Structure Control And Electrochemical Properties Of Sheet-like Porous Carbons

With the superiority of excellent conductivity, mechanical property, structural stability and diverse structure, carbon materials play vital roles in advanced energy storage and conversion devices by constructing energy storage and transport network. Controllable preparation of sheet-like porous carbons is an important way to increase the active sites and build more efficient and convenient charge transfer channel and key measure to further improve the power density and energy density of devices. Aiming to the problems of current electrode materials of lithium ion battery and supercapacitor, after understanding what roles carbons play, a series of sheet-like porous carbon-based materials with ion transport channel and conductive network were obtained by careful design and controllable preparation, and then were successfully applied in the advanced energy storage devices. On the basis of development of the preparation method of sheet-like porous carbons, we also analyzed their formation mechanism, which is helpful to realize the precise control of the microstructure.Considering the poor conductivity and volume effect of tin with high specific capacity, Sn@C/graphene hybrid was prepared. The electrochemical performance was optimized due to the synergistic effect between the components of the implementation. The first reversible charge capacity was as high as 922.7 mAh g-1 with a high capacity retention of 71.5 % after 50 cycles.The preparation methods of biomass-based sheet-like porous carbons were developed. Sheet-like porous carbons with controllable microstructure were obtained by direct carbonization of biomass under different temperatures. In 6 M KOH solution, BCY-800 shows a high capacitance of 216 F g-1, and keeps capacitance retention of 84 % when current density increases 40 times. In addition, the novel carbon possesses outstanding volumetric energy density and volumetric power density in ionic liquid system. The capacitance of BCY-900 was 64.6 Wh L-1 at a power density of 290 W L-1, and still as high as 34 Wh L-1 at a power density of 3065 W L-1.Transforming polymerized glucose spheres into oriented and interlinked sheet-like porous carbon was accomplished by changing the activation route, and the formation mechanism was also proposed. The advanced characteristics of high specific surface area(2633 m2 g-1) and hierarchical porous structure resulted in the excellent electrochemical performance. The specific capacitance was 247 and 184 F g-1 under the current density of 0.5 and 100 A g-1, respectively. And the capacitance retention was 98 % after 2000 cycles.The role and mechanism of graphene oxide as template for the formation of sheet-like carbonaceous materials was discussed by studying the effect of graphene oxide on the structure and morphology of hydrothermal product of biomass. Sheet-like porous carbon with 3257 m2 g-1 was obtained by KOH activation. And surprisingly, its cyclic voltammetry maintained nearly rectangular even at a high scan rate of 1000 mV s-1.