Synergistic Effect of Zn-Co Bimetallic Selenide Composites for Lithium-Sulfur Battery

Compared with monometallic selenides, heterogeneous bimetallic selenides have rich phase boundaries and superior electrical conductivity. ZnSe/CoSe2 composites were prepared by introducing Zn metal and using ZIF-8/67 as the precursor through the synergistic effect between Zn and Co after selenification. The electrocatalytic conversion of polysulfide is accelerated by ZnSe through chemical adsorption and the catalytic effect. The conductive CoSe2 surface provides a rapid diffusion path for lithium ions, accelerating the conversion of the polysulfide. On the basis of their individual strengths, ZnSe and CoSe2 can jointly promote the smooth adsorptive-diffuse-catalytic conversion process of polysulfide and induce the growth of lithium sulfide around its heterogeneous interface, thus enhancing the electrochemical performance of the lithium-sulfur battery cathode materials. The ZnSe/CoSe2-S electrode, at the optimal Zn-to-Co ratio of 1:1, has a 790.06 mAh g(-1) initial specific capacity at 0.2 C and excellent cycling stability at 1 C. After 300 cycles, the final capacity is 300.85 mAh g(-1), and the capacity retention rate reaches 82.71%.