Lid for secondary cells

Abstract

A lid (106) for a secondary cell (100, 302) comprises a top surface (214), a bottom surface (220), and a venting portion (208). The venting portion (208) is configured to form an opening when pressure of gas inside the secondary cell (100, 302) is greater than a threshold pressure to release gas from the secondary cell (100, 302). The venting portion (208) is located axially relative to the top surface (214) and relative to the bottom surface (220) without causing load of the lid (106) acting through the venting portion (208) and without causing movement of the lid (106) during the release of the gas.

Description

LID FOR SECONDARY CELLSBACKGROUND

[0001] Batteries are used to provide power to various components in various applications, such as mobile phones, laptops, Electric Vehicle, Hybrid Electric Vehicles, portable devices, clocks, and the like. In particular, in many such applications, batteries that are rechargeable are used. Such batteries are referred to as secondary batteries. In other words, once the secondary batteries discharge the energy stored to power the components, the second batteries can be electrically recharged to their pre-discharge condition to again power the components. The secondary batteries are compact and have high energy capacity. A secondary battery may include a plurality of secondary cells that are electrically connected together.

[0002] In secondary battery, due to various reasons, gas may be generated. For instance, during operation, a secondary cell or an area within a secondary cell of the second battery may achieve elevated temperatures due to various factors, such as thermal failure, mechanical failure, internal short circuiting, external short circuiting, electrochemical abuse, and the like. In this regard, a large amount of gas may be generated. When this scenario is aggravated, the generated gas and elevated temperature may cause damage to adjacent cells. This may also lead to thermal runaway of the secondary cells in the battery and thereby, leading to inflammation or explosion of the battery. Further, during operation, due to electrochemical reactions taking place inside the secondary battery, gas may be generated. In particular, the electrochemical reactions generate by-products and gases, such as Hydrogen Fluoride (HF). In another scenario, due to constant degradation of electrolytes and / or due to constant degradation of battery materials, gas may be generated. This may generate high pressure inside the secondary cell. Accordingly, to ensure proper operation of the battery modules without failing, the high-pressure gas may have to be vented out of the secondary cells.BRIEF DESCRIPTION OF DRAWINGS

[0003] The features, aspects, and advantages of the present subject matter will be better understood with regard to the following description, and accompanying figures. The use of the same reference number in different figures indicates similar or identical features.

[0004] Fig. 1 a illustrates an exploded view of a secondary cell, in accordance with an implementation of the present subject matter.

[0005] Fig. 1 b illustrates a sectional view of a secondary cell, in accordance with an implementation of the present subject matter.

[0006] Fig. 1c illustrates a perspective sectional view of a secondary cell, in accordance with an implementation of the present subject matter.

[0007] Fig. 1 d illustrates a portion of perspective section view of a secondary cell, in accordance with an implementation of the present subject matter.

[0008] Fig. 2a illustrates a top perspective view of a lid of a secondary cell, in accordance with an implementation of the present subject matter.

[0009] Fig. 2b illustrates a top perspective sectional view of a lid of a secondary cell, in accordance with an implementation of the present subject matter.

[0010] Fig. 2c illustrates a bottom perspective view of a lid of a secondary cell, in accordance with an implementation of the present subject matter.

[0011] Fig. 2d illustrates a bottom perspective sectional view of a lid of a secondary cell, in accordance with an implementation of the present subject matter.

[0012] Fig. 2e illustrates a sectional view of a portion of a secondary cell, in accordance with an implementation of the present subject matter.

[0013] Fig. 2f illustrates an enlarged view of a portion of the view illustrated in Fig. 2e, in accordance with an implementation of the present subject matter.

[0014] Fig. 3 illustrates a secondary battery, in accordance with an implementation of the present subject matter.

[0015] Throughout the drawings, identical reference numbers designate similar elements, but may not designate identical elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to illustrate the example shown with better clarity. Moreover, the drawings provide examples and / or implementations consistent with the description; however, the description is not limited to the examples and / or implementations provided in the drawings.DETAILED DESCRIPTION

[0016] Generally, based on shape of cells, secondary batteries are classified into coin-type, cylindrical-type, prismatic type, and pouch-type. In cylindrical-type battery, such as a Lithium (Li) ion, there are a plurality of cylindrical secondary cells that are electrically connected together. For instance, a secondary cylindrical type battery, such as large format cylindrical batteries, includes a plurality of secondary cylindrical cells.

[0017] In the secondary battery, each secondary cell may include an electrode assembly. The electrode assembly is a jelly-roll type electrode assembly. The jelly-roll type electrode assembly may include a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode. The positive electrode and the negative electrode are provided in as a sheet coated with an active material. The positive electrode, the separator, and the negative electrode are wound to form a cylindrical roll. Further, the positive electrode may include one or more positive tabs that are to be connected to a positive terminal at one end of the cell. The negative electrode may include one or more negative tabs that are to be connected to a negative terminal. The components of the secondary cell may be enclosed in a shell.

