Rechargeable aqueous aluminum-FeFe(CN)6 battery with artificial interphase through deep eutectic solution

The application needs of small electronic devices and large-scale power grid storage continuously promote the development of a new battery energy system. Rechargeable metal batteries based on aluminum (Al) are of enormous potential due to the abundant Al reserves, the trivalent charge carrier, high theoretical specific capacity (2980 mAh/g), and volumetric energy density (8046 mAh/cm3). However, the passivating oxide layer on the surface of the Al anode blocks the migration of electrons and ions, resulting in the operation difficulty and irreversibility of aluminum-based batteries. Herein we treated Al anode with a deep eutectic solution (DES) and constructed stable solid interface interphase on its surface, which can effectively prevent surface passivation, improve the chemical properties of the interface, promote ion transfer, and enable aqueous Al batteries with superior electrochemical performance. The assembled symmetric cells with treat Al (TAl) can cycle for more than 300 h with a low overpotential (~0.2 V). The TAl anode coupling with the FPB cathode material to assemble the full cells based on the aqueous electrolyte system can deliver a high discharge capacity of 85 mAh/g and exhibit capacity retention of 58 mAh/g after 150 cycles and an average coulombic efficiency of 97.1% at a current density of 100 mA/g. This work provides a novel surface modification strategy of Al metal anode and demonstrates high stability and cost-effective aqueous Al metal battery system, which suggest the significance for the commercialization of Al-metal batteries and their applications in large-scale energy store.