Crosslinked electrolyte capacitors and methods of making the same

• US 5,146,391 A
• Filed: 11/03/1989
• Issued: 09/08/1992
• Est. Priority Date: 04/30/1987
• Status: Expired due to Term

• Current Assignee: Telectronics Pacing Systems, Inc (Abbott Laboratories Incorporated)
• Original Assignee: Specialised Conductives Pty Limited
• Inventors: Philpott, Arthur K., MacFarlane, Douglas R., Tetaz, John R.
• Primary Examiner(s): Griffin, Donald
• Application Number:
  US07/431,600
• Time in Patent Office: 1,040 Days
• Field of Search: 361/323, 361/311-315, 361/502, 361/523-527, 29/25.42, 29/25.03, 252/62.2, 252/500, 252/63.2, 429/213, 429/194, 128/419 P, 128/419 PG, 128/419 PT, 428/409, 428/421
• US Class Current: 361/525
• CPC Class Codes: H01B 1/122 Ionic conductors
• CPC Class Codes: H01G 11/56 Solid electrolytes, e.g. gels; Additives therein
• CPC Class Codes: H01G 9/022 Electrolytes; Absorbents
• CPC Class Codes: H01G 9/025 Solid electrolytes H01G11/54 takes precedence
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

Compact leak-proof electrolytic capacitors including, between the anode and the cathode, an ultrathin layer of a solid electrolyte, are disclosed. The solid electrolyte comprises a solid solution of (a) an alkali metal salt, a transition metal salt, an ammonium salt, an organic ammonium salt, a zinc salt, a cadmium salt, a mercury salt or a thallium salt of (b) a monbasic, dibasic or tribasic acid other than a haloid acid (c) in a polymer of high solvation power. Preferred salts are the tetrafluoroborates and hexafluoroglutarates of sodium and potassium, and the preferred polymer is a blend of polyethylene oxide with a siloxane-alkylene oxide copolymer. Crosslinking of the polymer is accomplished by using an agent which may be a di -, tri, or polyisocyanate, a multifunctional reagent which is an analogue of the compound to be crosslinked or di - and multifunctional acids, or di - and multifunctional amines. Methods of making such capacitors are also disclosed. Rolled solid electrolyte capacitors of this type are characterized by low volume, absence of electrolyte leakage, and minimum dielectric deformation, and are capable of delivering intense bursts of current on demand, thereby being suitable for use in biomedical electronic devices such as cardiac pacemakers and defibrillators implanted in the human body.

Claims

1. A crosslinked polymer electrolyte having a composition comprising (a) an amorphous solid solution of (i) at least one salt selected from the group consisting of alkali metal salts, alkali earth metal salts, transition metal salts, ammonium salts, organic ammonium salts, zinc salts, cadmium salts, mercury salts and thallium salts of (ii) at least one acid selected from the group consisting of monobasic, dibasic and tribasic acids other than haloid acids (iii) in a polymer, and (b) a crosslinking agent which crosslinks the polymer.

2. The electrolyte of claim 1, wherein said polymer includes at least one of mono-, di-, tri- and poly-functional compounds having alkyleneoxide repeat units.

3. The electrolyte of claim 1, wherein the polymer includes at least one hydroxy compound.

4. The electrolyte of claim 3, wherein said at least one hydroxy compound includes:

##STR3## where R and R'"'"' are H or an alkyl group.

5. The electrolyte of claim 3, wherein the molecular weight of said at least one hydroxy compound is sufficiently low so that the polymer is crosslinked without crystallizing.

6. The electrolyte of claim 1, wherein the crosslinking agent is a diisocyanate.

7. The electrolyte of claim 6, wherein the diisocyanate is selected from the group consisting of hexamethylene diisocyanate, toluenediisocyanate and methyl diphenylisocyanate.

8. The electrolyte of claim 1, wherein each said at least one compound is terminated with an unsaturated functional group.

9. The electrolyte of claim 8, wherein said unsaturated functional group is selected from the group consisting of vinyl, allyl, acrylic and alkacrylic.

