Synthesis of Post-Spinel Compounds for Calcium Ion Battery Cathodes

Rechargeable batteries, which currently rely on lithium ion technology. are widely employed in electric vehicles and phones. As demand for rechargeable batteries grows, calcium ion batteries represent a potential replacement for Li-ion batteries as concerns grow regarding the price, availability, and environmental impact of Li-ion technology. Ca-ion batteries have potential applications in supporting intermittent renewable energy sources such as wind and solar power. Calcium has advantages over lithium because of its relatively high abundance which mitigates the scarcity and high cost issues surrounding lithium. Additionally, calcium is more sustainable and has less of an environmental impact. In terms of battery performance, calcium and lithium have a similar volumetric capacity and the divalent nature of calcium promises a potentially greater energy density. Commercial scale production of Ca-ion batteries has been prohibited by a lack of suitable cathode materials. Calcium oxides in the post-spinel phase are of interest for cathode materials owing to their probable high ionic mobility. DFT calculations indicate a theoretically low energy barrier for Ca-ion migration in the post-spinel structure. Three post-spinel compounds, CaFe₂O₄, CaMn₂O₄, and CaCo₂O₄, were synthesized using varying methods. X-ray diffraction results indicate a high purity of the post-spinel phase in each synthesized compound compared to commercially available materials. Future work includes the processing of the synthesized post-spinel compounds into electrodes and evaluating their redox activity with electrochemical testing.