Abstract:
A battery having an electrode assembly located in a housing that efficiently utilizes the space available in many implantable medical devices is disclosed. The battery housing provides a cover and a shallow case a preferably planar, major bottom portion, an open top to receive the cover opposing the bottom portion, and a plurality of sides being radiused at intersections with each other and with the bottom to allow for the close abutting of other components located within the implantable device while also providing for efficient location of the battery within an arcuate edge of the device. The cover and the shallow case being substantially hermetically sealed by a laser weld technique and an insulator member disposed within the case to provide a barrier to incident laser radiation so that during welding radiation does not impinge upon radiation sensitive component(s) disposed within the case.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 11/565,306, filed on Nov. 30, 2006 entitled “CONTOURED BATTERY FOR IMPLANTABLE MEDICAL DEVICES AND METHOD OF MANUFACTURE” which is a continuation of application Ser. No. 10/260,625, filed on Sep. 30, 2002, entitled CONTOURED BATTERY FOR IMPLANTABLE MEDICAL DEVICES AND METHOD OF MANUFACTURE, both of which are herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of batteries for implantable medical devices. More particularly, the present invention relates to volumetrically efficient batteries for implantable medical devices. 
       BACKGROUND OF THE INVENTION 
       [0003]    Implantable medical devices are used to treat patients suffering from a variety of conditions. Examples of implantable medical devices are implantable pacemakers and implantable cardioverter-defibrillators (ICDs), which are electronic medical devices that monitor the electrical activity of the heart and provide electrical stimulation to one or more of the heart chambers, when necessary. For example, a pacemaker senses an arrhythmia, i.e., a disturbance in heart rhythm, and provides appropriate electrical stimulation pulses, at a controlled rate, to selected chambers of the heart in order to correct the arrhythmia and restore the proper heart rhythm. The types of arrhythmias that may be detected and corrected by pacemakers include bradycardias, which are unusually slow heart rates, and certain tachycardias, which are unusually fast heart rates. 
         [0004]    Implantable cardioverter-defibrillators (ICDs) also detect arrhythmias and provide appropriate electrical stimulation pulses to selected chambers of the heart to correct the abnormal heart rate. In contrast to pacemakers, however, an ICD can also provide pulses that are much stronger and less frequent. This is because ICDs are generally designed to correct fibrillations, which is a rapid, unsynchronized quivering of one or more heart chambers, and severe tachycardias, where the heartbeats are very fast but coordinated. To correct such arrhythmias, an ICD delivers a low-, moderate-, or high-energy shock to the heart. 
         [0005]    Pacemakers and implantable defibrillator devices are preferably designed with shapes that are easily accepted by the patient&#39;s body while minimizing patient discomfort. As a result, the corners and edges of the devices are typically designed with generous radii to present a package having smoothly contoured surfaces. It is also desirable to minimize the volume occupied by the devices as well as their mass to further limit patient discomfort. As a result, the devices continue to become thinner, smaller, and lighter. 
         [0006]    In order to perform their pacing and/or cardioverting-defibrillating functions, pacemakers and ICDs must have an energy source, e.g., at least one battery. Known high current power sources used in implantable defibrillator devices employ deep, prismatic, six-sided rectangular solid shapes in packaging of the electrode assemblies. Examples of such deep package shapes can be found in, e.g., U.S. Pat. No. 5,486,215 (Kelm et al.) and U.S. Pat. No. 6,040,082 (Haas et. al.). While these prismatic cases have proven effective for housing and electrically insulating the electrode assemblies, there are volumetric inefficiencies associated with deep prismatic cases. 
         [0007]    One volumetric problem associated with deep prismatic cases is the excess volumetric size of the implantable medical device caused by placing these prismatic batteries within the contoured implantable medical device. As stated above, implantable medical devices are preferably designed with shapes that are easily accepted by the patient&#39;s body and which also minimize patient discomfort. Therefore, the corners and edges of the devices are typically designed with generous radii to present a package having smoothly contoured surfaces. When the deep prismatic battery is placed within the contoured implantable device, the contours of these devices do not necessarily correspond and thus the volume occupied within the implantable device cannot be optimally minimized to further effectuate patient comfort. 
         [0008]    Another volumetric problem associated with deep prismatic cases is the excess volume within the headspace. In a typical implantable device battery the headspace houses the electrode connector tabs, feedthrough pin, insulators, and various other connection components. In typical deep battery cases, the battery case has a prismatic top and then descends downward with possibly curved sides to a bottom. Thus while deep cases could provide for slightly contoured sides it could not provide for contours all throughout the battery case. Thus as shown in  FIG. 13 , the battery case would have to extend above the electrode assembly to accommodate the electrode connector tabs, feedthrough pin, etc. This is volumetrically inefficient since all that technically needs to extend from the top of the electrode assembly is the electrode connector tabs and the feedthrough pin. This inefficiency is due to manufacturing limitations, which make it difficult to create several curved surfaces in deep battery cases. 
