Targeted Catalysis of the Sulfur Evolution Reaction for High-Performance Lithium-Sulfur Batteries

摘要

The sluggish kinetics of the sulfur evolution reaction (SER) that occur becauseof the high oxidation barrier of Li_2S causes low sulfur utilization and thepoor rate performance of lithium–sulfur batteries. However, the design ofthe catalysts to solve this problem is still hard to achieve because it is difficultto precisely correlate the catalytic oxidation ability with the electronicstructure. Here, a layer transition metal oxide, Na_xTi_(0.5)Co_(0.5)O_2, is used as amodel catalyst to probe such a correlation because it has a tunable electronicstructure and good stability in the working potential window of Li–S batteries.By removing Na~+, a partial phase change gradually increases the concentrationof Co active sites while decreasing the work function with an upshift of theFermi level, accelerating charge transfer on the catalyst surface and thereforeimproving its catalytic oxidation activity of Li_2S. In particular, Na_(0.7)Ti_(0.5)Co_(0.5)O_2with two-phases coexisting effectively lowers the activation potential of Li_2S,leading to minimum polarization and excellent rate performance, and evenat 5.0 C, the assembled cell has a high capacity of 615 mAh g~(?1). This studyindicates a way to optimize the electronic structure to enhance the SER, whichis important for promoting the practical use of Li–S batteries.