Facile green synthesis of 3D porous glucose-based carbon aerogels for high-performance supercapacitors

Lignin Nanofiber Flexible Carbon Aerogels for Self-Standing Supercapacitors

Renewable feedstocks are sought for clean technology applications, including energy storage applications. In this study, LignoForce™ lignin, a biobased aromatic polymer commercially isolated from wood, was fractioned into two parts using acetone, and the resulting lignin fractions had distinct thermo-rheological behavior. These two fractionated lignins were combined in various ratios and transformed into nanofibers by electrospinning. Subsequently, electrospun fiber materials were disrupted by agitating the mats in water, and the materials were transformed into ultralight 3D aerogels through lyophilization and post-process controlled heating. Using only this combination of two fractions, the morphology of lignin nanofibers was tailored by heat treatment, resulting in lignin aerogels with high flexibility and significant shape recovery properties. Various microscale structures of lignin fibers impacted the resulting physical properties of the elastic aerogel materials, such as resilience, compressive strength, and electrical conductivity for the corresponding carbonized samples. By exploiting lignin's sensitivity to heat and tailoring the thermal properties of the lignin through fractionation, the work provided an interesting path to form robust lignin-derived functional materials without any toxic chemical additives and significant ability to serve as free-standing electrodes with specific capacitance values better than some graphene-based supercapacitors.

One-Step Hydrothermal Synthesis of Glucose-Induced Low Crystallinity NiCo-Based Layered Double Hydroxides for High-Performance Asymmetric Supercapacitors

In order to improve the electrochemical performance of NiCo-based layered double hydroxide (NiCoLDH), the synthesis of low-crystallinity NiCoLDH was induced by the adsorption of glucose and NiCoLDH. The results showed that glucose could not only effectively regulate the pore structure and morphology of NiCoLDH, but also had a regular effect on crystallinity. Pure phase NiCoLDH had higher crystallinity. When the mass of glucose is 0.05 g, the prepared NiCoLDH-0.05 is a short-range ordered structure embedded in the amorphous matrix. The crystallinity of the product decreases further with the further increase of glucose mass. Since the ordered structures have higher electrical conductivity, and amorphous structures have more defects and active sites, the structure of NiCoLDH-0.05 is conducive to achieving the best electrochemical performance. Electrochemical test results show that NiCoLDH-0.05 has a high specific capacitance, about 12 times that of the pure phase NiCoLDH, the mass of glucose is higher than or below 0.05 g, the specific capacitance will be further reduced. NiCoLDH-0.05 and activated carbon assembled into an asymmetric supercapacitor have a power density of 400 W kg-1 at an energy density of 32.7 Wh kg-1. This study provides a new idea for obtaining excellent electrochemical properties by adjusting LDH crystallinity.

Coal-based 3D hierarchical porous carbon aerogels for high performance and super-long life supercapacitors

Coal-based 3D hierarchical porous carbon aerogels (3D HPCAs) has been successfully fabricated from a freeze-drying method and with subsequent of calcination process, using coal oxide as carbon precursors, and PVA as both cross-linking agent and sacrifice template. The 3D HPCAs, using as electrode materials for supercapacitors, display outstanding electrochemical performance. The optimal sample (HPCAs-0.4-800) presents a high specific capacitance of 260 F g-1 at 1 A g-1, and exhibits considerable rate capability with the retention of 81% at 10 A g-1. Notably, HPCAs-0.4-800 shows an excellent cycling stability with 105% of the capacitance retention after 50000 cycles at 10 A g-1, attributing to its unique hierarchical porosity, high surface area up to 1303 m2 g-1, and improved conductivity. This work offers a promising route to synthesize coal-based porous carbon aerogels electrode materials for supercapacitors.

Hollow mesoporous carbon cages by pyrolysis of waste polyethylene for supercapacitors

Hollow mesoporous carbon cages with high electrochemical properties were prepared by a facile strategy using waste plastics as carbon source.