WO2024028890A1

WO2024028890A1 - A battery module

Info

Publication number: WO2024028890A1
Application number: PCT/IN2023/050734
Authority: WO
Inventors: Vikas Agrawal; Prabhanjan Kumar; Pramila Rao NILESHWAR
Original assignee: TVS Motor Co Ltd
Current assignee: TVS Motor Co Ltd
Priority date: 2022-08-01
Filing date: 2023-07-31
Publication date: 2024-02-08
Anticipated expiration: 2025-02-01
Also published as: CO2025000984A2

Abstract

The present invention relates to a battery module (10). The battery module (10) includes a casing (20) and a plurality of cylindrical battery cells (30) which are stacked adjacent to each other inside the casing (20). Each of the plurality of cylindrical battery cells (30) has a length (L) and a diameter (D). Each of the plurality of cylindrical battery cells (30) also has a pair of terminals. The terminals of the plurality of cylindrical battery cells (30) are electrically connected to each other. The battery module (10) further includes an adhesive (40) which is adapted to occupy interstices (42) between each of the plurality of cylindrical battery cells (30) so as to physically and electrically separate the plurality of cylindrical battery cells (30) from each other. The adhesive (40) is thermally conducting and electrically insulating.

Description

TITLE OF INVENTION

A Battery Module

FIELD OF THE INVENTION

[001] The present invention generally relates to a battery module and more particularly relates to disposition of battery cells of the battery module.

BACKGROUND OF THE INVENTION

[002] A battery module includes a plurality of battery cells interconnected to each other. The battery module achieves desired voltage by connecting several battery cells in series, such that each battery cell adds its voltage potential to derive the total terminal voltage. Similarly, the battery module achieves desired current by connecting several battery cells in parallel. If higher voltages or currents are needed and larger battery cells are not available or do not fit the design constraint, one or more battery cells can be connected in series or parallel to achieve the desired electrical output. Generally, the battery module employs a combination of series and parallel connections for its plurality of battery cells. This enables for design flexibility and achieves the desired voltage and current ratings with a standard battery cell size. Conventionally, the battery cell is provided with two cell tabs or terminals, one positive and other negative to connect the battery cell to another battery cell or to an external load. The aforementioned series and/or parallel connections between individual battery cells of the battery module are achieved by electrically connecting the cell tabs or terminals of different battery cells. [003] Generally, a plurality of standard cylindrical battery cells is employed in the battery modules used in automobiles, power tools, etc. The plurality of standard cylindrical battery cells is electrically interconnected with each other in a combination of series and parallel to achieve the desired electrical output. Use of standardised battery cells brings down manufacturing cost per cell. Since battery cells having a cylindrical form factor has higher energy density than battery cells having other form factors, cylindrical battery cells are preferred in high energy applications like automobiles and power tools where space constraint is a huge challenge. Ideally the plurality of cylindrical battery cells is arranged in rows and columns within the battery module and some means is employed to isolate the plurality of cylindrical battery cells from each other. Cell to cell contact could cause short circuit in the battery module leading to fires or explosions.

[004] Conventionally, the plurality of cells is accommodated in their respective cell holders. The cell holders are made of insulating materials and electrically isolates the plurality of cylindrical battery cells from each other. However, use of cell holders compromises space within the battery module since cell to cell spacing is greater than 1 to 1.5 millimetre (mm). It is not feasible to fabricate cell holders of lesser thickness that can effectively isolate the plurality of battery cells from each other.

[005] Also, spacers are used between adjacent battery cells to achieve a compact secured fit for the battery cells within the battery module. The spacers ensure constant pressure on the sides of the individual battery cells to ensure a tight packing of the battery cells within a battery module. However, the use of spacers increases the total footprint and the overall space requirement for the battery module. This creates challenges in applications where space limitation exists. Spacers, however, do not provide structural support for the battery pack. Other methods of using gaskets or seals in the battery module to secure the battery cells within the battery module leads to complexity in manufacturing and assembly of the battery module and does not produce corresponding space saving.

[006] Furthermore, if lithium-ion cells, used in modern day battery modules, are overheated, they are prone to accelerated battery cell degradation. The battery cells can catch fire or even explode as a thermal runaway condition can occur if voltage of one or more lithium-ion cells exceeds by even a few hundred millivolts as compared to its predetermined threshold voltage or if temperature of the battery cell rises above the temperature threshold. Thus, it is imperative to provide for effective cooling of the battery cells in the battery module along with electrical isolation from adjoining battery cells. Use of cell holders separate the plurality of battery cells from each other, and pockets of air are formed between them. Air being a bad conductor of heat, heat dissipation from the battery cells is low and there exists a risk of overheating and thermal runaway of the battery module. This in turn limits the performance of the battery pack including charging times and power output.

