Description:FIELD OF THE INVENTION
[001] The present invention generally relates to an energy storage device. More particularly, the present invention relates to a structure for connecting a plurality of cells in an energy storage device.

BACKGROUND OF THE INVENTION
[002] With advancements in automobile (vehicle) technologies, currently there seems to be greater focus laid on advancement of energy, and in particular green energy. The global community of automobile manufacturers is constantly improving and producing newer automobiles that operate on green and clean energy, thereby trying to reduce the carbon footprint and contribute to a safer environment. However, the quest to achieve green and clean energy also come with an increased demand of providing advanced and long-lasting technology in energy storage and consumption.
[003] In conventional electric vehicles, performance of the vehicle may normally depend on the power and energy capacity of the battery pack provided with the vehicle, which may degrade over time. Currently, battery packs (also referred to as energy storage devices) normally make use of cylindrical cells in order to provide higher energy density, higher working voltage, longer durability, higher reliability, and better susceptibility to heat that may be generated during discharge and recharge cycles. A disadvantage of the current energy storage devices is the high cost of manufacturing these energy storage devices that may be driven a further by a complexity involved in interconnecting a large number of cells. The interconnection of the large number of cells in the energy storage device is normally achieved by using wires, cables or a metal strip welded to the terminals of the cells. Conventional cell interconnection methods are generally susceptible to fail during longer term operation, for example, due to constant vibration that occurs during the movement of the vehicle.
[004] Moreover, a large number of the cells of an energy storage devices are interconnected by means of an electric current collector busbar. These electric current collector busbars for battery packs are required to be durable, capable of withstanding high level of vibration by providing rigidity to keep integrity of the battery module assembly while being flexible enough to cope with thermal and G- forces.
[005] Moreover, current battery packs use Nickel as the battery pack can provide high resistance to electrical conductivity. This results in cell imbalance issues due to a limited electrical conductivity of the interconnect as the interconnect uses a relatively large percentage of Nickel. A further disadvantage is that Nickel has a much lower tensile strength and Nickel is highly expensive compared to a number of other conducting material.
[006] However, a typical material composition for a busbar is Nickel in combination with other materials, where nickel is present up to 99% in the composition of the busbar. Nickel as the interconnector material for lithium-ion cells is responsible to connect cells in different configurations, for example in a series configuration or in a parallel configuration, for carrying electric current in the vehicle. The disadvantage of using such a composition having nickel in large ratio is cell imbalance, lower tensile strength making it susceptible to break under vibrational loads or on road endurances. Further, the manufacturing cost of such a busbar is very high, and it also provides high resistance to electric conductivity. Additionally, such a composition having nickel is that nickel plating is a complicated and time-consuming manufacturing process.
[007] Thus, there is a need in the art for a structure for connecting a plurality of cells in an energy storage device, which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[008] In one aspect, the present invention is directed towards a structure for connecting a plurality of cells in an energy storage device. The structure (interconnect) comprises a composite, wherein the composite has at least two materials. The at least two materials are combined in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of the energy storage device. For example, an admixture of the at least two materials in a pre-determined weight/weight ratio forms the composite.
[009] In an embodiment of the invention, the composite in the structure includes a first material, wherein the first material may be copper, and is in pre-determined ratio in a range between 90 to 97 w/w of the composite. The composite further includes a second material, wherein the second material may be nickel, and is in a pre-determined ratio in a range between 3 to 10 w/w of the composite.
[010] In a further embodiment of the invention, the composite in the structure may include a third material, wherein, the third material may be configured to aid blending of the at least two materials forming the composite, the third material may be manganese, and may be in a pre-determined ratio ranging between 0.2 to 0.35 w/w of the composite.
[011] In a further embodiment of the invention, the energy storage device has an outer casing that may be configured to accommodate one or more modules, wherein the one or more modules includes a plurality of cells. The structure, for example the interconnect, may be configured to electrically connect a plurality of cells of the one or more modules hosted within the casing. In a further aspect of the disclosure, the structure (interconnect) comprises a composite that comprises at least two materials, wherein the at least two materials are in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of an energy storage device.
[012] In a further embodiment of the invention, the composite in the energy storage device includes a first material, wherein the first material of the composite is copper. A pre-determined ratio of the first material ranges between 90 to 97 w/w of the composite. The composite includes a second material, wherein the second material is nickel. The pre-determined ratio of the second material ranges between 3 to 10 w/w of the composite.
[013] In a further embodiment of the invention, the composite in the energy storage device may include a third material, wherein the third material is manganese. The pre-determined ratio of the third material ranges between 0.2 to 0.35 w/w of the composite, and the third material may be configured to aid blending of the at least two materials. The structure is at least one of a busbar or an interconnector for the energy storage device.
[014] In another aspect, the present disclosure relates to a method for manufacturing a structure (interconnect) used to connect the plurality of cells in an energy storage device. The interconnect (also referred to as a structure) may be configured for connecting a plurality of cells in an energy storage device. The method of manufacturing the interconnect includes melting at least two materials to form a first molten composite, wherein the at least two materials are in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of the energy storage device. A further aspect of the disclosure includes melting a third material and adding the molten third material to the first molten composite, wherein the molten third material is configured to aid blending of the at least two materials to form a second molten composite. A further aspect of the disclosure includes cooling the second molten composite to form a solidified composite and stamping the solidified composite to obtain the interconnect or the structure.
[015] In a further embodiment of the invention, the first molten composite has a first material, wherein the first material being copper, and has a pre- determined ratio ranging between 90 – 97 w/w of the composite. The first molten composite has a second material, wherein the second material is nickel, and has a pre-determined ratio ranging between 3 – 10 w/w of the composite. The third material may be manganese and has a pre-determined ratio ranging between 0.2 – 0.35 w/w of the composite.

