Inexpensive Carbon Matrix for High Performance Lithium Sulfur Batteries

Batteries with multi-electron redox materials offer promise for increased performance relative to state of the art lithium-ion batteries. Lithium-sulfur (Li/S) batteries have two electron cathode materials (in addition to a lithium metal anode) and better than two times the specific energy of Li-ion batteries. However, several issues have prevented Li/S batteries from becoming more commercially viable. The sulfur cathode is both ionically and electronically insulating and so requires a conductive matrix. In addition, cycle life is limited by diffusion of polysulfides to the anode where they are reduced to Li/S2 becoming inactive; historically the cycle life has been relatively poor (<100 cycles). Recent literature reports indicate that a stable and conductive matrix is the key to achieving high capacity and long life in Li/S batteries. Using nanotemplated hard carbons, the utilization efficiency of the polysulfide cathode was increased from typical values of 30% or ~500 mAh/g to 80% or ~1300 mAh/g. In addition, by using dense conductive matrix formulations increases in cycle life to 400 cycles were obtained. TDA will develop ideal cathode compositions by engineering pore sizes of a highly conductive hard carbon matrix that contains polysulfide active materials. We will engineer the performance of templated carbons at a fraction of the cost. We are uniquely qualified to make these nanomaterials because for over ten years we have been developing sugar derived carbons for ultracapacitors, and through this work we have developed and have patented methods to control the nanopore size distribution. These mesoporous carbons are high purity, highly conductive and perhaps most importantly inexpensive. Commercial Applications and Other Benefits: The development of Li/S batteries, which are safe and economical, could be the next breakthrough in battery technology. Large scale introduction of PHEVs and HEVs would benefit society by both reducing our reliance on imported oil and reducing CO2 pollution which causes global warming. Since most of our imported oil is used as gasoline in vehicles, converting to cars that have better than 2 times the energy efficiency and run primarily on electricity can eliminate this burden. The dependence on foreign oil also reduces our national security, since oil imports have increasingly been used as political tools of the supplying countries.