Cobalt nitride nanocrystals coated separator as multifunctional interlayer for improving polysulfides regulation

Abstract

Using transition metal oxides to inhibit the shuttle effect of soluble polysulfides is one of the effective ways to improve the cycling capacity of Li–S batteries. However, due to their unsatisfactory electrical conductivity, the redox reactions of polysulfides adsorbed on transition metal oxide surface cannot occur in time and completely, thus increasing the electrode polarization. Herein, highly conductive Co4N nanocrystals were prepared and successfully used for separator modification of sulfur cathode. As an efficient intermediate layer, Co4N-Celgard not only effectively inhibited the diffusion and shuttle of polysulfides, but also promoted the corresponding conversion reactions due to its high catalytic activity and electrical conductivity, avoiding the ineffective accumulation of lithium polysulfides. Meanwhile, Co4N nanocrystals had good electrolyte affinity, which could effectively improve electrode dynamics. Based on the above advantages, Li–S cell with Co4N-Celgard separator exhibited high rate performance of 626 mA h g−1 at 4 C and low decay rate of 0.089 % per cycle.