Metallic Phase 2D MoS₂ Nanosheets as Anodes for Sodium-Ion Batteries

Next-generation of batteries beyond the Li-ion chemistry is needed for cost-efficient and large-scale systems. Na-ion batteries (SIB) have emerged as an alternative to Li-batteries. However, challenges relating to intrinsic properties of sodium ion intercalation remain and performance of SIBs must be improved. In this work, we have investigated anodes based on restacked metallic MoS₂ 2D transition metal dichalcogenide (TMDs) nanosheets for SIBs. We have found that electrodes from restacked metallic 1T phase MoS₂ nanosheets in SIBs offer distinct advantages. These include: (1) larger cations can be easily intercalated and de-intercalated into the electrodes; (2) enhanced electroconductivity that facilitates the diffusion of the ions; and (3) improved electrocatalytic activity that can catalyze desired reactions. Based on these principles, we have achieved SIBs with the first cycle capacity of 520 mAh g^-1 with a reversible efficiency of ~ 50 % and cycle stability of 80 % at 50 cycles. We employ Raman, XPS, and XRD measurements to figure out the intercalation mechanism of these materials before and after cycling.