Description:FIELD OF THE INVENTION
[001] Present invention relates to a battery. Particularly, the present invention relates to a venting structure for a battery pack.

BACKGROUND OF THE INVENTION
[002] Batteries are usually sealed to improve reliability of batteries and to meet basic waterproof and dustproof requirements. In the usage of the battery, battery failure caused by battery heating or altitude changes affects the safety of the battery, resulting in different internal pressure and external pressure of the battery. However, too high or too low air pressure inside the battery is likely to cause structural damage of the sealing surface, resulting in battery failure.
[003] Typically, the batteries used in vehicles include Lithium-Ion (Li-Ion) batteries. The safety of the Li-ion batteries in the vehicles is a priority of the automotive industry. Fire and explosion may pose a danger due to chemical reactions, chemical risk due to toxic liquids and gases, thermal danger due to high temperatures, and short circuit due to nail penetration event. The said events may trigger thermal runaway and thus the safety of the battery pack is a huge requirement in the automotive industry.
[004] The Li-ion batteries typically present one or more safety concerns. If the Li-ion batteries are short-circuited or exposed to a high temperature, exothermic reactions can be triggered, resulting in a self-enhanced increasing temperature loop known as “thermal runaway” that can lead to battery fires and explosions. Typically, the Li-ion battery uses a polymer separator and a flammable electrolyte, which are both constrained to certain temperature limits for safe performance. When the Li-ion battery’s temperature increases to approximately 130–150 ͦ C, the high-energy materials and the organic components are not stable and are prone to generate more heat. If the generated heat does not dissipate, the battery temperature will further increase and accelerate the heat-releasing process.
[005] Existing small cell batteries and large cell batteries have several serious drawbacks. For small cells such as, but not limited to, 18650 cells, they usually have disadvantages constrained by a housing or “can” and are partly due to mechanical stress or electrolyte depletion, cycle life and calendar life and cause restrictions. When the Li-ion battery is charged, these electrodes expand. Being a “can” limits the jelly roll structure of the electrode and creates mechanical stresses in a jelly roll structure that limit the life cycle. As more and more storage capacity are desired, more active anode and cathode materials are inserted into a given volume of “can”, which further creates mechanical stress on the electrodes.
[006] Similar to pouch cells, electrodes are stack in the laminated pouch. During cell formation, gases (initial cell cycle formed gases) are ejected during manufacturing of the cell itself. Even though there may be a possibility of gases built by cycling over the period, these gases should be vented out immediately. Else, the laminated pouch may look swelling like condition because of the gas built up. The swelling effect is always a danger situation for the batteries, and it may lead an explosion any time. So, it is required to vent out these built-up gases safely without any disturbance.
[007] Another problem with large cells is safety. The energy released in the cell going into thermal runaway is proportional to the amount of available electrolyte present in the cell during the thermal runaway scenario. As the cell becomes larger, more free space is available for the electrolyte to fully saturate the electrode structure. Since the amount of electrolyte per Wh for large cells is usually greater than the small cells, large cell batteries are generally systems that gain more momentum during a thermal runaway and are therefore less secure. However, any thermal runaway may depend on a specific scenario, but generally, the larger the fuel (electrolyte), the larger is the flame. In addition, once a large cell is in thermal runaway mode, the heat generated by the cell triggers a thermal runaway reaction in adjacent cells, causing the entire pack being destroyed, with massive destruction to the battery pack and peripheral devices. A user may also be in a dangerous state by causing a cascade effect to ignite.
[008] Many attempts have been made in order to provide safety aspects in the batteries used in the vehicles or in any electronic / electrical appliances. In one existing methods, a battery relief valve is provided in the battery. The battery relief valve is a bidirectional pressure relief valve. The bidirectional pressure relief valve has a valve seat, a first valve core, and a second valve core. The valve seat is provided with a first end part and a second end part opposite one another, and a channel and a dividing plate. The channel passes through the first end and the second end. The dividing plate is provided with a first pressure relief hole. The dividing plate is arranged on the inner wall of the channel. In the axial direction of the channel, the dividing plate divides the channel into a first chamber and a second chamber. Further, a portion of the first valve core is positioned within the first chamber and is configured to open or close the first pressure relief hole, in order to communicate or isolate the first chamber and the second chamber. Furthermore, a portion of the second valve core is positioned within the second chamber and is configured to open or close the second pressure relief hole to communicate or isolate the first chamber and the second chamber. The second pressure relief hole is provided in the dividing plate or the first valve core.
[009] In yet another existing method, a venting device is inserted into the sealing portion of a pouch of a secondary battery, and a housing is inserted between both sides of the sealing portion and sealed together with the sealing portion. A sheet formed inside the housing, made of a polymer, and having a passage formed therein for communicating with the inside and outside of the pouch is provided. A leaf spring is provided for opening and closing the passage according to the internal pressure of the pouch. The leaf spring is made of metal and has a surface treatment layer formed on an inner surface of one side.
[010] In still another existing method, a battery venting system is provided. The venting system includes case, a cap plate which is installed in the case and a vent hole, and a safety vent which is coupled to the vent hole of the cap plate. The safety vent ruptures when the internal pressure of the case is greater than a reference pressure.
[011] In yet another existing method, the Li-ion batteries include materials that provide endothermic functionalities contributing to the safety and stability of the batteries. The endothermic materials may include a ceramic matrix incorporating an inorganic gas-generating endothermic material. If the temperature of the Li-ion battery rises above a predetermined level, the endothermic materials serve to provide one or more functions to prevent and/or minimize the potential for thermal runaway, e.g., thermal insulation (particularly at high temperatures); (ii) energy absorption; (iii) venting of gases produced, in whole or in part, from endothermic reaction(s) associated with the endothermic materials, (iv) raising total pressure within the battery structure; (v) removal of absorbed heat from the battery system via venting of gases produced during the endothermic reaction(s) associated with the endothermic materials, and/or (vi) dilution of toxic gases (if present) and their safe expulsion from the battery system.
[012] In yet another existing method, a bidirectional pressure relief valve is provided in the battery. The bidirectional pressure relief valve includes a valve seat, a first valve element and a second valve element. The valve seat has a first end and a second end opposite each other. The bidirectional pressure relief valve further includes a channel and a partition plate. The channel is penetrating the first end and the second end. A first pressure relief hole is provided on the partition plate. The partition plate is arranged on an inner wall of the channel and dividing the channel into a first cavity and a second cavity in an axial direction of the channel. The bidirectional pressure relief valve of the application is applied to the battery to maintain balance between internal pressure and external pressure of the battery.
[013] In yet another existing method, a thermal mitigation is provided in the battery module. The battery module includes a heat exchange member. The heat exchanger includes a container with a heat transfer fluid disposed therein. In one form, the heat transfer fluid is capable of going through a phase change as a way to absorb at least a portion of heat present in or generated by battery cell. A pressure control device cooperates with the container and heat transfer fluid such that upon attainment of a predetermined thermal event within the battery cell, the pressure control device permits liberation of a portion of the heat transfer fluid to an ambient environment, thereby relieving pressure on the container and removing some of the excess heat caused by the thermal event.
[014] The thermal runaways create a pressure build-up in battery housings. The pressure must be evacuated quickly. If not, the risk of an explosion becomes a reality. In addition, the thermal runaway may be triggered if a battery has certain defects that can lead to short-circuiting, overheated, subject to high pulse power usage, or punctured.
[015] Thus, there is a need in the art for providing a venting structure for a battery pack which addresses the aforementioned problems and limitations.

