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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]

Inferior specific capacity and sluggish redox kinetics are the most stubborn problems lithium-ion and lithium-sulfur batteries (LIBs and LSBs) are facing, respectively. Here we report a facile fabrication of self-supported hollow Co 3 O 4 @carbon nanotubes on carbon cloth (H-Co 3 O 4 @CNT/CC) through a mild pyrolysis-oxidation process. The additive- and binder-free H-Co 3 O 4 @CNT/CC shows excellent electrochemical performances as both LIBs and LSBs electrodes. As a robust integrated anode for LIBs, the areal capacities are 2.72 mAh cm−2 at the current density of 0.5 C over 1000 cycles. While as a durable cathode host for LSBs, favorable areal capacities of 2.37 mAh cm−2 are maintained with a low capacity decay of 0.11 % per cycle at the sulfur loading of 6 mg cm−2 and current density of 1 C after 400 cycles. Electrochemical technology, ex situ Raman spectroscopy and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC via thermodynamics and kinetics. It is demonstrated that the hierarchically hollow interior structure, strong adsorb ability of Co 3 O 4 toward polysulfides and three-dimensional (3D) inter-connected conductive carbon framework are responsible for the high areal capacity, fast redox kinetics and cycling durability. [Display omitted] • The integrated electrode possesses the merits of hollow nanostructured Co 3 O 4 and 3D inter-connected conductive network. • Electrochemical technology and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC. • H-Co 3 O 4 @CNT/CC delivers high areal capacities of 2.72 mAh cm-2 after 1000 cycles at 0.5 C as anode. [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]