Graphene/CNT Foam as a High-Loading Sulfur Cathode for Lean-Electrolyte Lithium–Sulfur Cells

Abstract

Lithium–sulfur electrochemical batteries are promising next-generation energy-storage systems because of their high-capacity sulfur cathode, cost-effectiveness, and natural abundance. For practical applications, achieving high electrochemical utilization and stability of high-loading sulfur cathodes in lean-electrolyte cells is essential but remains challenging due to intrinsic material limitations and extrinsic cell-fabrication constraints. This study introduces a graphene/carbon nanotube (CNT) foam as a high-loading sulfur cathode for lean-electrolyte lithium–sulfur cells. The cathode architecture is designed to address intrinsic material challenges by integrating a porous graphene framework with a tortuous CNT network, significantly enhancing electronic conductivity and mitigating polysulfide diffusion. The graphene skeleton provides a lightweight conductive substrate with large space for sulfur accumulation, while the CNT network effectively traps migrating polysulfides and facilitates electrolyte transport. As a result, in terms of cell-fabrication progresses, the graphene/CNT foam achieves a high sulfur loading of 10.8 mg cm^–2 and a sulfur content of 65 wt %, delivering an outstanding areal capacity of 8.6 mA·h cm^–2 and an energy density of 18 mW·h cm^–2. Moreover, the cathode demonstrates excellent cycling stability, retaining 80% capacity after 200 cycles, and superior rate performance across C/20–C/2 rates at a low electrolyte-to-sulfur ratio of 5.25 μL mg^–1. These findings indicate the graphene/CNT foam’s potential as a high-efficiency sulfur host, advancing the practical application of high-energy-density lithium–sulfur batteries.