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It is an effective way to develop basswood (Tilia americana, hardwood)-derived thick carbon electrode for high energy density supercapacitors. The wood-derived anisotropic structural carbon electrodes have different transfer kinetics of the electrolyte, which will significantly affect the electrochemical performance especially at high current density. Therefore, the relationship between the sectional wood-derived electrodes and the electrochemical performance of supercapacitors were systematically studied. The results show that the high specific surface area (542 m2 g−1) of cross-sectional wood-derived carbon contributes to the excellent electrochemical performance (specific/area capacitance ~ 3040 mF cm−2/118 F g−1 at 1 mA cm−2, cycle stability ~ 82.2% after 10,000 cycles at 50 mA cm−2, and capacitive contribution of 76.64% at 5 mV s−1), which is attributed to the hierarchical porous structure and easily allows electrolytes to enter the interior even at high current density. This work provides a fundamental understanding of the dynamic behaviors of electrolyte at different wood sections, and it is expected to be extended to other wood species and wood-like structures for energy storage applications. [ABSTRACT FROM AUTHOR]

Increased energy consumption stimulates the development of various energy types. As a result, the storage of these different types of energy becomes a key issue. Supercapacitors, as one important energy storage device, have gained much attention and owned a wide range of applications by taking advantages of micro-size, lightweight, high power density and long cycle life. From this perspective, numerous studies, especially on electrode materials, have been reported and great progress in the advancement in both the fundamental and applied fields of supercapacitor has been achieved. Herein, a review of recent progress in carbon materials for supercapacitor electrodes is presented. First, the two mechanisms of supercapacitors are briefly introduced. Then, research on carbon-based material electrodes for supercapacitor in recent years is summarized, including different dimensional carbon-based materials and biomass-derived carbon materials. The characteristics and fabrication methods of these materials and their performance as capacitor electrodes are discussed. On the basis of these materials, many supercapacitor devices have been developed. Therefore, in the third part, the supercapacitor devices based on these carbon materials are summarized. A brief overview of two types of conventional supercapacitor according to the charge storage mechanism is compiled, including their development process, the merits or withdraws, and the principle of expanding the potential range. Additionally, another fast-developed capacitor, hybrid ion capacitors as a good compromise between battery and supercapacitor are also discussed. Finally, the future aspects and challenges on the carbon-based materials as supercapacitor electrodes are proposed. [ABSTRACT FROM AUTHOR]

Achieving a simple and mild preparation method to obtain high performance carbon-based flax fiber electrode for supercapacitor has become particularly important but still challenges. Hence, the excellent electrochemical performance of electrode was constructed by impregnation-heat treatment with ethylenediamine tetraacetic acid disodium zinc (EDTANa 2 Zn) and zinc nitrate (ZnNO 3) as activators. The results show that the decomposed zinc oxide (ZnO) of EDTANa 2 Zn leads to the prominently hierarchical porous structure and abundant nitrogen-doping, which provides more active storage sites for electrolyte. Likewise, the as-prepared electrode by EDTANa 2 Zn treatment exhibits the specific capacitance of 292 F g−1 at the current density of 0.5 A g−1, and keeps up with the capacitance retention of 102 % even after a 10, 000 long-cycles at the high current density of 10 A g−1. Significantly, the suitable zinc salt assisted preparation of high performance flax fiber carbon-based electrode provides a novel idea for future electrochemical energy storage. [Display omitted] • The obtained electrode was constructed by EDTANa 2 Zn and zinc nitrate. • The 950-EA electrode exhibits the specific capacitance of 292 F g−1–0.5 A g−1 • The 950-EA electrode keeps up with the capacitance retention of 102 % after 10,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of electrode thickness on the supercapacitance performance is studied. • Bass wood with hierarchical pores is easy processed to thick electrode. • The thick electrodes have high specific/areal/volumetric energy/power densities. • The SSC shows excellent cycling performance of 81% (20 mA cm−2, 15 000 cycles). The practical application of energy storage device requires high areal/volumetric energy density. One of the strategies is to design bulk electrode with hierarchical porous structure for the application of supercapacitor. Significantly, the energy storage electrochemical performance of the bulk electrode is highly influenced by the pore structure regulation and electrolyte infiltration. Therefore, it is necessary to design thick electrodes with proper pore structures and investigate the effect of thickness on the supercapacitance performance. In this work, bass wood is selected as the carbon source of electrode because of its hierarchical porous structure and easy processing into different thicknesses. The wood-derived carbon thick electrode with a thickness of 1.532 mm (CWT1.532) presents the best supercapacitance performance. Such electrode possesses a high active material loading of 54.75 mg cm−2. The symmetrical supercapacitor from CWT1.532 electrode displays remarkable specific capacitance of 65 F g−1 and areal/volumetric capacitance of 0.846 F cm−2 and 2.67 F cm−3 at 1.0 mA cm−2, respectively. It also exhibits mass/areal/volumetric power densities of 38.47 W kg−1, 500 mW cm2 and 1580 mW cm−3 as well as the corresponding energy densities of 9.04 Wh kg−1, 117.5 mWh cm−2 and 0.374 mWh cm−3, respectively. Moreover, the symmetrical supercapacitor shows an attractive cycling stability with a supercapacitance retention of 81.48% at 20 mA cm−2 even after 15 000 long-term cycles. This work provides an essential understanding about the effect of different thicknesses on the thick electrode-assembled supercapacitance and inspires future practical application in other energy storage areas. [ABSTRACT FROM AUTHOR]