Microwave-Reduced Graphene Oxide for Aluminum Batteries

Recently, rechargeable graphene-based aluminum-ion batteries (AIBs) as an attractive energy storage system has been studied. Owing to the requirements such as high conductivity and low defects, the graphene cathode used in AIBs is typically fabricated using chemical vapor deposition (CVD). Here, we utilize solution-processable microwave-reduced graphene oxide (MWrGO) that has been shown to be of very high quality with low defect density as a cathode in AIBs. Our results show that it is possible to increase the AlCl₄^-ion storage with MWrGO, relative to thermally reduced graphene oxide (TrGO). The MWrGO film cathode for AIBs shows a stable discharge capacity of 87.7 mA h g^-1at 0.2 A g^-1with a coulombic efficiency of >93% and favorable rate capability that can withstand more than 4500 cycles without capacity decay at a high current density of 2 A g^-1. The relationship between AlCl₄^-ion storage capability and microwave time has been examined to elucidate the fundamental relationship between AlCl₄^-intercalation and defects in graphene. We found that improved quality and lowered defects lead to higher diffusion-controlled contribution arising from the faradaic redox reaction, also leading to increased AlCl₄^-ion storage capability, whereas higher defects of graphene result in increased electrical double-layer capacity contribution but reduced AlCl₄^-ion storage capability.