Researchers at the DoE’s Oak Ridge National Laboratory (ORNL) have developed a lithium sulfur battery that is not only cheaper and safer than lithium ion batteries, but it can store four times as much energy as its li-ion counterparts. Used in small electronics and electric vehicles, lithium ion batteries are a standard for energy storage, but lithium sulfur batteries—which are already used in some solar aircraft—have the potential to succeed as an alternative with much higher energy density – and ORNL’s all-solid Li-S batteries are testing as safer and more durable than current Li-ion’s.
As Extreme Tech points out, the instability of lithium ion batteries was clearly seen in the flammability of the recent Boeing 787 Dreamliner aircraft, grounded shortly after they began flights due to on-board battery fires. Previous lithium sulfur batteries have also been susceptible to similar faults. The electrolytes in Li-ion and Li-S batteries—which convert chemical energy to electrical energy have previously been liquid. Gizmag explains that this is a “double-edged sword.. the liquid electrolyte is an excellent conductor because of how it dissolves the lithium compounds, but this dissolution also causes the battery to break down prematurely,” in addition to the liquid itself being flammable.
Researchers at ORNL however, have created cathodes and solid electrodes from lithium polysulfidophosphates, overcoming some of the issues of instability seen in previous batteries. The lithium polysulfidophosphates, a sulfur product, “virtually free,” as sulfur is a byproduct from the petrochemical industry. Additionally, they have a huge capacity “of 1,200 milliamp-hours (mAh) per gram after 300 charge/discharge cycles; a lithium-ion cathode, on the other hand, has a capacity of just 140-170 mAh/g” With a lower voltage than lithium-ion cathodes, this eight-fold increase translates into a four-fold increase in energy density.
Currently in the prototype phase, ORNL has applied for patents for the lithium polysulfidophosphates technology.