Versatile alkali-ion storage in hierarchically porous Mo2C@C hybrid architectures

Abstract

Transition metal carbides (TMCs) offer high conductivity and structural stability, engendering growing interest as promising anode materials for next-generation alkali-ion batteries. A hierarchically porous Mo2C@C (PMC) composite was synthesized herein via a scalable and environmentally benign salt-templated freeze-drying method. The resulting three-dimensional, porous architecture, comprising uniformly dispersed Mo2C nanocrystals embedded in a conductive carbon matrix, afforded a high specific surface area of 289 m2 g−1 and well-defined micropores and mesopores. When applied in the anode of lithium-, sodium-, and potassium-ion batteries (LIBs, SIBs, and KIBs), PMC delivered exceptional electrochemical performance, with reversible capacities of 556, 163, and 231 mAh g−1, respectively, at 50 mA g−1 over 100 cycles—significantly outperforming commercial Mo2C. Combined in situ and ex situ XRD, SAXS, and XPS analyses revealed distinct storage mechanisms for each alkali ion, where Li+ and K+ engage in both surface and pore-level processes, whereas Na+ storage is dominated by surface-limited pseudocapacitance owing to sluggish kinetics. The superior performance of PMC in LIBs and KIBs is attributed to its accessible surface for efficient charge transfer and its optimized pathways for ion transport. This study provides new insights into ion-specific storage mechanisms in Mo2C-based architectures and establishes design principles for multi-ion-compatible electrode materials.