Sulfur- layered porous carbon nanostructured matrix - Co3O4 composites: An enhancement of cycling performance in sodium-sulfur battery

Abstract

Background

For future applications in electric vehicles, power tools, portable devices, and other areas, developing effective cathode materials for sodium-sulfur batteries is crucial. Sulfur is a promising low-cost cathode material due to its high energy density, environmental friendliness, and natural abundance. Sodium-sulfur batteries, with a theoretical capacity of 1672 mAh g^-1, offer a higher capacity compared to conventional sodium-ion batteries. However, their use has been limited by the dissolution of intermediate polysulfides, which can impact performance.

Methods

In this study, sulfur was blended with various carbon matrices, including hard carbon (HC), reduced graphene oxide (rGO), and multi-walled carbon nanotubes (MWCNTs), along with Co₃O₄, through a solid-state reaction and melt diffusion process to prepare sulfur/ Co₃O₄/carbon template composites. These composites were then used as cathodes in sodium-sulfur (Na-S) batteries. The physical and electrochemical characteristics of the prepared composites were investigated using various characterization techniques. Raman analysis was employed to confirm the presence of carbon, while X-ray diffraction (XRD) patterns indicated that sulfur is in an orthorhombic structure.

Significant findings

The sulfur/ Co₃O₄/carbon template composite with 60% sulfur (SCR composite) demonstrated significantly enhanced cycling performance, achieving 925 mAh g^-1 at 0.2 C for the initial cycle. The incorporation of Co₃O₄ effectively suppressed the polysulfide shuttle effect, thereby sustaining the electrode's capacity. Additionally, the carbon matrix played a crucial role in confining the sulfur within its pores, which helped to limit the loss of active material.