Sintered capacitor electrode including multiple thicknesses

An example includes a capacitor case sealed to retain electrolyte, at least one anode disposed in the capacitor case, the at least one anode comprising a sintered portion disposed on a substrate, an anode conductor coupled to the substrate in electrical communication with the sintered portion, the anode conductor sealingly extending through the capacitor case to an anode terminal disposed on the exterior of the capacitor case with the anode terminal in electrical communication with the sintered portion, a cathode disposed in the capacitor case, a separator disposed between the cathode and the anode and a cathode terminal disposed on an exterior of the capacitor case and in electrical communication with the cathode, with the anode terminal and the cathode terminal electrically isolated from one another.

TECHNICAL FIELD

This document relates generally to energy storage and particularly to sintered electrodes to store energy in an implantable medical device.

BACKGROUND

Capacitors include multiple electrodes that are interconnected to function together to charge with energy and to discharge energy. Capacitor interconnections present several challenges. Interconnections can increase equivalent series resistance, which can decrease energy density. Interconnections can also frustrate assembly, either by machine or by operator, especially if the interconnections include delicate components. Robust interconnection systems and methods that address these challenges can improve capacitors.

SUMMARY

This document discusses apparatus and methods for sintered capacitor electrodes having multiple thicknesses. One embodiment of the apparatus includes a first second and third electrode disposed in a capacitor case. Separator material separates the second electrode form the first and third electrodes. The third electrode includes a first sintered portion of a first thickness and second sintered portion of a second thickness. The second thickness of the third electrode is substantially equivalent to a thickness including the first thickness of the third electrode, the second electrode thickness, the first separator thickness and the second separator thickness. The third electrode is in electrical communication with the first electrode. One or more electrodes couple to terminals extending through the case.

An aspect of this disclosure relates to a method for making a capacitor having electrodes with varying thickness. An embodiment according to the method includes sintering material into an electrode to define a first portion having a first thickness and a second portion having a second thickness, and stacking electrodes into a stack, including stacking the electrode with additional electrodes, the stacking including abutting the second portion with a connection portion of a second electrode, with an electrically isolated electrode disposed between the electrode and the second electrode.

DETAILED DESCRIPTION

This application is for energy storage devices such as capacitors that include interconnections. Some of the embodiments disclosed here intersperse anodes and cathodes in a stack, with electrodes of one polarity sandwiched between two electrodes of another polarity. In such configurations, interconnecting the electrodes of a like polarity can present challenges. One challenge is that interconnecting the electrodes can damage them, such as by bending the electrodes so they are close together to connect with a third interconnection device such as a bus bar, or so that the electrodes abut. Bending the electrodes can increase equivalent series resistance and can physically damage them, such as by kinking them or even snapping them into parts.

The present application sets forth systems and methods that can reduce or eliminate the bending of electrodes. Embodiments use spacers to maintain distance between the electrodes. In some examples, the spacers are formed onto the electrodes themselves, such as by sintering. In some examples, devices such as rivets are used to space the electrodes apart.

FIG. 1is a schematic of a system100such as a medical system including a sintered capacitor, according to some embodiments. The system100represents any number of systems to provide therapeutic stimulus, such as to a heart. Examples of medical systems include, but are not limited to, implantable pacemakers, implantable defibrillators, implantable nerve stimulation devices and devices that provide stimulation from outside the body, including, but not limited to, external defibrillators.

In various embodiments, electronics104are to monitor the patient, such as by monitoring a sensor105, and to monitor and control activity within the system100. In some examples, the electronics104are to monitor a patient, diagnose a condition to be treated such as an arrhythmia, and control delivery of a stimulation pulse of energy to the patient. In some instances, electronics104are powered wirelessly using an inductor. In additional configurations, the electronics104are powered by a battery106. In some examples, electronics104are to direct small therapeutic bursts of energy from the battery106to a patient.

For therapies that use energy discharge rates exceeding what battery106is able to provide, such as defibrillation, a capacitor108is used. Energy from the battery106is controlled by the electronics104to charge the capacitor108. The capacitor108is controlled with the electronics104to discharge to a patient to treat the patient. In some examples, the capacitor108entirely discharges to a patient, and in additional examples is switched on to provide therapeutic energy and switched off to truncate therapy delivery.

