Enhanced chemisorption and catalytic conversion of polysulfides via CoFe@NC nanocubes modified separator for superior Li-S batteries

The coordination mechanism of adjusting the chemical adsorption and catalytic conversion of polysulfides plays a key role in the development of high energy density lithium-sulfur (Li-S) batteries. Herein, a CoFe alloy is locked in situ in nitrogen-doped carbon nanocube (denoted as CoFe@NC) as a bifunctional separator modification material for Li-S batteries. The obtained CoFe@NC nanocubes exhibit strong chemisorption and catalytic conversion activity of double polysulfides, leading to the enhanced redox kinetics and the reduced polysulfide shuttle effect for Li-S batteries. As expected, the batteries assembled with CoFe@NC modified separator (CoFe@NC//PP batteries) show high specific capacity and long cycle stability. Specifically, the CoFe@NC//PP batteries exhibit a high initial specific capacity of 1473 mA h g-1 at 0.1C, excellent rate capacity of 604 mA h g-1 at 4C, as well as superior cycle stability with the capacity decay rate of only 0.059% per cycle for 1000 cycles at 1C. Additionally, the satisfactory electrochemical performance can be achieved even in the case of high sulfur loading (6.60 mg cm-2) and low electrolyte (E/S is about 7 mu L mg -1). Therefore, this work provides a reliable reference to develop effective intermetallic compounds with chemical adsorption and catalytic conversion of polysulfides for high-performance lithium-sulfur batteries.

Automated summary

The coordination mechanism of adjusting the chemical adsorption and catalytic conversion of polysulfides is crucial for the development of high energy density lithium-sulfur batteries. In this study, a CoFe@NC nanocubes material was successfully synthesized and used as a bifunctional separator modification for Li-S batteries. The CoFe@NC nanocubes exhibited strong chemisorption and catalytic conversion activity, leading to enhanced redox kinetics and reduced polysulfide shuttle effect. Li-S batteries assembled with CoFe@NC modified separator showed high specific capacity, excellent rate capacity, and superior cycle stability, even at high sulfur loading and low electrolyte conditions.