MoS2 Nanosheets Vertically Aligned on Carbon Paper: A Freestanding Electrode for Highly Reversible Sodium Ion Batteries

Abstract

The renaissance of sodium-ion batteries (SIBs) in the last few years provides a promising environmentally friendly alternative for energy storage and conversion (ESC).1 , 2 MoS2, a layered material with a large interlayer spacing along the c-axis (0.62 nm), has been attracting extraordinary attention as anode materials for SIBs. However, pure MoS2 exhibited poor rate capability and fast capacity decay upon cycling. Nanostructuring and hierarchical electrode architectures are required to facilitate transport of Na-ions within electrodes.3 Herein, we report on a rational design of freestanding anode materials for sodium-ion batteries, consisting of MoS2 nanosheets aligned vertically on carbon paper derived from paper towel.4 The hierarchical structure enables sufficient electrode/electrolyte interaction and fast electron transportation. Meanwhile, the unique architecture can minimize the excessive interface between carbon and electrolyte, enabling high ICE. When employed as freestanding electrodes for SIBs, the as-prepared MoS2@carbon paper composites delivered a high reversible capacity of 446 mA h g-1 at 20 mA g-1, high ICE (79.5%), and promising rate capability. Even at a high current density of 1000 mA g-1, a reversible capacity of 205 mA h g-1 was maintained.By exploiting in situ Raman spectroscopy, we observed the reversibility of the phase transition from 2H-MoS2 to 1T-MoS2 during the sodium-ion intercalation/de-intercalation process.