Battery module and method for cooling battery cells

Abstract

Battery module (1; 1') comprising a housing (2), battery cells (3) located in the housing (2), at least one cooling device (4), at least one inlet opening (5) for introducing a liquid cooling fluid (6) and an outlet opening (7) for discharging the cooling fluid (6), wherein the cooling fluid (6) is an electrical insulator, characterized in that the battery cells (3) are arranged in layers and that the cooling fluid (6) can flow through the housing (2) between the layers formed by the battery cells (3) in the countercurrent direction and further electrical contacts of the battery cells (3) are in contact with the cooling fluid (6).

Description

State of the art

[0001] It is foreseeable that new battery systems or battery modules, for example with lithium-ion batteries, will increasingly be used as rechargeable electrical energy storage systems (EES, electro-chemical storage system, ESS) in both stationary applications, for example in wind turbines, and mobile applications, for example in electric vehicles (EVs), hybrid vehicles (HEVs) or plug-in hybrid electric vehicles (PHEVs).

[0002] A battery system comprises a plurality of battery cells, such as cylindrical or prismatic battery cells, or battery cells with electrode windings (battery cell windings, cell windings, Jerry Roll, JR). The battery cells can be connected in series to increase the electrical voltage and / or in parallel to increase the maximum electrical current and capacity. Thus, the battery cells can be combined into battery modules or battery units. When used to power vehicles, for example, approximately 100 battery cells (as a traction battery) can be connected in series or parallel.

[0003] During operation, the battery cells can heat up, which can lead to adverse effects or malfunctions in operation if there are significant temperature changes. Therefore, cooling is necessary.

[0004] In the prior art, the battery cells arranged in a housing are cooled using circulating air as a coolant. The battery cells form a channel structure through which the coolant flows.

[0005] WO 2009 / 106 393 A1 discloses a device and a method for cooling a battery module in which air flows through the battery module as a coolant.

[0006] However, the prior art devices have the disadvantage that the batteries must be electrically isolated from each other, which leads to increased costs.

[0007] In order to increase the economic viability of battery modules and simplify their production, it is necessary to provide improved battery modules that are safer and also more cost-effective to produce.

[0008] Furthermore, the prior art includes the publications DE 10 2013 218 489 A1, US 2013 / 0 209 838 A1, WO 2014 / 045 628 A1, JP 2001- 60 466 A, and US 2013 / 0 071 701 A1. In particular, a battery module according to the preamble of independent claim 1 is known from these documents. Disclosure of the invention

[0009] The devices and methods according to the invention with the features of the independent claims have the advantage that, due to the electrically insulating properties of the cooling fluid, no electrical insulation of the battery cells from one another is required. Likewise, electrical insulation of the battery cells from the cooling fluid is not required.

[0010] The battery cells in the battery module form a channel structure through which the cooling fluid can flow. The electrical contacts of the battery cells are in contact with the cooling fluid. The batteries, which are preferably round, are arranged in such a way that they form a long channel resulting from the external geometry of the battery cells and their arrangement within the battery module. These channels support the optimal flow of the cooling fluid and are formed by the external shape of the battery cells. The battery cells themselves are arranged within a grid that secures the battery cells at both ends.

[0011] During operation of the battery module, the cooling fluid flows through the channels. The cooling fluid flows through the channels and reaches the battery cells, where the electrical connection points of the battery cells may be in direct contact with the cooling fluid.

[0012] Advantageous embodiments of the present invention are described in the dependent claims.

[0013] In a preferred embodiment, the cooling fluid has a dielectric strength of 50 to 300 kV / mm. A dielectric strength of this magnitude ensures that the battery cells in the battery module are sufficiently electrically insulated from one another.

[0014] The battery module advantageously has an external device for cooling the cooling fluid. This has the advantage that cooling can be increased or decreased as needed. This enables operation of the battery module that is largely independent of external conditions, such as the room temperature.

[0015] Conveniently, the cooling device enclosed by the battery module is a cooling fin. Due to its relatively large surface area, a cooling fin provides very efficient heat dissipation.

[0016] According to the invention, the cooling fluid flows through the battery module housing in a countercurrent direction. The battery cells are arranged within the battery module housing in such a way that the cooling fluid flows through each layer in a countercurrent direction. This ensures that the fresh, i.e., cool, cooling fluid reaches as many battery cells as possible, and that the heated cooling fluid exits the housing through the outlet valve as quickly as possible without transferring its heat to other battery cells.

[0017] The battery cells of the battery module are advantageously connected in series or parallel. If more than one layer of battery cells is arranged above another in the battery module, the flow direction of the cooling fluid in one layer is opposite to the flow direction of the cooling fluid in the layer above.