         [0009]    Although the use of curved battery cases in implantable devices is known, they are typically found in devices requiring only low current discharge such as pacemakers as described in U.S. Pat. No. 5,549,985 and U.S. Pat. No. 5,500,026. However, these batteries used thin, flat-layered electrodes that do not package efficiently within curved cases, thus contributing to volumetric inefficiencies. Batteries with curved cases have been used in connection with the high current batteries required for, e.g., implantable defibrillator devices. However, as discussed above, the curvature of these battery cases is limited due to manufacturing limitations associated with deep cases. 
         [0010]    For the foregoing reasons, there is a need for a contoured, low profile battery for implantable medical devices, which allows for shape flexibility in the design of the battery to match the contours of an implantable device and fit within the available device space thus providing for a reduction in the volume of the implantable device. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The present invention comprises various embodiments which provide solutions to one or more problems existing in the prior art respecting efficient battery case design for implantable medical devices. Among the problems in the prior art is the lack of a battery case design for use with electrode assemblies that can be: (1) efficiently packaged within an arcuate edge of the implantable device housings, (2) substantially reduces the amount of volume utilized within the implantable medical device and (3) provides flexibility in the placement of the feedthrough pin. 
         [0012]    Accordingly, it is an object of the invention to provide a battery having a high surface area electrode assembly housed in a case that efficiently utilizes the space available within many implantable medical devices. 
         [0013]    Battery housings in embodiments of the invention may include one or more of the following features: (a) a cover, (b) a shallow case having a (preferably) planar bottom portion, an open top to receive the cover; and at least two sides being radiused at intersections with the bottom, (c) a feedthrough assembly providing electrical communication between at least one electrode and implantable medical device circuitry, (d) a coupling providing electrical communication between the feedthrough assembly and the at least one electrode, (e) an insulator adjacent to the cover providing a barrier between an electrode assembly and the cover, (f) an insulator adjacent to the case providing a barrier between the electrode assembly and the case, and (g) a headspace portion extending from a portion of one of the sides. 
         [0014]    Batteries in one or more embodiments of the present invention may include one or more of the following features: (a) an electrode assembly including an anode and a cathode, (b) an electrolyte, (c) a battery housing enclosing the electrode assembly and within which the electrode assembly and the electrolyte are disposed, the housing comprising a cover, a shallow case having a (preferably) planar bottom portion, an open top to receive the cover; and a plurality of sides being radiused at intersections with each other and with the bottom, (d) a headspace region extending from a portion of one of the plurality of sides, (e) a feedthrough assembly providing electrical communication between at least one electrode and implantable medical device circuitry, (f) a coupling providing electrical communication between the feedthrough assembly and the at least one electrode, (g) an insulator adjacent to the cover providing a barrier between an electrode assembly and the cover, (h) and an insulator adjacent to the case providing a barrier between the electrode assembly and the case. 
         [0015]    Implantable defibrillator devices in one or more embodiments of the present invention may include one or more of the following features: (a) a device housing comprising at least one arcuate edge, (b) a capacitor disposed within the device housing, (c) a battery disposed within the device housing and operatively connected to the capacitor, the battery comprising an electrode assembly, and an electrolyte (d) a hermetically sealed battery housing within which the electrode assembly and the electrolyte are disposed, the housing comprising a cover, a shallow case having a (preferably) planar bottom, an open top to receive the cover; and at least two sides being radiused at intersections with the bottom wherein the radiused sides of the battery case nests within one of the arcuate edges of the device housing, (e) a headspace region extending from a portion of one side, and (f) a feedthrough assembly providing electrical communication between at least one electrode and implantable medical device circuitry. 
