Development of batteries for implantable applications.

摘要

Neuroprosthetic devices that electrically stimulate paralyzed muscles require implantable power sources with exceptional cycle life, safety, and sufficient energy and power density. Of the rechargeable battery technologies, lithium ion batteries have the highest energy density; however, they have limited cycle life of about 1000 cycles.; Nickel-hydrogen batteries, currently used in space applications are remarkable for long cycle life (40,000) and low maintenance; however they utilize high hydrogen pressures (60 atm) making them unsuitable for implantable applications. The present work involves design and development of low pressure nickel-hydrogen batteries (1 atm) by utilizing a metal hydride (MH) to store hydrogen, rather than as a negative electrode in the nickel-metal hydride battery.; A method to increase the exchange current density of the negative platinum electrode using cyclic voltammetry was developed. A nickel mesh was chosen as the current collector because of its low resistance and stability in alkaline solutions. The tested separators, zirconium oxide and polypropylene, were not significantly different from each other.; A pasted type nickel hydroxide electrode was fabricated by two means: screen printing and spatula pressing. The mechanism of electrode formation, the effect of different formation rates with and without overcharge and the effect of binder and nickel content on utilization were studied. Addition of filamentary nickel to the electrode increases the utilization by 10% by decreasing the oxygen evolution.; A low pressure nickel-hydrogen battery with and without MH was assembled. Charge and pressure data were analyzed to study the oxygen evolution, the recombination reaction and the self discharge of the cell. Oxygen evolution increases with the depth of charge; however the evolved oxygen recombines completely---70% during charging and the remainder during the first hour of the rest period. About 40-45% hydrogen from the metal hydride was used as fuel during cycling. The pressure composition isotherm was used to estimate the state of charge and to fuel gauge the cell. The NM is deactivated when exposed to KOH solution, increasing the hydrogen equilibration time.; Of the tested implantable lithium ion cells, Quallion outperformed the Wilson Greatbatch cells in cycle life. The conditions for maximum cycle life were determined.