A Scientific Methodology for Investigation of a Lithium Ion Battery Failure

Lithium-ion (rechargeable) batteries of various capacities and form factors appear in increasing varieties of consumer products including laptop computers, cellular telephones, digital cameras, portable music players, mini DVD players, children's toys, and cordless power tools. On occasion, the batteries in these products fail in a manner that includes overheating, case rupture, and even flaming combustion. Exponent has developed a systematic approach to lithium-ion battery failure investigations that has proven useful in identifying the root cause(s) of these failures. This approach includes collecting information about the incident, dissecting the remains of the incident device and battery pack, conducting visual, X-ray, and scanning electron-microscope examinations of failed and exemplar cells, and electrical testing of charging and battery protection system components. In this paper, we discuss the general approach developed, and provide examples of its application.