Electrochemical cell and implantable medical device including same

Abstract

Various embodiments of an electrochemical cell and an implantable medical device that includes such cell are disclosed. The cell includes a cathode including a first active material and a second active material, where the first active material includes carbon monofluoride (CFx) and the second active material includes at least one of a metal oxide or a metal fluoride, where at least one of the first or second active materials is premixed with a conductive carbon material. The electrochemical cell further includes an anode, a separator disposed between the cathode and the anode that is configured to prevent direct contact between the cathode and the anode, and an electrolyte configured to facilitate transport of ions between the cathode and the anode.

Description

ELECTROCHEMICAL CELL AND IMPLANTABLE MEDICAL DEVICE INCLUDING SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 526,041, filed July 11, 2023, the disclosure of which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] This disclosure generally relates to an electrochemical cell and an implantable medical device that includes such electrochemical cell.BACKGROUND

[0003] Electrochemical cells such as batteries are generally used to provide power to devices when wired connections to external power sources can be undesirable or inconvenient. For example, batteries can be used in portable devices such as laptops and mobile phones or in implantable medical devices (IMDs) where constant connection to external power sources can be cumbersome or excessively restrictive. Such IMDs can include a variety of devices that deliver therapy (such as electrical stimulation or drug delivery) to a patient, monitor a physiological parameter of a patient, or both. IMDs typically include several functional components encased in a housing. The housing is implanted in a body of the patient. For example, the housing can be implanted in a pocket created in a torso of the patient. The housing can include various internal components such as batteries and capacitors to deliver energy for therapy that is directed to the patient and monitor physiological parameters of the patient.SUMMARY

[0004] In general, the present disclosure provides one or more embodiments of an electrochemical cell. Such cell can be utilized with any suitable device or system. In one or more embodiments, the cell can be utilized with an implantable medical device as is further described herein. The cell can include a cathode that is manufactured utilizing a first active material (e.g., carbon monofluoride (CFX)) and a second active material (e.g., at least one of a metal oxide or a metal fluoride). At least one of the first or second active materials is premixed with a conductive carbon material (e.g., at least one of carbon black,carbon nanotubes, graphene, or graphite). At least one of the first or second active materials can be premixed with the conductive carbon material prior to the first and second active materials being combined to form the cathode.

[0005] This disclosure includes without limitation the following clauses:

[0006] Clause 1 : An electrochemical cell including a cathode that includes a first active material and a second active material, where the first active material includes carbon monofluoride (CFX) and the second active material includes at least one of a metal oxide or a metal fluoride, where at least one of the first or second active materials is premixed with a conductive carbon material. The electrochemical cell further includes an anode, a separator disposed between the cathode and the anode that is configured to prevent direct contact between the cathode and the anode, and an electrolyte configured to facilitate transport of ions between the cathode and the anode.

[0007] Clause 2: The electrochemical cell of Clause 1, where the second active material of the cathode includes at least one of silver vanadium oxide (SVO), vanadium pentoxide (V2O5), copper vanadium oxide, or manganese dioxide (MnCh).

[0008] Clause 3: The electrochemical cell of any one of Clauses 1-2, where the cathode includes at least 80% by weight of a combination of the first active material and second active material, and at least 2% by weight conductive carbon material.

[0009] Clause 4: The electrochemical cell of any one of Clauses 1-3, where the conductive carbon material includes at least one of carbon black, carbon nanotubes, graphene, or graphite.

[0010] Clause 5: The electrochemical cell of any one of Clauses 1-4, where the second active material of the cathode is premixed with the conductive carbon material, where a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5.

[0011] Clause 6: The electrochemical cell of any one of Clauses 1-4, where the first active material of the cathode is premixed with the conductive carbon material, where a ratio by weight of conductive carbon material to first active material of the cathode is at least 0.005.

[0012] Clause 7: The electrochemical cell of any one of Clauses 1-4, where each of the first active material and second active material of the cathode is premixed with the conductive carbon material.

[0013] Clause 8: The electrochemical cell of any one of Clauses 1-7, where the anode includes a lithium metal anode.

[0014] Clause 9: The electrochemical cell of any one of Clauses 1-8, where at least a portion of the conductive carbon material is disposed in combination with a binder material.

[0015] Clause 10: An implantable medical device that includes a housing, an electrical component disposed in the housing, and an electrochemical cell disposed within the housing and electrically coupled to the electrical component. The electrochemical cell includes a cathode that includes a first active material and a second active material, where the first active material includes carbon monofluoride (CFX) and the second active material includes at least one of a metal oxide or a metal fluoride, where at least one of the first or second active materials is premixed with a conductive carbon material. The electrochemical cell further includes an anode, a separator disposed between the cathode and the anode that is configured to prevent direct contact between the cathode and the anode, and an electrolyte configured to facilitate transport of ions between the cathode and the anode.

