NTSB Materials Failure Analysis of Lithium-Ion Battery Incidents from the Boeing 787

The National Transportation Safety Board is an independent federal agency charged with investigating transportation accidents across aircraft, rail, pipeline, marine, highway, and hazardous materials platforms. Among these events, the agency investigated multiple incidents of eight-cell lithium-ion batteries that powered various systems of the Boeing 787 in 2013. Specifically, a mechanic servicing a Japan Airlines 787-8 gate parked at Boston Logan International Airport found heavy smoke and fire from the front of the auxiliary power unit (APU) battery case. This battery consists of eight lithium-ion cells connected in series and assembled in two rows of four cells, each based on a lithium cobalt oxide compound chemistry with a flammable electrolyte liquid. The investigation found that the thermal runaway of several of these battery cells led to the failure of the battery, which affected safety of flight at the time. This presentation will review the novel failure analysis process performed by the NTSB materials laboratory, specifically focusing on examining fire signatures, thermal damage mapping, computed tomography, and chemical analytical data. Along with optical and electron microscopy, the data helped recreate the sequence of events leading to thermal runaway. Along with details of battery manufacturing processes, the investigation resulted in multiple recommendations to prevent thermal runaway from impacting flight safety again.