BRIEF DESCRIPTION OF THE DRAWINGS
[016] 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 an exemplary energy storage device, in accordance with an embodiment of the present invention.
Figure 2 illustrates an exemplary structure for connecting a plurality of cells in an energy storage device, in accordance with an embodiment of the present invention.
Figure 3 illustrates an exemplary method for manufacturing a structure for connecting a plurality of cells in an energy storage device, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[017] The present invention generally relates to relates to an energy storage device. More particularly, the present invention relates to a structure for connecting a plurality of cells in an energy storage device.
[018] Figure 1 illustrates an energy storage device 100. The energy storage device 100 is provided with an outer casing 110. The outer casing 110 is configured to accommodate one or more modules in a pre-determined orientation (not shown in the Figure). The one or more modules have a plurality of cells placed at pre-determined orientation within the outer casing 110. The plurality of cells is coupled or connected to each other by means of a structure (hereinafter also referred to as an interconnect or interconnector), to ensure that proper electrical connectivity exists in the energy storage device 100. The energy storage device 100 may be provided in an vehicle, and placed at a pre-determined location within the vehicle, such that the energy storage device 100 may be charged and discharged when the vehicle is in use. The outer casing 110 may be made of a suitable material which may include an inorganic material or an organic material, and the casing 110 is designed to be conducting in nature, and conductive outer casing is preferred for battery packs owing to the heat radiating capabilities of the energy storage device. In an exemplary embodiment, poly vinyl chloride (PVC) may be used for making the outer casing 110. The outer casing 110 comprises several other components such as heat radiating surfaces and openings for permitting venting which are not disclosed here as these do not fall within the scope of the present disclosure.
[019] Herein, as referenced in Figure 2, which illustrates a structure 200 for connecting a plurality of cells in an energy storage device 100. The shape and size of the structure 200 may vary depending on the design needs and the interconnection points that are connecting a plurality of cells in the energy storage device, and it should be obvious to a person of ordinary skill in the art that all such variation fall within the scope of the present disclosure. The structure 200 comprises a first point 212 which may be connected to at least one of a negative terminal and a positive terminal of each cell of the plurality of cells of the energy storage device 100 based on a desired electrical configuration to be established between the plurality of cells. The structure 200 comprises a second point 214, which are vents configured for providing venting for the structure 200, and further reduce the material used for creating the structure and the weight of the structure 200. It should be obvious to a person of ordinary skill in the art that the structure may be provided with or without the vents, however for ease of understanding the structure 200 according to the present invention is illustrated as having vents. In an alternate embodiment, fins may be provided on the structure as a heat sink instead of vents 214.
[020] The energy storage device 100 essentially comprises a plurality of cells and the plurality of cells are connected to each other by means of the structure 200 thereby ensuring proper electrical conductivity exists in the energy storage device 100 and the plurality of cells forming the energy storage device 100. As discussed previously, the shape and size of the structure 200 may vary depending on the number of cells in the energy storage device and the size of the energy storage device. As discussed previously, the shape and size of the structure may also vary depending on the provisions to be made for the structure, wherein in some cases vents may be provided and in some cases fins may be provided over the structure for the purpose of venting or cooling the structure 200.
[021] The structure 200 comprises a composite, for example an admixture of at least two materials in a pre-determined ratio. In an exemplary embodiment, the composite may be an alloy. In an exemplary embodiment, the least two materials forming the composite may be combined in a pre- determined weight/ weight (w/w) ratio of the total composite weight. In an exemplary embodiment, the pre-determined weight/weight (w/w) ratio may be based on pre-determined or a requisite current carrying capacity of the one or more loads drawing current or voltage from the energy storage device 100.
