Molecular Tailoring Modulates Coordination of Deep Eutectic Electrolytes for Dendrite-Free Rechargeable Aluminum Batteries
Rechargeable aluminum batteries (RABs) are promising for large-scale energy storage due to high theoretical capacity, inherent safety, and abundant aluminum reserves. However, conventional AlCl3-based ionic liquid electrolytes suffer from high cost, uncontrolled dendrite growth, and severe anode corrosion. Here, a molecular-level ligand engineering strategy is proposed, employing nitrogen-containing cyclic amides with tunable N–H functionalities to modulate the coordination environment of deep eutectic electrolytes (DEEs). Combined experimental and theoretical investigations reveal that the α-pyrrolidone-based DEE (PDEE) possesses a wider electrochemical window, higher ionic conductivity, and lower polarization. Precise N–H regulation optimizes cationic ligand and chloroaluminate anion interactions, accelerating ion transport to facilitate uniform Al deposition without dendrites. The amine functionalities enable in situ construction of a uniform inorganic-organic bilayer solid electrolyte interphase, mitigating anode corrosion and enhancing long-term interfacial stability. As a result, Al//Al symmetric batteries with PDEE achieve stable cycling for over 2000 hours, while Al-graphite full batteries demonstrate negligible capacity decay after 6000 cycles. This study establishes that ligand molecular engineering offers an effective strategy for optimizing DEEs, enabling durable and high-performance RABs.