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Multi-wall Sn/SnO2 @carbon hollow nanofibers evolved from SnO2 nanofibers are designed and programable synthesized by electrospinning, polypyrrole coating, and annealing reduction. The synthesized hollow nanofibers have a special wire-in-double-wall-tube structure with larger specific surface area and abundant inner spaces, which can provide effective contacting area of electrolyte with electrode materials and more active sites for redox reaction. It shows excellent cycling stability by virtue of effectively alleviating pulverization of tin-based electrode materials caused by volume expansion. Even after 2000 cycles, the wire-in-double-wall-tube Sn/SnO2 @carbon nanofibers exhibit a high specific capacity of 986.3 mAh g-1 (1 A g-1 ) and still maintains 508.2 mAh g-1 at high current density of 5 A g-1 . This outstanding electrochemical performance suggests the multi-wall Sn/SnO2 @ carbon hollow nanofibers are great promising for high performance energy storage systems.

Precisely carving of multi-shelled manganese-cobalt oxide hollow dodecahedra (Co/Mn-HD) with shell number up to three is achieved by a controlled calcination of the Mn-doped zeolitic imidazolate framework ZIF-67 precursor (Co/Mn-ZIF). The unique multi-shelled and polycrystalline structure not only provides a very large electrochemically active surface area (EASA), but also enhances the structural stability of the material. The residual C and N in the final structures might aid stability and increase their conductivity. When used in alkaline rechargeable battery, the triple-shelled Co/Mn-HD exhibits high electrochemical performance, reversible capacity (331.94 mAh g-1 at 1 Ag-1 ), rate performance (88 % of the capacity can be retained with a 20-fold increase in current density), and cycling stability (96 % retention over 2000 cycles).