Mesoporous TiO2 coating on carbon–sulfur cathode for high capacity Li–sulfur battery†
In this paper, a meso-porous TiO2 (titania) coating is shown to effectively protect a carbon–sulfur composite cathode from polysulfide dissolution. The cathode consisted of a sulfur impregnated carbon support coated with a few microns thick mesoporous titania layer. The carbon–sulfur cathode is made using activated carbon powder (ACP) derived from biomass. The mesoporous titania coated carbon–sulfur cathodes exhibit a retention capacity after 100 cycles at C/3 rate (433 mA g −1) and stabilized at a capacity around 980 mA h g−1. The electrochemical impedance spectroscopy (EIS) of the sulfur cathodes suggests that the charge transfer resistance at the anode, (Ract) is stable for the titania coated sulfur electrode in comparison to a continuous increase in Ract for the uncoated electrode implying mitigation of polysulfide shuttling for the protected cathode. Stability in the cyclic voltammetry (CV) data for the first 5 cycles further confirms the polysulfide containment in the titania coated cathode while the uncoated sulfur electrode shows significant irreversibility in the CV with considerable shifting of the voltage peak positions. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) studies confirm the adsorption of soluble polysulfides by mesoporous titania.