Graphite/copper phthalocyanine composite cathode for overcharge protection and gas evolution suppression in aluminum-ion batteries at room temperature

A rechargeable aluminum-graphite battery based on the conventional AlCl₃−[EMIm]Cl ionic liquid electrolyte exhibits excellent electrochemical performance, but the relatively narrow electrochemical window (1–2.45 V vs. Al/Al³⁺) at room temperature. Therefore, overcharge and safety hazards could limit the operation of such batteries. In this study, the authors proposed the addition of organic compounds to the graphite cathode to improve protection when the battery is overcharged. In particular, copper phthalocyanine (CuPc) and natural graphite flakes were combined to form a novel cathode material that effectively increases the working potential window up to 2.82 V (vs. Al/Al³⁺). In the conventional graphite cathode, the specific capacity was reduced by 66.7% after 200 charge/discharge cycles in the range of 1–2.82 V, accompanied by obvious pouch swelling. After the addition of CuPc to the graphite cathode, no significant capacity degradation (less than 10%) was observed after 200 cycles, and the specific capacity decay was below ∼25% for the first 1000 cycles. Notably, the swelling phenomenon did not occur after 1000 charging/discharging cycles when the CuPc/graphite composite cathode was used.