[0016] Clause 11 : The device of Clause 10, where the device is an implantable cardioverter defibrillator.

[0017] Clause 12: The device of any one of Clauses 10-11, where the second active material of the cathode includes at least one of silver vanadium oxide (SVO), vanadium pentoxide (V2O5), copper vanadium oxide, or manganese dioxide (MnCh).

[0018] Clause 13: The device of any one of Clauses 10-12, where the cathode includes at least 80% by weight of a combination of the first active material and second active material, and at least 2% by weight conductive carbon material.

[0019] Clause 14: The device of any one of Clauses 10-13, where the conductive carbon material includes at least one of carbon black, carbon nanotubes, graphene, or graphite.

[0020] Clause 15: The device of any one of Clauses 10-14, where the second active material of the cathode is premixed with the conductive carbon material, a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5.

[0021] Clause 16: The device of any one of Clauses 10-14, where the first active material of the cathode is premixed with the conductive carbon material, where a ratio by weight of conductive carbon material to first active material of the cathode is at least 0.005.

[0022] Clause 17: The device of any one of Clauses 10-14, where each of the first active material and second active material of the cathode is coated with the conductive carbon material.

[0023] Clause 18: The device of any one of claims 10-17, where the anode includes a lithium metal anode.

[0024] Clause 19: A method of forming a cathode of an electrochemical cell. The method includes disposing conductive carbon material on at least one of a first active material or second active material, where the first active material includes carbon monofluoride (CFX) and the second active material includes at least one of a metal oxide or a metal fluoride. The method further includes combining the first active material, the second active material, and at least one of a conductive material or a binder material to form a mixture, drying the mixture, and pressing the mixture to form the cathode.

[0025] Clause 20: The method of Clause 19, where disposing conductive carbon material includes disposing conductive carbon material on the second active material, where a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5.

[0026] Clause 21 : The method of Clause 20, where the conductive carbon material is disposed on the second active material prior to combining the second active material and the first active material to form the cathode.

[0027] Clause 22: The method of Clause 19, where disposing conductive carbon material includes disposing conductive carbon material on the first active material, where the first active material is premixed with the conductive carbon material, where a ratio by weight of conductive carbon material to first active material of the cathode is at least 0.005.

[0028] Clause 23: The method of Clause 22, where the conductive carbon material is disposed on the first active material prior to combining the first active material and the second active material to form the cathode.

[0029] Clause 24: The method of Clause 19, where disposing conductive carbon material includes disposing conductive carbon material on the first active material and the secondactive material such that the first active material and the second active material are premixed by the conductive carbon material.

[0030] Clause 25: The method of Clause 24, where the conductive carbon material is disposed on the first active material and the second active material prior to combining the first active material and the second active material to form the cathode.

[0031] Clause 26: The method of any one of Clauses 19-25, further including combining the conductive carbon material with a binder material prior to disposing the conductive carbon material on at least one of the first active material or second active material.

[0032] Clause 27: The method of any one of Clauses 19-26, where disposing the conductive carbon material on at least one of the first active material or the second active material includes acoustically mixing the conductive carbon material with at least one of the first active material or the second active material.

[0033] Clause 28: The method of any one of Clauses 19-27, where the second active material of the cathode includes at least one of silver vanadium oxide (SVO), vanadium pentoxide (V2O5), copper vanadium, or manganese dioxide (MnCh).

[0034] Clause 29: The method of any one of clauses 19-28, where the cathode includes at least 80% by weight of a combination of first active material and second active material, and at least 2% by weight conductive carbon material.

[0035] Clause 30: The method of any one of Clauses 19-29, where the conductive carbon material includes at least one of carbon black, carbon nanotubes, graphene, or graphite.

[0036] All headings provided herein are for the convenience of the reader and should not be used to limit the meaning of any text that follows the heading, unless so specified.

[0037] The terms “comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims. Such terms will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements.

[0038] In this application, terms such as “a,” “an,” and “the” are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration. The terms “a,” “an,” and “the” are used interchangeably with the term “at least one.” The phrases “at least one of’ and “comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

[0039] As used herein, the term “or” is generally employed in its usual sense including “and / or” unless the content clearly dictates otherwise.

[0040] The term “and / or” means one or all of the listed elements or a combination of any two or more of the listed elements.

[0041] As used herein in connection with a measured quantity, the term “about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used.Herein, “up to” a number (e.g., up to 50) includes the number (e.g., 50).Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0042] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0043] FIG. l is a schematic cross-section view of one embodiment of an electrochemical cell.

