Browse Prior Art Database

PULSE METHOD TO REDUCE IRREVERSIBLE CAPACITY FADE IN IMPLANTABLE SECONDARY BATTERIES

IP.com Disclosure Number: IPCOM000020255D
Publication Date: 2003-Nov-06

Publishing Venue

The IP.com Prior Art Database

Abstract

A system and method of battery discharge within an implantable medical device interferes with degradation reactions, thereby reducing the rate of capacity fade associated with a rechargeable battery. More particularly, the battery is drained through the use of dynamically applied current pulses at a relatively high rate for a short time so as to disrupt the degradation reactions that occur in such a battery. The frequency and amplitude of such pulses provides the net average current drain needed to power the implant device for its intended application. By not allowing the degradation reactions to reach steady-state, and/or by dispersing the degradation byproducts before they can irreversibly contaminate electrode interface layers, the rate of capacity fade is reduced.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 14% of the total text.

PULSE METHOD TO REDUCE IRREVERSIBLE CAPACITY FADE

IN IMPLANTABLE SECONDARY BATTERIES

Summary

The present invention relates to implantable medical devices, and more particularly to implantable medical devices that utilize a secondary battery, i.e., a rechargeable battery, that does not need to have stored therein the total energy used over the service life of the medical device at the time of implant.

Secondary batteries can advantageously increase the longevity of implantable devices while reducing overall device size. This is because the total energy used over the service life of the implantable device does not need to be stored in the device at the time of implant.

Secondary batteries, however, are subject to different forms of capacity fade over time as they are cycled repeatedly in charge and discharge modes. Such capacity fade decreases the time between charging cycles and can limit the useful life of the implanted device when the frequency of recharge becomes excessive.

Some mechanisms of capacity fade, in Lithium Ion batteries for example, are related to degradation reactions at an electrode interface layer whose steady state rates are related to the electrochemical potential of the secondary cell. Secondary cells used in implant applications with low average rates of discharge allow reaction products to build up in local concentration where they can support subsequent irreversible degradation reactions.

The present invention is directed to a method of battery discharge, which avoids steady state low average rates of discharge, and thereby disrupts the degradation reactions and/or disperses degradation byproducts before they irreversibly contaminate the electrode interface layer. As a result, the invention reduces the rate of capacity fade associated with the secondary battery.

More particularly, the present invention dynamically applies current pulses to drain the secondary battery of an implant device, or other device having a secondary battery, at a relatively high rate for a short time so as to disrupt the degradation reactions that occur in such a battery. The frequency and amplitude of such pulses provides the net average current drain needed to power the implant device for its intended application. By not allowing the degradation reactions to reach steady-state, and/or by dispersing the degradation byproducts before they can irreversibly contaminate electrode interface layers, the rate of capacity fade is advantageously reduced.

In accordance with one aspect of the invention, the amplitude of the current pulses used to discharge the battery is selected to be at an amplitude that would discharge a fully charged implanted secondary cell, i.e., a rechargeable battery, in less than one hour if applied continuously. The interval between the pulses allows a lower average current drain that extends the discharge time of the battery.

In accordance with another aspect of the invention, the amount of battery usage over a period of time be...