Recent attention has been focused on the synthesis and application of complex heter ostructured nanomaterials, which can have superior electrochemical performance than singlestructured materials. Here we synthesize the threedimensional (3D) multicomponent oxide, mnmoo 4 /Comoo 4 . Hierarchical heterostructures are successfully prepared on the backbone material mnmoo 4 by a simple refluxing method under mild conditions; and surface modification is achieved. We fabricate asymmetric supercapacitors based on hierarchical mnmoo 4 /Comoo 4 heterostructured nanowires, which show a specific capacitance of 187.1 F g − 1 at a current density of 1 A g − 1 , and good reversibility with a cycling efficiency of 98% after 1,000 cycles. These results further demonstrate that constructing 3D hierarchical heterostructures can improve electrochemical properties. 'oriented attachment' and 'selfassembly' crystal growth mechanisms are proposed to explain the formation of the heterostructures.

Ultralong hierarchical vanadium oxide nanowires with diameter of 100-200 nm and length up to several millimeters were synthesized using the low-cost starting materials by electrospinning combined with annealing. The hierarchical nanowires were constructed from attached vanadium oxide nanorods of diameter around 50 nm and length of 100 nm. The initial and 50th discharge capacities of the ultralong hierarchical vanadium oxide nanowire cathodes are up to 390 and 201 mAh/g when the lithium ion battery cycled between 1.75 and 4.0 V. When the battery was cycled between 2.0 and 4.0 V, the initial and 50th discharge capacities of the nanowire cathodes are 275 and 187 mAh/g. Compared with self-aggregated short nanorods synthesized by hydrothermal method, the ultralong hierarchical vanadium oxide nanowires exhibit much higher capacity. This is due to the fact that self-aggregation of the unique nanorod-in-nanowire structures have been greatly reduced because of the attachment of nanorods in the ultralong nanowires, which can keep the effective contact areas of active materials, conductive additives, and electrolyte large and fully realize the advantage of nanomaterial-based cathodes. This demonstrates that ultralong hierarchical vanadium oxide nanowire is one of the most favorable nanostructures as cathodes for improving cycling performance of lithium ion batteries.

Inspired by the cucumber-like structure, by combining the in situ chemical oxidative polymerization with facile soaking process, we designed the heterostructured nanomaterial with PEDOT as the shell and MnO(2) nanoparticles as the protuberance and synthesized the novel cucumber-like MnO(2) nanoparticles enriched vanadium pentoxide/poly(3,4-ethylenedioxythiophene) (PEDOT) coaxial nanowires. This heterostructured nanomaterial exhibits enhanced electrochemical cycling performance with the decreases of capacity fading during 200 cycles from 0.557 to 0.173% over V(2)O(5) nanowires at the current density of 100 mA/g. This method is proven to be an effective technique for improving the electrochemical cycling performance and stability of nanowire electrodes especially at low rate for application in rechargeable lithium batteries.

No abstract

Layered intercalation compounds NaxMnO2 (x = 0.7 and 0.91) nanoflakes have been prepared directly through wet electrochemical process with Na+ ions intercalated into MnO2 interlayers spontaneously. The as-prepared NaxMnO2 nanoflake based supercapacitors exhibit faster ionic diffusion with enhanced redox peaks, tenfold-higher energy densities up to 110 Wh·kg−1 and higher capacitances over 1000 F·g−1 in aqueous sodium system compared with traditional MnO2 supercapacitors. Due to the free-standing electrode structure and suitable crystal structure, NaxMnO2 nanoflake electrodes also maintain outstanding electrochemical stability with capacitance retention up to 99.9% after 1000 cycles. Besides, pre-intercalation effect is further studied to explain this enhanced electrochemical performance. This study indicates that the suitable pre-intercalation is effective to improve the diffusion of electrolyte cations and other electrochemical performance for layered oxides, and suggests that the as-obtained nanoflakes are promising materials to achieve the hybridization of both high energy and power density for advanced supercapacitors.

We designed and successfully synthesized the silver vanadium oxides/polyaniline (SVO/PANI) triaxial nanowires by combining in situ chemical oxidative polymerization and interfacial redox reaction based on β-AgVO(3) nanowires. The β-AgVO(3) core and two distinct layers can be clearly observed in single triaxial nanowire. Fourier transformed infrared spectroscopic and energy dispersive X-ray spectroscopic investigations indicate that the outermost layer is PANI and the middle layer is Ag(x)VO((2.5+0.5x)) (x < 1), which may result from the redox reaction of Ag(+) and aniline monomers at the interface. The presence of the Ag particle in a transmission electron microscopy image confirms the occurrence of the redox reaction. The triaxial nanowires exhibit enhanced electrochemical performance. This method is shown to be an effective and facile technique for improving the electrochemical performance and stability of nanowire electrodes for applications in Li ion batteries.

No abstract

No abstract