[022] In an exemplary embodiment, the structure 200 comprises a composite, wherein the composite comprises at least two materials. In an exemplary embodiment, the at least two materials may be an inorganic material or an organic material or a combination thereof. In an exemplary embodiment, the at least two materials may be good conductors of electricity, and the at least two materials may be chosen such that for example the electrical transmission losses may be minimized. Various other factors may be considered while selecting this material, for example a thickness of the material required for forming the structure 200, a flexibility associated with the at least two materials etc., to form the composite, and all such factors fall within the scope of the present disclosure. In an exemplary embodiment, the at least two materials used to form the structure 200 may be combined in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of the energy storage device. In an exemplary embodiment, various other parameters may also be considered to form the composite, and it should be obvious to one of ordinary skill in the art that all such factors for designing and forming the structure 200 fall within the scope of the present disclosure.
[023] In an exemplary embodiment, an admixture of at least two materials in a pre-determined weight/weight ratio may be used to form the composite that will form the structure 200, which will then be used to connect the plurality of cells in the energy storage device. In an exemplary embodiment, the composite that forms the structure 200 may include a first material, wherein the first material may be either an inorganic or organic conducting material. In a preferred embodiment, copper may be used as the first material. In an exemplary embodiment, the first material is in pre-determined ratio in a range between 90 to 97 w/w of the composite that forms the structure 200.
[024] In an exemplary embodiment, the composite that forms the structure 200 may include a second material, wherein the second material may be either an inorganic or organic conducting material. In a preferred embodiment, nickel may be used as the second material. In an exemplary embodiment, the second material is in pre-determined ratio in a range between 3 to 10 w/w of the composite that forms the structure 200.
[025] In a preferred embodiment, copper may be used as the first material and nickel as the second material because of the good conducting nature of the copper and nickel, and a composite formed by copper and nickel have a high-thermal stability, enabling them to maintain their mechanical properties and resist degradation at elevated temperatures. Further, a composite formed from copper and nickel is also corrosion resistant, hardenability, weldability, and castability.
[026] In an exemplary embodiment, the composite that forms the structure 200 may comprise a third material. In an exemplary embodiment, the third embodiment may include an inorganic or an organic conducting materiaḷ. In a preferred embodiment, based on the at least two materials chosen to make the structure 200, i.e., copper and nickel, the third material may be chosen to be manganese, where the third material is configured to aid blending of the at least two materials forming the composite. In an exemplary embodiment, the third material may be in a pre-determined ratio, where the pre-determined ratio of the manganese ranges between 0.2 to 0.35 w/w of the composite, which is a small percentage of the total w/w ratio of either the first material or the second material and may be considered to be negligible. However, the use of a third material aid in blending the first material and the second material forming the structure 200. In another preferred embodiment, a combination of a first material and a second material may be found such that no blending agent or third material may be required to form the structure 200. In an exemplary embodiment, other minerals may be used which include and are not limited to halogens, sodium, other elements based on specific application of the energy storage device.
[027] In an exemplary embodiment, the energy storage device may have an outer casing 110 that may be configured to accommodate one or more modules, wherein the one or more modules comprises a plurality of cells, and the plurality of cell are connected by means of the structure 200. In an exemplary embodiment, the structure 200 comprising the composite formed may have a tensile strength greater than 1000 MPa, and a breaking point stress greater than 500 MPa and may also have a maximum load strain greater than 1.1%. Further, the composite has a lower resistance when used to conduct electric current as compared to other conventionally used materials.
[028] In an embodiment, as referenced in Figure 3, which illustrates a method of manufacturing or producing the structure 200 disclosed in Figure 2. At step 310, at least two materials are chosen and the at least two materials are molten to form a first molten composite. In an exemplary embodiment, the at least two materials may be an inorganic material or an organic material or a combination thereof. In yet a further exemplary embodiment, the at least two materials may be conducting material. In an exemplary embodiment, the at least materials may be chosen in a pre-determined weight/weight (w/w) ratio of the composite. In an exemplary embodiment, the pre-determined weight/weight (w/w) ratio is based on pre- determined or requisite current carrying capacity of the energy storage device. The first material is in pre-determined ratio in a range between 90 to 97 w/w of the composite and the second material is in a pre-determined ratio in a range between 3 to 10 w/w of the composite.