[0044] FIG. 2 is a flowchart of one method of forming a cathode used in the electrochemical cell of FIG. 1.

[0045] FIG. 3 is a schematic view of one embodiment of an implantable medical device system that includes the electrochemical cell of FIG. 1 and an implantable medical device.

[0046] FIG. 4 is a conceptual view of the implantable medical device of FIG. 3 disposed within a patient.

[0047] FIG. 5 is a graph of cell resistance versus depth of discharge for a known electrochemical cell.

[0048] FIG. 6 is a graph of voltage versus time during a higher current draw for a known electrochemical cell.

[0049] FIG. 7 is an image of silver vanadium oxide coated with a conductive carbon material.

[0050] FIG. 8 is a magnified view of a portion of the image of FIG. 7.

[0051] FIG. 9 is a graph of change in voltage versus background voltage for one embodiment of an electrochemical cell.DETAILED DESCRIPTION

[0052] In general, the present disclosure provides one or more embodiments of an electrochemical cell. Such cell can be utilized with any suitable device or system. In one or more embodiments, the cell can be utilized with an implantable medical device as is further described herein. The cell can include a cathode that is manufactured utilizing a first active material (e.g., carbon monofluoride (CFX)) and a second active material (e.g., at least one of a metal oxide or a metal fluoride). At least one of the first or second active materials is premixed with a conductive carbon material (e.g., at least one of carbon black, carbon nanotubes, graphene, or graphite). At least one of the first or second active materials can be premixed with the conductive carbon material prior to the first and second active materials being combined to form the cathode.

[0053] Typical electrochemical cells such as lithium primary batteries that include hybrid cathodes composed of two or more active materials can exhibit a cell resistance increase in a region of voltage transition from one material to the other. Such resistance increase is often referred to as voltage delay phenomenon and is exemplified in FIG. 5, which is a graph of cell resistance versus depth of discharge for a known electrochemical cell. This resistance increase can limit power capability of the cell and reduce its usable capacity. For lithium batteries used with implantable medical devices (IMDs), this limit in battery power can increase charge times, which can reduce device longevity. As shown in FIG. 6, which is a graph of voltage versus time for a known electrochemical cell, a larger positive value for AV indicates a greater voltage delay, where AV is equal to Viast minus Vinitiai (Vi). By reducing AV, cell resistance increase can be reduced. As a result, a reduction in cell resistance increase can improve usable capacity of the electrochemical cell and thereby increase longevity of the cell and associated device.

[0054] One or more embodiments of electrochemical cells described herein can provide various advantages over known electrochemical cells. For example, at least partially coating one or more active materials of the cell’s cathode with conductive carbon material prior to combining the active materials to form the cathode can reduce cell resistancewithout significantly reducing volumetric capacity of the cathode. In one or more embodiments, coating one or more of the active materials of the cell’s cathode can reduce voltage delay of the cathode. Further, one or more embodiments of cathodes described herein can have a AV reduction of greater than 50%.

[0055] FIG. l is a schematic cross-section view of one embodiment of an electrochemical cell 10. The cell 10 includes a cathode 12, an anode 14, a separator 16 disposed between the cathode and the anode that is configured to prevent direct contact between the cathode and the anode, and an electrolyte 18 configured to facilitate transport of ions between the cathode and the anode. In one or more embodiments, the cathode 12 includes a first active material and a second active material, where the first active material includes carbon monofluoride (CFX) and the second active material includes at least one of a metal oxide or a metal fluoride. At least one of the first or second active materials is premixed with a conductive carbon material as is further described herein.

[0056] The cell 10 can be any suitable primary or rechargeable electrochemical cell. In one or more embodiments, the cell 10 can be a rechargeable lithium electrochemical cell such as a lithium-ion electrochemical cell, a lithium metal electrochemical cell, a lithium polymer electrochemical cell, or other lithium electrochemical cell. Further, one or more of the cells 10 can form any suitable battery, e.g., a lithium-ion battery, a lithium metal battery, a lithium polymer battery, or other lithium batteries. Additionally, the electrochemical cell 10 can be a primary cell (e.g., non-rechargeable) or a secondary cell (e.g., rechargeable).

[0057] The electrochemical cell 10 can include any suitable elements or components. In the embodiment illustrated in FIG. 1, the cell 10 includes the cathode 12, the anode 14, the separator 16, and the electrolyte 18. The cell 10 can also include a cell housing 20 that defines an exterior of the cell. Each of the cathode 12, the anode 14, the separator 16, and the electrolyte 18 can be disposed in the cell housing 20. The cathode 12 and the anode 14 can be provided as relatively flat or planar plates, wrapped or wound in a spiral or other configuration (e.g., an oval configuration), or in a folded configuration. The separator 16 (e.g., a polymeric microporous separator) can be arranged between the cathode 12 and the anode 14 to prevent direct contact between the cathode and anode.

