Scalable Composites Benefiting from Transition-Metal Oxides as Cathode Materials for Efficient Lithium-Sulfur Batteries

Abstract

Composite materials achieved by including transition-metal oxides with different structures and morphologies in sulfur are suggested as scalable cathodes for high-energy lithium-sulfur (Li-S) batteries. The composites contain 80 wt.% sulfur and 20 wt.% of either MnO2 or TiO2, leading to a sulfur content in the electrode of 64 wt.% and revealing a reversible, fast, and lowly polarized conversion process in the cell with limited interphase resistance. The S-TiO2 composite exhibits an excellent rate capability between C/10 and 2C, and a cycle life extended over 400 cycles at 2C, owing to the effects of the nanometric TiO2 additive in boosting the reaction kinetics. Instead, the micrometric sized particles of MnO2 partially limit the electrochemical activity of S-MnO2 to the current rate of 1C. Nevertheless, both S-MnO2 and S-TiO2 withstand a sulfur loading up to values approaching 6 mgcm-2, and deliver an areal capacit ranging from about 4.5 to 5.5 mAhcm-2 at C/5. The excellent performances of the metal oxide-sulfur electrodes, even at high active material loading, and the possible scalability of the synthetic pathway adopted in the work suggest that the composites are viable cathodes for next-generation Li-S batteries with high energy density and efficient electrochemical process.