Thermodynamic calculation on energy densities of multi-electron transfer Mg/Al batteries

Magnesium (Mg) ion batteries and aluminum (Al) ion batteries have become new hot spots in beyond lithium ion batteries due to their high energy densities, abundant reserves as well as safety. In this work, the theoretical gravimetric energy densities (GED), volumetric energy densities (VED) and output voltage (OV) of nearly 300 electrochemical couples of Mg/Al ion batteries are calculated by thermodynamic method. As our evaluation, considering of gravimetric energy density, volumetric energy density, output voltage, toxicity, corrosion, flammability and environmental friendliness and so on, a series of materials are screened out as promising candidates including Mg ion cathodes (O₂, S, MnO₂, MoO₃, Fe₂O₃, Fe₃O₄, NiO, MoO₂, CuO and Cu₂O) and Al ion cathodes (O₂, S, MnO₂, MoO₃, NiO, CuO and Cu₂O).