Some examples of a system100include an optional lead system101. In certain instances, after implantation, the lead system101or a portion of the lead system101is in electrical communication with tissue to be stimulated. For example, some configurations of lead system101contact tissue with a stimulation electrode102. The lead system101couples to other portions of the system100via a connection in a header103. Examples of the system101use different numbers of stimulation electrodes and/or sensors in accordance with the needs of the therapy to be performed.

Additional examples function without a lead101and are leadless. Leadless examples are positioned in contact with the tissue to be stimulated, or are positioned proximal to a tissue to be stimulated to shock the tissue through intermediary tissue. In some examples, leadless systems are easier to implant and are less expensive as they do not use additional lead components. The housing110is used as an electrode in leadless configurations, in some examples.

In certain embodiments, the electronics104include an electronic cardiac rhythm management circuit coupled to the battery106and the capacitor108to discharge the capacitor108to provide a therapeutic defibrillation pulse. In some examples, the system100includes an anode and a second electrode such as a cathode sized to deliver a defibrillation pulse of at least approximately 50 joules. This energy level is predetermined to achieve a delivered energy level mandated by a governing body or standard associated with a geographic region, such as a European country. In an additional embodiment, the anode and second electrode are sized to deliver a defibrillation pulse of at least approximately 60 joules. This energy level is predetermined to achieve an energy level mandated by a governing body of another region, such as the United States. In some examples, electronics104are to control discharge of a defibrillation pulse so that the medical system100delivers only the energy mandated by the region in which the device100is used.

Packaging anodes and cathodes can reduce their efficiency. Interconnections between conductors coupled to electronics and to the electrodes of the capacitor108decrease efficiency of charging and discharging, for example. Accordingly, anodes and cathodes are sized to compensate for decreases in efficiency. As such, in some embodiments, the capacitor108includes anodes and second electrodes sized and packaged to deliver a defibrillation pulse of at least approximately 50 joules. Some are sized and packaged to deliver a defibrillation pulse of at least approximately 60 joules.

One characteristic of some sintered electrode examples is that at least one anode and a cathode have a DC capacitance that is approximately 23% greater than a AC capacitance for the at least one anode and the second electrode. In some examples, the at least one anode and the second electrode have an AC capacitance of at least 96.7 microfarads per cubic centimeter at 445 total voltage. This is a 30% improvement over an etched capacitor that has 74.5 microfarads per cubic centimeter. Total voltage is the voltage that allows 1 milliamp of leakage per square centimeter. Some examples are aged to 415 volts.

In certain examples, the capacitor108includes a capacitor case112sealed to retain electrolyte. In some examples, the capacitor case112is welded. In some instances, the capacitor case112is hermetically sealed. In additional examples, the capacitor case112is sealed to retain electrolyte, but is sealed with a seal to allow flow of other matter, such as gaseous diatomic hydrogen or a helium molecule. Some of these examples use an epoxy seal. Several materials can be used to form case112, including, but not limited to, aluminum, titanium, stainless steel, nickel, a polymeric material, or combinations of these materials. The case112is sealed to retain electrolyte. Various electrolytes can be used including, but not limited to, Suzuki-Techno Corporation electrolyte model1184. The case112includes a seal, such as a resin based seal including but not limited to epoxy, in some examples. Some examples include a rubber seal to seal case portions to one another, or to seal subcomponents such as a feedthrough to one or more case portion. In some examples, case112is welded together from subcomponents. Some examples include a case that includes one or more backfill ports, but the present subject matter is not so limited.

A hermetically sealed device housing110is used to house components, such as the battery106, the electronics104, and the capacitor108. Hermeticity is provided by welding components into the hermetically sealed device housing110in some examples. Other examples bond portions of the housing110together with an adhesive such as a resin based adhesive such as epoxy. Accordingly, some examples of the housing110include an epoxy sealed seam or port. Several materials can be used to form housing110, including, but not limited to, titanium, stainless steel, nickel, a polymeric material, or combinations of these materials. In various examples, the housing110and the case112are biocompatible.

