A hierarchically porous TiN/N-C electrocatalyst with high interface utilization for lithium-sulfur batteries

Abstract

Lithium-Sulfur Batteries (LiSBs) are prevented to apply in practice by the irreversible loss from the cathode and difficult conversation kinetics of lithium polysulfides (LiPSs). An ideal S host material should possess high conductivity and sufficiently dispersed catalytic active sites to precisely restore the dissolved LiPSs to the surface of the S host material. In traditional catalyst design, porous carbonaceous materials are often selected as carriers for the nano-catalytic activity sites. However, non-polar pure carbon interfaces, where without nano-catalytic activity sites covered, have a very weak affinity to LiPSs. Here, we use ammonia as a nitrogen source to anneal the reduced aerogel (graphene oxide (rGO) supported nano-TiO2) at high temperatures. The N element is atomically doped into the lattice ofthe carbon matrix, and the nano-TiO2 is converted to nano-TiN. A hierarchically porous and high conductivity TiN/N-C is prepared, in which the nano-TiN is well dispersed on the surface of N-doped rGO as an active center for catalyzing LiPSs conversion. The doped-N elements significantly increase the proportion of the polar surface. The S@TiN/N-C composite cathode delivered an excellent long-life cycling performance, and the reversible discharge specific capacity faded from 1224 ± 16 to 675 ± 31 mAh g−1 after 930 cycles. More importantly, after 150 cycles with a high S loading, a reversible areal capacity of 4.1 mAh cm−2 can be achieved.