[0018] During the operation of the secondary cell, there is often generation of high-pressure gas. This gas generation can occur due tointernal electrochemical reactions and constant degradation of electrolytes during battery cycles. Additionally, in some scenarios, electrochemical reactions can produce side products and gases, such as Hydrogen Fluoride (HF). If this gas is not vented out, it can cause thermal damage to other cells of the secondary battery. This may result in inflammation or explosion of the secondary battery. Consequently, the gas generated in each secondary cell must be safely vented out.

[0019] In this regard, in conventional secondary batteries, each secondary cell includes a vent designed to release gas generated inside the secondary cell when internal pressure increases. For instance, the vent may form an opening when internal pressure of the secondary cell increases beyond a threshold. However, conventional venting techniques face challenges in proper, safe, and complete opening. For instance, if the vent encounters obstruction or resistance, the vent may not form an opening. This may lead to partial or incomplete release of gas from inside the secondary cell. The partial venting of gas can result in gas entrapment within the secondary cell. The entrapment of the gas within the secondary cell may cause thermal damage to the secondary cell and to adjacent secondary cells in the battery. In some scenarios, there is a high rate of gas generation. Such high rate of gas generation may exceed the capacity of venting if the venting is inefficient. This may lead to high pressure build-up and thereby, posing risk to integrity of the secondary cell and risk of cascading failures across the entire battery. This also poses an increased risk to the application in which the secondary battery is used. In other words, when the secondary battery is used in vehicles, such pressure build-up inside the secondary cell may risk the integrity of the vehicle.

[0020] Moreover, the arrangement of secondary cells within the battery can significantly impact the consequences of gas venting. In configurations where cells are stacked vertically, when the gas from the top secondary cell vents out, the components of the bottom secondary cell may be damaged by the top secondary cell due to the thrust of the gas with which the gasvents out. For instance, the bottom portion of the top secondary cell may hit and damage the bottom secondary cell or other components of the secondary battery, such as the battery casing. This may cause damage to the structural integrity of underlying secondary cells or the components of the secondary battery, such as the battery casing. Such damage can compromise the integrity of the secondary battery.

[0021] The present subject matter relates to a lid for a secondary cell. With the present subject matter, the vent can be opened without any hinderance cause and without any damage being caused to the components of the battery pack. Accordingly, the present subject matter enables safe, quick, and efficient venting of high-pressure gas and thereby, eliminating any damage caused to generation of the gas inside the secondary cells.

[0022] In an implementation of the present subject matter, a secondary battery may include a plurality of secondary cells that are electrically connected with each other. Hereinafter, secondary cell will be explained with reference to a single secondary cell. A secondary cell may include an electrode assembly. The secondary cell may be, for example, a cylindrical- type secondary cell. In an example, the secondary cell may be a cylindrical cell. In an example, the secondary cell may be a large format cylindrical cell, tab less cell, full tab cell, and the like. The secondary cell may be part of a secondary battery and may be used in applications, such as Electric Vehicles (EV), Hybrid Vehicles, and the like. The electrode assembly may include a first electrode, a second electrode, and a separator separating the first electrode and the second electrode. In an example, the electrode assembly may be a jelly-roll electrode assembly. Further, the secondary cell may include a shell to enclose components of the secondary cell, including the electrode assembly. The first electrode may be connected to a current collector at a first end of the secondary cell and the second electrode may be connected to a lid at a second end of the secondary cell.The first end may be opposite the second end. The lid may be attached to the shell.

[0023] In an example, the lid may include a top surface and a bottom surface. Further, the lid may include a venting portion. In an example, the lid may include a first portion, a second portion, and a third portion. The bottom surface may form a part of the first portion. The first portion may be connected with the shell. In an example, the first portion may be welded with the shell. The second portion may be contiguous with and extending radially inwards from the first portion. The second portion may be displaced axially at a distance from the first portion. The top surface forms a part of the second portion. The second portion of the lid may be connected (for example, welded) with the electrode assembly for the connection thereof. When the second portion of the lid is connected to the second electrode of the electrode assembly, a gap may be formed between the electrode assembly and the third portion of the lid. The gap may facilitate release of the gas from the secondary cell.

[0024] The third portion may be contiguous with and extending radially inwards from the second portion. The venting portion may be part of the third portion. The third portion may be located axially relative to the top surface and relative to the bottom surface. Accordingly, the venting portion may be located axially relative to the top surface and relative to the bottom surface without causing load of the lid acting through the venting portion and without causing the movement of the lid during release of the gas. The third portion may be axially displaced downwards at a second distance from the top portion and axially displaced upwards at a first distance from the bottom portion. In an example, an axial distance between the top surface and the bottom surface is greater than the first distance at which the third portion is axially upwards from the first portion.

