WO2024095291A1

WO2024095291A1 - Fire-resistant battery modules

Info

Publication number: WO2024095291A1
Application number: PCT/IN2023/051012
Authority: WO
Inventors: Bharathraj Jayaraman; Samraj J Dhinagar; Ayush Srivastav
Original assignee: Ola Electric Mobility Limited
Priority date: 2022-11-03
Filing date: 2023-11-03
Publication date: 2024-05-10

Abstract

Present invention relates to a method for manufacturing fire-resistant battery modules (100) The method comprises press moulding, along periphery of a fixture resembling a battery module (100) in shape, a fire- retardant material, to obtain a mold (104) of the fire-retardant material, the battery module (100) having a plurality of cells (102). The method further comprises positioning the mold (104) inside a casing (106) for the battery module (100) and assembling the battery module (100) in the casing (106) such that the mold (104) is positioned around the battery module (100) to form an outer boundary along the periphery of the plurality of cells (102) of the battery module (100). Further, the method comprises covering a top of the plurality of cells of the battery module with a sheet of fire-retardant material and inserting fire-retardant material by a robotic nozzle into gaps (202) between the plurality of cells (102) of the battery module (100).

Description

FIRE-RESISTANT BATTERY MODULES

TECHNICAL FIELD

[0001 ] The present subject matter relates, in general, to battery modules and, particularly, to fire-resistant battery modules for electric vehicles.

BACKGROUND

[0002] Electric vehicles use one or more battery packs as a source of power. A battery pack that powers electric vehicles consist of individual battery cells and modules organized in series and parallel. A cell is the smallest unit of a battery pack, comprised of components, such as a cathode, anode, electrolyte, and separator. The characteristics of a battery cell play a pivotal role in overall performance of the electric vehicles. A module consists of multiple cells connected in series and/or parallel, encased in a mechanical structure. A battery pack is assembled by connecting multiple modules together in series or parallel with sensors and controllers including battery management systems and thermal management systems and then encased in a casing as a final battery system designed specifically for each vehicle model.

[0003] The process of charging and discharging the battery modules is normally accompanied by a small amount of heat. In ideal conditions, the heat dissipates from the cell. However, in thermal runaway, the cells may generate heat at a rate several times higher than the rate at which heat dissipates from the cells. The sequential occurrence of thermal runaway within a battery system triggered by the thermal runaway of a cell in a battery system is known as thermal propagation.

[0004] A recent government regulation AIS (AUTOMOTIVE INDUSTRY STANDARD) 156 (Amendment 2) mandates that the REESS (Rechargeable Electrical Energy Storage System) should withstand thermal propagation which is triggered by an internal short circuit leading to a single cell thermal runaway and subsequent thermal propagation and shall not result in fire and explosion. [0005] Therefore, it is desirable to provide fire-resistant battery modules for electric vehicles which are able to withstand thermal propagation during the thermal runaway of a cell inside a battery module.

BRIEF DESCRIPTION OF DRAWINGS

[0006] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0007] Figure 1 illustrates a plan view of a fire-resistant battery module, in accordance with an implementation of the present subject matter.

[0008] Figure 2 illustrates a plan view of the fire-resistant battery module, in accordance with another implementation of the present subject matter.

DETAILED DESCRIPTION

[0009] The present subject matter relates to a method and system for manufacturing a fire-resistant battery modules.

[0010] In an event of a thermal runaway, a battery cell, such as a lithium- ion cell generates heat at a rate several times higher than the rate at which heat dissipates from the battery cell. The thermal runaway of the battery cell may cause thermal propagation in a battery module in which the battery cell is located due to the continuous thermal runaway of the remaining cells within the battery module. The thermal propagation caused due to the continuous thermal runaway within the battery module may further lead to fire and explosion in the battery module.

