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Graphene hydrogel/nickel foam composite electrodes for high-rate electrochemical capacitors are produced by reduction of an aqueous dispersion of graphene oxide in a nickel foam (upper half of figure). The micropores of the hydrogel are exposed to the electrolyte so that ions can enter and form electrochemical double-layers. The nickel framework shortens the distances of charge transfer. Therefore, the electrochemical capacitor exhibits highrate performance (see plots).

An improved hydrothermal process is developed to fabricate macroporous graphene monoliths (MGMs) using a soft template of organic droplets. The MGMs are constructed from closed-cell distorted spherical pores. This unique microstructure makes MGMs that have low weight densities, good electrical conductivities, and excellent elasticity with rapid recovery rates.

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Electrochemical capacitors (ECs) have been widely applied in electronics, electric vehicles, aircrafts, energy storage devices, uninterrupted or emergency power supplies, and so on. An ideal EC should have high energy and/or powder density, good rate capability, and long cycling life. Recently, graphene, graphene derivatives, and their composites have been explored as the electrode materials of ECs to satisfy these requirements. In this Perspective, we review the recent development in synthesizing graphene materials for ECs and discuss the strategies of fabricating graphene-based macroscopic electrodes. Particularly, we highlight the importance of the specific surface area, conductivity, and heteroatom-doping of graphene sheets and the micro/nanostructures of their electrodes for controlling the performances of graphene-based ECs.

Freestanding, paper-like films of reduced graphene oxide (rGO) containing trace amounts of polymers are fabricated by an operationally simple, cost-effective, and environmentally friendly gel-film approach. The films, which can have a large area, display ultrahigh strengths and toughnesses as well as high electrical conductivities.

Engineering a stable solid electrolyte interphase (SEI) is critical for suppression of lithium dendrites. However, the formation of a desired SEI by formulating electrolyte composition is very difficult due to complex electrochemical reduction reactions. Here, instead of trial-anderror of electrolyte composition, we design a Li-11 wt % Sr alloy anode to form a SrF 2 -rich SEI in fluorinated electrolytes. Density functional theory (DFT) calculation and experimental characterization demonstrate that a SrF 2 -rich SEI has a large interfacial energy with Li metal and a high mechanical strength, which can effectively suppress the Li dendrite growth by simultaneously promoting the lateral growth of deposited Li metal and the SEI stability. The Li−Sr/Cu cells in 2 M LiFSI-DME show an outstanding Li plating/stripping Coulombic efficiency of 99.42% at 1 mA cm −2 with a capacity of 1 mAh cm −2 and 98.95% at 3 mA cm −2 with a capacity of 2 mAh cm −2 , respectively. The symmetric Li−Sr/Li−Sr cells also achieve a stable electrochemical performance of 180 cycles at an extremely high current density of 30 mA cm −2 with a capacity of 1 mAh cm −2 . When paired with LiFePO 4 (LFP) and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes, Li−Sr/LFP cells in 2 M LiFSI-DME electrolytes and Li−Sr/NMC811 cells in 1 M LiPF 6 in FEC:FEMC:HFE electrolytes also maintain excellent capacity retention. Designing SEIs by regulating Li-metal anode composition opens up a new and rational avenue to suppress Li dendrites.

Base-induced graphene oxide (GO) liquid crystals form a highly ordered texture. This microstructure can be inherited by graphene foams prepared by hydrothermal reduction, showing a long-range ordered microstructure of graphene sheets in 3D. This provides an insightful understanding into the supramolecular chemistry of GO sheets.