Sunday, 29 May 2016: 15:55
Sapphire Ballroom A (Hilton San Diego Bayfront)
J. Y. Hwang (Hanyang University), A. Abouimrane (Qatar Environment & Energy Research Institute, HBKU), M. A. Khaleel (Qatar Environment and Energy Research Institute), I. Belharouak (Qatar Environment & Energy Research Institute, HBKU), A. Manthiram (The University of Texas at Austin), and Y. K. Sun (Hanyang University)
The Li–S batteries are becoming attractive due to the abundance of elemental sulfur and its environmental compatibility. In addition, sulfur undergoes a two-electron redox reaction with lithium and offers an extremely high theoretical specific capacity of 1675 mAh g−1 and a high energy density of 2600 Wh kg−1.1 Despite these advantages, several issues have hampered the practical use of Li–S batteries. For example, the insulating character of sulfur and lithium sulfide impede the full electrochemical utilization of sulfur. Moreover, the dissolution of lithium polysulfide inter-mediates in the electrolyte triggers undesirable shuttle reactions. Other issues such as low Coulombic efficiency, high self-discharge, and huge volume change remain unsolved. To overcome these drawbacks, several mitigation strategies have been explored by various research groups. One of the most followed routes deals with the mixing/impregnation/confinement of sulfur within highly conducting carbons. carbon nanotube-based composites have been used for high sulfur loading amount. Another approach is the use of metal oxides. In particular, TiO2 is a promising host for sulfur containment owing to its high absorption ability2. Further enhancement in the capacity and cycle life of Li–S batteries has been realized by Manthiram’s group by employing a free-standing interlayer (between the sulfur cathode and the separator) that plays the bifunctional role as a trap for mobile polysulfides and as an upper current collector for fast electron transport3.Herein, we synthesized and characterized (i) a S-HMT@CNT sulfur cathode comprised of hollow, spherical, nanostructured TiO2 and carbon nanotubes and (ii) DF-PCW interlayer comprised of highly porous carbon spheres and carbon nanotubes. The pores of TiO2 allowed for high sulfur loadings and accommodation of the volume expansion at the electrode level. The CNT component provided an overlap-ping network that improved both the electronic conductivity and mechanical strength of the S-HMT@CNT and DF-PCW. The pores in the carbon interlayer played the role of a medium that scavenged the dissolved lithium polysulfides, while improving Li-ion and electron transports. Owing to our cathode characteristics and cell design, the lithium–sulfur cell fabricated demonstrated good cycle life, high efficiency, and high rate capability. Of significance, the excellent cycling realized at the 2C and 5C rates is appealing for utilizing the lithium–sulfur batteries in high power applications
