Battery cell seal assembly

Abstract

The seal assembly for a battery cell includes a grommet having an opening with an inner surface. The nail has a nail head and a stem extending from the nail head. The stem includes a first portion having a larger diameter and a second portion having a smaller diameter, and the stem extends through the opening in the grommet. The stem 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 nail head. The trap gap defines a trap for a sealant. The sealant is disposed on the stem and is at least partially located within the trap.

Description

Technical Field

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

Background Art

[0002] Consumer electronic devices have certain power requirements. Generally, consumer electronic devices receive power from a single battery cell (contained within the device itself) or a portable battery pack that may include one or more battery cells. Alternatively, one or more single-use or rechargeable consumer battery cells can be used and replaced in the device as needed. Rechargeable consumer battery cells generate electricity by reduction of the cathode and oxidation of the anode. An alkaline electrolyte is often 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 prone 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 because white powder accumulates around the seal of the battery cell. Alkaline electrolyte leakage can be due to creep of the alkaline electrolyte along the negatively polarized electrode. Alkaline electrolyte leakage can be exacerbated by physical factors such as scratches or other physical deformations / defects in the seal of the battery cell. Although powdered alkaline electrolyte is generally safe for human contact, contact should be minimized because respiratory, eye, and skin irritation can occur. Further, when the electrolyte is lost, the performance of the battery cell can degrade. [Overview of the Initiative]

[0004] According to one embodiment, a seal 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 nail has a nail head and a stem extending from the nail head. The stem includes a first portion having a larger first stem diameter and a second portion having a smaller second stem diameter, and the stem extends through the opening of the grommet. The stem and the grommet form a first interference fit at the distal end of the opening. A trap gap is formed between the distal end and the proximal end of the opening. The trap gap is located radially and longitudinally between the second portion of the nail and the inner surface, and the trap gap defines a trap for sealant. The sealant is placed on the stem and is at least partially located within the trap.

[0005] According to another embodiment, the 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. The anode and cathode are located within the housing. A seal assembly is located adjacent to the first cover. The seal assembly includes a grommet having an opening and an inner surface. A nail has a nail head and a stem extending from the nail head. The stem includes a first portion having a larger first diameter and a second portion having a smaller second diameter, and the stem extends through the opening of the grommet. The stem and 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 nail head. The trap gap is located radially and longitudinally between the second portion of the nail and the inner surface, and the trap gap defines a trap for sealant. The sealant is located on the stem, and the sealant is at least partially located within the trap.

[0006] According to another embodiment, a seal assembly for a battery cell includes a grommet having an opening that includes a distal end, a proximal end, and a bore having an inner surface between the distal and proximal ends. An internal annular ring is positioned close to the distal end and has a ring diameter. The bore has a bore diameter. A headspace is located at the proximal end and has a headspace diameter. The ring diameter is smaller than the bore diameter and the headspace diameter, and the bore diameter is smaller than the headspace diameter. A nail has a nail head and a stem extending from the nail head. The stem includes a first portion having a first stem diameter and a second portion having a second stem diameter. The first stem diameter is larger than the second stem diameter. The stem extends through the opening of the grommet. The stem and the grommet form a first interference fit between the second portion of the stem and the ring diameter. The stem and grommet form a trap gap between the second portion of the stem and the bore diameter, which defines a trap for the sealant. The sealant is placed on the stem and is at least partially located within the trap.

[0007] According to another embodiment, the 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 adjacent to the first cover. The seal assembly includes a grommet having an opening that includes a distal end, a proximal end, and a bore having an inner surface between the distal and proximal ends. An internal annular ring is located adjacent to the distal end and has a ring diameter. The bore has a bore diameter. A headspace is located at the proximal end and has a headspace diameter. The ring diameter is smaller than the bore diameter and the headspace diameter, and the bore diameter is smaller than the headspace diameter. The nail includes a nail head and a stem extending from the nail head. The stem includes a first portion having a first stem diameter and a second portion having a second stem diameter. The first stem diameter is larger than the second stem diameter. The stem extends through the opening of the grommet. The stem and grommet form a first interference fit between the second portion of the stem and the ring diameter. The stem and grommet form a trap gap between the second portion of the stem and the bore diameter, which defines a trap for the sealant. The sealant is placed on the stem and is at least partially located within the trap.

[0008] The aforementioned embodiments of the seal assembly or battery cell may further include one or more of the following optional features, structures, and / or forms:

[0009] In some optional configurations, the second part is distal to the first part relative to the head.

[0010] In other optional configurations, the first and second parts are joined by a chamfered portion.

[0011] In other optional forms, the inner surface of the opening includes a bore having a bore diameter, the bore diameter being greater than the second stem diameter and smaller than the first stem diameter, and at least a portion of the second stem diameter is located within the bore diameter, thereby eliminating any interference fit between the second stem diameter and the bore diameter when the nail is assembled to the grommet.

[0012] In other optional forms, the trap is formed in the assembled battery cell between the bore and a second portion of the stem, where the bore diameter is larger than the second stem diameter.

[0013] In other optional configurations, the bore diameter is 0.03 mm to 0.05 mm larger than the second stem diameter.

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

[0015] In other optional forms, the internal annular ring has a ring diameter smaller than the bore, and the internal annular ring forms a first interference fit with the second portion of the stem.

[0016] In other optional forms, the trap is located along the length of the stem, above the internal annular ring.

[0017] In other optional configurations, the trap is 0.35 mm 3 ~1.5mm 3 It has the volume of .

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

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

[0020] In other optional forms, the stem includes multiple annular recesses.

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

[0022] In other alternative forms, the nail includes a metal such as brass or bronze.

