WO2007101003A2

WO2007101003A2 - High energy density capacitor in a hermetically sealed flexible case and method of manufacturing

Info

Publication number: WO2007101003A2
Application number: PCT/US2007/062398
Authority: WO
Inventors: Joachim Hossick-Schott
Original assignee: Medtronic Inc
Current assignee: Medtronic Inc
Priority date: 2006-02-28
Filing date: 2007-02-20
Publication date: 2007-09-07
Anticipated expiration: 2008-08-28
Also published as: WO2007101003A3; US20070188980A1; US7474521B2

Abstract

A capacitor including a flexible case and method for manufacturing the same are provided. The capacitor includes an electrode assembly encased in a sealed flexible case. The electrode assembly includes an anode formed from a high surface area valve metal and a cathode operatively positioned relative to the anode. The flexible case may conform to an exterior contour of the electrode assembly.

Description

HIGM ENERGY DENSITY CAPACITORS AND METHOD OF

MANUFACTURING TECHNICAL FIELD

The invention relates generally to capacitors, and, in particular, to electrolytic capacitors containing valve metal anodes including a flexible case and methods for making the same.

BACKGROUND

Electrolytic capacitors are typically provided with a metal encasement for enclosing an anode, cathode, liquid electrolyte and a separator materia! positioned between the anode and cathode. The metal encasement is provided with feedthroughs through which the anode and cathode leads extend to facilitate electrical connection to other circuit components. The encasement also includes a fill port to accommodate filling the capacitor with a liquid electrolyte The encasement typically includes a case and a cover that ia welded to the case to hermetically seal tile capacitor

Electronic devices, particularly implantable medical devices, are becoming physically smaller, often with increased functionality. Accordingly, it is desirable to reduce the internal space required for capacitors included in such devices. Some degree of packaging inefficiency is generally associated with a metal encasement The metal encasement may not conform to the space available for the capacitor formed by the contours of the electronic device housing and other internal components. Additional features of the encasement such as the feedthroughs and fill port can require additional space and a minimum encasement thickness. A header space is often provided to accommodate additional features as well as facilitate welding of the cover to the case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. l is a top view depicting a partially-assembled electrode assembly for use in a high-energy density capacitor.

FIG. 2 is a top view of the fully-assembled electrode assembly shown in FlG i and a flexible case for encasing the electrode assembly.

FiG. 3 is a top plan view of a capacitor cell including a flexible case. FIGs. 4A through 4C illustrate a method for encasing a capacitor cell including a flexible case according to an alternative embodiment of the invention.

FIG 5 is a side sectional view of a capacitor cell including a flexible case

FlG. 6 is a side sectional view of an alternative capacitor cell including a flexible case.

FIG. 7 is a top, open view of the capacitor cell shown in FΪG. 6.

FICJ 8 is a flow chart summarizing steps included in a method for manufacturing a valve metal capacitor including a flexible case.

FIG. 9 is a side sectional view of an alternative embodiment of a valve metal capacitor having a solid electrolyte and a flexible case.

FIG. 10 is a flow chart summarizing a method for fabricating a valve metal capacitor having a solid electrolyte and flexible case

DETA I LED DESCRI PTlON In the following description, references are made to illustrative embodiments for cany ing out the invention It is understood that other embodiments may be utilized without departing from the scope of the invention. For purposes of clarity, the same reference numbers are used in the drawings to identify similar elements. The drawings are provided to illustrate various embodiments of the invention and are not drawn to scale FlG ! is a top view depicting a partially-assembled electrode assembly for use in a high- energy density capacitor An anode 12 is provided as a porous "slug" or "pellet" type anode formed from a pressed, sintered and formed valve metal powder. For example, anode 12 may be formed from tantalum or niobium powder. Anode 12 could also be provided as a stack of die-cut porous sheets, for example etched Al sheets All anodes are coated with a dielectric so as to hold electronic charge at high potential differences with low leakage currents. Anode 12 is shown having a generally uniform, cylindrical shape, however, anode 12 may be provided with other geometries having variable contours or surfaces. Mold parts used to form anode 12 may have convex, concave irregular, curved or geometric features formed therein to impart a desired shape to anode 12. The selected valve metal is pressed into a desired shape in a mold and heated in a pressure vacuum

Valve metal anodes having various shapes and surfaces and methods of manufacture are generally disclosed in U.S. Pat. Pub. No. 2004/0134874, hereby incorporated herein by reference in its entirety

The formed anode 12 is typically anodized in an electrochemical process involving immersing the anode in an anodizing electrolyte and applying an electrical formation potential to grow an anodic oxide layer to a target thickness Methods for anodizing valve metal anodes of the porous slug type are generally taught in U.S. Pat. No. 6,802,95 ! , hereby incorporated herein by reference in its entirety.

