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Smart Battery Tells You When It's About To Explode
sciencehabit writes Material scientists have found a clever way to alert users of damaged batteries before any hazard occurs. A typical lithium-ion cell consists of a lithium oxide cathode and a graphite anode, separated by a thin, porous polymer sheet that allows ions to travel between the electrodes. When the cell is overcharged, microscopic chains of lithium, called "dendrites," sprout from the anode and pierce through the polymer separator until they touch the cathode. An electrical current passing through the dendrites to the cathode can short-circuit the cell, which causes overheating and, in some cases, fire. Attempts to stop dendrite formation have met with limited success, so the researchers tried something different. They built a "smart" separator by sandwiching a 50-nanometer thin copper layer between two polymer sheets and connecting the copper layer to a third electrode for voltage measurement. When the dendrites reach the separator, the voltage between the anode and the copper layer drops to zero, alerting users that they should change the damaged battery while it is still operating safely—disaster averted.
mmmm, I work in the Electronics recycling industry. When most (and I do mean most) laptops come in for repair, the typical thing is that the battery cells are dead but the system works fine.
http://www.liveleak.com/view?i...
User was installing a new battery that failed due to shorting when installed.
Another story of it happening and photo of the aftermath
http://miami.cbslocal.com/2014...
Different incident. User dropped the phone and the physical damage caused the battery short.
The typical failure mode from dendrite formation is the battery slowly drains itself from the high resistance connection between the cathode and anode that forms, and not a thermal runaway but it can happen. This is a common failure mode for NiCad batteries, but Lithium batteries are much more heat sensitive and the electrolyte when heated too much can release oxygen to fuel a runaway reaction. Battery failures in portable electronics are typically due to physical damage or poor quality chinese made batteries, especially when they omit the protection circuits.
A excellent short primer on Lithium Ion battery failures. Prompted by the recent airline industry incidents.
http://www.ntsb.gov/news/event...