Unlocking an Aluminum Anode in the Nonaqueous Electrolyte: Electrodeposition Kinetics, Electrolyte Engineering, and Electrode Modification

To meet the escalating energy density demands of next-generation energy storage systems, new battery materials and electrochemical mechanisms are required to surpass the limitations of conventional intercalation-based Li-ion batteries. Although the aluminum metal anode, with the highest volumetric capacity (8046 mA h cm –3 ) and a gravimetric capacity (2980 mA h g –1 ) second only to lithium, as well as unparalleled abundance in the earth’s crust and inherent safety, holds immense promise for nonaqueous aluminum-ion batteries (AIBs), the practical application of Al anodes continues to face challenges: inhomogeneous electrodeposition, interface instability, and dendrite-induced safety risks. In this review, we systematically summarize the characteristics and anode reactions in four nonaqueous electrolyte systems (an ionic liquid, a deep eutectic solvent, molten salt, and quasi-solid-state electrolytes). By thoroughly examining the four critical kinetic processes in the Al anode reaction: mass transport, charge transfer reaction, nucleation, and crystallographic growth, we reveal the limiting factors for the trivalent Al 3+ anode reactions by comparing them with monovalent (Li +, Na + ) and divalent (Mg 2+, Ca 2+, and Zn 2+ ) metal anodes. Based on recent advancements and insights into electrolyte modifications and electrode engineering for Al anodes in nonaqueous electrolytes, this review also addresses several promising application areas, challenges, and directions for future research in AIBs.