Patent Application
20070292600
The following detailed description refers to the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention.
A single-stage compaction system for pressed powder electrodes is described herein. The system relieves the need for pre-compacting the powder. The present disclosure provides for the use of controlled compaction of powder around a fixed collector to allow single stage compaction and provide a substantially centered location of the current collector in the cathode. A centered collector aids in the prediction of battery life tests and optimizes impedance in a battery cell. The electrode is compressed substantially simultaneously from both directions while the collector is held in place, allowing for better flow of powder in and about the collector. Single stage compaction allows for more consistent manufacturing results and increased ease of process automation.
According to various embodiments of the system, the pistons are adapted to be actuated using springs. Various embodiments of the system use standard die springs. The powder 110 can include CFx (carbon monofluoride) with a conductive filler such as graphite or acetylene black, and a binder, such as PTFE (polytetrafluoroethylene) according to an embodiment. The binder includes a carbon-based conductive material according to various embodiments. The current collector 106, or tab, includes a stainless steel material in an embodiment. The tab may be constructed of nickel, aluminum, or other metals in various embodiments.
The pistons 104 are adapted to be actuated using forced air, hydraulics, a servo-motor, or any mechanism to deliver force equally to both pistons, according to various embodiments. The resulting electrode pellet can be adapted to be used in a battery for powering an implantable medical device. Examples of implantable medical devices include pacemakers, defibrillators, neurostimulators, among others. The present system can be incorporated into any pressed powder medium rate battery.
One aspect of this disclosure relates to a system for manufacturing a pressed powder electrode for an electrochemical power source for use with an implantable medical device. The system includes means for surrounding a current collector with layered sections of electrode powder. The surrounding means can include a die or other (usually metallic, although composites could be used in an embodiment) structure. The system also includes means for compacting the electrode powder against the current collector from opposite sides using springs having spring constants calculated to relieve a gap difference in equal strokes from each side. The gap difference indicates the distance from the first piston to the collector or the distance from the second piston to the collector, according to various embodiments. According to an embodiment of the system, the resulting electrode pellet includes a substantially centered current collector. The means for surrounding a current collector includes at least one clamping means, according to an embodiment. The clamping means holds the current collector parallel to the face of the compacting means, in an embodiment. The compacting means includes at least one forced air adapted to supply forced air to at least two opposing air cylinders to compact powder from opposite sides of the collector, according to one embodiment.
The die 202 may be adapted to hold the current collector in a variety of different orientations with respect to the die, according to various embodiments. A groove may exist in the die to allow the tab to move, according to an embodiment. The resulting electrode pellet can be used in a battery for powering implantable medical devices, such as pacemakers, defibrillators, neurostimulators, among others. The present system can be incorporated into any pressed powder medium rate battery.
In various embodiments, the cathode 406 may include compressed powder, dough or slurry. The cathode can be formed directly in the battery container or pressed or coated onto an electrically conductive material. In various embodiments, the cathode includes at least one metal oxide, metal sulphide, metal selenide, metal halide or metal oxyhalide compound or their corresponding lithiated forms. The cathode may include manganese, vanadium, silver, molybdenum, tungsten, cobalt, nickel, or chromium. The cathode may also include a main group compound such as carbon monofluoride or iodine. Other compositions of the cathode are within the scope of this disclosure.
The anode 404 may include carbon or a metal, according to various embodiments. The anode may include metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, tin, zinc or silver. Other compositions of the anode are within the scope of this disclosure.
Certain implantable medical devices (IMDs) have been developed to operate using batteries with pressed powder pellet electrodes.
Implantable medical device 700 can include a lead system 703, which after implantation electrically contact strategic portions of a patient's organs or vessels. Shown schematically are portions of device 700 including a monitoring circuit 702 for monitoring activity through one or more of the leads of lead system 703, and a therapy circuit 701 for delivering electrical energy through one or more of the leads to a patient. The device 700 also includes an energy storage component, which includes a capacitor 705 and incorporates at least one electrochemical power source, or battery 704, having one or more of the features of the capacitor embodiments described above. In addition to implantable heart monitor and other cardiac rhythm management devices, one or more teachings of the present system can be incorporated into electrochemical power sources used for other IMDs, such as neurostimulators, or into photographic flash equipment. The present system can be incorporated into any pressed powder medium rate battery.
According to an embodiment, medical device circuitry includes sensor circuitry adapted to provide a diagnostic function. The medical device circuitry may also include stimulation circuitry adapted to provide a therapeutic function, such as neurostimulation circuitry adapted to provide neurostimulation therapy. The medical device circuitry may include both sensor circuitry and stimulation circuitry. According to various embodiments, the electrochemical power source includes multiple electrodes electrically connected in series, connected in parallel, or connected in a combination of series and parallel, to provide the necessary electrical current to power the implantable medical device.
According to an embodiment, compacting the electrode powder includes compacting the electrode powder from each side substantially simultaneously. Surrounding the current collector includes holding the current collector in a fixed position using a die, according to various embodiments.
According to various embodiments, forming the pressed powder electrode includes pressing CFx powder. Forming the pressed powder electrode includes forming the electrode with a nickel, aluminum or stainless steel current collector, according to various embodiments.
One of ordinary skill in the art will understand that, the modules and other circuitry shown and described herein can be implemented using software, hardware, and combinations of software and hardware. As such, the illustrated modules and circuitry are intended to encompass software implementations, hardware implementations, and software and hardware implementations.
The methods illustrated in this disclosure are not intended to be exclusive of other methods within the scope of the present subject matter. Those of ordinary skill in the art will understand, upon reading and comprehending this disclosure, other methods within the scope of the present subject matter.
This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
