In Situ Constructing a TiO2/TiN Heterostructure Modified Carbon Interlayer for Balancing the Surface Adsorption and Conversion of Polysulfides in Li-S Batteries

Severe shuttle effect and sluggish reaction kinetics caused by lithium-polysulfides have always been the dominant factor to reduce the actual energy density of lithium-sulfur batteries. It's very important to simultaneously balance the surface adsorption and redox conversion of the lithium-polysulfides. Herein, a TiO2/TiN heterostructure and in situ N-doping modified multifunctional carbon interlayer is designed and constructed using a melamine foam as the matrix material at a relatively low temperature and without NH3 atmosphere. Interestingly, TiO2 nano-particles decorated on the N-enriched melamine carbon foam can be partially in situ transformed into TiN during pyrolysis process. Based on the support of highly conductive and interconnected carbon skeletons, the N heteroatom and TiO2/TiN show good synergetic adsorption and conversion of the soluble lithium-polysulfides, whilst boosting the electrochemical performance of lithium-sulfur batteries. Consequently, when used the multifunctional carbon interlayer, the Super P/sulfur cathode based lithium-sulfur battery delivers a high initial discharge capacity of 814 mAh g(-1) at a high current rate of 2.0 C and maintain the 548 mAh g(-1) after 500 cycles. Even with the high sulfur loading of 7.5 mg cm(-2) and low E/S ratio of 4.7 mu L mg(-1), an acceptable areal capacity of 8.2 mAh cm(-2) can be obtained.