Encapsulation of Se/C into ultra-thin Ni(OH)2 nanosheets as cathode materials for lithium-selenium batteries

Composites consisting of selenium/carbon (Se/C) encapsulated by ultra-thin Ni(OH)2 nanosheet shell are synthesized as cathode for high-performance lithium-selenium batteries. The Se/C-Ni(OH)2 cathode presents excellent discharge capacities and cyclic stability with almost 100% Coulombic efficiencies. It delivers a reversible capacity of 323 mAh g−1 after 300 cycles with almost negligible capacity degradation after 100 cycles at a high current density of 1 C. Several unique functional features of the composite electrodes are responsible for the findings. The uniform mixture of Se and carbon black in the composite promotes the utilization of the active materials with enhanced ion/electron transfer. The Ni(OH)2 nanosheets maintain the integrity of Se/C core during cycles, reducing the shuttling effect reactions of polyselenides. These results demonstrate that the Se/C-Ni(OH)2 composite cathode is a promising candidate for application in rechargeable lithium-selenium batteries.