Rechargeable Aqueous Aluminum Organic Batteries

Aqueous aluminum-ion batteries (AABs) are regarded as promising next-generation energy storage devices, and the current reported cathodes for AABs mainly focused on inorganic materials which usually implement a typical Al³⁺ ions (de)insertion mechanism. However, the strong electrostatic forces between Al³⁺ and the host materials usually lead to sluggish kinetics, poor reversibility and inferior cycling stability. Herein, we employ an organic compound with redox-active moieties, phenazine (PZ), as the cathode material in AABs. Different from conventional inorganic materials confined by limited lattice spacing and rigid structure, the flexible organic molecules allow a large-size Al-complex co-intercalation through reversible redox active centers (-C=N-) of PZ. This co-intercalation behavior can effectively reduce desolvation penalty, and substantially lower the Coulombic repulsion during the ion (de)insertion process. Consequently, this organic cathode exhibits a high capacity and excellent cyclability, which exceeds those of most reported electrode materials for AABs. This work highlights the anion co-intercalation chemistry of redox-active organic materials, which is expected to boost the development of high-performance multivalent-ion battery systems.