Rechargeable Silicon-Ion Batteries

Silicon (Si) is the second abundant material in nature and yet, despite its high abundance and ease of production, the possibility of using Si as an active multivalent rechargeable anode was never explored or reported. As a proof of concept, we will discuss in this talk a new rechargeable Si-ion cell, its design and architecture, enabling Si to be reversibly discharged at 1.1 V and charged at 1.5 V. Several discharge-charge cycles were achieved, utilizing heavy doped n-type Si wafer anodes, and hybrid based ionic liquid electrolytes. In addition, dissolved halides are functioning as conversion cathodes. Cell characterizations correlated the discharge and charge processes with the presence of dissolved fluoride and Si species in the electrolyte. The presence of appreciable fluoride species is crucial in both establishing surface activation and battery operation, and their depletion is directly linked to cell performance degradation. We will discuss Si ions deposition and dissolution mechanisms.