[029] At step 320, a third material is melted. In an exemplary embodiment, the third material is in a pre-determined ratio, where the pre-determined ratio of the manganese ranges between 0.2 to 0.35 w/w of the composite, which is a small percentage of the total w/w ratio of either the first material or the second material. At step 330, the molten third material is added to the first molten composite, wherein the first molten composite comprises an admixture of the at least two materials in a molten state, and the molten third material added to the first molten composite to aid blending the admixture of the first molten composite comprising the at least two materials to form a second molten composite.
[030] After addition of the molten third material to the molten admixture of the at least two material that comprise the first molten composite. At step 340, the second molten composite is cooled in order to form a solidified composite. Once the second molten composite is cooled, at step 350, the solidified composite is stamped or forged to obtain the structure as desired, which may be of a desired shape and size. The structure being any one of an interconnector and a busbar.
[031] Accordingly, in an embodiment, to order to securely connect the interconnector onto the plurality of cells in the energy storage device as well as achieve other electrical connections, the structure may be joined for example using resistive spot welding (RSW), wire welding and laser welding. It should be obvious to a person or ordinary skill in the art that other techniques may be used for joining the structure to a plurality of cells and all such techniques fall within the scope of the present disclosure.
[032] In an embodiment, the type of process used for joining may be decided based on the type of cells being connected. In an exemplary embodiment, for cylindrical cells resistive spot welding (RSW) may be preferred. In another exemplary embodiment, for prismatic or pouch cells laser welding or wire welding would be the preferred option. In a further exemplary embodiment. For instance, for RSW the presence of nickel material in the interconnector or bus bar may be mandatory.
[033] In an exemplary embodiment, copper is chosen because of the several advantageous properties exhibited by copper. In an exemplary advantageous embodiment, copper is an excellent conductor of electricity. In an exemplary advantageous embodiment, copper assists in thermal regulation and the heat may be effectively dissipated through copper material. In an exemplary advantageous embodiment, copper has a minimal resistance being provided to impede current flow. In an exemplary advantageous embodiment, copper is easily available and is cheaper compared to many other metals. In an advantageous exemplary embodiment, copper assists/ facilitates laser welding thereby making the interconnector adaptable to withstand multiple joining processes. In an exemplary advantageous embodiment, Copper has a high tensile strength, which makes the interconnector suitable for high power applications as well as for withstanding endurances during operation such as impact and vibrational loads. In an advantageous exemplary embodiment, cell imbalances occurring in the battery pack are reduced due to reduced resistances provided by the copper material.
[034] In a further exemplary advantageous embodiment, Nickel is used for the purposes of facilitating resistive spot welding and owing to a high cost associated with Nickel, Nickel is at kept at a minimum 3% w/w of the composite and ensured that it is not more than 10% w/w of the composite. In an further exemplary advantageous embodiment, Manganese assists in blending of the copper with nickel during composite or alloy formation for making the interconnector.
[035] Advantageously, the present invention provides a system and method for a structure for connecting a plurality of cells in an energy storage device that significantly improves the performance of the energy storage device. The present invention achieves this by using copper, nickel and manganese for enhancing the electrical conductivity in the energy storage device. The present invention is a simplified manufacturing process by incorporating a composite thereby reducing manufacturing cost and providing a cost-effective interconnector.
[036] The present invention ensures that the energy storage device has higher tensile strength and a high force at break ratio. Thereby, improving the durability of the energy storage device, thus providing a robust energy storage device that is not susceptible to breakage under vibrational loads or on-road endurances. Further, the present invention ensures reduced resistance during conduction of the electric current, further optimizing the performance of the energy storage device.
[037] 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 modification may be made without departing from the scope of the invention as defined in the following claims.
List of Reference Numerals
100: An energy storage device
110: Casing
200: A structure
212: First Point
214: Second Point
300: Method for manufacturing a structure , Claims:WE CLAIM:
1. A structure (200) for connecting a plurality of cells in an energy storage device (100), the structure (200) comprising:
a composite,
the composite comprising at least two materials, wherein the at least two materials being combined in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of the energy storage device.

