A Photo-Assisted Reversible Lithium-Sulfur Battery

A groundbreaking photo-assisted lithium-sulfur battery (LSB) is constructed with CdS-TiO2/carbon cloth as a multifunctional cathode collector to accelerate both sulfur reduction reaction (SRR) during the discharge process and sulfur evolution reaction (SER) during the charge process. Under a photo illumination, the photocatalysis effect derived from the photo-generated electrons/holes efficiently decreases the reaction energy barrier of polysulfides to Li2S by 70 mV; and the photoconductive effect largely increases the charge concentration and boosts the electrochemical kinetics because of abundant photo-generated carriers. The photo-assisted LSB could also be directly photo-charged and gain a specific discharge capacity of 608 mA h g−1 with a high energy conversion efficiency of 2.3%, which is about 36.3% of the theoretical specific capacity of the LSB. Consequently, a stable reversible capacity of approximately 1225 mA h g−1 is achieved with an outstanding 100% energy efficiency, which is ∼10% higher than the circumstance of no light illumination, indicating that the photo-assisted LSB achieves an apparent lossless energy storage under only 0.5-sun illumination in the wavelength range of 300-800 nm. This work provides a completely sustainable model for efficiently promoting the electrochemical performances of LSBs.