Cu2+ regulates high-performance Fe2O3 nanospheres (Fe1−xCuxO1.5-δ (x = 0.33, 0.4, 0.5)) sulfur loaded matrix to improve the electrochemical performance of lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are considered as promising energy storage systems owing to rather high theoretical specific capacity (1675 mAh.g−1) and low cost. Nevertheless, the practical prospect is always limited owing to some short-comings, such as sulfur insulation, volume alternation and shuttle effect. To solve these problems, Cu2+ regulated Fe2O3 nanospheres (Fe1−xCuxO1.5-δ) as high-performance matrixes for sulfur composite cathodes of lithium-sulfur batteries are constructed via a facile hydrothermal method. It indicates that Cu2+ regulation can increase the lattice size and exhibit uniform nanospheres micromorphology with less serious agglomeration. Moreover, as sulfur loading material can realize the joint effect on the physical and chemical confinement and some dissociate excess Cu2+ with sulfur also can directly compose some Cu-S structures, further stabilizing the structure of sulfur composite cathode. In addition, Fe0.6Cu0.4O1.5-δ/S composite cathode with sulfur loading mass ratio to 1:3 has fast electrochemical reaction kinetics with the low charge transfer resistance (25.54 Ω) and the high lithium-ion transfer efficiency (DLi+=2.59 ×10−12 cm2·s−1) and the initial specific discharge capacities and ideal capacity retention accompanied by a charge and discharge voltage platform with small fluctuation.