Wood‐Derived, Conductivity and Hierarchical Pore Integrated Thick Electrode Enabling High Areal/Volumetric Energy Density for Hybrid Capacitors

Abstract

For the proliferation of the supercapacitor technology, it is essential to attain superior areal and volumetric performance. Nevertheless, maintaining stable areal/volumetric capacitance and rate capability, especially for thick electrodes, remains a fundamental challenge. Here, for the first time, a rationally designed porous monolithic electrode is reported with high thickness of 800 µm (46.74 mg cm−2, with high areal mass loading of NiCo2S4 6.9 mg cm−2) in which redox‐active Ag nanoparticles and NiCo2S4 nanosheets are sequentially decorated on highly conductive wood‐derived carbon (WC) substrates. The hierarchically assembled WC@Ag@NiCo2S4 electrode exhibits outstanding areal capacitance of 6.09 F cm−2 and long‐term stability of 84.5% up to 10 000 cycles, as well as exceptional rate capability at 50 mA cm−2. The asymmetric cell with an anode of WC@Ag and a cathode of WC@Ag@NiCo2S4 delivers areal/volumetric energy density of 0.59 mWh cm−2/3.93 mWh cm−3, which is much‐improved performance compared to those of most reported thick electrodes at the same scale. Theoretical calculations verify that the enhanced performance could be attributed to the decreased adsorption energy of OH− and the down‐shifted d‐band of Ag atoms, which can accelerate the electron transport and ion transfer.

Wood‐Derived High‐Mass‐Loading MnO2 Composite Carbon Electrode Enabling High Energy Density and High‐Rate Supercapacitor

“…This can be attributed to how the low loading of MnO 2 nanosheets enhances the electric conductivity, which is affected by the matrix heterojunction and changes the electronic structure trend. [12,21] A subsequent decrease in electronic conductivity was also observed with the increase of mass loading, which was associated with the agglomeration of MnO 2 with high mass loading and was consistent with the impedance analysis results. Also, compared the WC@MnO 2 -20 electrode, the excessive loading of MnO 2 nanosheets in the Small 2022, 18, 2201307 and d) pore size distribution of the WC, WC@MnO 2 -10, WC@MnO 2 -20, and WC@MnO 2 -50 samples; e) Wide-range XPS spectra and f) high-resolution Mn 2p spectra of the WC@MnO 2 -20 sample.…”

“…[13a,14] The unique pore structure of wood-derived carbon provides a continuous connection pathway for fast electron transport, while the channel filled with electrolyte/electrode afford a low-tortuous pathway for ion transport. [12] Inspired by this, we further combined wood-derived carbon with KMnO 4 to directly grow MnO 2 nanosheets composite thick carbon electrode under hydrothermal conditions without the need for an additional conductive agent or binder.…”

“…[10] Hu et al [11] impregnated a slurry of commercial LiFePO 4 nanoparticles and epoxy resin into the wood-derived collector channels to obtain the low tortuosity and high mass-loading of the LiFePO 4carbon framework 3D electrode and achieve a high capacity of 7.6 mAh cm −2 . In our previous work, [12] the as-prepared NiCo 2 S 4 -based composite thick carbon electrode prepared through pyrolysis with electrodeposition successfully achieved…”

Hierarchical pipe cactus-like Ni/NiCo-LDH core–shell nanotube networks as a self-supported battery-type electrode for supercapacitors with high volumetric energy density

“…Furthermore, with a higher current density of 50 mA cm À2 , it retains an energy density of 4.9 mWh cm À3 at a higher power density of 4769.3 mW cm À3 . The accomplished superior volumetric energy density (14.7 mWh cm À3 ) outperforms the emerging symmetric, asymmetric, and This journal is © The Royal Society of Chemistry 2022 hybrid devices, with outstanding volumetric energy density, encompassing GF/NiCo 2 S 4 //CF (12.3 mWh cm À3 ), 19 MnO 2 /TCC// TCC (9.4 mWh cm À3 ), 75 WC@Ag@NiCo 2 S 4 //WC@Ag (3.93 mWh cm À3 ), 81 Co 9 S 8 //Co 3 O 4 @RuO 2 (1.44 mWh cm À3 ), 73 symmetric NiCo-LDH@Ni-coated textile (1.25 mWh cm À3 ), 82 NiCoP/Ti 3 C 2 MXene//AC (2.2 mWh cm À3 ), 74 Co(OH) 2 @CW//CW (14.1 mWh cm À3 ), 72 CuCo 2 O 4 //AC (0.81 mWh cm À3 ), 83 symmetric mesoporous network-like NiCo 2 O 4 (0.69 mWh cm À3 ), 84 and Ni(OH) 2 // Mn 3 O 4 (0.35 mWh cm À3 ), 85 as represented in Table S2 † and Fig. 6a.…”

Changes in Chemical and Thermal Properties of Bamboo after Delignification Treatment

“…Consequently, these materials have become research hotspots in recent years. Several functional studies have recently been conducted on various wood and bamboo fibre materials, such as transparent wood, aesthetic wood, flame retardant fibre materials, oil-water separation sponges, supercapacitor electrodes, and bioplastics [2][3][4][5][6][7]. Naturally occurring lignocellulosic materials, such as wood and bamboo, are porous materials.…”