A high-performance sodium anode composed of few-layer MoSe2 and N, P doped reduced graphene oxide composites

Abstract

The renewable energy revolution and its practical applications demand the need for large solar storage options. Lithium-ion batteries may remain top in terms of their utilization and performance, however their cost-per-kWh impacts their usage, and researchers prefer to stick to sodium-ion chemistry as a large storage option. One of the main research topics for rechargeable sodium-ion batteries is in proposing new anodes, since the commercial graphite anode is incompatible for use in SIBs as its larger radius (0.98 Å vs. 0.69 Å of Li⁺) leads to sluggish Na-ion transport during the cycling process. Our team is continuously working on the development of chalcogenide-based anodes for use in sodium-ion batteries and their reaction mechanisms. In this work, we prepared MoSe₂ and MoSe₂-N, P-doped rGO composites (with the latter denoted as MoSe₂/NPr) as active anodes for use in sodium-ion batteries. The morphology and electrochemical properties of MoSe₂/NPr were characterised and compared with those of the bare MoSe₂ electrode. The MoSe₂/NPr composite delivers a capacity of 337 mA h g⁻¹ at 0.1 A g⁻¹ after 100 cycles and 244.4 mA h g⁻¹ at 1 A g⁻¹; these values are higher than those of MoSe₂/rGO (225.6 mA h g⁻¹ at 0.1 A g⁻¹) and MoSe₂ electrodes (206 mA h g⁻¹ at 0.1 A g⁻¹). The excellent performance of MoSe₂/NPr is attributed to the interconnected doped rGO sheets that provide sufficient active sites for MoSe₂ with improved conductivity and reduced volume expansion during the cycling process. In addition, the sodium storage mechanism is investigated by several ex situ physical and microscopic studies.