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

The lithium polysulfides (LiPSs) shuttle effect and low redox kinetics is the key problem that hinders the performance improvement and prevents the achievement of commercial requirement for lithium-sulfur batteries (LSBs), reasonable construction of sulfur hosts is one of the effective strategies to relieve the polysulfides shuttle effect and improve redox kinetics. Herein, N-doped carbon nanocages decorated with homogeneous dispersed TiN nanoparticle (TiN@C NCs) as multifunctional sulfur hosts are designed for superior LSBs. Carbon nanocage provides space to mitigate volume expansion and provides additional physical adsorption to trap the LiPSs. While polar TiN nanoparticle not only affords chemisorption capacity for LiPSs, but also catalyzes and promotes the conversion of long-chain LiPSs to Li2S2/Li2S in the reduction process as well as the decomposition of Li2S in the oxidation reaction, which significantly boosts electron/ion transport and decreases the potential barrier. Therefore, the S/TiN@C NCs cathode have excellent electrochemical capacity of 1485.7 mAh g-1 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.