[0011] In some conventional and existing techniques for manufacturing the fire-resistant battery modules, fire-retardant materials, such as wool paper and blankets are used for prevention of the thermal propagation within the battery module. Production of fire-resistant battery modules using the fire-retardant wool paper and blankets requires tedious labor for manually cutting and placing the fire-retardant wool paper and blankets inside small and hard-to-reach gaps of the battery modules. Moreover, manufacturing fire-resistant battery modules using the fire-retardant materials, such as wool paper and blankets increases the takt time due to the involvement of manual labor. Also, the cost of the battery modules increases owing to significant manual labor involved in the manufacturing process.

[0012] Thus, the existing methods for manufacturing the fire-resistant battery modules are complex, expensive, time consuming as well as error- prone due to the involvement of labor-intensive and cumbersome processes.

[0013] The present subject matter related to a method for manufacturing fire-resistant battery modules. As mentioned above, the battery module has a plurality of cells. The method comprises press moulding a fire-retardant material, along periphery of a fixture resembling a battery module in shape, to obtain a mold of the fire-retardant material. The method further comprises positioning the mold inside a casing for the battery module and assembling the battery module in the casing such that the mold is positioned around the battery module to form an outer boundary along the periphery of the plurality of cells of the battery module.

[0014] In accordance with embodiments of the present subject matter, press molding the fire-retardant material is achieved using a mechanical press. Conventionally available techniques do not consider use of a mechanical press in the battery assembling process given that a battery module is generally not suitable to be subjected to a mechanical press. To overcome this limitation, i.e., to enable use of the mechanical press in the battery assembling process, the present subject matter involves the use of a fixture. A fixture may be understood as a three-dimensional structure that has an identical shape as a battery module which is to be made fire- resistant. Since the fixture resembles the battery module dimensionally, press molding of the fire-retardant material around the fixture allows the molded fire-retardant material to acquire a shape of the battery module. Thus, the mechanically prepared mold is obtained and the manual process of packaging fire-retardant material around a battery module to make it fire- resistant is eliminated. This results in cost and time reduction in the manufacturing of the fire-resistant battery modules as the disclosed method of manufacturing the fire-resistant battery modules eliminate manual intervention. Further, the disclosed method of manufacturing the fire- resistant battery modules is less complex.

[0015] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0016] Figure 1 and figure 2 illustrate a plan view of a fire-resistant battery module in accordance with one embodiment of the present subject matter.

[0017] While Figure 1 and Figure 2 depict a specific shape of the fire- resistant battery module, it will be clear to a person skilled in the art that the shape shown in figures is not a limitation. Rather, the method of manufacturing the fire-resistant battery module of the present application is applicable to any battery module irrespective of the shape of the battery module and the fire-resistant battery module as described in the present subject matter can be of any shape, such as cuboidal, cube, cylindrical, elliptical, etc.

[0018] As mentioned previously, in general, a battery pack that powers electric vehicles consist of individual battery cells and the battery modules organized in series and parallel. A battery cell is the smallest unit of the battery pack. The battery module 100 consists of a plurality of cells 102 connected in series and/or parallel, encased in a mechanical structure. The battery pack is assembled by connecting multiple battery modules together in series or parallel. For example, the plurality of cells 102 used in the battery modules is not limited to the lithium-ion cell, the battery module may use a Nickel-Cadmium cell, Nickel-metal hydride cell, dry cell, etc.

[0019] In accordance with embodiments of the present subject matter, a method for manufacturing the fire-resistant battery module 100 comprises press moulding a fire-retardant material such as a ceramic wool, along periphery of a fixture (not shown in figures) resembling the battery module 100 in shape.

[0020] In accordance with embodiments of the present subject matter, the fixture can be a completely solid structure or a hollow structure resembling the shape of the battery module 100. In accordance with embodiments of the present subject matter, the fixture having an identical shape to the battery module can be made of any material, such as plastic, metal, wood, or any metal alloy which is capable of withstanding pressure during the press moulding process in which the fire-retardant material is press molded around the fixture to acquire a shape of the battery module 100.

[0021] Depending on the material used to make the fixture, various techniques may be used to make the fixture. In an example, in case the material selected for preparing the fixture is wood, the fixture can be simply carved out from the wood in the shape and dimensions identical to the battery module 100 which is to be made fire-resistant. Similarly, in case the material to be used for preparing the fixture is a plastic, metal, or any metal alloy, the fixture can be prepared using a compression molding process, for example.

