Closure Assembly with Low Vapor Transmission for Electrochemical Cell

• US 20090311583A1
• Filed: 06/11/2008
• Published: 12/17/2009
• Est. Priority Date: 06/11/2008
• Status: Active Grant

• Current Assignee: Energizer Brands, LLC (Energizer Holdings, Inc.)
• Original Assignee: Eveready Battery Company Incorporated (Energizer Holdings, Inc.)
• Inventors: Wu, James X.
• Granted Patent: US 8,147,999 B2
• Time in Patent Office: Days
• US Class Current: 429/82
• CPC Class Codes: H01M 50/167 by crimping
• CPC Class Codes: H01M 50/171 using adhesives or sealing agents
• CPC Class Codes: H01M 50/317 Re-sealable arrangements
• CPC Class Codes: H01M 50/3425 in the form of rupturable membranes or weakened parts, e.g. pierced with the aid of a sharp member
• CPC Class Codes: H01M 6/10 with wound or folded electrodes
• CPC Class Codes: H01M 6/16 with organic electrolyte H01M6/18 takes precedence
• CPC Class Codes: Y10T 29/4911 including sealing

Abstract

A closure assembly for an electrochemical cell including a container and an end assembly sealing an open end of the container in order to minimize mass or weight loss of the cell due to electrolyte vapor transmission is disclosed. The end assembly is provided with a vent member capable of venting a fluid when the pressure within the cell exceeds a predetermined limit; a contact member operatively in electrical contact with a conductive contact of the end assembly and a current collector of an electrode of the cell; and an insulating, polymeric seal member disposed at least between conductive components of the closure assembly having different polarities. In a preferred embodiment, the seal member has a selected dimensional ratio in order to minimize vapor transmission of the electrolyte through the seal member.

Claims

1. An electrochemical cell, comprising:

a cylindrical metal container having a closed bottom end, a sidewall and an open end;

a spirally wound electrode assembly disposed within the container, said electrode assembly comprising a positive electrode, a negative electrode consisting essentially of lithium or a lithium alloy, a separator disposed between the positive and negative electrodes, and a non-aqueous volatile electrolyte;

a circumferential inward projection in the sidewall and having an upper wall and a lower wall connected by a transition member, the upper wall inclined upwardly towards a radial center of the cell, and the upper wall spaced apart from the lower wall along their respective lengths; and

an end assembly closing the open end of the container, the end assembly comprising a vent member capable of venting at a predetermined internal pressure, a current limiting or interrupting member, and an insulating, polymeric seal member located between the container and a conductive contact of the end assembly, and wherein the conductive contact is operatively electrically connected to the positive electrode or negative electrode.

2. The electrochemical cell according to claim 1, wherein the bead upper wall has a lowermost point located radially outward from an upper wall uppermost point, and wherein an angle between an imaginary horizontal line extending through upper wall lowermost point and an imaginary line between upper wall lowermost point and upper wall uppermost point is from 1°

to 30°

.

3. The electrochemical cell according to claim 2, wherein the angle is from 3°

to 20°

.

6. The electrochemical cell according to claim 1, wherein the contact assembly further includes a conductive contact member having a peripheral flange connected to a pressure release vent member, the pressure release vent member capable of rupturing in response to internal cell pressure that is at least as high as a predetermined release pressure thereby allowing matter to escape through the vent member, wherein the peripheral flange includes an axial segment that extends an axial distance substantially parallel to a segment of the sidewall adjacent thereto, wherein the peripheral flange includes a radial segment extending from the axial segment in a substantially radial direction and includes a portion located axially above the bead, and wherein the peripheral flange transitions from the radial segment to a second lower axial segment extending in a substantially axial direction, wherein the seal member is under compression between at least (a) the sidewall and peripheral flange axial segment, (b) the bead and the radial segment, and (c) the bead and the second lower axial segment.

7. The electrochemical cell according to claim 1, wherein the end assembly further includes a conductive inner cover in operative electrical contact with the conductive contact, wherein the inner cover has a radial segment and an axial segment, wherein the seal member is compressed between the radial segment and the upper wall of the bead, and wherein the seal member is compressed between the inner cover axial segment and an upper sidewall of the container.

8. The electrochemical cell according to claim 7, wherein a conductive contact member is connected to the inner cover and operatively electrically connected to a current collector of the positive electrode, wherein the cell further includes an insulating member that prevents contact between a portion of a positive electrode current collector and the sidewall of the container, and wherein a portion of the insulating member is in contact with and disposed between the bead and the contact member.