Slug-type anode 12 is typically provided as a single anode. An electrically insulated anode lead 20 extends from anode 12. Anode lead 20 is typically pressed into anode 12 at the time that anode 12 is formed. Further processing of the anode will depend upon the choice of electrolyte, a liquid electrolytic or a solid polymeric electrolyte. The use of a solid polymeric electrolyte will be further described below. If a liquid electrolyte is used, anode lead 20 is electrically insulated using a sleeve or tube formed from an insulating material that is non-reacti\ e with the capacitor cell electrolyte, such as polyethylene, polytetrafluoroetSiylene, polyvinylidene fluoride, or other tluoropoiymers.

Anode 12 is wrapped in a separator 18. Separator 18 is disposed between anode 12 and cathode 14 to prevent internal electrical short circuit conditions while allowing sufficient movement of a liquid electrolyte within the capacitor. Separator 18 may be formed from one or more layers of a paper material or impregnated paper material such as kraft paper or manila paper. Separator materials may alternatively be formed from one or more layers of a porous polymeric material, such as polyproplylene or PTfE, or fabric gauze material. Separator 18 may be an elongated sheet of one or more layers of separator material or formed into a pouch or "envelope" for wrapping around anode 12. In some embodiments, separator 18 is sealed to enclose anode 12. The cathode 14 is provided as a carbon material deposited on a substrate 16

Substrate 16 includes an outer surface 26 and an inner surface 24 Substrate 16 is depicted as a single piece of material having a "left-hand" portion 50 and a "right-hand" portion 52. Substrate 16 is folded over anode 12 in a "clam-shell" manner to position cathode 14 adjacent to anode 12, with separator 18 interposed there between A carbonaceous material is deposited on inner surface 24 of both the left hand portion 50 and right hand portion 52 of substrate 16 to provide cathode material on both sides of anode 12 (separated by separator 18) Alternatively, substrate 16 may be provided as two separate halves, each having cathode material deposited on an inner surface, and each half stacked with the separator-wrapped anode 12 positioned there between In alternate embodiments, othei cathode materials raa\ be selected for deposition on substrate 16, for example ruthenium oxide Cathode substrate 16 is prov ided as a thin flexible, electrically conductive material, such as a foil or a woven or non-woven mesh Appropriate materials for substiate 16 include, but are not limited to. titanium, aluminum, nickel, tantalum, niobium, or alloys thereof Substrate 16 may alternative!) be formed from a conductive polymer Substrate 16 may be formed to incorporate a cathode lead extension 22a extending there from In some embodiments, a second cathode lead extension 22b is provided extending from the left hand portion 50 such that when substiate 16 is folded ovei anode 12, cathode lead extension 22a and cathode lead extension 22b are aligned and ma> be twisted or pressed together to form a cathode lead Alternatively, a cathode lead may be electrically coupled, for example spot welded, to substrate S 6 The carbon material used to from cathode 14 may be printed, stamped, or pressed, onto substrate 16 or applied using laser deposition, chemical \ apor deposition or any other appropriate method Formation of cathode 14 on substrate 16 may include applying more than one laver of carbon-containing material and may include an annealing step The annealing step may be used to promote adherence of cathode 14 to substrate 16, form a metal carbide with the underlying metal substrate 16, and/or vapori/e an> sohent or p\ roli/e any polymer present in the carbon source

The carbon source may include any foim of carbon, including graphite, a carbon polymorph, carbon black, and carbon nanotube material The carbon source is provided in any medium suitable for the selected deposition process, such as an ink, ribbon, powder. solution, or polymeric materia! Materials and techniques used for depositing a carbon coating onto a metallic substrate are generally disclosed in U S Fat Pub No 2005/0090108, hereby incorporated herein by reference in its entirety The total amount of the anode and cathode material required in the cell will depend on the energy density, volume, voltage, current, energy output, and other requirements of the cell for a particular application