The capacitor108is improved by the present electrode technology in part because it can be made smaller and with less expense. The improvement provided by these electrodes is pertinent to any application where high-energy, high-voltage, or space-efficient capacitors are desirable, including, but not limited to capacitors used for photographic flash equipment. In other words, present subject matter extends to energy storage devices that benefit from high surface area sintered electrodes including, but not limited to, aluminum. The electrodes described here can be incorporated into cylindrical capacitors that are wound, in addition to stacked capacitors.

FIG. 2is an implanted medical system200, implanted in a patient201, according to some embodiments. The system includes a cardiac rhythm management device202coupled to a first lead204to extend through the heart206to the right ventricle208to stimulate at least the right ventricle208. The system also includes a second lead210to extend through the heart206to the left ventricle212. In various embodiments, one or both of the first lead204and the second lead210include electrodes to sense intrinsic heart signals and to stimulate the heart. The first lead204is in direct contact (e.g., touching) with the right atrium214and the right ventricle208to sense and/or stimulate both those tissue regions. The second lead210is in direct contact with the right atrium216and the right ventricle212to sense and/or stimulate both of those tissue regions. The cardiac rhythm management device202uses the lead electrodes to deliver energy to the heart, between electrodes on the leads or between one or more lead electrodes and the cardiac rhythm management device202. In some examples, the cardiac rhythm management device202is programmable and wirelessly communicates218programming information with a programmer220. In some examples, the programmer220wirelessly218charges an energy storage device of the cardiac rhythm management device202. Other stimulation topologies, such as those that stimulate other portions of the body, additionally benefit from the apparatus, systems and methods disclosed herein.

FIG. 3Ais a plan view of nested sintered capacitor electrodes that have yet to be excised from a substrate, according to some embodiments.FIG. 3Bis a cross section taken along the line3B-3B inFIG. 3A. Electrodes302are sintered onto a substrate304. A first sintered portion310has a thickness of L31. In various embodiments, a second sintered portion308has a thickness L32. In certain examples, the thickness L32is greater than the thickness L31.

In some examples, the web300is used in constructing a capacitor. In additional examples, sintered portions are excised from the web300for use in constructing a capacitor. In some examples, an electrode is cut from the web300on the illustrated perimeters such as perimeter306. In some of these examples, the sintered material is not excised. In additional examples, the sintered material is brushed or smeared by an excision device. In additional examples, an electrode is cut from the web300by cutting around and outside the web300. In these embodiments, foil extends beyond a perimeter of the sintered material. Foil that extends beyond a perimeter of sintered material is used in constructing a capacitor in some examples, such as by interconnecting multiple electrodes by interconnecting their respective foils. Examples of foils used for interconnection are disclosed herein. In various examples, an electrode is cut from the web300by cutting inside the perimeter306, such that sintered material is cut.

In some embodiments, the first portion310and the second portion308are formed with the same sintering process. In additional examples, separate sintering processes are used. In various examples, one or both of the first portion310and the second portion308are formed by one or more processes including, but not limited to, sintering, selective laser sintering, direct metal laser sintering, doping a material with a conductive dopant, forming a portion of a conductive adhesive such as a conductive epoxy and melting a dopant. In some examples, the thickness of one or both of the first portion310and the second portion308is defined using a mechanical process such as planeing, grinding, sanding or another process. The thickness of the first portion and the second portion are controlled within specified manufacturing tolerances so that a stack of electrodes can additionally fall within a specified tolerance. A stack of electrodes having different widths between respective first portions and second portions allows for a side profile of the stack to have a contour defined by varying first portions, while the stack defined by the second portions has a rectangular cross section.

