Inverse Capacity Growth and Pocket Effect in SnS2 Semifilled Carbon Nanotube Anode.

SnS2 with high theoretical capacity has been impeded from practical applications as the anode of lithium-ion (Li-ion) batteries due to its large volume expansion and fast capacity decay. A nanostructure of the SnS2 semifilled carbon nanotube (SnS2@CNT) has been realized by plasma-assisted fabrication of Sn semifilled CNT (Sn@CNT) followed by post-sulfurization. When serving as the anode of a Li-ion battery, SnS2@CNT delivers an initial discharge capacity of 1258 mAh g-1 at 0.3 A g-1. Instead of capacity fading, SnS2@CNT shows inverse capacity growth to 2733 mAh g-1 after 470 cycles. The high-resolution transmission electron microscopy images show that the void in CNTs, after cycling, is fully filled with pulverized SnS2 grains which have a shortened Li-ion diffusion path and enhanced surface area for interfacial redox reactions. In addition, the CNTs, like a pocket, confine the pulverized SnS2, maintain the electric contact and structural integrity, and thus allow the electrodes to work safely under long cyclic loadings and extreme temperature conditions.