Search

Transition metal oxides@carbon(C) nanocomposites with hierarchical three-dimensional (3D) core-shell nanoarchitectures, large surface area and high electrical conductivity as anode materials for lithium ion batteries (LIBs) are very desirable. Herein, we developed a simple and feasible route to fabricate novel hierarchical 3D ball-in-ball ZnO/ZnFe 2 O 4 @C nanospheres with well-defined hollow microstructures via one-step carbonization of Zn/Fe-metal organic frameworks for the first time. The as-prepared hierarchical 3D ball-in-ball ZnO/ZnFe 2 O 4 @C nanospheres were carefully characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, thermogravimetric analysis, N 2 adsorption/desorption isotherm, transmission electron microscopy and electrochemical techniques. The results showed ultrafine ZnO and ZnFe 2 O 4 nanocrystals were uniformly encapsulated by few carbon layers which was derived from in-situ carbonization of the organic ligands. Benefiting from their special hollow nanoarchitectures, ultrafine ZnO and ZnFe 2 O 4 nanocrystals encapsulated by a few carbon layers, large specific surface area and high electrical conductivity, the hierarchical 3D ball-in-ball ZnO/ZnFe 2 O 4 @C nanospheres presented high reversible capacities of 1283 and 1100 mA h g −1 after first 100 cycles and the following 100 cycles at current density of 100 and 200 mA g −1 , respectively. A high specific capacity of 155 mA h g −1 was obtained at relatively large current rates of 20 A g −1 . [ABSTRACT FROM AUTHOR]

In this work, we demonstrated an accessible and facile method to prepare hierarchically porous carbon (HPC)/Co 3 O 4 nanocomposites (HPCC). Biomaterials-derived HPC was used as the appropriate carrier to load Co 3 O 4 nanoparticles due to its hierarchically porous structure and high surface area of 163 m 2 g −1 . The HPCC nanocomposites were used as an anode material for lithium-ion batteries (LIBs) and showed good electrochemical performance, delivering an initial discharge of 1566 and charge capacity of 1314 mA h g −1 with a initial coulombic efficiency of 83.9%. Additionally, it could still maintain a high reversible capacity of 1215 mA h g −1 after 100 cycles at a specific current of 100 mA g −1 , which is much better than that of HPC, and Co 3 O 4 and some Co 3 O 4 -based nanocomposites. The good electrochemical performance was mainly attributed to the good distribution of small Co 3 O 4 on HPC, the high surface area and hierarchical pores of HPC to effectively load a number of small Co 3 O 4 , alleviate the severe volume expansion during cycling and improve the electrical conductivity of nanocomposites, and the synergistic effects from the HPC and Co 3 O 4 . Therefore, the HPCC nanocomposites were expected to be an advanced anode material for LIBs. [ABSTRACT FROM AUTHOR]

In the contemporary era, energy demands are ever-growing and a significant number of people are concerned about environmental pollution caused by the burning of fossil fuels. Therefore, it is a striking problem for the researchers to pursue renewable energy and sustainable energy to deal with the environmental and energy crisis. In this work, a novel hybrid hollow porous ZnO/C nanocages with high specific surface areas of 256 m 2 g −1 and high carbon content in weight of about 50% used as anode materials for lithium ion batteries (LIBs) were synthesized by a one-step pyrolysis of hollow metal organic framework material MOF-5 as both precursor and self-sacrificing template under N 2 atmosphere. The hollow porous ZnO/C nanocages released an initial discharge capacity of 1928 mA h g −1 at the current density of 100 mA g −1 and remained a high reversible capacity of 750 mA h g −1 after 100 cycles. According to the results of electrochemical measurements, the hollow porous ZnO/C nanocages also showed a good rate capability of 351 mA h g −1 at a relative large current density of 2 A g −1 . The excellent electrochemical performance was mainly due to the special nanostructures of the fabricated materials. Hence, the as-resulted hollow porous ZnO/C nanocages are promising anode materials for LIBs. [ABSTRACT FROM AUTHOR]

Hollow multicomponent transition metal oxide nanostructures have caused extensive attention due to their enhanced performances in lithium-ion batteries (LIBs). Herein, a hybrid of multicomponent 3NiO·2Ni 3/2 Co 1/2 ZnO 4 nanocomposite with porous hollow dodecahedron nanostructures (3NiO·2Ni 3/2 Co 1/2 ZnO 4 -HD) was fabricated by carbonization of NiCoZn-layered double hydroxides which were derived from multimetallic zeolitic imidazolate frameworks (Zn/Co-ZIFs) as both self-sacrificial template and precursors. The 3NiO·2Ni 3/2 Co 1/2 ZnO 4 -HD nanocomposites were carefully characterized by various techniques including scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, N 2 adsorption/desorption, transmission electron microscopy, Four-Point Probes and electrochemical techniques. When the 3NiO·2Ni 3/2 Co 1/2 ZnO 4 -HD nanocomposites were acted as anode materials for LIBs, a capacity of about 1337 mA h g −1 could be obtained after 100 cycles. The improved electrochemical performances might originate from synergistic effect of multicomponents, enhanced electrical conductivity and porous hollow dodecahedron nanostructures which could effectively alleviate volume deformation in the process of discharge/charge, accelerate mass transfer and increase the active sites for Li + storage. [ABSTRACT FROM AUTHOR]