The Effects of Anions Behaviors on Electrochemical Properties of Al/Graphite Rechargeable Aluminum-Ion Battery via Molten AlCl3-NaCl Liquid Electrolyte

The need of an efficient and sustainable way to store energy is an urgent necessity. Unfortunately, due to the cost and limited resources of lithium, the use of the most mature Li-ion batteries for grid-scale storage of renewable energy production is nowadays going on slowly. Here, a low-cost, high-capacity Al/graphite rechargeable aluminum battery was explored based on molten AlCl3-NaCl liquid electrolyte. The battery shows a specific capacity of above 200 mAh g−1 at a current density of 100 mA g−1, even maintaining at 111.4 mAh g−1 at a higher current density of 1000 mA g−1 over 1000 cycles, with a Coulombic efficiency of 94.6%. Raman spectroscopy and X-ray photoelectron spectroscopy reveal that AlCl4− and Al2Cl7− anions are intercalated between graphite layers at the graphitic carbon cathode, meanwhile Al2Cl7− anions are transformed into metallic Al and AlCl4− anions at the Al anode. The inherent low-cost and low-flammability, as well as the most outstanding high capacity, long-term cycling stability and Coulombic efficiency, are particularly favorable for grid-scale storage of renewable energy.