[0018] The cooling fluid preferably contains at least 99.5% methoxy-nonafluorobutane and a maximum of 1.0 ppm of non-volatile residues. One such cooling fluid is 3M Novec 7100DL Engineered Fluid. This has a molecular weight of 250, a boiling point of 61 °C, and a freezing point of -135 °C. The liquid density is 1.52 g / ml, and the surface tension is 13.6 dynes / cm. The solubility in water is 12 ppmw, and the solubility of water in this coolant is 95 ppmw. The vapor pressure is 200 mmHg. Unless otherwise stated, all values refer to a temperature of 25 °C.

[0019] The cooling fluid is expediently cooled by an external cooling device.

[0020] It is advisable for the cooling fluid to be cooled by an external device before being introduced into the housing.

[0021] Advantageously, the cooling fluid contains at least 99.5% methoxy-nonafluorobutane and at most 1.0 ppm non-volatile residues.

[0022] Further features and advantages of the present invention will become apparent to those skilled in the art from the following description of exemplary embodiments, which, however, are not to be construed as limiting the invention, with reference to the accompanying drawings.

[0023] Fig. 1 shows a battery module 1 comprising a housing 2. The housing comprises a plurality of battery cells 3. Furthermore, the battery module has at least one inlet opening or an inlet valve 5 for introducing a liquid cooling fluid 6 and an outlet opening or an outlet valve 7 for discharging the cooling fluid 6. Furthermore, the battery module comprises a cooling device 4, for example a heat exchanger and / or a circulation device 10, for example a pump. Fig. 1, the cooling fluid flows into the battery module via the inlet valve 5 and then flows in countercurrent through the channels formed by the individual battery cells. The device also includes an external device 8 for cooling the cooling fluid 6.

[0024] Fig. 2 shows another battery module 1'. As with Fig.1, a liquid cooling fluid flows from the cooling fluid cooling device 8 through an inlet valve 5 into the battery module 1' and exits the battery module 1' through the outlet valve 7. The battery cells 3 are arranged in layers, with the cooling fluid flowing countercurrently between the layers formed by the battery cells. The battery module 1' additionally has a degassing valve 9. If, in the event of a malfunction, a temperature rise occurs in a battery cell 3 and the cooling fluid begins to evaporate upon reaching its boiling point, the resulting pressure increase is compensated via the degassing valve 9.

[0025] Finally, it should be noted that expressions such as “comprising” and “having” or the like do not exclude the possibility of further elements or steps being provided. The numbers used are merely exemplary, so that a plurality may include two, four, five, six, or more elements or steps. It should also be noted that articles such as “a” or “an” do not exclude a plurality. It should also be noted that numerals or ordinal numbers such as “first,” “second,” etc. serve solely to distinguish elements and steps, without establishing or restricting an order in which the elements are arranged or the steps are carried out. Furthermore, the features described in connection with the various embodiments can be combined with one another in any desired manner. Finally, it should be noted that the reference signs in the claims should not be interpreted as limiting the scope of the claims.

Claims

[1] Battery module (1; 1') comprising a housing (2), battery cells (3) located in the housing (2), at least one cooling device (4), at least one inlet opening (5) for introducing a liquid cooling fluid (6) and an outlet opening (7) for discharging the cooling fluid (6), wherein the cooling fluid (6) is an electrical insulator, characterized by that the battery cells (3) are arranged in layers and that the cooling fluid (6) can flow through the housing (2) between the layers formed by the battery cells (3) in countercurrent direction and further electrical contacts of the battery cells (3) are in contact with the cooling fluid (6). [2] Battery module (1; 1') according to claim 1, wherein: - the cooling fluid (6) has a dielectric strength of 50 - 300 kV / mm. [3] Battery module (1; 1') according to claim 1 or 2, wherein: - the battery module (1; 1') has an external device (8) for cooling the cooling fluid (6). [4] Battery module (1; 1') according to one of the preceding claims, wherein: - the cooling device (4) is a cooling fin. [5] Battery module (1; 1') according to one of the preceding claims, wherein: - the battery cells (3) are connected in series or parallel. [6] Battery module (1; 1') according to one of the preceding claims, wherein: - the cooling fluid contains at least 99.5% methoxy-nonafluorobutane and at most 1.0 ppm non-volatile residues. [7] Method for cooling battery cells (3) arranged in a housing (2), comprising: - Introducing a liquid cooling fluid (6) into the housing (2), - Cooling the battery cells (3) with the cooling fluid (6), - discharging the cooling fluid (6) from the housing, wherein the cooling fluid is an electrical insulator, characterized by , that the battery cells (3) are arranged in layers and that the cooling fluid (6) flows through the housing (2) between the layers formed by the battery cells (3) in countercurrent direction, and further electrical contacts of the battery cells (3) are in contact with the cooling fluid (6). [8] The method of claim 7, wherein: - the cooling fluid (6) is cooled by an external cooling device (8). [9] A method according to claim 7 or 8, wherein: - the cooling fluid (6) is cooled by an external device (8) before being introduced into the housing (2). [10] A method according to any one of claims 7 to 9, wherein: - the cooling fluid contains at least 99.5% methoxy-nonafluorobutane and at most 1.0 ppm non-volatile residues.

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