[0058] The cathode 12 can take any suitable shape and have any suitable dimensions. Further, the cathode 12 can include any suitable materials. For example, the cathode 12can include any suitable active materials, e.g., any one or more materials such as silver vanadium oxide (SVO) (e.g., Ag2V40n), carbon monofluoride (CFX), copper vanadium oxide, manganese dioxide (MnCh), silver vanadium oxyfluoride (Ag2V20eF2), lithium- metal oxides (e.g., LiCoCh, LiM Ch, Li(NixMnyCoz)O2, etc.), other vanadium oxides, etc. The particular materials used or included in the cathode 12 can depend on whether the electrochemical cell 10 is a primary or a secondary cell. For instance, as part of a primary cell, the active materials of the cathode 12 can include, for example, SVO, carbon monofluoride (CFX), copper vanadium oxide, manganese dioxide (Mn02), silver vanadium oxyfluoride (Ag2V20eF2), or other metal oxides or halides. As part of a secondary cell, the active materials of the cathode 12 can include, e.g., lithium-metal oxides (e.g., LiCoO2, LiMn2O4, Li(NixMnyCoz)O2, etc.), vanadium oxides, etc. In one or more embodiments, the cathode 12 can include a mixture of active materials, such as a mixture including CFXwith either Ag2V40n or MnCh.

[0059] In one or more embodiments, the cathode 12 can include the first active material and the second active material, where the first active material includes carbon monofluoride (CFX) and the second active material includes at least one of a metal oxide or a metal fluoride. Suitable metal oxides of the second active material include at least one of SVO, vanadium pentoxide (V2O5), copper vanadium oxide, or Mn02. Suitable metal fluorides of the second active material include at least one of copper fluoride ( 1F2), bismuth fluoride (BiFs), or iron fluoride (FeF2 or FeFs). The cathode 12 can have any suitable electrochemical capacity ratio of first active material to second active material, e.g., a ratio in a range of 10: 1 to 1 : 1. Further, a ratio of first active material to second active material can have any suitable electrochemical capacity ratio, e.g., a ratio in a range of 2: 1 to 6: 1 (electrochemical equivalents).

[0060] One or more of the active materials of the cathode 12 can be premixed with a conductive carbon material. As used herein, the term “premixed” means that a conductive carbon material is disposed on (e.g., at least partially coated onto) an active material prior to the active material being combined with other materials including other active materials to form the cathode 12. For example, in one or more embodiments, the first active material is premixed with the conductive carbon material. In one or more embodiments, the second active material is premixed with the conductive carbon material. Further, in one or more embodiments, each of the first active material and second active material is premixed withthe conductive carbon material. Each of the coated active materials of the cathode 12 can include any suitable ratio of conductive carbon material to active material. In one or more embodiments, the first active material of the cathode 12 is premixed with the conductive carbon material, where a ratio by weight of conductive carbon material to first active material of the coated first active material of the cathode is at least 0.005. In one or more embodiments, the second active material is premixed with the conductive carbon material, where a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5 as measured using BET (Brunauer, Emmett and Teller) methods. In one or more embodiments, at least one of the first active material or second active material is completely coated with conductive carbon material, i.e., a ratio of conductive carbon material surface area to the active material surface area of the coated active material of the cathode is 1. The cathode 12 can include any suitable percent of active materials and conductive carbon materials. In one or more embodiments, the cathode 12 includes at least 80% by weight of a combination of the first active material and the second active material, and at least 2% by weight conductive carbon material, where the 80% by weight of the combination of first active material and the second active material includes at least 10% by weight metal oxide or metal fluoride. Any suitable technique can be utilized to measure the weight percent of the active materials and the conductive carbon materials, e.g., Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD), or combustion methods.

[0061] Any suitable conductive carbon material can be premixed with at least one of the active materials. In one or more embodiments, the conductive carbon material can include at least one of carbon black, carbon nanotubes, graphene, or graphite. In one or more embodiments, at least a portion of the conductive carbon material is disposed in a binder material prior to premixing the conductive carbon material with one or more active materials.

[0062] Further, any suitable technique can be utilized to premix at least one of the active materials of the cathode 12 with conductive carbon material to form coated active materials mixture. In one or more embodiments, the conductive carbon material can be premixed with an active material using an acoustic mixer, milling such as ball milling, or wet mixing. In one or more embodiments, the conductive carbon material can be premixedwith an active material using physical vapor deposition, chemical vapor deposition, or by carbonization of organics under an inert atmosphere.