10. The electrolyte of claim 9, wherein said crosslinking agent is poly(alkylhydrogensiloxane).

11. The electrolyte of claim 9, wherein said crosslinking agent is a difunctional reagent.

12. The electrolyte of claim 11, wherein said difunctional reagent is an analog of the compound to be crosslinked.

13. The electrolyte of claim 11, wherein said difunctional reagent is selected from the group consisting of a divinyl, diallyl, dialkacrylic and diacrylic analog of the compound to be crosslinked.

14. The electrolyte of claim 8, wherein said compound is selected from the group consisting of:

space="preserve" listing-type="equation">CXY═

CRCOO--(--CH.sub.2 CHR'"'"'O--)--R"

space="preserve" listing-type="equation">CXY═

CRCH.sub.2 O(--CH.sub.2 CHR'"'"'O--)--R"

where X,Y,R and R" are H or alkyl groups and R" is H, an alkyl group or, for a difunctional compound, an unsaturated functional group.

15. The electrolyte of claim 1, wherein said crosslinking agent is selected from the group consisting of di- and multifunctional acids.

16. The electrolyte of claim 1, wherein said crosslinking agent is selected from the group consisting of di- and multifunctional amines

17. The electrolyte of claim 1, wherein said at least one salt is NaBF₄.

18. The electrolyte of claim 1, wherein said at least one salt is KSCN.

19. The electrolyte of claim 1, further comprising a plasticizer having a chemical compatibility with the polymer and in which said at least one salt is soluble.

20. The electrolyte of claim 19, wherein said plasticizer is one of low molecular weight alkylene oxide oligomers and polymers having minimal reaction with said polymer.

21. The electrolyte of claim 20, wherein said plasticizer contains at least one end group comprised of one of an alkyl ether, an alkyl urethane and an ester.

22. The electrolyte of claim 1, wherein the polymer is ethylene oxide based and includes pendant groups for disrupting crystallization.

23. The electrolyte of claim 22, wherein the polymer is selected from the group consisting of copolymers of ethylene oxide and propylene oxide.

24. The electrolyte of claim 23, wherein between substantially six and one hundred percent of repeat units in the polymer ar propylene oxide groups.

25. The electrolyte of any one of claims 1 to 24, formed as a layer in combination with an anode disposed to contact a first side of said layer and a cathode disposed to contact a second side of said layer opposite said first side.

26. A compact capacitor including an electrically conductive anode, an electrically conductive cathode and between said anode and said cathode a crosslinked polymer electrolyte having a composition comprising (a) an amorphous solid solution of (i) at least one salt selected from the group consisting of alkali metal salts, alkali earth metal salts, transition metal salts, ammonium salts, organic ammonium salts, zinc salts, cadmium salts, mercury salts and thallium salts of (ii) at least one acid selected from the group consisting of monobasic, dibasic and tribasic acids other than haloid acids (iii) in a polymer, and (b) a crosslinking agent which crosslinks the polymer.

27. The capacitor of claim 26, wherein said polymer includes at least one of mono-, di-, tri- and polyfunctional compounds having alkyleneoxide repeat units.

28. The capacitor of claim 26, wherein the polymer includes at least one hydroxy compound.

29. The capacitor of claim 28, wherein said at least one hydroxy compound includes:

##STR4## where R and R'"'"' are H or an alkyl group.

30. The capacitor of claim 28, wherein the molecular weight of said at least one hydroxy compound is sufficiently low so that the polymer is crosslinked without crystallizing.

31. The capacitor of claim 26, wherein the crosslinking agent is a diisocyanate.

32. The capacitor of claim 31, wherein the diisocyanate is selected from the group consisting of hexamethylene diisocyanate, toluenediisocyanate and methyl diphenylisocyanate.

33. The capacitor of claim 26, wherein each said at least one compound is terminated with an unsaturated functional group.

34. The capacitor of claim 33, wherein said unsaturated functional group is selected from the group consisting of vinyl, allyl, acrylic and alkacrylic.

35. The capacitor of claim 34, wherein said crosslinking agent is poly(alkylhydrogensiloxane).

36. The capacitor of claim 34, wherein said crosslinking agent is a difunctional reagent.

37. The capacitor of claim 36, wherein said difunctional reagent is an analog of the compound to be crosslinked.

38. The capacitor of claim 36, wherein said difunctional reagent is selected from the group consisting of a divinyl, diallyl, dialkacrylic and diacrylic analog of the compound to be crosslinked.

