Atomic-Level Alloying of Sulfur and Selenium for Advanced Lithium Batteries

Li-S batteries are potential candidates to be utilized in next-generation energy storage applications. Though they offer very high theoretical capacity, their poor volumetric energy density as compared to conventional Li-ion batteries and polysulphide dissolution in the electrolyte hinder it to be used in practical application. In this work, we have attempted to solve these issues by creating an alloy of sulfur and selenium by co-melting. The alloy, in the form of composite with reduced graphene oxide, was used further as a cathode in the Li-S/Se battery. The creation of an S-Se alloy improves the bonding between S and Li with the presence of Se due to dipolar interactions of S-Se and Li. This prevents polysulphide dissolution and gives a stable capacity of 800 mA h g^-1 for more than 100 cycles. The high density of the alloy resulted in high areal loading of electroactive material (6.5 mg/cm²).