Impact of Aluminium Electrode Potential during Charging on Aluminium‐Ion Battery Performance with TEA‐AlCl3 Electrolyte

In aluminium (Al) symmetric cell, potentials during Al deposition on an Al foil at 1 mA cm−2 were 60–70 mV higher in TEA‐AlCl3 electrolyte compared to those measured with EMIMCl‐AlCl3 reference. Because of higher electrochemical stability of TEA‐AlCl3 solution, cut‐off voltage of charging step in AIB full‐cell was set to 2.45 V compared to 2.40 V for the reference cell. During long‐term cycling at 1 A g−1, the specific capacity of the AIB cell employing TEA‐AlCl3 increased from 60 to 94 mAh g−1 (57 %) after 1000 cycles while that of cell with EMIMCl‐AlCl3 was quite constant at about 60 mAh g−1. This behaviour was explained by continuous decreasing in Al electrode potential at End‐of‐Charge state (EOC) during deposition reaction (charging step) in TEA‐AlCl3 allowing an increase in graphite electrode potential and consequently in AIB cell capacity over the whole experiment. This increase in capacity was accompanied by a raise of defect sites in graphite material. The suitability of TEA‐AlCl3 electrolyte for Al‐graphite AIB is assessed by monitoring of electrode potentials during long‐term cycling at 1 A g−1. While Al electrode potential decreases continuously allowing steady increase of graphite electrode potential and cell capacity, those of AIB in 1.5 Emi remain constant.