ZnFe2O4-Ni5P4 Mott-Schottky Heterojunctions to Promote Kinetics for Advanced Li-S Batteries.

Abstract

The practical progress of lithium-sulfur batteries is hindered by the serious shuttle effect and the slow oxidation-reduction kinetics of polysulfides. Herein, the ZnFe2O4-Ni5P4 Mott-Schottky heterojunction material is prepared to address these issues. Benefitting from a self-generated built-in electric field, ZnFe2O4-Ni5P4 as an efficient bidirectional catalysis regulates the charge distribution at the interface and accelerates electron transfer. Meanwhile, the synergy of the strong adsorption capacity derived from metal oxides and the outstanding catalytic performance that comes from metal phosphides strengthens the adsorption of polysulfides, reduces the energy barrier during the reaction, accelerates the conversion between sulfur species, and further accelerates the reaction kinetics. Hence, the cell with ZnFe2O4-Ni5P4/S harvests a high discharge capacity of 1132.4 mAh g-1 at 0.5C and displays a high Coulombic efficiency of 99.3% after 700 cycles. The ZnFe2O4-Ni5P4/S battery still maintains a capacity of 610.1 mAh g-1 with 84.4% capacity retention after 150 cycles at 0.1C under a high sulfur loading of 3.2 mg cm-2. This work provides a favorable reference and advanced guidance for developing Mott-Schottky heterojunctions in lithium-sulfur batteries.