         [0016]    Methods of manufacturing batteries for implantable medical devices according to the present invention may include one or more of the following steps: (a) providing a shallow battery case having an open end, a base located opposite the open end, and a plurality of sides being radiused at intersections with each other and the base, (b) inserting an electrode assembly into the battery case, (c) placing a cover over the open end of the case, and hermetically sealing the cover to the case, and (d) placing an electrolyte inside the battery case. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is an exploded perspective view of a battery according to the present invention; 
           [0018]      FIG. 2  is a bottom profile of a battery case embodiment of the present invention; 
           [0019]      FIG. 3  is a side profile battery case embodiment of the present invention; 
           [0020]      FIG. 4  is cutaway side profile of several attachment embodiments between a battery cover and a battery case; 
           [0021]      FIG. 5  is a side elevated perspective of a battery case liner of the present invention; 
           [0022]      FIG. 6  is a front profile of an electrolyte fillport embodiment of the present invention; 
           [0023]      FIG. 7  is a side elevated perspective of an electrode assembly embodiment of the present invention; 
           [0024]      FIG. 8  is a side elevated perspective of an insulator cup embodiment of the present invention; 
           [0025]      FIG. 9  is a top profile of a battery cover with a header assembly of the present invention; 
           [0026]      FIG. 10  is a side profile of a battery cover with a header assembly of the present invention; 
           [0027]      FIG. 11  is a front profile embodiment of a feedthrough assembly of the present invention; 
           [0028]      FIG. 12  is a cutaway view of a headspace embodiment showing the feedthrough pin connection with the coupling; 
           [0029]      FIG. 13  is an elevational, exploded pictorial view of the headspace in prior art implantable medical device batteries; 
           [0030]      FIG. 14  is an elevated perspective of a headspace insulator embodiment of the present invention; 
           [0031]      FIG. 15  is a rear profile perspective of a headspace insulator embodiment of the present invention; 
           [0032]      FIG. 16  is an exploded perspective view of battery insulators and connector; and 
           [0033]      FIG. 17  is an elevated side profile of a battery connector embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    The following detailed description is to be read with reference to the drawings, in which like elements in different drawings have like reference numerals. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Skilled artisans will recognize that the examples provided herein have many useful alternatives that fall within the scope of the claimed invention. 
         [0035]    The present invention is not limited to implantable cardioverter defibrillators and may be employed in many various types of electronic and mechanical devices for treating patient medical conditions such as pacemakers, defibrillators, neurostimulators, and therapeutic substance delivery pumps. It is to be further understood; moreover, the present invention is not limited to high current batteries and may utilized for low or medium current batteries. For purposes of illustration only, however, the present invention is below described in the context of high current batteries. 
         [0036]    As used herein, the term battery (or batteries) include a single electrochemical cell or cells. Batteries are volumetrically constrained systems in which the components in the case of the battery cannot exceed the available volume of the battery case. Furthermore, the relative amounts of some of the components can be important to provide the desired amount of energy at the desired discharge rates. A discussion of the various considerations in designing the electrodes and the desired volume of electrolyte needed to accompany them in, for example, a lithium/silver vanadium oxide (Li/SVO) battery is discussed in U.S. Pat. No. 5,458,997 (Crespi et al.). Generally, however, the battery must include the electrodes and additional volume for the electrolyte required to provide a functioning battery. 
         [0037]    The present invention is particularly directed to high current batteries that at least with respect to ICDs are capable of charging capacitors with the desired amount of energy, preferably about 20 joules or more, typically about 20 joules to about 40 joules, in the desired amount of time, preferably about 20 seconds or less, more preferably about 10 seconds or less. These values can typically be attained during the useful life of the battery as well as when the battery is new. As a result, the batteries must typically deliver up to about 5 amps at about 1.5 to about 2.5 volts, in contrast to low rate batteries that are typically discharged at much lower currents. Furthermore, the preferred batteries must be able to provide these amounts of energy repeatedly, separated by about 30 seconds or less, more preferably by about 10 seconds or less. 
         [0038]    With reference to  FIG. 1 , a preferred battery according to the present invention is depicted. Battery  10  is comprised of a battery case  12  ( FIG. 2 ), electrode assembly  14 , insulator cup  16 , battery cover  18 , coupling  20 , headspace cover  22 , feedthrough assembly  24 , and battery case liner  31 . The battery case  12  is designed to enclose the electrode assembly  14  and be hermetically sealed with battery cover  18 . 
         [0039]    With reference to  FIGS. 2 &amp; 3 , a bottom and side profile respectively is shown of a battery case. Battery case  12  is comprised of battery space  30  which houses electrode assembly  14 , headspace  32 , fillport  34 , which allows for the input of electrolyte into battery  10 , and open end  29 . Battery case  12  is preferably generally arcuate in shape where sides  26  meet with top  28  of battery case  12 . This construction provides a number of advantages including the ability to accommodate the curved or arcuate ends of a preferred coiled electrode assembly  14 . As will be more fully discussed below, the arcuate sides  26  can also nest within the arcuate edges of an implantable medical device such as an implantable cardiac defibrillator. 
         [0040]    Battery case  12  is preferably made of a medical grade titanium, however, it is contemplated that battery case  12  could be made of almost any type of material, such as aluminum and stainless steel, as long as the material is compatible with the battery&#39;s chemistry in order to prevent corrosion. Further, it is contemplated that shallow battery case  12  could be manufactured from most any process including but not limited to machining, casting, stamping, milling, so-called rapid prototyping techniques (e.g., using an SLA and the like) thermoforming, injection molding, vacuum molding, etc., however, case  12  is preferably manufactured using a shallow drawing process. Headspace  32  houses insulators and connector tabs, which transfer electrical energy from electrode assembly  14  to the implantable medical device circuitry and will be discussed in more detail below. However, as shown in  FIG. 2 , a significant amount of headspace is reduced from prior battery assemblies such as the one shown in  FIG. 13 . 
