The disclosure generally relates to an electrochemical cell for an implantable medical device, and, more particularly, to a vanadium tab that extends from at least one current collector in an electrochemical cell.
Implantable medical devices (IMDs) detect and deliver therapy for a variety of medical conditions in patients. The human anatomy includes many types of tissues that can either voluntarily or involuntarily, perform certain functions. After disease, injury, or natural defect, certain tissues may no longer operate within general anatomical norms. For example, after disease, injury, time, or combinations thereof, the heart muscle may begin to experience certain failures or deficiencies. Certain failures or deficiencies can be corrected or treated with implantable medical devices (IMDs), such as implantable pacemakers, implantable cardioverter defibrillator (ICD) devices, cardiac resynchronization therapy defibrillator devices, implantable pulse generators (IPGs), neurological stimulation devices, drug administering devices, diagnostic recorders, cochlear implants, and the like.
ICDs typically comprise, inter alia, a control module, a capacitor, and a battery that are housed in a hermetically sealed container with a lead extending therefrom. When therapy is required by a patient, the control module signals the battery to charge the capacitor, which in turn discharges electrical stimuli to tissue of a patient. The battery includes a case, a liner, an electrode assembly, and electrolyte. The liner insulates the electrode assembly from the case. The electrode assembly includes electrodes, an anode (also referred to as a negative electrode) and a cathode (also referred to as a positive electrode), with a separator therebetween. For a flat plate battery, an anode comprises a set of anode electrode plates with a set of tabs extending therefrom. The set of tabs are electrically connected through a connector such as a weld or a jumper pin. Each anode electrode plate includes a current collector with anode material disposed thereon. A cathode is similarly constructed. It is desirable to continue to develop new batteries for IMDs.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers are used in the drawings to identify similar elements.
The present invention is directed to an electrochemical cell such as a battery or a capacitor for an implantable medical device (IMD). One embodiment of the battery, for example, includes electrodes, an anode and a cathode, with a separator therebetween. An electrode includes at least one current collector and/or a tab that comprises vanadium (V) a V alloy, or cladded V. Exemplary V alloys include V-4 chromium (Cr)-4 titanium (Ti) and V-15Cr-5Ti wherein the numerical values are in weight percentages.
A vanadium tab and/or a vanadium current collector in a primary and/or secondary cell or battery helps to minimize adverse affects on magnetic resonance imaging (MRI) associated with medical devices. For example, vanadium does not interfere or exhibits minimal interference with the formation of the MRI image. Moreover, vanadium substantially reduces or eliminates heating of, for example, the battery during the MRI. Additionally, vanadium exhibits a substantially lower corrosion rate (i.e. 70 micro-inches per year) under cell operating conditions compared to conventional materials. Vanadium also exhibits excellent ability to be welded with dissimilar metals compared to conventional tab and/or current collector materials. Vanadium also enhances the reliability of the connection between the battery electrode and the case or the battery electrode and the feedthrough pin.
Principles of the claimed invention apply to a primary cell and/or a secondary cell (also referred to as primary battery or secondary battery). The primary or secondary cells can be configured in a variety of ways. Primary or secondary cells can be configured in a “jelly roll,” such as that which is presented and described relative to
IMD 100 includes a case 102, a control module 104, a battery 106 (e.g. organic electrolyte battery etc.) and capacitor(s) 108. Case 102 comprises a conductive material such as titanium, titanium alloy, stainless steel, or other suitable material. Control module 104 controls one or more sensing and/or stimulation processes from IMD 100 via leads (not shown). “Module” refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality.
Battery 106 includes an insulator 110 (or liner) disposed therearound. Battery 106 charges capacitor(s) 108 and powers control module 104.
Feed-through assembly 118, formed by pin 123, insulator member 113, and ferrule 121, is electrically connected to jumper pin 125B through a weld formed through a set of tabs 128B. Jumper pin 125B may comprise a conductive material such as vanadium, aluminum, nickel, niobium, vanadium alloys. Vanadium can be alloyed with one or more elements to the extent that the V alloy remains a substitutional solid solution, i.e., is free of intermetallic phases. Exemplary V alloys include V-4 chromium (Cr)4 titanium (Ti) and V-15Cr-5Ti wherein the numerical values are in weight percentages. Vanadium can also be cladded with other refractory or non-refractory-type materials. Exemplary refractory materials include chromium, titanium, molybdenum, niobium or columbium, tantalum, tungsten, halfnium and zirconium. Exemplary non-refractory materials include aluminum (Al) 300 series stainless steels or other like material. Vanadium cannot be clad to pure Cr due to Cr being very brittle. Vanadium can be cladded by bonding a vanadium sheet with other metal sheet to form a layered structure. Exemplary cladding processes include cold and/or hot rolling or explosive bonding. The connection between pin 123 and jumper pin 125B allows delivery of positive charge from electrode assembly 114 to electronic components outside of battery 106.