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

[0024] In other alternative forms, a head gap is formed between the nail head and the grommet, and the sealant is also disposed in the head gap.

Brief Description of the Drawings

[0025] This specification particularly points out and distinctly claims the subject matter regarded as forming the invention, but the invention will be better understood from the following description taken in conjunction with the accompanying drawings.

[0026] [Figure 1] Cross-sectional view of a prior art battery cell. [Figure 2] Cross-sectional view of a battery cell including a seal assembly enclosed by a sealant according to the present disclosure. [Figure 3] Exploded cross-sectional view before assembly of the seal assembly enclosed by the sealant of FIG. 2. [Figure 4] Cross-sectional view of the assembled seal assembly of FIG. 3. [Figure 5] Cross-sectional view of an alternative embodiment of a seal assembly enclosed by a sealant. [Figure 6] Graphical representation of leak test data for a seal assembly according to the present disclosure including a first sealant. [Figure 7] Graphical representation of leak data for a seal assembly according to the present disclosure including a second sealant.

Modes for Carrying Out the Invention

[0027] Electrochemical cells or batteries can be primary or secondary. Primary batteries are intended to be discharged only once until they are depleted, for example, and then discarded. Primary batteries (i.e., disposable batteries) are described, for example, in David Linden's Handbook of Batteries (4th edition, 2011) (which is incorporated herein by reference). Secondary batteries (i.e., rechargeable batteries) are intended to be recharged and reused. Secondary batteries can be discharged and recharged many times, for example, more than 50 times, more than 100 times, or many more. Secondary batteries are described, for example, in David Linden's Handbook of Batteries (4th edition, 2011) (which is also incorporated herein by reference). Thus, batteries can include a variety of electrochemical coupling and electrolyte combinations. The descriptions and examples provided herein apply to both aqueous, non-aqueous, ionic liquid, and solid-state primary and secondary batteries. While the attached description primarily focuses on consumer-grade, single-use primary alkaline battery cells, the following description may equally apply 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 cell, including the electrolyte solution.

[0028] The seal assemblies provided herein can be incorporated into any type of electrochemical battery cell. For example, the seal assemblies provided herein can be used in consumer alkaline electrochemical cells of any size and / or shape, including but not limited to AAAA cells, AAA cells, AA cells, B cells, C cells, D cells, 9V cells, etc. (including batteries having cylindrical, rectangular, or square shapes or cross-sectional shapes).

[0029] Referring here to Figure 1, an example of a conventional alkaline battery cell 10 is shown. The battery cell 10 includes a first cover 12 and a second cover 14, which correspond to the negative and positive battery terminals, respectively, with a housing 16 positioned roughly between them. 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 positioned within the housing 16, the first cover 12 is received in a groove 26 of a grommet or seal 28 positioned close to the distal end 15 of the housing 16, and the side wall 29 of the housing 16 is pressed against the periphery of the seal 28. In some examples, the seal 28 is spaced away from the cathode 20 to allow the cathode 20 to expand. In some examples, the seal 28 is similarly spaced away from the anode 18 to allow the anode 18 to expand.

[0030] To connect the anode current collector 30 to the first cover 12 that provides the negative terminal to the assembled battery cell 10, in this example, the seal 28 includes a first opening 32 having a wider portion 34 that defines a head gap or space 36, where the end or head 38 (sometimes called a “nail”) of the anode current collector 30 is positioned and electrically coupled to the first cover 12. This space 36 may have a chamfered or angled configuration to accommodate the head 38. In this example, the body 40 of the anode current collector 30 extends into the anode 18 through the first opening 32. The electrolyte solution is contained within the housing 16.

[0031] The seal 28 in Figure 1 includes a cylindrical portion or boss 33 surrounding the first opening 32. The boss 33 extends laterally outward from the boss 33 and extends downward from the shelf portion 35. The boss 33 in Figure 1 is referred to herein as a short boss. The short boss extends below or above the shelf portion 35, but not both.

[0032] As described above, the battery cell is prone to electrolyte leakage due to, for example, electrolyte creep along the body of the anode current collector 30, thereby allowing the electrolyte to escape through the first opening 32 of the seal 28. Previous attempts to prevent leakage have been made by providing sealant around the nail in the opening 32, so that the sealant is "pushed out" or wiped away during assembly (by the tight fit with the seal 28) and thus eventually settle in the space 36 around the head 38. However, the sealant may not be uniformly provided around the head and therefore may not provide a uniform seal and / or may be displaced from the space 36 by electrolyte creep. Furthermore, this existing configuration is more prone to leakage due to defects that may be introduced during manufacturing.

[0033] For example, the distal end of the anode current collector 30 (e.g., the lower end in Figure 1) may have burrs or flash, which could damage the inner surface of the first opening 32 during assembly due to the tight fit provided between these components. More specifically, as the anode current collector 30 is pushed downward through the first opening 32 during assembly, any protruding surface from the anode current collector 30 may rub against the side of the first opening 32 of the seal 28. As a result, defects may form on the inner surface of the first opening 32. These defects can facilitate the upward movement of the electrolyte through the first opening 32 and thus creep, as described above.

[0034] The disclosed seal 28 can be formed by various manufacturing techniques and molding processes. Injection molding and blow molding, which use pins to create a void, are particularly advantageous. Pins used in injection molding and blow molding may also have defects such as burrs and flash, so defects similar to those described above with respect to the anode current collector may be formed during the injection molding or blow molding of the seal 28. Typically, the seal 28 is formed by injection molding, and pins are used during the molding process to create a void that forms the first opening 32 of the seal 28. The distal end of such injection-molded pins is polished, so burrs or flash often occur as a result, which can also cause scratches to form during manufacturing. For example, when the pin is withdrawn from the first opening 32 after the molding process is complete, any defect in the pin may scratch the inner surface of the seal 28 as the pin is withdrawn, similar to how the anode current collector 32 scratches its inner surface, as described above with respect to the insertion of a nail into the seal assembly.