9. The electrochemical cell according to claim 7, wherein the vent member is a ball-type vent member.

10. The electrochemical cell according to claim 1, wherein the end assembly further includes a conductive inner cover, wherein the inner cover includes a segment which forms a portion of a ball vent assembly, wherein the inner cover includes a peripheral flange having a radial segment and an axial segment, wherein the radial segment is located radially outward from the axial extending segment, wherein the seal member is compressed between the axial segment of the inner cover and the transition member of the bead, and wherein the seal member is compressed between the radial segment of the inner cover and the upper wall of the bead.

11. The electrochemical cell according to claim 1, wherein the positive electrode comprises iron disulfide, and wherein the cell is a R6 size cell and the seal member has a dimensional ratio of less than 1.14 cm.

12. The electrochemical cell according to claim 11, wherein the dimensional ratio is less than 0.86 cm.

13. The electrochemical cell according to claim 11, wherein the dimensional ratio is less than 0.51 cm.

14. The electrochemical cell according to claim 1, wherein the positive electrode comprises iron disulfide, and wherein the cell is a R03 or R8 size cell and the seal member has a dimensional ratio of less than 0.86 cm.

15. The electrochemical cell according to claim 14, wherein dimensional ratio is less than 0.48 cm.

16. The electrochemical cell according to claim 14, wherein dimensional ratio is less than 0.30 cm.

17. The electrochemical cell according to claim 6, wherein a cross-sectional area of the seal member between the contact member and the upper wall of the bead is less than 12.5 mm² for a R6 size cell and less than 6.3 mm² for a R03 size cell.

18. The electrochemical cell according to claim 6, wherein the lower axial segment of the contact member extends at least 0.25 mm axially below the upper wall uppermost point of the bead.

19. The electrochemical cell according to claim 7, wherein the inner cover further includes a second axial segment located radially inwardly from the first axial segment, wherein the radial segment connects the axial segments, and wherein the axial segments have a difference in length of less than 20%.

20. The electrochemical cell according to claim 6, wherein the cell further includes an insulating member in contact with the sidewall of the container below the bead and in contact with the contact member so that a portion of the seal member is bounded by the contact member, the insulating member and the bead.

21. The electrochemical cell according to claim 6, wherein the contact member has an inwardly folded end extending from the axial segment, wherein a retainer defining an opening is present in the cell, and wherein a portion of the retainer and a portion of the vent member are compressed between the contact member inwardly folded end and the radial segment.

22. The electrochemical cell according to claim 6, wherein the pressure release vent member is a foil-type vent member and comprises at least a first layer of a composition comprising one or more of a metal and a polymer.

23. The electrochemical cell according to claim 22, wherein the pressure release vent member comprises a second layer comprising a composition selected from the group consisting of:

polyethylene, polypropylene, polybutylene, terephthalate, polyethylene terephthalate, ethylene acrylic acid, ethylene methacrylic acid, polyethylene methacrylic acid, and mixtures thereof, and wherein the pressure release vent member comprises a third layer, the first layer being disposed between the second layer and the third layer, and the third layer comprising a composition selected from the group consisting of;

polyethylene, polypropylene, polybutylene, terephthalate, polyethylene terephthalate, ethylene acrylic acid, ethylene methacrylic acid, polyethylene methacrylic acid, and mixtures thereof.

24. The electrochemical cell according to claim 23, wherein the first layer comprises aluminum.

25. The electrochemical cell according to claim 1, wherein the positive electrode comprises FeS₂.

26. The electrochemical cell according to claim 1, wherein the seal member has an upper radial segment extending in a substantially radial direction situated below a crimped end of the container, wherein the seal member upper radial segment is connected to a seal member upper axial segment extending in a substantially axial direction and in contact with the container sidewall, wherein the seal member upper axial segment extends between the crimped end and the upper wall of the inward projection, wherein the seal member includes a lower radial segment connected to and extending substantially radially inwardly from the upper axial segment, wherein a lower axial segment of the seal member is connected to and extends substantially axially downward from the lower radial segment, wherein the seal member upper radial segment and lower radial segment are compressed between the inward projection upper wall and crimped end of the container, and wherein the seal member lower axial segment is compressed between the transition member and an inner cover or contact member.

27. The electrochemical cell according to claim 6, wherein the seal member has an upper radial segment extending in a substantially radial direction situated below a crimped end of the container, wherein the seal member upper radial segment is connected to a seal member upper axial segment extending in a substantially axial direction and in contact with the container sidewall and the peripheral flange axial segment, wherein the seal member upper axial segment extends between the crimped end and the upper wall of the inward projection, wherein the seal member includes a lower radial segment connected to and extending substantially inwardly from the seal member upper axial segment, wherein the seal member lower radial segment is in contact with and extends a distance along the peripheral flange radial segment, wherein a lower axial segment of the seal member is connected to and extends axially downward from the seal member lower radial segment, wherein the upper radial segment and lower radial segment are compressed between the inward projection upper wall and crimped end of the container, and wherein the seal member lower axial segment is compressed between the transition member of the inward projection and the lower axial segment of the contact member.

