High-performance aqueous sodium-ion/sulfur battery using elemental sulfur

Abstract

Despite a promising outlook, the large-scale application of aqueous rechargeable sodium-ion batteries (ARSIBs) was impeded due to low-capacity electrode materials. Herein, we report a high capacity elemental sulfur-anode (S@NiVP/Pi-NCS) for aqueous rechargeable sodium ion/sulfur batteries using 70% of elemental sulfur, which delivers an outstanding capacity of 826 mA h g⁻¹ at 0.5C with an excellent cycling stability even at 10C and a negligible capacity decay with 0.03% sulfur loss per cycle even after 400 cycles. The NiVP/Pi-NCS host combines the merits of fast anchoring and high conductivity of the composite to achieve smooth anchoring-diffusion and conversion of sodium polysulfide. The superior anchoring and accelerated polysulfides redox kinetics were confirmed by various electrochemical studies and in situ spectro-electrochemical analysis. Chemical interaction with vanadium provides faster redox kinetics of polysulfide conversion and efficient anchoring as revealed by XPS and was further supported by XANES and EXAFS studies wherein the distortion at the V site and overlapping electronic states in the NiVP/Pi catalyst were observed. Further, a full cell battery assembled using S@NiVP/Pi-NCS anode and Na_0.44MnO₂ cathode demonstrates an excellent initial capacity of 756 mA h g⁻¹ based on S loading and 98.3 mA h g⁻¹ based upon total electrode weight with 95% of capacity retention even after 600 cycles and a remarkable energy density of 84 W h kg⁻¹ at 0.5C. Two full cells connected in series able to power LED demonstrate its practical application.