Understanding the deposition of Mg and intercalation of Mg2+ for future Mg-ion batteries

Magnesium-Ion Batteries;Polyoxometalate;Electrochemistry

Miller, Elizabeth Carol

关键词: Magnesium-Ion Batteries;    Polyoxometalate;    Electrochemistry;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/78484/MILLER-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In efforts to decrease the world’s dependence on fossil fuels, renewable energy sources and storage are being actively sought, especially in the transportation sector. The electrification of vehicles hinges on the low cost, safety, and volumetric capacity of its energy storage devices, namely batteries. Currently, Li-ion batteries are used in commercial electric vehicles; however, these have limited capacities compared to metal anode batteries. Herein, this work describes the methods and advancements in understanding and developing Mg batteries, as an alternative to Li-ion batteries. Theoretically, Mg batteries have far superior volumetric capacities (3833 mAhcm-3 Mg vs. 760 mAhcm-3 graphite). Mg is a more earth abundant (13.9% Mg in earth’s crust compared to 7x10-4 % Li) and a less expensive alternative to Li ($2700/ton Mg and $64000/ton Li). In Chapter 1, polyoxometalates are electrochemically characterized as a possible cathode material for Mg-ion batteries. Phosphomolybdic acid is used a proof of concept material, showing reversible redox chemistry in a variety of nonaqueous electrolyte systems. Efforts are described to reduce dissolution with polymer binders and how the redox chemistry changes with cationic salts. In Chapter 2, the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex is described. The results define the requirements for reversible behavior with ~100% Coulombic efficiencies. Voltammetric cycling alters the composition and the performance of the electrolyte. The electrolyte has no shelf life, and oligomers form due to the ring-opening polymerization of the THF solvent. From these results, a mechanism is proposed describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.