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 H2O2 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. The sulfur utilization and cycling stability of composite cathodes in rechargeable lithium batteries are enhanced by carbonyl‐β‐cyclodextrin (C‐β‐CD) as the binder in sulfur composite cathodes. This is made possible by the fact that C‐β‐CD is highly soluble in water, ca. 100 times more soluble than β‐CD at room temperature, and because it exhibits strong bonding strength.