2D heterostructural Mn2O3 quantum dots embedded N-doped carbon nanosheets with strongly stable interface enabling high-performance sodium-ion hybrid capacitors

Abstract

The ingenious architectural structural engineering is extensively identified as a cogent means for facilitating the electrochemical properties of conversion-type anode materials for sodium-ion storage. Herein, a delicate, scalable and controllable solvent-free strategy is proposed to synthesize ultrafine Mn2O3 quantum dots embedded into N-doped carbon to generate two-dimensional (2D) composites (MNC) with robust interfacial heterostructural interactions for high sodium ion storage and fast reaction kinetics, which averts the use of solvents and environmental pollution, greatly reduces time and production costs. The introduction of metallic Mn species simultaneously achieves the construction of ultrafine Mn2O3 quantum dots and strong interfacial heterostructural COMn bonds between metal species and 2D N-doped carbon matrix. The synergistic effect of the formation of oxide quantum dots, the combination of 2D N-doped carbon and the construction of robust interfacial interactions provides the stable electrode structure, fast reaction kinetics and high electrochemical storage capability of anode materials. Hence, MNC composites in SIBs convey remarkable reversible rate capability. Its superior capacity reaches 215 mAh g−1 for 50 cycles at 0.2 A g−1 and 155 mAh g−1 for 1000 cycles at a high current density of 5 A g−1, which shows good long-term stability. The assembled sodium-ion hybrid capacitors (SIHCs) device delivers outstanding energy density of 138 Wh kg−1 at a power density of 126 W kg−1 and 98% capacity retention after 2000 cycles at 2 A g−1, and tremendous capability for practical applications (69 LEDs can be easily lighted). This work not merely offers guidance for the rational interfacial engineering design of high-capacity Mn-based electrode materials in a feasible and scalable solvent-free tactics for Na+ storage, but also broadens the routes for projecting a better electrode material for other battery systems.