[0025] In an example, the lid may be made of Aluminium, Nickel-plated steel, or a combination thereof. In an example, the lid may be made of stamping process. In an example, the venting portion may be of triangularcross-section. Further, the venting portion may be configured to form an opening to release a gas from an inside of the secondary cell. In particular, when the gas inside the secondary cell has a pressure greater than a threshold pressure, the vent may be configured to form an opening to release the gas.

[0026] The venting portion may be at a higher stress than other portions of the lid to enable detachment of the venting portion when the pressure of gas inside the secondary cell is greater than the threshold pressure. Therefore, the venting portion may form the opening when the pressure of gas inside the secondary cell is greater than the threshold pressure. In an example, to enable the higher stress of the venting portion in the lid, the venting portion may be embossed over other portions of the lid.

[0027] In an example, since the venting portion is part of the third portion, the bottom surface is part of the first portion, the venting portion may be located axially upwards at a first distance from the bottom surface. Similarly, since the venting portion is part of the third portion and the top surface is part of the second portion, the venting portion may be axially downwards at a second distance from the top surface. Accordingly, the location of the venting portion (i.e. , the third portion) may be such that load of the lid (and thereby, the load of the secondary cell) acting may not act through the venting portion before forming the opening. In other words, in an assembled position in the secondary battery, the secondary cell may rest on another secondary cell or a component of the secondary battery. In such a scenario, the load (i.e., weight) of the secondary cell may act through the lid. In particular, the load may act through the bottom surface (i.e., the first portion) and not through the venting portion (i.e., the third portion). Therefore, there is no hinderance caused to the venting portion to open. Further, the location of the venting portion is such that when the gas is released through the opening formed by the venting portion, there is no movement of the lid. In other words, since the venting portion is axially atthe first distance upwards from the bottom surface, the lid rests on another component (another secondary cell of the secondary battery or a casing of the secondary battery) through the bottom surface (i.e., through the first portion) and not through the venting portion (i.e., through the third portion). Therefore, when the gas is released through the opening formed by the venting portion, the thrust of the gas does not cause movement of the lid.

[0028] With the present subject matter, the vent can be opened without any hinderance caused. Accordingly, the present subject matter eliminates risk of partial or incomplete release of gas from inside the secondary cell. Therefore, the present subject matter prevents any damage caused to the secondary cell and to the adjacent secondary cells caused due to the partial venting of gas. In this regard, the present subject matter also prevents high pressure build-up caused due to the partial venting of gas and thereby, eliminates risk to integrity of the secondary cell and risk of cascading failures across the entire battery.

[0029] Further, with the present subject matter, any damage being caused to the components of the battery during the venting of the gas is eliminated. Accordingly, damage caused to the structural integrity of other secondary cells or other components of the battery is eliminated. Therefore, the present subject matter eliminates the risk of incomplete venting of gases while also preventing any damage caused to the other components of the battery. Therefore, the present subject matter provides a safeguard during sudden, high-pressure release of gas. The present subject matter enables safe, quick, and efficient venting of high-pressure gas.

[0030] The present subject matter not only addresses safety concerns but also enhances overall battery performance and longevity. For instance, by enabling safe, quick, and efficient venting of high-pressure gas, the present subject matter maintains optimal internal conditions within each secondary cell. This contributes to consistent battery performance, reduces the risk of premature cell degradation, and potentially extends the operational life of the entire battery system.

[0031] 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.

[0032] Fig. 1 a illustrates an exploded view of a secondary cell 100, in accordance with an implementation of the present subject matter. Fig. 1 b illustrates a sectional view of the secondary cell 100, in accordance with an implementation of the present subject matter. Fig. 1 c illustrates a perspective sectional view of the secondary cell 100, in accordance with an implementation of the present subject matter. Fig. 1 d illustrates a portion of perspective section view of the secondary cell 100, in accordance with an implementation of the present subject matter. For the sake of brevity, Figs. 1 a-1 d are explained in conjunction with each other.

[0033] The secondary cell 100 may include an electrode assembly 102. The secondary cell 100 may be, for example, a cylindrical-type secondary cell. In an example, the secondary cell 100 may be a large format cylindrical cell. The secondary cell 100 may be a tab less cell, a full tab cell, and the like. The secondary cell 100 may be part of a secondary battery and may be used in applications, such as Electric Vehicles (EV), Hybrid Vehicles, and the like.

[0034] Further, the secondary cell 100 may include a shell 101 to enclose components of the secondary cell 100. The secondary cell 100 may include an electrode assembly 102. The electrode assembly 102 mayinclude a first electrode (not shown in Figs. 1 a-1 d), a second electrode (not shown in Figs. 1 a-1d), and a separator (not shown in Figs. 1 a-1 d) separating the first electrode and the second electrode. In an example, the first electrode may be a positive electrode and the second electrode may be a negative electrode. Each of the first electrode, the second electrode may be provided in the form of a sheet. Further, the first electrode and the second electrode may be wound together with the separator so as to be formed in a jelly roll type. Here, as will be understood, the electrode assembly 102 may be wound, for example, in a cylindrical shape.

