Destructive physical analysis of spaceflight qualified nickel-hydrogen battery cells

Abstract

Nickel-hydrogen (Ni-H/sub 2/) batteries are extensively used in the aerospace industry as the power system of choice in Earth-orbital spacecraft. The batteries are typically required to support a ten to fifteen year geosynchronous-Earth-orbit (GEO) mission or thousands of charge/discharge cycles in low-Earth-orbit (LEO). Reliability requirements for this application are extensive and include the routine destructive physical analysis (DPA) of sample flight production battery cells. Standard procedures have been developed over the past 15-years for the disassembly, handling and detailed analysis of the cell components. These include mechanical, thermal and impedance analysis, electrolyte concentration and distribution, gas management, corrosion, dye penetrant and radiographic inspection, and several chemical and electrochemical analytical procedures for the battery electrodes and separator materials. Electrolyte management is a critical issue in the electrolyte-starved Ni-H/sub 2/ cell design and procedures have been developed to particularly address this aspect of the DPA analysis. Specific analytical procedures for cell components includes nickel electrode active material and sinter substrate corrosion analysis, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), cobalt ion, potassium-carbonate and anion analysis. Many of these procedures are also applicable to aerospace battery systems in general and to other alkaline rechargeable batteries.