39. The capacitor of claim 33, wherein said compound is selected from the group consisting of:

space="preserve" listing-type="equation">CXY═

CRCOO--(--CH.sub.2 CHR'"'"'O--)--R"

space="preserve" listing-type="equation">CXY═

CRCH.sub.2 O(--CH.sub.2 CHR'"'"'O--)--R"

where X,Y,R and R'"'"' are H or alkyl groups and R" is H, an alkyl group or, for a difunctional compound, an unsaturated functional group.

40. The capacitor of claim 26, wherein said crosslinking agent is selected from the group consisting of di- and multifunctional acids.

41. The capacitor of claim 26, wherein said crosslinking agent is selected from the group consisting of di- and multifunctional amines.

42. The capacitor of claim 26, wherein said at least one salt is NaBF₄.

43. The capacitor of claim 26, wherein said at least one salt is KSCN.

44. The capacitor of claim 26, further comprising a plasticizer having a chemical compatibility with the polymer and in which said at least one salt is soluble.

45. The capacitor of claim 44, wherein said plasticizer is one of low molecular weight alkylene oxide oligomers and polymers having minimal reaction with said polymer.

46. The capacitor of claim 45, wherein said plasticizer contains at least one end group comprised of one of an alkyl ether, an alkyl urethane and an ester.

47. The capacitor of claim 26, wherein the polymer is ethylene oxide based and includes pendant groups for disrupting crystallization.

48. The capacitor of claim 47, wherein the polymer is selected from the group consisting of copolymers of ethylene oxide and propylene oxide.

49. The capacitor of claim 48, wherein between substantially six and one hundred percent of repeat units in the polymer are propylene oxide groups.

50. A method for forming an electrolytic capacitor comprising the steps of:

coating a cathode foil with a first coating of a polymerizable material having a crosslinking agent dissolved therein;

curing the first coating;

coating an anode foil with a second coating of a polymerizable material having a salt and a crosslinking agent dissolved therein;

assembling the anode and the cathode to one another in facing relationship to form a capacitor assembly;

curing the second coating.

51. The method of claim 50, wherein the cathode foil has larger dimensions than the anode foil, further comprising the step of enfolding the anode foil within the cathode foil.

52. The method of claim 51, further comprising the step of expelling excess anode coating material by applying pressure.

53. The method of claim 52, wherein pressure is applied by rolling.

54. The method of claim 51, further comprising the step of dissolving a salt in the first coating material before coating the cathode.

55. The method of claim 54, further comprising the step of winding the assembly into a roll.

56. The method of claim 50, further comprising the step of winding the assembly into a roll.

57. The method of claim 50, wherein the cathode foil is a continuous ribbon and the step of curing the first coating is achieved by passing the ribbon through a curing oven.

58. The method of claim 50, wherein the anode foil is a continuous ribbon and the second coating is applied by passing the ribbon through a bath of the polymerizable material.

59. The method of claim 50, wherein the step of assembling the anode and the cathode comprises cowinding the coated anode foil with a ribbon of coated cathode foil.

60. The method of claim 59, further comprising the step of applying pressure to expel excess coating material.

61. The method of claim 60, wherein the pressure is applied with a pressure roller.

65. The method of claim 61, further comprising the step of coating the uncoated foil prior to assembling the foils in facing relationship.

62. A method of forming a capacitor comprising the steps of:

applying a coating to one of an anode foil and an amorphous coating foil, said coating containing a polymerizable material having a salt and a crosslinking agent dissolved therein to form a coated foil and an uncoated foil;

curing the coating; and

assembling the coated foil and the uncoated foil in facing relationship to form a capacitor assembly.

63. The method of claim 62, wherein the anode foil is coated prior to the step of assembling the coated foil and the uncoated foil.

64. The method of claim 62, wherein the cathode foil is coated prior to the step of assembling the coated foil and the uncoated foil.

66. A method of forming an electrolytic capacitor comprising the steps of:

providing a three layer assembly having an anode foil, a cathode foil and a spacer disposed between said anode foil and said cathode foil,

said spacer being ultrathin and having openings occupying at least substantially twenty percent of its volume;

impregnating the assembly with an electrolyte.

