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Use of hybridized transition-metal oxides nanostructures with a shell coating show promise for improving the electrochemical performance of sodium-ion batteries. Herein, a novel type of designed sodium vanadate @ polypyrrole (Na 5 V 12 O 32 @PPy) nanocomposites with a synergetic core-shell structure was fabricated using sequential hydrothermal and electrodeposition methods. When the Na 5 V 12 O 32 @PPy nanocomposites were employed as a cathode, the assembled sodium-ion batteries exhibited a high reversible discharge capacity of 213 mAh g −1 at a current density of 30 mA g −1 , high rate performance (133 mAh g −1 at 480 mA g −1 ) and superior cycling performance (202 mAh g −1 at 100 mA g −1 after 100 cycles with a capacity retention of 94%). By contrast, the cycling behavior of this novel material proved to be much better than the naked Na 5 V 12 O 32 nanowires. This research provides a new pathway to explore cathode materials for sodium-ion battery with enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Precursors of ammonium vanadium bronze (NH 4 V 4 O 10 ) nanowires assembled on a conductive substrate were prepared by a hydrothermal method. After calcination at 360 °C, the NH 4 V 4 O 10 precursor transformed to vanadium pentoxide (V 2 O 5 ) nanowires, which presented a high initial capacity of 135.0 mA h g −1 at a current density of 50 mA g −1 in 5 M LiNO 3 aqueous solution; while the specific capacity faded quickly over 50 cycles. By coating the surface of V 2 O 5 nanowires with water-insoluble polypyrrole (PPy), the formed nanocomposite electrode exhibited a specific discharge capacity of 89.9 mA h g −1 at 50 mA g −1 (after 100 cycles). A V 2 O 5 @PPy //LiMn 2 O 4 rechargeable lithium battery exhibited an initial discharge capacity of 95.2 mA h g −1 ; and after 100 cycles, a specific discharge capacity of 81.5 mA h g −1 could retain at 100 mA g −1 . [ABSTRACT FROM AUTHOR]

BiVO 4 nanowire array is fabricated by a hydrothermal method, and the nanowire array and a lithium foil are used as working and counter electrodes, respectively, to assemble a lithium-ion battery. After charging to 4 V, the BiVO 4 nanowire array has a strong oxidizing property. The pyrrole can be in-situ polymerized on the surface of the charged BiVO 4 nanowire array to form a polypyrrole coating layer in pyrrole solution. The morphology and structure properties of the samples are characterized and analyzed in detail. The lithium storage performances of the samples are also measured and compared. The obtained BiVO 4 -PPy nanowires have stable cycle performance and a discharge capacity of more than 400 mAh g−1 after 50 cycles. This work provides a new method for synthesizing conductive polymers on charged electrodes. • A novel in-situ coating polypyrrole (PPy) on charged BiVO 4 nanowires method is used to improve the cycle performance of the electrode. • The obtained BiVO 4 -PPy nanowires have a capacity of more than 400 mAh g−1 at a current density of 100 mA g−1 after 50 cycles in 1–4 V. [ABSTRACT FROM AUTHOR]