A strategy of combination reaction to improve electrochemical performance in two-dimensional Mo1-W Se2 battery-type electrode materials

We report here a case of combination reaction between MoSe2 and WSe2 in certain proportions to improve electrochemical performance of Mo1-xWxSe2 compound materials. Two-dimensional (2D) Mo1-xWxSe2 flower-like crystals (x = 0, 0.25, 0.5, 0.75, 1) were synthesized using a solution synthesis method, and then Mo1-xWxSe2-based electrodes were prepared using a powder pellet method. Their structure and electrochemical performance were respectively measured by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS), scanning electron microscope (SEM), and electrochemical workstation. The results indicate that only Mo0.25W0.75Se2-based electrode (x = 0.75), compared with other electrodes, delivers excellent specific capacity and stability with the capacity retention of 74.4% after 5000 charging-discharging deep cycles at the current density of 2 A g−1 in 1.0 mol/L KOH aqueous electrolyte, and exhibits a Coulombic efficiency almost 100% after 5000 cycles. This phenomenon is attributed to a situation that Mo0.25W0.75Se2 active material has a quite different electronic band structure from the other remaining materials. It is therefore concluded that the combination reaction enables Mo1-xWxSe2 composite materials to realize their potential in electrochemical energy storage.