[0022] The compression molding process for preparing the fixture may include various step, such as insertion of any one of the plastic, metal, or alloys into the mold having shape and dimensions similar to the battery module 100 and application heat until the material becomes soft and pliable to mold the same. Details of conventional steps/techniques of making the fixture have been skipped for the sake of brevity of the present description. [0023] Once the fixture is ready, press molding process may be used for pressing the fire-retardant material against the mold. For example, the compression molding process may include compressing the fire-retardant material with a hydraulic tool press against the mold. Due to compression, as the fire-retardant material compresses, it takes shape of the mold which has shape and dimensions similar to the battery module.

[0024] In accordance with embodiments of the present subject matter, press moulding of the fire-retardant material along periphery of the fixture to create a mold 104 is done by application of pressure by a pressing device. The pressing device may be a hydraulic press, hydro pneumatic press, or any other device suitable for such purposes.

[0025] In accordance with embodiments of the present subject matter, the fire-retardant material is a fire-retardant ceramic, such as ceramic wool fiber, ceramic silicone rubber, etc. The fire-retardant material can be any material which is capable of withstanding high temperatures and can be press moulded in the shape of the battery module.

[0026] As apparent, press molding of the fire-retardant material along periphery of the fixture creates a mold 104 of the fire-retardant material.

[0027] The mold 104 made of the fire-retardant material is positioned inside a casing 106 for the battery module 100. The casing for the battery module 100 provides an external peripheral boundary for the battery module 100. The casing can be made of any material such as plastic, metal alloy, or any other material which can provide a rigid structure for an outer boundary of the battery module.

[0028] The battery module 100 is assembled in the casing 106 in such a manner that the mold 104 made of the fire-retardant material is positioned around the battery module 100 to form an outer boundary along the periphery of the plurality of cells 102 of the battery module 100.

[0029] In an example implementation, the battery module 100 may be then assembled in an electric vehicle.

[0030] In accordance with embodiments of the present subject matter, the method of manufacturing the fire-resistant battery modules 100 comprises covering a top of the plurality of cells 102 of the battery module 100, with a sheet of the fire-retardant material. The sheet can be made of any fire-retardant material as mentioned in the above paragraphs. The sheet may be of the same material as used for making the mold 104 or a different type of fire-retardant material.

[0031] The shape of the sheet resembles the shape of the battery module 100. For the purpose, in one example, the sheet may be cut out in the shape of the top of the battery module 100 from a sheet of the fire- retardant material. While assembling the sheet on the top of the plurality of cells 102 of the battery module 100, edge of the sheet and the periphery of the mold 104 aligns together.

[0032] Assembling the sheet of the fire-retardant material on the top of the plurality of cells 102 arranged inside the casing 106 for the battery module 100 may be done with the help of a robotic arm in an example embodiment. The robotic arm picks up the sheet of fire-retardant material and places it on the top of the battery module 100 ensuring that the sheet provides a complete top enclosure for the battery module 100. In other example embodiments, the sheet may be placed on the top manually.

[0033] In accordance with embodiments of the present subject matter, and as shown in Figure 2, a plurality of gaps 202 are formed between the plurality of cells 102 arranged inside the casing 106 of the battery module 100. As will be apparent, the plurality of cells 102 are cylindrical in shape and hence when the plurality of cells 102 are arranged inside the casing 106 of the battery module 100, gaps are formed between the adjacent cells. [0034] In an example implementation, the method of manufacturing the fire-resistant battery modules 100 further comprises inserting the fire- retardant material into gaps between the plurality of cells 102 of the battery module 100. Such an additional step serves to make the battery modules 100 further resistant to fire.

[0035] In accordance with embodiments of the present subject matter, the insertion of the fire-retardant material into gaps between the plurality of cells 102 of the battery module 100 may be carried out by a robotic nozzle configured to for the purpose.

