Patent Description:
Medical devices such as implantable medical devices (IMDs) include a variety of devices that deliver therapy (such as electrical simulation or drugs) to a patient, monitor a physiological parameter of a patient, or both. IMDs typically include a number of functional components encased in a housing. The housing is implanted in a body of the patient. For example, the housing may be implanted in a pocket created in a torso of a patient. The housing may include various internal components such as batteries and capacitors to deliver energy for therapy delivered to a patient and/or to power circuitry for monitoring a physiological parameter of a patient and controlling the functionality of the medical device. <CIT> describes an electrochemical cell with electrode elements that include alignment aperatures. <CIT> describes an accumulator and method for the manufacture thereof.

The present invention provides a battery assembly for an implantable medical device according to claim <NUM>.

In some aspects, the disclosure is directed to battery assemblies for use, e.g., in a medical device, and techniques for manufacturing the battery assemblies.

In one example, the disclosure is directed to a battery assembly for an implantable medical device. The assembly may comprise an electrode stack comprising a plurality of electrode plates, wherein the plurality of electrode plates comprises a first electrode plate including a first tab extending from the first electrode plate and a second electrode plate including a second tab extending from the second electrode plate; a spacer between the first tab and the second tab; and a rivet extending through the first tab, second tab, and spacer, wherein the rivet is configured to mechanically attach the first tab, second tab, and spacer to each other. In another example, the disclosure is directed to an implantable medical device comprising such a battery assembly within an outer housing of the implantable medical device, and processing circuitry, wherein the processing circuitry is configured to control delivery electrical therapy from the implantable medical device to a patient using power supplied by the battery assembly.

In another example, the disclosure is directed to a battery assembly for an implantable medical device. The assembly may comprise a battery housing; an electrode stack comprising a plurality of electrode plates, wherein the plurality of electrode plates including a first tab stack of anode tabs extending from anode plates of the electrode stack and a second tab stack of cathode tabs extending from cathodes plates of the electrode stack, wherein the first tab stack is adjacent to the second tab stack and a gap separates the first tab stack from the second tab stack; and a shim located on a top tab of at least one of the first tab stack or the second tab stack, wherein the shim is located between the at least one of the first tab stack or the first tab of the second tab stack and the battery housing. In another example, the disclosure is directed to an implantable medical device comprising such a battery assembly within an outer housing of the implantable medical device, and processing circuitry, wherein the processing circuitry is configured to control delivery electrical therapy from the implantable medical device to a patient using power supplied by the battery assembly.

A variety of medical devices may utilize one or more batteries as a power source for operational power. For example, an implantable medical device (IMD) that provides cardiac rhythm management therapy to a patient may include a battery to supply power for the generation of electrical therapy or other functions of the IMD. For ease of illustration, examples of the present disclosure will be described primarily with regard to batteries employed in IMDs that provide cardiac rhythm management therapy. However, as will be apparent from the description herein, examples of the disclosure are not limited to IMDs that provide such therapy. For example, in some instances, one or more of the example batteries describe herein may be used by a medical device configured to deliver electrical stimulation to a patient in the form of neurostimulation therapy (e.g., spinal cord stimulation therapy, deep brain stimulation therapy, peripheral nerve stimulation therapy, peripheral nerve field stimulation therapy, pelvic floor stimulation therapy, and the like). In some examples, example batteries of this disclosure may be employed in medical device configured to monitor one or more patient physiological parameters, e.g., by monitoring electrical signals of the patient, alone or in conjunction with the delivery of therapy to the patient.

In some examples, a battery of an IMD may include a plurality of electrode plates (e.g., including both anode and cathode plates) stacked on each other in which each of the plates includes a tab extending therefrom. The tabs of the anode plates may be aligned with each other in a stack and electrically connected to each other to form an anode of the battery. In this sense, the tab stack may function as an electrical interconnect between the plates of the anode. Similarly, the tabs of the cathode plates may be aligned with each other in a stack and electrically connected to each other to form a cathode of the battery. In some examples, such a battery may be referred to as a flat plate battery.

In some examples, in each the anode tab stack and cathode tab stack, a spacer may be located between adjacent individual tabs in the stack of tabs, e.g., such that each individual tab is separated from an adjacent tab by a spacer. The spacers may be electrically conductive to electrically couple the respective tabs in the stack to each other and define an electrical interconnect, at least in part, between respective plates of the electrode. For each electrode, the tabs in the stack of tabs and spacers may be attached to each other by one or more side laser welds that span the height of the tab stack.

In some examples, the tabs of an electrode stack may be flexed or bent due to the nature of the spacer and tab interconnect design. This results in stressed materials that can lead to failures of the side weld(s) and/or insulation failures.

In some examples, a stacked plate battery interconnect spacer stack may be subject to "fanning" (e.g., opening like the pages of a bound book) as a result of the mechanical force applied by the expansion of the electrode stack, e.g., during discharge of the battery. The applied force may displace the spacer stack causing electrical shorting to the surrounding battery enclosure, and/or leading to failure of the laser welds on the interconnect spacer stack.

