Ice template-induced assembly coupled with carbonization strategy for preparation of sulfur-doped porous carbon nanosheets from lignite as high-capacity anode for lithium-ion batteries

Abstract

Two-dimensional (2D) porous carbon nanosheets with heteroatom doping are promising anode materials for lithium-ion batteries (LIBs) due to their distinctive sheet-like structure and excellent electrical conductivity. Limited by high preparation costs and cumbersome preparation processes, the large-scale production of carbon nanosheets remains a major challenge. Herein, a series of sulfur-doped porous carbon nanosheets (SCNSs) are successfully synthesized through ice template-induced assembly coupled with a carbonization approach using aromatic ring fragments exfoliating from lignite as the precursor and K2SO4 as the sulfur source. The prepared SCNSs exhibit well-defined sheet-like structures, abundant hierarchical nanopores, large specific surface areas (∼1761 m2·g−1), and high sulfur doping contents (∼7.72 at%). Such unique microstructure characteristics of SCNSs not only provide favorable and efficient channels for the lithium-ions/electrons transportation but also offer sufficient available space or active sites for lithium-ions storage. When used as anode materials for LIBs, the SCNS-3 shows high reversible capacity (1620 mAh·g−1 at 0.05 A·g−1), excellent rate performance (315 mAh·g−1 at 2 A·g−1), and superior cycling stability (901 mAh·g−1 at 1 A·g−1 after 500 cycles). Lithium storage behavior analysis indicated that the capacitance enhancement in SCNSs anodes is primarily due to improved capacitive behavior. This study provides a novel and effective route for the large-scale production of sulfur-doped carbon nanosheets using aromatic ring fragments exfoliated from lignite, which demonstrates promising industrial application potential in LIBs anode materials.