Long Term Operability of Li-ion Battery under Micro-gravity Condition Demonstrated by the Satellite “REIMEI”

Lithium-ion secondary cells are widely used for the space applications, today. Among these applications, REIMEI, which was launched in 2005, was one of the first satellites using lithium-ion battery. The off-the-shelf type cells designed using spinel manganese oxide for the positive and the graphitized carbon for the negative electrode were used. The cell case was made of aluminum laminated film and the structure was reinforced by the aluminum case filled with epoxy resin. Today, ten years has passed, and the battery experienced 55,000 cycles for charge and discharge. The current distribution between two batteries almost coincided together even after the long term operation, which revealed the stable performance of the lithium-ion secondary cells under the microgravity in space.