As the size of the cell increases, the chance of some­thing hap­pening increases because you have an increased amount of mate­rial being exposed” says Dr. K.M. Abraham. “[Lithium-​​ion bat­teries] are not as for­giving as far as design and con­struc­tion are con­cerned. If you have quality con­trol issues, it can be very bad.”

Dr. Abraham is a bat­tery con­sul­tant and pro­fessor at North­eastern Uni­ver­sity in Boston and has been researching lithium-​​ion bat­teries since 1976.

Lithium-​​ion bat­teries are extremely power dense, deliv­ering a lot of elec­tricity from a rel­a­tively com­pact package. To do this they need extremely thin sheets of the plastic mate­rial to sep­a­rate the cath­odes and anodes inside the bat­tery. The large 32 volt bat­tery like those found in the 787 is made up of eight 3.7 volt cells. Dr. Abraham says the design and con­struc­tion of a bat­tery is crit­ical so that these sep­a­ra­tors are not dam­aged during man­u­fac­turing or during a battery’s use.

I always con­sider the sep­a­rator as a major source for a problem” Dr. Abraham says of the sheets that are 25 microns thick, around the same thick­ness as cellophane.

Read the article at Wired →