Life verification of large capacity Yardney Li-ion cells and batteries in support of NASA missions

Lithium-ion batteries have been used on a number of NASA missions and have been base-lined for use on a number of tip-coining aerospace applications. The Li-ion cells and batteries that have been developed together with Yardney Technical Products are especially attractive due to their high specific energy and energy density, good performance over a wide operating temperature range, as well as their good calendar and cycle life performance. However, given that the Li-ion technology is relatively new to the aerospace community and that mature, large capacity prototype cells have continued to evolve over the last 10 years, real-time performance test data is especially valuable in demonstrating the capabilities over a number of environmental and application specific conditions. For this reason, we have focused on performing a number of generic and mission specific performance life tests to establish the viability of the technology to meet current and future applications. In this work, we will describe the results of a number of generic cycle life tests, including 100% depth-of-discharge (DOD) cycling at various temperatures, partial DOD cycling simulating planetary orbiters and low earth orbit (LEO) satellite conditions, as well as partial DOD mission specific testing. We will also describe the results obtained from a number of calendar life tests where the cells were stored under different conditions, such as at different temperatures and different storage modes (i.e. open circuit voltage (OCV) conditions and storage under trickle charge conditions). Methods to quantify the capacity degradation and impedance growth of the batteries when subjected to different electrical and environmental conditions will be discussed, as well as, possible degradation mechanisms that can lead to reduced lifetime. Copyright (C) 2009 John Wiley & Sons, Ltd.