Effect of Carbon Black Materials on the Electrochemical Properties of Sulfur-Based Composite Cathode for Lithium-Sulfur Cells

To investigate the effect of the electrode materials on the electrochemical performance of Li-S cells, sulfur cathodes were constructed using four types of carbon blacks: Ketjenblack EC-600JD (KB-600), Printex XE-2, Cabot BP-2000, and Super-P. It was found that the electrochemical performance of sulfur cathode was strongly dependent on the type of carbon black used. In the first discharge, the sulfur cathodes containing carbon blacks with a high surface area, KB-600 (S _BET = 1270 m²/g), Printex XE-2 (S _BET = 950 m²/g), or Cabot BP-2000 (S _BET = 1487 m²/g), showed much higher discharge capacities (> 1200 mA h/g) than the sulfur cathode (710 mA h/g) with Super-P (S _BET = 62 m²/g). It was observed that the sulfur cathodes with KB-600, Printex XE-2, or Cabot BP-2000, which showed very similar discharge capacities one another at a low rate of 0.2 C, exhibited significantly different electrochemical behavior (the discharge capacity and midvoltage) at a high rate of 1.0 C. In particular, the sulfur cathode with KB-600 showed an extremely high capacity (831 mA h/g) with a midvoltage of 2.07 V at a 1.0 C rate, and excellent capacity retention (79%) after 50 cycles.