[007] Thus, there is a need in the art for a battery module which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION

[008] In one aspect, the present invention is directed to a battery module. The battery module includes a casing and a plurality of cylindrical battery cells which are stacked adjacent to each other inside the casing. Each of the plurality of cylindrical battery cells has a length and a diameter. Each of the plurality of cylindrical battery cells also has a pair of terminals. The terminals of the plurality of cylindrical battery cells are electrically connected to each other. The battery module further includes an adhesive which is adapted to occupy interstices between each of the plurality of cylindrical battery cells so as to physically and electrically separate the plurality of cylindrical battery cells from each other. The adhesive is thermally conducting and electrically insulating.

[009] In an embodiment, the interstice between each of the plurality of cylindrical battery cells is 0.2 to 0.3 millimeters.

[010] In an embodiment, the adhesive used is epoxy. In another embodiment, the adhesive used is polyurethane.

[011] In an embodiment, the casing of the battery module includes a bottom wall and a plurality of side walls. The plurality of side walls extends upwardly from the bottom wall. In an embodiment, the adhesive occupies interstices between the plurality of cylindrical battery cells which are disposed at an extremity within the casing and the plurality of side walls of the casing.

[012] In another embodiment, the plurality of cylindrical battery cells is stacked inside the casing such that the length of each of the plurality of cylindrical battery cells is orthogonal to the bottom wall of the casing. In yet another embodiment, one terminal of the pair of terminals of each of the plurality of battery cells is located at a first end and the other terminal is located at a second end of the corresponding cylindrical battery cell. The first end of the corresponding cylindrical battery cell is disposed closer to the bottom wall.

[013] In an embodiment, the battery module includes a plurality of interconnectors which are adapted to electrically connect the corresponding terminals of the plurality of cylindrical battery cells to connect the plurality of cylindrical battery cells with each other. The corresponding terminals of the plurality of cylindrical battery cells are connected via the plurality of interconnectors to achieve series or parallel or a combination of series and parallel connection between the plurality of cylindrical battery cells of the battery module. [014] In a further embodiment, the terminals located at the first end of the plurality of cylindrical battery cells and the interconnectors for connecting them are enveloped by the adhesive. In another embodiment, the terminals located at the second end of the plurality of cylindrical battery cells and the interconnectors for connecting them are exposed outside the adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

[015] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

Figure 1 illustrates a perspective view of an exemplary battery module, in accordance with an embodiment of the present invention.

Figure 2 illustrates an exploded view of the battery module, in accordance with an embodiment of the present invention.

Figure 3 illustrates a cross sectional view of the battery module, in accordance with an embodiment of the present invention.

Figure 4 illustrates another cross sectional view of the battery module, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[016] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. [017] The present invention generally relates to a battery module and more particularly relates to disposition of battery cells of the battery module. In the ensuing exemplary embodiments, the battery cell is a cylindrical battery cell. However, it is contemplated that the disclosure in the present invention may be applied to a battery cell of any form factor capable of accommodating the present subject matter without defeating the scope of the present invention.

[018] Figure 1 illustrates a perspective view of an exemplary battery module 10, in accordance with an embodiment of the present subject matter. The battery module 10 includes a casing 20 which forms an outer protective structure of the battery module 10. The casing 20 includes a bottom wall 22 (shown in Figure 3) and a plurality of side walls 24. The plurality of side walls 24 extends upwardly from the bottom wall 22. In the illustrated embodiment, the casing 20 has a cuboidal shape and the four side walls 24 are perpendicular to the bottom wall 22. However, the casing 20 can be of any shape based on design requirements of the battery module 10. The battery module 10 further includes a plurality of cylindrical battery cells 30 which are stacked adjacent to each other inside the casing 20. Each of the plurality of cylindrical battery cells 30 include a pair of terminals. Among the pair of terminals one terminal is negative and the other is positive. The terminals of the plurality of cylindrical battery cells 30 are electrically connected to each other.

