Multidimensional Hybrid Architecture Encapsulating Cobalt Oxide Nanoparticles into Carbon Nanotube Branched Nitrogen-Doped Reduced Graphene Oxide Networks for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are regarded as promising candidates for the next-generation energy storage devices owing to their high-theoretical capacity (1675 mAh g⁻¹) and affordable cost. However, several limitations of LSBs such as the lithium polysulfide shuttle, large volume expansion, and low electrical conductivity of sulfur need to be resolved for practical applications. To address these limitations, herein, a multidimensional architectured hybrid (Co@CNT/nG), where Co₃O₄ nanoparticles are encapsulated into three-dimensional (3D) porous N-doped reduced graphene oxide interconnected with carbon nanotube (CNT) branches, is synthesized through a simple pyrolysis method. The synergistic effect achieved through the homogeneously distributed and encapsulated Co₃O₄ nanoparticles, the interconnected CNT branches, and the 3D hierarchical porous structure and N-doping of Co@CNT/nG significantly suppresses the shuttle effect of lithium polysulfides and enhances the conversion redox kinetics for the improved sulfur utilization. We validate this effect through various measurements including symmetric cells, Li₂S nucleation, shuttle currents, Tafel slopes, diffusion coefficients, and post-mortem analyses. Importantly, Co@CNT/nG-70S-based LSB cells achieve a high-specific capacity of 1193.1 mAh g⁻¹ at 0.1 C and a low capacity decay rate of 0.030% per cycle for 700 cycles at 5 C, delivering a high areal capacity of 5.62 mAh cm⁻² even with a loading of 6.5 mg cm⁻².