Sealing assembly for a battery cell

Abstract

A sealing assembly for a battery cell includes a grommet having an opening with an inner surface. A peg has a peg head and a shaft extending from the peg head. The shaft includes a first portion having a larger diameter and a second portion having a smaller diameter, and the shaft extends through the opening in the grommet. The shaft and the grommet form a first interference fit at a distal end of the opening. A trap gap is formed between the distal end of the opening and the peg head. The trap gap defines a trap for a sealant. A sealant is disposed on the shaft and at least partially in the trap.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a sealing assembly for a battery cell, and more particularly to a sealing assembly configured to reduce leakage of electrolyte from the interior of a battery cell. BACKGROUND

[0002] Consumer electronic devices have certain power requirements. Typically, consumer electronic devices receive power from a single battery cell housed within the device itself or from a portable battery pack that can include one or more battery cells. Alternatively, one or more single-use or rechargeable consumer battery cells can be used in the device as needed and replaced. Rechargeable and replaceable consumer battery cells generate electricity through the reduction of a cathode and oxidation of an anode. Alkaline electrolyte is typically used to facilitate the movement of ions from the anode to the cathode.

[0003] Alkaline battery cells, including rechargeable alkaline battery cells, are known to be susceptible to leakage of alkaline electrolyte from the battery seal. See For example, Hull et al., “Why Alkaline Cells Leak,” J. Electrochem. Soc., 124(3): 332-339, (1977) and Davis et al., “Aspects of Alkaline Cell Leakage,” J. Electrochem. Soc., 125(12): 1918-123 (1978). Evidence of alkaline electrolyte leakage can be visually detected as a white powder deposits around the battery cell seal. Alkaline electrolyte leakage can be attributed to the creepage of alkaline electrolyte along the negative polarized electrode. Alkaline electrolyte leakage can be exacerbated by physical factors such as a scratch or other physical deformation / defect in the seal of the battery cell. Although powdered alkaline electrolyte is generally safe for human contact, contact should be minimized as respiratory, eye, and skin irritation can occur. Furthermore, loss of electrolyte can result in battery performance degradation. SUMMARY

[0004] According to one embodiment, a sealing assembly for a battery cell includes a grommet having an opening with an inner surface, the opening having a proximal end and a distal end. A peg has a peg head and a shaft extending from the peg head. The shaft includes a first portion having a first shaft diameter that is larger and a second portion having a second shaft diameter that is smaller, and the shaft extends through the opening in the grommet. The shaft and the grommet form a first interference fit at the distal end of the opening. A trap gap is formed between the distal end of the opening and the proximal end of the opening. The trap gap is radially and longitudinally between the second portion of the peg and the inner surface, and the trap gap defines a trap for a sealant. The sealant is disposed on the shaft and at least partially in the trap.

[0005] According to another embodiment, a battery cell includes a housing. The housing has a first cover at a first housing end and a second cover at a second housing end. An anode and a cathode are disposed within the housing. A seal assembly is located proximate the first cover. The seal assembly includes a grommet having an opening and an inner surface. A peg has a peg head and a shaft extending from the peg head. The shaft includes a first portion having a first, larger diameter and a second portion having a second, smaller diameter, and the shaft extends through the opening in the grommet. The shaft and the grommet form a first interference fit at a distal end of the opening. A trap gap is formed between the distal end of the opening and the peg head. The trap gap is located radially and longitudinally between the second portion of the peg and the inner surface, and the trap gap defines a trap for a sealant. The sealant is disposed on the shaft and the sealant is at least partially located in the trap.

[0006] According to another embodiment, a seal assembly for a battery cell includes a grommet having an opening including a distal end, a proximal end, and a bore between the distal end and the proximal end. An inner annular ring is positioned proximate the distal end, the inner annular ring having a ring diameter. The bore has a bore diameter. A headspace is located at the proximal end and the headspace has a headspace diameter. The ring diameter is less than the bore diameter and the headspace diameter, and the bore diameter is less than the headspace diameter. A peg has a peg head and a shaft extending from the peg head. The shaft includes a first portion having a first shaft diameter and a second portion having a second shaft diameter. The first shaft diameter is greater than the second shaft diameter. The shaft extends through the opening in the grommet. The shaft and the grommet form a first interference fit between the second portion of the shaft and the ring diameter. The shaft and the grommet form a trap gap between the second portion of the shaft and the bore diameter, the trap gap defining a trap for a sealant. The sealant is disposed on the shaft and at least partially located in the trap.

[0007] According to another embodiment, a battery cell includes a housing having a first cover at a first housing end and a second cover at a second housing end, and an anode and a cathode disposed within the housing. A seal assembly is located proximate the first cover. The seal assembly includes a grommet having an opening including a distal end, a proximal end, and a bore between the distal end and the proximal end. An inner annular ring is positioned proximate the distal end, the inner annular ring having a ring diameter. The bore has a bore diameter. A headspace is located at the proximal end and the headspace has a headspace diameter. The ring diameter is less than the bore diameter and the headspace diameter, and the bore diameter is less than the headspace diameter. A staple has a staple head and a shaft extending from the staple head. The shaft includes a first portion having a first shaft diameter and a second portion having a second shaft diameter. The first shaft diameter is greater than the second shaft diameter. The shaft extends through the opening in the grommet. The shaft and the grommet form a first interference fit between the second portion of the shaft and the ring diameter. The shaft and the grommet form a trap gap between the second portion of the shaft and the bore diameter, the trap gap defining a trap for a sealant. The sealant is disposed on the shaft and at least partially located in the trap.

[0008] The foregoing embodiments of the seal assembly or battery cell can also include any one or more of the following optional features, structures, and / or forms.

[0009] In some optional forms, the second portion is distal to the head with respect to the first portion.

[0010] In other optional forms, the first portion and the second portion are joined by a chamfer.

[0011] In other optional forms, the inner surface of the opening includes a bore having a bore diameter that is greater than the second shaft diameter and less than the first shaft diameter, at least some of the second shaft diameter being within the bore diameter such that there is no interference fit between the second shaft diameter and the bore diameter when the staple is assembled in the grommet.

[0012] In other optional forms, the trap is formed in the assembled battery cell between the bore and the second portion of the shaft, the bore diameter being greater than the second shaft diameter.

[0013] In other optional forms, the bore diameter is between 0.03 mm and 0.05 mm greater than the second shaft diameter.

[0014] In other optional forms, the grommet opening includes an inner annular ring.