[0063] FIG. 7 is a micrograph of SVO active material that is premixed with conductive carbon material (carbon black) prior to combining the coated SVO active material with other materials (including other active material) to form a cathode mixture. FIG. 8 is a micrograph of a magnified portion of the micrograph of FIG. 7. As can be seen in these figures, a small amount of carbon black, which has a surface area that is typically 30 to 60 times that of SVO, can cover at least 50% of particles of SVO active material, thus maintaining high weight percentage of the active materials of the cathode, and high electrochemical capacity of the cathode.

[0064] The cathode 12 can further include a conductivity enhancer and a binder. The conductivity enhancer is typically a conductive carbon, such as carbon black, acetylene black, carbon nanotubes, graphene, and / or graphite. Various combinations of such conductivity enhancers can be used if desired. The amount of conductivity enhancer is typically at least 0.5% by weight, and typically no more than 10% by weight, based on the total weight of the dry cathode mixture (without solvent). The binder for these conductivity enhancers can include carboxy methyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), or combinations thereof. The amount of binder is typically at least 0.5% by weight, and typically no more than 10% by weight, based on the total weight of the dry cathode mix (without solvent). The conductivity enhancer and binder can be combined with the active materials after one or more of such active materials have been premixed with conductive carbon material. The conductivity enhancer can include the same material as the conductive carbon material or a different material.

[0065] Such binders can be used in an electrochemical cell of relatively small volume but of relatively high power (reported as therapeutic power) and relatively high capacity (reported as capacity density), but this is not a requirement. Using these polymers, the active materials can be increased to greater than 92% by weight, making the cathode / cell more energy dense. The cathode mixture can be slurry coated or dry processed, allowing for much thinner layers, which can be more cost effective, and provides higher yields.

[0066] The anode 14 can include any suitable materials. In one or more embodiments, the anode 14 can include a lithium alloy. The anode 14 can be substantially free of anymaterials or impurities in addition to the lithium alloy. The lithium alloy can include at least 70% by weight lithium and no greater than 99.9% by weight lithium or any suitable range therebetween. The lithium alloy of the anode 14 can include at least 70% by weight lithium, at least 75% by weight lithium, at least 80% by weight lithium, at least 85% by weight lithium, at least 90% by weight lithium, or at least 95% by weight lithium. The lithium alloy of the anode 14 can include no greater than 99.9% by weight lithium, no greater than 99% by weight lithium, no greater than 95% by weight lithium, no greater than 90% by weight lithium, no greater than 85% by weight lithium, no greater than 80% by weight lithium, or no greater than 75% by weight lithium. In one or more embodiments, the lithium alloy of the anode 14 can include at least 70% by weight lithium and no greater than 99% by weight lithium. In one or more embodiments, the lithium alloy of the anode 14 can include at least 85% by weight lithium and no greater than 95% by weight lithium. In one or more embodiments, the lithium alloy of the anode 14 can include at least 88% by weight lithium and no greater than 92% by weight lithium.

[0067] In general, one or more embodiments of electrochemical cells described herein can exhibit high energy density by having thick cathodes combined with an appropriately sized anode. Achieving high energy and power density in electrochemical cells can provide improved longevity while enabling high-power features such as telemetry and optical sensor modalities. In one or more embodiments, high-energy density can be improved by utilizing thick, CFx rich cathodes (i.e., high CFx: SVO ratio), paired with an appropriately sized anode (lithium metal, lithium alloy anode, etc.). Currently available electrochemical cells may have cathodes that are limited in capacity as the cells include enough lithium for the anode to support near full use of the capacity of the cathode. Since power density of the electrochemical cell is typically lower at high depths of discharge (i.e., greater than about 70% depth of discharge), additional optimization for energy density and power density in one or more embodiments of electrochemical cells can be accomplished by providing quantities of lithium in the anode of the cell to support discharge to just about 70% depth of discharge or similar values based on the power characteristics of the particular cathode formulation instead of near full discharge capacity of the cathode. One or more embodiments of this anode limited design can minimize excess anode material (e.g., lithium) as compared to anodes having excess anode material(e.g., lithium) designed to support a low power region of a highly discharged cathode (greater than about 70% depth of discharge).

[0068] Further, one or more embodiments of electrochemical cells having a reduced anode volume (e.g., an anode having a reduced quantity of lithium) can enable cathodes having an increased volume, thereby improving energy density. As a result of this improved energy density, these cells can enable longer lived, smaller implantable medical devices that can be utilized, e.g., as monitoring devices such as sensors that can detect various physiological conditions, e.g., heart failure or stroke. Further, one or more embodiments of electrochemical cells having reduced anode volumes can enable higher power telemetry capabilities of implantable medical devices. The various embodiments of reduced volume anodes can be utilized with any suitable embodiments, including those that do not include conductive carbon material disposed on active material of the cathode or anode.