SUMMARY OF THE INVENTION
[016] In one aspect, the present invention is directed to a venting structure for a battery pack comprising a plurality of battery modules. The venting structure comprises a plurality of first tubular members, each first tubular member comprising: a first portion connected to a plurality of cells of the battery modules of the battery pack; and a second portion distal to the first portion, wherein the first portion being configured eject one or more gases from the battery module to the second portion when there is a pressure build-up in the battery module; a second tubular member, the second tubular member connected to the second portion of each of the first tubular members and having a common outlet; and a third member, the third member is connected to the common outlet of the second tubular member.
[017] In an embodiment, the venting structure comprises a pressure relief valve connected to the third member. The pressure relief valve is being configured to open when an internal pressure is built up due to an increase in temperature of the battery module, thereby degassing the one or more gases generated by the plurality of cells of the battery modules during a thermal runaway event.
[018] In a further embodiment, the pressure relief valve is made of a heat resistant material comprising silicon.
[019] In a further embodiment, the third member is in curved shape or a slant shape, and a profile of the curved shape is having pre-defined radius.
[020] In a further embodiment, the first tubular member, the second tubular member and the third member being made of a polymeric material comprising rubber.
[021] In a further embodiment, the battery pack being a pouch cell battery pack.
[022] In a further embodiment, an axis of each of the first tubular members is oriented transversely with respect to an axis of the second tubular member.
[023] In a further embodiment, the venting structure being configured to release the one or more gases from the plurality of cells in at least two states of operation of the battery pack, wherein the at least two states of operation of the battery pack comprises a first state being a normal operation and a second state being of the thermal runaway.
[024] In another aspect, the present invention is directed to battery pack for a vehicle, comprising: a plurality of battery modules, each battery modules comprising a plurality of cells; a venting structure connected to the battery modules comprising a plurality of first tubular members, each first tubular member comprising: a first portion connected to the plurality of cells of the battery module of the battery pack; and a second portion distal to the first portion, wherein the first portion being configured eject one or more gases from the battery module to the second portion when there is a pressure pile up in the battery module; a second tubular member, the second tubular member connected to the second portion of each of the first tubular members and having a common outlet; and a third member, the third member connected to the common outlet of the second tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS
[025] 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.
Figures 1 and 2 show perspective views of a battery pouch having a venting structure, in accordance with an embodiment of the present invention.
Figure 3 shows a perspective view of a battery module having one or more battery pouches and having the venting structure, in accordance with an embodiment of the present invention.
Figure 4 shows a top view of the battery pack having the venting structure, in accordance with an embodiment of the present invention.
Figure 5 shows a magnified perspective view of the battery pack having the venting structure and a pressure relief valve, in accordance with an embodiment of the present invention.
Figure 6 shows a perspective view of the battery pack with venting structure having a curved third member, in accordance with an embodiment of the present invention.
Figure 7 shows a front view of the battery pack shown in Figure 6, in accordance with an embodiment of the present invention.
Figure 8 shows a side view of the battery pack shown in Figure 6, in accordance with an embodiment of the present invention.
Figure 9 shows a perspective view of the battery pack with venting structure having a slanted third member shown in Figure 5, in accordance with an embodiment of the present invention.
Figure 10 shows a front view of the battery pack shown in Figures 9, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[026] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder.
[027] Present invention relates to a battery. Particularly, the present invention relates to a venting structure 100 for a battery pack 10.
[028] Figures 1 and 2 illustrate perspective views of a battery pouch 12A of a battery module 12 (shown in Figure 3) and having a venting structure 100, in accordance with an embodiment of the present invention. In the illustrated embodiment, the battery pouch 12A may be of Lithium-ion (Li-ion) type. However, the said Li-ion is an exemplary embodiment and should not meant to be limiting the scope of the present invention. The battery module 12 having a pouch design may include glass-to-metal electrical feed-through and conductive foil tabs welded to electrodes and brought to an outside in a fully sealed manner. The pouch type of batteries may be a lightweight, flexible and simple in construction and cells in the pouch may deliver high load currents. The pouch type batteries may provide space and/or packing advantages as well. However, the pouch type batteries pose inflation or swelling problem due to formation of gases and therefore, in order to provide safety due to the inflation of the battery pouches 12A, degassing is necessary.
