Sodium-Selenium Batteries with Outstanding Rate Capability by Introducing Cubic Mn₂ O₃ Electrocatalyst

With their high volumetric capacity and electronic conductivity, sodium-selenium (Na-Se) batteries have attracted attention for advanced battery systems. However, the irreversible deposition of sodium selenide (Na₂ Se) results in rapid capacity degradation and poor Coulombic efficiency. To address these issues, cubic α-Mn₂ O₃ is introduced herein as an electrocatalyst to effectively catalyze Na₂ Se conversion and improve the utilization of active materials. The results show that the addition of 10 wt% Mn₂ O₃ in the selenium/Ketjen black (Se/KB) composite enhances the conversion from Na₂ Se to Se by lowering activation energy barrier and leads to fast sodium-ion kinetics and low internal resistance. Consequently, the Mn₂ O₃ -based composite delivers a high specific capacity of 635 mAh ⋅ g^-1 at 675 mA ⋅ g^-1 after 250 cycles as well as excellent cycling stability for 800 cycles with a high specific capacity of 317 mAh ⋅ g^-1 even at the high current density of 3375 mA ⋅ g^-1 . Due to the cubic Mn₂ O₃ electrocatalyst, the performance of the composites is superior to existing state-of-the-art Na-Se batteries reported in the literature.