Crystalline Transition Metal Cathode Materials for Rechargeable Aluminum Batteries

Department of Chemical Engineering, The City College of New York;

160 Convent Avenue, New York, NY 10031

Title: Crystalline Transition Metal Cathode Materials for Rechargeable Aluminum Batteries

The expanding use of electric vehicles and grid-scale storage of renewable energy sources requires novel electrical energy storage systems. Lithium-ion batteries have dominated the portable electronics market; however, rechargeable aluminum batteries have several advantages over lithium-based batteries. Trivalent aluminum ions can transfer three electrons each upon Faradaic reaction, yielding almost three times the volumetric capacity compared to Lithium ions. Aluminum is also the most abundant metal in the Earth’s crust and consequently has a low cost. However, one of the outstanding challenges lies in the limited number of cathode materials that are known to reversibly intercalate trivalent aluminum ions.

This work highlights two crystalline transition metal oxide and sulfide structures as intercalation cathode materials for rechargeable aluminum-ion batteries: the spinel-phase Mn₂O₄ and the chevrel-phase Mo₆S₈. Best practices for synthesizing pure spinel and chevrel phases will be discussed, as well as how to incorporate them into composite cathodes. Electrochemical analyses of the cathode materials, using cyclic voltammetry (CV) and galvanostatic cycling, will be presented and analyzed in detail. X-ray diffraction (XRD), scanning electron microscopy (SEM), and ²⁷Al magic-angle-spinning (MAS) solid-state NMR measurements yield insight into the intercalation mechanisms and the molecular and structural changes that the materials undergo upon electrochemical cycling. The results yield insights into the challenges and opportunities of designing crystalline intercalation cathode for rechargeable aluminum batteries.