[029] Figure 3 illustrates a perspective view of the battery module 12 having one or more battery pouches 12A and the venting structure 100, in accordance with an embodiment of the present invention. In an embodiment of the present invention, the battery pack 10 is a pouch cell type battery pack.
[030] As illustrated in the Figure 3, the venting structure 100 comprises a plurality of first tubular members 110. Each of the first tubular member 110 comprises a first portion 112 (shown in Figure 2) connected to a plurality of cells of the battery modules 12 of the battery pack 10. That is to say, the first portion 112 of each of the first tubular member 110 is connected to the plurality of cells of the battery pouches 12A of the battery modules 12. The first tubular member 110 further comprises a second portion 114 (shown in Figure 2). The second portion 114 is distal to the first portion 112. In an embodiment, the first portion 112 is configured to eject one or more gases from the battery pouches 12A of the battery module 12 to the second portion 114 when there is a pressure build-up in the battery pouches 12A of the battery module 12. In some embodiments, the first portion 112 is configured to continuously eject one or more gases from the battery pouches 12A of the battery module 12 to the second portion 114.
[031] Referring to Figures 1 – 5, the venting structure 100 further comprises a second tubular member 120. The second tubular member 120 is connected to the second portion 114 of each of the first tubular members 110 (shown in Figure 2). The second tubular member 120 has a common outlet 120A (shown in Figure 5). As illustrated in Figure 5, an axis A-A’ of each of the first tubular members 110 is oriented transversely with respect to an axis B-B’ of the second tubular member 120. It may also be contemplated that the first tubular members 110 may be oriented to the second tubular members any feasible angle that would facilitate easy or smooth venting of the gases.
[032] Referring to Figures 5 – 7, the venting structure 100 further comprises a third member 130. The third member 130 is connected to the common outlet 120A of the second tubular member 120. In some embodiments, the third member 130 is a tubular member which extends from the common outlet 120A of the second tubular member 120. In an embodiment, the third member 130 is in a curved shape (shown in Figure 6 and 7), or a slant shape (shown in Figures 5, 9 and 10). In a further embodiment, a profile of the curved shape of the third member 130 is having pre-defined radius R1 (shown in Figure 7). Thus, the third member 130 forms a curved path in the venting structure 100. In some embodiments, the curved path or the slant shape ensures smooth passing of the generated gases towards a pressure relief valve 140 of the venting structure 100. This also ensures smooth degassing and packaging such that the first tubular members and the second tubular member are diverted to the pressure relief valve 140.
[033] In an embodiment, the first tubular member 110, the second tubular member 120 and the third member 130 are made of a polymeric material, including, but not limited to, a rubber. In some embodiments, the venting structure 100 as disclosed in the present invention having the first tubular member 110, the second tubular member 120 and the third member 130 are microcapillary in nature. The first portion 112 of each of the first tubular member 110 is inserted in a laminated pouch terminal of the battery module 12, and thereafter closed /sealed. In some embodiments, the battery pack 10 having the pouch cells typically generate gases because of continuous charge and discharge cycles. Therefore, continuous degassing is required to avoid any bulging of the pouch cells of the battery pouches 12A. The microcapillary tubular members (first tubular member 110, the second tubular member 120 and the third member 130) ejects gases automatically whenever there is a pressure pile up. During the pressure pile up, capillary type of tubular members gets a path to move the generated gases.
[034] In some embodiment, the venting structure 100 having the first tubular members and the second tubular members enable continuous degassing in the battery pack 10 and not only during an event of thermal runaway. The term ‘thermal runaway’ is an exothermic reaction which may occur inside a Li-ion battery when the battery is damaged or short-circuited. Typically, in the Li-ion batteries, a cathode and an anode are separated by a thin layer of polyethylene barrier. In case the barrier is damaged, a short circuit could occur, resulting in decomposition of materials inside the cell. The reactions due to decomposition are exothermic, thereby quickly rising temperature in the battery to a melting point of lithium. This may cause a chain reaction and heating inside the battery. Cells in the battery may eventually be unstable and releases its energy to the environment, resulting in a thermal runaway condition in the battery. During the thermal runaway events, the battery would get heated up resulting in disintegrating of the cells of the electrolytes and release of gases. The gases would build up pressure and temperature inside the batter and may lead to explosion of the battery.