[0069] During charging and discharging of the electrochemical cell 10, lithium ions can move between the cathode 12 and the anode 14. Such movement of lithium ions between the cathode 12 and the anode 14 can be referred to as ion transfer. For example, when the electrochemical cell 10 is discharged, lithium ions flow from the anode 14 to the cathode 12. In contrast, when the electrochemical cell 10 is charged, lithium ions flow from the cathode 12 to the anode 14. While the separator 16 can prevent direct contact between the cathode 12 and the anode 14, the separator can permit the flow of ions between the anode 14 and the cathode 12. Furthermore, the electrolyte 18 can facilitate transport of ions between the anode 14 and the cathode 12.

[0070] The electrolyte 18 can be disposed in the cell housing 20. The electrolyte 18 can generally fill at least a portion of any space inside the cell housing 20 that is not filled by the other components (e.g., the cathode 12, the anode 14, the separator 16, insulators, conductors, etc.) of the electrochemical cell 10. When the cathode 12 and the anode 14 are electrically isolated from the cell housing 20, the cell housing can float at the electrical potential of the electrolyte. The electrolyte 18 can be one or more of, for example, a liquid, a gel, a paste, etc. The material composition of the electrolyte can depend on a cell type of the electrochemical cell 10. The electrolyte 18 can include, e.g., lithium salt dissolved in organic solvents, or other suitable electrolyte.

[0071] The separator 16 of the electrochemical cell 10 can be configured to electrically insulate the cathode 12 from the anode 14. Conventional materials can be used. Thematerial is generally wettable by the cell electrolyte, sufficiently porous to allow the electrolyte to flow through separator material and maintain physical and chemical integrity within the cell during operation. Examples of suitable separator materials include, but are not limited to, fluoropolymeric fabrics, polytetrafluoroethylene (PTFE), ceramics, nonwoven glass, glass fiber material, polypropylene, and polyethylene. For example, the separator 16 can include microporous polyethylene (PE) or polypropylene (PP) and / or a layer of non-woven polypropylene or polyethylene laminated to it. As described in U.S. Patent No. 8,945,753 B2 to Chen et al. and entitled IMPLANTABLE BATTERY HAVING THERMAL SHUTDOWN SEPARATOR, a separator can include three layers, for example, a polyethylene layer sandwiched between two layers of polypropylene. The polyethylene layer can have a lower melting point than the polypropylene layers and provide a shutdown mechanism in case of cell overheating.

[0072] The electrochemical cell 10 can include any suitable additional elements or components. For example, although not shown, the cell 10 can include one or more current collectors associated with one or both of the cathode 12 and the anode 14. Any suitable current collectors can be utilized. In general, such current collectors are typically metal films or foils such as aluminum, titanium, nickel, copper, or another conductive metal that is corrosion-resistant when associated with the active anode material. They can be primed or unprimed. In one or more embodiments, one or more current collectors can be perforated.

[0073] The electrochemical cell 10 can be manufactured using any suitable technique. For example, FIG. 2 is a flowchart of one embodiment of method of manufacturing the cathode 12. Although described regarding the cathode 12 of cell 10 of FIG. 1, the method 100 can be utilized to form any suitable cathode. At 102, conductive carbon material is premixed with at least one of the first active material or second active material. Any suitable technique can be utilized to premix the conductive carbon material with at least one of the first or second active materials, e.g., acoustic mixing. In one or more embodiments, the first active material includes carbon monofluoride (CFX). In one or more embodiments, the second active material includes at least one of a metal oxide or a metal fluoride.

[0074] The conductive carbon material can be premixed with at least one of the first active material or second active material. In one or more embodiments, the conductive carbonmaterial is premixed with the first active material, where a ratio by weight of conductive carbon material to first active material of the coated first active material of the cathode is at least 0.005. The conductive carbon material can be premixed with the first active material prior to combining the first active material and the second active material to form the cathode.

[0075] In one or more embodiments, the conductive carbon material is premixed with the second active material, where a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5. The conductive carbon material can be premixed with the second active material prior to combining the first active material and the second active material to form the cathode.

[0076] In one or more embodiments, the conductive carbon material can be premixed with each of the first and second active materials prior to combining the first active material and the second active material to form the cathode. In one or more embodiments, the method 100 can include combining the conductive carbon material with a binder material prior to premixing the conductive carbon material with at least one of the first or second active materials.

