even under high heat loads, and ensures a more uniform temperature distribution.

[0021] Preferably, the thermally conductive element has a thickness of 2 mm or less, particularly 1 mm or less. This ensures a space-saving cell structure.

[0022] According to another advantageous embodiment of the invention, the thickness of the thermally conductive element is smaller than the thickness of the cell separator element. The cell separator element primarily serves an electrical insulation function, while the thermally conductive element is optimized for heat dissipation. The smaller thickness of the thermally conductive element maximizes its efficiency without compromising the function of the cell separator element.

[0023] Another aspect of the invention relates to a motor vehicle comprising at least one battery system acting in conjunction with an electric motor. The battery system has at least one cell as described above. A cooling element is connected to a coolant-based primary cooling circuit. According to the invention, the cooling element is additionally integrated into a secondary cooling circuit of the vehicle. Here, the cooling circuit has a refrigeration unit / chiller. By additionally connecting the cooling element to the coolant-based secondary cooling circuit coupled to the refrigeration unit, and through more efficient thermal connection with the cooling element via electrodes, the temperature of the coolant guided through the coolant circuit is increased, and thus the overall cooling power of the motor vehicle is improved. Furthermore, it is conceivable that the secondary cooling circuit be designed as a refrigerant-based cooling circuit. Attached Figure Description

[0024] Other advantages and application possibilities of the invention will become apparent from the following description of the embodiments shown in conjunction with the accompanying drawings.

[0025] Figure 1 A schematic side view of the battery cell of the battery module according to a first embodiment of the present invention is shown, and

[0026] Figure 2 A schematic side view of the battery cell of the battery module according to a second embodiment of the present invention is shown. Detailed Implementation

[0027] exist Figure 1 and Figure 2 The figures show schematic side views of a portion of the battery cell 10 according to the invention. The battery cell 10 has a housing, not shown.

[0028] Here, the cell 10 has multiple electrodes 12 of the same type. The electrodes 12 are designed as cuboids with two bottom surfaces 12a and four side surfaces 12b. The area of ​​the bottom surface 12a is several times the area of ​​the side surfaces 12b. The cell 10 is designed as a prismatic cell. The cell 10 can also be designed as a pouch cell. The electrodes 12 are arranged such that the bottom surfaces 12a are perfectly aligned, and the side surfaces 12b of the electrodes 12 are designed to be parallel to each other. Each electrode 12 contains an active material. For example, lithium nickel manganese cobalt oxide (NMC) or lithium iron phosphate (LFP) can be used for the positive electrode. For example, graphite or a silicon-graphite mixture can be used for the negative electrode.

[0029] Separating elements 14 are arranged between the electrodes 12. Each separating element 14 has two bottom surfaces 14a and four side surfaces 14b. The area of ​​the bottom surface 14a is several times the area of ​​the side surfaces 14b. The separating elements 14 are attached to the bottom surface 12a of the electrodes 12 using one of their bottom surfaces 14a.

[0030] Furthermore, heat-conducting elements 16 are arranged between the separator element 14 and the electrode 12. Each heat-conducting element 16 has two legs 18 and 20. The legs 18 and 20 are interconnected via a rounded corner intermediate member 22. The first leg 18 has two bottom surfaces 18a and three free side surfaces 18b. The first leg 18 rests against the other bottom surface 12a of the electrode 12 using one of its bottom surfaces 18a. The other bottom surface 18a of the first leg 18 rests against the other bottom surface 14a of the separator element 14.

[0031] A cooling element 24 is arranged on the upper side of the battery cell 10. Here, the cooling element 24 is thermally connected to the refrigerant-based primary cooling circuit of the vehicle. The cooling element 24 can also be connected to an additional refrigerant-based secondary cooling circuit. The cooling element 24 can be designed as a cooling plate.

[0032] The cooling element 24 is thermally connected to the heat-conducting element 16 directly or indirectly via a contact surface 24a. Here, the width of the contact surface 24a is at least 80% of the width of the side surface 12b of the electrode 12 associated with the cooling element 24.

[0033] The thickness of the heat-conducting element 16 is smaller than that of the separating element 14, wherein the thickness of the heat-conducting element 16 is less than 2 mm.

[0034] exist Figure 1 The diagram shows a first embodiment of the battery cell 10. Here, the heat-conducting element 16 is designed as a graphite foil. However, the heat-conducting element 16 can also be designed as a graphene film.

[0035] In a first embodiment of the cell 10, a leg 20 parallel to the cooling element 24 rests planarly on one side of the electrode 12 associated with the cooling element 24. The other side of the leg 20 is connected to a thermally conductive gap-filling element 26. The thermally conductive gap-filling element 26 is designed to be parallel to the cooling element 24 and has a thickness less than that of the cooling element 24. The thermally conductive gap-filling element 26 is designed as a gap filler, thus possessing flexibility in addition to thermal conductivity to compensate for measurement tolerances and reduce vibration. The thermally conductive gap-filling element 26 is designed as a continuous plate planarly connected to the cooling element 24. Therefore, in addition to being planarly connected to the bottom surface 12a of the electrode 12 via the first leg 18, the thermally conductive element 16 is also planarly connected to the side surface 12b associated with the cooling element 24. Additionally, the intermediate piece 22 of the thermally conductive element 16 also rests on the rounded edge of the electrode 12 between the side surface 12b and the bottom surface 12a. Therefore, the active surface for dissipating heat from the electrode 12 via the heat-conducting element 16 is designed to be large. As a result, heat is directed to the cooling element 24 via the thermally conductive gap-filling element 26 and the legs 20 of the heat-conducting element 16.

