Energy storage arrangement

Abstract

An energy storage arrangement (1), comprising a plurality of energy storage cells (2) which each have electrical poles (3) and at least one emergency opening (4), at least one covering element (5) which covers the electrical poles (3) and has openings (6) which are associated with the emergency openings (4) being arranged on the energy storage cells (2).

Description

[0001] Energy storage arrangement

[0002] The invention relates to an energy storage arrangement comprising a plurality of energy storage cells, each of which has electrical poles and at least one emergency opening.

[0003] Energy storage cells with emergency openings are known, for example, from EP 3 128 579 A1. Energy storage devices, especially rechargeable storage devices for electrical energy, are widely used, especially in mobile systems.

[0004] Rechargeable energy storage cells for electrical energy are used, for example, in portable electronic devices such as smartphones or laptops. Furthermore, rechargeable energy storage devices are used to provide energy for electrically powered vehicles. The spectrum of electrically powered vehicles extends from passenger cars to two-wheelers, small vans, and trucks. Applications in robots, ships, aircraft, and mobile machinery are also conceivable. Other areas of application for electrical energy storage devices include stationary applications, for example, for uninterruptible power supply in IT systems, in network stabilization systems, and for storing electrical energy from renewable energy sources.

[0005] A frequently used energy storage system is based on energy storage devices in the form of lithium-ion batteries. Like other rechargeable energy storage devices, lithium-ion batteries usually have multiple storage cells that together form a module. In addition to lithium-ion batteries, other possible options include lithium-sulfur batteries, solid-state batteries, sodium-ion batteries, batteries based on other light metals such as magnesium or aluminum, and even metal-air batteries.

[0006] Electrical energy storage devices exhibit their highest electrical capacity and best power input and output only within a limited temperature range. If the optimal operating temperature range is exceeded or undershot, the capacity, power input, and power output of the storage device drop significantly, and its functionality is impaired. Excessively high temperatures can also cause irreversible damage to the energy storage device. Accordingly, persistent elevated temperatures and short-term temperature peaks should be avoided. For example, with lithium-ion batteries, persistent temperatures of more than 50°C and short-term temperature peaks of more than 80°C should not be exceeded.

[0007] Particularly for applications in passenger cars or commercial vehicles, rapid charging capability of energy storage devices is required. The energy storage devices should be fully or almost fully charged within a short period of time, for example, within 15 minutes. Due to the charging system's efficiency, which ranges from a maximum of 90% to 95%, large amounts of heat are released in the energy storage device during the charging process, which must be dissipated from the energy storage device. Therefore, it is usually necessary to temperature-control energy storage devices.

[0008] Excessively high temperatures, internal and external short circuits, or mechanical damage to the cells can trigger irreversible damage to the energy storage devices. In this context, what is known as thermal runaway is particularly common with lithium-ion batteries. This process releases large amounts of thermal energy and gaseous reaction products in a short period of time, resulting in high pressure and high temperatures in the housing of an energy storage cell. For this reason, energy storage cells usually have emergency vents through which excess pressure can be relieved. The development of energy storage devices with high energy density, such as those required to provide electrical energy in electrically powered vehicles, has significantly increased the release of gases even in the event of a malfunction.To release excess pressure, energy storage cells with a metallic housing can be equipped with an emergency vent, which can be designed, for example, in the form of a rupture disc. In the event of a failure, the pressure and temperature inside an energy storage cell rise sharply. If a predetermined pressure is exceeded, e.g. if the rupture disc ruptures, the emergency vent opens and harmful gases can escape from the interior of the energy storage cell. The emergency vent can prevent the energy storage cell from opening uncontrollably and exposing neighboring energy storage cells to excessive thermal and mechanical stress. In the event of thermal runaway, not only hot gases with temperatures that can exceed 1,000 °C depending on the cell chemistry used, but also electrically conductive particles are ejected from an emergency vent.These are, for example, carbon particles or metallic or metal oxide particles or metallic melt products.

[0009] However, this poses a problem because electrically conductive particles can accumulate on the electrical connectors or contacts of the energy storage cells. This can cause the connectors or contacts to short-circuit due to particles escaping from the interior of an energy storage cell. The problem is that the released particle streams cause very strong thermal and abrasive stress. Simple insulation materials such as plastic housings or heat-shrink tubing can be damaged, exposing the underlying electrical structures.