FIG. 4Ais a plan view of a web, according to some embodiments.FIG. 4Bis a cross section taken along the line4B-4B inFIG. 4A. The web includes material408disposed on a substrate404. The substrate404is formed of a metallic foil in various examples. In some examples, the substrate404is an aluminum foil. The substrate404has a thickness of less than 0.008 inches (0.2 mm) in various examples. Some aluminum foils are less than or equal to 0.005 inches thick. These foils are easily bent by hand and are easily torn by hand. Substrates that are thicker are additionally possible. Examples of substrate materials include aluminum, titanium, copper, nickel and alloys thereof. In some examples, the web400is feedable through a reel-to-reel process.

In certain examples the material408is sintered onto the substrate. In various examples, one or both of the first portion406and the second portion402are formed by one or more processes including, but not limited to, sintering, selective laser sintering, direct metal laser sintering, doping a material with a conductive dopant, forming a portion of a conductive adhesive such as a conductive epoxy and melting a dopant. In some examples, the material is sintered to define a first portion406and a second portion402. The first portion406has a thickness L41, and the second portion402has a thickness L42. In some embodiments these thicknesses are equivalent or substantially equivalent (e.g., within a selected manufacturing tolerance). Some embodiments include a first portion406having a thickness that is less than the second thickness402. Optionally, the web400includes sintered material408on a first side of the substrate406and a second sintered material411on a second side of the substrate406. In some embodiments, the second sintered material411includes portions with different thicknesses406′,402′. In some embodiments the thickness of the portions406′,402′ are equivalent or substantially equivalent (e.g., within a selected manufacturing tolerance). It is understood that in embodiments described herein showing an electrode including a substrate with a sintered portion on one side of the substrate, that it is possible to have instead, an electrode including a substrate with sintered material on two sides of the substrate without departing from the scope of the present subject matter.

In some examples the first portion406and the second portion402are continuous and monolithic—a state defined by the sintered material being sintered in a single sintering step such that the metal grains of the first portion406and the second portion402appear uniform when viewed across a boundary between the first portion406and the second portion402.

In some embodiments, the first portion406and the second portion402are formed with the same sintering process. In additional examples, separate sintering processes are used. In various examples, one or both of the first portion406and the second portion402are formed by one or more processes including, but not limited to, sintering, selective laser sintering, direct metal laser sintering, doping a material with a conductive dopant, forming a portion of a conductive adhesive such as a conductive epoxy and melting a dopant. In some examples, the thickness of one or both of the first portion406and the second portion402is defined using a mechanical process such as planeing, grinding, sanding or another process. The thickness of the first portion and the second portion are controlled within specified manufacturing tolerances so that a stack of electrodes can additionally fall within a specified tolerance. A stack of electrodes having different widths between respective first portions and second portions allows for a side profile of the stack to have a contour defined by varying first portions, while the stack defined by the second portions has a rectangular cross section.

FIG. 5Ais a plan view of one or more sintered capacitor electrodes including multiple thicknesses, according to some embodiments.FIG. 5Bis a cross section taken along the line5B-5B inFIG. 5A. The web includes material disposed on a substrate504. The substrate504is formed of a metallic foil in various examples. In some examples, the substrate504is an aluminum foil. The substrate504has a thickness of less than 0.008 inches (0.2 mm) in various examples. Some aluminum foils are less than or equal to 0.005 inches thick. These foils are easily bent by hand and are easily torn by hand. Substrates that are thicker are additionally possible. Examples of substrate materials include aluminum, titanium, copper, nickel and alloys thereof. In some examples, the web500is feedable through a reel-to-reel process.

Certain examples include a material sintered onto the substrate. In certain examples, the material is sintered to define a first portion506and a second portion502. The first portion has a thickness L51, and the second portion has a thickness L52. In some embodiments these thicknesses are equivalent or substantially equivalent (e.g., within a selected manufacturing tolerance). Some embodiments include a first portion having a thickness that is less than the second thickness.

In some embodiments, the first portion506and the second portion502are formed with the same sintering process. In additional examples, separate sintering processes are used. In various examples, one or both of the first portion506and the second portion502are formed by one or more processes including, but not limited to, sintering, selective laser sintering, direct metal laser sintering, doping a material with a conductive dopant, forming a portion of a conductive adhesive such as a conductive epoxy and melting a dopant. In some examples, the thickness of one or both of the first portion506and the second portion502is defined using a mechanical process such as planeing, grinding, sanding or another process. The thickness of the first portion and the second portion are controlled within specified manufacturing tolerances so that a stack of electrodes500can additionally fall within a specified tolerance. A stack of electrodes having different widths between respective first portions and second portions allows for a side profile of the stack to have a contour defined by varying first portions, while the stack defined by the second portions has a rectangular cross section.

