Abstracts Category : Other

Reversible Electrochemical Intercalation of Aluminum in Transition Metal Sulfides

by Linxiao Geng

Rechargeable battery technology has been one of the most exciting advancements in science and technology in the last several decades. Even though lithium ion battery technology has achieved great success in many fields, its wide deployment for large-scale energy storage is very questionable because of the limited resources of lithium. Therefore, alternative rechargeable battery technologies based on abundant elements need to be developed for sustainable electrochemical energy storage. Among all the potential candidates, battery systems based on aluminum as anode is particularly promising. In this thesis, we are dedicated to develop novel rechargeable Al-ion battery prototypes mainly focusing on cathode materials. Our achievement of discovering transition metal sulfides as promising cathode materials for rechargeable Al-ion batteries is pioneering. We first proposed Chevrel Phase Mo6S8 as intercalation-type cathode material for rechargeable Al-ion battery using ionic liquid electrolyte. We investigated the electrochemical properties as well as compositional properties of Chevrel Phase Mo6S8 as a cathode material. We believe it is the first reported intercalation-type rechargeable Al-ion battery prototype. We went further to probe the detailed intercalation process of Al3+ in Chevrel phase Mo6S8. High quality powder XRD data along with Rietveld refinements give a clear picture of the aluminum intercalation induced phase transition process of Mo6S8. High resolution TEM further provided strong evidence of Al3+ intercalation and phase transition of Mo6S8. In light of the information gained from the Al3+ intercalation and deintercalation process, constant-current-constant-voltage charge and galvanostatic discharge technique was used to improve the cycling performance of Mo6S8. A 50% capacity increase was obtained with a high current density of 40 mA g-1. At last, we extended our cathode materials screening on other transition metal sulfides base on the previous results. We presented layered TiS2 and cubic Cu0.31Ti2S4 to be potential cathode materials for rechargeable Al-ion batteries. Layered TiS2 showed better electrochemical performance than Cubic Cu0.31Ti2S4. Moreover, we also demonstrated that the slow diffusion of Al3+ in the titanium sulfides crystal structure is the main obstacle to achieving high Al intercalation capacity through GITT analysis.