Inherent electrochemical activity of TiO2 (anatase, rutile) enhances the charge capacity of cathodes of lithium-sulfur batteries
Abstract
The addition of nanocrystalline titanium dioxide (P90) to a cathode of Li/S cell enhances its voltammetric charge capacity by 19%, from which only a small fraction (ca. 1%) is assignable to the intrinsic Li-storage in TiO2. The flatband potential of anatase (the main component of P90) and rutile (the second main component of P90) equals 2.1 V vs.
Li(+)/Li for both anatase and rutile. The S8 reduction is triggered at the same potential, confirming that TiO2 behaves like an ideally rectifying semiconductor electrode for sulfur.
The modification of glass-fiber separator by P90 further improves the charge capacity of the Li/S cell. Titanium dioxide is active in the Li/S cell not only for immobilization of polysulfides on the sulphiphilic surface but also due to its inherent electrochemical activity for sulfur reduction at potentials negative to Vfb.