Despite their potential application in lithium-ion battery electrodes, one apparent disadvantage for SnO 2based materials is that the electrodes sufferlow coulombic efficiency especially for the initial cycle, which originates from the irreversible conversion of SnO 2 to Sn, the formation of solid electrolyte interphase and the other possible side reactions. Here we design a novel nanofiber structure in which SnO 2 nanoparticles are well separated and confined by inner porous carbon framework and then hooped by outer carbon shell. The resultant SnO 2 /voids@C nanofibers electrode displays not only a high reversible capacity of 986mAh g-1 at 200 mA g-1 after 200 cycles, but also a high initial coulombic efficiency of 73.5%.It has been shown that such a rational design can efficiently reduce the side reactions and promote the reversible conversion of Sn to SnO 2 for both half and full cells.

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SummaryA novel network of spindle-like carbon nanofibers was fabricated via a simplified synthesis involving electrospinning followed by preoxidation in air and postcarbonization in Ar. Not only was the as-obtained carbon network comprised of beads of spindle-like nanofibers but the cubic MnO phase and N elements were successfully anchored into the amorphous carbon matrix. When directly used as a binder-free anode for lithium-ion batteries, the network showed excellent electrochemical performance with high capacity, good rate capacity and reliable cycling stability. Under a current density of 0.2 A g−1, it delivered a high reversible capacity of 875.5 mAh g−1 after 200 cycles and 1005.5 mAh g−1 after 250 cycles with a significant coulombic efficiency of 99.5%.

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