Hierarchically assembled mesoporous carbon nanosheets with an ultra large pore volume for high-performance lithium–sulfur batteries. (19th December 2018) - Zhang, Jun
Abstract : Hierarchically assembled carbon nanosheets with a high surface area and an ultra large pore volume were derived by the direct carbonization of an adipic acid and zinc powder mixture. This structure enables fast ion and electron kinetics, resulting in an enhanced electrochemical performance of 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 m 2 g −1 ) and an ultra large pore volume (4.09 cm 3 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.