[0035] When the sealant is applied to the anode current collector 30 in Figure 1, during assembly, the sealant is wiped along the axis of the anode current collector 30 by the interference fit between the anode current collector 30 and the first opening 32 when the anode current collector 30 is inserted into the first opening 32, thereby causing the sealant to accumulate on the upper part of the anode current collector 30 near the head 38. The electrolyte from inside the housing 16 can move upward towards the head 38 along the body 40 of the current collector 30, particularly along the path of any defects introduced into the seal 28 during the manufacturing process as described above. Any sealant deposited on the upper part of the anode current collector 30 near the head 38 can be overcome by the creep of the electrolyte along the anode current collector. As a result, electrolyte leakage may occur.

[0036] Referring now to Figure 2, an example of a battery cell 110 having a seal assembly in which sealant is contained is shown. Similar to the example in Figure 1, the battery cell 110 includes a first cover 112 and a second cover 114, which correspond to the negative and positive battery terminals, respectively, with a housing 116 positioned roughly between them. To isolate the anode 118 from the cathode 120, the battery cell 110 includes a separator 122.

[0037] Cathode 120 may include any known electrochemically active cathode material, including but not limited to manganese oxide, manganese dioxide, electrolytic manganese dioxide (EMD), chemical manganese dioxide (CMD), high-performance 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 oxide; nickel oxide; nickel oxyhydroxide; copper oxide; copper salts such as copper iodate; bismuth oxide; high-valence nickel compounds; high-valence iron compounds; and mixtures thereof. Nickel oxide may include nickel hydroxide, nickel oxyhydroxide, cobalt oxyhydroxide-coated nickel 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 U.S. Patent No. 10,910,647B2, incorporated herein by reference. Nickel hydroxide or nickel oxyhydroxide may include β-nickel oxyhydroxide, γ-nickel oxyhydroxide, and / or intergrowth of β-nickel oxyhydroxide and / or γ-nickel oxyhydroxide. Cobalt oxyhydroxide-coated nickel oxyhydroxide may include cobalt oxyhydroxide-coated β-nickel oxyhydroxide, cobalt oxyhydroxide-coated γ-nickel oxyhydroxide, and / or cobalt oxyhydroxide-coated intergrowth of β-nickel oxyhydroxide and γ-nickel oxyhydroxide. High-valence nickel compounds may include, for example, tetravalent nickel. High-valence iron compounds may include, for example, hexavalent iron. Electrochemically active cathode materials may include one or more combinations of the exemplary electrochemically active cathode materials described above.

[0038] The cathode 120 may contain conductive additives and binders, such as carbon particles. The carbon particles are included in the cathode 120 to facilitate the flow of electrons through it. The carbon particles may 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 small, for example, less than about 10%, less than about 7.0%, less than about 4.25%, less than about 3.75%, less than about 3.5%, or even less than about 3.25%, for example, about 2.0% to about 3.25%. Lower carbon levels allow for the inclusion of more electrochemically active cathode material filling within the cathode 120 without increasing the volume of the cathode 120 or decreasing the void volume of the finished battery 10 (which must be maintained above a certain level to prevent the internal pressure from becoming too high due to gas generation within the cell). A suitable expanded graphite could be, for example, BNB-90 graphite, available from TIMCAL Carbon & Graphite (Bodio, Switzerland).

[0039] Examples of binders that can be used with cathode 120 include polyethylene, polyacrylic acid, or fluorocarbon resins such as PVDF or PTFE. An example of a polyethylene binder is sold under the trademark COATHYLENE HA-1681 (available from Hoechst or DuPont). Examples of other cathode additives are described, for example, in U.S. Patents 5,698,315, 5,919,598, 5,997,775 and 7,351,499.

[0040] Anode 118 comprises at least one electrochemically active anode material, and typically further comprises small amounts of additives such as gelling agents and gas generation inhibitors. The electrochemically active anode material may include, but is not limited to, zinc; cadmium; iron; AB5, AB2, and A2B7 metal hydride alloys; and mixtures thereof. Anode 118 is typically supplied as a gelled zinc anode.

[0041] To close the end 124 after the components of the battery cell 110 are placed inside the housing 116, the first cover 112 is received in a groove 126 of a grommet or seal 128 positioned close to the distal end 115 of the housing 116, and the side wall 129 of the housing 116 is pressed against the periphery of the seal 128. In some examples, the seal 128 is spaced away from the cathode 120 to allow the cathode 120 to expand. In some examples, the seal 128 is similarly spaced away from the anode 118 to allow the anode 118 to expand. The cover 112 is positioned over the seal 128 to create a space or void X. The void X allows for gas venting when pressure rises inside the housing 116.

[0042] To connect the anode current collector 130 to a first cover 112 that provides a negative terminal to the assembled battery cell 110, in this example, the seal 128 includes a first opening 132 having a wider portion 134 that defines a head gap or space 136, where the end or head 138 (sometimes called a “nail”) of the anode current collector 130 is positioned and electrically coupled to the first cover 112. This 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 into the anode 118 through the first opening 132. The electrolyte solution is contained within the housing 116.

[0043] 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 shelf portion 135, and a planar sealing portion or shelf portion 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 segments provided both above and below the shelf portion 135.