28. The electrochemical cell according to claim 7, wherein the seal member has an upper radial segment extending in a substantially radial direction situated below a crimped end of the container, wherein the seal member upper radial segment is connected to an upper axial segment of the seal member extending in a substantially axial direction and in contact with the container sidewall, wherein the upper axial segment extends between the crimped end and the upper wall of the inward projection and is in contact with the inner cover axial segment, wherein the seal member includes a lower radial segment connected to and extending substantially radially inwardly from the seal member upper axial segment, wherein the seal member lower radial segment is in contact with the radial segment of the inner cover and compressed between the inner cover and the upper wall of the inward projection, wherein the seal member upper radial segment is compressed between the inward projection upper wall and crimped end of the container, and wherein the seal member further includes an inner axial segment connected to the seal member lower radial segment that extends substantially radially upwardly between the axial segment of the inner cover and a contact member of the cell.

4. The electrochemical cell according to clam 2, wherein the bead has a depth that is at least 22% of a maximum radius of the container.

5. The electrochemical cell according to claim 4, wherein the bead depth is at least 30% of the radius of the container.

29. An electrochemical cell, comprising:

a cylindrical conductive container having a closed end, an open end sealed by an end assembly, and a sidewall extending between the closed end and the open end, the conductive container being of a first polarity and the end assembly having a contact assembly of a second polarity, said sidewall having an inwardly extending bead;

an electrode assembly comprising a positive electrode, a negative electrode and a separator disposed between the electrodes, and an electrolyte, wherein one of the electrodes is in operative electrical contact with the container and the other electrode is in operative electrical contact with the contact assembly of the end assembly; and

the end assembly comprising a seal member that electrically isolates the sidewall from electrically conductive components of the end assembly having the second polarity, wherein the contact assembly includes a conductive contact member having a peripheral flange connected to a pressure release vent member, the pressure release vent member capable of rupturing in response to internal cell pressure that is at least as high as a predetermined release pressure thereby allowing matter to escape through the vent member, wherein the peripheral flange includes an axial segment that extends an axial distance substantially parallel to a segment of the sidewall adjacent thereto, wherein the peripheral flange includes a radial segment extending from the axial segment in a substantially radial direction and includes a portion located axially above the bead, and wherein the peripheral flange transitions from the radial segment to a second lower axial segment extending in a substantially axial direction, wherein the seal member is under compression between at least (a) the sidewall and peripheral flange axial segment, (b) the bead and the radial segment, and (c) the bead and the second lower axial segment.

30. The electrochemical cell according to claim 29, wherein the cell further includes an insulating member in contact with the sidewall of the container below the bead and in contact with the contact member so that a portion of the seal member is bounded by the contact member, the insulating member and the bead.

31. The electrochemical cell according to claim 29, wherein the contact member has an inwardly folded end extending from the axial segment, wherein a retainer defining an opening is present in the cell, and wherein a portion of the retainer and a portion of the vent member are compressed between the contact member inwardly folded end and the radial segment.

32. The electrochemical cell according to claim 31, wherein a cross-sectional area of the seal member between the contact member and the upper wall of the bead is less than 12.5 mm² for a R6 size cell and less than 6.3 mm² for a R03 size cell.

33. The electrochemical cell according to claim 29, wherein the pressure release vent member is a foil-type vent member and comprises at least a first layer of a composition comprising one or more of a metal and a polymer.

34. The electrochemical cell according to claim 33, wherein the pressure release vent member comprises a second layer comprising a composition selected from the group consisting of:

polyethylene, polypropylene, polybutylene, terephthalate, polyethylene terephthalate, ethylene acrylic acid, ethylene methacrylic acid, polyethylene methacrylic acid, and mixtures thereof, and wherein the pressure release vent member comprises a third layer, the first layer being disposed between the second layer and the third layer, and the third layer comprising a composition selected from the group consisting of;

polyethylene, polypropylene, polybutylene, terephthalate, polyethylene terephthalate, ethylene acrylic acid, ethylene methacrylic acid, polyethylene methacrylic acid, and mixtures thereof, and wherein the first layer comprises aluminum.

35. The electrochemical cell according to claim 29, wherein the positive electrode comprises iron disulfide, and wherein the cell is a R6 size cell and the seal member has a dimensional ratio of less than 1.14 cm.

