New cathode materials for rechargeable Mg batteries: Fast Mg ion transport and reversible copper extrusion in Cu_yMo₆S₈ compounds

We report on a discovery of fast cathode materials, ternary Chevrel phases (CPs), Cu_yMo₆S₈, for rechargeable magnesium batteries; the related electrochemical process displays a unique coupling between reversible Mg insertion, and Cu extrusion/reinsertion; this coupling results in an entirely new intercalation mechanism which combines the total chemical reversibility of the electrochemical reaction of Mg_xCu _yMo₆S₈ with irreversibility of its separate stages once Cu extrusion stage is reached (in Mg_xCu _yMo₆S₈: 0.5x + y > 4).