Reversible and rapid calcium intercalation into molybdenum vanadium oxides

Title	Reversible and rapid calcium intercalation into molybdenum vanadium oxides
Authors	Aniruddha S. Lakhnot, Kevin Bhimani, Varad Mahajani, Reena A. Panchal, Shyam Sharma, Nikhil Koratkar
Magazine	Proceedings of the National Academy of Sciences of the United States of America
Date	07/21/2022
DOI	10.1073/pnas.2205762119
Introduction	The sustained utilisation of lithium in energy storage applications faces challenges due to issues of scarcity, high costs, and safety. Calcium presents an attractive alternative for battery systems given its abundance and affordability. However, the larger ionic radius and higher charge density of calcium ions, compared to lithium, typically hinder diffusion kinetics and reduce cyclic stability. This research presents an aqueous calcium-ion battery employing orthorhombic, trigonal, and tetragonal polymorphs of molybdenum vanadium oxide (MoVO) as suitable hosts for calcium ions. The orthorhombic and trigonal MoVO structures exhibit enhanced performance compared to the tetragonal form. This capability is attributed to the extensive hexagonal and heptagonal tunnels within their crystal structures, which facilitate efficient calcium-ion transport. Specifically, trigonal MoVO achieved a specific capacity of approximately 203 mAh g⁻¹ at a 0.2C rate, and maintained a capacity of about 60 mAh g⁻¹ even at a significantly faster rate of 20C. Furthermore, these open-tunnel trigonal and orthorhombic polymorphs contributed to improved cyclic stability and reversibility. Current literature suggests that MoVO demonstrates one of the leading performances reported thus far for calcium-ion storage.
Quote	Aniruddha S. Lakhnot, Kevin Bhimani and Varad Mahajani et al. Reversible and rapid calcium intercalation into molybdenum vanadium oxides. Proceedings of the National Academy of Sciences of the United States of America. 2022. Vol. 119(30). DOI: 10.1073/pnas.2205762119
Element	Calcium (Ca) , Lithium (Li) , Molybdenum (Mo) , Vanadium (V) , Oxygen (O)
Materials	Crystals
Industry	Energy Storage & Batteries , Research & Laboratory