In some examples, the laser welds on the side of an interconnect spacer stack are subject to mechanical loading, e.g., when the electrode stack expands during battery life. The electrode stack expansion may be due to plate warp or cathode expansion during battery discharge. As described above, the mechanical loading on the interconnect spacer stack may result in the interconnect spacer stack "fanning" open much like when a book and its many pages are opened.

In accordance with at least some examples of the disclosure, a battery assembly that includes an electrode tab stack may include spacers of varying thicknesses and/or may include multiple spacers between individual tabs. The spacer and tab stacking sequence may be tailored to provide for desired flexing/bending that reduces material stresses in the interconnect and nearby electrode materials. In some examples, a predictive model may be employed to predict a desirable stacking sequence, e.g., using spacers of desired thicknesses. In some examples, the model may consider sources of variation in the components used to create the battery assembly. For example, the modeling may be used to assess the variation in thickness of the spacers and the associated tabs. The model may be used to strategically place the spacers based on inferred variation or measured variation in each component of the stacked assembly.

Additionally, or alternatively, a battery assembly in accordance with some examples of the disclosure may include a rivet through an aperture in the tab/spacer stack, (e.g., through a hole in or near the center of the stack of tabs). The rivet may prevent the mechanical "fanning" of the spacers. The rivet can be a piece of wire that is mechanically fastened and/or laser welded to the outer most plate tabs (e.g., the top and bottom tabs of the tab stack) of the stack assembly. The rivet may be configured to counter-act the forces applied by the electrode stack expansion.

Additionally, or alternatively, a battery assembly in accordance with some examples of the disclosure may include one or more spacers (also referred to as a shim) between the interconnect spacer tab stack and the surrounding battery housing (e.g., between the top of the spacer tab stack and the surrounding battery housing). In some examples, the shim may be formed of a polymer material that acts as an electrical insulator to prevent electrical shorting. The shim consumes space between the interconnect spacer stack and the enclosure wall, thus limiting the "fanning" that imparts stress on the laser welds. The shim may transfer the forces of electrode expansion away from the interconnect laser weld joint and impart those forces to the more robust battery housing walls.

In some examples, the shim may be a relatively simple molded polymer component that is added during assembly, or it can be designed as an integral feature of another insulator (e.g. headspace insulator, stack insulator, and/or feedthrough insulator). In some examples, the "shim" may be attached as a foldable feature that allows assembly ease, while also preventing occurrences of the shim inadvertently not being installed during battery assembly.

<FIG> is a conceptual diagram that illustrates an example medical device system <NUM> that may be used to provide electrical therapy to a patient <NUM>. Patient <NUM> ordinarily, but not necessarily, will be a human. System <NUM> may include an IMD <NUM>, and an external device <NUM>. In the example illustrated in <FIG>, IMD <NUM> has battery <NUM> positioned within an outer housing <NUM> of the IMD <NUM>. Battery <NUM> may be a primary or secondary battery.

While the examples in the disclosure are primarily described with regard to battery <NUM> positioned within housing <NUM> of IMD <NUM> for delivery of electrical therapy to heart of patient <NUM>, in other examples, battery <NUM> may be utilized with other implantable medical devices. For example, battery <NUM> may be utilized with an implantable drug delivery device, an implantable monitoring device that monitors one or more physiological parameter of patient <NUM>, an implantable neurostimulator (e.g., a spinal cord stimulator, a deep brain stimulator, a pelvic floor stimulator, a peripheral nerve stimulator, or the like), or the like. Moreover, while examples of the disclosure are primarily described with regard to implantable medical devices, examples are not limited as such. Rather, some examples of the batteries described herein may be employed in any medical device including non-implantable medical devices. For example, an example battery may be employed to supply power to a medical device configured delivery therapy to a patient externally or via a transcutaneoulsy implanted lead or drug delivery catheter.

In the example depicted in <FIG>, IMD <NUM> is connected (or "coupled") to leads <NUM>, <NUM>, and <NUM>. IMD <NUM> may be, for example, a device that provides cardiac rhythm management therapy to heart <NUM>, and may include, for example, an implantable pacemaker, cardioverter, and/or defibrillator that provides therapy to heart <NUM> of patient <NUM> via electrodes coupled to one or more of leads <NUM>, <NUM>, and <NUM>. In some examples, IMD <NUM> may deliver pacing pulses, but not cardioversion or defibrillation shocks, while in other examples, IMD <NUM> may deliver cardioversion or defibrillation shocks, but not pacing pulses. In addition, in further examples, IMD <NUM> may deliver pacing pulses, cardioversion shocks, and defibrillation shocks.