[0010] This poses the risk of thermal runaway of other energy storage cells. The release of gases or particles from a broken cell can cause a short circuit in another cell in the energy storage system. The invention is based on the object of providing an energy storage arrangement with a high degree of operational reliability.

[0011] This object is achieved by the features of claim 1. The subclaims refer to advantageous embodiments.

[0012] The energy storage arrangement according to the invention comprises a plurality of energy storage cells, each of which has electrical poles and at least one emergency opening, wherein at least one cover element is arranged on the energy storage cells, which covers the electrical poles and which has openings associated with the emergency openings.

[0013] The cover element covers the electrical poles in such a way that the electrical poles are better protected from external influences and that no electrically conductive particles can accumulate on the electrical poles. This applies in particular to electrically conductive particles that can escape from the interior of an energy storage cell in the event of damage. The opening in the cover element ensures that the excess pressure in an energy storage cell can be safely dissipated in the event of damage. Harmful gases are released in a defined manner via the emergency opening and removed from the energy storage cells. The cover element protects the poles of the energy storage system from the effects of electrically conductive particles and prevents the harmful gases and the particles carried with the harmful gases from accumulating on the electrical poles.

[0014] The cover element can also be designed to withstand hot and abrasive particle streams. When the cover element comes into contact with such particle streams, it neither melts nor forms electrically conductive thermal degradation products. Thermoplastic materials, for example, can be used for this purpose. Alternatively, carbon-based polymers or thermosets can also be considered, in which electrically conductive carbon structures are formed through pyrolysis processes.

[0015] The energy storage cells can be designed as prismatic cells. Prismatic cells have a cuboid-shaped housing in which an electrode unit is arranged, with the housing closed by a lid. Electrical contact between the energy storage cells is established via the electrical poles, which are usually located in the lid. The emergency opening can be located between the two electrical poles in the lid. Prismatic cells can be arranged side by side to save space.

[0016] Adjacent energy storage cells can be electrically connected to one another via at least one cell connector. Energy storage cells connected to one another in this way form a module, wherein, depending on the electrical connection, an increase in the electrical voltage or an increase in the capacity is possible. Within the energy storage arrangement forming a module, the energy storage cells are preferably connected in series, so that the electrical voltage of the energy storage arrangement is increased. In the case of a lithium-ion rechargeable battery, the electrical voltage of a single energy storage cell is approximately 3.6 volts, and by connecting several energy storage cells in series, the electrical voltage can be significantly increased. Furthermore, it is conceivable to connect several modules, each containing energy storage cells connected in series, in parallel.

[0017] In the case of a series connection, a cell connector covers each of two opposite poles of adjacent energy storage cells. Neighboring cell connectors must be prevented from making electrical contact, as this would lead to a short circuit. This is particularly problematic in the event of damage, as the distance between adjacent cell connectors is particularly small. However, the cover element ensures reliable electrical insulation of adjacent cell connectors, so that a short circuit can be avoided even in the event of damage. The cover element preferably covers the cell connectors. This ensures that no electrically conductive particles or the like can accumulate on the cell connectors, which could undesirably electrically connect adjacent cell connectors and lead to a short circuit.

[0018] The opening in the cover element can be designed as a perforation that can be aligned with the emergency opening of an energy storage cell, with the opening preferably being congruent with the emergency opening. The perforation is preferably designed to be aligned with the emergency opening in such a way that harmful gases, particles, and the like can escape unhindered in the event of damage. With the aid of the emergency opening, the substances released from the cell can be directed to a side of the cover element facing away from the cell connector.

[0019] The opening associated with the cover element can have at least one slot. This essentially closes the cover element during normal operation, so that the energy storage cells are particularly well protected against external influences, which is particularly advantageous with regard to condensate formation. The slots can be designed in the form of a longitudinal slot, a Phillips slot, a semicircular slot, or the like.

[0020] Alternatively, it is conceivable to assign a predetermined breaking point to the opening, for example in the form of a notch or material weakening introduced into the cover element.

