Enabling Reversible (De-)lithiation of Aluminum via the Use of Bis(fluorosulfonyl)imide-based Electrolytes.

Aluminum, a cost-effective and abundant metal capable of alloying with Li up to ~1000 mAh/g, is a very appealing anode material for high energy density lithium ion batteries (LIBs). However, despite the repeated efforts in the past three decades, reports presenting stable cycling performance are extremely rare. In this letter, we report our recent findings on the highly reversible (de-)lithiation of micro-sized Al anode (m-Al) enabled by the use of bis(fluorosulfonyl)imide (FSI)-based electrolytes. Using this kind of electrolytes, m-Al can deliver a specific capacity over 900 mAh/g and superior Coulombic efficiency (96.8%) compared to traditional carbonate- and glyme-based electrolytes (87.8% and 88.1%, respectively), which is the best performance ever obtained for Al anode without sophisticated structure design. The significantly improved electrochemical performance, paving the way to realize high performance Al-based high energy density LIBs, lies in peculiar solid electrolyte interface (SEI) formed by the FSI-containing electrolyte.