Folding Graphene Film Yields High Areal Energy Storage in Lithium-Ion Batteries

We show that a high energy density can be achieved in a practical manner with freestanding electrodes without using conductive carbon, binders, and current collectors. We made and used a folded graphene composite electrode designed for a high areal capacity anode. The traditional thick graphene composite electrode, such as made by filtering graphene oxide to create a thin film and reducing it such as through chemical or thermal methods, has sluggish reaction kinetics. Instead, we have made and tested a thin composite film electrode that was folded several times using a water-assisted method; it provides a continuous electron transport path in the fold regions and introduces more channels between the folded layers, which significantly enhances the electron/ion transport kinetics. A fold electrode consisting of SnO2/graphene with high areal loading of 5 mg cm–2 has a high areal capacity of 4.15 mAh cm–2, well above commercial graphite anodes (2.50–3.50 mAh cm–2), while the thickness is maintained as low as ...