Inverse Capacity Growth and Pocket Effect in SnS<sub>2</sub> Semifilled Carbon Nanotube Anode.

Jin, Xiaozhe; Huang, Hao; Wu, Aimin; Gao, Song; Lei, Mingkai; Zhao, Jijun; Gao, Xiaoxia; Cao, Guozhong · ACS Nano · 2018

basic_science · Level V

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Abstract

SnS<sub>2</sub> 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 SnS<sub>2</sub> semifilled carbon nanotube (SnS<sub>2</sub>@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, SnS<sub>2</sub>@CNT delivers an initial discharge capacity of 1258 mAh g<sup>-1</sup> at 0.3 A g<sup>-1</sup>. Instead of capacity fading, SnS<sub>2</sub>@CNT shows inverse capacity growth to 2733 mAh g<sup>-1</sup> after 470 cycles. The high-resolution transmission electron microscopy images show that the void in CNTs, after cycling, is fully filled with pulverized SnS<sub>2</sub> 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 SnS<sub>2</sub>, maintain the electric contact and structural integrity, and thus allow the electrodes to work safely under long cyclic loadings and extreme temperature conditions.