High-energy battery electrodes load up on sulfur

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.