[0021] The cover element is preferably made of an electrically insulating and thermally conductive material. Furthermore, the cover element is preferably made of an elastic, in particular an elastomeric material. The elastic design enables the cover element to be adapted to the shape of the energy storage cells, the electrical poles, and / or the emergency openings, and it is conceivable for the cover element to seal at least the lid area of ​​the energy storage cells. The cover element is preferably made of a thermally stable elastomer. Silicone materials and fluorinated silicone materials are particularly conceivable in this context. Silicone-based elastomers are particularly preferred because they do not form electrically conductive structures even upon thermal degradation. The use of fluororubbers or materials based on EPDM or EVA is also conceivable.

[0022] The dielectric strength of the cover element is at least 2 kV / mm. Furthermore, the cover element is preferably flame-resistant. The cover element can be provided with endothermic fillers and have fiber reinforcement.

[0023] The cover element can be thermally conductive. Improved thermal conductivity can be achieved, for example, by adding hydroxides, oxides, or nitrides. Due to the improved thermal conductivity, heat can be distributed across the entire cover element in the event of a fault, thereby reducing local thermal stress in the area of ​​the opening. Furthermore, a thermally conductive design can contribute to improved heat dissipation during normal operation and transfer heat from the cell connectors to the cover element. The thermal conductivity of the cover element material is preferably at least 0.5 W / (m×K).

[0024] The cover element can be integrally bonded to the energy storage cells. It is conceivable that the cover element is connected to the energy storage cells via an adhesive bond. Alternatively, it is also conceivable that the cover element is molded directly onto the energy storage cells. This is particularly feasible when using adhesive elastomer materials.

[0025] It is also conceivable for the cover element to form a single unit with the cell connectors. The cell connectors can be embedded in the cover element, or the cover element can be molded directly onto the cell connectors. In both cases, the shape of the cover element can ensure that adjacent cell connectors are electrically insulated from one another and that the electrical insulation is maintained even in the event of a fault. It is also conceivable for the cell connectors to have already been overmolded with the cover element.

[0026] At least one heat sink can be assigned to the cover element. Particularly if the cover element is thermally conductive, it is possible to cool the energy storage cells via the poles. This allows the anodes and cathodes within the cell housing to be cooled particularly effectively when the poles are cooled. Placing the cooling elements above the cells is advantageous because energy storage cells are particularly easily accessible via the cover area. A particularly good cooling effect is achieved when a heat sink is assigned to the cell connectors. Electrical contact is made between the poles via the cell connectors, with the poles being electrically connected to the electrode unit. These components are usually also very thermally conductive, so that cooling assigned to the electrical poles is particularly effective. Until now, the problem has been that cooling can accelerate condensation formation.However, the cover element located between the heat sink and the electrical terminals prevents condensation from forming directly on the electrical terminals. Condensation on the cover element, however, is unproblematic.

[0027] Some embodiments of the energy storage arrangement according to the invention are explained in more detail below with reference to the figures. The figures show, schematically:

[0028] Fig. 1 shows an energy storage arrangement in an exploded view;

[0029] Fig. 2 shows in detail a first embodiment of a cover element;

[0030] Fig. 3 shows a second embodiment of a cover element;

[0031] Fig. 4 shows a third embodiment of a cover element;

[0032] Fig. 5 shows a fourth embodiment of the cover element; Fig. 6 shows a unit consisting of the cover element and cell connector in an exploded view;

[0033] Fig. 7 a cover element with associated heat sinks;

[0034] Fig. 8 a cover element with an associated blow-off channel.

[0035] The figures show an energy storage arrangement 1 comprising a plurality of energy storage cells 2 in the form of prismatic cells. The energy storage cells 2 each have a housing 9, which is closed by a cover 11. The two electrical poles 3 of a cell are assigned to the cover 11, with the poles 3 being assigned to the narrow sides of the housing 9. An emergency opening 4 is formed in the cover 11 between the two poles 3. The emergency opening 4 comprises an opening formed in the cover 11, which is closed by a rupture disk.

