The research team of professor Linda Nazar, graduate student David Xiulei Ji and postdoctoral fellow Kyu Tae Lee are one of the first to demonstrate robust electrochemical performance for a lithium-sulphur battery. The finding is reported in the online issue of Nature Materials.

The prospect of lithium-sulphur batteries has tantalized chemists for two decades, and not just because successfully combining the two chemistries delivers much higher energy densities. Sulphur is cheaper than many other materials currently used in lithium batteries. It has always showed great promise as the ideal partner for a safe, low cost, long lasting rechargeable battery, exactly the kind of battery needed for energy storage and transportation in a low carbon emission energy economy.

"The difficult challenge was always the cathode, the part of the battery that stores and releases electrons in the charge and recharge cycles," said Dr. Nazar. "To enable a reversible electrochemical reaction at high current rates, the electrically-active sulphur needs to remain in the most intimate contact with a conductor, such as carbon."

The Canadian research team leap-frogged the performance of other carbon-sulphur combinations by tackling the contact issue at the nanoscale level. Although they say the same approach could be used with other materials, for their proof of concept study they chose a member of a highly structured and porous carbon family called mesoporous carbon. At the nanoscale level, this type of carbon has a very uniform pore diameter and pore volume.

Using a nanocasting method, the team assembled a structure of 6.5 nanometre thick carbon rods separated by empty three to four nanometre wide channels. Carbon microfibres spanning the empty channels kept the voids open and prevented collapse of the architecture.