Facet-Tailoring Five-Coordinated Ti Sites and Structure-Optimizing Electron Transfer in A Bifunctional Cathode with Titanium Nitride Nanowire Array to Boost the Performance of Li2S6-based Lithium-Sulfur Batteries

Lithium-sulfur (Li–S) batteries are a promising candidate for renewable next-generation energy storage technologies with low cost and high performance. However, their performances are limited by the “shuttle effect” of polysulfides. Herein, a bifunctional hierarchical structure of three-dimensional titanium nitride (TiN) nanowire array (NA) with exposed (200) facets is prepared as an efficient polysulfide-anchoring center. Benefitting from this chemical tailoring strategy, the TiN-NA-based electrode not only provides stable well-dispersed and highly ordered nanowires to accelerate the efficient transition of redox charge carriers and to further promote the redox kinetics of polysulfide conversion, but also suggests five-coordinated Ti sites on (200) facets to enhance the adsorption ability for polysulfides. With the advances of the newly developed materials, liquid Li2S6-based TiN NA electrodes (area: 2 ​cm2) offer large initial capacities of 1214 and 1150 mAh/g, and hold 856 and 520 mAh/g with 1.0 and 3.0 ​mg/cm2 sulfur loadings at 1.6 ​mA/cm2 after 500 cycles, respectively. Specifically, the Galvanostatic intermittent titration technique suggests a strong adsorption capacity of TiN-NA-based electrodes in artificial strong polysulfide diffusion conditions during discontinuous charging and discharging processes. This work offers a novel concept of tailoring uncoordinated Ti sites and optimizing electron transfer in polysulfide redox reactions to effectively tackle the “shuttle effect”.