[035] As shown in Figures 4 – 7, the venting structure 100 comprises the pressure relief valve 140 connected to the third member 130. The term ‘pressure relief valve’ and the ‘venting valve’ as used herein are interchangeably used. However, the said terms ‘pressure relief valve’ and the ‘venting valve’ relate to the same component, and the term ‘venting valve’ is used in place of pressure relief valve for brevity. The venting valve 140 is configured to open when an internal pressure is built up due to an increase in temperature of the battery module 12, thereby degassing the one or more gases generated by the plurality of cells of the battery modules 12 during a thermal runaway event. In an embodiment, the venting valve 140 is made of a heat resistant material, including but not limited to, silicon. However, it may also be contemplated that any other heat resistant material may be used for manufacturing the venting valve 140.
[036] In an embodiment, the venting structure 100 as disclosed in the present invention is configured to release the one or more gases from the plurality of cells in at least two states of operation of the battery pack 10. The two states of operation of the battery pack 10 include, a first state being a normal operation and a second state being of the thermal runaway.
[037] In an embodiment, the venting structure may include a breather or membrane type opening. However, any other type of opening which eject the thermal runaway gases can be suitably incorporated in the venting valve 140 of the venting structure 100.
[038] In another aspect of the present invention, it is directed to a battery pack 10 for a vehicle (not shown). The battery pack 10 includes a plurality of battery modules 12. Each of the battery modules 12 comprises a plurality of cells. The battery pack 10 comprises the venting structure 100 connected to the battery modules 12.
[039] Advantageously, present invention of the venting structure provides degassing the gases that are generated during a thermal runaway event, balances the pressure inside the battery pack in an altitude journey, protects batteries in any thermal runaway and also ensure safety of the vehicle and passengers, and prevents long usage after cell failure and trigger thermal runaway meantime fire also protected. Also, the venting structure as disclosed in the present invention provides solution to any abuse condition in the battery pack that will take to a thermal runaway event which generate enormous amount of heat and gases by ejecting the gases through the venting valve.
[040] The venting structure has properties of high temperature resistant when thermal runaway and protect the lithium cells and the battery pack from maximum damage. In addition, the venting structure solves internal pressure raise problem in the battery pack since the venting valve regulates the gases that generated during the thermal runaway event. The venting structure as disclosed in the present invention saves cost since the safety solution is implemented in the part level of the vehicle.
[041] The venting structure as disclosed in the present invention is applicable to batteries used in two-wheeled vehicles, three-wheeled vehicles, four-wheeled vehicles, or any other vehicle which may include batteries like Li-ion. In addition, the venting structure for batteries may also be applicable in all energy storage application devices, power backup devices, all electronics applications with wireless mode and all future mobility energy storage devices.
[042] The venting structure in the present invention will do both the thermal management (internal pressure management) and gas ejection during the thermal runaway event and thus performs a twin role. However, in the prior arts gas ejection alone or thermal management alone are provided. In the present invention, the venting structure provides a multimodal function through a single venting solution / implementation.
[043] The venting structure as disclosed in the present invention improves the reliability of batteries, meet the basic waterproof and dustproof requirements, prevent structural damage of the sealing surface due to air pressure difference created due to heating of battery or during thermal runaway and prevents swelling effect for individual cells in the battery modules.
[044] 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 and Characters:
10: Battery pack
12: Battery modules
12: Battery Pouch
100: Venting structure
110: First tubular members
112: First portion of the first tubular members
114: Second portion of the first tubular members
120: Second tubular member
120A: Common outlet
130: Third member
140: Pressure relief valve or venting valve
R1: Radius
A-A’: Axis of each of first tubular members
B-B’: Axis of second tubular member
, C , Claims:1. A venting structure (100) for a battery pack (10) comprising a plurality of battery modules (12), the venting structure (100) comprising:
a plurality of first tubular members (110), each first tubular member (110) comprising:
a first portion (112) connected to a plurality of cells of the battery modules (12) of the battery pack (10); and
a second portion (114) distal to the first portion (112), wherein the first portion (112) being configured eject one or more gases from the battery module (12) to the second portion (114) when there is a pressure build-up in the battery module (12);
a second tubular member (120), the second tubular member (120) connected to the second portion (114) of each of the first tubular members (110) and having a common outlet (120A); and
a third member (130), the third member (130) connected to the common outlet (120A) of the second tubular member (120).

