Advanced valve metal anodes with complex interior and surface features and methods for processing same

• US 20040134874A1
• Filed: 10/23/2003
• Published: 07/15/2004
• Est. Priority Date: 11/25/2002
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Norton, John D., Rorvick, Anthony W., Hossick-Schott, Joachim, May, Steve J.
• Granted Patent: US 7,342,774 B2
• Time in Patent Office: Days
• US Class Current: 216/13
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: H01G 9/042 characterised by the material H01G11/22 takes precedence
• CPC Class Codes: H01G 9/052 Sintered electrodes
• CPC Class Codes: H01G 9/06 Mounting in containers
• CPC Class Codes: H01G 9/08 Housing; Encapsulation

Abstract

The present invention generally relates to improved capacitors; in particular, the present invention provides advanced valve metal (AVM) anodes and methods for fabricating AVM anodes having complex surface and interior features for use in high energy density capacitors. Such anodes find use in high voltage capacitors incorporated into implantable medical devices (IMDs), among other uses. The AVM anodes may be pressed into virtually any arbitrary shape and may have a gradually changing (or substantially constant) density profile throughout the AVM anode. Such AVM anodes may also be perforated or shaped to receive one or more cathode members. The AVM anodes enhance packaging efficiency for compact high energy density capacitors.

Claims

15. A capacitor apparatus, comprising:

a porous sintered valve metal anode member having at least two cavities formed therein;

a conductive lead wire coupled to the anode member;

at least one cathode member disposed in electrical communication with said anode member; and

a housing means for retaining the anode member and cathode member.

16. An apparatus according to claim 15, wherein the anode member includes one of:

an aluminum material, a tantalum material, a niobium material, a valve metal material, and an alloy comprising at least one valve metal.

17. An apparatus according to claim 16, wherein the cathode member includes one of:

a carbon material, stainless steel material, a carbide material, a titanium material and a ruthenium material; and

said cathode member includes a coat of at least one of;

a carbon layer, a carbide material, a carbonaceous material, a ruthenium oxide, an iron oxide, a nickel oxide, a titanium oxide, a ruthenium carbide, an iron carbide, and a nickel carbide.

18. An apparatus according to claim 15, wherein the at least two cavities comprises at least one surface feature on the anode member and said at least one surface feature comprises:

a ridge, a boss, a channel, a tunnel, a corrugation, a ripple, a groove, a notch, a slot, a furrow, a crease.

19. An apparatus according to claim 15, wherein said cathode member comprises an elongated cathode member and said elongated cathode member is at least partially inserted into one of said at least two cavities, and wherein said cathode member has a core surrounded by a high capacitance material and a separator layer surrounding the high capacitance material

20. An apparatus according to claim 19, wherein the at least one elongated cathode member further comprises a coaxial, nested set of hollow core members, and wherein said core members have a layer of one of the following disposed thereon:

a carbon, a carbide, a metal oxide.

21. An apparatus according to claim 15, wherein said anode member and said cathode member each have major surfaces and the major surface of the anode member is disposed substantially orthogonal to the major surface of the cathode member.

22. An apparatus according to claim 21, further comprising:

a pair of cathode members disposed spaced apart so that the major surfaces of the pair of cathode members are substantially parallel; and

a plurality of anode members disposed between the pair of cathode members and electrically insulated from each adjacent one of said plurality of anode members.

23. An apparatus according to claim 22, wherein at least one of said plurality of anode members has a plurality of apertures formed therein.

24. An apparatus according to claim 23, further comprising at least one layer of porous material disposed between an adjacent pair of anode members.

25. An apparatus according to claim 24, wherein said at least one layer of porous material is an aluminum foil having a lower capacitance value than the anode members.

26. An apparatus according to claim 25, wherein the aluminum foil is mechanically etched with tunnel features oriented substantially parallel to the major surface or substantially orthogonal to the major surface.

45. A capacitor apparatus according to claim 15, wherein said valve metal anode includes a cross-sectional density gradient and a peripheral portion of the valve metal anode is relatively less dense than a central portion of the valve metal anode.

46. A capacitor apparatus according to claim 45, wherein the central portion comprises a substantially uniform shape.

47. A capacitor apparatus according to claim 45, wherein the peripheral portion includes at least one elongated hollow passageway.

48. A capacitor apparatus according to claim 46, wherein the at least one elongated hollow passageway is occupied by a material.

49. A capacitor apparatus according to claim 47, wherein the material is one of:

a material that absorbs liquid electrolyte, a cellulose-based material, a cathode material, a non-woven material, a metallic powder of different density than the density of the peripheral portion.

50. A capacitor apparatus according to claim 49, wherein the metallic powder has a different density than the density of the central portion.

27-1. A method according to claim 1, wherein the subjecting step further comprises delivering the potential pulses to the anode-electrolyte system for a predetermined hold time after achievement of the target formation voltage until the current flow through the anode-electrolyte system has dropped to a predetermined level.

31. A high energy-density valve metal anode, comprising:

a multi-density, layered porous sintered valve metal anode member having a layer of oxide formed on exposed surfaces of the anode member and wherein said valve metal anode has a cross-sectional density profile wherein an outmost layer that is less dense than the density of a central layer of the valve metal anode; and

a conductive lead wire coupled to the anode member.

32. An anode according to claim 31, wherein said central layer has a pair of opposing major planar surfaces and said outermost layer surrounds said central layer so that a portion of the outermost layer abuts the pair of opposing major planar surfaces of the central layer.

33. An anode according to claim 32, wherein said central layer comprises a pressed and sintered layer of metallic material and said outermost layer comprises a perforated structure.

34. An anode according to claim 33, wherein the outermost layer is configured so that for substantially each surface location of said central layer a shortest transport path distance exists with respect to the closest exterior surface location of the outermost layer.

35. An anode according to claim 33, wherein the outermost layer has a substantially planar configuration having a minor thickness dimension approximately equal to the average transport path for each surface location of said central layer.

36. An anode according to claim 31, further comprising an intermediate layer interposed between the central layer and the outermost layer and having a density higher than the density of the central layer and lower than the outermost layer.

37. An anode according to claim 36, wherein said intermediate layer and said outermost layer are perforated with a plurality of passageways and a majority of said passageways fluidly couple opposing major surfaces of said intermediate layer and said outermost layer.

38. An anode according to claim 37, wherein said majority of passageways continuously fluidly couple an exterior surface of said outermost layer to said central layer.

39. An anode member for a high energy density capacitor apparatus, comprising:

a porous sintered valve metal anode member assembly having a central layer, a first layer substantially surrounding said central layer, and a second layer substantially surrounding said first layer, wherein the central layer comprises a high density member, the first layer comprises a lower density member, and said second layer comprises a lowest density member and wherein said central, said first and said second layer are independently pressed and sintered, and then combined and anodized together in a formation electrolyte solution so that a layer of oxide is formed on exposed surfaces of each of said central, said first, and said second layers; and

a conductive lead wire coupled to a portion of said anode member.

40. An anode member according to claim 39, wherein said central layer, said first layer and said second layer include a plurality of apertures formed therein adapted for receiving a plurality of elongated cathode members arranged in an array and wherein the interior of said plurality of apertures are covered with an electrically non-conductive material so that when said elongated cathode members are inserted therein said anode member and said plurality of elongated cathode members are not in direct electrical communication.

41. An anode member according to claim 40, further comprising a relatively different density material disposed in at least one of the plurality of apertures.

42. An anode member according to claim 41, wherein the relatively different density material comprises one of:

a cellulose material, a metallic powder, a non-woven material.