Understanding Charge Storage Mechanisms for Amorphous MoSnSe1.5S1.5 Nanoflowers in Alkali‐Ion Batteries

Transition metal sulfides/selenides have been reported as promising materials for alkali‐ion batteries owing to their high pseudocapacitive effects and large capacities. However, these materials undergo large volume expansion, which results in poor cycling retention. Hence, in this study, an amorphous bimetallic chalcogenide, MoSnSe1.5S1.5 (MSSS), is synthesized to mitigate the volume expansion. By introducing an amorphous structure, MSSS can reach high capacities of 805 mAh g‒1 in Li‐ion batteries (LIBs) and 526 mAh g‒1 in Na‐ion batteries (NIBs) at a current density of 0.1 A g‒1. Moreover, amorphous MSSS can tolerate a high current density of 20 A g‒1 and possess high percentages of capacitance contributions in both LIBs and NIBs. To explore fundamentals, in situ/operando measurements, such as X‐ray absorption spectroscopy, transmission X‐ray microscopy, and transmission electron microscopy, are utilized to investigate real‐time phenomena and consequently establish the reaction mechanisms for amorphous MSSS electrodes in alkali‐ion batteries. In this study, self‐assembled amorphous MoSnSe15S15 nanoflowers are synthesized, achieving remarkable cycling stability as anode materials in lithium‐ and sodium‐ion batteries with fast charging/discharging rates. To unravel the mechanisms behind these exceptional capacities and stabilities, sophisticated operando techniques such as X‐ray absorption spectroscopy, transmission electron microscopy, and transmission X‐ray microscopy are employed.