MoS2 microflowers as a stable and high performance anode material for sodium-ion batteries

Abstract

Sodium-ion batteries are most probable alternative system to current Li-ion batteries, because of sodium is highly abundant in earth's crust. But, Na-ion batteries still have many obstacles for commercialization, although researchers have proposed a number of electrode materials for Na-ion batteries [1, 2]. In particular, negative electrodes for Na-ion batteries are one of the major challenging issues, because graphite, the representative anode material for Li-ion batteries, shows low Na-ion intercalation/deintercalation capability [3]. Here we report the pure MoS2 microflowers with nano-sized petals which are prepared by combination of hydrothermal reaction followed by calcination for Na-ion battery anode materials. The electrochemical performance of MoS2 microflowers with different binders (PVDF, PEO and Na-alginate) is evaluated against pure Na metal in a half-cell configuration through a conversion reaction. Especially, the electrode of MoS2 microflowers with a Na-alginate binder shows excellent cyclic stability, delivering a high discharge capacity of 595 mAh g-1 after 50 cycles. Also, it exhibit high rate capability, retaining a capacity of 236 mAh g-1 at 10C without any carbonaceous materials. The improved electrochemical performance was mainly attributed to the synergetic effect of the morphology of MoS2 microflowers and good adhesive properties of alginate binder. Furthermore, we report a Na-ion full cell using the MoS2 microflowers anode with a Na3V2O2x(PO4)2F3-2x/C as a cathode material.