FIG 2 is a top view of the electrode assembly 10 and a flexible case 30 The completed electrode assembly H) is depicted with substrate 16 positioned around the anode 12 wrapped in separator 18 (as shown in FIG 1 ), so as to opcratively position the cathode S 4 (shown in FKJ 1 ) adjacent to anode 12 insulated anode lead 20 and a cathode lead 22 extend from the respecth e electrodes Insulation on cathode lead 22 is optional Λ flexible case 30 is adapted to receh e electrode assembly 10 In the embodiment shown, flexible case 30 is shown as a pouch or envelope having an open side 36 for receh ing electrode assembly 10 Flexible case 30 may altemathely be formed in a clam-shell configuration that is folded over electrode assembly 10 or in two pieces that are stacked with electrode assembly 10 positioned there between and then sealed along all borders flexible case 30 is formed from a leak-proof, conformable material that is non-reacti\e \\ ith the selected electroh te to be used in the cell Appropriate case materials include, but are not limited to, latex, polypropylene, polyethylene, polytetrafluorυethylene, poly vin\ lidene fluoride, or other fluoropoh mers and combinations thereof The thickness of case 30 is selected to provide the durability required for a particular application to prevent puncture, tearing, or rupture of ease 30 during manufacturing of the capacitor cell, during handling of the cell in subsequent electronic device assembly processes, and throughout the expected functioning life of the cell Case 30 is kept as thin as possible while meeting application specific durability requirements in order to provide a highly volumetiicallv efficient capacitor cell In one example, the case mav be formed of a flexible material on the order of 10 mil in thickness Electrode assembh 10 is inserted into flexible case 30 as indicated

arrow 31

Flexible case 30 is prov ided with an anode lead

32 and a cathode lead sleeve 34 While the anode lead 20 and cathode lead 22, and corresponding anode lead sleeve 32 and cathode lead sleev e 34. are shown ha\ ing a particular orientation with respect to the electrode assembly 10, it should be apparent to a skilled artisan that numerous orientations or configurations are possible I he anode and cathode lead orientations wi 11 be design choices associated with the arrangement of other electronic circuitry used with the capacitor cell and the required electrical connections to be made to the capacitoi cell

FIG 3 is a top plan view of the assembled capacitor cell including a flexible case After inserting electrode assembly 10 into flexible case 30, case 30 may be filled with a liquid eleetroh te Flexible case 30 is hermetically sealed along seal area 38 Flexible case

30 is typically sealed using heat, though othei methods such as methods employing pressure or an adhesive may be used Any excess case material 30 remaining after scaling case 30 mav be trimmed away

Flexible case 30 is

ided with a size and shape that generally corresponds to the outer dimensions of electrode assembly SO to achieve high \ oluractric efficiency In some embodiments, flexible case 30 is formed from an elastic material, such as Latex, such that it may be sti etched ova electrode assembly 10 and cicatcs a tightly-fitting encasement that con form s to the geometry of electrode assembly !0 Flexible case 30 may alternatively be formed of a heat-shrinkable material such that after electrode assembly 10 is properly placed in case 30, application of heat causes case 30 to shrink and snugly conform to electrode assembly 10

Seal 40 is provided between anode lead sleeve 32 and anode lead 20, and seal 42 is pro\ided between cathode lead sleeve 34 are cathode lead 22 A hermetic seal is required in case a liquid electrolyte is being used If a solid polymeric electrolyte is being used, a hermetic seal may not be required Seals 40 and 42 røa\ be formed along an\ portion of anode lead sleeve 32 and cathode lead sleeve 34, respectively Seals 40 and 42 may be formed using sealing members 46 and 48, which may be provided as tie wraps, wires or other members adapted for tightly securing the anode and cathode lead sleeves 32 and 34 around the respective leads 20 and 22 to form hermetic seals 46 and 48 Seals 40 and 42 ma\ alternativeh be formed by applying heat to seal and or shrink the lead sleeves 32 and 34 around respecth e leads 20 and 22 Seals 40 and 42 may alternatively be formed by- applying an adhesive or epoxy between the sleex es 32 and 34 and the respective leads 20 and 22

In an embodiment requiring a liquid electrolyte, one of the lead slee\es 32 or 34 may be used to provide access for filling capacitor cell 100 with a liquid electrolyte Λlternath ely, eel I 100 may be fi lied \s ith a liquid electro!) te through the same opening through which electrode assembly 10 is inserted, prior to sealing case 30 along seal area 38 Seal area 38 may be partially sealed leaving an opening for filling cell 100 with an electrolyte, the opening being scaled after electrolyte delivery is complete In yet another embodiment, a fill slee\e 44 may be provided for delivering a fluid electroly te into cell 100 hill sleexe 44 is sealed along seal area 45 after filling is completed and any excess