[0044] Referring here to Figures 3 and 4, the seal assembly 100 of the battery cell 110 is shown in more detail. The seal assembly shown in Figures 3 and 4 can be implemented in the battery cell 10 shown in Figure 1 by using a grommet 128 and nail 130 according to the disclosure shown in Figures 2 and 3, instead of the conventional seal 28 and anode current collector 30 of Figure 1. The seal assembly 100 includes a grommet or seal 128 having a headspace 136 having a headspace diameter and an opening 132 having an inner surface or bore 150 having a bore diameter. The opening 132 has a proximal end 151 near the top 153 of the seal 128 and a distal end 154 near the bottom 155 of the seal 128. When assembled, the proximal end 151 or upper 153 of the seal 128 is adjacent to the cover 112 that provides the negative terminal of the battery cell 110, and the bottom 155 of the seal 128 is positioned closer to the anode, cathode, and electrolyte of the battery cell 110. The nail 130 comprises a nail head 138 and a body or stem 140 extending from the nail head 138.

[0045] When assembled, the stem 140 extends through the opening 132 of the seal 128 from the proximal end 151 to the distal end 154, and the nail head 138 seats in the headspace 136 near the proximal end 151. The headspace 136 may be chamfered. When assembled, the stem 140 and the seal 128 form a first interference fit 152 adjacent to the distal end 154 of the opening 132, and a second interference fit 157 (Figure 4) between the stem 140 and the seal 128 adjacent to the proximal end 151 of the seal 128. When assembled, a trapping gap 160 is formed radially and longitudinally between the stem 140 and the bore 150, and between the distal end 154 of the opening and the nail head 138, or more specifically, between the first interference fit 152 and the second interference fit 157. The trap gap 160 defines a trap 164 for the sealant 170. The sealant 170 is positioned on the stem 140 and is at least partially located within the trap 164. Thus, the opening 132 of the seal 128 includes a first gap (trap gap 160) and a second gap (headspace 136).

[0046] As best shown in Figure 3, the stem 140 of the nail 130 includes a first portion 172 having a first stem diameter D and a second portion 174 having a second stem diameter B. The second stem diameter B is smaller than the first stem diameter D. The first portion 172 also includes a length E shorter than the length F of the opening 132, with one end bounded by the wiper 180 and the other end bounded by the upper part 153 of the seal 128. The second portion 174 is distal to the first portion 172 relative to the nail head 138. As shown, the first portion 172 and the second portion 174 of the stem 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 if the second portion 174 has a smaller diameter than the first portion 172 as described above.

[0047] Bore 150 includes bore diameter C. Bore diameter C is greater than the second stem diameter B and less than the first stem diameter D.

[0048] The trap 164 is formed between the bore 150 and a second portion 174 of the stem 140. The trap 164 is radially bounded on the inside by the outer surface of the second portion 174 and radially bound on the outside by the inner surface of the bore 150. In the illustrated example, the trap 164 forms an annular space.

[0049] In the illustrated example, the seal opening 132 includes an internal annular ring 180 having a ring diameter A, which protrudes from the inner surface of the bore 150 adjacent to the distal end 154 of the seal 128. The ring diameter A is smaller than the bore diameter C. As described above, the stem 140 and the seal 128 form a first interference fit 152 adjacent to the distal end 154 of the opening 132, between the second stem diameter B and the ring diameter A. In other words, the internal annular ring 180 forms the first interference fit 152 with the second portion 174 of the stem 140 when the stem 140 is fully inserted into the seal 128, as shown in Figure 3, because the second stem diameter B is larger than the ring diameter A. Optionally, a lower bore 181 having a wider diameter than the internal annular ring 180, which opens into the internal components of the battery cell, may be included.

[0050] The trap 164 is longitudinally positioned along the stem 140, above the internal annular ring 180. In the example shown in Figure 3, the trap 164 is longitudinally bounded by the internal annular ring 180 and the chamfer 176 once the stem 140 is fully inserted into the seal 128, in the illustrated embodiment. This is because the length E of the first portion 172 is shorter than the length F of the bore 150, where length E is measured from the bottom of the nail head 138 to the transition or change in the inner diameter of the stem 140 (shown as the chamfer), and length F is measured from the proximal end of the opening 132 to the internal annular ring 180. The structural arrangement of the stem 140 within the bore 150 is intentionally positioned to provide the void that is the trap 164.

[0051] In the illustrated example, the bore diameter C is 0.03 mm to 0.05 mm larger than the second stem diameter B. In other examples, the following dimensional ratios can advantageously create the efficient sealant trapping gap described herein. The length E of the first part 172 of the stem and the diameter D of the first part 172 of the stem 140 are approximately 1.1 to 3.0, for example, approximately 1.1 to 1.2. The diameter D of the first part 172 of the stem 140 and the diameter B of the second part 174 of the stem 140 are approximately 1.1 to 3.0, for example, approximately 1.1 to 2.0. The internal ring diameter A of the internal annular ring 180 and the diameter B of the second part 174 of the stem 140 are less than 1.0. The length F of the bore 150 and the length E of the first part 172 of the stem 140 are approximately 1.1 to 2.0, for example, approximately 1.1 to 1.5.

[0052] In the illustrated example, trap 164 is approximately 0.35 mm 3 ~about 1.5mm 3 It has a volume of . In other examples, trap 164 may be configured to have a different volume depending, for example, the viscosity of sealant 170 and / or the size of the battery cell.

