Efficient sulfur host based on Sn doping to construct Fe2O3 nanospheres with high active interface structure for lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are hampered by the shuttle effect and sluggish conversion kinetics of polysulfide, and give rise to serious capacity decay and poor rate performance, which is an important reason for limiting to commercialization applications. Herein, Sn-doped Fe2O3 nanospheres with high active interface structure adhere to adequate and high-efficiency catalytic sites have been designed by a facile hydrothermal reaction. Theoretical calculations of density of states (DOS), visualized detection, symmetric cyclic voltammetry and Li2S nucleation experiment can elucidate adsorption effect and the mechanism of promoting polysulfide conversion. When Sn@Fe2O3 with Sn doping molar ratio to 1:3, it can advance growth of Li2Sn (93.47 mAh·g−1), reduce the reaction energy barrier, and enhance the conversion of polysulfides. Thus, as a sulfur composite cathode active material, it shows low electrochemical charge transfer resistance (56.14 Ω) and great lithium-ion diffusion coefficient (DLi+ = 1.4 × 10−11 cm2·s−1). Meanwhile, it has a great initial discharge capacity of 1057 mAh·g−1 at 0.5 C along with 85 % discharge capacity retention at 1 C after 130 cycles. Encouragingly, even with a sulfur loading up to 1.2 mg cm−2, the sulfur composite cathode still can harvest high lithium-ion transfer efficiency and cyclic stability.