uqing Li

Fabrication of Fe3O4 Dots Embedded in 3D Honeycomb‐Like Carbon Based on Metallo–Organic Molecule with Superior Lithium Storage Performance

A novel metallo-organic molecule, ferrocene, is selected as building block to construct Fe3 O4 dots embedded in 3D honeycomb-like carbon (Fe3 O4 dots/3DHC) by using SiO2 nanospheres as template. Unlike previously used inorganic Fe3 O4 sources, ferrocene simultaneously contains organic cyclopentadienyl groups and inorganic Fe atoms, which can be converted to carbon and Fe3 O4 , respectively. Atomic-scale Fe distribution in started building block leads to the formation of ultrasmall Fe3 O4 dots (≈3 nm). In addition, by well controlling the feed amount of ferrocene, Fe3 O4 dots/3DHC with well-defined honeycomb-like meso/macropore structure and ultrathin carbon wall can be obtained. Owing to unique structural features, Fe3 O4 dots/3DHC presents impressive lithium storage performance. The initial discharge and reversible capacities can reach 2047 and 1280 mAh g-1 at 0.05 A g-1 . With increasing the current density to 1 and 3 A g-1 , remarkable capacities of 963 and 731 mAh g-1 remain. Moreover, Fe3 O4 dots/3DHC also has superior cycling stability, after a long-term charge/discharge for 200 times, a high capacity of 1082 mAh g-1 can be maintained (80% against the capacity of the 2nd cycle).

Construction of Hierarchically One-Dimensional Core–Shell CNT@Microporous Carbon by Covalent Bond-Induced Surface-Confined Cross-Linking for High-Performance Supercapacitor

A covalent bond-induced surface-confined cross-linking is reported to construct one-dimensional coaxial CNT@microporous carbon composite (CNT@micro-C). Octaphenyl polyhedral oligomeric silsesquioxane (Ph-POSS) composed of eight phenyls and a -Si8O12 cage was selected as precursor for microporous carbon. The layer-by-layer cross-linking of phenyl anchored Ph-POSS on the surface of CNT; after carbonization and etching of -Si8O12 cages, CNT@micro-C including CNT core and microporous carbon shell was harvested. The thickness of microporous carbon shell can be well tailored from 6.0 to 20.0 nm, and the surface area of CNT@micro-C can reach 1306 m2 g-1. CNT@micro-C combines the structural advantages of CNT and microporous carbon, presenting large surface area, high electrical conductivity, fast ion transfer speed, and short ion transfer distance. When used as electrode material, CNT@micro-C reveals superior supercapacitive performance; for example, its capacitance can reach 243 F g-1 at 0.5 A g-1 and slightly decreases to 209 F g-1 at 10 A g-1, indicating a capacitance retention of 86%. Even at a very high scan rate of 50 A g-1, a high capacitance of 177 F g-1 is retained, giving a capacitance retention of 73%.

Rapid preparation of SnO2/C nanospheres by using organotin as building blocks and their application in lithium-ion batteries

Constructing an electrode integrating ultralow SnO2 size, stable carbon barriers and well-developed pore structure are effective to address the issues of crack and pulverization for SnO2-based electrode during lithiation/delithiation process. But until now, it is still a challenge to exploit simple and robust method to fabricate ultrasmall SnO2 particles embedded in a carbon matrix. Herein, we develop a rapid strategy to prepare SnO2/C nanospheres using a simple Friedel–Crafts crosslinking of triphenyltin chloride for only 15 min and subsequent carbonization. The SnO2/C nanospheres (∼500 nm) have ultrasmall SnO2 particles of 4 nm, which were dispersed in carbon continuous phase. Moreover, the pyrolysis of the polymer during carbonization creates considerable micropores inside the carbon phase and leads to a surface area of 463.3 m2 g−1. When used as electrode materials in a lithium-ion battery, the ultrasmall SnO2 particles can prevent the cracking of the electrode, the carbon continuous phase can act as a buffer to protect SnO2 particles from aggregation, and micropores will supply expansive space for volume change. Thus, the SnO2/C nanosphere exhibits superior electrochemical performance, e.g., the first discharge and charge capacities can reach 1453 and 719 mA h g−1 respectively, and 120 cycles later, its capacity remains 629 mA h g−1, indicating a capacity retention of 87.4% (C120th/C2nd).