[0015] In other optional forms, the inner annular ring has a ring diameter that is less than the bore, and the inner annular ring forms the first interference fit with the second portion of the shaft.

[0016] In other optional forms, the trap is located above the inner annular ring along a length of the shaft.

[0017] In other optional forms, the volume of the trap is between 0.35 mm 3 and 1.5 mm 3 .

[0018] In other optional forms, the stem includes an annular recess.

[0019] In other optional forms, the trap gap is formed by the annular recess.

[0020] In other optional forms, the stem includes a plurality of annular recesses.

[0021] In other optional forms, the grommet comprises a polymer, such as polypropylene or nylon.

[0022] In other optional forms, the peg comprises a metal, such as brass or bronze.

[0023] In other optional forms, the sealant comprises a polymer, such as a polyamide or a petroleum-based material, such as an asphalt-based material.

[0024] In other optional forms, a head gap is formed between the peg head and the grommet, and the sealant is also disposed in the head gap. BRIEF DESCRIPTION OF DRAWINGS

[0025] While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the application, it is believed the application will be better understood from the following description when read in connection with the accompanying drawings.

[0026] FIG. 1 is a cross-sectional view of a prior art battery cell.

[0027] Figure 2 is a cross-sectional view of a battery cell including a trapped sealant seal assembly according to the present disclosure.

[0028] Figure 3 is an unassembled exploded cross-sectional view of the trapped sealant seal assembly of Figure 2

[0029] Figure 4 is a cross-sectional view of the seal assembly of Figure 3 in an assembled state.

[0030] Figure 5 is a cross-sectional view of an alternative embodiment of a trapped sealant seal assembly.

[0031] Figure 6 is a cross-sectional view of an alternative embodiment of a seal assembly according to the present disclosure.

[0032] Figure 7 ​It is a graphical representation of leakage test data of the sealing assembly according to this disclosure, including the first sealant.

[0033] Figure 8 It is a graphical representation of leakage data of the sealing assembly according to this disclosure, including the second sealant. Detailed Implementation

[0034] An electrochemical unit or battery can be a primary battery or a secondary battery. A primary battery is one that is discharged only once. For example Use until depleted, then discard. A primary battery (or disposable battery) is described, for example, by David Linden. Handbook of Batteries (4 th (ed. 2011), which is incorporated herein by reference. Secondary batteries (or rechargeable batteries) are designed for repeated charging and use. Secondary batteries can be discharged and charged many times, for example, more than fifty times, one hundred times, or more. Secondary batteries are described, for example, by David Linden. Handbook of Batteries (4 th (ed. 2011), which is also incorporated herein by reference. Therefore, batteries can include a variety of electrochemical couples and electrolyte combinations. The descriptions and examples provided herein apply to primary and secondary batteries in aqueous, non-aqueous, ionic liquid, and solid-state systems. While single-use consumer alkaline batteries are the primary focus of the accompanying description, the following description is equally applicable to any battery cell, including but not limited to rechargeable alkaline battery cells, such as rechargeable alkaline manganese (RAM) battery cells, and any other type of battery that includes an electrolyte solution.

[0035] The sealing assembly according to this disclosure can be included in any type of electrochemical cell. For example, the sealing assembly according to this disclosure can be used in consumer alkaline electrochemical cells of any size and / or shape (including, for example, cells having a cylindrical, rectangular or square shape or cross-sectional shape), including but not limited to AAAA cells, AAA cells, AA cells, B cells, C cells, D cells, 9V cells, etc.

[0036] Turning now to FIG. 1, one example of a conventional alkaline battery cell 10 is shown. The battery cell 10 includes first and second covers 12 and 14 corresponding to the negative and positive battery terminals, respectively, with a housing 16 generally disposed between the first and second covers. To separate the anode 18 from the cathode 20, the battery cell 10 includes a separator 22. To close the end 24 after the components of the battery cell 10 are disposed within the housing 16, the first cover 12 is received within a groove 26 of a grommet or seal 28 disposed proximate to the distal end 15 of the housing 16, and the sidewall 29 of the housing 16 is crimped over the peripheral edge of the seal 28. In some examples, the seal 28 is spaced from the cathode 20 to enable expansion of the cathode 20. In some examples, the seal 28 is similarly spaced from the anode 18 to enable expansion of the anode 18.

[0037] To couple the anode current collector 30 and the first cover 12 (which provides the negative terminal in the assembled battery cell 10), in this example, the seal 28 includes a first opening 32 having a wider portion 34 defining a head gap or space 36, with an end or head 38 of the anode current collector 30 (sometimes referred to as a “pin”) positioned at the first cover 12 and electrically coupled to the first cover. This space 36 can have a chamfered or angled configuration to accommodate the head 38. In this example, a body 40 of the anode current collector 30 extends through the first opening 32 and into the anode 18. An electrolyte solution is contained within the housing 16.

[0038] The seal 28 of FIG. 1 includes a cylindrical portion or boss 33 around the first opening 32. The boss 33 extends downward from a planar sealing portion or shelf 35 that extends laterally outward from the boss 33. The boss 33 of FIG. 1 is referred to herein as a short boss. The short boss extends below or above the shelf 35, but not both.

[0039] As noted above, battery cells are susceptible to electrolyte leakage, for example, due to seepage of electrolyte along the body of the anode current collector 30, such that electrolyte can escape from the first opening 32 in the seal 28. Previous attempts to prevent leakage have been made by providing a sealant around the pin in the opening 32, with the result that the sealant is “squeezed out” or wiped away during assembly (by interference fit with the seal 28), and thus ultimately disposed in the space 36 around the head 38. However, the sealant can not be uniformly provided around the head, and thus can not provide a uniform seal and / or can be displaced from the space 36 due to electrolyte seepage. Furthermore, such existing arrangements are more prone to leakage due to imperfections that can be introduced during manufacturing.

[0040] For example, the distal end of the anode current collector 30 (e.g., the bottom end in FIG. 1) can have burrs or flash that, due to the interference fit provided between these components, can scratch the inner surface of the first opening 32 during assembly. More specifically, when the anode current collector 30 is pushed down through the first opening 32 during assembly, any protruding surfaces of the anode current collector 30 can scrape the sides of the first opening 32 of the seal 28. As a result, defects can be formed in the inner surface of the first opening 32. As described above, these defects can facilitate the migration of electrolyte up through the first opening 32 and thus, leakage.

