Effect of ion size and charge density on the electrochemical characteristics of α-MoO3 using aqueous Be2+ and Mg2+ sulfate electrolytes

We investigated the electrochemical characteristics of layer structured α-MoO3 using two divalent ions (Mg2+ and Be2+) of different sizes. The cyclic voltammetry studies showed a high specific capacity with Be2+ electrolyte, and galvanostatic intermittent titration (GITT) measurements revealed a higher diffusion coefficient for Be2+ in MoO3 despite having a higher charge density than Mg2+. The intercalation of both ions resulted in poor cyclability, but a slightly better performance with Be2+ electrolyte could be attributed to favored diffusion of Be2+ in MoO3 due to its covalent nature as well as preferred coordination number.