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.