[0035] The electrode assembly 102 may include a current collector plate 104 and a lid 106. The current collector plate 104 and the lid 106 may facilitate connection of the electrodes with an external circuit, such as to terminals of the secondary battery. In this regard, the first electrode may be connected to the current collector plate 104. In particular, the first electrode may be connected through a first electrode tab portion.

[0036] Similarly, the second electrode may be connected to the lid 106. In particular, the second electrode may be connected through a second electrode tab portion. Further, the lid 106 may be connected to the shell 101. In an example, the lid 106 may be welded to the shell 101 and thereby, forming the negative terminal. The lid 106 may be welded to a second electrode tab of the second electrode and further welded to a lower circumference of the shell 101 so as to ensure proper sealing and structure closure. The welding may be, for example, laser welding, as will be explained later. In an example, the current collector plate 104 may be positioned near a top end 150-1 of the secondary cell 100 in the view depicted herein. The lid 106 may be positioned near a bottom end 150-2 of the secondary cell 100 in the view depicted herein.

[0037] Further, the secondary cell 100 may include a rivet 108. The rivet 108 may facilitate extraction of positive terminal to enable electrical connection of the secondary cell 100 at the secondary battery level. The rivet 108 may be insertable through an opening 112 on the shell 101provided at the top end 150-1 of the secondary cell 100. Further, the secondary cell 100 may also include a rivet sealing member 110 to seal the opening 112. The rivet 108 may be welded to the central portion of a central portion of the current collector plate 104 to take out the terminal connections. In an example, the shell 101 , the rivet sealing member 110, and the rivet 108 may be provided as a single component.

[0038] Further, the secondary cell 100 may include a closing pin 114 and a lid sealing member 116 provided at the bottom end 150-2. The lid sealing member 116 may provide a sealing to an opening 130 at the bottom end 150-2 to prevent electrolyte egressing the electrode assembly 102. To prevent any short circuiting between positive terminal and negative terminal of the secondary cell 100, the secondary cell 100 may include an insulator 111 provided between the rivet 108 and the shell 101. The insulator 111 and the rivet sealing member 110 may avoid the connection of the current collector plate 104 with the shell 101 .

[0039] In an example, during operation, the secondary cell 100 may generate high-pressure gas. Particularly, the gas may have to be vented out of the secondary cell 100 to prevent thermal damage of the secondary cell 100. In this regard, the lid 106 may be designed so as to enable venting of the gas when the pressure of the gas exceeds a threshold pressure, as will be explained below.

[0040] Fig. 2a illustrates a bottom perspective view of the lid 106 of the secondary cell 100, in accordance with an implementation of the present subject matter. Fig. 2b illustrates a top perspective sectional view of the lid 106 of the secondary cell 100, in accordance with an implementation of the present subject matter. For the sake of brevity, Figs. 2a and 2b are explained in conjunction with each other. The lid 106 may be, for example, a circular disc. The lid 106 may include a central portion 210 forming a central part of the lid 106. The central portion 210 may be adapted to be received into the opening 130 (not shown in Figs. 2a-2b) at a bottom end of the electrode assembly 102. In an example, the lid 106 may be co-axial withthe electrode assembly 102. In particular, the central portion 210 may be co-axial with the central portion of the electrode assembly 102. The central portion 210 of the lid 106 defines an aperture 212 which is adapted to facilitate entry of electrolyte into the electrode assembly 102 of the secondary cell 100. Further, the aperture 212 of the central portion 210 is adapted to the closing pin 114 and the lid sealing member 116.

[0041] The lid 106 may include a first portion 202, a second portion 204, and a third portion 206. The first portion 202, the second portion 204, and the third portion 206 may be contiguous with each other. The first portion 202 may extend inwards along radial direction ‘R’. Hereinafter, ‘inwards’ and ‘outwards’ along the radial direction ‘R’ will be referred to as radially inwards and radially outwards respectively. In particular, the first portion 202 may extend radially inwards towards the central portion 210. The second portion 204 may be contiguous with the first portion 202 and may extend radially inwards from the first portion 202. Particularly, the second portion 204 may extend radially inwards towards the central portion 210. Similarly, the third portion 206 may be contiguous with the second portion 204 and may extend radially inwards from the second portion 204 and towards the central portion 210.

[0042] In an example, the first portion 202, the second portion 204, and the third portion 206 may be at different dimensions along an axial direction ‘A’. In other words, the first portion 202 may be at one height along the axial direction ‘A’, the second portion 204 may be at another height along the axial direction ‘A’, and the third portion 206 may be at yet another height along the axial direction ‘A’.

