Design of spherical TiN/Nb4N5 heterostructure as bifunctional adsorption/catalytic material for lithium sulfur batteries

Lithium sulfur (Li-S) battery is the typical representative of the new generation secondary batteries, but its practical application is greatly hindered by the shuttle effect of lithium polysulfides (LiPSs) and sluggish electrochemical reaction kinetics. In this work, a spherical TiN/Nb 4 N 5 heterostructure is produced by nitridation of TiNb 2 O 7 microsphere and then used as an adsorption and catalytic material to fabricate modified polypropylene separator in Li-S batteries. Visual adsorption tests show that the TiN/Nb 4 N 5 heterostructure has better adsorption capacity of LiPSs than that of TiNb 2 O 7 microsphere precursor. The TiN/Nb 4 N 5 heterostructure also exhibits superior catalytic performance to accelerate the redox reaction kinetics of LiPSs conversion. The Li-S cell assembled with TiN/Nb 4 N 5 modified separator can deliver an initial discharge capacity of 917 mAh g -1 at 0.2 C, and a reversible capacity of 663.2 mAh g -1 after 200 cycles, higher than the cell assembled with TiNb 2 O 7 modified separator (555.4 mAh g -1 ) and pristine separator (385.1 mAh g -1 ). In short, this work provides a simple synthetic method to obtain a TiN/Nb 4 N 5 heterostructure with enhanced electrochemical performance of Li-S batteries. • TiN/Nb 4 N 5 heterostructure is synthesized by nitriding TiNb 2 O 7 microsphere; • TiN/Nb 4 N 5 heterostructure has strong adsorptive/catalytic conversion capability for polysulfides; • Li-S cell assembled with TiN/Nb 4 N 5 modified separator shows excellent electrochemical performance.