Bundled Defect-Rich MoS for a High-Rate and Long-Life Sodium-Ion Battery: Achieving 3D Diffusion of Sodium Ion by Vacancies to Improve Kinetics.

Molybdenum disulfide (MoS ), a 2D-layered compound, is regarded as a promising anode for sodium-ion batteries (SIBs) due to its attractive theoretical capacity and low cost. The main challenges associated with MoS are the low rate capability suffering from the sluggish kinetics of Na intercalation and the poor cycling stability owning to the stack of MoS sheets. In this work, a unique architecture of bundled defect-rich MoS (BD-MoS ) that consists of MoS with large vacancies bundled by ultrathin MoO is achieved via a facile quenching process. When employed as anode for a SIB, the BD-MoS electrode exhibits an ultrafast charge/discharge due to the pseudocapacitive-controlled Na storage mechanism in it. Further experimental and theoretical calculations show that Na is able to cross the MoS layer by vacancies, not only limited to diffusion along the layer, thus realizing a 3D Na diffusion with faster kinetics. Meanwhile, the bundling architecture reduces the stack of sheets with a superior cycle life illustrating the highly reversible capacities of 350 and 272 mAh g at 2 and 5 A g after 1000 cycles.