[0041] The disclosed seal 28 can be formed by a variety of manufacturing techniques, molding processes. In particular, injection molding and blow molding that use pins to create the voids are particularly advantageous. Defects can be formed during the injection molding and blow molding of the seal 28 that are similar to the defects described above with respect to the anode current collector because the pins used in the injection molding and blow molding can also have defects, such as burrs and flash. Typically, the seal 28 is formed by injection molding and a pin is used during the molding process to create the void that forms the first opening 32 of the seal 28. The distal end of this injection molding pin is ground and thus, often has burrs or flash that can also cause scratches to be formed during manufacturing. For example, when the pin is withdrawn from the first opening 32 after the molding process is complete, any defects in the pin can scratch the inner surface of the seal 28 as the pin is withdrawn, similar to the anode current collector 30 scratching the inner surface, as described above with respect to the insertion of the peg into the seal assembly.

[0042] When the sealant is applied to the anode current collector 30 of FIG. 1, during assembly, as the anode current collector is inserted into the first opening 32 by the interference fit between the anode current collector 30 and the first opening 32, the sealant is wiped along the axis of the anode current collector 30, causing the sealant to collect at the top of the anode current collector 30 near the head 38. Electrolyte from the interior of the housing 16 can migrate up the body 40 of the current collector 30 toward the head 38, particularly along the path of any defects introduced into the seal 28 during the manufacturing process as described above. Any sealant deposited at the top of the anode current collector 30 near the head 38 can be overcome by the electrolyte leakage of the anode current collector. As a result, electrolyte leakage can be formed.

[0043] Turning now to Figure 2FIG. 1 shows one example of a battery cell 110 having a seal assembly with a trapped sealant. The battery cell 110 includes a first cover 112 and a second cover 114 corresponding to a negative battery terminal and a positive battery terminal, respectively, with a housing 116 generally disposed between the first and second covers. To separate an anode 118 from a cathode 120, the battery cell 110 includes a separator 122.

[0044] The cathode 120 can include any known electrochemically active cathode material, including but not limited to manganese oxides, manganese dioxide, electrolytic manganese dioxide (EMD), chemical manganese dioxide (CMD), high power electrolytic manganese dioxide (HP EMD), lambda manganese dioxide, gamma manganese dioxide, beta manganese dioxide, and mixtures thereof. Other electrochemically active cathode materials include, but are not limited to, silver oxides; nickel oxides; nickel oxyhydroxide; copper oxides; copper salts such as copper iodate; bismuth oxides; high valence nickel compounds; high valence iron compounds; and mixtures thereof. Nickel oxides can include nickel hydroxide, nickel oxyhydroxide, nickel oxyhydroxide coated with cobalt oxyhydroxide, partially delithiated layered nickel oxide, and mixtures thereof. Partially delithiated layered nickel oxide suitable for use as an electrochemically active cathode material is described in US 10,910,647 B2, which is incorporated by reference herein. Nickel hydroxide or oxyhydroxide can include beta-nickel oxyhydroxide, gamma-nickel oxyhydroxide, and / or a co-biometal of beta-nickel oxyhydroxide and / or gamma-nickel oxyhydroxide. Nickel oxyhydroxide coated with cobalt oxide can include beta-nickel oxyhydroxide coated with cobalt oxide, gamma-nickel oxyhydroxide coated with cobalt oxide, and / or a co-biometal of beta-nickel oxyhydroxide and gamma-nickel oxyhydroxide coated with cobalt oxide. For example, the high valence nickel compound can include tetravalent nickel. For example, the high valence iron compound can include hexavalent iron. The electrochemically active cathode material can include a combination of one or more of the foregoing exemplary electrochemically active cathode materials.

[0045] The cathode 120 can include conductive additives, such as carbon particles and a binder. Carbon particles are included in the cathode 120 to facilitate electron flow through the cathode 120. The carbon particles can be graphite, such as expanded graphite and natural graphite; graphene, single-walled nanotubes, multi-walled nanotubes, carbon fibers; carbon nanofibers; and mixtures thereof. The amount of carbon particles in the cathode is preferably relatively low, For exampleless than about 3.5%, or even less than about 3.25%, for example from about 2.0% to about 3.25%. Lower carbon levels enable a higher loading of electrochemically active cathode material to be included within the cathode 120 without increasing the volume of the cathode 120 or reducing the void volume of the finished battery 10 (which must remain at or above a certain level to prevent excessive internal pressure build-up in the event of gas generation within the cell). A suitable expanded graphite can be, for example, BNB-90 graphite available from TIMCAL Carbon & Graphite (Bodio, Switzerland).

[0046] Examples of binders that can be used in the cathode 120 include polyethylene, polyacrylic acid, or fluorocarbon resins such as PVDF or PTFE. An example of a polyethylene binder is sold under the trade name COAT HYLENE HA-1681, available from Hoechst or DuPont. Examples of other cathode additives are described in, for example, U.S. Patents 5,698,315, 5,919,598, 5,997,775, and 7,351,499.

[0047] The anode 118 includes at least one electrochemically active anode material, and typically also includes a gelling agent and a small amount of additives such as a gas evolution inhibitor. The electrochemically active anode material can include zinc; cadmium; iron; metal hydrides including, but not limited to, AB5, AB2, and A2B7 metal hydride alloys; and mixtures thereof. The anode 118 is typically provided as a gelled zinc anode.

[0048] To close the end 124 after the components of the battery cell 110 are disposed within the housing 116, the first cover 112 is received within a groove 126 of a grommet or seal 128 disposed proximate the distal end 115 of the housing 116, and the sidewall 129 of the housing 116 is crimped over the peripheral edge of the seal 128. In some examples, the seal 128 is spaced from the cathode 120 to enable expansion of the cathode 120. In some examples, the seal 128 is similarly spaced from the anode 118 to enable expansion of the anode 118. The cover 112 is disposed over the seal 128 to form a space or void X. The void X allows space for gas to escape when pressure builds up inside the housing 116.

[0049] To couple the anode current collector 130 and the first cover 112 (which provides the negative terminal in the assembled battery cell 110), in this example, the seal 128 includes a first opening 132 having a wider portion 134 defining a head gap or space 136, wherein the end or head 138 of the anode current collector 130 (sometimes referred to as a "peg") is positioned at and electrically coupled to the first cover 112. The space 136 may have a chamfered or angled configuration to accommodate the head 138. In this example, the body 140 of the anode current collector 130 extends through the first opening 132 and into the anode 118. The electrolyte solution is contained within a housing 116.

