TiN@C nanocages as multifunctional sulfur hosts for superior lithium-sulfur batteries.

The lithium polysulfide (LiPS) shuttle effect and low redox kinetics are the key problems that hinder performance improvement and prevent achieving the commercial requirements for lithium-sulfur batteries (LSBs), and the reasonable construction of sulfur hosts is one effective strategy to relieve the polysulfide shuttle effect and improve redox kinetics. Herein, N-doped carbon nanocages decorated with homogeneously dispersed TiN nanoparticles (TiN@C NCs) as multifunctional sulfur hosts are designed for superior LSBs. Carbon nanocages provide space to mitigate volume expansion and provide additional physical adsorption to trap the LiPSs. Polar TiN nanoparticles not only exhibit the chemisorption capacity for LiPSs, but also catalyze and promote the conversion of long-chain LiPSs to LiS/LiS in the reduction process as well as the decomposition of LiS in the oxidation reaction, which significantly boosts electron/ion transport and decreases the potential barrier. Therefore, the S/TiN@C NC cathode has an excellent electrochemical capacity of 1485.7 mA h g at 0.1 C. In particular, the cathode demonstrates high capacity reversibility after 500 cycles at 3 C with a retention of about 73.1%, which is equivalent to a slow capacity decay rate of 0.053% per cycle.