SIC-CΛ c material ma\ then be removed, as indicated by the dash-dot line Manufacture of capacitor cell 100 docs not require welding as normally required m past practice for closing a metal case and cover and sealing fill ports or other openings of a metal capacitor cell encasement A header space to accommodate welding of m eta! encasements and additional encasement features such as fill ports and insulated lead feedthroughs that increase the o\ eral I encasement volume are not required

FIGs 4A through 4C illustiate a method for encasing a capaciioi cell including a flexible case according to an alternative embodiment of the invention In FIG 4 A, electrode assembK 10 is positioned on an elongated sheet 70 of case material, which is then folded along a fold line 72 over electrode assembly 10 As shown in KIG 4B, the sheet 70 is hermeticalK sealed along a seal area 74 around electrode assembly 10 In MG

4C the excess material of sheet 70 has trimmed away to from case 78, which is sealed on all sides of electrode assembly 10 Seal area 74 ma> extend over anode lead 20 and cathode lead 22 to form leak-proof seals^* around the leads 20 and 22 Alternatively, case 78 ma\ be sealed around leads 20 and 22 in a separate step When sheet 70 is provided as a heat-shrinkafale material, a subsequent step of applying heat may be used to shrink case

78 to conform to the exterior contour 28 of electrode assembK 10, therein forming a high! N volumetricalh efficient capacitor case

FKJ 5 is a side sectional

of a capacitor cell including a flexible case The anode 12 is wrapped by separator 18 Cathode 14 is deposited on substrate 16, and substrate Io is positioned around separator 18 such that cathode 14 and anode 12 are operati\ely positioned relative to each other The electrode assembly 10 is enclosed in flexible case 30, which is hermetically sealed as described above Flexible case 30 is filled with a liquid electroMe

FIG 6 is a side sectional view of an alternative capacitor cell including a flexible case In capacitor cell 150, flexible ease 120 encases the anode 12 and cathode 126 and provides the substrate 124 on which cathode 126 is formed Case 120 is provided as a laminate having at least two layers including an innei metallic inner layer 124 which forms the substrate for cathode 126 Cathode 12o is provided as a carbon containing material deposited on metallic inner layer 124 according to methods described previously Metallic inner layer 124 is thin enough to maintain flexibility of case 120 Metallic inner layer 124 is laminated to a leak-proof, flexible outer Save? 122 formed, foi example, from latex, poly prop) I ene. polyethylene, PTFI-, or combinations of these materials or other elecfrolytic resistant materials Case 120 is generally sized to match the exterior contour S 25 of anode 12, wrapped m separator I S and is generally not highly elastic or heat- shrinkable since significant stretching or shrinking of case 120 may dislodge or breakaway- portions of cathode 126 deposited on metallic inner layer 124 Case 120 is hermetically sealed along seal area 128 Seal area !2S may be provided without metallic inner layer

124 such that outer layer 126 can be hermetically sealed using thermal, pressure, adhesive or other appropriate sealing methods

FIG 7 is a top, open view of the capacitor cell shown in FlG 6 Case 120 is depicted having a "clam shell^" configuration for folding over anode 12, wrapped in a separator 18. Anode 12 is provided with an insulated anode lead 20 extending there from.

Case 120 is formed from a flexible, laminated material including an outer layer 122 and metallic inner layer 124. Outer layer 122 is formed from a leak-proof, electrolyte-resistant flexible material. Outer layer 122 has an inner surface 140 arid an outer surface 142. Metallic inner layer 124 is provided as a suitable foil or woven or non-woven mesh that is laminated onto inner surface 140. Suitable material for metallic inner layer 124 include titanium, aluminum, nickel, platinum, iridium or alloys thereof. Cathode 126 is deposited on the metallic inner layer 124 Metallic inner layer 124 may be formed with cathode lead extensions 130a and 130b, which become aligned when case 120 is folded over anode 12 Alternatively, a cathode lead may be welded to inner metallic layer 124. In an alternate embodiment that includes a solid electrolyte, metallic inner layer

124 may he prov ided for contacting the solid electrolyte functioning as a cathode A solid electrolyte cell will be described further below.