[0053] The seal 128 according to this disclosure advantageously reduces or eliminates electrolyte leakage from inside the battery cell by confining and positioning a sealant in the gap between two interferences, thereby positioning the sealant in a location where it can more effectively provide a barrier against electrolyte creep, because the sealing effect of the sealant is further enhanced by the interlocking fit between the nail 130 and the seal 128 toward the proximal end 151 of the seal 128, further along the axis of the nail 130. Furthermore, the seal 128 according to this disclosure further reduces electrolyte leakage by reducing or compensating for manufacturing defects. More specifically, as described above, the nail 130 may have defects, for example, at its distal end (located in the second portion 174 of the stem 140 having a second stem diameter B). During assembly, these defects are separated from the first inner portion 178 of the opening 132 because the second stem diameter B is smaller than the bore diameter C. As a result, no damage occurs to the first inner surface portion 178 of the opening 132 from the nail 130 during assembly. Any damage that may occur to the seal 128 by the nail 130 during assembly is limited to the annular ring 180 where the interference fit exists. However, the sealant is positioned on the second portion 174 of the stem 140 and, as a result of being wiped by the annular ring 180 during assembly, is intentionally and advantageously positioned on the annular ring 180 within the trap 164, thereby preventing or reducing any electrolyte creep (including along any damaged areas of the annular ring 180 as a result of the insertion of the nail 130) due to the reinforcement of the seal provided by the intentionally positioned sealant 170, particularly by the interference fit between the first portion 172 of the stem 140 and the bore 150.

[0054] Furthermore, as best shown in Figure 4, the illustrated embodiment favorably pushes the sealant 170 extending beyond the side edge of the seal opening 132 upward along the first portion 172 of the nail 130 during manufacturing and assembly, thereby depositing a thin layer of sealant 170 between the first portion 172 of the nail 130 and the inner surface 150 of the opening 132. Before assembly, a bead of sealant is applied beneath the first portion 172, so that some of the sealant 170 present on the nail 130 is wiped away by the first inner surface portion 178 of the opening 132, and the remaining sealant 170 is then pushed downward by the first portion 172 of the stem 140, which prevents the sealant 170 from escaping upward due to the interlocking fit between the first portion 172 of the nail 130 and the first inner surface portion 178 of the opening 132. The force applied from the chamfered portion 176 of the first portion 172 causes the sealant 170 to flow into the trap 164 in a relatively uniform manner, resulting in a homogeneous distribution of the sealant within the trap 164. As a result, when the nail 130 is inserted, the sealant 170 in the trap 164 is advantageously trapped between two interlocking fits (a first interlocking fit between the annular ring 180 and the second portion 174, and a second interlocking fit between the first portion 172 and the first inner surface portion 178), forming an additional sealing surface, all working together to form an enhanced seal that reduces or prevents the electrolyte from escaping from the battery cell. Furthermore, the first portion 172 of the stem compresses the sealant 170 in the trap 164, increasing the effectiveness of the sealant 170. The chamfered portion 176 controls the speed and direction of the compressive 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 prevent the seal ultimately formed by the sealant 170 from being compromised, thereby helping to maintain the effectiveness of the sealant 170 within the seal assembly.Finally, the sealant 170 wiped away by the first portion 172 of the nail 130 accumulates on the upper part of the nail 130 just below the nail head 138 and is trapped in the head gap 136, thereby forming a second bead of sealant 170 over the second tight fit (between the first portion 172 and the first inner surface portion 178), which also serves as an additional barrier against electrolyte creep.

[0055] In alternative embodiments, multiple sealant traps 164a, 164b may be formed, for example, as shown in Figure 5. Unreferenced structural elements in the embodiment of Figure 5 relate to and function accordingly with the same structural elements in the embodiments of Figures 2-4. For example, the nail head (138 in Figures 2-4) is not referenced or mentioned in Figure 5, but the nail head in the embodiment of Figure 5 functions in the same way as the nail head 138 in Figures 2-4. The sealant (170 in Figures 2-4) is omitted from Figure 5 for clarity, but the sealant in this embodiment is located in the same positions as the sealant in the embodiments of Figures 2-4 (e.g., within the sealant traps 164a, 164b and within the head gap 136).

[0056] Multiple sealant traps 164a, 164b form a stepped seal that enhances sealing and improves the prevention of electrolyte creep. The nail 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.

[0057] As shown in the figure, the first sealant trap 164a is formed longitudinally between the first chamfered portion 176a and the first annular ring 180a, and is formed transversely between the second portion 174 of the nail 130 and the first inner surface portion 178a. The second sealant trap 164b is formed longitudinally between the second chamfered portion 176b and the second annular ring 180b, and is formed transversely between the third portion 173 of the nail 130 and the second inner surface portion 178b.

[0058] In other embodiments, three or more sealant traps can be formed by adding an additional annular ring 180 and stepped portions of nails 130 having different diameters.

[0059] Referring now to Figure 6, a cross-sectional view of an alternative embodiment of the seal assembly 200 according to this disclosure is shown. The seal assembly 200 shown in Figure 6 can be implemented in the battery cell 110 described in Figure 2 by using a seal 228 and a nail 230 according to the disclosure shown in Figure 5 instead of the seal 28 and anode current collector 30 of Figure 1. The seal assembly 200 includes a seal 228 having an opening 232 including a bore 250 having a bore diameter. The nail 230 has a nail head 238 and a body or stem 240 extending from the nail head 238. The stem 240 extends through the opening 232 of the seal 228. The stem 240 and the seal 228 form a first interlocking fit 252 at the distal end 254 of the opening 232. A trapping gap 260 is formed between the distal end 254 of the opening and the nail head 238. The trap gap 260 defines a trap 264 for the sealant 270. The sealant 270 is positioned on the stem 240 and is at least partially located within the trap 264.

[0060] 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 nail head 238. The first portion 272 and the second portion 274 are joined by a chamfered portion 276, but a more "abrupt" stepped transition between the first portion 272 and the second portion 274 can also be used if the second portion 274 has a smaller diameter than the first portion 272 as described above.

