Lithium-sulfur batteries could theoretically store an order of magnitude more energy by weight than today’s lithium-ion batteries. But because of sulfur’s low electrical conductivity, it’s hard to design a Li-S battery cathode with such a high energy storage capacity. Engineers compensate by adding conductive carbon-based compounds, but these materials reduce the amount of sulfur that can fit in the cathode, lowering the energy density. Now, a team of researchers has designed a Li-S cathode that holds up to 10 times as much sulfur as other designs (ACS Energy Lett. 2016, DOI: 10.1021/acsenergylett.6b00104). Arumugam Manthiram of the University of Texas, Austin; Yang-Kook Sun of Hanyang University; and their colleagues used a combination of acetylene black and multiwalled carbon nanotubes because their high conductivity leaves more room in the cathode for sulfur. The new cathode contains 10 mg of sulfur per cm2 compared with 1 to 2 mg per cm2 in previous designs, Manthiram says. A test battery made with the cathode and a lithium-metal anode had eight times the energy capacity of a typical cellphone battery. After charging and discharging 50 times, the new design maintained 91% of that capacity.