Synthesis of standalone $SnS_2$ particle as an anode for sodium-ion batteries

Abstract

Recently, demand for large scale energy storage system is increasing. Among energy storage system (ESS), battery system have drawn attentions because of high energy density. In various battery systems, sodium ion battery (SIB) system is the promising large-scale ESS because Sodium is cheaper than lithium due to richness of sodium in crust. Also, Sodium and lithium are in the same period on the periodic table. So the both elements have similar physical and chemical properties, resulting in applying advanced technology of lithium ion battery (LIB) to SIB. Among the candidates of various materials for battery, conversion materials such as metal oxide, metal sulfide are attracting attention as an anode material for SIBs because of high capacity. In order to synthesize high capacity $SnS_x$ without carbon and binder, Sn and SnS was each electrodeposited on Al current collector directly and then $SnS_x$ was synthesized by sulfiding as-deposited Sn and SnS. when Sn was sulfide, It was observed that the particles size significantly increased to 4 ~ 5 um and the particle shape changed to spherical shape. On the other hand, when the SnS was sulfided, the size and shape was almost the same as before the sulfurization treatment. From the XRD pattern analysis, it was confirmed that the sulfided Sn were phase-transformed into hybrid of SnS, $Sn_3S_4$ and $SnS_2$ and the sulfided Sn were phase-transformed into crystalline $SnS_2$. From the electrochemical tests, $SnS_x$ microsphere showed high initial capacity but had poor retention ability. Meanwhile, it was confirmed that $SnS_2$ nanoparticles has not only high capacity but also superb retention ability. As a results, we synthesized $SnS_2$ nanoparticles having outstanding electrochemical performance. Also, the active materials were used as a conductive agent and binder-free anode for SIBs.