[0050] The seal 128 includes a cylindrical portion or boss 133 surrounding the first opening 132. The boss 133 extends both upward and downward from the planar sealing portion or support 135, which extends laterally outward from the boss 133. The boss 133 is referred to herein as a long boss. As used herein, a "long boss" is a boss having cylindrical sections simultaneously positioned above and below the support 135.

[0051] Now go to Figure 3 and Figure 4 The sealing assembly 100 of the battery cell 110 is shown in more detail. (This is achieved by using...) Figure 2 and Figure 3 The cable ring 128 and nail 130 shown in the disclosure replace the conventional seal 28 and anode collector 30 of FIG1. Figure 3 and Figure 4 The sealing assembly shown can be implemented in the battery cell 10 shown in FIG. 1. The sealing assembly 100 includes a grommets or seals 128 comprising a top space 136 and an opening 132. The top space has a top space diameter, and the opening includes an inner surface with an aperture 150. The opening 132 has a proximal end 151 near the top 153 of the seals 128 and a distal end 154 near the bottom 155 of the seals 128. When assembled, the proximal end 151 or top 153 of the seals 128 is adjacent to a cover 112 providing a negative terminal for the battery cell 110, and the bottom 155 of the seals 128 is positioned closer to the anode, cathode, and electrolyte of the battery cell 110. A stud 130 includes a stud head 138 and a body or rod 140 extending from the stud head 138.

[0052] During assembly, rod 140 extends from proximal end 151 through distal end 154 through opening 132 in seal 128, and pin head 138 is located in top space 136 near proximal end 151. Top space 136 may be chamfered. During assembly, rod 140 and seal 128 form a first interference fit 152 near distal end 154 of opening 132, and a second interference fit is formed between rod 140 and seal 128 near proximal end 151 of seal 128. During assembly, trap gap 160 is formed radially and longitudinally between rod 140 and hole 150 and between distal end 154 of opening and pin head 138, or more specifically, between first interference fit 152 and second interference fit. Trapper gap 160 defines trap 164 for sealant 170. Sealant 170 is disposed on rod 140 and is at least partially located in trap 164. Therefore, the opening 132 of the seal 128 includes a first gap (catch gap 160) and a second gap (top space 136).

[0053] like Figure 3 As shown, the shank 140 of the nail 130 includes a first portion 172 having a first shank diameter D and a second portion 174 having a second shank diameter B. The second shank diameter B is smaller than the first shank diameter D. The first portion 172 also includes a length E shorter than the length F of the opening 132, one end of which is defined by a scraper 180 and the other end by the top 153 of a seal 128. The second portion 174 is located distal to the nail head 138 from the first portion 172. As shown, the first portion 172 and the second portion 174 of the shank 140 are joined by a chamfer 176, but a more "abrupt" stepped transition between the first portion 172 and the second portion 174 can also be used, provided that the second portion 174 has a smaller diameter than the first portion 172, as previously described.

[0054] Hole 150 includes a diameter C. The diameter C is greater than the diameter B of the second rod and less than the diameter D of the first rod.

[0055] A trap 164 is formed between the hole 150 and the second portion 174 of the rod 140. The trap 164 is radially defined internally by the outer surface of the second portion 174 and externally by the inner surface of the hole 150. In the illustrated example, the trap 164 forms an annular space.

[0056] In the illustrated example, the sealing opening 132 includes an inner annular ring 180 with a ring diameter A, which protrudes from the inner surface of the bore 150 near the distal end 154 of the seal 128. The ring diameter A is smaller than the bore diameter C. As described above, the rod 140 and the seal 128 form a first interference fit 152 between the second rod diameter B and the ring diameter A near the distal end 154 of the opening 132. In other words, asFigure 3 As shown, when the post 140 is fully inserted into the seal 128, the inner annular ring 180 forms a first interference fit 152 with the second portion 174 of the post 140 because the second post diameter B is greater than the ring diameter A. Optionally, a lower bore 181 having a wider diameter than the inner annular ring 180 can be included that opens to the interior components of the battery cell.

[0057] The trap 164 is longitudinally above the inner annular ring 180 along the post 140. In the illustrated example, the trap 164 is longitudinally bounded by the inner annular ring 180 and the chamfer 176 when the post 140 is fully inserted into the seal 128 in the illustrated embodiment. This is due to the length E of the first portion 172 being shorter than the length F of the bore 150, where the length E is measured from the bottom of the stud head 138 to the transition or change in inner diameter of the post 140 (illustrated as a chamfer) and the length F is measured from the proximal end of the opening 132 to the inner annular ring 180. The structural arrangement of the post 140 in the bore 150 is purposefully arranged to provide a void, which is the trap 164. Figure 3

[0058] In the illustrated example, the bore diameter C is 0.03 mm to 0.05 mm greater than the second post diameter B. In other examples, the following size ratios can advantageously produce an effective sealant trap gap as described herein:

[0059] The length E of the first portion of the post 172: the diameter D of the first portion 172 of the post 140 is between about 1.1 and about 3.0, such as between about 1.1 and about 1.2;

[0060] The diameter D of the first portion 172 of the post 140: the diameter B of the second portion 174 of the post 140 is between about 1.1 and about 3.0, such as between about 1.1 and about 2.0;

[0061] The inner ring diameter A of the inner annular ring 180: the diameter B of the second portion 174 of the post 140 is less than 1.0; and

[0062] The length F of the bore 150: the length E of the first portion 172 of the post 140 is between about 1.1 and about 2.0, such as between about 1.1 and about 1.5.

[0063] In the illustrated example, the volume of the trap 164 is between about 0.35 mm 3 and about 1.5 mm 3 In other examples, the trap 164 can be configured to have other volumes depending on the viscosity of the sealant 170 and / or the size of the battery cell.

[0064] ​The seal 128 according to the present disclosure advantageously reduces or eliminates leakage of electrolyte from the interior of the battery cell by capturing and positioning the sealant in the gap between the two interference portions, thereby positioning the sealant in a location where it can more effectively provide a barrier to electrolyte leakage (as the sealing effect of the sealant is further enhanced by the interference fit between the peg 130 and the seal 128 further along the peg 130 axis toward the proximal end 151 of the seal 128). Moreover, the seal 128 according to the present disclosure further reduces electrolyte leakage by reducing or compensating for manufacturing defects. More specifically, as noted above, the peg 130 can have defects, for example, at the distal end (which is located in the second portion 174 of the stem 140 having the second stem diameter B). During assembly, these defects are isolated from the first inner surface portion 178 of the opening 132 because the second stem diameter B is smaller than the bore diameter C. Thus, during assembly, the peg 130 does not cause damage to the first inner surface portion 178 of the opening 132. Any damage to the seal 128 that the peg 130 can cause during assembly will be limited to the annular ring 180 where the interference fit exists. However, because the sealant is disposed on the second portion 174 of the stem 140 and is scraped by the annular ring 180 during assembly, the sealant is purposefully and advantageously positioned above the annular ring 180 in the trap 164, whereby any electrolyte leakage (including any damaged area along the annular ring 180 due to insertion of the peg 130) can be prevented or reduced, particularly because of the enhancement of the seal provided by the purposefully positioned sealant 170 by the interference fit between the first portion 172 of the stem 140 and the bore 150.