67. The method of claim 66, wherein said electrolyte comprises a polymerizable material.

68. The method of claim 67, further comprising dissolving a salt in said polymerizable material.

69. The method of claim 67, further comprising adding a plasticizer to said polymerizable material.

70. The method of claim 67, further comprising polymerizing the electrolyte.

71. A capacitor comprising

an anode foil;

a cathode foil,

an ultrathin spacer having openings therein occupying at least substantially twenty percent of its volume;

an electrolyte impregnated into said openings in said spacer.

72. The capacitor of claim 71, wherein said spacer is comprised of isotactic polypropylene.

73. The capacitor of claim 72, wherein said spacer has a thickness of less than 25 μ

.

74. The capacitor of claim 72, wherein said spacer has a microporous structure.

75. A capacitor comprising:

an anode;

a cathode

a crosslinked polymer electrolyte disposed between said anode and said cathode;

a sealed housing for containing said anode, said cathode and said polymer electrolyte, substantially all space in said housing being occupied by said anode, said cathode and said electrolyte.

76. A capacitor comprising:

an anode;

a cathode;

a crosslinked polymer electrolyte disposed between said anode and said cathode;

a sealed housing for containing said anode, said cathode and said solid polymer electrolyte, said housing being devoid of an expansion chamber for said electrolyte.

77. A capacitor comprising:

an anode;

a cathode;

a crosslinked polymer electrolyte disposed between said anode and said cathode;

a sealed housing for containing said anode, said cathode and said polymer electrolyte, said housing being entirely occupied by said anode, said cathode and said electrolyte except for a longitudinally extending passageway therein.

78. The capacitor of claim 77, further comprising a hollow forming member for defining said passageway and wherein said anode and said cathode are rolled about said forming member.

79. A compact electrolytic capacitor including an electrically conductive anode, an electrically conductive cathode, and an electrolyte between said anode and said cathode;

characterized in that the electrolyte is in the form of an ultrathin layer of a solution of (a) at least one salt selected from the group consisting of organic ammonium salts, zinc salts, cadmium salts, mercury salts and thallium salts of (b) at least one acid selected from the group consisting of monobasic, dibasic and tribasic acids other than haloid acids (c) in an ionically conductive carrier of high solvation power.

80. A compact electrolytic capacitor including an electrically conductive anode, an electrically conductive cathode, and an electrolyte between said anode and said cathode;

characterized in that the electrolyte is in the form of an ultrathin layer of a solution of (a) at least one salt selected from the group consisting of organic ammonium salts, zinc salts, cadmium salts, mercury salts and thallium salts of (b) at least one acid selected from the group consisting of monobasic, dibasic and tribasic acids other than haloid acids (c) in a carrier of high solvation power;

said capacitor having a breakdown voltage which is increased by at least five percent for a given construction due to action of said electrolyte.

81. A compact electrolytic capacitor including an electrically conductive anode, an electrically conductive cathode, and an electrolyte between said anode and said cathode;

characterized in that the electrolyte is in the form of an ultrathin layer of a solution of (a) at least one salt selected from the group consisting of organic ammonium salts, zinc salts, cadmium salts, mercury salts and thallium salts of (b) at least one acid selected from the group consisting of monobasic, dibasic and tribasic acids other than haloid acids (c) in a carrier of high solvation power;

said capacitor having a capacitance which is increased by at least five percent for a given anode construction due to action of said electrolyte.

82. A compact electrolytic capacitor including an electrically conductive anode, an electrically conductive cathode, and an electrolyte between said anode and said cathode;

characterized in that the electrolyte is in the form of an ultrathin layer of a solution of (a) at least one salt selected from the group consisting of organic ammonium salts, zinc salts, cadmium salts, mercury salts and thallium salts of (b) at least one acid selected from the group consisting of monobasic, dibasic and tribasic acids other than haloid acids (c) in a carrier of high solvation power;

said capacitor undergoing, under given elevated temperature and time conditions, only minimal deforming of its dielectric layer.

83. The capacitor of claim 82, wherein said elevated temperature of 60°

C. and said deforming is less than substantially four percent.

84. The capacitor of claim 83, wherein said deforming takes place over a time of at least 1,000 hours.