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

Abstract

• The CoFe@NC as a bifunctional separator modification material for Li-S batteries. • CoFe@NC nanocubes exhibit strong chemisorption and catalytic conversion activity. • The CoFe@NC//PP batteries exhibit excellent rate capacity and superior cycle stability. • High performance achieved by high sulfur loading and low electrolyte (7 μL mg −1 ). 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 μL 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.