Microwave-Reduced\nGraphene Oxide for Aluminum Batteries

Abstract

Recently, rechargeable graphene-based aluminum-ion batteries\n(AIBs)\nas an attractive energy storage system has been studied. Owing to\nthe requirements such as high conductivity and low defects, the graphene\ncathode used in AIBs is typically fabricated using chemical vapor\ndeposition (CVD). Here, we utilize solution-processable microwave-reduced\ngraphene oxide (MWrGO) that has been shown to be of very high quality\nwith low defect density as a cathode in AIBs. Our results show that\nit is possible to increase the AlCl₄^– ion storage with MWrGO, relative to thermally reduced graphene oxide\n(TrGO). The MWrGO film cathode for AIBs shows a stable discharge capacity\nof 87.7 mA h g^–1 at 0.2 A g^–1 with\na coulombic efficiency of >93% and favorable rate capability that\ncan withstand more than 4500 cycles without capacity decay at a high\ncurrent density of 2 A g^–1. The relationship between\nAlCl₄^– ion storage capability and microwave\ntime has been examined to elucidate the fundamental relationship between\nAlCl₄^– intercalation and defects in graphene.\nWe found that improved quality and lowered defects lead to higher\ndiffusion-controlled contribution arising from the faradaic redox\nreaction, also leading to increased AlCl₄^– ion storage capability, whereas higher defects of graphene result\nin increased electrical double-layer capacity contribution but reduced\nAlCl₄^– ion storage capability.