         [0041]    With reference again to  FIG. 3 , lip  27  is utilized to hold battery cover  18  in place not allowing cover  18  to drop within battery case  12 . Further, lip  27  provides protection to electrode assembly  14  during the welding process, which is preferably performed by laser welding, however, other methods of attachment are contemplated. For example, resistance welding, brazing, soldering and similar techniques may be employed and/or adhesive materials may be used to couple the cover  18  to the case  12 . Lip  27  provides a shelf or ledge designed to reduce the likelihood of, if not completely prevent, a portion of radiation emitted from the laser beam from penetrating battery case  12  and damaging radiation sensitive components therein. This would be especially true if this shelf were not present and a gap between cover  18  and case  12  were present there would exist a large risk that electrode assembly  14  could be damaged by a laser penetrating the gap and causing heat damage to electrode assembly  14 . 
         [0042]    With reference to  FIG. 4 , several cutaway side profiles of attachment embodiments between a battery cover and a battery case are shown. In profile A, lip  27  is cut at 90° to provide even more protection during the welding process. While more protection is typically desired, the 90° lip  27  of profile A can be difficult to manufacture. In profile B, lip  27  is bent outward and then preferably cover  18  is placed overtop and butt welded to case  12 . In profile C, lip  27  is also bent outward, however, in profile C, a crimp  25  is utilized to help prevent a laser beam from penetrating battery case  12 . In profile D, lip  27  is eliminated and the outer edge of cover  18  is bent over before being welded to case  12  to help prevent the laser from penetrating case  12  during welding. In profile E, the outer edge of case  12  is bent over top of cover  18  before being welded. In profile F, cover  18  simple rests upon the upper edge of case  12  and then is butt welded together. In profile G, the upper edge of case  12  is bent slightly inward with cover  18  resting upon to be butt welded to case  12 . Each of these embodiments is meant to provide protection to electrode assembly  14  during the welding process, which is preferably performed by laser welding, however, other methods of attachment are contemplated. Each embodiment is meant to prevent the welding laser beam (represented by the arrow in the Figure) from penetrating battery case  12  and damaging electrode assembly  14 . Further, the term welding can encompass many types of attachment such as resistance welding and brazing, however, all welds are preferably laser welds. It is also contemplated that many types of attachment could be utilized without departing from the spirit of the invention. 
         [0043]    As discussed above, traditional battery cases were deep cases wherein the opening to the case was perpendicular to the deepest portion of the battery. There are two major drawbacks to this traditional design. First, there are manufacturing limitations to the amount of curvature, which can be implemented into the case. Therefore, most cases would have a substantially prismatic case, which, as discussed above, is very limiting when packaging the case within the implantable medical device. Second, because the headspace exists at the open end of the case, it consumes an entire side of the case. In contrast to deep cases, battery case  12  is manufactured using a shallow form process, which allows for corners of case  12  to be radiused as well as providing for the possibility of many varying shapes of case  12 . By doing so, the volume case  12  occupies is substantially reduced. Further, because battery case  12  can be manufactured with various shapes and contours, a substantial amount of headspace room can be eliminated and thus more volume within the implantable medical device can be reduced. The inventors of the present invention have found a reduction in excess of on the order of about 10%. 
         [0044]    With reference to  FIG. 5 , a battery case liner used to isolate the battery case from the electrode assembly is shown. Case liner  31  is preferably comprised of ETFE and has a thickness of 0.013 cm. (0.004 inches), however, other thicknesses and types of materials are contemplated such as polypropylene, silicone rubber, polyurethane, fluoropolymers, and the like. Case liner  31  preferably has substantially similar dimensions to battery case  12  except that case liner  31  would have slightly smaller dimensions so that it can rest inside of battery case  12 . From the case liner&#39;s shape as shown in  FIG. 5  and the battery case&#39;s shape as shown in  FIG. 2 , it is clear to one of skill in the art how case liner  31  would rest within battery case  12 . For example, the headspace area of case liner  31  would line up with headspace  32  of battery case  12  except it would be slightly smaller to accommodate for fillport  34 . 
         [0045]    With reference to  FIG. 6 , a front profile of the electrolyte fillport is shown with a fillport ball seal and a closing button. Fillport  34  is used to route lithium hexafluoroarsenate electrolyte into battery  10 . Although lithium hexafluoroarsenate is preferably used for the present embodiment, it is contemplated that most any chemical electrolyte could be used without departing from the spirit of the invention. Fillport  34  is preferably laser welded to battery case  12  and preferably has a hermetic seal to ensure no electrolyte leakage. However, it is contemplated that fillport  34  could be attached to case  12  in any fashion, such as any suitable hermetic joint as is known to those of skill in the art. Fillport  34  is preferably comprised of titanium and has a diameter of 0.1117 inches at the top and 0.060 inches at the bottom, however, it is fully contemplated that fillport  34  could be most any thickness or type of electrochemically compatible material. However, for the ease of manufacturing and reliability of the weld, case  12  and fillport  34  are preferably made from the same material. 
