Ternary molybdenum oxyphosphide based hybrid nanotubes boosts sodium-ion diffusion kinetics enabled through oxygen-deficient modulation

Abstract

Sodium-ion hybrid capacitors (SIHCs) possess high energy density but often suffer from relatively low power density mainly due to their sluggish battery-type anode. Herein, we synthesized innovative porous molybdenum dioxide nanotubes that were spirally grown high-conductive carbon sheets with uniformly deposited molybdenum oxyphosphide clusters (∼1.6 nm, MOP@C@MOP). It is discovered that the carbon sheet-spirally enforced MOP tubes can meritoriously inhibit the volume variation through cycles while their high porosity and conductivity allow fast mass and charge transport, respectively. Further, rich oxygen deficiency was delicately tailored to modulate ternary MOP for a high density of reaction active centers. The as-prepared anode delivers a high reversible capacity of 261.5 mAh g⁻¹ (@100 mA g⁻¹) after 500 cycles and even maintains 5500 cycles at a current density of 1000 mA g⁻¹, a capacity can still retain 86.5 % of the initial capacity, overwhelming the most reported molybdenum dioxide lifespan. This work vividly demonstrates an effective method to simultaneously tune both the physics (nanostructure) and chemistry (composition) of electrode material for greatly improved high power density for battery-type hybrid capacitors.