NOVELTY - The apparatus comprises: a first electrode such as an anode (10) including an active material; a second electrode such as a cathode (14); and an electrolyte that is located between the anode and the cathode and includes magnesium ions, where the active material includes a binary combination of bismuth and tin having an atomic ratio of bismuth/tin of 1/99-99/1. The active material allows insertion and extraction of magnesium ions during operation of the battery through the formation of a magnesiated bismuth compound and a magnesiated tin compound.    USE - The apparatus such as a rechargeable magnesium-ion battery (claimed) is useful in an electrically-powered apparatus, a consumer electronic device, a medical device and an electric or hybrid vehicle.    ADVANTAGE - The apparatus has higher volumetric energy-densities.    DETAILED DESCRIPTION - The apparatus comprises: a first electrode such as an anode (10) including an active material; a second electrode such as a cathode (14); and an electrolyte that is located between the anode and the cathode and includes magnesium ions, where the active material includes a binary combination of bismuth and tin having an atomic ratio of bismuth/tin of 1/99-99/1. The active material allows insertion and extraction of magnesium ions during operation of the battery through the formation of a magnesiated bismuth compound and a magnesiated tin compound. The apparatus has a charged state and a discharged state. The apparatus further comprises: a housing supporting an anode terminal (12) electrically connected to the anode and a cathode terminal (16) electrically connected to the cathode; an anode support; and a cathode support. The anode terminal is electrically connected to the anode support. The cathode terminal is electrically connected to the cathode support. The housing provides an electrolyte seal. The anode terminal has an exterior surface and an interior surface. The cathode includes a cathode active material. The anode active material is formed directly on the interior surface of the anode terminal so that the anode terminal provides the anode support.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic sectional view of a magnesium-ion battery.    Anode (10)    Anode terminal (12)    Cathode (14)    Cathode terminal (16)    Insulating region. (22)