Rational Design of Unique MoSe 2 -Carbon Nanobowl Particles Endows Superior Alkali Metal-Ion Storage Beyond Lithium.

Attracted by the rich earth abundance and low-cost advantages, alkali metal-ion (Na/K)-based energy storage devices have attracted wide interest as promising candidates for energy economizing in recent years. Unfortunately, the lack of suitable host materials with high capacity and long life span for alkali metal-ion storage has severely impeded their practical application in large-scale energy storage devices. Herein, we present a promising anode candidate composed of ultrasmall MoSe 2 clusters embedded in a nitrogen-doped hollow carbon nanobowl substrate to form unique MoSe 2 -Carbon nanobowl particles (denoted as MoSe 2 ⊂CNB). MoSe 2 ⊂CNB demonstrates exceptional electrochemical properties for alkali metal-ion storage including sodium and potassium. In situ Raman spectroscopy and galvanostatic intermittent titration measurements reveal the possible reason for the high performance of MoSe 2 ⊂CNB. Notably, the assembled potassium-ion hybrid capacitors could manifest an extraordinary energy density of 130.7 W h kg -1 at 0.2 A g -1 , a high power density of 13,607 W kg -1 , and an enviable cycle life after 6000 cycles, further reflecting the great developmental potential for energy storage devices in practical applications. This work provides a new method to design functional nanostructures for electrode materials to drive the development and application of possible energy storage devices.