Vertically Oriented MoS 2 with Spatially Controlled Geometry on Nitrogenous Graphene Sheets for High-Performance Sodium-Ion Batteries

Lithium-ion battery (LIB) has been a tremendous success for decades. As the demand for rechargeable batteries surges, a need has arisen for low-cost secondary batteries. Among various studies, sodium-ion battery (SIB) is the most promising secondary batteries due to its similar working principles and the abundance of sodium in the natural world. Among many anode materials for SIB, MoS­­ 2 has attracted attention because it can intercalate sodium ions in its layered structure. However, in the repeated intercalation of Na + , MoS 2 suffers from collapse of its layered structure. Herein, we present vertically grown MoS 2 on nitrogenous reduced graphene oxides (N-RGO) with controlled sheet density and height of MoS2 sheets as SIB anode active material. The MoS 2 materials are synthesized by gel-precursor based method. By adjusting the nucleation and growth processes, we controlled the height and density of MoS 2 sheets to find optimal condition that show great performance and high stability. Control of the partial geometry can achieve these improved property because the high sheet density can prevent additional SEI layer and the shortened sheet length reduces the resistance of Na + diffusion. It shows remarkably high reversible discharging capacity of 255mAh/g at 1C and 245mAh/g at 5C discharging with a capacity reduction of 5.35% after 1300 cycles. And closely packed MoS 2 sheets shows specific capacity of 254, 243, 153, 86 mAh/g at 0.2, 2, 10, 50A/g current density, respectively. Furthermore, vertically grown MoS 2 is paired with Na 3 V 2 (PO 4 ) 3 to fabricate SIB full cell, and the full cell shows a specific capacity of 262mAh/g (based on the mass of anode material) during 50 cycles. Figure 1