Ultrathin TiO2 surface layer coated TiN nanoparticles in freestanding film for high sulfur loading Li-S battery

A novel structure of ultrathin TiO2 surface layer coated TiN (TiO2@TiN) nanoparticle as polysulfide reservoir which can simultaneously boosts the static trapping and dynamic conversion of UPS is proposed. TiO2 @TiN nanoparticles are found to be uniformly distributed on three dimensional well connected nitrogen doped carbon nanofibers (CNFs) which provide extra chemical adsorption sites and continuous electron transfer pathways. With the synergistic effect of TiO2@TiN and CNFs, TiO2 @TiN/CNFs cathode shows exceptionally excellent rate capability by delivering 950 mAh g(-1) at current density of 5 mA cm(-2) with sulfur loading of 5 mg cm(-2). High sulfur utilization by maintaining 6.41 mAh cm(-2) after 200 cycles with sulfur loading of 8.0 mg cm(-2) is observed. The cycling stability is also confirmed by the discharge capacity of 800 mAh g(-1) after 400 cycles with sulfur loading of 4.0 mg cm(-2). Moreover, the in-situ conversion, adsorption-conversion and desorption-conversion mechanisms are proposed and confirmed by symmetric batteries and full batteries. This work highlights the superiority of surface chemistry and electrode structure in high sulfur loaded Li-S battery and provides new insights for developing high energy density Li-S battery.