Although the replacement of metallic Li with carbon
intercalation negatives significantly improved the safety of
secondary Li cells, some concerns remain, particularly in
view of recent problems in the field [2]. Li-ion cells are not
immune to safety incidents since their thermal stability
limits are finite. We have found that cells deliberately
heated to high temperatures eventually undergo a thermal
runaway reaction, producing very high cell temperatures,
smoke and even fire [3]. This implies that under abusive
conditions, the potential exists to heat a cell beyond its
thermal stability limit, initiating the runaway reaction and
producing a safety incident. To date, safety engineering
has played a key role in mitigating potential safety problem.