[0043] The lid 106 may include a top surface 214 which may be part of the second portion 204. The top surface 214 may be at a first height along the axial direction ‘A’. Further, the lid 106 may include a venting portion 208, which may be part of the third portion 206. The venting portion 208 may form an opening to release the gas from inside the secondary cell 100. In particular, the venting portion 208 may form the opening when pressure ofthe gas inside the secondary cell 100 is greater than a threshold pressure. For instance, the venting portion 208 may be configured to detach from the lid 106 when a pressure inside the secondary cell 100 is greater than a threshold pressure. Accordingly, a part of the third portion 206 may detach from the lid 106 causing formation of the opening in the lid 106 (i.e., in the third portion 206 of the lid 106). The opening may enable venting of gas from the secondary cell 100. In an example, the venting portion 208 may be, for example, of triangular shaped cross-section. The venting portion 208 may have a higher stress compared to other portions of the lid 106. This is to facilitate the venting portion 208 to fail due to higher stress to cause the detachment and form the opening to release the gas when the pressure of the gas is greater than the threshold pressure. The venting portion 208 may have a predetermined thickness to allow the detachment of the venting portion 208 from the third portion 206. In an example, the threshold pressure may be 10 Bar to 30 Bar.

[0044] In an example, the lid 106 may be formed using stamping process. The venting portion 208 may be embossed over other portions of the lid 106. In other words, the venting portion 208 may be formed using embossing with a higher stress than other portions of the lid 106 and may form an integrated part of the third portion 206. The higher stress may ensure that the venting portion 208 is the weakest portion compared to other portions of the lid 106. The lid 106 may be, for example, made using Nickel- plated steel, Aluminium, or a combination thereof. However, in other examples, the lid 106 may be made of any other battery-grade material.

[0045] Fig. 2c illustrates a bottom perspective view of the lid 106 of the secondary cell 100, in accordance with an implementation of the present subject matter. Fig. 2d illustrates a bottom perspective sectional view of the lid 106 of the secondary cell 100, in accordance with an implementation of the present subject matter. For the sake of brevity, Figs. 2c and 2d are explained in conjunction with each other. The lid 106 may include a bottom surface 220 that is part of the first portion 202. As can be seen in Figs. 2cand 2d, the positioning of the first portion 202, the second portion 204, and the third portion 206 along the axial direction ‘A’ may be different. In particular, the first portion 202 may form lowermost portion of the lid 106 along the axial direction ‘A’. The second portion 204 may form the top most portion of the lid 106 along the axial direction ‘A’. The third portion 206 may form the middle portion of the lid 106 along the axial direction ‘A’. Accordingly, when the lid 106 rests on another component, such as another secondary cell 100 or casing of the secondary battery, the lid 106 may rest through the bottom surface 220, which is the part of the first portion 202. However, the other portions of the lid 106, such as the second portion 204 and the third portion 206, may not be in contact with other component when the lid 106 rests on another component.

[0046] Fig. 2e illustrates a sectional view of a portion of the secondary cell 100, in accordance with an implementation of the present subject matter. Fig. 2f illustrates an enlarged view of a portion of the view of the secondary cell 100 illustrated in Fig. 2e, in accordance with an implementation of the present subject matter. For the sake of brevity, Figs. 2e and 2f are explained in conjunction with each other.

[0047] The first portion 202 may extend radially inwards towards the central portion 210 for a first predetermined distance. The second portion 204 may extend radially inwards from the first portion 202 towards the central portion 210 for a second predetermined distance. The third portion 206 may extend radially inwards towards the central portion 210 for a third predetermined distance. In other words, the first portion 202 may have a first predetermined diameter. The first predetermined diameter may be chosen so as to correspond to the circumference of the shell 101. The second portion 204 may have a second predetermined diameter. The third portion 206 may have a third predetermined diameter.

[0048] As mentioned earlier, the first portion 202, the second portion 204, and the third portion 206 of the lid 106 may be at different positions along the axial direction ‘A’. The first portion 202 may form the bottom mostpart of the lid 106. Accordingly, when the lid 106 rests on another component, the lid 106 may rest through the first portion 202. The second portion 204 may be displaced axially at a distance from the first portion 202. The second portion 204 may form the top most portion of the lid 106. The third portion 206 may be at a middle position to the first portion 202 and the second portion 204 along the axial direction ‘A. The displacement along the axial direction ‘A’ upwards and downwards will be referred to as axially upwards and axially downwards respectively. In other words, the third portion 206 may be axially displaced downwards at a second distance from the top portion and axially displaced upwards at a first distance from the bottom portion. Since the venting portion 208 is part of the third portion 206, the top surface 214 is part of the second portion 204, and the bottom surface 220 is part of the first portion 202, the venting portion 208 is axially displaced downwards at a second distance from the top surface 214 and axially displaced upwards at a first distance from the bottom surface 220. In other words, the venting portion 208 is at a different plane along the axial direction when compared with the top surface 214 and the bottom surface 220. For instance, the bottom surface 220 may be at a first plane along the axial direction, the venting portion 208 may be at a second plane along the axial direction, and the top surface 214 may be at a third plane along the axial direction. The first plane, the second plane, and the third plane may be in the increasing order of distance along the axial direction.

