Amorphous MoS ₃ as the sulfur-equivalent cathode material for room-temperature Li–S and Na–S batteries

Abstract

Many problems associated with Li-S and Na-S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS as such a material for room-temperature Li-S and Na-S batteries. In Li-S batteries, MoS exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS can also be used as the cathode material of even more challenging Na-S batteries to enable decent capacity and good cycle life. X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.

Fast‐Charging and Ultrahigh‐Capacity Lithium Metal Anode Enabled by Surface Alloying

“…Figure 4 a depicts the charge and discharge voltage profiles of the full cell for the first 3 cycles between 1.2 and 3.0 V at 0.2 mA cm −2 . They are generally consistent with the reported data of amorphous MoS 3 . The capacity is normalized with respect to the MoS 3 weight, and is calculated to be ≈500 mAh g −1 .…”

“…Next, we paired our sa‐Li anode with an amorphous MoS 3 cathode for the fabrication of full cells. MoS 3 is selected here for its proven large specific capacity (500–600 mAh g −1 ) and great cycling stability in the ether electrolyte . Its areal loading was controlled to be ≈5 mg cm −2 in order to achieve a relatively high areal capacity of 2–3 mAh cm −2 .…”

Sulfur‐Based Electrodes that Function via Multielectron Reactions for Room‐Temperature Sodium‐Ion Storage

“…Ghosh's group developed a sulfur copolymer as a cathode material to address the inherent weaknesses of RT‐NaS batteries in terms of the polysulfide shuttle effect and the low electrical conductivity of elemental S. As shown in Figure g, a sulfur‐rich copolymer (CS90 with S content of ≈90 wt %) could be from cardanol‐functionalized benzoxazine (Ca) and elemental sulfur . More recently it was shown 1D chain‐like S‐rich amorphous MoS 3 can serve as the sulfur‐equivalent cathode in RT‐NaS batteries (Figure h) . Unlike conventional S cathodes, this battery system could fully avoid the generation of soluble polysulfide intermediates but did realize sulfur‐like electrochemical performance.…”

Ultrasmall MoS3 Loaded GO Nanocomposites as High‐Rate and Long‐Cycle‐Life Anode Materials for Lithium‐ and Sodium‐Ion Batteries

“…To improve the electrochemical performance of MoS 3 , J. Lu and co‐workers had prepared the SWCNT/MoS 3 composites, which showed excellent sodium storage properties . They also discussed the electrochemical performance of MWCNT/MoS 3 cathode materials for both Li−S and Na−S batteries . However, except for carbon nanotubes, researches on other carbon modified MoS 3 composites for both LIBs and SIBs were rarely reported.…”