[0061] The diameter of the 250 bore is larger than the diameter of the second stem and smaller than the diameter of the first stem.

[0062] The 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 radially bound on the outside by the inner surface 278 of the bore 250. In the illustrated example, the trap 264 is partially provided by an annular recess 290 formed in the nail 230. In the illustrated example, the bore diameter is 0.03 mm to 0.05 mm larger than the second stem diameter.

[0063] The embodiment shown in Figure 6 differs from the embodiments shown in Figures 3-5 in that the embodiment in Figure 6 does not include an annular ring 180 at the distal end 254 of the opening 232. Rather, the embodiment in Figure 6 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.

[0064] In an alternative embodiment, the stem 240 may include a plurality of annular recesses 290.

[0065] Test data With respect to Figures 2-4, battery cells having the sealant-enclosed seal assembly described above were subjected to leak testing and compared with control cells tested under the same conditions. One set of tested control cells contained the same components (anode, cathode, separator, seal assembly, current collector) and concentrations as commercially available AA COPPERTOP® cells, and these control cells are therefore referred to herein as AA COPPERTOP® cells. The data also includes another set of control cells, labeled “control wiped polyamide long boss” and “control wiped asphalt long boss,” which are not commercially available cells. Both “control wiped long boss” control cells contain a long boss and wiped sealant. The “control wiped long boss” control cells do not include the stepped outer diameter of the nail or the stepped inner diameter of the boss opening described in relation to the sealant-enclosed configuration according to the present invention. The “control wiped long boss” control cells provide comparative examples that specifically identify the effect of the sealant-enclosed design according to the present invention. More specifically, the improvement between the "enclosed long boss" and the "contrast wiped long boss" is solely due to the enclosed sealant configuration according to the present invention.

[0066] Leak tests performed on battery cells included flushing the space between the seal or grommet and the top cover (indicated as void X in Figure 2) with deionized water, accelerating aging of the cell for 3, 6, or 9 weeks by placing it in an environmental chamber at 50°C and over 60% relative humidity, extracting any chemicals in void X by removing the cell from the chamber and flushing it again with deionized water, capturing the deionized water, and analyzing it for the presence of potassium. Any potassium present in the deionized water was presumed to have been generated by electrolyte creep between the nail and the seal or grommet, because the seal or grommet contains polymer material that does not allow a quantifiable amount of potassium to pass directly through the polymer material.

[0067] Two different boss lengths and two different sealants were included in the test cells. The two boss lengths were a long boss and a short boss, and the two different sealants were polyamide and asphalt. The AA COPPERTOP® control cell included a short boss with a selected sealant having a wipe configuration as described above, where the sealant is placed on the nail and, after nail insertion, the sealant is "wiped off" by the nail when the nail is inserted into the seal, so that the sealant is placed on the nail and, after nail insertion, the sealant is placed close to the nail head. The second group of control cells included a long boss with a selected sealant having a wipe configuration, in this case similarly, where the sealant is placed close to the nail head after nail insertion. The sealant-confined cell according to the present invention included a seal assembly having the sealant trap described above in relation to Figures 2-4 within the long boss. Surprisingly, the sealant-confined cell showed significantly less leakage than both the COPPERTOP® control cell and the wiped long-boss control cell.

[0068] The test results are summarized in Tables 1 and 2 below. [Table 1] [Table 2]

[0069] The results in tabular form above are shown graphically in Figures 7 and 8. Two general conclusions were drawn from the test data. First, polyamide generally appeared to perform better than asphalt, suggesting that other relatively non-polar sealants, such as silicone sealants and epoxy sealants, could perform similarly in this assembly. However, the second, and most important, conclusion was that the sealant-enclosed seal assemblies (as described herein) performed remarkably and significantly better than both commercially available COPPERTOP® and control wiped long-boss configurations. In summary, the sealant-enclosed polyamide configuration showed 66% less leakage than the COPPERTOP® cell, and the sealant-enclosed asphalt configuration showed 38% less leakage than the COPPERTOP® cell. The sealant-enclosed polyamide configuration also showed 49% less leakage than the control wiped long-boss polyamide configuration, and the sealant-enclosed asphalt configuration showed 8.5% less leakage than the control wiped long-boss asphalt configuration.

[0070] While some improvement over the control cell was expected due to the sealant-confined configuration, the magnitude of the improvement achieved was unexpected and surprising, especially in the design of the confined polyamide long boss.

[0071] The confined short boss configuration was not tested because it did not provide sufficient space to actually implement the confined sealant. In other words, the short boss seal does not have enough space within the internal bore to incorporate a seal trap with sufficient volume to effectively implement the confined sealant.

[0072] In any of the embodiments described above, the seal or grommet may include a polymer, in particular one or more thermoplastic polymers such as polypropylene or nylon. Nylon 66 and nylon 612 are two specific representative materials that can be used individually or in combination.

[0073] In any embodiment, the nail may comprise a conductive metal, such as brass or bronze (including silicon bronze). A brass alloy having a copper content exceeding about 50% by weight, for example 60% or 70% by weight, and a zinc content exceeding 20% ​​by weight, for example 30% or 40% by weight, can be used.