[0049] As mentioned earlier, the lid 106 may be connected to the shell 101 as well as the electrode assembly 102. The lid 106 may be connected to the shell 101 on a circumference of the lid 106. In this regard, the lid 106 may be connected to the shell 101 through the first portion 202. In particular, the first portion 202 may include a top end. The shell 101 may include a bottom end. The top end of the first portion 202 and the bottom end of the shell 101 may be coupled and attached together to form an assembly of the shell 101 and the lid 106. In an example, the shell 101 and the lid 106 maybe attached using welding, such as laser welding. Therefore, the lid 106 may form the bottom portion of the secondary cell 100.

[0050] Further, the lid 106 may be connected to the second electrode through the second electrode tab portion. In particular, the lid 106 may connected to the second electrode tab portion through the second portion 204. The connection of the lid 106 and the second electrode tab may be, for example, performed by welding. In an example, the welding may be laser welding. Since the venting portion 208 is part of the third portion 206 and the third portion 206 is axially displaced downwards from the second portion 204, a gap 240 would be formed between the third portion 206 and the electrode assembly 102 when the second portion 204 is welded with the electrode assembly 102. This gap 240 would enable venting of gases, as will be explained later. In an example, the location of the third portion 206 is such that the venting portion 208 forms the gap 240 on an upper side of the third portion 206 to cause appropriate amount of accumulation of gas in the gap 240 and thereby, causing sufficient thrust of the gas for causing the release of the gas without causing damage to the secondary cell 100. Further, the location of the third portion 206 is such that there is no hinderance caused for detachment of the venting portion 208 when the pressure of the gas is higher than a threshold pressure. Further, in an example, the position of the third portion 206 is such that the distance H1 between the top surface 214 and the bottom surface 220 along the axial direction is greater than the distance H2 at which the third portion 206 is axially upwards from the first portion 202. In an example, the distance H2 may be for example, in the range of 0.5 mm to 2.0 mm.

[0051] During operation, when there is a pressure build-up inside the secondary cell 100, the gas may flow and accumulate in the gap 240. The path of the gas is depicted by the arrow 250. When the pressure of the gas is greater than the threshold pressure, the gas accumulated in the gap 240 may look for a weaker region for escaping. Since the venting portion 208 is the weakest portion of the lid 106 among other portions of the lid 106, thegas may try to escape through the venting portion 208. In this regard, due to the pressure of the gas, the venting portion 208 may detach from the lid 106 and may form the opening. The gas may escape through the opening formed by the venting portion 208. Additionally, as the third portion 206 has clearance relative to the bottom surface 220, there is no hindrance for the venting portion 208 to open. This clearance helps in safe guarding the adjacent secondary cells and the secondary battery or any components of the secondary battery from damage from the thrust of the gases and opening of the venting portion 208.

[0052] The location of the venting portion 208 (i.e., the third portion 206) may be such that load of the lid 106 (and thereby, the load of the secondary cell 100) acting may not act through the venting portion 208. In other words, in an assembled position in the secondary battery, the secondary cell 100 may rest on another secondary cell 100 or a component of the secondary battery. In such a scenario, the load (i.e., weight) of the secondary cell 100 may act through the lid 106. In particular, the load may act through the bottom surface 220 (i.e., the first portion 202) and not through the venting portion 208 (i.e., the third portion 206). Therefore, there is no hinderance caused to the venting portion 208 to open. That is, when the venting portion 208 detaches from the lid 106, there is no hinderance caused to the venting portion 208 due to the positioning of the venting portion 208, as explained earlier. Further, the positioning of the venting portion 208 is such that when the gas is released through the opening formed by the venting portion 208, there is no movement of the lid 106. In other words, since the venting portion 208 is axially at the first distance upwards from the bottom surface 220, the lid 106 rests on another component (another secondary cell 100 of the secondary battery or a casing of the secondary battery) through the bottom surface 220 (i.e., through the first portion 202) and not through the venting portion 208 (i.e., through the third portion 206). Therefore, when the gas is released through the opening formed by the venting portion 208, the thrust of the gas does not causemovement of the lid 106. Accordingly, there is no damage caused by the lid 106 to other components of the battery.