Referring to
Each electrode plate 126A includes a current collector 200 or grid, a tab 120A extending therefrom, and electrode material 144A. Referring to
Cathode 119 is constructed in a similar manner as anode 115. Cathode 119, which is an electrode in which electric current flows out, includes a set of electrode plates 126B (i.e. cathode electrode plates), a set of tabs 124B, and a conductive coupler 128B connecting set of tabs 124B. Conductive coupler 128B or cathode collector is connected to conductive member 129 and jumper pin 125B (also referred to as the jumper connector or connector). Conductive member 129, shaped as a plate, comprises titanium, aluminum/titanium clad metal or other suitable materials. Jumper pin 125B is also connected to feed-through assembly 118, which allows cathode 119 to deliver positive charge to electronic components outside of battery 106. Separator 117 is coupled to each cathode electrode plate 126B.
Each cathode electrode plate 126B includes a current collector 200 or grid, electrode material 144B and a tab 120B extending therefrom. Tab 120B comprises electrically conductive material such as vanadium or vanadium alloy. Vanadium can be alloyed or cladded with other refractory type materials such as chromium, titanium, molybdenum, niobium or columbium, tantalum, tungsten, halfnium and zirconium. Electrode material 144B or cathode material includes metal oxides (e.g. vanadium oxide, silver vanadium oxide (SVO), manganese dioxide (MnO2) etc.), carbon monofluoride and hybrids thereof (e.g., CFx+MnO2), combination silver vanadium oxide (CSVO), lithium ion, other rechargeable chemistries, or other suitable compounds.
Liner 324 is adjacent or proximate to the case 320 to separate internal components of the battery 300 from the case 320. Liner 324 can be made of ethylene tetrafluoroethylene (ETFE) and can have a thickness of between about 25 μm and 250 μm.
A cover or cap 322 is provided at a top surface of battery 300 and can be coupled (e.g., welded, adhered, etc.) to case 320. Headspace insulator 326 is provided within case 320 to provide a space in which connections may be made to electrodes provided within case 320. Coil liner 327, as shown in
Battery 300 includes a cell element 302 (
Separator 340 is provided intermediate or between positive electrode 332 and negative electrode 360. Separator 340 is a polymeric material such as a polypropylene/polyethelene copolymer or another polyolefin multilayer laminate that includes micropores formed therein to allow electrolyte and lithium ions to flow from one side of the separator to the other. The thickness of separator 340 is between about 10 μm and about 50 μm with an average pore size of that is between about 0.02 μm and 0.1 μm.
Electrolyte 350 is provided in the case 320 (e.g., through an opening or aperture 328 in the form of a fill port provided in cover 332 of battery 300) to provide a medium through which lithium ions can move. Exemplary electrolyte includes a liquid (e.g., a lithium salt dissolved in one or more non-aqueous solvents), a lithium salt dissolved in a polymeric material such as poly(ethylene oxide) or silicone, an ionic liquid such as N-methyl-N-alkylpyrrolidinium bis(trifluoromethanesulfonyl)imide salts, a solid state electrolyte such as a lithium-ion conducting glass such as lithium phosphorous oxynitride (LiPON) or other suitable materials.
Positive electrode 322 is formed from a metal such as aluminum or an aluminum alloy having a layer of active material (e.g., lithium cobalt oxide (LiCoO2) provided thereon. Any of a variety of active materials may be utilized for the metal and active material according to various exemplary embodiments as may be now known or later developed. The thickness of the positive electrode 332 is between about 5 μm and 250 μm. In another embodiment, the thickness of the positive electrode 322 is about 75 μm. Positive electrode's 332 current collector may be a thin foil material, or may be a grid such as a mesh grid, an expanded metal grid, a photochemically etched grid, or the like.
Negative electrode 336 is formed from a metal such as copper, a copper alloy or aluminum having a layer of active material (e.g., a carbon material such as graphite) provided thereon. Any of a variety of active materials may be utilized for the metal and active material according to various exemplary embodiments as may be now known or later developed. The thickness of the negative electrode 336 is between about 5 μm and 250 μm. The negative electrode 336 may be a thin foil material, or may be a grid such as a mesh grid, an expanded metal grid, a photochemically etched grid, or the like.
As depicted in
One embodiment of the invention relates to a member 329 or element that couples a current collector 338 to case 320 or to cover 332. In one embodiment, member 329 comprises vanadium, vanadium alloy, vanadium cladded with another electrically conductive material titanium/vanadium, vanadium/aluminum etc.) In yet another embodiment, member 329 comprises other suitable cladded material such as titanium/aluminum.
