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Organic/inorganic sulfur may be key for safe rechargeable lithium batteries

Wednesday, October 11, 2017
One of the lithium sulfur coin batteries being developed in Penn State's Energy Nanostructure Laboratory (E-Nano). Image: Patrick Mansell

We have come a long way from leaky sulfur-acid automobile batteries, but modern lithium batteries still have some down sides. Now a team of Penn State engineers have a different type of lithium sulfur battery that could be more efficient, less expensive and safer.

"We demonstrated this method in a coin battery," said Donghai Wang, associate professor of mechanical engineering. "But, I think it could eventually become big enough for cellphones, drones and even bigger for electric vehicles."

Lithium sulfur batteries should be a promising candidate for the next generation of rechargeable batteries, but they are not without problems. For lithium, the efficiency in which charge transfers is low, and lithium batteries tend to grow dendrites — thin branching crystals — when charging that do not disappear when discharged.

The researchers examined a self-formed, flexible hybrid solid-electrolyte interphase layer that is deposited by both organosulfides and organopolysulfides with inorganic lithium salts. The researchers report in today's (Oct. 11) issue of Nature Communications that the organic sulfur compounds act as plasticizers in the interphase layer and improve the mechanical flexibility and toughness of the layer. The interphase layer allows the lithium to deposit without growing dendrites. The Coulombic efficiency is about 99 percent over 400 recharging discharging cycles.