Phones, laptops and other personal devices have boomed over the past few decades thanks to lithium-ion batteries, but as climate change demands more powerful batteries for electric vehicles and grid-scale renewable energy storage, lithium-ion technology may no longer be enough. The theoretical capacity of lithium-metal batteries is an order of magnitude larger than that of lithium-ion batteries, but its disadvantage is that it is “flammable and explosive.” According to a paper published in the journal Matter on November 9, researchers at the University of Chicago have proposed a way to solve this decades-long problem: using solvo-free inorganic molten salts to create high energy density, safe batteries.
The researchers say they have developed a non-flammable, non-volatile system that is safe and can increase the energy density by two times compared to lithium-ion batteries.
Traditional lithium-metal batteries rely on an electrolyte made by dissolving lithium salts in a solvent. Those volatile, flammable solvents raise safety concerns. To solve this problem, the researchers tried different solvents, or modified the concentration of salt. There has been a trade-off in such attempts: batteries that use solid inorganic substances as electrolytes are safer; Batteries that use liquid electrolytes are more powerful. The result is either unsafe batteries or batteries that do not live up to the enormous theoretical capabilities of lithium metal batteries.
The Chicago team took a novel approach this time. They make lithium liquid by melting it instead of dissolving it. This requires the creation of a new salt component that melts at low temperatures. The challenge is to reach a temperature where the lithium salts melt, but the lithium metal in the rest of the battery does not.
Pure lithium chloride melts at temperatures slightly above 600 ° C, and lithium metal melts at 180°C, which means that any useful molten salt electrolyte must have a much lower melting point. So, the team created a salt that melts at 45°C, obtaining a powerful battery that can operate safely at 80°C to 100°C.
The research team is also continuing to study the composition of salts with lower melting points, with the ultimate goal of developing a powerful lithium metal battery that can operate safely at room temperature.