Elucidation of Electrochemical Performance of Few-Layered Graphene As Aluminium Battery Cathode Material: Effect of the Common O and S Impurities

Abstract

Of late, few-layered graphene (FLG) is being tested as an efficient aluminum battery (AB) cathode material. FLG is typically prepared by reducing and exfoliating graphene oxide (GO), commonly prepared by wet-chemical methods. Therefore, FLG is bound to have impurities (commonly O and S). Consequently, it is crucial to study the influence of the S and O impurities in FLG on its performance as an AB cathode material. To conduct such a study, we considered FLG prepared by exfoliating GO using microwave irradiation. The considered FLG has O and S impurities (bonded to C atoms in FLG), collectively weighing 2.9 – 4.7 at.% (4.1 – 6.9 wt.%). The considered FLG as a cathode material in AB pouches delivered stable discharge capacities of around 100 mAh/g at 0.1 A/g current rate over 500 cycles and high irreversible capacities for the first few cycles. The effect of the O and S impurities was negligible when the FLG was cycled at 1.0 A/g, but initial energy storage capacities and cyclic behavior varied with the voltage window. However, the storage capacities at the end of 10000 cycles are similar, irrespective of the voltage window. Overall, the O and S impurities in FLG lead to initial high irreversible capacities, ruling out the commercial use of FLG. We therefore recommend careful characterization of O and S impurities (and any such impurities) before reporting FLG-related materials as AB cathode materials. Removing these impurities will help FLG outperform its class of materials because it shows excellent rate capability with excellent discharge capacities at a high current density of 5 A/g, even with O and S impurities.