[0077] At 104, the first and second active materials can be combined using any suitable technique. The combination of first and second active materials, where at least one of these materials is premixed with conductive carbon material, can further be combined with at least one of a binder, and conductivity enhancer, or an optional thickener in a solvent at 106 using any suitable technique to form a cathode mixture. The materials of the cathode mixture can be combined in any suitable order. For example, in one or more embodiments, the first active material can be combined with one or more of a binder, conductivity enhancer, or thickener prior to being combined with the second active material or other active materials.

[0078] At 108, the cathode mixture can be dried to remove substantially all of the solvent using any suitable technique. After drying, the cathode mixture can be pressed at 110 using any suitable technique to form the cathode 12.

[0079] In one or more embodiments, one or more active materials and inactive materials of the cathode can be premixed with one or more conductive carbon materials using any suitable technique. In one or more embodiments, all active and inactive materials of the cathode 12 can be premixed with one or more conductive materials using any suitabletechnique. Such conductive carbon coating of the materials of the cathode can also reduce cell resistance without significantly reducing volumetric capacity of the cathode.

[0080] The electrochemical cell 10 can be utilized with any suitable device or system. For example, FIG. 3 is a schematic diagram of one embodiment of an implantable medical device system 200 that includes the electrochemical cell (e.g., battery) 10 of FIG. 1 utilized with an implantable medical device (IMD) 220. The system 200 also includes a charging apparatus 210 operatively coupled to the cell 10.

[0081] The charging apparatus 210 can be configured to provide the charging current directly to the cell 10, or the charging apparatus 210 can be configured to provide the charging current via an optional battery management system (BMS) 230. Furthermore, the charging apparatus 210 can be configured to provide the charging current via a wired or wireless connection.

[0082] The system 200 can further include the IMD 220 that is powered by the electrochemical cell 10. In other words, the IMD 220 can include one or more of the electrochemical cells 10. An embodiment of the IMD 220 as an implantable medical device is depicted in FIG. 4, which is a conceptual drawing illustrating the IMD 220 at least partially implanted within a patient 300. As depicted in FIG. 3, the IMD 220 includes a housing 221 that defines an exterior of the device. The IMD 220 can be any suitable implantable medical device such as, for example, implantable pulse generators, implantable cardioverter defibrillators, implantable cardiac contractility modulators, implantable neurostimulators, implantable mechanical assist devices, etc.

[0083] The IMD 220 can include a controller 228 disposed in the housing 221 and operatively coupled to the electrochemical cell 10. The controller 228 can include one or more processors, logic gates, or other digital circuitry to control operations of the device 220. The controller 228 can also include data storage for data storage and access to processing programs or routines that can be employed to carry out the techniques, processes, and algorithms of the device 220. In one or more embodiments, the controller 228 can be operatively couplable to the charging apparatus 210. In one or more embodiments, the controller 228 can be operatively coupled to an energy harvester 226.

[0084] The IMD 220 can include an optional kinetic energy harvester 226 disposed in the housing 221 and operatively coupled to the electrochemical cell 120 to charge the cell. The kinetic energy harvester 226 can be configured to move within the housing 221 togenerate electrical energy. In other words, the kinetic energy harvester 226 can be a transducer configured to convert kinetic energy into electrical energy and provide an electric current. The controller 228 can be operatively coupled to the kinetic energy harvester 226 and configured to receive the electrical energy provided by the kinetic energy harvester and use such electrical energy to charge the electrochemical cell 10.

[0085] The IMD 220 can also include one or more one or more electrodes 222 to facilitate delivery of therapeutic electrical pulses to desired treatment areas. The IMD 220 can include the one or more electrodes with or without leads. The IMD 220 can also include one or more electrical components 224 disposed in the housing 221. The one or more electrical components 224 can include any suitable electrical components or circuits, e.g., one or more pulse generators, switches, passive electrical components (e.g., capacitors, inductors, or resistors), digital logic circuits, processors, or other components to facilitate operation of the device 220. Additionally, the one or more electrical components 224 can be operatively coupled to the electrochemical cell 10 to receive power. In other words, the cell 10 can be configured to provide power to the one or more electrical components.EXAMPLES

[0086] Lithium batteries were constructed with cathodes that included a first active material of CFx and a second active material of SVO with a weight ratio of 0.7. An electrolyte of 1.0M LiAsFe in propylene carbonate / dimethoxy ethane was utilized. Batteries were initially discharged at 1 mA to about 30% remaining energy and then switched to 25 microamps discharge and pulsed every two weeks with a current density of 35 mA / cm2for 10 seconds. All testing was performed at a temperature of 37 °C.