[0036] Adjacent energy storage cells 2 are electrically connected to one another by a cell connector 7 such that the energy storage cells 2 arranged in the energy storage arrangement 1 are connected in series. The cell connectors 7 are made of electrically conductive metallic material and are manufactured as a stamped part from a flat element. Copper and aluminum are particularly suitable materials in this case. A cell connector 7 covers two poles 3 and connects one pole of an energy storage cell 2 to an oppositely charged pole of a neighboring energy storage cell 2. Accordingly, it is necessary to electrically insulate neighboring cell connectors 7 from one another. During normal operation, this can be ensured by spatial spacing. However, if conductive substances or even water penetrate into the space between neighboring cell connectors 7, leakage currents or even short circuits can occur.Further insulation is provided in this case by a cover element 5. The cover element is made of an elastomeric material, in this case a silicone material. The cover element 5 is electrically insulating and thermally conductive. The cover element 5 covers the electrical poles 3 of the energy storage cells 2. In the areas of the cover element 5 assigned to the emergency openings 4, an opening 6 is made in the cover element 5 so that, in the event of damage, material flowing out of the emergency openings 4 can escape through the opening 6. The material then reaches the side of the cover element 5 facing away from the cell connectors 7 and is thus spatially separated from the cell connectors 7.

[0037] In the present embodiment, the cover element 5 seals the energy storage cells 2 in the area of ​​the lids 11 in such a way that it is moisture- and watertight, so that any condensation cannot lead to moisture deposition in the area of ​​the electrical poles 3. Furthermore, the cover element 5 also seals the space between the energy storage cells 2, so that no released material can enter the space.

[0038] Figure 2 shows a cover element 5 in detail. The cover element 5 has a plurality of openings 6 in its central region, which are assigned to the emergency openings 4 of the energy storage cells 2. In the edge regions, the cover element 5 has elevations 10, wherein the elevations 10 are designed to receive the cell connectors 7. Each cell connector 7 is assigned an elevation 10, so that adjacent cell connectors are electrically insulated from one another by the walls of the adjacent elevations 10.

[0039] Figure 3 shows an alternative embodiment of the cover element 5 described in Figure 2. In the present embodiment, channel-shaped elevations 10 are formed on the two edges of the cover element 5, wherein each elevation 10 accommodates the cell connectors 7 arranged on one side of the housing 9. This embodiment enables a particularly flexible arrangement of the cover element 5. Furthermore, the cell connectors 7 arranged below the cover element 5 can have a different shape and extension. Such a design of the cover element 5 can be extruded as a profile, which is advantageous in arrangements with a particularly large number of energy storage cells 2. Figure 4 shows an alternative embodiment of the cover element 5 described in Figure 2. In the present embodiment, the openings 6 have slots arranged in a cross shape.In the event of damage, harmful gases escape from the emergency openings 4 and can escape through the slots from the opening 6. The opening 6 can open along the slots, enlarging the passage opening. During the intended use of the energy storage arrangement 1, the openings 6 in the present embodiment are essentially closed by the opposing walls of the slots coming into contact with one another. This embodiment ensures that if material is released from an opening 6, the openings 6 of intact, adjacent energy storage cells 2 are protected.

[0040] Figure 5 shows a further development of the cover element 5 shown in Figure 4. In the present embodiment, channel-shaped elevations 10 are formed on the two edges of the cover element 5, with each elevation 10 accommodating the cell connectors 7 arranged on one side of the housing 9. This embodiment enables a particularly flexible arrangement of the cover element 5. Furthermore, the cell connectors 7 arranged beneath the cover element 5 can have a different shape and extension. This embodiment ensures that if material is released from an opening 6, the openings 6 of intact, adjacent energy storage cells 2 are protected.