FIG. 6Ais a plan view of a capacitor stack, according to some embodiments.FIG. 6Bis a front view of the capacitor stack ofFIG. 6A, illustrating interconnects, according to some embodiments. In some embodiments, the stack600is an anode. To increase surface area of an electrode, several electrodes are positioned against one another. In certain examples, each electrode includes one or more sintered portions disposed on a substrate. A first electrode includes a main portion602and a substrate610. A second electrode includes a second main portion604and a second substrate612, with a second connection portion670additionally disposed on the substrate612. A third electrode includes a third sintered portion606and a third substrate614, with a third connection portion672additionally disposed on the third substrate614. A fourth electrode includes a fourth sintered portion608and a fourth substrate616, with a fourth connection portion674additionally disposed on the substrate616. The present subject matter is not limited to stacks of sintered material and extends to stacks of other materials, such as etched material.

In various examples, the electrodes are interconnected to one another physically and electrically. A stack of first portions650defines a contoured side profile619in some examples. In certain embodiments, a stack of second portions652has a rectangular cross section. Embodiments in which both the first stack and the second stack have a rectangular cross section are possible. Additionally, some examples define a contoured side profile of each of a stack of first portions and a stack of second portions.

In some examples, one or more of the second portions652include additional material to melt during a welding procedure to interconnect multiple electrodes. For example, connection portion670includes weld filler material in some embodiments, the weld filler material to melt and interconnect the substrate610to the substrate612.

In some examples, the electrodes each abut one another and are electrically connected via the abutment. In some examples, the sintered portions are welded to one another using resistance welding, such as by applying a voltage across several electrodes along the axis of stacking. In some examples, several electrodes are interconnected by interconnecting their respective substrates such as by adhesion, welding, fasteners, or combinations thereof. In some examples, substrates are interconnected to define a side profile619such as an edge face. Along the side profile619, interconnection configurations include, but are not limited to, welding (including, but not limited to, laser welding), adhesion fasteners, and combinations thereof. Additionally, the substrates can be resistance welded together such as by pinching and welding.

In the illustrated configuration, a first sintered portion602is sintered onto a first substrate610, and a second sintered portion604is sintered onto a second substrate612. The first substrate610faces the second sintered portion604and abuts it. In additional configurations, the second electrode is flipped, and the first substrate610abuts the second substrate612.

In the illustrated configuration, the plurality of anodes are stacked to a stack height T6, and at least two of the sintered anodes have respective widths, perpendicular to the height T6, that are substantially different such that the plurality of sintered anodes define a contoured edge618, with the contoured edge618extending between a top major face620of a top sintered portion602and a bottom major face622of a bottom substrate616. Various examples have an overall width W6perpendicular to the height T6. In some examples at least two of the sintered anodes have respective lengths, perpendicular to the height T6, that are substantially different such that the plurality of sintered anodes define a side profile619, such as a contoured edge, with the side profile619extending between a top major face620of a top sintered portion602and a bottom major face622of a bottom substrate616. Accordingly, the top major face620and the bottom major face622have different areas. The top major face620and the bottom major face622are substantially parallel. Various embodiments have an overall length L6.

In another configuration, the plurality of electrodes are stacked to a stack height T6, and at least two of the sintered anodes have respective widths, perpendicular to the height T6, that are substantially equal such that the plurality of sintered anodes define a side surface that is substantially parallel to the height T6. In the illustrated configuration, the top major face620and the bottom major face622are shaped similarly, but in additional embodiments, they are shaped differently.