IMD <NUM> may include electronics and other internal components necessary or desirable for executing the functions associated with the device. In one example, IMD <NUM> includes one or more of processing circuitry, memory, a signal generation circuitry, sensing circuitry, telemetry circuitry, and a power source. In general, memory of IMD <NUM> may include computer-readable instructions that, when executed by a processor of the IMD, cause it to perform various functions attributed to the device herein. For example, processing circuitry of IMD <NUM> may control the signal generator and sensing circuitry according to instructions and/or data stored on memory to deliver therapy to patient <NUM> and perform other functions related to treating condition(s) of the patient with IMD <NUM>.

IMD <NUM> may include or may be one or more processors or processing circuitry, 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" and "processing circuitry" as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.

Memory may include any volatile or non-volatile media, such as a random-access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. Memory may be a storage device or other non-transitory medium.

The signal generation circuitry of IMD <NUM> may generate electrical therapy signals that are delivered to patient <NUM> via electrode(s) on one or more of leads <NUM>, <NUM>, and <NUM>, in order to provide pacing signals or cardioversion/defibrillation shocks, as examples. The sensing circuitry of IMD <NUM> may monitor electrical signals from electrode(s) on leads <NUM>, <NUM>, and <NUM> of IMD <NUM> in order to monitor electrical activity of heart <NUM>. In one example, the sensing circuitry may include switching circuitry to select which of the available electrodes on leads <NUM>, <NUM>, and <NUM> of IMD <NUM> are used to sense the heart activity. Additionally, the sensing circuitry of IMD <NUM> may include multiple detection channels, each of which includes an amplifier, as well as an analog-to-digital converter for digitizing the signal received from a sensing channel (e.g., electrogram signal processing by processing circuitry of the IMD).

Telemetry circuitry of IMD <NUM> may be used to communicate with another device, such as external device <NUM>. Under the control of the processing circuitry of IMD <NUM>, the telemetry circuitry may receive downlink telemetry from and send uplink telemetry to external device <NUM> with the aid of an antenna, which may be internal and/or external.

The various components of IMD <NUM> may be coupled to a power source such as battery <NUM>. Battery <NUM> may be a lithium primary battery or lithium secondary (rechargeable) battery although other types of battery chemistries are contemplated. Battery <NUM> may be capable of holding a charge for several years. In general, battery <NUM> may supply power to one or more electrical components of IMD <NUM>, such as, e.g., the signal generation circuitry, to allow IMD <NUM> to deliver therapy to patient <NUM>, e.g., in the form of monitoring one or more patient parameters, delivery of electrical stimulation, or delivery on a therapeutic drug fluid. Battery <NUM> may include a lithium-containing anode and cathode including an active material that electrochemically reacts with the lithium within an electrolyte to generate power. A wide variety of battery types and.

Leads <NUM>, <NUM>, <NUM> that are coupled to IMD <NUM> may extend into the heart <NUM> of patient <NUM> to sense electrical activity of heart <NUM> and/or deliver electrical therapy to heart <NUM>. In the example shown in <FIG>, right ventricular (RV) lead <NUM> extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium <NUM>, and into right ventricle <NUM>. Left ventricular (LV) coronary sinus lead <NUM> extends through one or more veins, the vena cava, right atrium <NUM>, and into the coronary sinus <NUM> to a region adjacent to the free wall of left ventricle <NUM> of heart <NUM>. Right atrial (RA) lead <NUM> extends through one or more veins and the vena cava, and into the right atrium <NUM> of heart <NUM>. In other examples, IMD <NUM> may deliver therapy to heart <NUM> from an extravascular tissue site in addition to or instead of delivering therapy via electrodes of intravascular leads <NUM>, <NUM>, <NUM>. In the illustrated example, there are no electrodes located in left atrium <NUM>. However, other examples may include electrodes in left atrium <NUM>.

IMD <NUM> may sense electrical signals attendant to the depolarization and repolarization of heart <NUM> (e.g., cardiac signals) via electrodes (not shown in <FIG>) coupled to at least one of the leads <NUM>, <NUM>, and <NUM>. In some examples, IMD <NUM> provides pacing pulses to heart <NUM> based on the cardiac signals sensed within heart <NUM>. The configurations of electrodes used by IMD <NUM> for sensing and pacing may be unipolar or bipolar. IMD <NUM> may also deliver defibrillation therapy and/or cardioversion therapy via electrodes located on at least one of the leads <NUM>, <NUM>, and <NUM>. IMD <NUM> may detect arrhythmia of heart <NUM>, such as fibrillation of ventricles <NUM> and <NUM>, and deliver defibrillation therapy to heart <NUM> in the form of electrical shocks. In some examples, IMD <NUM> may be programmed to deliver a progression of therapies (e.g., shocks with increasing energy levels), until a fibrillation of heart <NUM> is stopped. IMD <NUM> may detect fibrillation by employing one or more fibrillation detection techniques known in the art. For example, IMD <NUM> may identify cardiac parameters of the cardiac signal (e.g., R-waves, and detect fibrillation based on the identified cardiac parameters).

