Fe-Co PBA/rGO interface strategy enabling fast Al3+ intercalation for stable aqueous Al-ion batteries

Aqueous aluminum-ion batteries (AAIBs) have emerged as cost-effective and safe alternatives to lithium-ion batteries for storing energy. However, utilizing cathode materials like Prussian blue analogs (PBAs) to accommodate different metallic charge carriers faces challenges due to their low conductivity and slow redox kinetics. To overcome these issues, we propose a novel Fe-Co PBA/rGO nanocomposite with a strong interfacial chemical coupling between Fe-Co PBA and rGO. By combining theoretical calculations with experimental analysis, we have identified the essential role of interfacial interactions in regulating the electronic state and diffusion barriers of Al3+ within the Fe-Co PBA framework. Moreover, a three-dimensional structure that is tightly enclosed by ultrathin rGO sheets was successfully formed, ensuring excellent structural stability. Ex-situ XPS and XRD investigations have further clarified the electrochemical mechanism of the Fe-Co PBA/rGO cathode, revealing reversible redox reactions between Fe2+/Fe3+ and Co3+/Co2+ states during the insertion and extraction of Al3+. These inherent properties contribute to the remarkable cycling stability of the Fe-Co PBA/rGO cathode, achieving 66.7 mAh/g at 1 A/g after 1500 cycles, and high electrochemical reversibility. Additionally, we have successfully built a MoO3//Fe-Co PBA/rGO full battery with a capacity of 53.6 mAh/g over 2000 cycles at 1 A/g. This outcome further emphasizes its significant potential in electronic applications related to energy storage.