High-performance lithium-ion electro- chemical cells and batteries have been developed to satisfy a need for longer lifetimes and greater capacities in the power supplies of the life-support systems attached to space suits. These and similar cells and batteries could also be used on Earth to satisfy requirements for high energy densities, high power levels, and long lifetimes in a variety of applications, including electric vehicles, medical electronic equipment, communication equipment, uninterruptible power supplies, and power tools.
One prototype battery, rated at a nominal power of 900 W, was assembled from five prismatic cells dimensioned to fit the spacesuit battery compartment. The battery can be discharged at any temperature between –40 °C and +55 °C. Each cell is rated at a nominal discharge capacity of 45 Ah. Each cell was found to be capable of delivering a charge of 47 Ah while maintaining a voltage of at least 2.5 V, or delivering a charge of 45 Ah at a current of 5 A while maintaining a voltage of at least 3.2 V. These cells have been designed to enable the fabrication of a space-suit battery that weighs less than does the present silver/zinc space-suit battery while offering a capacity, rate capability, and lifetime greater than those of the present battery, which is rated at a capacity of 29.5 Ah and a “wet” lifetime of 425 days.
At a current of 2.5 A, these cells are characterized by a mass-specific energy density of 158 Wh/kg and a volumetric energy density of 377 Wh/L. They have been demonstrated to be capable of sustaining a continuous current of 80 A while delivering a charge of 35 Ah, as well as a capability for pulse discharge at a current of 250 A.
The prismatic cell is protected by a thick-walled stainless-steel case that affords protection against crushing and puncturing. The five-cell battery weighs 12.3 lb (has a mass of 5.6 kg) — 2 lb (0.9 kg) less than does an advanced silver/zinc space-suit battery. At a discharge current of 3.8 A, this battery was found to deliver 47 Ah at a voltage above 16 V; in so doing, it exhibited 59 percent more capacity than the 29.5 Ah capacity specified for the present silver/zinc battery. This greater capacity could support a mission as long as 12 hours. In addition, whereas the silver-zinc battery exhibits short “wet” life and large capacity fade, the present Li-ion battery retains a significantly greater fraction of its initial capacity for a longer time.
This work was done by Grant M. Ehrich and Michael J. Hetzel of Yardney Technical Products Inc. for Johnson Space Center.