Recipe for safer batteries—just add diamonds

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While lithium-ion batteries, widely used in mobile devices from cell phones to laptops, have one of the longest lifespans of commercial batteries today, they also have been behind a number of recent meltdowns and fires due to short-circuiting in mobile devices. In hopes of preventing more of these hazardous malfunctions researchers at Drexel University have developed a recipe that can turn electrolyte solution—a key component of most batteries—into a safeguard against the chemical process that leads to battery-related disasters.

To avoid dendrite formation and minimize the probability of fire, current battery designs include one electrode made of graphite filled with lithium instead of pure lithium. The use of graphite as the host for lithium prevents the formation of dendrites. But lithium intercalated graphite also stores about 10 times less energy than pure lithium. The breakthrough made by Gogotsi's team means that a great increase in energy storage is possible because dendrite formation can be eliminated in pure lithium electrodes.

"Battery safety is a key issue for this research," Gogotsi said. "Small primary batteries in watches use lithium anodes, but they are only discharged once. When you start charging them again and again, dendrites start growing. There may be several safe cycles, but sooner or later a short-circuit will happen. We want to eliminate or, at least, minimize that possibility."

Gogotsi notes that his group's discovery is just the beginning of a process that could eventually see electrolyte additives, like nanodiamonds, widely used to produce safe lithium batteries with a high energy density. Initial results already show stable charge-discharge cycling for as long as 200 hours, which is long enough for use in some industrial or military applications, but not nearly adequate for batteries used in laptops or cell phones. Researchers also need to test a large number of battery cells over a long enough period of time under various physical conditions and temperatures to ensure that dendrites will never grow.

"It's potentially game-changing, but it is difficult to be 100 percent certain that dendrites will never grow," Gogotsi said. "We anticipate the first use of our proposed technology will be in less critical applications—not in cell phones or car batteries. To ensure safety, additives to electrolytes, such as nanodiamonds, need to be combined with other precautions, such as using non-flammable electrolytes, safer electrode materials and stronger separators."