Mining Contract: Evaluating the Inherent Safety of Li-ion Batteries in Portable Electronics Used in Underground Mine Environments

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

Li-ion batteries have become one of the most popular types of rechargeable battery for portable electronics. Li-ion technology provides enhanced energy storage capabilities that lengthen device runtime, shorten the recharge time, and extend the life of the battery. Beyond consumer electronics, Li-ion batteries are now growing in popularity for usage in underground mine safety equipment such as cap lamps, hand-held gas detectors, hand tools, and communications and tracking devices. Li-ion batteries also have well-known thermal runaway safety concerns. MSHA has issued a Program Information Bulletin regarding safety precautions for charging of Li-ion or lithium polymer batteries. With the tendency for Li-ion battery chemistries to undergo thermal runaway—creating a potential ignition source in a mine—it is important that the use of different Li-ion battery chemistries be evaluated as a means for reducing this hazard.

Under this contract, the University of Kentucky evaluated the inherent safety of a variety of Li-ion batteries used in portable electronics. Experiments involved crushing the Li-ion cells to produce internal short circuits while placed within methane-contaminated atmospheres to simulate the mining hazard. The potential ignition hazard was evaluated as a function of cathode and anode chemistry, electrolyte solvent, and state-of-charge (SOC).

The final report from this research recommended lithium titanate battery chemistry as the safest choice of those studied for underground mining environments. Lithium iron phosphate/graphite battery chemistry was deemed appropriate for use in mining environments, although not quite as safe as the lithium titanate battery chemistry. Battery cells featuring cobalt oxide or nickel manganese cobalt cathodes and graphite anodes were shown to be inherently more violent and energetic when crushed and are not recommended for use in underground mining environments. All of the battery chemistries tested in this research can be considered to be “safe” at 50% SOC.