         [0046]    From the figure it is shown that fillport  34  has an opening  36  in which to receive an electrolyte injection device that transfers electrolyte from the device to battery  10  through conduit  38 . Further, it is shown that the upper portion of fillport  34  is tapered so that fillport  34  can rest within an opening in case  12  before fillport  34  is welded to case  12 . It is of note that the opening in case  12  for fillport  34  does not necessarily have to be located in headspace  32  and can be located anywhere in case  12  or cover  18  without departing from the spirit of the invention. Once the electrolyte has been injected within battery  10 , fillport ball seal  35  is placed within conduit  38  to create a “press-fit” hermetic seal, which prevents any electrolyte from escaping through conduit  38 . Closing button  37  is then placed over aperture  33  and is welded to fillport  34 . Closing button  37  is preferably comprised of medical grade titanium and ball seal  35  is preferably comprised of a titanium alloy of titanium aluminum and vanadium, however, other materials and alloys are contemplated as long as they are electrochemically compatible. It is further shown in the figure that fillport  34  is tapered from the top to the bottom. This provides for maximum space inside battery  10 , further the taper provides a larger upper area for button  37  to be welded to, which allows for button  37  to be larger and thus easier to handle and weld to fillport  34 . 
         [0047]    With further reference to  FIG. 6 , it is shown that fillport  34  extends entirely from case  12  to cover  18 . Since case  12  and cover  18  are preferably 0.038 cm. (0.015 inches) thick, fillport  34  provides support by extending from case  12  to cover  18  so that an indentation or denting does not occur during the “press-fit” operation where ball seal  35  is pressed within conduit  38 . If fillport  34  did not extend from case  12  to cover  18  there is a risk that denting could occur during the “press-fit” operation due to the thinness of case  12  and cover  18 . Further, distal end  39  of fillport  34  is tapered so that electrolyte can freely enter battery  10 . The taper allows conduit  38  to be unobstructed by cover  18  and thus the injection of electrolyte occurs more easily. 
         [0048]    Other fillport embodiments and locations are contemplated without departing from the spirit of the invention. One embodiment includes a low profile fillport (e.g., one that does not extend from the case to the cover) that is located near the corners of case  12  and cover  18 . In this embodiment, indentation during the “press-fit” is inhibited by the support provided by the sides of case  12  (or cover  18 ) in the corner. Further, this embodiment can be implemented in case  12  or cover  18  as long as the low profile fillport is placed in a corner of the vessel defined by case  12  and cover  18  of the battery  10 . In another fillport embodiment, a filltube is located on case  12  or cover  18 . After the electrolyte is injected into battery  10 , the filltube is crimped shut and welded. This embodiment eliminates the “press-fit” operation. In another embodiment, a plug or button is welded over or into an open port where the electrolyte is injected. This embodiment eliminates a redundant seal. In yet another embodiment, a gasket seal or epoxy is utilized to plug an open port. 
         [0049]    With reference to  FIG. 7 , the details regarding construction of electrode assembly  14 , such as connector tabs, electrode pouches, etc., are secondary to the present invention and will be described generally below with a more complete discussion being found in, e.g., U.S. Pat. No. 5,458,997 (Crespi et al.). With reference to  FIG. 7 , electrode assembly  14  is preferably a wound or coiled structure similar to those disclosed in, e.g., U.S. Pat. No. 5,486,215 (Kelm et al.) and U.S. Pat. No. 5,549,717 (Takeuchi et al.). However, electrode assembly  14  could be a folded or stacked electrode assembly structure. The composition of the electrode assemblies can vary, although one preferred electrode assembly includes a wound core of lithium/CSVO. Other battery chemistries are also anticipated, such as those described in U.S. Pat. No. 5,616,429 to Klementowski and U.S. Pat. No. 5,458,997 to Crespi et al., with the preferred cores comprising wound electrodes. Such a design provides a volumetrically efficient battery useful in many different implantable devices. 
         [0050]    Electrode assembly  14  preferably includes an anode, a cathode, cathode connector tabs  40 , anode connector tab  41 , and a porous, electrically non-conductive separator material encapsulating either or both of the anode and cathode. These three components are wound to form electrode assembly  14 . The anode portion of the electrode assembly can comprise a number of different materials including an anode active material located on an anode conductor element. Examples of suitable anode active materials include, but are not limited to: alkali metals, materials selected from Group IA of the Periodic Table of Elements, including lithium, sodium, potassium, etc., and their alloys and intermetallic compounds including, e.g., Li—Si, Li—B, and Li—Si—B alloys and intermetallic compounds, insertion or intercalation materials such as carbon, or tin-oxide. Examples of suitable materials for the anode conductor element include, but are not limited to: stainless steel, nickel, titanium, or aluminum. However, in a preferred embodiment the anode is comprised of lithium with a titanium conductor. 
