This is one of the lithium-sulfur coin batteries being developed in Penn State's Energy Nanostructure Laboratory. Photo: Patrick Mansell, Penn State.A team of engineers at Penn State has developed a lithium-sulfur battery that could be more efficient, less expensive and safer than conventional lithium-ion batteries.
"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 cell phones, drones and even bigger for electric vehicles."
Lithium-sulfur batteries should be a promising candidate for the next generation of rechargeable batteries, because sulfur is inexpensive and produces a battery with a high charge capacity and energy density, but they are not without problems. They tend to form an inorganic coating on the battery that is brittle and cannot tolerate changes in volume or sustain high energy.
In addition, the electrolyte can dry up and the bulk lithium can corrode. Like conventional lithium-ion batteries, they also tend to grow dendrites – thin branching crystals – when charging that do not disappear when discharged. These dendrites can cause the battery to short-circuit and potentially catch fire.
As a way to overcome these problems, the researchers examined a self-formed, flexible, hybrid solid-electrolyte interphase layer that is deposited by both organosulfides and organopolysulfides with inorganic lithium salts. In a paper in Nature Communications, the researchers report that the organic sulfur compounds act as plasticizers in the interphase layer, improving its mechanical flexibility and toughness. The interphase layer also allows the lithium to deposit without growing dendrites, and produces a battery with a Coulombic efficiency of about 99% over 400 charging/discharging cycles.
"We need some kind of barrier on the lithium in a lithium metal battery, or it reacts with everything," said Wang. "Potentially, we can double the energy density of conventional DC batteries using lithium sulfur batteries with this hybrid organosulfide/organopolysulfide interface." They can also create a safer, more reliable battery.
To create their battery, the researchers used an ether-based electrolyte with sulfur-containing polymer additives, together with a sulfur-infused carbon cathode and a lithium anode. The organic sulfur in the electrolyte self-forms the interphase layers.
The researchers report that they "demonstrate a lithium-sulfur battery exhibiting a long cycling life – 1000 cycles – and good capacity retention".
This story is adapted from material from Penn State, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.