Coordination Defect-Induced Lewis Pairs in Metal-Organic Frameworks Boosted Sulfur Kinetics for Bifunctional Photo-Assisted Li-S Batteries

The photo-assisted strategy is regarded as a crucial approach to enhance the conversion kinetics of polysulfides in lithium-sulfur (Li-S) batteries. However, the development of photo-assisted Li-S batteries still faces important challenges, such as the rapid recombination of photogenerated electron-holes on cathode and more severe shuttle effect. Herein, a breakthrough in overcoming the challenges has been made by constructing a promising photo-assisted Li-S battery based on semiconducted metal-organic frameworks. During the discharging progress, the photoexcited electrons generated by H2BPDC ligand based on ligand-to-metal charge transfer (LMCT) effect, are injected into the Ti-oxo clusters in Ti-MOF, thereby facilitating the sulfur reduction to Li2S. And photoexcited holes are capable of promoting the decomposition kinetics of Li2S during charging. More importantly, the stronger chemical interaction between Ti-BPDC-d and polysulfides under light inhibits the polysulfides dissolution and shuttling, which fundamentally addresses the issue of light-accelerated shuttling. As a result, the photo-assisted Li-S batteries deliver a reversible capability of 1090.21 mAh g-1 at 0.2 C with a capacity retention of 82.91% over 150 cycles, and a superior rate capability of 673.58 mAh g-1 at 5 C. The findings are promising in advancing the design principles for photo-rechargeable Li-S batteries. A new perspective for a photo-assisted Li-S battery systems based on Ti-MOF with ligand defects is proposed, which improves the efficiency of photogenerated electron-holes separation, greatly promoting redox reaction kinetics. Additionally, the introduction of light enhances the chemical affinity between Ti-BPDC-d and polysulfides, which inhibits the LiPSs shuttling. image