Carbon/Sulfur Composites Stabilized with Nano-TiNi for High-Performance Li-S Battery Cathodes

In this work we proposed a novel strategy to prepare high-performance Li-S battery cathodes by nano-TiNi synergistically stabilizing C/S composites, whereby the TiNi/C/S hybrid composites were synthesized by infusing S gas into carbon black (CB) and nano-TiNi composites in vacuum. After several initial conditioning charge/discharge cycles, this unique TiNi/C/S hybrid nanocomposite cathode shows a high capacity (300 mAh/g based on total and 960 mAh/g based on S) with Coulombic efficiency of near 100% at 100 mA/g for around 300 cycles without obvious capacity decay. Due to its high electronic/ionic conductivity, the TiNi/C/S nanocomposite can retain an overall capacity of 150 mAh/g (480 mAh/g based on S) even at a higher current density of 10.0 A/g, demonstrating the outstanding rate capability. The exceptional performance of TiNi/C/S cathode can be ascribed to (i) the strong interactions between nano-TiNi and S to form metal disulfide clusters, (ii) the CB percolating throughout the composite to prevent nano-TiNi and metal sulfides particles from aggregating into large particles during lithiation/delithiation, (iii) the good electronic conductivity of TiNi and CB to facilitate transportation of electrons, and (iv) the flexibility of CB and TiNi alloy to accommodate large volumetric change during lithiation/delithiation. These synergistic interactions among TiNi, C and S provide a new material design strategy to achieve high overall performance of S cathodes for Li-S batteries.