Recessed deposition of TiN into N-doped carbon as a cathode host for superior Li-S batteries performance

Abstract

In this work, we put forward a novel cathode host for Li-S batteries by loading titanium nitride (TiN) nanoparticles into the pores of N-doped carbon as a proof-of-concept. The selection of TiN arises from its strong binding ability with polysulfide and its exceptionally high conductivity of 5 × 106 S/m. As for N-doped porous carbon, it provides necessary physical adsorption and extra chemical adsorption sites from the N-doping. Besides the above advantages, the most substantial merit endowed to this structure is the pore-loaded TiN design. The carbon pore size confines the TiN precursors to the nanoscale and prevents otherwise subsequent agglomeration of TiN nanoparticles. Moreover, the pore-loaded TiN design, with fully exposed adsorptive surface and highly dispersed adsorptive sites, guards against the blocking of future sulfur infiltration and Li+ diffusion. The advantages of the TiN loaded N-doped carbon are finally confirmed by electrochemical evaluations. The capacity is found up to be 1338 mAh/g at a current density of 0.2 C and 690 mAh/g at a current density of 5 C (where 1 C = 1672 mAh/g). For durability evaluations, the capacity is maintained at 700 mAh/g after 800 cycles with a mere decay of 0.04% per cycle. Lastly, the feasibility of a high mass loading with 7 mg/cm2 is demonstrated.