[0053] Fig. 3 illustrates a secondary battery 300, in accordance with an implementation of the present subject matter. The secondary battery 300 may be used in applications, such as Electric Vehicles (EV), Hybrid Vehicles, and the like. The secondary battery 300 may include a plurality of secondary cells, such as a first secondary cell 302-1 , a second secondary cell 302-2, ... , and Nth secondary cell 302-N. The secondary cells may be collectively referred to as secondary cell 302. Each of the secondary cells 302 may correspond to the secondary cell 100. The secondary cell 100 may be, for example, a cylindrical-type secondary cell. In an example, the secondary cell 100 may be a large format cylindrical cell. The secondary cell 100 may be a tab less cell, a full tab cell, and the like.Each secondary cell 302 may include an electrode assembly. The electrode assembly may correspond to the electrode assembly 102. The electrode assembly may include a first electrode, a second electrode, and a separator. The separator may be positioned between the first electrode and the second electrode. Each secondary cell 302 may include a current collector plate, a shell, and a lid. The current collector plate may be connected to the first electrode and may correspond to the current collector plate 104. The shell may enclose components of the secondary cell 302. The shell may correspond to the shell 101. The lid may be connected to the second electrode and to the shell. The lid may correspond to the lid 106, as explained with reference to Figs. 2a-2f.

[0054] The lid may include a first portion, a second portion, and a third portion. The first portion may correspond to the first portion 202, the second portion may correspond to the second portion 204, and the third portion may correspond to the third portion 206. The first portion may include a bottom surface. The second portion may be contiguous with and may extend radially inwards from the first portion. The second portion may be displaced axially at a distance from the first portion. The second portion may includea top surface. The third portion may be contiguous with and may extend radially inwards from the second portion. The third portion may be axially displaced downwards at a second distance from the top portion and axially displaced upwards at a first distance from the bottom portion. The lid may include a venting portion that is disposed in the third portion without causing load of the lid acting through the venting portion and without causing movement of the lid during the release of the gas. The venting portion may be configured to form an opening when pressure of gas inside the secondary cell 302 is greater than a threshold pressure to release the gas from the secondary cell 302. The venting portion may correspond to the venting portion 208. The structure, working, and other aspects of the each of the secondary cell 302 are explained with reference to Figs. 1 a- 2f.

[0055] With the present subject matter, the vent can be opened without any hinderance caused. Accordingly, the present subject matter eliminates risk of partial or incomplete release of gas from inside the secondary cell. Therefore, the present subject matter prevents any damage caused to the secondary cell and to the adjacent secondary cells caused due to the partial venting of gas. In this regard, the present subject matter also prevents high pressure build-up caused due to the partial venting of gas and thereby, eliminates risk to integrity of the secondary cell and risk of cascading failures across the entire battery.

[0056] Further, with the present subject matter, any damage being caused to the components of the battery during the venting of the gas is eliminated. Accordingly, damage caused to the structural integrity of other secondary cells or other components of the battery is eliminated. Therefore, the present subject matter eliminates the risk of incomplete venting of gases while also preventing any damage caused to the other components of the battery. Therefore, the present subject matter provides a safeguard during sudden, high-pressure release of gas. The present subject matter enables safe, quick, and efficient venting of high-pressure gas.

[0057] Although the present subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter.

Claims

1 / We Claim:1 . A lid (106) for a secondary cell (100, 302), the lid (106) comprising: a top surface (214); a bottom surface (220); a venting portion (208) configured to form an opening when pressure of gas inside the secondary cell (100, 302) is greater than a threshold pressure to release the gas from the secondary cell (100, 302), wherein the venting portion (208) is located axially relative to the top surface (214) and relative to the bottom surface (220) without causing load of the lid (106) acting through the venting portion (208) and without causing movement of the lid (106) during the release of the gas.

2. The lid (106) as claimed in claim 1 , wherein the venting portion (208) is located axially upwards at a first distance from the bottom surface (220) and axially downwards at a second distance from the top surface (214).

3. The lid (106) as claimed in claim 1 , comprising: a first portion (202), the bottom surface (220) forming a part of the first portion (202); a second portion (204) being displaced axially at a distance from the first portion (202), wherein the top surface (214) forms a part of a second portion (204); and a third portion (206) being axially displaced downwards at a second distance from the top portion and axially displaced upwards at a first distance from the bottom portion, the venting portion (208) being part of the third portion (206).

4. The lid (106) as claimed in claim 3, wherein: the second portion (204) is contiguous with and extends radially inwards from the first portion (202), andthe third portion (206) is contiguous with and extends radially inwards from the second portion (204).

5. The lid (106) as claimed in claim 3, wherein an axial distance between the top surface (214) and the bottom surface (220) is greater than the first distance at which the third portion (206) is axially upwards from the first portion (202).

6. The lid (106) as claimed in claim 1 , wherein the venting portion (208) is at a higher stress than other portions of the lid (106) to enable detachment of the venting portion (208) when the pressure of gas inside the secondary cell (100, 302) is greater than the threshold pressure.

7. The lid (106) as claimed in claim 1 , wherein the venting portion (208) of triangular cross-section.

8. The lid (106) as claimed in claim 1 , wherein the lid (106) is made of Aluminium, Nickel-plated steel, or a combination thereof.

9. The lid (106) as claimed in claim 1 , wherein the lid (106) is made of stamping process.

10. The lid (106) as claimed in claim 1 , wherein the venting portion (208) is embossed over other portions of the lid (106).