36. The electrochemical cell according to claim 35, wherein the dimensional ratio is less than 0.86 cm.

37. The electrochemical cell according to claim 35, wherein the dimensional ratio is less than 0.51 cm.

38. The electrochemical cell according to claim 29, wherein the positive electrode comprises iron disulfide, and wherein the cell is a R03 or R8 size cell and the seal member has a dimensional ratio of less than 0.86 cm.

39. The electrochemical cell according to claim 38, wherein dimensional ratio is less than 0.48 cm.

40. The electrochemical cell according to claim 38, wherein the dimensional ratio is less than 0.30 cm.

41. The electrochemical cell according to claim 29, wherein the inwardly extending bead has an upper wall and a lower wall connected by a transition member, wherein the upper wall is inclined upwardly towards a radial center of the cell, and wherein the upper wall is spaced apart from the lower wall along their respective lengths.

42. The electrochemical cell according to claim 41, wherein the bead upper wall has a lowermost point located radially outward from an upper wall uppermost point, and wherein an angle between an imaginary horizontal line extending through upper wall lowermost point and an imaginary line between upper wall lowermost point and upper wall uppermost point is from 1°

to 30°

.

43. The electrochemical cell according to claim 42, wherein the angle is from 3°

to 20°

.

44. The electrochemical cell according to claim 29, wherein the bead has a depth that is at least 22% of a maximum radius of the container.

45. The electrochemical cell according to claim 29, wherein the seal member has an upper radial segment extending in a substantially radial direction situated below a crimped end of the container, wherein the seal member upper radial segment is connected to a seal member upper axial segment extending in a substantially axial direction and in contact with the container sidewall, wherein the seal member upper axial segment extends between the crimped end and an upper wall of the bead, wherein the seal member includes a lower radial segment connected to and extending substantially radially inwardly from the seal member upper axial segment, wherein a lower axial segment of the seal member is connected to the seal member lower radial segment and extends substantially axially downward therefrom, wherein the seal member upper radial segment and lower radial segment are compressed between the bead and crimped end of the container, and wherein the lower axial segment is compressed between the bead and contact member.

46. The electrochemical cell according to claim 34, wherein the seal member has an upper radial segment extending in a substantially radial direction situated below a crimped end of the container, wherein the seal member upper radial segment is connected to a seal member upper axial segment extending in a substantially axial direction and in contact with the container sidewall, wherein the seal member upper axial segment extends between the crimped end and an upper wall of the bead, wherein the seal member includes a lower radial segment connected to and extending substantially radially inwardly from the seal member upper axial segment, wherein a lower axial segment of the seal member is connected to the seal member lower radial segment and extends substantially axially downward therefrom, wherein the seal member upper radial segment and lower radial segment are compressed between the bead and crimped end of the container, and wherein the lower axial segment is compressed between the bead and contact member.

47. The electrochemical cell according to claim 44, wherein the seal member has an upper radial segment extending in a substantially radial direction situated below a crimped end of the container, wherein the seal member upper radial segment is connected to a seal member upper axial segment extending in a substantially axial direction and in contact with the container sidewall, wherein the seal member upper axial segment extends between the crimped end and an upper wall of the bead, wherein the seal member includes a lower radial segment connected to and extending substantially radially inwardly from the seal member upper axial segment, wherein a lower axial segment of the seal member is connected to the seal member lower radial segment and extends substantially axially downward therefrom, wherein the seal member upper radial segment and lower radial segment are compressed between the bead and crimped end of the container, and wherein the lower axial segment is compressed between the bead and contact member.

48. A method for forming an electrochemical cell, comprising the steps of:

providing a cylindrical container having a closed bottom end, a sidewall and an open end;

forming an initial bead in the sidewall of the container after insertion of an electrode assembly into the container, wherein the initial bead is located at a cell axial height above the electrode assembly;

inserting an end assembly into the container so that a peripheral portion of the end assembly is seated on an upper wall of the initial bead;

providing support to a) the bottom end of the container, b) the initial bead with a bead support, and c) the open end of the container and tapering the upper wall upward towards the radial center of the cell; and

crimping the open end of the container sidewall and securing the end assembly between the crimped end and a portion of the upwardly tapered upper wall to form a sealed cell, wherein the bead upwardly tapered upper wall is spaced from a lower wall of the bead in the sealed cell.

49. The method according to claim 48, wherein the bead support extends around the circumference of the cell during formation of the upwardly tapered upper wall.

50. The method according to claim 49, wherein forming the initial bead includes pressing a forming wheel against the sidewall of the container while the can is rotated around its axial axis.

51. The method according to claim 48, wherein during the crimping process, the container is also supported at the bottom of the container.

52. The method according to claim 48, wherein an upper sidewall located above the bead is subjected to diameter reduction.

53. The method according to claim 52, wherein radial compression is maintained on at least the upper sidewall during crimping of the upper end of the container.