Widely commercial carbonaceous materials as cathode for Al-ion batteries

Recently, the scientific interest in developing rechargeable aluminium-ion (Al-ion) batteries has increased, triggered by its theoretical capacity, low cost and low reactivity of aluminium metal. One of the main challenges is the development of cathode materials that reversibly intercalate AlCl4− in its structure. The most promising candidates are carbonaceous materials of very different nature. However, no systematic analysis has been performed so far to investigate the intrinsic parameters that determine their electrochemical performance. Here, different commercial available carbons such as pyrolytic graphite (PG), expanded graphite (EG), synthetic graphitic flakes (SGF) and two different carbon papers (H23C3 and H23I1) are systematically evaluated as cathodes in Al-ion batteries. The influence of their graphitic degree, particle size, porosity and mass loading on the battery performance is elucidated. Electrochemical tests combined with ex situ XRD demonstrated that only highly graphitic materials can intercalate AlCl4− obtaining a good battery performance. Synthetic graphite flakes (SGF) showed the best specific capacity (85 mAh g−1), rate capability and cycle life (>1600 cycles) due to the fast diffusion of the AlCl4− through its structure. Finally, high mass loading cathodes (SGF-HML) showed extraordinary areal capacity (5.6 mAh cm−2), almost doubling the high energy cathodes for Li-ion batteries (3 mAh cm−2).