[0036] exist Figure 2 The diagram shows a second embodiment of the battery cell 10. Here, the heat-conducting element 16 is designed as a heat pipe plate or a vapor chamber.

[0037] Compared to the structure of the cell 10 in the first embodiment, the heat-conducting element 16 is designed to have a larger thickness. Furthermore, the intermediate member 22 has a larger radius. The heat-conducting gap-filling element 26 is designed as a multi-piece structure. The support leg 20 is planarly attached to the cooling element 24 on one side, and planarly attached to the heat-conducting gap-filling element 26 on the other side. The heat-conducting element 16 is directly planarly connected to the cooling element 24. To compensate for possible tolerances, air gaps, or vibrations, the heat-conducting gap-filling element 26 is arranged between the support leg 20 and the electrode side surface 12b associated with the cooling element 24. Therefore, heat transfer of the heat-conducting element 16 is achieved, on the one hand, directly through the bottom surfaces 12a and 18a, and on the other hand, through the indirect connection between the electrode side surface 12b and the support leg 20 via the heat-conducting gap-filling element 26.

[0038] The cooling element 24 can also be designed as a two-piece unit, each formed by two opposing partial cooling elements. The partial cooling elements are respectively arranged on the opposing side 12b of the electrode 12. Thus, the heat-conducting element 16 has three legs, two of which are designed to be parallel to the partial cooling elements and thermally connected to them through corresponding contact surfaces.

[0039] Furthermore, in a motor vehicle, the battery cell 10 can be connected such that the cooling element 24 is integrated on one hand into the vehicle's coolant-based primary cooling circuit, and on the other hand, additionally integrated into the vehicle's coolant-based secondary cooling circuit. Here, the secondary coolant circuit has a refrigerator that additionally cools the coolant used for the cooling element 24 via the secondary cooling circuit.

[0040] By designing the cell 10 to have the described heat-conducting element 16, efficient and high-performance heat dissipation within the cell can be achieved, wherein the geometric design of the heat-conducting element 16 also enables a space-saving cell 10.

Claims

1. A cell (10) for a battery module in an electric vehicle, the cell comprising a plurality of electrodes (12) having a bottom surface (12a) and at least one side surface (12b), at least one cooling element (24) having a contact surface (24a), at least one separating element (14), and at least one heat-conducting element (16), wherein, The cooling element (24) is thermally connected to the heat-conducting element (16) via a contact surface (24a), wherein the bottom surface (12a) of the electrode (12) is several times the length of at least one side surface (12b) of the electrode (12), wherein a partition element (14) is arranged between the two bottom surfaces (12a) of two adjacent electrodes (12), wherein the electrodes (12) are thermally connected to the cooling element (24) via the heat-conducting element (16), wherein at least one cooling element (24) is arranged such that at least one side surface (12b) of the electrode (12) faces the contact surface (24a), wherein at least one heat-conducting element (16) is arranged between the bottom surface (12a) of the electrode (12) and the partition element (14), wherein the heat-conducting element (16) is designed to have at least two legs (18, 20). Its features are, One leg (18) rests against one of the bottom surfaces (12a), while the other leg (20) is designed to be parallel to the abutment surface (24a) of the cooling element (24), wherein the width of the abutment surface (24a) is at least 80% of the width of the side surface (12b) associated with the abutment surface.

2. The battery cell according to claim 1, characterized in that, The thermally conductive element (16) is designed as a graphite foil or graphene film.

3. The battery cell according to claim 1, characterized in that, The heat-conducting element (16) is designed as a heat pipe plate or a vapor chamber.

4. The battery cell according to any one of the preceding claims, characterized in that, The legs (18, 20) are interconnected by rounded corner intermediate parts (22).

5. The battery cell according to any one of the preceding claims, characterized in that, A thermally conductive gap filling element (26) is arranged between the leg (20) of the thermally conductive element (16) associated with the cooling element (24) and the side surface (12b) of the electrode (12) associated with the contact surface of the cooling element (24), wherein the thermally conductive gap filling element (26) not only abuts against the side surface (12b) of the electrode (12) but also abuts against the leg (20).

6. The battery cell according to any one of the preceding claims, characterized in that, The electrodes (12) are arranged to form a prismatic battery cell.

7. The battery cell according to any one of the preceding claims, characterized in that, The cooling element (24) is designed as a two-piece unit, wherein the first part of the cooling element is arranged above the electrode (12) and the second part of the cooling element is arranged below the electrode (12), wherein the heat-conducting element (16) is thermally connected to one or both parts of the cooling element.

8. The battery cell according to any one of the preceding claims, characterized in that, The thermally conductive element (16) has a thickness of less than or equal to 2 mm, and in particular less than or equal to 1 mm.

9. The battery cell according to any one of the preceding claims, characterized in that, The thickness of the heat-conducting element (16) is less than the thickness of the separating element (14).

10. A motor vehicle comprising at least one battery system acting in conjunction with an electric motor, wherein, The at least one battery system has at least one cell (10) according to any one of the preceding claims, wherein the cooling element (24) is integrated into the primary cooling circuit based on the coolant of the motor vehicle. Its features are, The cooling element (24) is additionally integrated into the coolant-based secondary cooling circuit of the motor vehicle, wherein the cooling circuit has a refrigeration unit.

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