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

Abstract

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 SnO/graphene with high areal loading of 5 mg cm has a high areal capacity of 4.15 mAh cm, well above commercial graphite anodes (2.50-3.50 mAh cm), while the thickness is maintained as low as ∼20 μm. The fold electrode shows stable cycling over 500 cycles at 1.70 mA cm and improved rate capability compared to thick electrodes with the same mass loading but without folds. A full cell of fold electrode coupled with LiCoO cathode was assembled and delivered an areal capacity of 2.84 mAh cm after 300 cycles. This folding strategy can be extended to other electrode materials and rechargeable batteries.

Nickel‐Catalyzed Synthesis of 3D Edge‐Curled Graphene for High‐Performance Lithium‐Ion Batteries

“…The edge curl structure of 3D ECG not only effectively prevents the stacking and aggregation of graphene, but also forms a large number of stacked holes. These mesopores increase the contact area between the electrode and the electrolyte, shorten the diffusion distance of Li + and improve the rate performance . In addition, the edge‐curled structure also ensures the overall uniformity of the graphene sheets, which can effectively avoid the 3D ECG pulverization during repeated Li + insertion and removal.…”

“…However, there is still an obvious gap between the actual performance and theoretical performance of current graphene products. The main reason is that the strong π‐π interaction between the graphene sheets forces the graphene to tend to stack and aggregate during preparation and subsequent application . The thickness of stacked graphene is significantly increased and thus negatively affects various properties.…”

High‐Performance, Low‐Cost, and Dense‐Structure Electrodes with High Mass Loading for Lithium‐Ion Batteries

“…Generally, the thickness of conventional electrodes is limited to 100 µm, not only because the electrode's brittle behavior and weak adhesion to the current collector but also the poor kinetics caused by inhomogeneity, tortuous, and long ionic/electronic diffusion paths in the thick film. In addition, the high impedance from point contacts between individual particles in the electrodes is also a problem . Hence, new architectures and manufacture methods for LIBs are needed to develop electrodes with thickness > 100 µm and areal capacity > 3 mAh cm −2 corresponding to mass loading of ≈20 mg cm −2 for LiCoO 2 (LCO) and ≈10 mg cm −2 for graphite.…”

Flexible Graphene‐, Graphene‐Oxide‐, and Carbon‐Nanotube‐Based Supercapacitors and Batteries

“…Many electrode materials are used for the fabrication of flexible supercapacitors and batteries. Graphene‐ and carbon nanotube (CNT)–based materials attract much attention as potential energy‐storage platforms due to their inherent mechanical flexibilities . Conducting polymers, such as polypyrrole (PPy) and polyaniline (PANI), are particularly interesting electrode materials since they show relatively high capacitance toward supercapacitor and battery applications .…”