In some examples, external device <NUM> may be a handheld computing device or a computer workstation. External device <NUM> may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may be, for example, a cathode ray tube (CRT) display, a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with particular functions. External <NUM> can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user may interact with the user interface. In some embodiments, a display of external <NUM> may include a touch screen display, and a user may interact with programmer <NUM> via the display.

A user, such as a physician, technician, other clinician or caregiver, or the patient, may interact with external device <NUM> to communicate with IMD <NUM>. For example, the user may interact with external device <NUM> to retrieve physiological or diagnostic information from IMD <NUM>. A user may also interact with external device <NUM> to program IMD <NUM> (e.g., select values for operational parameters of IMD <NUM>).

External device <NUM> may communicate with IMD <NUM> via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, external device <NUM> may include a communication head that may be placed proximate to the patient's body near the IMD <NUM> implant site in order to improve the quality or security of communication between IMD <NUM> and external device <NUM>.

In the example depicted in <FIG>, IMD <NUM> is connected (or "coupled") to leads <NUM>, <NUM>, and <NUM>. In the example, leads <NUM>, <NUM>, and <NUM> are connected to IMD <NUM> using the connector block <NUM>. For example, leads <NUM>, <NUM>, and <NUM> are connected to IMD <NUM> using the lead connector ports in connector block <NUM>. Once connected, leads <NUM>, <NUM>, and <NUM> are in electrical contact with the internal circuitry of IMD <NUM>. Battery <NUM> may be positioned within the housing <NUM> of IMD <NUM>. Housing <NUM> may be hermetically sealed and biologically inert. In some examples, housing <NUM> may be formed from a conductive material. For example, housing <NUM> may be formed from a material including, but not limited to, titanium, stainless steel, among others.

<FIG> is a conceptual diagram of IMD <NUM> of <FIG> with connector block <NUM> not shown and a portion of housing <NUM> removed to illustrate some of the internal components within housing <NUM>. IMD <NUM> includes housing <NUM>, a control circuitry <NUM> (which may include processing circuitry), battery <NUM> (e.g., an organic electrolyte battery) and capacitor(s) <NUM>. Control circuitry <NUM> may be configured to control one or more sensing and/or therapy delivery processes from IMD <NUM> via leads <NUM>, <NUM>, and <NUM> (not shown in <FIG>). Battery <NUM> includes battery assembly housing <NUM> and insulator <NUM> (or liner) disposed therearound. Battery <NUM> charges capacitor(s) <NUM> and powers control circuitry <NUM>.

<FIG> and <FIG> are conceptual diagrams illustrating aspect of example battery <NUM>. Battery <NUM> includes assembly housing <NUM> having a bottom housing portion 50A and top housing portion 50B (shown in <FIG>), a feed-through terminal <NUM>, and an electrode assembly <NUM>. An electrolyte may be filled into via a fill port (not shown) in housing <NUM>. Housing <NUM> houses electrode assembly <NUM> with the electrolyte. Top portion 50B and bottom portion 50A of housing may be welded or otherwise attached to seal the enclosed components of battery <NUM> within housing <NUM>. Feed-through assembly <NUM>, formed by pin <NUM> and insulator member/ferrule <NUM>, is electrically connected to jumper pin 60B. The connection between pin <NUM> and jumper pin 60B allows delivery of positive charge from electrode assembly <NUM> to electronic components outside of battery <NUM>.

As noted above, a fill port (not shown) allows for the introduction of liquid electrolyte to electrode assembly <NUM>. The electrolyte creates an ionic path between the anode(s) and the cathode(s) of electrode assembly <NUM>. The electrolyte serves as a medium for migration of ions between the anode(s) and the cathode(s) during an electrochemical reaction with these electrodes.

Electrode assembly <NUM> is depicted as a stacked assembly. The anode(s) comprise a set of electrode plates <NUM> (including individual anode electrode plate 76A) with a set of tabs <NUM> (including individual tab 76A) extending therefrom that are conductively coupled via a conductive coupler <NUM> (also referred to as an anode collector). Although not labeled, the one or more spacers (e.g., conductive spacers) may be located between respective tabs in the set of tabs <NUM>. The conductive coupler <NUM> may be a pin that extends vertically through the set of tabs <NUM> and spacers located between respective tabs. Additionally, or alternatively, one or more welds <NUM> may also conductively couple the set of tabs <NUM> and spacers. In accordance with at least some of examples of the disclosure, as described below, conductive coupler <NUM> may be a rivet that extends vertically through set of tabs <NUM> and spacers that also mechanically attaches the individual tabs <NUM> and spacers to each other.

Each anode electrode plate 72A includes a current collector or grid <NUM>, a tab 76A extending therefrom, and an electrode material. The electrode material (or anode material) may include elements from Group IA, IIA or IIIB of the periodic table of elements (e.g. lithium, sodium, potassium, etc.), alloys thereof, intermetallic compounds (e.g. Li-Si, Li-B, Li-Si-B etc.), or an alkali metal (e.g. lithium, etc.) in metallic form.

