Preparation of coal based graphite nanoplatelets based on mechanochemistry andthe characterization of their electrochemical energy storage performance

The clean and efficient conversion of coal is an important part of the national energy development strategy of “carbon emission peak and carbon neutrality”,and the materialization of coal is an effective way to realize its low carbon,high value and clean utilization.In this paper,the coal based graphite nanoplatelets (CGNs) were prepared from the pre synthesized coal based graphite with the help of mechanochemistry generated by high energy mechanical ball milling.The effect of ball milling time on the microstructure of CGNs was investigated,and the electrochemical energy storage properties of CGNs as anode in lithium ion batteries (LIBs) were studied to explore the feasibility of using mechanochemical action to prepare CGNs anode materials.The results show that the CGNs with rich defective structures such as nanopores and oxygen containing functional groups can be exfoliated from coal based graphite by mechanochemical action,and the microstructure of graphite nanoplatelets can be effectively regulated by controlling ball milling time.When the ball milling time is 50 h,the CGNs exhibits a three dimensional network structure formed by stacking and cross linking of graphite microcrystal layers,and contains abundant nanopores with a pore size distribution of 1.5-20.0 nm and a small amount of oxygen containing functional groups,and its layer spacing and specific surface area are 0.345 5 nm and 573 m2/g,respectively.The CGNs as anode in LIBs show some good electrochemical energy storage properties.The CGNs electrode delivers a high reversible capacity of 726 mAh/g,good rate performance and cycling stability,in which the CGNs electrode exhibits a reversible capacity of 252 mAh/g at a high current density of 2.0 A/g and a capacity retention rate of 88.1% after 200 cycles.The lithium ion storage of the CGNs anode is controlled by both diffusive intercalation capacitance and surface adsorption capacitance,and the introduction of defective structures such as nanopores and oxygen containing functional groups is beneficial to improve the contribution of surface adsorption capacitance to the energy storage capacity of the CGNs anode.This study provides some new ideas for the development of high performance graphite nanoplatelets anode,the materialization and high value added utilization of coal.