         [0051]    The cathode portion of the electrode assembly preferably includes a cathode active material located on a cathode current collector that also conducts the flow of electrons between the cathode active material and the cathode terminals of electrode assembly  14 . Examples of materials suitable for use as the cathode active material include, but are not limited to: a metal oxide, a mixed metal oxide, a metal sulfide or carbonaceous compounds, and combinations thereof. Suitable cathode active materials include silver vanadium oxide (SVO), copper vanadium oxide, combination silver vanadium oxide (CSVO), manganese dioxide, titanium disulfide, copper oxide, copper sulfide, iron sulfide, iron disulfide, carbon and fluorinated carbon, and mixtures thereof, including lithiated oxides of metals such as manganese, cobalt, and nickel. However, in a preferred embodiment the cathode is comprised of CSVO with a titanium conductor. 
         [0052]    Preferably, the cathode active material comprises a mixed metal oxide formed by chemical addition, reaction or otherwise intimate contact or by thermal spray coating process of various metal sulfides, metal oxides or metal oxide/elemental metal combinations. The materials thereby produced contain metals and oxides of Groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table of Elements, which includes noble metals and/or their oxide compounds. 
         [0053]    The cathode active materials can be provided in a binder material such as a fluoro-resin powder, preferably polytetrafluoroethylene (PTFE) powder that also includes another electrically conductive material such as graphite powder, acetylene black powder, and carbon black powder. In some cases, however, no binder or other conductive material is required for the cathode. 
         [0054]    The separator material should electrically insulate the anode from the cathode. The material is preferably wettable by the cell electrolyte, sufficiently porous to allow the electrolyte to flow through the separator material, and maintain physical and chemical integrity within the cell during operation. Examples of suitable separator materials include, but are not limited to: polyethylenetetrafluoroethylene, ceramics, non-woven glass, glass fiber material, polypropylene, and polyethylene. 
         [0055]    As best seen in  FIG. 1 , an insulator cup  16  is used to electrically isolate electrode assembly  14  from battery cover  18 . With reference to  FIG. 8 , an insulator cup embodiment of the present invention is shown. Insulator cup  16  includes slits  44 ,  46 , and  48  to accommodate connector tabs  40  and anode tab  41 . Preferably insulator cup  16  is comprised of ETFE with a thickness of 0.030 cm. (0.012 inches), however, it is contemplated that other thicknesses and materials could be used such as HDDE, polypropylene, polyurethane, fluoropolymers, and the like. Insulator cup  16  performs several functions including working in conjunction with battery case liner  31  to isolate battery case  12  and battery cover  18  from electrode assembly  14 . It also provides mechanical stability for electrode assembly  14 . In addition, it serves to hold the coil assembly together which substantially aids in the manufacturing of battery  10 . Since electrode assembly  14  is preferably a wound coil, insulator cup  16  also helps prevent assembly  14  from unwinding. Insulator cup  16  further provides protection for assembly  14  during handling and during the life of assembly  14 . Finally, and most importantly cup  16  provides a thermal barrier between assembly  14  and cover  18  during the laser welding procedure that joins cover  18  with case  12 , which is discussed in more detail below. 
         [0056]    As stated above in detail, case  12  and cover  18  are preferably welded together to provide a hermetic enclosure for electrode assembly  14 . However, because of the battery&#39;s structure, the weld is performed within 1 mm of electrode assembly  14 . Since, case  12  and cover  18  are first assembled before the welding process, a finite gap between case  12  and cover  18  typically exists. However, any time there is a finite gap there is the possibility that the laser beam utilized in the laser welding process may penetrate battery  10  and damage electrode assembly  14 . Therefore, molded insulator cup  16  is preferably comprised of ETFE and further is preferably compounded or mixed with carbon black, although cup  16  may be simply coated with carbon black in lieu of the foregoing. The carbon coloring serves to make the insulator black. The black color serves to shield electrode assembly  14  from laser beam penetration into battery  10 . Essentially cup  16  is opaque to the laser wavelength, which is approximately 1 micron. Alternatively, this thermal protection could be accomplished with a metal ring compatible with case  12  and cover  18 , such as titanium, stainless steel, niobium, etc., however, preferably cup  16  is an opaque polymer as discussed above. 
         [0057]    With reference to  FIGS. 9 and 10 , a top and side profile of a battery cover with a feedthrough assembly is shown. Battery cover  18  is comprised of an electrode assembly region  60 , a headspace region  62 , and a feedthrough aperture  64 . Similar to battery case  12 , battery cover  18  is comprised of medical grade titanium to provide a strong and reliable weld creating a hermetic seal with the battery case. However, it is contemplated that battery cover  18  could be made of any type of material as long as the material was electrochemically compatible. Battery cover  18  is designed to fit overtop the shallow opening  29  within lip  27  on the perimeter of opening  29 . Therefore battery cover  18  rests on the small lip, substantially flush with the top of opening  29  which provides for substantial ease of manufacturing when battery cover  18  is laser welded to battery case  12 . 
