Molecularly-regulating oxygen-containing functional groups of ramie activated carbon for high-performance supercapacitors.

Effectively managing oxygen-containing functional groups (OCFGs) within activated carbon and methodically elucidating their intricate types and proportions are essential for considerably improving the electrochemical performance of carbon-based supercapacitors. Herein, we designed a ZnCl2-based molecular regulation strategy to introduce OCFGs into ramie-activated carbon (RAC), managing different OCFGs and revealing their structure-activity relationship with electrochemical performance. Thus, this regulated RAC, with a 3.5-fold enhancement in advantageous OCFGs (a-OCFGs: CO and COO), exhibits a supreme specific capacitance of 286.4F g-1 at 1 A/g and an excellent capacitance retention rate of 89.7 % at 20 A/g in an aqueous electrolyte, considerably surpassing that of nonregulated RAC (212.0F g-1 and 81.9 %). This confirms that a-OCFGs provide ample ion-storage accommodation and suppress solvent electronic oxidation, thereby enhancing electrochemical performance. Furthermore, its electrochemical performance is competitive with that of the commercial YP-50F (129.2F g-1 at 1 A/g). Therefore, this work not only highlights the contributions of specific OCFGs to high electrochemical performance but also designs a promising commercial electrode material to meet the demands of OCFGs-adequate carbon-based energy storage devices.

Capillary Evaporation on High-Dense Conductive Ramie Carbon for Assisting Highly Volumetric-Performance Supercapacitors.

Conductive biomass carbon possesses unique properties of excellent conductivity and outstanding thermal stability, which can be widely used as conductive additive. However, building the high-dense conductive biomass carbon with highly graphitized microcrystals at a lower carbonization temperature is still a major challenge because of structural disorder and low crystallinity of source material. Herein, a simple capillary evaporation method to efficiently build the high-dense conductive ramie carbon (hd-CRC) with the higher tap density of 0.47 cm3 g-1 than commercialized Super-C45 (0.16 cm3 g-1 ) is reported. Such highly graphitized microcrystals of hd-CRC can achieve the high electrical conductivity of 94.55 S cm-1 at the yield strength of 92.04 MPa , which is higher than commercialized Super-C45 (83.92 S cm-1 at 92.04 MPa). As a demonstration, hd-CRC based symmetrical supercapacitors possess a highly volumetric energy density of 9.01 Wh L-1 at 25.87 kW L-1 , much more than those of commercialized Super-C45 (5.06 Wh L-1 and 19.30 kW L-1 ). Remarkably, the flexible package supercapacitor remarkably presents a low leakage current of 10.27 mA and low equivalent series resistance of 3.93 mΩ. Evidently, this work is a meaningful step toward high-dense conductive biomass carbon from traditional biomass graphite carbon, greatly promoting the highly-volumetric-performance supercapacitors.