FIG. 7Ais a top view of a capacitor stack, according to some embodiments.FIG. 7Bis a cross section taken along the line7B-7B inFIG. 7A. In various embodiments, a stack750is disposed in a capacitor case701. In some examples, the case701is sealed to retain electrolyte. Examples of seals include welds, gasketed seals such as those using o-rings, adhesives and other seals. In some examples the case701includes a dish portion752and lid portion754.

Various embodiments include a first electrode702disposed in the stack750. In certain examples, a conductor720is coupled to the first electrode702, with the first electrode702in electrical communication with the conductor720. In some examples, the conductor720sealingly extends through the capacitor case701. In some examples, the conductor720forms a terminal724disposed on an exterior726of the capacitor case701, the terminal724to be coupled to a wire harness or other circuitry. In additional embodiments, the conductor720couples to a terminal to be connected to another wire harness or other circuitry. In various embodiments, the terminal724is in electrical communication with the first electrode702.

Various embodiments include a second electrode710that has a second electrode thickness TE2. The second electrode710is in the stack750in some examples. In various embodiments, the second electrode710is disposed in the stack750with the first electrode702. In various embodiments, the second electrode710is sealed into the case701.

The stack750in some examples includes a third electrode703that includes a first sintered portion704, and a substrate705. In some examples, the stack750includes a fourth electrode includes a sintered portion706and a substrate707. Some examples include a fifth electrode that includes a sintered portion708and a substrate709. The present subject matter is not limited to stacks of sintered material and extends to stacks of other materials, such as etched material.

In various embodiments, a first separator728is disposed between the first electrode702and the second electrode710. The separator728has a first separator thickness TS1. Separator contemplated includes Kraft paper. Some examples include one or more electrodes of 0.0005 inch thick Kraft paper, although the present subject matter is not so limited and other separators are used in additional embodiments.

In some examples, a third electrode703is in electrical communication with the first electrode702. In various embodiments, the third electrode703has a first sintered portion704of a first thickness TE31. A second portion756of the third electrode703has a second thickness of TE32. In some examples, the thickness TE32is a thickness other than the first thickness TE31. Various embodiments include a second separator730disposed between the third electrode703and the second electrode710having a second separator thickness TS2. In some examples, one or more of the portion756include filler material to fill space between the substrates that sandwich them, such as by melting during a welding operation to interconnect several electrodes.

Various embodiments include a second terminal760disposed on the exterior726of the capacitor case701. In some examples, the second terminal760is in electrical communication with the second electrode710, with the terminal724and the second terminal760electrically isolated from one another. In various embodiments, the second thickness TE32of the third electrode703is substantially the same as a thickness including the first thickness TE31of the third electrode703, the second electrode thickness TE2, the first separator thickness TS1and the second separator thickness TS2.

Some examples include a plurality of electrodes stacked together touching one another, such as by abutting one another physically. In some of these examples, the electrodes are anodes. Some of these examples are configured such that each of the plurality of electrodes includes a sintered portion disposed on a respective substrate. For example, the third electrode703includes a first sintered portion704and a second sintered portion756, each disposed on a substrate705.

In some examples, electrodes of a plurality of electrodes are electrically interconnected to one another. For example, electrodes703,758and762are stacked together in electrical communication with one another. In various embodiments, portions of these electrodes abut and are in electrical communication with one another. For example, portions756,764and766abut and are in electrical communication with one another. In some examples, a stack of electrodes is constructed in which a first electrode702abuts a third electrode703. In some of these examples, the first electrode702abuts a sintered portion756of the second electrode703. In some examples, the third electrode703includes a substrate705that abuts a sintered portion764of electrode758. In some examples, electrode758includes a substrate707that abuts a sintered portion766of a third electrode762.

FIG. 8Ais a top view of an electrode stack including rivets, according to some embodiments.FIG. 8Bis a front view of the electrode stack ofFIG. 8A, illustrating rivets of different thicknesses, according to some embodiments. In some embodiments, the stack800forms part of a capacitor.

