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

Abstract

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 µL mg−1, an acceptable areal capacity of 8.2 mAh cm−2 can be obtained.