Cathode tabs <NUM> may be constructed in a similar manner as anode tabs <NUM>. The cathodes include a set of electrode plates <NUM> (including individual cathode electrode plates 74A) with a set of tabs <NUM> (including individual tab 78A) extending therefrom. As labelled in <FIG>, e.g., one or more spacers (e.g., conductive spacers 86A-86C) may be located between respective tabs in the set of tabs <NUM>. The conductive coupler <NUM> connects the set of tabs <NUM> and spacers <NUM>. Conductive coupler <NUM> or other cathode collector may be connected to conductive member 60A. Conductive member 60A, shaped as a spacer plate, may comprise titanium, aluminum/titanium clad metal or other suitable materials. Conductive member 60A allows cathode tabs <NUM> to be electrically coupled to electronic components outside of battery <NUM>. Each tab of the set of tabs <NUM> (including, e.g., individual tab 78A) may be additionally, or alternatively, attached to each other via laser weld(s) <NUM>.

In accordance with at least some of examples of the disclosure, as described below, conductive coupler <NUM> may be a rivet that extends vertically through set of tabs <NUM> and spacers <NUM> that also mechanically attaches the individual tabs <NUM> and spacers <NUM> to each other.

Each cathode electrode plate 74A includes a current collector (not shown) or grid, an electrode material and a tab 78A extending therefrom. Tab 78A comprises conductive material (e.g., aluminum, etc.). Tab 78A comprises conductive material (e.g., copper, titanium, aluminum, etc.). Electrode material (or cathode material) may include metal oxides (e.g., vanadium oxide, silver vanadium oxide (SVO), manganese dioxide, etc.), carbon monofluoride and hybrids thereof (e.g., CFx+MnO2), combination silver vanadium oxide (CSVO), lithium ion, other rechargeable chemistries, or other suitable compounds.

<FIG> is a conceptual schematic diagram illustrating a magnified view of a portion of cathode tabs <NUM> of battery <NUM>. <FIG> is a cross-section view of the stack of cathode tabs <NUM> shown in <FIG>. As shown, electrodes plates <NUM> of cathode <NUM> includes cathode electrode plates 74A, 74B, 74C (among others) in a stacked configuration. Cathode tabs 78A, 78B, 78C extend from cathode electrodes plates 74A, 74B, 74C, respectively, and exhibit the same stacked configuration as electrode plate <NUM>. At least one spacer is located between each respective tab. For example, spacer 86A is located between tabs 78A and tab 78B, and two spacers 86B and 86C are located between tab 78B and tab 78C.

For ease of description and illustration, not all the tabs and spacers of cathode stack <NUM> are labelled in <FIG> and <FIG>. However, it is understood that the description of tabs 78A-78C and spacers 86A-86C also may apply to any of the tabs and spacers shown in <FIG> and <FIG>. Additionally, while <FIG> is described with regard to cathode stack <NUM> it is contemplated that the same configuration is applicable to anode stack <NUM> of battery <NUM> shown in <FIG>.

In some examples, spacer 86A ensures tabs 78A and 78B are substantially straight extending from plates 74A and 74B, respectively, and are not bent during a subassembly process to connect the set of tabs <NUM> (including, e.g., individual tab 78A) for cathode stack <NUM>. While a single spacer 86A is depicted as being placed between two tabs, more than one spacer may be placed between two tabs, such as, e.g., spacers 86B and 86C between tabs 78B and 78C.

Spacers 86A-86C may comprise a conductive material, e.g., such that the each of the tabs are electrically interconnected. For electrode plates related to anode stack <NUM>, titanium and alloys thereof or other suitable materials are used. For electrode plates related to cathode stack <NUM>, titanium, nickel, aluminum, alloys thereof or other suitable materials are used.

Spacers 86A-86C may include a variety of shapes. Exemplary spacers include a substantially H-shaped spacer, substantially rectangular, circular, or include at least one triangular shape (e.g. a single triangle, a hexagon etc.). Spacers 86A-86C may have different or substantially the same individual thicknesses in the z-direction labeled in <FIG>, e.g., to achieve different design criteria. For example, a thicker electrode plate may requires a thicker spacer. In the example in of <FIG>, spacer 86A may have substantially the same thickness of spacer 86B but spacer 86C may be thinner than spacers 86A and 86B. In some examples, the thickness of a spacer may range from about. <NUM> inches to about. <NUM> inches although other values are contemplated. Examples of spacers 86A-86C may include one or more of the example spacers described in <CIT>.

In some examples, the number of spacers and thicknesses of the individual spacer(s) between the tabs of cathode stack <NUM> and anode stack <NUM> may be selected such that tab bending is minimized yet still fits in the battery housing <NUM>.

