Structure-Performance relationship guided design and strategic synthesis of lithiated oxa-graphene for high lithium storage.

Graphene derivative materials are widely used as anode component in lithium-ion batteries. However, there is still a lack of reliable and foresighted guides helpful for designing high-performance graphene-based electrode materials. To this end, we strategically chose challenging graphite fluoride as starting material for the derivatization of graphene in order to exclude interference factors. As a result, graphene framework was functionalized with oxygen-containing carboxylate and sulfonate groups and oxygen-free aniline units at a similar functionalization degree. Due to the strong effect of lithiation, out-of-plane p-aminobenzoic acid blocks boosted the lithium-storage capacity of graphene matrix to 636 mAh g-1 at 0.1 A/g, and sulfanilic acid blocks maximized this value to 873 mAh g-1. Sadly, oxygen-free aniline functionalized graphene material only delivered a specific capacity of 88 mAh g-1. Meanwhile, spatial lithiated carboxylate and sulfonate units endowed graphene framework with better rate capability and cycling stability. Such a structure-performance relationship established herein was beneficial for the design and preparation of high-performance graphene derivative electrode materials.

High-energy-density flexible graphene-based supercapacitors enabled by atypical hydroquinone dimethyl ether.

Supercapacitor is an electrochemical energy-storage technology that can meet the green and sustainable energy needs of the future. However, a low energy density was a bottleneck that limited its practical application. To overcome this, we developed a heterojunction system composed of two-dimensional (2D) graphene and hydroquinone dimethyl ether- an atypical redox-active aromatic ether. This heterojunction displayed a large specific capacitance (Cs) of 523 F g-1 at 1.0 A g-1, as well as good rate capability and cycling stability. When assembled in symmetric and asymmetric two-electrode configuration, respectively, supercapacitors can work in voltage windows of 0 âˆ¼ 1.0 V and 0 âˆ¼ 1.6 V, accordingly, and exhibited attractive capacitive characteristics. The best device can deliver an energy density of 32.4 Wh Kg-1 and a power density of 8000 W Kg-1, and suffered a small capacitance degradation. Additionally, the device showed low self-discharge and leakage current behaviors during long time. This strategy may inspire exploration of aromatic ether electrochemistry and pave a way to develop electrical double-layer capacitance (EDLC)/pseudocapacitance heterojunctions to boost the critical energy density.

High-performance reduced graphene oxide supercapacitors enabled by simple amino hydroquinone dimethylether.

Reduced graphene oxide (rGO) supercapacitors usually feature poor capacitive characteristics. In the current work, coupling of the simple, nonclassical redox molecule amino hydroquinone dimethylether with rGO was found to boost the rGO capacitance to 523 F g-1. The assembled device exhibited an energy density of 143 Wh kg-1 and excellent rate capability and cyclability.

Ultrasimple air-annealed pure graphene oxide film for high-performance supercapacitors.

Realizing both high gravimetric and volumetric specific capacitances (noted as CW and CV, respectively) is an essential prerequisite for the next-generation, high performance supercapacitors. However, the need of electronic/ionic transport for electrochemical reactions causes a "trade-off" between compacted density and capacitance of electrode, thereby impairing gravimetric or volumetric specific capacitances. Herein, we report a high-performance, film-based supercapacitor via a thermal reduction of graphene oxide (GO) in air. The reduced, layer-structured graphene film ensures high electrode density and high electron conductivity, while the hierarchical channels generated from reduction-induced gas releasing process offer sufficient ion transport pathways. Note that the resultant graphene film is employed directly as electrodes without using any additives (binders and conductive agents). As expected, the as-prepared electrodes perform particularly well in both CW (420F g-1) and CV (360F cm-3) at a current density of 0.5 A g-1. Even at an ultrahigh current density of 50 A g-1, CW and CV maintain in 220F g-1 and 189F cm-3, respectively. Furthermore, the corresponding symmetric two-electrode supercapacitor achieves both high gravimetric energy density of 54 W h kg-1 and high gravimetric power density of 1080 W kg-1, corresponding to volumetric energy density of 46 W h L-1 and volumetric power density of 917 W L-1.