[0074] The sealant can be any known sealant capable of adhering the grommet to the nail. Therefore, in the illustrated embodiment, the sealant may include petroleum-based materials such as polyamide sealants, resins, polyvinyl acetate sealants, asphalt sealants, polybutene sealants, polyisobutylene sealants, polyethylene wax sealants, epoxy sealants, silicone sealants, acrylic sealants, polysulfide sealants, polyurethane sealants, and mixtures thereof. In the illustrated embodiment, the grommet comprises a polymer and the nail comprises metal. One improvement is that a relatively hydrophilic sealant containing a water-swellable polymer can be used to provide a water-swellable acrylate polymer containing superabsorbent particles, such as SikaSwell® sealant (Sika AG, Switzerland). Solvents that can be advantageously used to formulate sealants for application to nails include, but are not limited to, xylene, isopropanol, toluene, and mixtures thereof. In other embodiments, the formulated sealant may have a viscosity of about 165 cps to about 1600 cps and may contain about 40% to about 80% solids. Furthermore, in other embodiments, the sealant may advantageously include an anaerobic 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 upper and lower interlocking fits of the trap. Since the sealant may initially be in an uncured state after the nail is inserted into the grommet, the sealant may have sufficient time in the liquid phase to fully fill the trap and to fill any defects, including the aforementioned manufacturing defects, that may be present in the seal and even the nail before curing.

[0075] The disclosed seal assembly advantageously confines the sealant within a sealant trap, thereby minimizing the exposure of the assembled battery cell to oxygen and preventing the electrolyte from moving to the top of the nail and escaping from the seal assembly. Furthermore, due to the tight fit between the nail stem and the seal at the distal end of the seal opening, and the relatively large inner diameter of the first inner portion of the opening compared to a second, narrower inner portion of the opening (e.g., provided by an internal annular ring), the sealant is effectively positioned within the sealant trap. The internal annular ring(s) wipe away any remaining sealant from the stem as the stem is inserted into the seal, precisely positioning the sealant within the sealant trap. Since the sealant is deposited on the nail stem in liquid form before the assembly of the seal, the wipe-away by the internal annular ring ensures uniform flow into the sealant trap, providing a substantially uniform 360-degree seal between the nail and the grommet in a consistently controlled and reproducible manner. The sealant within the sealant trap, in combination with the upper and lower interlocking fits of the sealant trap, effectively forms a seal assembly having three distinct sealing surfaces that prevent or significantly reduce electrolyte leakage. If sealant is also placed in the head gap, four distinct sealing surfaces are formed (a fourth sealing surface is formed by the sealant in the head gap). In embodiments having two or more sealant traps (e.g., the embodiment shown in Figure 5), five or more distinct sealing surfaces may be formed. Furthermore, the position of the sealant within the sealant trap (i.e., between the two interlocking fits) creates an additional barrier against any electrolyte that successfully moves through the lower interlocking fit (generated in the first embodiment by the annular ring and the second portion of the nail stem). The disclosed seal assembly also advantageously mitigates manufacturing defects of the seal, such as flash or burrs, caused by inserting the nail into the seal and withdrawing the pin during the formation of the seal, as described above.

[0076] The dimensions and values ​​disclosed herein should not be understood as being strictly limited to the exact numerical values ​​listed. Instead, unless otherwise specified, each such dimension is intended to mean both the listed value and a functionally equivalent range around that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm". Furthermore, any dimension disclosed in one embodiment is similarly applicable to other embodiments. Where an "interlocking" fit is described above, an alternative embodiment may have a very small clearance when a more viscous sealant is used. For example, as the viscosity of the sealant increases, the ratio of the diameter A of the annular ring 180 to the diameter B of the second portion 174 of the nail 130 may exceed a value greater than 1.0. In such an example, having a diameter A greater than a diameter B facilitates the venting of gas in the opening 132 during assembly by allowing gas to escape through a very small gap between diameters A and B when the nail 130 is inserted into the seal 128, while a viscous sealant in this case seals the gap when the sealant comes into contact with the annular ring 180.

[0077] All documents cited herein, including any cross-references or related patents or applications, and any patent applications or patents on which this application claims priority or interest, are incorporated herein by reference in their entirety unless expressly excluded or otherwise limited. No citation of any document constitutes prior art relating to any invention disclosed or claimed herein, nor does it constitute teaching, suggestion, or disclosure of any such invention, either alone or in any combination with any other reference(s). Furthermore, to the extent that any meaning or definition of any term herein conflicts with any meaning or definition of the same term in any document incorporated by reference, the meaning or definition assigned to that term herein shall apply.

[0078] While specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to encompass all such changes and modifications that fall within the scope of the invention.

Claims

1. A seal assembly for a battery cell, A grommet having an opening including the inner surface, A nail comprising a nail head and a stem extending from the nail head, wherein the stem includes a first portion having a first stem diameter and a second portion having a second stem diameter, the first stem diameter being greater than the second stem diameter, the stem extending through the opening of the grommet, the stem and the grommet forming a first interference fit at the end of the opening, forming a trap gap between the end of the opening and the nail head, the trap gap being located between the second portion of the nail and the inner surface, the trap gap defining a trap for sealant, A sealant disposed on the stem, comprising a sealant that is at least partially located within the trap, The inner surface of the opening includes a bore having a bore diameter, the bore diameter being larger than the second stem diameter and smaller than the first stem diameter. An assembly in which the opening of the grommet includes an internal annular ring, the internal annular ring having a ring diameter smaller than the bore diameter, and the internal annular ring forms a first interference fit with the second portion of the stem.

2. The assembly according to claim 1, wherein the second portion is distal to the first portion with respect to the head.

3. The assembly according to claim 1 or 2, wherein the first portion and the second portion are joined by a chamfered portion.

4. The assembly according to any one of claims 1 to 3, wherein the trap is formed between the inner surface and the second portion of the stem.

5. The assembly according to claim 1, wherein the trap is located on the inner annular ring along the length of the stem.

6. The assembly according to claim 1, wherein the stem includes an annular recess.

7. The assembly according to claim 6, wherein the trap gap is formed by the annular recess.

8. The assembly according to claim 6 or 7, wherein the stem includes a plurality of annular recesses.

9. The assembly according to any one of claims 1 to 8, wherein the grommet comprises a polymer including polypropylene or nylon.