As shown in <FIG> and <FIG>, cathode stack <NUM> may include rivet <NUM> extending through aperture <NUM> (shown in <FIG>) that runs through the set of cathode tabs <NUM> (including, e.g., individual tab 78A), spacers <NUM>, and conductive plate 60A in the z-direction. Rivet <NUM> includes body <NUM>, head <NUM>, and deformed tail <NUM>. Body <NUM> may be a solid body (e.g., as shown in <FIG>) or a body that include an inner lumen (e.g., as shown in <FIG>). Head <NUM> has a flanged portion that is located below conductive plate 60A. Similarly, deformed tail <NUM> has a flanged portion that is located above tab 78A, which is the "top" tab of the stack. In the example of <FIG> and <FIG>, spacer 86D is between tail <NUM> and tab 78A. In such an example, spacer 86D may be thicker and other more structurally rigid than tab 78A, e.g., to prevent head <NUM> of rivet <NUM> from "pulling-through" tab 78A if spacer 86D was not present. In other examples, tail <NUM> may be directly adjacent to tab 78A.

The flanged shape of head <NUM> and deformed tail <NUM> allows rivet <NUM> to fasten or otherwise mechanically attach cathode tabs <NUM>, spacers <NUM>, and conductive plate 60A to each other and prevent the stack from becoming detached from each other. As will be described in further detail below, before being deformed, tail <NUM> may be inserted into aperture <NUM> such that it extends out of the top of the stack of tabs <NUM>, spacers <NUM>, and conductive plate 60A. Subsequently, tail <NUM> is deformed to form the flange and attaches the stack of tabs <NUM>, spacers <NUM>, and conductive plate 60A together.

Rivet <NUM> may fix and define the thickness of the stack of tabs <NUM>, spacers <NUM>, and conductive plate 60A shown in the z-direction to correspond to the thickness of body <NUM> in the z-direction. In some examples, rivet <NUM> may apply a compressive force between head <NUM> and tail <NUM>, e.g., to counteract a force in the other direction that would otherwise cause tabs <NUM> and spacers <NUM> from separating. In this manner, the stack of tabs <NUM> are prevented, e.g., from "fanning," e.g., spreading apart in the z-direction, during the operating life of battery <NUM> and preventing tabs <NUM> from losing electrical interconnect between each other.

In some examples, rivet <NUM> is configured to keep the stack of tabs <NUM> together such that weld(s) <NUM> does not receive the "book opening" mechanical loading. Weld(s) <NUM> may be present in assemblies including rivet <NUM> in stack of tabs <NUM> to provide a robust electrical connection, e.g., between the respective tabs. Long-term, corrosion and surface oxidation may degrade the interface contacts, thus, the need for the weld.

In some examples, the height (in the Z-direction) of rivet <NUM> is selected based on the stack modeling described above. The modeling work may suggest just one rivet for all production variation options, or if too variable, the individual tab/spacer stacks can be actively measured during manufacturing before selecting any of several premade rivet heights for a particular stack.

Rivet <NUM> may be formed from any suitable material such as stainless steel (e.g., <NUM> series stainless steel), monel or other nickel-copper alloy, and/or nickel. In some examples, rivet <NUM> may be an electrically conductive material such that rivet <NUM> functions to electrically couple the individual tabs <NUM>, spacers <NUM>, and conductive plate 60A together, e.g., alone or in combination with other features such as welds <NUM> and/or conductive spacers <NUM>. In other examples, rivet <NUM> may be formed of an electrically insulating material.

<FIG> is a photograph illustrating example rivet <NUM> that may be employed in examples of the disclosure. Rivet <NUM> include head <NUM>, tail <NUM>, and body <NUM> that extends between head <NUM> and tail <NUM>. Rivet <NUM> is shown in a state prior to tail <NUM> being deformed as shown in <FIG>, for example. Body <NUM> of rivet <NUM> has an outer diameter D that is smaller than the size of aperture <NUM> extending through the stack of tabs <NUM>, spacers <NUM>, and conductive plate 60A shown in <FIG> and <FIG>. In some examples, body <NUM> of rivet <NUM> may have an outer diameter of about <NUM> mils or less, e.g., with the diameter of head <NUM> and deformed tail <NUM> being about <NUM> mils or greater. In examples in which body <NUM> includes an inner lumen rather than being solid, the thickness of the body walls may be about <NUM> mils. In some examples, the overall length of rivet <NUM> from head <NUM> to tail <NUM> may be about <NUM> mils or less. In some examples, the overall height (in the Z-direction) of the combination of tabs <NUM> and spacers <NUM> may be about <NUM> inches (e.g., +/- <NUM> inches). Other values are contemplated.

<FIG> is a schematic diagram illustrating an example apparatus <NUM> for deforming tail <NUM> when arranged with cathode tabs <NUM> and spacers <NUM> to form a stacked assembly in which tabs <NUM> and spacers <NUM> are attached to each other via rivet <NUM>. <FIG> is a flowchart illustrating an example technique for attaching tabs <NUM> and spacers <NUM> to each other via rivet <NUM>. For ease of description, the example technique of <FIG> will be described with regard to apparatus <NUM> shown in <FIG>.