[019] Figure 2 illustrates an exploded view of the battery module 10, in accordance with an embodiment of the present subject matter. Each of the plurality of cylindrical battery cells 30 include a first end 32 and a second end 34. The first end 32 and second end 34 are situate opposite each other. The first end 32 is disposed closer to the bottom wall 22, and the second end 34 is disposed further away from the bottom wall 32. In the illustrated embodiment, one terminal of the pair of terminals of each cylindrical battery cell 30 is located at the first end 32 and the other terminal is located at the second end 34. In an embodiment, the battery module 10 includes a plurality of interconnectors 52. The plurality of interconnectors 52 are adapted to electrically connect the corresponding terminals of the plurality of cylindrical battery cells 30 to connect the plurality of cylindrical battery cells 30 with each other in series or in parallel or in a combination of series and parallel. In the illustrated embodiment, a single row of cylindrical battery cells 30 is portrayed and the plurality of interconnectors 52 connect the single row of cylindrical battery cells 30 in series. One interconnector 52 connects all the corresponding positive terminals and the other interconnector 52 connects all the corresponding negative terminals of the single row of cylindrical battery cells 30.

[020] Figure 3 illustrates a cross sectional view of the battery module 10, in accordance with an embodiment of the present subject matter. In the embodiment illustrated in Figure 3, the plurality of cylindrical battery cells 30 are connected to each other in series. Figure 4 illustrates a cross sectional view of the battery module 10, in accordance with another embodiment of the present subject matter. In the embodiment illustrated in Figure 4, the plurality of cylindrical battery cells 30 are connected to each other in parallel. Referring to Figures 2, 3 and 4, each of the plurality of cylindrical battery cells 30 have a length L and a diameter D. In the illustrated embodiment, the plurality of cylindrical battery cells 30 is stacked inside the casing 20 such that the length L of each of the plurality of cylindrical battery cells 30 is substantially orthogonal to the bottom wall 22, i.e., the plurality of cylindrical battery cells 30 is disposed to be erect with respect to the bottom wall 22. In an embodiment, each of the plurality of cylindrical battery cells 30 rest on the bottom wall 22 by its first end 32.

[021 ] The battery module 10 includes an adhesive 40 which is adapted to occupy interstices

42 between each of the plurality of cylindrical battery cells 30. By occupying interstices 42 between the plurality of cylindrical battery cells 30, the adhesive 40 physically and electrically separates the plurality of cylindrical battery cells 30 from each other. Further, the adhesive 40 secures the plurality of cylindrical battery cells 30 within the casing 20. This ensures that the plurality of cylindrical battery cells 30 stay in a state of rest with respect to each other and the casing 20, thereby reducing chances of lose contact or shorting due to dislocation of any of the plurality of interconnectors 52 from the corresponding terminals under external accelerations or forces. The adhesive 40 is also thermally conducting and electrically insulating in nature. While aiding in electrically isolating the plurality of cylindrical battery cells 30 from each other, the adhesive 40 also improves the thermal performance of the battery module 10 by effectively dissipating heat developed in the plurality of cylindrical battery cells 30 to the casing 20 and then to an environment outside the battery module 10. In an embodiment, the interstice 42 between each of the plurality of cylindrical battery cells 30 is 0.2 to 0.3 millimeters (mm). The adhesive 40 is effective enough to electrically insulate the said interstice 42. In another embodiment, the adhesive 40 occupies interstices 42 between the plurality of cylindrical battery cells 30 disposed at an extremity and the plurality of side walls 24 of the casing 20. This ensures that the plurality of cylindrical battery cells 30 are electrically insulated from the walls of the casing 20 and do not pose a safety risk to persons touching the casing 20. It also keeps the battery module 10 shock resistant as the adhesive 40 will absorb impacts on the casing 20 and shield the plurality of cylindrical battery cells 30 from impact forces.

[022] In an exemplary embodiment, the plurality of cylindrical battery cells 30 are placed inside the casing 20 maintaining the required gap or interstice 42 between each other and the casing 20. The adhesive 40 in liquid form is poured to seal the first end 32 of the plurality of cylindrical battery cells 30 along with the bottom wall 22 and the interconnector 52 disposed thereon. The plurality of cylindrical battery cells 30 are externally supported to prevent them from dislocation during the process of pouring the adhesive 40. The external support is removed after the adhesive 40 sets and secured the plurality of cylindrical battery cells 30 in position. Then, interconnectors 52 are welded to connect the terminals of the plurality of cylindrical battery cells 30 at their respective second ends 34. In a further embodiment, the terminals located at the first end 32 of the plurality of cylindrical battery cells 30 and the interconnectors 52 for connecting them are enveloped by the adhesive 40. The terminals located at the second end 34 of the plurality of cylindrical battery cells 30 and the interconnectors 52 for connecting them are exposed outside the adhesive 40. In yet another embodiment, the plurality of cylindrical battery cells 30 employ single side welding. In an embodiment, the adhesive 40 used is a fast-curing resin which immediately solidifies and becomes rigid around the plurality of cylindrical battery cells 30 after its application or pouring. In an embodiment, the adhesive 40 is epoxy along with other combinations. In another embodiment, the adhesive 40 is polyurethane.