2. The structure (200) as claimed in claim 1, wherein the composite comprises a first material, the first material being copper; and the first material being in a predetermined ratio in a range between 90 to 97 w/w of the composite.

3. The structure (200) as claimed in claim 1, wherein the composite comprises a second material, the second material being Nickle; and the second material being in a predetermined ratio in a range between 3 to 10 w/w of the composite.

4. The structure (200) as claimed in claim 1, wherein a ratio of the first material to the second material being a minimum 9 parts of the first material with a maximum 1 part of the second material.
5. The structure (200) as claimed in claim 1, wherein the composite comprises a third material of pre-determined w/w ratio of the composite; and wherein the third material being configured to aid blending of the at least two materials of the composite.

6. The structure (200) as claimed in claim 5, wherein the third material being Manganese; and wherein the pre-determined ratio of the third material being in ranges between 0.2-0.35 w/w of the composite.

7. An energy storage device (100), the energy storage device (100) comprising:
a casing (110), the casing (110) being configured to accommodate one or more modules, the one or more modules comprises a plurality of cells; and
a structure (200), the structure (200) being configured to electrically connect the plurality of cells of the one or more modules,
wherein the structure (200) comprising: a composite comprising at least two materials, wherein the at least two materials being in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of the energy storage device (100).

8. The energy storage device (100) as claimed in claim 7, wherein the composite comprises a first material, the first material being copper, and the pre-determined ratio of the first material being in ranges between 90 to 97 w/w of the composite.

9. The energy storage device (100) as claimed in claim 7, wherein the composite comprises a second material, the second material being Nickle, and the pre-determined ratio of the second material being in ranges between 3 to 10 w/w of the composite.

10. The energy storage device (100) as claimed in claim 7 comprising a third material of pre-determined w/w ratio, the third material being configured to aid blending of the at least two materials, and wherein the third material being Manganese, and the pre-determined ratio of the third material being in ranges between 0.2-0.35 w/w of the composite.

11. The energy storage device (100) as claimed in claim 10, wherein the structure (200) being at least one of a busbar of the battery pack (100) and an interconnector of the energy storage device (100).

12. A method (300) for manufacturing a structure (200), the structure (200) being configured for connecting a plurality of cells in an energy storage device (100), the method (300) comprising:
- melting (310) at least two materials to form a first molten composite, wherein the at least two materials being in a pre-determined weight/weight (w/w) ratio based on a requisite current carrying capacity of the energy storage device (100)
- melting (320) a third material;
- adding (330) the molten third material to the first molten composite, wherein the molten third material being configured to aid blending of the molten first composite to form a second molten composite;
- cooling (340) the second molten composite to form a solidified alloy; and
- stamping (350) the solidified alloy to obtain the structure (200).

13. The method (300) as claimed in claim 12, wherein the first molten composite comprises a first material, the first material being copper, and the pre-determined ratio of the first material being in ranges between 90 to 97 w/w of the composite.

14. The method (300) as claimed in claim 12, wherein the first molten composite comprises a second conducting material, the second material being Nickle, and the pre-determined ratio of the second material being in ranges between 3 to 10 w/w of the composite.

15. The method (300) as claimed in claim 12, wherein the third material is Manganese, and the third material being in a pre-determined w/w ratio of a third material ranging between 0.2-0.35 w/w of the composite.

Dated this 26 day of July 2023

TVS MOTOR COMPANY LIMITED
By their Agent & Attorney

(Nikhil Ranjan)
of Khaitan & Co
Reg No IN/PA-1471