         [0058]    Feedthrough aperture  64  is tapered outwardly not only to allow feedthrough assembly  24  to rest within aperture  64 , but also to provide an isolation buffer between glass member  72  and the weld which will attach feedthrough assembly  24  to battery cover  18 . With reference to  FIG. 11 , an embodiment for the feedthrough assembly is shown. Feedthrough assembly  24  is comprised of feedthrough pin  70 , glass sealing member  72 , ferrule  74 , flange  76 , and retention slots  78 . As is shown in the figure, ferrule  74  is tapered at a substantially equal angle as the tapers on feedthrough aperture  64  so that it may be received within aperture  64 . This tapered portion of ferrule  74  is also the location where the weld to join feedthrough assembly  24  to battery cover  18  occurs. The taper of ferrule  74  not only places the weld further from glass member  72 , but also creates more surface area in which to dissipate the heat from the weld. As is discussed above, feedthrough aperture  64  and assembly  24  can be located anywhere on case  12  or cover  18 . 
         [0059]    Feedthrough pin  70  is preferably comprised of niobium, however, any conductive material could be utilized without departing from the spirit of the invention. Niobium is preferably chosen for its low resistivity, its material compatibility during welding with titanium, and its coefficient of expansion when heated. As will be discussed in more detail below, pin  70  is preferably welded to coupling  20  ( FIG. 12 ) and to connector module  100  ( FIG. 17 ) located outside of battery  10 . Coupling  20  and contacts  114  and  116  on connector module  100  are preferably made of niobium and titanium respectively. Niobium and titanium are compatible metals, meaning that when they are welded together a strong reliable weld is created. Pin  70  has a diameter of 0.055 cm. (0.0216 inches), preferably selected for a high current application. Glass sealing member  72  is comprised of CABAL-12 (calcium-boro-aluminate) glass, which provides electrical isolation of feedthrough pin  70  from battery cover  18 . The pin material is in part selected for its suitability in feedthrough assembly  24  for its ability to join with glass sealing member  72 , which results in a hermetic seal. 
         [0060]    CABAL-12 is very corrosion resistant as well as being a good insulator. Therefore, CABAL-12 provides for good insulation between pin  70  and battery cover  18  as well as being resistant to the corrosive effects of the electrolyte. Preferably glass member  72  provides an electrical insulation resistance of 1000 M-ohms from pin  70  to ferrule  74  at 100 VDC per Mil-STD 202F method  302 . Glass member  72  is then preferably placed within a conduit on ferrule  74  having a diameter of 0.060 inches. Preferably glass member  72  provides a hermetic seal both with pin  70  and ferrule  74  having a leak rate not exceeding 10 −8  ATM STD cc/sec of helium per MIL-STD 202F method  112 E. Ferrule  74  is preferably comprised of medical grade titanium that is annealed according to ASTM F67. Although, preferable materials have been listed for the components listed above, it is contemplated that other materials could be utilized. Feedthrough pin  70 , sealing member  72 , and ferrule  74  are heated together to allow the glass to melt and reform to seal within ferrule  74  and around pin  70 . 
         [0061]    After pin  70 , glass member  72 , and ferrule  74  are placed together; the bottom of ferrule  74  is subjected to an overmolding process where it is coated with polypropylene to provide electrical insulation between pin  70  and ferrule  74 . The polypropylene overmold helps prevent pin  70  from being bent over to touch ferrule  74  thus creating an electrical short. The overmolding also provides mechanical short protection for other situations, such as pin  70  bending to bridge to connector tabs  40  and  41 . Further, the polypropylene coating limits the amount of electrolyte exposure to glass member  72 . It is contemplated that other insulation materials could be used as a coating such as PETFE (polyethylene tetra fluoro ethylene), ETFE (ethylene tetrafluorethylene), polyurethane, polyethylene, and the like. The polypropylene molding is held in place by retention slots  78 , which act to prevent the molding from twisting off or pulling away from feedthrough assembly  24 . Further, during the overmolding process flange  76  is created. Flange  76  provides a retention means for headspace insulator  22  ( FIG. 14 ), which is discussed in more detail below. Preferably flange  76  has a thick plastic-thin plastic-thick plastic design, which allows for insulator  22  to be snapped onto flange  22 . 
         [0062]    In another embodiment, the overmolding is extended out over a plate with slots for cathode tabs  40 . Tabs  40  are then welded to the plate, which in turn is welded to feedthrough pin  70 . This embodiment provides a relatively rigid system, which has advantages of preventing insulators from inadvertently folding or collapsing out of place. 
