Cobalt-embedded carbon nanotube-bridged hollow carbon cubes enabling electro n/ion co-transport and catalytic conversion in lithium-sulfur batteries

Abstract

Lithium‑sulfur (Li−S) batteries have attracted tremendous attention as next-generation energy storage systems due to their exceptional theoretical energy density (2600 Wh kg⁻¹). Despite their great promise, the large-scale application of Li−S batteries is still hindered by critical challenges, particularly the lithium polysulfide shuttle phenomenon and sluggish kinetics during sulfur-based redox reactions. This research introduces an innovative cathode architecture that consists of hollow carbon cubes integrated with carbon nanotubes and cobalt nanoparticles (HCCs-Co-CNTs), aiming to mitigate the previously discussed issues. The HCCs-Co-CNTs possess structure featuring cobalt-embedded carbon nanotubes to bridge hollow carbon cubes, forming a multi-scale and interconnected structure. The design enables synergistic enhancement of Li−S battery performances through several mechanisms: The hollow carbon cubes provide a continuous conductive framework for efficient electron transport; The interconnected carbon structure improves electrical conductivity across the cathode; Carbon nanotubes (CNTs) directly grown on the surfaces of the cubes establish continuous conductive networks, resulting in a three-dimensional ion transport network to facilitate lithium-ion diffusion. Meanwhile, cobalt nanoparticles embedded within the nanotubes act as catalytic centers, improving the chemical interaction with polysulfides and facilitating their catalytic transformation, enabling coordinated regulation of electrons, ions, and reactants. This synergistic design enables the HCCs-Co-CNTs/S cathode to deliver an initial discharge capacity of 1216 mAh g⁻¹ at 0.2C with 83 % capacity retention after 200 cycles. Even at a high rate of 4C, it maintains a capacity of 734 mAh g⁻¹, demonstrating excellent rate capability and cycling stability. This study provides an effective approach to mitigate the LiPSs shuttle effect and contributes to the rational development of sulfur host architectures.