[0041] Figure 6 shows an embodiment in which the cover element 5 and the cell connectors 7 form an assembleable unit. The cover element 5 is molded directly onto the cell connectors 7, so that the cell connectors 7 are connected to the cover element 5 in a materially or positively locking manner. For clarity, the cell connectors 7 and the cover element 5 are shown separately in an exploded view. The cell connectors 7 can be overmolded with the material forming the cover element 5 in an injection mold before assembly. It is also conceivable for the cell connectors 7 to be embedded in the elastic structure of the cover element 4. Figure 7 shows an embodiment in which heat sinks 8 are assigned to the cover element 5.In the present embodiment, two heat sinks 8 are provided, one heat sink each assigned to the edge region of the cover element 5, wherein the heat sinks 8 are each thermally connected to the cell connectors 7 and the electrical poles 3. This enables particularly effective cooling of the cell connectors 7, the electrical poles 3, and thus of the energy storage cells 2. An elastomeric design of the cover element 5 ensures gap-free contact with both the heat sink 8 and the cell connector 7. A cooling medium can flow through the heat sinks 8. The heat sinks 8 are preferably assigned to cover elements 5, but can also be integrated into cover elements 5. A design as an overmolded tube for coolant or as a heat sink 8 with an integrated cavity for the coolant to flow through is conceivable.The material of the cover element 5 has a thermal conductivity coefficient of at least 0.5 W / (mxK), preferably of at least 1.0 W / (mxK).

[0042] Figure 8 shows a configuration in which a blow-off channel 9 is assigned to the cover element 5. In the event of damage, material released through the emergency openings 4 enters the blow-off channel 9 and can be removed from the module. The blow-off channel 9 is sealed to the cover element 5. In this case, this is achieved by sealing longitudinal ribs. Alternatively, this can be achieved by compression. Because the cover element 5 is arranged between the blow-off channel 9 and the cell connectors 7, the blow-off channel 9 can also be made of a metallic material.

[0043] Figure 9 shows an alternative embodiment of the blow-off channel 9. The blow-off channel 9 contains a pressing element 11, here a spring or alternatively a deformable longitudinal profile, which presses the blow-off channel 9 against the cover element 5.

Claims

Patent claims 1. Energy storage arrangement (1) comprising a plurality of energy storage cells (2), each having electrical poles (3) and at least one emergency opening (4), characterized in that at least one cover element (5) is arranged on the energy storage cells (2), which cover element covers the electrical poles (3) and has openings (6) associated with the emergency openings (4).

2. Energy storage arrangement according to claim 1, characterized in that adjacent energy storage cells (2) are electrically conductively connected to one another via at least one cell connector (7) and that the cover element (5) covers the cell connectors (7).

3. Energy storage arrangement according to claim 1 or 2, characterized in that the openings (6) are designed as perforations and congruent to the emergency openings (4).

4. Energy storage arrangement according to one of claims 1 to 3, characterized in that the openings (6) each have at least one slot.

5. Energy storage arrangement according to one of claims 1 to 4, characterized in that the cover element (5) is made of electrically insulating material.

6. Energy storage arrangement according to one of claims 1 to 5, characterized in that the cover element (5) is made of thermally conductive material.

7. Energy storage arrangement according to one of claims 1 to 6, characterized in that the cover element (5) is made of polymeric material.

8. Energy storage arrangement according to one of claims 1 to 7, characterized in that the cover element (5) is made of an elastomeric material.

9. Energy storage arrangement according to one of claims 1 to 8, characterized in that the cover element (5) is formed from a silicone elastomer.

10. Energy storage arrangement according to one of claims 1 to 9, characterized in that the cover element (5) is designed as an injection-molded part or as an extruded part 11. Energy storage arrangement according to one of claims 1 to 10, characterized in that the cover element (5) is connected to the energy storage cells (2) in a materially bonded and / or form-fitting manner.

12. Energy storage arrangement according to one of claims 2 to 11, characterized in that the cover element (5) forms a unit with the cell connectors (7).

13. Energy storage arrangement according to one of claims 1 to 12, characterized in that at least one heat sink (8) is assigned to the cover element (5).

14. Energy storage arrangement according to claim 13, characterized in that the heat sink (8) is in thermal contact with the cell connectors (7) via the cover element (5).

15. Energy storage arrangement according to claim 13 or 14, characterized in that a heat sink (8) is assigned to the cell connectors (7), wherein the cell connectors (7) and the heat sinks (8) are separated by the cover element (5).

16. Energy storage arrangement according to one of claims 1 to 15, characterized in that the cover element (5) is assigned a blow-off channel (9) which can transport away material released in the event of damage, wherein the blow-off channel (9) is sealed by the cover element (5).

17. Energy storage arrangement according to one of claims 1 to 15, characterized in that the cover element (5) is assigned a blow-off channel (9) which is pressed onto the cover element (5) by a pressing element.

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