No abstract

A veritable magnesium-ion battery is described. Magnesium-ion can be reversibly extracted from MgMn2O4 and reversibly inserted into lambda-MnO2.

Calcium batteries could be an alternative to lithium analogues, but this technology is still in its infancy. It is previously known that layered-type molybdite (α-MoO 3 ) can intercalate hydrated calcium ions in aqueous electrolyte, and this intercalation process increases the interlayer spacing. In this work, we have found that α-MoO 3 is electrochemically active in calcium cell with nonaqueous electrolyte. The mechanism of intercalation has been explored by using XRD, Raman, and XPS. The layered structure of α-MoO 3 is preserved upon electrochemical intercalation of unsolvated calcium, and the perovskite-type structure of CaMoO 3 is not formed. The experimental length of the lattice parameter perpendicular to the slab increases from 13.85 to 14.07 Å in the first stages of intercalation. This limited increase can be optimum for achieving good electrochemical cycling. The model for calcium intercalation in the interlayer space was optimized by theoretical calculations based on the density functional theory. The resulting experimental reversible capacity is about 80−100 mA h g −1 , and the average voltage is ca. 1.3 V vs Ca. Further improvement of the electrolyte composition and particle size and morphology could render molybdite as a suitable electrode for rechargeable calcium batteries. The slow diffusion of calcium ion, the side-reactions, and the competing conversion reaction could be drawbacks, particularly at deep discharge and low voltages.

a Rechargeable batteries based on the intercalation of aluminium ions may be competitive against lithium-ion batteries, but their development and comprehension are full of difficulties. The charge/discharge processes are particularly complex in aqueous electrolyte solutions. The electrochemical behaviour of orthorhombic V2O5, obtained from xerogel, in aluminium cell is studied here by using electrochemical cycling, impedance spectroscopy, XRD and XPS results. After electrochemical intercalation of aluminium, the resulting (Al 3+ )x/3[(V 4+ )x,(V 5+ )2-x]O5.nH2O is XRD-amorphous at approximately x=1.5. The reversible capacity is ca. 120 mAh g -1 (equivalent to Al0.27V2O5). The loss of crystallinity induced by the electrochemical intercalation enhances the chemical exchange between the electrode material and the electrolyte solution. In the presence of acidic water solution, besides the faradic electrochemical process driven by the electrical current, aluminium, proton and water also can be intercalated into V2O5 by chemical reactions or ion exchange. Please do not adjust margins Please do not adjust margins redox activity in the voltage range between -1.3 and +0.5 V. In comparison with anatase, 2 the voltage of V 2 O 5 is higher, and discharge: solid symbols charge: open symbols (B)

No abstract