[0065] Moreover, as Figure 4Best shown in the middle, during manufacture and assembly, the illustrated embodiment advantageously pushes the sealant 170 extending beyond the lateral edge of the seal opening 132 upward along the first portion 172 of the peg 130, thereby depositing a thin layer of sealant 170 between the first portion 172 of the peg 130 and the inner surface 150 of the opening 132. Because a droplet of sealant is applied below the first portion 172 prior to assembly, some of the sealant 170 present on the peg 130 is scraped by the first inner surface portion 178 of the opening 132, and then the remaining sealant 170 is pushed downward by the first portion 172 of the stem 140, which prevents the sealant 170 from escaping upward due to the interference fit between the first portion 172 of the peg 130 and the first inner surface portion 178 of the opening 132. The force applied from the chamfer 176 of the first portion 172 causes the sealant 170 pushed down into the trap 164 to flow into the trap 164 in a relatively uniform manner, resulting in a uniform distribution of sealant in the trap 164. Thus, upon insertion of the peg 130, the sealant 170 in the trap 164 is advantageously captured between two interference fits (the first interference fit between the annular ring 180 and the second portion 174, and the second interference fit between the first portion 172 and the first inner surface portion 178), and forms an additional sealing surface, all of which form an enhanced seal that reduces or prevents the escape of electrolyte from the battery cell. Furthermore, the first portion 172 of the stem compresses the sealant 170 in the trap 164, thereby enhancing the effectiveness of the sealant 170. The chamfer 176 controls the rate and direction of the compression force. Furthermore, the interference fit between the first portion 172 of the stem and the first inner surface portion 178 of the opening 132 helps to prevent the seal ultimately formed by the sealant 170 from being compromised, thereby helping to maintain the effectiveness of the sealant 170 in the seal assembly. Finally, the sealant 170 scraped off on the first portion 172 of the peg 130 accumulates on the top of the peg 130, just below the peg head 138 and is captured in the head gap 136, thereby forming a second droplet of sealant 170 above the second interference fit (between the first portion 172 and the first inner surface portion 178), which serves as yet another additional barrier to electrolyte leakage.

[0066] In alternative embodiments, multiple sealant traps 164a, 164b can be formed, for example as shown in Figure 5 . The unnumbered structural elements of the embodiment of Figure 5 are associated with the same structural elements of the embodiment of Figures 2 to 4 , and function accordingly. For example, the peg head (138 in Figures 2 to 4 is not numbered or labeled in Figure 5 , but the peg head of the embodiment of Figure 5 functions identically to the peg head 138 of Figures 2 to 4 . For the sake of clarity, Figure 5The sealant (170) in FIG. 1 is omitted in Figures 2 to 4 but is disposed in the same location as the sealant in the embodiment of FIG. 2 (e.g., within the sealant traps 164a, 164b and within the head gap 136) in this embodiment. Figures 2 to 4

[0067] The plurality of sealant traps 164a, 164b form a graded seal that provides enhanced sealing and increased prevention of electrolyte leakage. The peg 130 includes a first portion 172 having a first diameter H, a second portion 174 having a second diameter I, and a third portion 173 having a third diameter J. The first diameter H is greater than both the second diameter I and the third diameter J, and the second diameter I is greater than the third diameter J.

[0068] As shown, the first sealant trap 164a is formed longitudinally between the first chamfer 176a and the first annular ring 180a, and laterally between the second portion 174 of the peg 130 and the first inner surface portion 178a. The second sealant trap 164b is formed longitudinally between the second chamfer 176b and the second annular ring 180b, and laterally between the third portion 173 of the peg 130 and the second inner surface portion 178b.

[0069] In other embodiments, more than two sealant traps can be formed by adding additional annular rings 180 and segmented portions of the peg 130 having different diameters.

[0070] Turning now to Figure 6 , a cross-sectional view of an alternative embodiment of a seal assembly 200 according to the present disclosure is shown. According to the disclosure shown in FIG. 2, the seal 28 and anode current collector 30 of FIG. 1 are replaced with a seal 228 and a peg 230, Figure 5 the seal assembly 200 shown in FIG. 2 can be implemented in the battery cell 110 described in FIG. 1. The seal assembly 200 includes a seal 228 that includes an opening 232 that includes a bore 250 having a bore diameter. The peg 230 has a peg head 238 and a body or stem 240 extending from the peg head 238. The stem 240 extends through the opening 232 in the seal 228. The stem 240 and the seal 228 form a first interference fit 252 at a distal end 254 of the opening 232. A trap gap 260 is formed between the distal end 254 of the opening and the peg head 238. The trap gap 260 defines a trap 264 for a sealant 270. The sealant 270 is disposed on the stem 240 and at least partially located in the trap 264. Figure 6 Figure 2

[0071] ​​​The stem 240 includes a first portion 272 having a first stem diameter and a second portion 274 having a second stem diameter. The second stem diameter is smaller than the first stem diameter. The second portion 274 is distal to the first portion 272 relative to the staple head 238. The first and second portions 272, 274 are joined by a chamfer 276, although a more "jarring" step transition between the first and second portions 272, 274 can also be used, provided that the second portion 274 has a smaller diameter than the first portion 272, as previously described.

[0072] The bore 250 has a diameter that is greater than the second stem diameter and less than the first stem diameter.

[0073] A trap 264 is formed between the bore 250 and the second portion 274 of the stem 240. The trap 264 is radially bounded on the inside by the outer surface of the second portion 274 of the stem 240 and on the outside by the inner surface 278 of the bore 250. The trap 264 in the illustrated example is partially provided by an annular recess 290 formed in the staple 230. In the illustrated example, the bore diameter is between 0.03 mm and 0.05 mm greater than the second stem diameter.

