Microstructural regulation of coal based carbon nanosheets and their electrochemical performance

The clean processing and high-efficiency utilization of coal is the core content of the national energy development strategy,and the materialization of coal is one of the important ways to realize its high value-added utilization.Herein,three-dimensional (3D) hierarchical porous coal-based carbon nanosheets (CCNSs) with controllable structure were prepared via a liquid oxidation-thermal reduction method using pre-synthesized graphite as the carbon source.The microstructure of CCNSs was characterized by scanning electron microscope (SEM),transmission electron microscope (TEM),nitrogen adsorption-desorption,X-ray diffraction (XRD),Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS),and their electrochemical performances applied as anode in lithium-ion batteries (LIBs) were further investigated via galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) tests.The results indicate that CCNSs with abundant 3D hierarchical porous and graphite microcrystalline structure can be successfully prepared by the liquid oxidation-thermal reduction method.The dosage of oxidant is an important factor affecting the microstructure of CCNSs,and the 3D hierarchical porous and graphite microcrystalline structure in CCNSs can be effectively regulated by adjusting the dosage of oxidant.When the mass ratio of oxidant to TXG is 4,the prepared CCNSs-3 exhibits a 3D hierarchical porous network structure formed by the cross-linking of graphene-like nanosheets and retains 38.9% graphite microcrystalline structure,while possesses a specific surface area of 285.6 m2/g and contains large amount of micro-meso-macroporous structure with an abroad pore size distribution of 1.5-100 nm and 5.47% oxygen doping.Due to the synergistic effect of 3D hierarchical porous structure and graphite microcrystalline structure,the CCNSs materials as anode in LIBs exhibit an excellent electrochemical performance.In particular,the optimal CCNSs electrode can deliver a high initial reversible capacity of 917 mA·h/g(higher than the 372 mA·h/g theoretical capacity of traditional graphite) at a current density of 50 mA/g,and possesses a high reversible rate capacity of 300 mA·h/g at a high current density of 2.0 A/g and the reversible capacity reaches 1 047 mA·h/g after 120 cycles,which demonstrates that the carbon material has a superior rate capability and cycling stability,suggesting that it can be a desirable anode material for LIBs.