Construction of a fast Li-ion path in a MOF-derived Fe3O4@NC sulfur host enables high-rate lithium-sulfur batteries.

Abstract

Besides the adjustment of the active centres, the precisely designed microstructures of the carbon hosts also play a significant role in improving the battery performance. Herein, MOF-derived Fe3O4@NCs were prepared through a molten salt-assisted calcination method at different carbonization temperatures. Compared with the materials obtained at 700 °C, LK450 calcined at a lower temperature of 450 °C maintains suitable pore sizes and more N-doping and exhibits excellent Li-ion transport performance. Thus, the S/LK450 cathode can achieve an outstanding rate performance of up to 5 C (∼528 mA h g-1) and an extremely low capacity decay of 0.037% per cycle after 500 cycles at 1C. Notably, even with a high sulfur loading (4.0 mg cm-2), the S/LK450 cathode can still deliver a high capacity of 673 mA h g-1 at 0.2C after 100 cycles. Briefly, this work demonstrates the superiorities to prepare the samples at relatively low carbonization temperatures, which guarantee a better ion path structure and sufficient N-doping in the carbon skeleton.