In various embodiments, the stack800includes a first electrode803, a second electrode805, a third electrode807and a fourth electrode809. In some examples, each of these electrodes includes a respective sintered material disposed on a substrate. For example, the first electrode803includes a first sintered material802disposed on a first substrate850. In certain examples, the second electrode805includes a second sintered material804disposed on a second substrate852. In various examples, the third electrode807includes a third sintered material806disposed on a third substrate854. In some examples, the fourth electrode809includes a fourth sintered material808disposed on a fourth substrate856.

In various embodiments, each of the electrodes includes a connection member. For example, the first electrode803includes a first connection member840. In various embodiments, the first connection member840defines an aperture829. In various embodiments, the aperture is an excised portion created by any of a laser, punch, drill or combinations thereof. In various embodiments, disposed in the aperture829is a rivet822. In some examples, the second electrode is coupled with a second rivet828. In some examples, the third electrode is coupled with a third rivet830. In some examples, the fourth electrode is coupled with a fourth rivet832. In various examples, the first rivet822has a first thickness T81. In some examples, the second rivet828has a second thickness T82. In various embodiments, the first thickness T81is different than the second thickness T82, however embodiments in which they are the same or similar (e.g., within a predetermined manufacturing tolerance) form part of the present subject matter.

In various embodiments, the electrodes physically contact one another via their respective rivet. The rivets are stacked into a rivet stack852. In some examples, the thickness of one or more rivets is defined by an excision such as a grinding process. Other excision processes are possible. The present subject matter is not limited to stacks of sintered material and extends to stacks of other materials, such as etched material.

In various examples, the rivets are interconnected to one another mechanically and electrically. In some examples, the rivets each abut one another and are electrically connected via the abutment. In some examples, the rivets are welded to one another using resistance welding, such as by applying a voltage across several rivets, such as along the axis of stacking.

In the illustrated configuration, the plurality of anodes are stacked to a stack height T8, and at least two of the electrodes have respective widths, perpendicular to the height T8, that are substantially different such that the plurality of sintered anodes define a contoured edge818, with the contoured edge818extending between a top major face820of a top sintered material802and a bottom major face823of a bottom substrate816. In various embodiments, the stack800has an overall width W8. In some examples at least two of the sintered anodes have respective lengths, perpendicular to the height T8, that are substantially different such that the plurality of sintered anodes define a contoured edge819, with the contoured edge819extending between a top major face820of a top sintered material802and a bottom major face823of a bottom substrate816. In various embodiments, the stack800has an overall length L8. Accordingly, the top major face820and the bottom major face823have different areas. The top major face820and the bottom major face823are substantially parallel.

In another configuration, the plurality of slugs are stacked to a stack height T8, and at least two of the sintered anodes have respective widths, perpendicular to the height, that are substantially equal such that the plurality of sintered anodes define a side surface that is substantially parallel to the height T8. In the illustrated configuration, the top major face820and the bottom major face823are shaped similarly, but in additional embodiments, they are shaped differently.

FIG. 9is a method of making a capacitor including electrodes having different thicknesses, according to some embodiments. At902, an example method includes sintering material into an electrode to define a first portion having a first thickness and a second portion having a second thickness. At904, an example method includes stacking electrodes into a stack, including stacking the electrode with additional electrodes, the stacking including abutting the second portion with a connection portion of a second electrode, with an electrically isolated electrode disposed between the electrode and the second electrode. Methods are contemplated in which stacking the electrodes includes maintaining the electrode in a planar shape. In certain methods, stacking the electrodes includes maintaining the second electrode in a planar shape. In some methods, stacking includes disposing separator between the electrode and the second electrode. Some methods include etching the second electrode. In some methods sintering material into an electrode includes sintering material onto a substrate. Some methods include riveting a rivet through the substrate to at least partially define the second thickness. Additional methods include sintering material into an electrode includes sintering material onto a web, with one side of the web defining the first thickness and the second portion defining the second thickness. Some methods include excising the electrode from the web. Additional methods include forming the second portion of a conductive epoxy. Some methods include forming the second portion by sintering material and doping the sintered material with a conductive epoxy. Some methods include melting a sintered material into the second portion. Some methods include melting a dopant into the second portion. Some methods include selective laser sintering a material into the second portion. Some methods include direct metal laser sintering a material into the second portion.