[0074] Figure 6 The illustrated embodiment differs from Figures 3 to 5 The illustrated embodiment because Figure 6 The embodiment of FIG. 1 1 does not include the annular ring 180 at the distal end 254 of the opening 232. Instead, Figure 6 The embodiment of FIG. 1 1 includes an annular recess 290 formed between the second portion 274 of the stem 240 and the bore 250. The sealant trap 264 is provided by the annular recess 290.

[0075] In alternative embodiments, the stem 240 can include a plurality of annular recesses 290.

[0076] Test data

[0077] Reference is made to Figures 2 to 4Battery cells having the above-described trapped sealant seal assemblies were subjected to leak tests and compared to control cells tested under the same conditions. One set of control cells tested included the same components (anode, cathode, separator, seal assembly, current collector) and concentrations as commercially available AA COPPERTOP® cells and thus these control cells are referred to herein as AA COPPERTOP® cells. Also included in the data are another set of control cells labeled "Control Scrubbed Polyamide Long Tab" and "Control Scrubbed Asphalt Long Tab" which are not commercially available cells. Both of the "Control Scrubbed Long Tab" control cells include a long tab and a scrubbed sealant. The "Control Scrubbed Long Tab" control cells do not include the stepped outer diameter of the peg or the stepped inner diameter of the tab opening described with respect to the trapped sealant configurations according to the present application. The "Control Scrubbed Long Tab" control cells provide a comparison example that specifically isolates the effect of the trapped sealant design according to the present application. More specifically, the improvement between the "Trapped Long Tab" and the "Control Scrubbed Long Tab" is attributable solely to the trapped sealant configuration according to the present application.

[0078] The leak tests performed on the battery cells included rinsing the space between the seal or grommet and the top cover (labeled as void X in Figure 2 ° C and greater than 60% relative humidity to promote 3, 6, or 9 weeks of accelerated aging, removing the cells from the chamber and extracting any chemicals in void X by rinsing again with deionized water, collecting the deionized water and analyzing the deionized water for the presence of potassium. Any potassium found in the deionized water was considered to be the result of electrolyte leakage between the peg and the seal or grommet because the seal or grommet comprises a polymer material that does not allow a quantifiable amount of potassium to pass directly through the polymer material.

[0079] Two different tab lengths and two different sealants were included in the test cells. The two tab lengths were long tabs and short tabs and the two different sealants were polyamide and asphalt. The AA COPPERTOP® control cells included a short tab with the selected sealant in a scrubbed configuration as described above in which the sealant is placed on the peg and "scrubbed" up the peg as the peg is inserted into the seal such that the sealant is placed proximate the peg head after insertion of the peg. A second set of control cells included a long tab with the selected sealant in a scrubbed configuration in which the sealant is also placed proximate the peg head after insertion of the peg. The trapped sealant cells according to the present application included a seal assembly with the sealant traps discussed above with reference to Figures 2 to 4 Discussion in the long tab with the sealant traps discussed above with reference to ​

[0080] The test results are summarized in Tables 1 and 2 below.

[0081] Design Mean Standard error Lower limit Upper limit Example 1 - Trapped polyamide long protrusion 0.78475 0.037287 0.710954 0.858546 Controlled scraped polyamide long protrusion 1.2315 0.0320915 1.16799 1.464252 COPPERTOP® AA 2.31 0.0453842 2.22018 2.39982

[0082] Table 1

[0083] Design Mean Standard error Lower limit Upper limit Example 2 - Trapped asphalt long protrusion 1.41267 0.0262026 1.36081 1.46452 Controlled scraped asphalt long protrusion 1.5455 0.320915 1.48199 1.60901 COPPERTOP® AA 2.31 0.0453842 2.22018 2.39982

[0084] Table 2

[0085] The tabular results above are shown in graphical form in Figure 7 and Figure 8 Two general conclusions are drawn from the test data. First, the polyamides appear to generally outperform the bitumens, suggesting that other relatively non-polar sealants such as silicone sealants, epoxy sealants, and the like can similarly perform in this assembly. However, the second and most important conclusion is that the trapped sealant sealed assemblies (as described herein) surprisingly and significantly outperform both the COPPERTOP® and the control scraped long boss configurations. Overall, the trapped sealant polyamide configuration shows 66% less leakage than the COPPERTOP® unit, and the trapped sealant bitumen configuration shows 38% less leakage than the COPPERTOP® unit. The trapped sealant polyamide configuration also shows 49% less leakage than the control scraped long boss polyamide configuration, and the trapped sealant bitumen configuration shows 8.5% less leakage than the control scraped long boss bitumen configuration.

[0086] While some improvement over the control units is expected with the trapped sealant configurations, the magnitude of the improvement achieved is unexpected and surprising, especially for the trapped polyamide long boss design.

[0087] The trapped short boss configuration was not tested since the short boss configuration does not provide sufficient space to actually implement a trapped sealant. In other words, the short boss seal does not have sufficient space within the bore to incorporate a sealant trap with sufficient volume to make the trapped sealant effective.

[0088] In any of the foregoing embodiments, the seal or grommet can comprise a polymer, particularly one or more thermoplastic polymers such as polypropylene or nylon. Nylon 66 and nylon 612 are two specific representative materials that can be used alone or in combination.

[0089] In any embodiment, the peg can comprise an electrically conductive metal, for example brass or bronze (including silicon bronze). A brass alloy having a copper content greater than about 50% by weight (e.g. 60% or 70% by weight) and a zinc content greater than 20% by weight (e.g. 30% or 40% by weight) can be used.

[0090] The sealant can be any known sealant capable of adhering the grommet to the pin. Thus, in the illustrated embodiments, the sealant can include a polyamide sealant, a resin, a polyvinyl acetate sealant, a petroleum-based material such as an asphalt sealant, a polybutene sealant, a polyisobutylene sealant, a polyethylene wax sealant, an epoxy sealant, a silicone sealant, an acrylic sealant, a polysulfide sealant, a polyurethane sealant, and mixtures thereof. In the illustrated embodiments, the grommet comprises a polymer and the pin comprises a metal. In one refinement, a relatively hydrophilic sealant comprising a water-swellable polymer can be used to provide the sealant, e.g., a water-swellable acrylate polymer, including superabsorbent particles, such as Sika Swell® sealant (Sika AG, Switzerland). Solvents that can be advantageously used to formulate the sealant for application to the pin include, but are not limited to, xylene, isopropyl alcohol, toluene, and mixtures thereof. In other embodiments, the formulated sealant can have a viscosity of about 165 cps to about 1600 cps, with a solids content of about 40% to about 80%. Further, in other embodiments, the sealant can advantageously include an anaerobic type sealant, as exposure of the sealant to oxygen is effectively eliminated when the seal assembly is fully assembled, such that the sealant trap is formed between the interference fit above and below the trap. Because the sealant can initially be in an uncured state after the pin is inserted into the grommet, the sealant can have sufficient time in the liquid phase to completely fill the trap and fill any defects present in the seal and even the pin (including the manufacturing defects described above) before curing.