         [0063]    With reference to  FIG. 12 , an embodiment showing the interconnection between a feedthrough pin and a coupling is shown. As is shown, coupling  20  is welded to cathode tabs  40  while anode tab  41  is in contact with battery cover  18 . Coupling  20  is preferably comprised of niobium with a diameter of 0.055 cm. (0.0216 inches), which is compatible with pin  70 . Coupling  20  is welded to feedthrough pin  70  to provide an electrical connection between the cathode of electrode assembly  14  and the implantable medical device. While for the purposes of this discussion coupling  20  is welded to cathode tabs  40  and feedthrough pin  70 , it is contemplated that an alternate method of attachment may be utilized such as soldering, electrically conductive glue, or an electrically conductive thermoset material and the like, without departing from the spirit of the invention. At the time of the present invention, however, the inventors have found that welding provides the most reliable connection. Coupling  20  allows for ease in manufacturing by eliminating the need to bend tabs  40  or pin  70  to reach a coupling between them. Since coupling  20  has a “U” shape it allows for more compliance in aligning with the position of tabs  40  and pin  70 . 
         [0064]    What is further shown with reference to  FIG. 12  is that the headspace volume is substantially reduced when compared with prior implantable medical device batteries as shown in  FIG. 13  and as discussed above. 
         [0065]    With respect to  FIG. 14 , a headspace insulator is shown. Preferably headspace insulator  22  is comprised of polypropylene, however, other insulative materials are contemplated. Headspace insulator  22  preferably covers coupling  20  and cathode tabs  40 . Insulator  22  is designed to provide mechanical line of sight insulation and electrical protection from electrical shorts. Insulator  22  also prevents any materials from contacting cathode tabs  40  and coupling  20 , which could compromise the battery&#39;s operation. With reference to  FIG. 15 , which shows a rear profile view of the headspace insulation, slot  90  is shown, which snaps onto flange  76  of feedthrough assembly  24 . This connection holds insulator  22  into place and protects cathode tabs  40  and coupling  20  during handling and discharge. 
         [0066]    With reference to  FIG. 16 , a battery assembly with insulators and a battery connector is shown. Upon battery  10  being mechanically assembled as described in detail above, a battery connector  100  is connected to pin  70 , which is described in more detail below. Connector  100  is utilized to route the energy from battery  10  to the implantable medical device. In an implantable cardioverter defibrillator the energy would be transferred to a switching system such as that described in U.S. Pat. No. 5,470,341 (Kuehn et al.). Battery insulators  104  and  106  are held in place on battery  10  with two pressure sensitive acrylic adhesive strips  102 . These strips are similar to double back adhesive tape, which is tacky on both sides of the tape. While pressure sensitive acrylic is discussed for purposes of the embodiment, it is fully contemplated that other methods of attachment for insulators  104  and  106  could be utilized without departing from the spirit of the invention. 
         [0067]    Insulators  104  and  106  are preferably comprised of a thermoplastic polyimide film, however, other insulator materials are contemplated. Insulators  104  and  106  provide electrical and mechanical insulation for battery  10 . Since battery case  12  and cover  18  are negatively charged, they need to be electrically isolated from the rest of the implantable medical device. Further, insulators  104  and  106  provide mechanical insulation by protecting battery  10  during handling and thermal protection when the implantable device shields are welded together, which is outside the scope of the present invention. 
         [0068]    With reference to  FIG. 17 , a battery connector is shown. Connector  100  is comprised of a main body  110 , a base  112 , a positive contact  114 , and a negative contact  116 . Main body  110  provides a housing for base  112 , positive contact  114 , and negative contact  116  and is preferably comprised of polyetherimide, however other insulator materials are contemplated. Body  110  also acts as an insulator to electrically isolate positive contact  114  from negative contact  116 . Base  112 , positive contact  114 , and negative contact  116  are preferably comprised of titanium, however other materials are contemplated. Connector  100  is placed over top of pin  70  in which pin  70  is received by an aperture in positive contact  114 . Pin  70  is then preferably laser welded to positive contact  114  as well as base  112  which is laser welded to cover  18 . What cannot be shown with reference to  FIG. 17  is that negative contact  116  is in contact with base  112 . Thus after the laser welding is complete there exists a positive charge on contact  114  and a negative charge on contact  116 . Positive contact  114  and negative contact  116  are then ribbon bonded, as is known in the art, to the implantable medical device&#39;s circuitry. It is of note that connector  100  is the only exposed portion of battery  10  after it is received through triangular cut  108  as shown in  FIG. 15 . It is further noted that an alternative embodiment would include a negative charge on contact  114  and a positive charge on contact  116 . 
         [0069]    It will be appreciated that the present invention can take many forms and embodiments. The true essence and spirit of this invention are defined in the appended claims, and it is not intended that the embodiments of the invention presented herein (i.e., described and/or illustrated) should limit the scope thereof.