Toward Practical Aluminum Organic Batteries Featuring Covalent Organic Framework

Abstract

In recent years, Al metal organic batteries have attracted significant interest due to their promise of sustainability and high volumetric energy densities, while being based on abundant materials. However, many studies assess their performance with insufficient rigor, often emphasizing high capacity and power performance, as well as cycling stability at very high cycling rates. Herein, the feasibility of a highly stable β-ketoenamine-linked anthraquinone-based covalent organic framework (DAAQ-TFP-COF) for rechargeable Al batteries is reassessed. First, the influence of different voltage windows on electrochemical behavior in an ionic liquid electrolyte, identifying an optimal balance between capacity and stability, is investigated. Within the optimized voltage window of 0.5 to 2.0 V, DAAQ-TFP-COF achieves a capacity of 113.9 mAh g⁻¹ at 50 mA g⁻¹. To gain deeper insight into the charge storage mechanism, surface- and bulk-sensitive characterization techniques—energy-dispersive X-ray spectroscopy and X-ray Raman spectroscopy—confirming monovalent AlCl₂⁺ as the main coordination species are employed. Finally, the compatibility of DAAQ-TFP-COF with more cost-effective amide-based Al electrolytes is evaluated. In butyramide-based electrolyte, the organic material exhibits stable performance and high Coulombic efficiency. Based on our findings, a realistic outlook on the key challenges that must be addressed to advance COF-based electrodes for future aluminum battery applications is provided.