As shown in <FIG>, tabs <NUM> and spacers <NUM> may be stacked on body <NUM> of rivet <NUM> (<NUM>). For example, aperture <NUM> of the individual tabs of tabs <NUM> and individual spacers <NUM> may be sequentially placed over tail <NUM> onto body <NUM> in the order and arrangement desired, e.g., in the arrangement shown in <FIG>. In other examples, tabs <NUM> and spacers <NUM> may be arranged in a stack initially with apertures aligned (e.g., using a fixture pin) and then placed as a single stack onto body <NUM> over tail <NUM>. The stacking may be accomplished manually or by robotic assembly devices (e.g., a pick and place robotic device).

Once tabs <NUM> and spacers <NUM> are assembled over rivet <NUM>, tail <NUM> may be deformed to attach tabs <NUM> and spacers <NUM> in the stacked arrangement (<NUM>). For example, retractable supports <NUM> may be used force swage <NUM> into tail <NUM> against fixed pin <NUM>, e.g., via a compressive force, to deform the edges of tail <NUM> outwardly and form a flanged end as shown in <FIG>. In some example, weld(s) <NUM> may then be formed, e.g., via laser welding or other suitable process, in tabs <NUM> and spacers <NUM> after rivet <NUM> has been installed. Alternatively, weld(s) <NUM> may be formed prior to installation of rivet <NUM>.

The example of <FIG> illustrates only one example technique for deforming tail <NUM> of rivet <NUM> within aperture <NUM> in the stack of tabs <NUM> and spacers <NUM> to attach tabs <NUM> and spacers <NUM> to each other. Other examples suitable technique may be employed as well as other types of rivets, such as, e.g., rivets with solid bodies.

As noted above, some example battery assemblies of the disclosure may additionally, or alternatively, include a shim on the "top" of the stack of tabs <NUM> and spacers <NUM>, e.g., to prevent "fanning" of the tabs <NUM> as described herein. <FIG> is a schematic diagram illustrating an example of battery <NUM> including shim <NUM>. As shown in <FIG>, shim <NUM> is located on stack of tabs <NUM> and spacers <NUM> of cathode stack <NUM>. In the example of <FIG>, shim <NUM> is not directly on top of tab 78A but instead is separated from tab 78A by spacer 86D. In other examples, shim <NUM> may be located directly on tab 78A. Although not shown in <FIG>, in some examples, welds <NUM> may be extended to include shim <NUM> along the side of the stack assembly depending on the material used to form shim <NUM>.

Additionally, shim <NUM> is located on stack of tabs <NUM> of anode stack <NUM> in a similar fashion. Shim <NUM> is a single member that spans gap <NUM> between stack of tabs <NUM> of cathode stack <NUM> and stack of tabs <NUM> of anode stack <NUM>, which also includes spacers (not labelled) between the individual tabs in the stack. While shim <NUM> is a single member in the example of <FIG>, in other examples, battery <NUM> may include one shim located on the stack of tabs and spacers for cathode stack <NUM> and another shim located on the stack of tabs and spacers for anode stack <NUM>.

In some examples, rather than being a separate component, shim <NUM> may be included as an integral feature of another component, e.g., of an insulative component. For example, in some examples, shim <NUM> may be a portion of another typical insulator used to isolate electrical polarities within the battery <NUM>, e.g., a headspace insulator, a stack insulator, and/or a feedthrough insulator. In some examples, shim <NUM> may be attached or otherwise included as a foldable feature of the component to allow for ease of assembling battery <NUM>, while also preventing against the occurrence of inadvertently not being installed during the assembly of battery <NUM>.

Although not shown in <FIG>, when battery housing <NUM> is assembled with top portion 50B (shown in <FIG>) and bottom portion 50A being sealed or otherwise attached to each other to form housing <NUM>, the thickness of shim <NUM> (in the z-direction) may be selected such that the top surface of shim <NUM> comes into contact with the inner surface of top portion 50B of battery housing <NUM>. In some examples, the contact between the top surface of shim <NUM> and the inner surface of top portion 50B of housing <NUM> may apply a compressive force (represented by arrows <NUM> in <FIG>) or otherwise prevent cathode stack <NUM> and anode stack <NUM> from fanning. For example, when top portion 50B is attached to bottom portion 50A of housing <NUM>, e.g., via a weld around the perimeter of housing <NUM> at the interface between top and bottom portion 50B and 50B, compressive force <NUM> may be applied to the stack of tabs <NUM> of cathode <NUM> and the stack of tab <NUM> of anode <NUM> between the top and bottom portions 50B and 50A by way of shim <NUM>. In this manner, compressive force <NUM> may prevent the stack of tabs <NUM> of cathode <NUM> and the stack of tab <NUM> of anode <NUM> from "fanning," e.g., during the operating life of battery <NUM>.

