Fully Reversible Conversion between SnO₂ and Sn in SWNTs@SnO₂@PPy Coaxial Nanocable As High Performance Anode Material for Lithium Ion Batteries

In this report, we designed a novel SWNTs@SnO₂@PPy coaxial nanocable as superior anode material for the first time. The nanosized SnO₂ particles (2–3 nm) were uniformly distributed between one dimension SWNTs core and PPy shell, as confirmed by XRD, SEM, and TEM characterizations. As an anode material for lithium ion batteries, this composite delivered a high capacity of 823 mAh g^–1 at 150 mA g^–1 after 100 cycles. Even at a high rate of 3000 mA g^–1, a reversible capacity of 480 mAh g^–1 still remained. Furthermore, the SnO₂ in this composite exhibited a large capacity of 1486 mAh g^–1 as well as good capacity retention of 95% over 100 cycles. This result indicated the completely reversible reaction between Li_4.4Sn and SnO₂, greatly improving the theoretical capacity of SnO₂ from 782 to 1493 mAh g<sup>–1