Dual additive of lithium titanate and sulfurized pyrolyzed polyacrylonitrile in sulfur cathode for high rate performance in lithium-sulfur battery.

Abstract

Lithium-Sulfur (Li-S) batteries have attracted much attention as next-generation batteries due to their high theoretical energy density. However, lithium polysulfide generated during the discharge loses intimate electrical contact with the carbon matrix due to its high solubility in the electrolyte, causing a high charge transfer resistance and slow redox kinetics for the discharge reactions, resulting in a low rate capability. A cathode additive having a strong chemical adsorbing site toward the polysulfide can effectively inhibit their dissolution. We now report a dual additive of lithium titanium oxide (LTO) and sulfurized polyacrylonitrile (SPAN). LTO provides a rapid charge transfer and a fast Li+ ion transfer in the cathode. On the other hand, SPAN helps to enhance the polysulfide adsorption capability. This dual additive system synergistically supplies the cathode with a strong polysulfide adsorption capability and fast redox kinetics. As a result, the dual additive exhibits high discharge capacities of 1430 mA h g-1 at 0.1C and 1200 mA h g-1 at 0.5C at the high-sulfur-loading cathode of 5.0 mg cm-2. Our findings demonstrated the manufacturing of the cathode with a strong polysulfide adsorption capability and a fast redox reaction which could then effectively improve the rate performance of the Li-S batteries.