Carbonyl‐β‐Cyclodextrin as a Novel Binder for Sulfur Composite Cathodes in Rechargeable Lithium Batteries

As one of the essential components in electrodes, the binder affects the performance of a rechargeable battery. By modifying β ‐cyclodextrin ( β ‐CD), an appropriate binder for sulfur composite cathodes is identified. Through a partial oxidation reaction in H 2 O 2 solution, β ‐CD is successfully modified to carbonyl‐ β ‐cyclodextrin (C‐ β ‐CD), which exhibits a water solubility ca. 100 times that of β ‐CD at room temperature. C‐ β ‐CD possesses the typical properties of an aqueous binder: strong bonding strength, high solubility in water, moderate viscosity, and wide electrochemical windows. Sulfur composite cathodes with C‐ β ‐CD as the binder demonstrate a high reversible capacity of 694.2 mA h g (composite) −1 and 1542.7 mA h g (sulfur) −1 , with a sulfur utilization approaching 92.2%. The discharge capacity remains at 1456 mA h g (sulfur) −1 after 50 cycles, which is much higher than that of the cathode with unmodified β ‐CD as binder. Combined with its low cost and environmental benignity, C‐ β ‐CD is a promising binder for sulfur cathodes in rechargeable lithium batteries with high electrochemical performance.