Preparation And Electrochemical Properties Of Coal-based Graphene And Its Composites

In this paper,coal-based graphites were prepared from coals with different metamorphic degree as raw material via high temperature graphitization.Coal-based graphene derived from the as-prepared graphite was further used as anode material in lithium-ion batteries?LIBs?.Besides,a series of composites were synthesized using coal-based graphene as staring raw and modified by Co3O4,which were systematically investigated by SEM,TEM,XRD,FT-IR,Raman,XPS and various electrochemical techniques.The results show that with the increasement of coal metamorphism degree,coal-based graphite has a higher graphitization degree under the same condition,and coal-based graphene exhibits a larger sheet and a more complete structure,and its electrochemical performance is better.For the G-TX2800 sample,the graphitization degree was as high as 94.19%,and the corresponding graphene CRGO-TX2800 was observed with the best electrochemical performance,of which the first reversible specific capacity was 943 mAh·g^-1 at 0.1 C and the specific capacity was maintained651mAh·g^-1 after 100 cycles at 1 C.In addition,for coal-based graphene derived from Xishan bitumite,the specific capacity was no less than 608.5 mAh·g^-1 after 100 cycles at 1 C.Co₃O₄/CRGO composites were prepared by using CGO-TX2800 as precursor and cobalt nitrate as cobalt source and XPS result shows Co atoms have coordinated with oxide atoms inside the Co3O4/CRGO composites.Importantly,the electrochemical properties of the composite can be obviously improved after introduction of nitrogen elements.The Co₃O₄/CRGO-2 composite was observed with the optimal electrochemical properties:the first reversible specific capacity is 845.2 mAh·g^-1 under the current density of 100 mA·g^-11 and coulomb efficiency is 73%.