10. The assembly according to any one of claims 1 to 9, wherein the nail comprises brass or silicon bronze.

11. The assembly according to any one of claims 1 to 10, wherein the sealant comprises a polyamide or asphalt-based material.

12. The assembly according to any one of claims 1 to 11, wherein a head gap is formed between the nail head and the grommet, and sealant is also provided in the head gap.

13. It is a battery cell, It is a housing, A housing comprising a first cover at a first housing end, a second cover at a second housing end, and an anode and a cathode disposed within the housing, A seal assembly adjacent to the first cover, A grommet having an opening including the inner surface, A nail comprising a nail head and a stem extending from the nail head, wherein the stem includes a first portion having a first stem diameter and a second portion having a second stem diameter, the first stem diameter being greater than the second stem diameter, the stem extending through the opening of the grommet, the stem and the grommet forming a first interference fit at the end of the opening, forming a trap gap between the end of the opening and the nail head, the trap gap being located between the second portion of the nail and the inner surface, the trap gap defining a trap for sealant, A seal assembly comprising a sealant disposed on the stem, which is at least partially located within the trap, The inner surface of the opening includes a bore having a bore diameter, the bore diameter being larger than the second stem diameter and smaller than the first stem diameter. A battery cell in which the opening of the grommet includes an internal annular ring, the internal annular ring having a ring diameter smaller than the bore diameter, and the internal annular ring forms a first interlocking fit with the second portion of the stem.

14. The battery cell according to claim 13, wherein the second portion is distal to the first portion with respect to the head.

15. The battery cell according to claim 13 or 14, wherein the first portion and the second portion are joined by a chamfered portion.

16. The battery cell according to any one of claims 13 to 15, wherein the trap is formed between the inner surface and the second portion of the stem.

17. The battery cell according to claim 13, wherein the trap is located on the inner annular ring along the length of the stem.

18. The battery cell according to any one of claims 13 to 17, wherein the stem includes an annular recess.

19. The battery cell according to claim 18, wherein the trap gap is formed by the annular recess.

20. The battery cell according to any one of claims 13 to 19, wherein the stem includes a plurality of annular recesses.

21. A seal assembly for a battery cell, A grommet comprising: an opening including a distal end, a proximal end, and a bore having an inner surface between the distal end and the proximal end; an internal annular ring positioned close to the distal end, having a ring diameter, the bore having a bore diameter; and a headspace located at the proximal end, having a headspace diameter, the ring diameter being smaller than the bore diameter and the headspace diameter, and the bore diameter being smaller than the headspace diameter; A nail comprising a nail head and a stem extending from the nail head, wherein the stem includes a first portion having a first stem diameter and a second portion having a second stem diameter, the first stem diameter being greater than the second stem diameter, the stem extending through the opening of the grommet, the stem and the grommet forming a first interference fit between the second portion of the stem and the ring diameter, the stem and the grommet forming a trap gap between the second portion of the stem and the bore diameter, the trap gap defining a trap for sealant, A sealant disposed on the stem, comprising a sealant that is at least partially located within the trap, A seal assembly in which the inner surface of the opening includes a bore diameter, the bore diameter being larger than the second stem diameter and smaller than the first stem diameter.

22. It is a battery cell, It is a housing, A housing comprising a first cover at a first housing end, a second cover at a second housing end, and an anode and a cathode disposed within the housing, A seal assembly adjacent to the first cover, A grommet comprising: an opening including a distal end, a proximal end, and a bore having an inner surface between the distal end and the proximal end; an internal annular ring positioned close to the distal end, having a ring diameter, the bore having a bore diameter; and a headspace located at the proximal end, having a headspace diameter, the ring diameter being smaller than the bore diameter and the headspace diameter, and the bore diameter being smaller than the headspace diameter; A nail comprising a nail head and a stem extending from the nail head, wherein the stem includes a first portion having a first stem diameter and a second portion having a second stem diameter, the first stem diameter being greater than the second stem diameter, the stem extending through the opening of the grommet, the stem and the grommet forming a first interference fit between the second portion of the stem and the ring diameter, the stem and the grommet forming a trap gap between the second portion of the stem and the bore diameter, the trap gap defining a trap for sealant, A seal assembly comprising a sealant disposed on the stem, which is at least partially located within the trap, A battery cell in which the inner surface of the opening includes a bore diameter, the bore diameter being larger than the second stem diameter and smaller than the first stem diameter.

23. The assembly or battery cell according to claim 21 or 22, wherein the second portion is distal to the first portion with respect to the head.

24. The assembly or battery cell according to any one of claims 21 to 23, wherein the first portion and the second portion are joined by a chamfered portion.

25. The assembly or battery cell according to any one of claims 21 to 24, wherein the trap is formed between the inner surface and the second portion of the stem.

26. The assembly or battery cell according to claim 21 or 22, wherein the trap is located on the inner annular ring along the length of the stem.

27. The assembly or battery cell according to claim 21 or 22, wherein the stem includes an annular recess.

28. The assembly or battery cell according to claim 27, wherein the trap gap is formed by the annular recess.

29. The assembly or battery cell according to claim 27 or 28, wherein the stem includes a plurality of annular recesses.

30. The assembly or battery cell according to any one of claims 21 to 29, wherein the grommet comprises a polymer including polypropylene or nylon.

31. The assembly or battery cell according to any one of claims 21 to 30, wherein the nail comprises brass or silicon bronze.

32. The assembly or battery cell according to any one of claims 21 to 31, wherein the sealant comprises a polyamide or asphalt-based material.

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