[0036] In an example, the robotic nozzle may use a pressurized pump that blows pressurized air for inserting the fire-retardant material into the plurality of gaps 202 between the plurality of cells 102. The robotic nozzle, apart from the pressurized pump, may use any other means which fulfils the purpose of using the pressurized pump and works in conjunction with the robotic nozzle for inserting the fire-retardant material into the plurality of gaps 202.

[0037] As will be understood, the battery module 100 is assembled in the casing 106 in such a manner that the mold 104 of the fire-retardant material is positioned around the battery module 100 to form an outer boundary along the periphery of the plurality of cells 102 of the battery module 100. Further, the plurality of gaps 202 between the plurality of cells 102 of the battery module is filled with the fire-retardant material with the help of the robotic arm.

[0038] Thus, a battery module assembled based on the above- mentioned techniques is fire-resistant. Hence, in an event of thermal runaway in a cell of the battery module 100, the fire-retardant mold 104, the sheet of the fire-retardant material placed on the top of the plurality of cells 102 of the battery module 100, and the fire-retardant material filled into the gaps 202 between the plurality of cells 102 of the battery module 100, prevent thermal propagation in the battery module 100 which may otherwise result in fire or explosion in the battery module 100.

[0039] In an example implementation, fire-resistant battery modules assembled based on the above-mentioned techniques are assembled onto electric vehicles. An electric vehicle incorporating fire-resistant battery modules assembled using the herein described method is compliant with AIS (AUTOMOTIVE INDUSTRY STANDARD) 156 (Amendment 2).

[0040] In accordance with embodiments of the present subject matter, the use of the fire-resistant battery modules is not limited to electric vehicles, the fire-resistant battery modules can be used in various application that implement a battery system, in high voltage in particular. For instance, apart from their application in the electric vehicles, the fire-resistant battery modules can be also used as a power source for an electronic equipment in industrial applications, and a high-capacity power bank that offers uninterruptible power supply (UPS) capabilities.

[0041] Although the subject matter has been described in considerable detail with reference to certain examples and implementations thereof, other implementations are possible. As such, the present disclosure should not be limited to the description of the preferred examples and implementations contained therein.

Claims

I/We Claim:

1. A method for manufacturing fire-resistant battery modules (100), said method comprising: press moulding, along periphery of a fixture resembling a battery module (100) in shape, a fire-retardant material, to obtain a mold (104) of the fire-retardant material, wherein the battery module (100) has a plurality of cells (102); positioning the mold (104) inside a casing (106) for the battery module (100); and assembling the battery module (100) in the casing (106) such that the mold (104) is positioned around the battery module (100) to form an outer boundary along the periphery of the plurality of cells (102) of the battery module (100).

2. The method as claimed in claim 1 , comprises covering, with a sheet of the fire-retardant material, a top of the plurality of cells (102) of the battery module (100).

3. The method as claimed in claim 1 , comprises inserting the fire- retardant material into gaps (202) between the plurality of cells (102) of the battery module (100).

4. A system for manufacturing fire-resistant battery modules (100), said system comprising: a fixture resembling shape of a battery module (100), the battery module (100) having a plurality of cells (102) to be arranged in a casing (106); and a pressing device to create a mold (104) of a fire-retardant material by press moulding the fire-retardant material along periphery of the fixture, wherein the mold (104) forms an outer boundary along the periphery of the plurality of cells (102) to be arranged inside the casing (106) for the battery module (100).

5. The system as claimed in claim 4, comprises a robotic nozzle configured to insert the fire-retardant material in gaps (202) between the plurality of cells (102) of the battery module (100).

6. The system as claimed in claim 4, comprises a robotic arm to assemble a sheet of fire-retardant material configured to cover top of the plurality of cells (102) to be arranged inside the casing (106) for the battery module (100).

7. The system as claimed in claim 4, wherein the robotic nozzle comprises a pressurized pump configured to blow pressurized air for inserting the fire-retardant material into a plurality of gaps (202) between the plurality of cells (102).

8. The system as claimed in any one of the preceding claims 4-7, wherein the fire-retardant material is a fire-retardant ceramic.

9. The system as claimed in claim 4, wherein the pressing device is a hydraulic press.