Multi-cavity carbon nanofiber film decorated with Co-Nx doped CNTs for lithium–sulfur batteries with high-areal-capacity

Abstract

The severe shuttle effect and sluggish redox kinetics are the main challenges in sulfur cathodes, leading to capacity degradation and poor rate performance of lithium–sulfur batteries, especially under high sulfur loading and low electrolyte/sulfur (E/S). Herein, a three-dimensional (3D) multi-cavity carbon nanofiber film decorated with Co-N_x doped carbon nanotubes (Co-NCNTs@CNF) has been designed and endowed with dual functions as the sulfur host and an interlayer simultaneously. The multi-cavity structure of Co-NCNTs@CNF provides enough space for high-loading sulfur and relieves the volume expansion of sulfur. In situ protruded CNTs and CNF form a conductive framework conducive to accelerating the electrons/ions transfer. The macroporous structure caused by the introduction of Co-containing hydrotalcite is beneficial for electrolyte penetration, thereby reducing the E/S. Co-N_x sites can act as high-efficiency adsorbents and catalysts to adsorb polysulfides and catalyze the conversion of polysulfides rapidly. Owing to the synergistic effect, the Co-NCNTs@CNF-0.42-S cathode with an interlayer delivers a high areal capacity of 4.77 mA h cm⁻² at 0.2C after 100 cycles under the sulfur loading of 6.7 mg cm⁻² and E/S = 10 µL mg⁻¹. This strategy provides a new insight for preparing sulfur cathode materials that can work at low E/S under high sulfur loading.