Natural chalcopyrite as a sulfur source and its electrochemical performance for lithium–sulfur batteries

Abstract

The production of polysulfides during discharging and their solubility in electrolytes are issues encountered in lithium–sulfur batteries. In this study, a novel chalcopyrite material with fixed sulfur was developed based on its chemical affinity for lithium–sulfur batteries. Pure micro-sized chalcopyrite (CuFeS₂) was prepared from its natural ore by simple flotation. Sulfur in the prepared chalcopyrite can be fixed in the electrode during charging–discharging because copper and iron are sulfur-friendly elements in nature. The fixing of sulfur leads to a high initial charge capacity (1300 mA h g⁻¹ at the initial discharge current density of 100 mA g⁻¹), excellent rate performance, and good cycling properties. The discharge capacities are approximately 1200, 1050, 970, 930, and 875 mA h g⁻¹ at current densities of 100, 200, 300, 500, and 1000 mA g⁻¹, respectively. When the current density is reduced to 100 mA g⁻¹, the reversible capacity can recover to 1000 mA h g⁻¹, and the cyclability becomes impressive (initial capacity of 1130 mA h g⁻¹, and 767 mA h g⁻¹ is maintained for 100 cycles at a high current density of 1000 mA g⁻¹). Given the abundance of chalcopyrite in nature and the simplicity and low cost of flotation extraction, chalcopyrite exhibits potential to be applied to lithium–sulfur batteries.