Efficient Fabrication of Disordered Graphene with Improved Ion Accessibility, Ion Conductivity, and Density for High-Performance Compact Capacitive Energy Storage.

High-performance compact capacitive energy storage is vital for many modern application fields, including grid power buffers, electric vehicles, and portable electronics. However, achieving exceptional volumetric performance in supercapacitors is still challenging and requires effective fabrication of electrode films with high ion-accessible surface area and fast ion diffusion capability while simultaneously maintaining high density. Herein, a facile, efficient, and scalable method is developed for the fabrication of dense, porous, and disordered graphene through spark-induced disorderly opening of graphene stacks combined with mechanical compression. The obtained disordered graphene achieves a high density of 1.18 g cm-3, sixfold enhanced ion conductivity compared to common laminar graphene, and an ultrahigh volumetric capacitance of 297 F cm-3 in ionic liquid electrolyte. The fabricated stack cells deliver a volumetric energy density of 94.2 Wh L-1 and a power density of 13.7 kW L-1, representing a critical breakthrough in capacitive energy storage. Moreover, the proposed disordered graphene electrodes are assembled into ionogel-based all-solid-state pouch cells with high mechanical stability and multiple optional outputs, demonstrating great potential for flexible energy storage in practical applications.

Microcrack Arrays in Dense Graphene Films for Fast-Ion-Diffusion Supercapacitors.

Laminated graphene film has great potential in compact high-power capacitive energy storage owing to the high bulk density and opened architecture. However, the high-power capability is usually limited by tortuous cross-layer ion diffusion. Herein, microcrack arrays are fabricated in graphene films as fast ion diffusion channels, converting tortuous diffusion into straightforward diffusion while maintaining a high bulk density of 0.92 g cm-3 . Films with optimized microcrack arrays exhibit sixfold improved ion diffusion coefficient and high volumetric capacitance of 221 F cm-3 (240 F g-1 ), representing a critical breakthrough in optimizing ion diffusion toward compact energy storage. This microcrack design is also efficient for signal filtering. Microcracked graphene-based supercapacitor with 30 µg cm-2  mass loading exhibits characteristic frequency up to 200 Hz with voltage window up to 4 V, showing high promise for compact, high-capacitance alternating current (AC) filtering. Moreover, a renewable energy system is conducted using microcrack-arrayed graphene supercapacitors as filter-capacitor and energy buffer, filtering and storing the 50 Hz AC electricity from a wind generator into the constant direct current, stably powering 74 LEDs, demonstrating enormous potential in practical applications. More importantly, this microcracking approach is roll-to-roll producible, which is cost-effective and highly promising for large-scale manufacture.

Spontaneous liquid-gas imbibition for characterization of carbon molecular sieves.

Spontaneous liquid-gas imbibition at 293.2K and 0.1 MPa was conducted to assess the micropore size and size-exclusion property of carbon molecular sieves (CMS). The CMS were firstly saturated with N(2) and then immersed into water. The volume of gas recovered by the water imbibition was measured and applied to evaluate the density of the N(2) adsorbed in the CMS. The micropore size of the CMS was determined by comparing the N(2) density from the water-N(2) imbibition with that calculated by grand canonical simulation. The micropore size evaluated by the liquid-gas imbibition coincides with that obtained by N(2) adsorption at ambient temperature. The size-exclusion property of the CMS was estimated through comparing the N(2) recovery by imbibition of liquids with increasing molecular dimensions, that is, water, benzene, and cyclohexane. The amount of N(2) recovered from benzene imbibition is dramatically less than that from the water imbibition, showing that the dominated micropore size of the CMS is smaller than 0.37 nm. Furthermore, the effect of chemical vapor deposition treatment on the porous texture of the CMS was revealed by the liquid-gas imbibition.