Case 120 is hermetically sealed along seal area 128, extending along the periphery of case 120. Outer layer 122 may optionally include anode lead sleeve extensions 150a and 150b and cathode lead sleeve extensions 152a and 152b The sleeve extensions 150a,

150b, 1 52a and 152b become hermetically sealed around the respective anode lead 20 and cathode lead extensions 130a and 130b (forming a cathode lead) either during sealing along seal area 128 or in a separate sealing step as generally described above

As described previously, the anode or cathode sleeve extensions may serve as a fill sleeve for delivering a liquid electrolyte. Alternatively, a separate fill sleeve may he provided or the liquid electrolyte may be injected through the case using a hypodermic needle The fill sleeve or puncture formed by a h\ podermic needle are hermetically sealed after delivering the electioivte into capacitor cell 150

FIG 8 is a flow chart summarizing steps included in a method for manufacturing a valve metal capacitor including a liquid eSectioiyte and a flexible case At block 205, the valve metal anode is formed as a slug-type anode b> pressing, sintering a selected valve metal powder The anode could also be formed from a stack of high surface aiea sheets, for example etched Λl sheets Λll anode representations are coated with a dielectric The anode is wrapped in a separator at block 210 If a liquid electron te design is used, a carbon-containing cathode or other appropriate cathode material is formed on a cathode substrate at block 215 In one embodiment, the cathode substrate is provided as a metallic foil or a woven or non-woven metallic mesh material thai is wrapped aiound Ui e anode- separator subassembly at block 220 The flexible case is then positioned around the electrode assembly, including the anode, cathode and separator, at block 225 The flexible case may be provided as a pouch or em elope that the electrode assembh is inserted into The fiesiblc case may alternative!)' be provided as sheet of material that is folded over the electrode assembly or two sheets of materia! stacked with the electrode assembh positioned there between

In another embodiment requiting a liquid electrolyte 111!, the cathode substrate is provided as an inner metallic la\er of a laminated case material such that the steps of positioning the cathode around the anode-separator subassembK (block 220) and positioning the flexible case around the electrode assenibK (block 225) are achieved in a single step

At block 230 the flexible case is filled with a liquid electrolyte, and at block 235 the case is hermetically sealed In some embodiments, the flexible case ma> be partially sealed, the liquid electrolyte

and then the case complete!) sealed Sealing the flexible case ma> be performed in a single step or in multiple steps which may include sealing anode and cathode lead

es and sealing an opening through which the electrolyte has been delivered Sealing the flexible case may include applying heat, pressure, an adhesive and/or a sealing member such as a tie wrap, wire, or a heat shrinkable member

An additional step of applying heat to the hermetically sealed case ma> be performed at block 240 to shrink the case to conform to the exterior contour of the elccfrode assembly when the case is fabricated from a hcat-shrinkable material Any excess case materia! mav be lemoved ai block 245

FIG 9 is a side sectional view of an alternative embodiment of a

metal capacitor having a solid e!ectrol>te and a flexible case Electrode assembly 3 !0 includes a porous, slug-type, or stacked-plate-iy pe \ ah e rneia! anode 312 coupled to anode lead 320 as described

\\ hen used in a solid electrolyte cell 300 The formed porous anode 312 is impregnated with a liquid conductive polymer to form solid electrolyte 318 deposited in the pores of anode 314 Electrode contacting 3 14 is provided as a conductive material, such as siKer and/or graphite paste, formed on a conductive substrate 316 A cathode lead 322 is electriealK coupled to contacting 314 via substrate 316 to provide electrical connection to the solid electrolyte The use of a solid polymeric electrolyte, such as PEDT (poh 3,4- cthylenedioxythiophenej, replaces the liquid electrolyte and eliminates the need for a separate cathode The solid pol\ meric electrolyte together with appropriate contacting pro\ ides the functionality of the electrolyte and the cathode \ separator material is also not necessary for separating the anode and cathode as described previous!) with regard to liquid electro! N tc cells

FKJ 10 is a flow chaπ summarizing a method for fabricating a valve metal capacitor having a solid electrolyte and flexible case The use of a solid electrolyte rna> simplify the construction of cell 300 in that liquid electrolyte fiihng is not required, and case 330 may not require hermetic sealing At Mock 405. a porous or

valve metal anode is formed as described previous!} At block 410, the anode is filled with a liquid polymer electrolyte which, after polymerization, forms the solid electrolyte At block 415, a conductive material is formed on a substrate for providing electrical contacting Wύh the solid electrolyte The contact is positioned over the pohraeri/.ed electrolyte at block 420 to operative!} couple the solid electrolyte with a cathode lead as shown in FIG 9

