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.

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Na3V2(PO4)3 nanograins dispersed in different carbon matrices are rationally synthesized and systematically characterized. The acetylene carbon matrix provides the best conductive networks for electrons and sodium ions, which endows Na3V2(PO4)3 stable cyclability and high rate performance. The Na3V2 (PO4)3 -based symmetric sodium-ion batteries show outstanding electrochemical performance, which is promising for large-scale and low-cost energy storage applications.