Abstract

Lithium/sulfur cells are receiving significant attention as an alternative power source for zero-emission vehicles and advanced electronic devices due to the very high theoretical specific capacity of the sulfur cathode. However, the poor cycle life and rate capability have remained a grand challenge, preventing the practical application of this attractive technology. Here, we report that a Li/S cell employing a cetyltrimethyl ammonium bromide -modified sulfur-graphene oxide nanocomposite cathode can be discharged at rates as high as 6C and charged at rates as high as 3C while still maintaining high specific capacity, with a long cycle life exceeding 1500 cycles and an extremely low decay rate, perhaps the best performance demonstrated so far for a Li/S cell. The initial estimated cell-level specific energy of our cell was ∼500 W·h/kg, which is much higher than that of current Li-ion cells. Even after 1500 cycles, we demonstrate a very high specific capacity, which corresponds to ∼414 mA·h/g of electrode: still higher than state-of-the-art Li-ion cells. Moreover, these Li/S cells with lithium metal electrodes can be cycled with an excellent Coulombic efficiency of 96.3% after 1500 cycles, which was enabled by our new formulation of the ionic liquid-based electrolyte. The performance we demonstrate herein suggests that Li/S cells may already be suitable for high-power applications such as power tools. Li/S cells may now provide a substantial opportunity for the development of zero-emission vehicles with a driving range similar to that of gasoline vehicles. © 2013 American Chemical Society.