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[Display omitted] Self-supporting tree skeleton and densely stackable phenolic resin are cleverly coupled together by a "rebar-concrete" structure. The thick electrode as a master of space utilization has extremely high areal and volumetric energy density. This work confirms the effective coupling of the self-supporting skeleton and powder materials, providing novel ideas for the preparation of thick electrodes with high mass loading. • A "rebar-concrete" structure is proposed to facilitate the high space utilization of thick electrodes. • The areal capacitance of the thick electrode reaches an astonishing 11F cm−2. • The assembled SSC device delivers competitive areal energy density of 0.63 mWh cm−2. The thick electrode design with high packing density of active materials can increase the capacity in a limited space. However, the key challenge is still to develop a system with high space utilization and ensure electron/ion transport in thick electrode. This work proposes an interesting "rebar-concrete" structure, which successfully prepared wood/phenolic resin-derived thick electrode with high space utilization by in-situ polymerization of phenolic resin (concrete) in the wood (rebar) channel. The electrode exhibits an excellent three-dimensional interconnected hierarchical pore structure due to the uniform activation of in-situ anchored KOH particles. The mass loading (35 mg cm−2) and areal capacitance (11F cm−2) of the obtained composite electrode are increased to 446 % and 1257 % of the original balsa wood, respectively. The assembled symmetric supercapacitor (SSC) exhibits a high energy density of 0.63 mWh cm−2 (3.91 mWh cm−3) and an excellent cycle stability (95 % retention after 50 000 cycles), showing good practicability in lighting LEDs or driving a fan. This strategy achieves effective coupling of self-supporting skeleton and powder materials, providing more insights and possibilities for the preparation of high energy density thick electrodes. [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]

Hierarchical porous carbon-based electrodes, benefiting from their facilitated ion diffusion and electron conduction, have demonstrated enormous potential in supercapacitors. The preparation of hierarchical carbons with uniformity and appropriate porosity, however, still remains a grand challenge, which hinders their widespread applications. Herein, a hierarchical porous polyimide-derived carbon electrode (CPC-Fe/Zn) has been fabricated by employing bimetallic salts (Fe/Zn) as precursor and template to activate the cellulose/polyimide (PI) carbon (CPC). Originating from suitable distribution of mesopores and micropores, the obtained CPC-Fe/Zn delivers a high specific capacitance of 420 F/g at a current density of 1 A/g. Moreover, a symmetric supercapacitor device assembled with CPC-Fe/Zn exhibits delivers an energy density of 35.5 Wh/kg at a power density of 800 W/kg. Even at a larger current density of 20 A/g, the specific capacitance retention of such device still remains 92.5 % after 10,000 cycles, showing the rate performance and stability. This work has proposed a bimetallic salts template-assisted strategy to precisely modulate of the pore structure of carbon electrodes, which provides a promising platform to design superior electrodes for various electrochemical systems. [Display omitted] • The hierarchically porous structure of the material can be modulated precisely. • The symmetric supercapacitor exhibited a remarkable energy density of 35.5 Wh/kg @ 1000 W/kg. • The specific capacitance retention of symmetric supercapacitor reached 92.5 % after 10,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • High P-doped (9.24 at%) thick carbon electrodes (CW-P) by phytic acid treatment. • SSC exhibits high capacitance of 4.7F cm−2/206.5F g−1 at 1.0 mA cm−2. • Excellent capacitance retention of 90.5% after 20 000 cycles (@20 mA cm−2). • High energy density up to 0.94 mW h cm−2 (41.2 Wh kg−1). • High power density up to 0.6 mW cm−2 (26.3 W kg−1). Keeping outstanding electrochemical performance under high mass loading is critical to develop functional thick electrodes. Here, we report a high phosphorus-doped wood-derived carbon thick electrode for supercapacitor via phytic acid treatment, which can form hydrogen bonds with cellulose molecules in the wood. The content of phosphorus reaches up to 9.24 at% in carbonized wood with P-doping (CW-P-9.24), higher than most previously reported P-doped carbonaceous materials. CW-P-9.24 electrode (800 μm, 17.17 mg cm−2) exhibits greatly improved electrochemical performance, especially in energy density and cyclic stability. Significantly, the symmetrical supercapacitor device exhibits high areal and specific capacitance of 4.7 F cm−2 and 206.5 F g−1 at 1.0 mA cm−2 with prominent retention of 90.5% through the long-term cycling at 20 mA cm−2 for 20,000 cycles, and 0.94 mW h cm−2 (41.2 Wh kg−1) at power density of 0.6 mW cm−2 (26.3 W kg−1), and possesses excellent volumetric capacitance and energy density of 29.3 F cm−3 and 5.8 Wh cm−3, respectively. The outstanding performance can be attributed to the excellent hierarchical structure, low tortuosity, and high phosphorus doping with fast accessible channels at high current density. The extraordinary performance of CW-P has been elucidated by density functional theory calculations, which confirm the enhanced activity by P-doping. These results demonstrate that the CW-P electrode is promising for practical application in energy storage devices and encourage more investigations for thick electrode. [ABSTRACT FROM AUTHOR]