Λ block 425 the flexible case is positioned around the electrode assembly , including the substrate and contact formed thereon The flexible case is sealed at block 430 Additional steps of applying heat to shrink the flexible case and trimming aw ay any excess case material ma\ be performed at block 435 and 44 Thus, a valve metal capacitor including a flexible case and method for manufacturing the same have been presented in the foregoing description with reference Io specific embodiments It is appreciated that \ aήous modifications to the referenced embodiments may be made without departing from the scope of the invention as set forth in the following claims.

Claims

S \ capacitor, comprising an electrode assembly having an exterior contour, the electrode assembly comprising an anode formed from a high surface area vahe metal and a cathode operative!) positioned reiaine to the anode, and a flexible case for encasing the electrode asserabl) , the flexible case being hermeticali) sealed

2 The capacitor of claim 1 w herein the flexible case conforms to the exterior contour of the electrode assembly

3 I^'he capacitor of claim 1 wherein the flexible case includes one of an elastic material and a heai-shrinkable material

4 The capacitor of claim 1 wherein the flexible case includes_* any of polypropylene, polyethylene, latex and a ffuoropolyrner

5 The capacitor of claim I v\ herein the cathode includes a solid polymei

(> The capacitor of claim 5. wherein the sohd polymer being impregnated in the formed anode

7 The capacitor of claim 1 wherein the cathode includes a cathode material deposited on a conductive substrate

8 The capacitor of claim 7 wherein the conductive substrate includes any of a foil, a woven mesh, and a non-woven mesh

9 The capacitor of claim 7 wherein the cathode substrate includes am of titanium, aluminum, tantalum, niobium, nickel and a conductive polymer I ϊ

10. The capacitor of claim 7 wherein the cathode substrate includes a cathode lead extending there from.

1 1 . The capacitor of claim 5 further including a conductive contact operative!}/ positioned relative to the solid polymer and a cathode lead electrically coupled to the conductive contact and extending therefrom

12. The capacitor of claim ! wherein the flexible case includes an anode lead sleeve and a cathode lead sleeve extending there from.

S3 The capacitor of claim 1 wherein the flexible case being sealed using any of beat, pressure, an adhesive, and a sealing member.

S 4 The capacitor of claim 9 wherein the sealing member includes any of a tie wrap, a wire, a band, and a heat-shrmkable member.

15. The capacitor of claim 1 wherein the flexible case includes a laminated material including a flexible outer layer and a metallic inner layer and wherein the metallic inner layer forms the cathode substrate

16. The capacitor of claim I wherein the anode is formed as a slug-type anode.

i 7. A method for fabri cati ng a capacitor, compri sing: forming an anode, the anode being formed from a high surface area valve metal; forming a cathode in operative relation to the anode, the anode and cathode forming an electrode assembly; positioning the electrode assembly in a flexible case; and sealing the flexible case.

18. The method of claim 17 wherein forming the cathode comprises depositing a cathode material on a cathode substrate - M-

1 ^c> The method of claim 18 further including filling the flexible case with a liquid electrolyte

20 The method of claim ! 7 wherein forming the cathode includes impregnating the anode with a liquid conductive pol\ trier

21 The method of claim i 7 wherein the flexible case includes one of an elastic material and a heat-shrinkable material

22 The method of claim 17 further including inserting an anode lead through an anode lead sleeve and inserting a cathode lead through a cathode lead sleeve, the anode and cathode lead sleeves being included on the flexible case, and sealing the anode and cathode lead sleeves

23 The method of claim 1 7 further including applying heat to shrink the flesiblc case to conform to an exterior contour of the electrode assembly

24 The method of claim S 7 v\ herein sealing the case includes any of applying heat, applying pressure, applying an adhesive, apphing a sealing member

25 I he method of claim 17 wherein the flexible case being formed from a laminate including an outer flexible layer and an inner metallic layer, the innei metallic layer forming a substrate for one of a cathode and a cathode contact

26 I he method of clai m 17 further including remos ing excess case materia! after sealing the flexible case

The method of claim 17 wherein forming the anode includes forming a slug-t\ pe pellet of valve metal material