Natural Silk Cocoon Derived Nitrogen-doped Porous Carbon Nanosheets for High Performance Lithium-Sulfur Batteries

Abstract There is an ever-increasing interest in utilization of natural biomass for rational design and fabrication of advanced carbon materials towards energy-related storage/conversion application. In this work, we successfully prepared an in-situ nitrogen-doped porous carbon nanosheet (NPCN) materials derived from renewable silk cocoon via a facile simultaneous activation and carbonization approach using metal salt FeCl3 and ZnCl2 as chemical activating agent. The as-prepared carbon materials were fully characterized to determine their morphology and structure features, and it was found that the obtained NPCN has a unique interconnected sheet-like morphology and a hierarchically porous structure with a relatively high specific surface area of 1540 m2 g−1 and a large pore volume of 1.85 cm3 g−1. Owing to the inherent nitrogen-containing functional groups existing in the silk cocoon, in-situ doping of nitrogen heteroatom can be realized by the carbonization treatment, which can efficiently boost the electrical conductivity of the porous carbon nanosheets. By employing the NPCP as a reservoir to impregnate sulfur for lithium-sulfur batteries, the resulting carbon/sulfur composite (NPCN/S) shows a remarkably improved rate performance and superior long-term cycling stability with an extremely low decay rate (0.1% per cycle) up to 300 cycles at a high rate of 2C (3350 mA g−1). What is more, a Coulombic efficiency of approximatively 100% is obtained. Taking into consideration various factors including sustainable development, low-cost carbon source, and facile mass production, this work shows a great scientific significance and promising prospect in scalable preparation of advanced carbon-based host matrix for the efficient immobilization of sulfur towards developing high performance lithium-sulfur batteries.