TiN as a simple and efficient polysulfide immobilizer for lithium-sulfur batteries

Lithium-sulfur batteries are believed to be potential next-generation electrochemical devices which will satisfy the increasing market demands due to their high energy density, low cost and environmental friendliness. However, the practical application of Li-S batteries is still hindered by poor cycle stability and rate capability caused by the low electronic conductivity of sulfur and dissolution of intermediate polysulfides. Here, we employ easily-obtained titanium nitride (TiN) as a highly efficient immobilizer to trap polysulfides via a chemical mechanism. TiN also possesses high electronic conductivity which helps in achieving a high sulfur utility and an excellent rate capability. At 0.5C, the TiN-based sulfur composite cathode demonstrates a high initial reversible capacity of 1012 mA h g(-1) and a long cycle life of over 200 cycles with a decay rate of 0.2% per cycle. Even at 5C, the reversible discharge capacity is still higher than 550 mA h g(-1). The outstanding electrochemical performance is ascribed to the strong chemisorption effect between TiN and polysulfides.