[0087] FIG. 9 is a graph that illustrates the extent of voltage delay (y-axis), as defined in FIG. 9 as a function of battery background voltage (x-axis) which inversely related to the remaining battery energy. Lower voltage delay value (y-axis) is desirable. The line with open circles indicates batteries having cathodes that do not include a conductive carbon material premixed with an active material of the cathode, and the line with open squares indicates batteries having cathodes that include carbon cathode material premixed with the SVO active material.

[0088] It should be understood that various aspects disclosed herein can be combined in different combinations than the combinations specifically presented in the description andaccompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., all described acts or events cannot be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure can be performed by a combination of units or modules associated with, for example, a medical device.

[0089] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include computer-readable storage media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0090] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein can refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0091] All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure. Illustrative embodiments of this disclosure are discussed and reference has been made to possible variations within the scope of this disclosure. These and other variations and modifications in the disclosure will be apparent to those skilled in the art without departing from the scope of the disclosure, and it should be understood that this disclosure is not limited to the illustrative embodiments set forth herein. Accordingly, the disclosure is to be limited only by the claims provided below.

Claims

WHAT IS CLAIMED IS:

1. An electrochemical cell comprising: a cathode comprising a first active material and a second active material, wherein the first active material comprises carbon monofluoride (CFX) and the second active material comprises at least one of a metal oxide or a metal fluoride, wherein at least one of the first or second active materials is premixed with a conductive carbon material; an anode; a separator disposed between the cathode and the anode that is configured to prevent direct contact between the cathode and the anode; and an electrolyte configured to facilitate transport of ions between the cathode and the anode.

2. The electrochemical cell of claim 1, wherein the cathode comprises: at least 80% by weight of a combination of the first active material and the second active material; and at least 2% by weight of the conductive carbon material.

3. The electrochemical cell of any one of claims 1-2, wherein the second active material of the cathode is premixed with the conductive carbon material, wherein a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5.

4. The electrochemical cell of any one of claims 1-3, wherein the first active material of the cathode is premixed with the conductive carbon material, wherein a ratio by weight of conductive carbon material to first active material of the coated first active material of the cathode is at least 0.005.

5. The electrochemical cell of any one of claims 1-3, wherein each of the first active material and second active material of the cathode is premixed with the conductive carbon material.

6. An implantable medical device comprising: a housing; an electrical component disposed in the housing; and an electrochemical cell disposed within the housing and electrically coupled to the electrical component, the electrochemical cell comprising: a cathode comprising a first active material and a second active material, wherein the first active material comprises carbon monofluoride (CFX) and the second active material comprises at least one of a metal oxide or a metal fluoride, wherein at least one of the first or second active materials is premixed with a conductive carbon material; an anode; a separator disposed between the cathode and the anode that is configured to prevent direct contact between the cathode and the anode; and an electrolyte configured to facilitate transport of ions between the cathode and the anode.

7. The device of claim 6, wherein the cathode comprises: at least 80% by weight of a combination of the first active material and the second active material; and at least 2% by weight conductive carbon material.

8. The device of any one of claims 6-7, wherein the second active material of the cathode is premixed with the conductive carbon material, wherein a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5.

9. The device of any one of claims 6-7, wherein the first active material of the cathode is premixed the conductive carbon material, wherein a ratio by weight of conductive carbon material to first active material of the cathode is at least 0.005.

10. The device of any one of claims 6-7, wherein each of the first active material and second active material of the cathode is coated with the conductive carbon material.

11. A method of forming a cathode of an electrochemical cell, the method comprising: premixing conductive carbon material with at least one of a first active material or second active material, wherein the first active material comprises carbon monofluoride (CFX) and the second active material comprises at least one of a metal oxide or a metal fluoride; combining the first active material, the second active material, and at least one of a conductive material or a binder material to form a mixture; drying the mixture; and pressing the mixture to form the cathode.

12. The method of claim 11, wherein disposing conductive carbon material comprises disposing conductive carbon material on the second active material, wherein a ratio of conductive carbon material surface area to second active material surface area of the coated second active material of the cathode is at least 0.5.

13. The method of claim 11, wherein disposing conductive carbon material comprises disposing conductive carbon material on the first active material, wherein the first active material is premixed with the conductive carbon material, wherein a ratio by weight of conductive carbon material to first active material of the cathode is at least 0.005.

14. The method of any one of claims 11-13, further comprising combining the conductive carbon material with a binder material prior to disposing the conductive carbon material on at least one of the first active material or the second active material.

15. The method of any one of claims 11-14, wherein disposing the conductive carbon material on at least one of the first active material or the second active material comprises acoustically mixing the conductive carbon material with at least one of the first active material or the second active material.

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