[023] Advantageously, the present claimed invention provides a battery module and disposition of a plurality of battery cells in the battery module while achieving a reduction in gaps or interstices between the plurality of battery cells. The claimed configurations of the battery module as discussed above are not routine, conventional, or well understood in the art, as the claimed configurations of the battery module enable the following solutions to the existing problems in conventional technologies. Specifically, the present invention achieves a reduction in battery cell to battery cell spacing within the battery module thereby leading to an increase in volumetric energy density. Thus, a greater number of battery cells can be accommodated within a given space. This is beneficial in applications requiring battery power but is limited by space available for battery storage like electric automobiles, power tools, etc. Since an adhesive is used to separate the plurality of battery cells from each other there are benefits like part reduction and weight reduction. Parts to hold the plurality of battery cells like cell holders can be eliminated thereby decreasing weight and cost of the battery module. Further, since the adhesive tightly packs the battery cells and secures them within the battery module there is no requirement for extra parts like spacers to insulate and tightly pack the cells. The electrically insulating adhesive can effectively prevent short circuits by keeping each of the plurality of battery cells, their terminals and the plurality of interconnectors connecting them electrically isolated. The thermally conducting adhesive allows for effective heat dissipation thereby enhancing safety of the battery module and increasing its operational efficiency. Good heat dissipation also increases longevity of the battery cells. The adhesive also is quick setting and allows for an easier assembly process. Further, the adhesive present between the plurality of battery cells and walls of the casing of the battery module helps in dampening external shocks and vibrations that may reach the battery cells through the casing.

[024] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS:

1 . A battery module (10) comprising: a casing (20); a plurality of cylindrical battery cells (30) stacked adjacent to each other inside the casing (20), each of the plurality of cylindrical battery cells (30) having: a length (L) and a diameter (D); and a pair of terminals, the terminals of the plurality of cylindrical battery cells (30) being electrically connected to each other; and an adhesive (40) configured to occupy interstices (42) between each of the plurality of cylindrical battery cells (30) so as to physically and electrically separate the plurality of cylindrical battery cells (30) from each other, the adhesive (40) being thermally conducting and electrically insulating.

2. The battery module (10) as claimed in claim 1 , wherein the interstice (42) between each of the plurality of cylindrical battery cells (30) being 0.2 to 0.3 millimeters.

3. The battery module (10) as claimed in claim 1 , wherein the adhesive (40) comprises epoxy.

4. The battery module (10) as claimed in claim 1 , wherein the adhesive (40) comprises polyurethane.

5. The battery module (10) as claimed in claim 1 , wherein the casing (20) comprises a bottom wall (22) and a plurality of side walls (24) extending upwardly from the bottom wall (22). The battery module (10) as claimed in claim 5, wherein the adhesive (40) occupies interstices (42) between the plurality of cylindrical battery cells (30) disposed at an extremity and the plurality of side walls (24) of the casing (20). The battery module (10) as claimed in claim 5, wherein the plurality of cylindrical battery cells (30) is stacked inside the casing (20) to have the length (L) of each of the plurality of cylindrical battery cells (30) orthogonal to the bottom wall (22). The battery module (10) as claimed in claim 7, wherein one terminal of the pair of terminals is located at a first end (32) and the other terminal is located at a second end (34) of the corresponding cylindrical battery cell (30), the first end (32) disposed closer to the bottom wall (22). The battery module (10) as claimed in claim 1 comprising a plurality of interconnectors (52) configured to electrically connect the corresponding terminals of the plurality of cylindrical battery cells (30) to connect the plurality of cylindrical battery cells (30) with each other in series or in parallel or in a combination of series and parallel. The battery module (10) as claimed in claims 8 and 9, wherein: the terminals located at the first end (32) of the plurality of cylindrical battery cells (30) and the interconnectors (52) for connecting them are enveloped by the adhesive (40); and the terminals located at the second end (34) of the plurality of cylindrical battery cells (30) and the interconnectors (52) for connecting them are exposed outside the adhesive (40).