Tetraiodo nickel phthalocyanine electrocatalyst enables superior Na-Se battery performances by enhancing the utilization of Na2Se

Sodium: -Selenium (Na-Se) batteries are regarded as one of the most promising alternative energy storage de-vices compared to their room-temperature sodium-sulfur battery counterparts. Since Selenium cathodes operate well in carbonate-based electrolytes, the solubility issue of polyselenides is no longer an issue. However, the main obstacles of Na-Se batteries remain the precipitation and reoxidation of sodium selenide (Na2Se) owing to the high energy barrier of these reactions and passivation of the electrode during cycling. Herein, we propose a tetraiodo nickel phthalocyanine (NiPc) electrocatalyst to improve the electrochemical performance of Na-Se batteries. It is demonstrated that the presence of even a small amount of NiPc improves the electrocatalytic conversion of Na2Se by lowering the decomposition energy barrier of Na2Se. The improved cell performances are verified by the decrease in reaction polarization, Tafel slope values, and the measured internal resistance of Na-Se cells in addition to the density functional theory (DFT) calculations. Consequently, the Na-Se cell with the NiPc electrocatalyst exhibited outstanding rate capability (405 mAh & BULL;g- 1 after 250 cycles at 3375 mA g-1 and superior long-term cyclic stability (563 mAh & BULL;g- 1 after 250 cycles at 675 mA g-1), which are among the most promising rate performance characteristics demonstrated in the literature.