[0091] The disclosed seal assembly advantageously traps the sealant in the sealant trap, thereby minimizing exposure of the assembled battery cell to oxygen and preventing migration of electrolyte to the top of the peg and out of the seal assembly. Furthermore, due to the interference fit between the peg shank and the seal at the distal end of the sealed opening, and the relatively larger inner diameter of the first inner portion of the opening relative to the second, narrower inner portion of the opening (e.g., provided by the inner annular ring), the sealant is effectively disposed in the sealant trap. As the shank is inserted into the seal, the inner annular ring scrapes the remaining sealant off of the shank and precisely positions the sealant in the sealant trap. Since the sealant is deposited in liquid form on the peg shank prior to the seal assembly, the sealant flows uniformly into the sealant trap due to the scraping by the inner annular ring, thereby providing a substantially uniform 360 degree seal between the peg and grommet in a consistent and controlled reproducible manner. The sealant in the sealant trap, in combination with the interference fit above and below the sealant trap, effectively forms a seal assembly having three different sealing surfaces that prevent or greatly reduce the amount of electrolyte leakage. When sealant is also disposed in the head gap, four different sealing surfaces are formed (a fourth sealing surface is formed by the sealant in the head gap). In embodiments having more than one sealant trap (e.g., Figure 5 the illustrated embodiment), five or more different sealing surfaces can be formed. Furthermore, the location of the sealant in the sealant trap (i.e., between the two interference fits) creates an additional barrier to any electrolyte that successfully migrates through the lower interference fit (which, in the first embodiment, is created by the annular ring and the second portion of the peg shank). The disclosed seal assembly also advantageously mitigates manufacturing defects in the seal, such as flash or burrs caused by insertion and extraction of the peg into the seal during molding of the seal as described above.

[0092] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and functionally equivalent values surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm." Furthermore, any dimensions disclosed in one embodiment are equally applicable to other embodiments. In cases where "interference" fits are described above, alternative embodiments can have very small gaps if a more viscous sealant is used. For example, as the viscosity of the sealant increases, the ratio of diameter A of the annular ring 180 to diameter B of the second portion 174 of the peg 130 can exceed a value greater than 1.0. In such examples, a diameter A that is greater than diameter B can facilitate venting of gas out of the opening 132 during assembly by allowing gas to escape through a very small gap between diameter A and diameter B as the peg 130 is inserted into the seal 128, while the viscous sealant then seals the gap as the sealant contacts the annular ring 180.

[0093] Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any application disclosed or claimed herein or that it alone, or along with any other reference or references, teaches, suggests or discloses any such application. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0094] While particular embodiments of the present application have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the application. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this application.

Claims

1. A sealing assembly for a battery cell, the sealing assembly comprising: a grommet having an opening comprising an inner surface; a stud having a stud head and a shaft extending from the stud head, the shaft comprising a first portion having a first shaft diameter and a second portion having a second shaft diameter, the first shaft diameter being greater than the second shaft diameter, the shaft extending through the opening in the grommet, the shaft and the grommet forming a first interference fit at a distal end of the opening and a trap gap between the distal end of the opening and the stud head, the trap gap being located between the second portion of the stud and the inner surface and the trap gap defining a trap for a sealant; and a sealant disposed on the shaft, the sealant being at least partially located in the trap, wherein the inner surface of the opening comprises a bore having a bore diameter, the bore diameter being greater than the second shaft diameter and less than the first shaft diameter, and wherein the opening further comprises an inner annular ring having a ring diameter that is less than the bore diameter and the inner annular ring forms the first interference fit with the second portion of the shaft.

2. The sealing assembly of claim 1, wherein the second portion is distal to the first portion relative to the head.

3. The sealing assembly of claim 1, wherein the first portion and the second portion are joined by a chamfer.

4. The sealing assembly of claim 1, wherein the trap is formed between the inner surface and the second portion of the shaft.

5. The sealing assembly of claim 4, wherein the bore diameter is between 0.03 mm and 0.05 mm greater than the second shaft diameter.

6. The sealing assembly of claim 1, wherein the trap is located above the inner annular ring along a length of the shaft.

7. The seal assembly of any of claims 1-6, wherein the volume of the trap is between 0.35 mm 3 and 1.5 mm 3 .

8. The sealing assembly of claim 1, wherein the shaft comprises an annular recess.

9. The sealing assembly of claim 8, wherein the trap gap is formed by the annular recess.

10. The sealing assembly of claim 8 or 9, wherein the shaft comprises a plurality of annular recesses.

11. The sealing assembly of any one of claims 1 to 6, wherein the grommet comprises a polymer comprising polypropylene or nylon.

12. The sealing assembly of any one of claims 1 to 6, wherein the stud comprises brass or silicon bronze.

13. The sealing assembly of any one of claims 1 to 6, wherein the sealant comprises a polyamide or bitumen based material.

14. The sealing assembly of any one of claims 1 to 6, wherein a head gap is formed between the stud head and the grommet and sealant is also disposed in the head gap.

15. A battery cell comprising: a housing comprising: a first cover at a first housing end and a second cover at a second housing end, and an anode and a cathode disposed within the housing; and a sealing assembly according to any one of claims 1 to 14. a seal assembly located proximate the first cover, the seal assembly comprising: a grommet having an opening comprising an inner surface; a staple having a staple head and a shaft extending from the staple head, the shaft comprising a first portion having a first shaft diameter and a second portion having a second shaft diameter, the first shaft diameter being greater than the second shaft diameter, the shaft extending through the opening in the grommet, the shaft and the grommet forming a first interference fit at a distal end of the opening and a trap gap between the distal end of the opening and the staple head, the trap gap being located between the second portion of the staple and the inner surface and the trap gap defining a trap for a sealant; and a sealant disposed on the shaft, the sealant being at least partially located in the trap, wherein the inner surface of the opening comprises a bore having a bore diameter, the bore diameter being greater than the second shaft diameter and less than the first shaft diameter, and wherein the opening further comprises an inner annular ring having a ring diameter that is less than the bore diameter and the inner annular ring forms the first interference fit with the second portion of the shaft.