Shim <NUM> may be formed of any suitable material. In some examples, shim <NUM> may be formed of an electrically insulating material, e.g., to prevent electrical coupling of cathode stack <NUM> and anode stack <NUM> by way of shim <NUM> and/or electrical coupling of cathode stack <NUM> and/or anode stack <NUM> to housing <NUM>. Example insulating materials may include polypropylene, polyethylene, and/or the like. In other example, shim <NUM> may be formed of an electrically conductive material, such as titanium, stainless steel, and/or the like. In some examples, spacer 86D between top tab 78A of cathode <NUM> as well as the spacer between shim <NUM> and top tab 76A of anode <NUM> may be electrically insulating to prevent electrical coupling between the respective electrode tabs and shim <NUM>. In other examples, shim <NUM> may be configured such that the compressive force is applied once the cathode stack <NUM> and/or anode stack <NUM> begin to start fanning, e.g., at some point during the operating life of battery <NUM>.

<FIG> is a schematic diagram illustrating an example of shim <NUM>. As shown, shim <NUM> does not have a constant thickness but instead exhibits a thickness T1 on one side of shim <NUM> and thickness T2 on the other side of shim <NUM>. This difference in this may account for the differences in distance between the tab/spacer stack of cathode stack <NUM> and the inner surface of top portion 50B of housing <NUM> compared to the distance between the tab/spacer stack of anode stack <NUM> and the inner surface of top portion 50B of housing <NUM> when housing <NUM> is assembly around the internal components of battery <NUM>.

As shown, in some examples, shim <NUM> may include posts 122A and 122B. Post 122A may be configured to fit within a portion of aperture <NUM> of the stack of tabs <NUM> and spacers <NUM> of cathode stack <NUM>. Similarly, post 122B may be configured to fit within a portion of a similar aperture in the stack of tabs/spacers of anode stack <NUM>. This feature may facilitate the registration or alignment of shim <NUM> with respect to anode stack <NUM> and cathode stack <NUM>, and maintain shim <NUM> in place, e.g., before, during, and/or after top portion 50B and bottom portion 50A of housing <NUM> are assembled. Such a design may be utilized in cases in which a rivet, such as, rivet <NUM>, does not extend through the stack of tabs and spacers of the anode stack and cathode stack. For examples including a rivet in one or both of the anode stack and cathode stack, shim <NUM> may include another type of registration feature (e.g., indentions into shim <NUM> rather than protrusion such as posts 122A and 122B) other than that shown in <FIG>, e.g., so that the rivet and shim may both prevent fanning of the stack of tabs during the operating life of the battery.

<FIG> is a conceptual diagram illustrating another example battery <NUM>. Battery <NUM> may be similar to the other battery assemblies described herein and like features are numbered similarly. <FIG> illustrates an example in which shim <NUM> is employed between the inner surface of the top portion 50B of housing <NUM> and cathode stack <NUM> and anode stack <NUM>. As described above, the contact between the top surface of shim <NUM> and the inner surface of top portion 50B of housing <NUM> may apply a compressive force (represented by the two arrows in <FIG>) or otherwise prevent cathode stack <NUM> and anode stack <NUM> from fanning. For example, when top portion 50B is attached to bottom portion 50A of housing <NUM>, e.g., via a weld around the perimeter of housing <NUM> at the interface between top and bottom portion 50B and 50B, the compressive force may be applied to the stack of tabs <NUM> of cathode <NUM> and the stack of tab <NUM> of anode <NUM> between the top and bottom portions 50B and 50A by way of shim <NUM>. In this manner, the compressive force may prevent the stack of tabs <NUM> of cathode <NUM> and the stack of tab <NUM> of anode <NUM> from "fanning," e.g., during the operating life of battery <NUM>. In some examples, shim <NUM> may be configured such that the compressive force is applied once the cathode stack <NUM> and/or anode stack <NUM> begin to start fanning, e.g., at some point during the operating life of battery <NUM>.

Claim 1:
A battery assembly (<NUM>) for an implantable medical device (<NUM>), the assembly (<NUM>) comprising:
an electrode stack (<NUM>, <NUM>) comprising a plurality of electrode plates (<NUM>, <NUM>), wherein the plurality of electrode plates (<NUM>, <NUM>) comprises a first electrode plate (72A, 74A) including a first tab (76A, 78A) extending from the first electrode plate (72A, 74A) and a second electrode plate (74B) including a second tab (78B) extending from the second electrode plate (74B);
a spacer (<NUM>) between the first tab (76A, 78A) and the second tab (78B); and
a rivet (<NUM>) extending through the first tab (76A, 78A), second tab (78B), and spacer (<NUM>), wherein the rivet (<NUM>) is configured to mechanically attach the first tab (76A, 78A), second tab (78B), and spacer (<NUM>) to each other.