Ethanol reduced molybdenum trioxide for Li-ion capacitors

Highlights: • Partial reduction of MoO₃ in ethanol results in its increased interlayer spacing. • Binder-free electrodes are fabricated and compared to traditional electrodes. • The electrodes showed excellent cyclic performance (92% capacitance after 5000). • The capacitance of reduced electrodes is higher than previously reported values. Orthorhombic molybdenum trioxide (α-MoO₃) is a layered oxide with promising performance as electrode material for Li-ion capacitors. In this study, we show that expansion of the interlayer spacing (by ~0.32 Å) of the structure along the b-axis, introduced by partial reduction of α-MoO₃ and formation of MoO_3−x (x=0.06–0.43), results in enhanced diffusion of Li ions. Binder-free hybrid electrodes made of MoO_3−x nanobelts and carbon nanotubes show excellent electrical conductivity. The combination of increased interlayer spacing and enhanced electron transport leads to high gravimetric and volumetric capacitances of about 420 F/g or F/cm³ and excellent cycle life of binder-free MoO_3−x electrodes.