A Bi-based artificial interphase to achieve ultra-long cycling life of Al-metal anode in non-aqueous electrolyte

Rechargeable aluminum-ion batteries (RAB) with Al-metal anode are regarded as cost-effective and environmentally sustainable energy storage systems. However, tapping the high volumetric capacity of the Al-anode has been a challenge because of the spontaneous and irreversible formation of the oxide layer on its surface that renders it electrochemically inactive. Though recently reported AlCl3-based electrolytes overcome this problem by breaking down this oxide layer, their highly corrosive nature hampers commercialization. Here, we investigate a novel approach to protect the Al-anode from severe oxidation by engineering an artificial protective interphase. A unique and less corrosive combination of Al(CF3SO3)3 salt and BiCl3 additive reacts with the Al-anode intrinsically to form an inorganic-rich protective bilayer. This layer is electronically insulating and significantly reduces the charge transfer resistance and surface activation energy at the anode, enabling plating/stripping at extremely low overpotential of <0.1 V that can be sustained for record-long cycling times of >4000 h.