Date/Time: 04-04-2018 - Wednesday - 05:00 PM - 07:00 PM
Sujung Kim1 Yena Kim1 2 Hye Ryung Byon1

1, Korea Advanced Institute of Science and Technology, Daejeon, , Korea (the Republic of)
2, RIKEN, Wako, , Japan

Two-dimensional molybdenum disulfide (MoS2) has been extensively investigated in applications for lithium (Li) storage material owing to its high theoretical capacity of ~670 mAh/g, while its low ionic and electrical conductivities and poor reversibility have tackled further development for battery applications.[1] To mitigate these challenges, here we show incorporation of heteroatom with the same chalcogen group, selenium (Se), to MoS2 and design tubular structure by coating on multi-walled carbon nanotube (MWCNT). The molybdenum sulfide selenide (MoSSe) shell on MWCNT structure was synthesized from one-pot hydrothermal reaction. Transmission electron microscopy (TEM) images exhibit bi- or tri-layers of MoSSe shell that coaxially coat the sidewall of MWCNT. Electron energy loss spectroscopy (EELS) analysis reveals 1: 0.7: 1 atomic ratio of Mo: S: Se for MoSSe shell. Notably, the presence of Se distorts total lattice structure, thus increasing the interlayer space to 6.6 Å, which is 0.4 Å larger than Se-free MoS2. To evaluate electrochemical storage capability, few-layer MoSSe/MWCNT composites were prepared to binder-free and three-dimensional (3-D) structural electrode. The specific capacity for MoSSe/MWCNT electrode coupled with a counterpart of metallic Li electrode is ~1,900 mAh/g at a current density of 100 mA/g and ~95% of Coulombic efficiency is delivered. The 3-D electrode structure and few-layer MoSSe on MWCNT may allow for short diffusion distance of Li+ ion and fast electron transfer, respectively. The galvanostatic cell performance with MoSSe/CNT electrode was also compared with the similar structure of MoS2/MWCNT electrode. With increasing a current density to 1,200 mA/g, the capacity of MoSSe/MWNT is a twofold increase in that of MoS2/MWCNT, which indicates intrinsically higher lithium storage capability of MoSSe than MoS2. The decreasing bandgap of MoS2 by addition of Se can enhance electrical conductivity.[2] In addition, the distorting atomic structure may signify the mobility of Li+ ion inside MoSSe shell.[3] The few-layer MoSSe with MWCNT electrode is stably cycled in the measured 30 cycles, which is distinct from poor capacity retention of MoS2/MWCNT electrode.

[1] Nat. Nanotechnol. 2007, 2, 53.
[2] Nanoscale, 2015, 7, 10490.
[3] Nano Lett., 2017, 17, 3518.

Meeting Program

5:00 PM–7:00 PM Apr 4, 2018

PCC North, 300 Level, Exhibit Hall C-E