16. The battery cell of claim 15, wherein the second portion is distal to the first portion relative to the head.

17. The battery cell of claim 15, wherein the first portion and the second portion are joined by a chamfer.

18. The battery cell of claim 15, wherein the trap is formed between the inner surface and the second portion of the shaft.

19. The battery cell of claim 15, wherein the bore diameter is between 0.03 mm and 0.05 mm greater than the second shaft diameter.

20. The battery cell of claim 15, wherein the trap is located above the inner annular ring along a length of the shaft.

21. The battery cell of any one of claims 15-20, wherein the volume of the trap is between 0.35 mm 3 and 1.5 mm 3 .

22. The battery cell of any one of claims 15 to 20, wherein the shaft comprises an annular recess.

23. The battery cell of claim 22, wherein the trap gap is formed by the annular recess.

24. The battery cell of any one of claims 15 to 20, wherein the shaft comprises a plurality of annular recesses.

25. A seal assembly for a battery cell, the seal assembly comprising: a grommet having an opening and a headspace, the opening comprising a distal end, a proximal end, a bore with an inner surface between the distal end and the proximal end, and an inner annular ring positioned proximate the distal end, the inner annular ring having a ring diameter, the bore having a bore diameter; the headspace being at the proximal end, the headspace having a headspace diameter, the ring diameter being less than the bore diameter and the headspace diameter, and the bore diameter being less than the headspace diameter; a staple having a staple head and a shaft extending from the staple head, the shaft including a first portion having a first shaft diameter and a second portion having a second shaft diameter, the first shaft diameter being greater than the second shaft diameter, the shaft extending through the opening in the grommet, the shaft and the grommet forming a first interference fit between the second portion of the shaft and the grommet diameter, and the shaft and the grommet forming a trap gap between the second portion of the shaft and the bore diameter, the trap gap defining a trap for a sealant; and a sealant disposed on the shaft, the sealant at least partially located in the trap, wherein the inner surface of the opening includes a bore diameter that is greater than the second shaft diameter and less than the first shaft diameter.

26. The seal assembly of claim 25, wherein the second portion is distal to the first portion relative to the head.

27. The seal assembly of claim 25, wherein the first portion and the second portion are joined by a chamfer.

28. The seal assembly of claim 25, wherein the trap is formed between the inner surface and the second portion of the shaft.

29. The seal assembly of claim 27, wherein the bore diameter is between 0.03 mm and 0.05 mm greater than the second shaft diameter.

30. The seal assembly of claim 28, wherein the trap is located above the inner annular ring along a length of the shaft.

31. The seal assembly of any of claims 25-30, wherein the volume of the trap is between 0.35 mm 3 and 1.5 mm 3 .

32. The seal assembly of any one of claims 25 to 30, wherein the shaft includes an annular recess.

33. The seal assembly of claim 32, wherein the trap gap is formed by the annular recess.

34. The seal assembly of any one of claims 25 to 30, wherein the shaft includes a plurality of annular recesses.

35. The seal assembly of any one of claims 25 to 30, wherein the grommet comprises a polymer.

36. The seal assembly of any one of claims 25 to 30, wherein the grommet comprises polypropylene or nylon.

37. The seal assembly of any one of claims 25 to 30, wherein the staple comprises brass or silicon bronze.

38. The seal assembly of any one of claims 25 to 30, wherein the sealant comprises a polyamide or bitumen based material.

39. A battery cell comprising: a housing comprising: a first cover at a first housing end and a second cover at a second housing end, and an anode and a cathode disposed within the housing; and a seal assembly located proximate the first cover, the seal assembly comprising: a staple having a staple head and a shaft extending from the staple head, the shaft including a first portion having a first shaft diameter and a second portion having a second shaft diameter, the first shaft diameter being greater than the second shaft diameter, the shaft extending through the opening in the grommet, the shaft and the grommet forming a first interference fit between the second portion of the shaft and the grommet diameter, and the shaft and the grommet forming a trap gap between the second portion of the shaft and the bore diameter, the trap gap defining a trap for a sealant; and a sealant disposed on the shaft, the sealant at least partially located in the trap, wherein the inner surface of the opening includes a bore diameter that is greater than the second shaft diameter and less than the first shaft diameter. a grommet having an opening and a top space, the opening including a distal end, a proximal end, a bore with an inner surface between the distal end and the proximal end, and an inner annular ring positioned adjacent the distal end, the inner annular ring having a ring diameter, the bore having a bore diameter; the top space being at the proximal end, the top space having a top space diameter, the ring diameter being less than the bore diameter and the top space diameter, and the bore diameter being less than the top space diameter; a staple having a staple head and a shaft extending from the staple head, the shaft including a first portion having a first shaft diameter and a second portion having a second shaft diameter, the first shaft diameter being greater than the second shaft diameter, the shaft extending through the opening in the grommet, the shaft and the grommet forming a first interference fit between the second portion of the shaft and the ring diameter, and the shaft and the grommet forming a trap gap between the second portion of the shaft and the bore diameter, the trap gap defining a trap for a sealant; and a sealant disposed on the shaft, the sealant being at least partially located in the trap, wherein the inner surface of the opening includes a bore diameter that is greater than the second shaft diameter and less than the first shaft diameter.

40. The battery cell of claim 39, wherein the second portion is distal to the first portion relative to the head.

41. The battery cell of claim 39, wherein the first portion and the second portion are joined by a chamfer.

42. The battery cell of claim 39, wherein the trap is formed between the inner surface and the second portion of the shaft.

43. The battery cell of claim 39, wherein the bore diameter is between 0.03 mm and 0.05 mm greater than the second shaft diameter.

44. The battery cell of claim 39, wherein the trap is located above the inner annular ring along a length of the shaft.

45. The battery cell of any one of claims 39-44, wherein the volume of the trap is between 0.35 mm 3 and 1.5 mm 3 .

46. The battery cell of any one of claims 39 to 44, wherein the shaft includes an annular recess.

47. The battery cell of claim 46, wherein the trap gap is formed by the annular recess.

48. The battery cell of claim 46, wherein the shaft includes a plurality of annular recesses.

49. The battery cell of any one of claims 39 to 44, wherein the grommet comprises a polymer.

50. The battery cell of any one of claims 39 to 44, wherein the grommet comprises polypropylene or nylon.

51. The battery cell of any one of claims 39 to 44, wherein the staple comprises brass or silicon bronze.

52. The battery cell of any one of claims 39 to 44, wherein the sealant comprises a polyamide or bitumen-based material.

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