In one embodiment, member 329 couples current collector 334 to pin or terminal 325. Vanadium member or element 329, for example, couples a current collector 338 or tab of a negative electrode 336 to cover 322. In one embodiment, member or element 329 is in the form of a bracket or a splice. A bracket is an overhanging member that projects from a structure. Splice is an interconnect or graft that joins or unites two members by welding the over lapping ends together. Referring to
Referring to
Numerous types of batteries may include a vanadium connector such as member 329. For example, vanadium member 329 can be used in a rechargeable battery such as a lithium-ion battery placed in a titanium or titanium alloy (e.g. Ti-6Al-4V, Ti-3Al-2.5V etc.) case 320. The rechargeable battery includes positive and negative electrodes 332, 336 along with a mixture of ethylene carbonate to ethylmethyl carbonate with 1M LiPF6 electrolyte. In this embodiment, the negative electrode 336 includes active material such as lithium titanate (Li4Ti5O12). Current collector 338 comprises aluminum or aluminum alloy with an aluminum or aluminum alloy tab 334. The positive electrode 332 includes lithium cobalt oxide (LiCoO2). The aluminum tab from the negative electrode tab 338 is connected to the titanium case 320 by a vanadium member 329. In this embodiment, member 329 is welded or connected in some manner to both the aluminum tab 338 and the titanium case 320.
Another exemplary battery involves a case negative primary cell. A primary cell can be incorporated into a neurostimulation device, cardiac device, or other like device. In this embodiment, a lithium primary cell can include a titanium case 320, a lithium metal anode 115, and a cathode 119 along with mixture of propylene carbonate to dimethoxyethane with 1M LiAsF6 electrolyte. Anode 115 includes one or more vanadium current collectors 200 with a vanadium tab 120 extending from each current collector 200. Cathode 119 consists of silver vanadium oxide disposed over a titanium current collector 200. The vanadium electrode tab 120A is connected to the titanium case by a weld or other suitable means.
Yet another exemplary battery involves a case positive primary cell. In this embodiment, a lithium primary cell can include a titanium case 320, a lithium negative electrode 336, and a positive electrode 332. Negative electrode 336 includes one or more vanadium current collectors 338 or a vanadium tab. Positive electrode 332 consists of silver vanadium oxide disposed over a current collector 334 with a vanadium tab that is connected to the titanium case by a weld or other suitable means.
Yet another exemplary battery involves a case positive rechargeable cell. For example, a lithium-ion cell includes a titanium case 320, a negative electrode 336, and a positive electrode 332 along with 1:1 mixture of ethylenecarbonate to diethylcarbonate with 1M LiPF6 electrolyte. The 1M LiPF6 electrolyte can also be used in a case negative design described above. Negative electrode 336 comprises lithium titanate (Li4Ti5O12) whereas positive electrode 332 comprises lithium cobalt oxide (LiCoO2). The positive electrode 332 includes an aluminum current collector with an aluminum tab 334. The aluminum positive electrode tab 334 is connected to the titanium case 320 by a vanadium member 339, which is welded to both the aluminum tab 334 and titanium case 320.
Still yet another battery involves a case negative rechargeable cell. A case negative rechargeable cell has a case with the same polarity as the negative electrode. A lithium-ion cell utilizes a stainless steel case 320, a negative electrode 336, and a positive electrode 332 along with 1:1 mixture of ethylenecarbonate to dimethylcarbonate with 1M LiPF6 electrolyte. Negative electrode 336 comprises a carbon lithium intercalation compound (e.g. C6Li) with a copper current collector 338 and a vanadium tab that extends therefrom. A positive electrode 332 includes a mixture of lithium cobalt oxide (LiCoO2) and lithium manganese oxide (LiMnO4). The vanadium negative electrode tab 336 is connected to the stainless steel case 322 (e.g. 300 series austenitic stainless steel class) by a vanadium member 329 which is welded to both the vanadium tab 338 and a stainless steel case 322.
Still yet another battery may involve a case positive rechargeable cell. A case positive rechargeable cell has a case that possesses the same polarity as the positive electrode. In this embodiment, the lithium-ion cell utilizes an aluminum or aluminum alloy case 320. The battery includes a negative electrode 336 that comprises carbon (C6Li) with a copper or aluminum current collector with a vanadium tab 338, a positive electrode 332 consisting of lithium cobalt oxide (LiCoO2) with an aluminum current collector with an aluminum tab. The negative electrode vanadium tab is connected to the titanium alloy feedthrough pin.
Skilled artisans appreciate that alternative embodiments can be implemented using the principles described herein. For example, member 329 can be in the form of a wire. Various other electrolytes may be used according to other exemplary embodiments. For example, according to an exemplary embodiment, the electrolyte may be a 1:1 mixture of ethylene carbonate to diethylene carbonate (EC:DEC) in a 1.0 Molar (M) salt of LiPF6. The electrolyte may include a polypropylene carbonate solvent and a lithium bis-oxalatoborate salt (sometimes referred to as LiBOB). For example, the claimed invention can be implemented utilizing various electrolytes in secondary or rechargeable cells. Other exemplary electrolyte may comprise one or more of a PVDF copolymer, a PVDF-polyimide material, and organosilicon polymer, a thermal polymerization gel, a radiation cured acrylate, a particulate with polymer gel, an inorganic gel polymer electrolyte, an inorganic gel-polymer electrolyte, a PVDF gel, polyethylene oxide (PEO), a glass ceramic electrolyte, phosphate glasses, lithium conducting glasses, lithium conducting ceramics, and an inorganic ionic liquid or gel, among others.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. For example, while several embodiments include specific dimensions, skilled artisans appreciate that these values will change depending, for example, on the shape of a particular element.