11. A secondary cell (100, 302) comprising: an electrode assembly (102) comprising: a first electrode and a second electrode, wherein a separator is positioned between the first electrode and the second electrode; a current collector plate (104) connected to the first electrode; a shell (101 ) to enclose components of the secondary cell (100, 302); a lid (106) connected to the second electrode and to the shell (101 ), wherein the lid (106) comprises:a top surface (214); a bottom surface (220); and a venting portion (208) configured to form an opening when pressure of gas inside the secondary cell (100, 302) is greater than a threshold pressure to release the gas from the secondary cell (100, 302), wherein the venting portion (208) is located axially upwards at a first distance from the bottom surface (220) and axially downwards at a second distance from the top surface (214) without causing load of the lid (106) acting through the venting portion (208) and without causing movement of the lid (106) during the release of the gas.

12. The secondary cell (100, 302) as claimed in claim 11 , wherein the lid (106) comprises: a first portion (202), the bottom surface (220) forming a part of the first portion (202); a second portion (204), the second portion (204) being contiguous with and extending radially inwards from the first portion (202), the second portion (204) being displaced axially at a distance from the first portion (202), wherein the top surface (214) forms a part of a second portion (204); and a third portion (206) contiguous with and extending radially inwards from the second portion (204), the venting portion (208) being part of the third portion (206), wherein the third portion (206) is axially displaced downwards at a distance from the top portion and axially displaced upwards at a distance from the bottom portion.

13. The secondary cell (100, 302) as claimed in claim 12, wherein an axial distance between the top surface (214) and the bottom surface (220) is greater than the first distance at which the third portion (206) is axially upwards from the first portion (202).

14. The secondary cell (100, 302) as claimed in claim 12, wherein the first portion (202) of the lid (106) is connected with the shell (101 ).

15. The secondary cell (100, 302) as claimed in claim 12, wherein the first portion (202) of the lid (106) is welded with the shell (101 ).

16. The secondary cell (100, 302) as claimed in claim 12, the second portion (204) of the lid (106) is welded with the electrode assembly (102) for the connection thereof.

17. The secondary cell (100, 302) as claimed in claim 12, a gap (240) is formed between the electrode assembly (102) and the third portion (206) of the lid (106) when the second portion (204) of the lid (106) is connected to the second electrode of the electrode assembly (102), wherein the gap (240) is to facilitate the release of the gas from the secondary cell (100, 302).

18. The secondary cell (100, 302) as claimed in claim 12, the venting portion (208) is to detach from the third portion (206) to form the opening when the pressure of the gas is greater than the threshold pressure.

19. The secondary cell (100, 302) as claimed in claim 11 , wherein the venting portion (208) is of triangular cross-section.

20. The secondary cell (100, 302) as claimed in claim 11 , wherein the lid (106) is made of Aluminium, Nickel-plated steel, or combination thereof.21 . The secondary cell (100, 302) as claimed in claim 11 , wherein the lid (106) is made by stamping and wherein the venting portion (208) is embossed with other portions of the lid (106).

22. The secondary cell (100, 302) as claimed in claim 11 , wherein the lid (106) comprises a central portion (210) with an aperture (212) that is to be received into an opening (130) in the electrode assembly (102) to facilitate entry of electrolyte in the electrode assembly (102).

23. The secondary cell (100, 302) as claimed in claim 11 , wherein the secondary cell (100, 302) is a cylindrical-type cell.

24. The secondary cell (100, 302) as claimed in claim 11 , wherein the electrode assembly (102) is a jelly-roll electrode assembly (102).

25. A secondary battery (300) comprising: a plurality of secondary cells (302) electrically connected with each other, wherein each secondary cell (100, 302) comprises: an electrode assembly (102) comprising: a first electrode and a second electrode, wherein a separator is positioned between the first electrode and the second electrode; a current collector plate (104) connected to the first electrode; a shell (101 ) to enclose components of the secondary cell (100, 302); a lid (106) connected to the second electrode and to the shell (101 ), wherein the lid (106) comprises: a first portion (202) comprising a bottom surface (220); a second portion (204) being contiguous with and extending radially inwards from the first portion (202), the second portion (204) being displaced axially at a distance from the first portion (202), wherein the second portion (204) comprises a top surface (214); and a third portion (206) contiguous with and extending radially inwards from the second portion (204), wherein the third portion (206) is axially displaced downwards at a second distance from the top portion and axially displaced upwards at a firstdistance from the bottom portion, wherein a venting portion (208) is disposed in the third portion (206) without causing load of the lid (106) acting through the venting portion (208) and without causing movement of the lid (106) during release of gas, and wherein the venting portion (208) is configured to form an opening when pressure of gas inside the secondary cell (100, 302) is greater than a threshold pressure to release the gas from the secondary cell (100, 302).

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