Hierarchically assembled mesoporous carbon nanosheets with an ultra large pore volume for high-performance lithium–sulfur batteries

Abstract

Porous carbon materials are considered as a promising sulfur host for lithium–sulfur (Li–S) batteries. However, many porous carbon materials are prepared by complicated preparation processes, facing challenges including low yields, toxic chemicals, and high-energy consumption. In this work, a simple method is reported for the preparation of mesoporous carbon with a high surface area (2166 m² g⁻¹) and an ultra large pore volume (4.09 cm³ g⁻¹) by the direct carbonization of an adipic acid and zinc powder mixture without further chemical/physical activation process. The mesoporous carbon is composed of nanosheets with abundant capsule-like nanopores of around 15 nm, exhibiting a hierarchically assembled flower-like structure. The porous carbon nanosheets (PCNSs) with a hierarchical structure are used as the host for sulfur to form a homogeneous composite (S/PCNS) through a conventional heat infiltration process. Excellent electrochemical performance is achieved with S/PCNS as the cathode of a Li–S battery. The S/PCNS composite with 62 wt% sulfur exhibits an initial discharge capacity of 1384 mA h g⁻¹ and retains a reversible capacity of 657 mA h g⁻¹ after 100 cycles at 0.2C rate. Remarkably, the S/PCNS composite exhibits a decay rate of only 0.046% per cycle within 500 cycles at 1C rate. The high surface area, large pore volume, and sheet-like two-dimensional (2D) structure of the micro/mesoporous carbon matrix render the sulfur-based cathode with superior electrochemical kinetics, rate capability, and long-life performance.