2. The venting structure (100) as claimed in claim 1 comprising a pressure relief valve (140) connected to the third member (130), the pressure relief valve (140) being configured to open when an internal pressure is built up due to an increase in temperature of the battery module (12), thereby degassing the one or more gases generated by the plurality of cells of the battery modules (12) during a thermal runaway event.

3. The venting structure (100) as claimed in claim 2, wherein the pressure relief valve (140) is made of a heat resistant material comprising silicon.

4. The venting structure (100) as claimed in claim 1, wherein the third member (130) is in curved shape or a slant shape, and a profile of the curved shape is having pre-defined radius (R1).

5. The venting structure (100) as claimed in claim 1, the first tubular member (110), the second tubular member (120) and the third member (130) being made of a polymeric material comprising rubber.

6. The venting structure (100) as claimed in claim 1, wherein battery pack (10) being a pouch cell battery pack.

7. The venting structure (100) as claimed in claim 1, wherein an axis (A-A’) of each of the first tubular members (110) is oriented transversely with respect to an axis (B-B’) of the second tubular member (120).

8. The venting structure (100) as claimed in claim 1 being configured to release the one or more gases from the plurality of cells in at least two states of operation of the battery pack (10), wherein the at least two states of operation of the battery pack (10) comprises a first state being a normal operation and a second state being of the thermal runaway.

9. A battery pack (10) for a vehicle, comprising:
a plurality of battery modules (12), each battery modules (12) comprising a plurality of cells;
a venting structure (100) connected to the battery modules (12) comprising:
a plurality of first tubular members (110), each first tubular member (110) comprising:
a first portion (112) connected to the plurality of cells of the battery module (12) of the battery pack (10); and
a second portion (114) distal to the first portion (112), wherein the first portion (112) being configured eject one or more gases from the battery module (12) to the second portion (112) when there is a pressure pile up in the battery module (12);
a second tubular member (120), the second tubular member (120) connected to the second portion (114) of each of the first tubular members (110) and having a common outlet (120A); and
a third member (130), the third member (130) connected to the common outlet (120A) of the second tubular member (120).

10. The battery pack (10) as claimed in claim 9 comprising a pressure relief valve (140) connected to the third member (130), the pressure relief valve (140) being configured to open when an internal pressure is built up due to an increase in temperature of the battery module (12), thereby degassing the one or more gases that are generated by the plurality of cells of the battery modules (12) during a thermal runaway event.

11. The battery pack (10) as claimed in claim 9 being a pouch cell battery pack.