Multi‐Channel Hollow Carbon Nanofibers with Graphene‐Like Shell‐Structure and Ultrahigh Surface Area for High‐Performance Zn‐Ion Hybrid Capacitors

Abstract

Porous carbon is the most promising cathode material for Zn‐ion hybrid capacitors (ZIHCs), but is limited by insufficient active adsorption sites and slow ion diffusion kinetics during charge storage. Herein, a pore construction‐pore expansion strategy for synthesizing multi‐channel hollow carbon nanofibers (MCHCNF) is proposed, in which the sacrificial template‐induced multi‐channel structure eliminates the diffusion barrier for enhancing ion diffusion kinetics, and the generated ultrahigh surface area and high‐density defective structures effectively increase the quantity of active sites for charge storage. Additionally, a graphene‐like shell structure formed on the carbon nanofiber surface facilitates fast electron transport, and the highly matchable pore size of MCHCNF with electrolyte‐ions favors the accommodation of charge carriers. These advantages lead to the optimized ZIHCs exhibit high capacity (191.4 mAh g−1), high energy (133.1 Wh kg−1), along with outstanding cycling stability (93.0% capacity retention over 15000 cycles). Systematic ex situ characterizations reveal that the dual‐adsorption of anions and cations synergistically ensures the outstanding electrochemical performance, highlighting the importance of the highly‐developed porous structure of MCHCNF. This work not only provides a promising strategy for improving the capacitive capability of porous materials but also sheds light on charge storage mechanisms and rational design for advanced energy storage devices.

Iodine-Doped Hollow Carbon Nanocages without Templates Strategy for Boosting Zinc-Ion Storage by Nucleophilicity

“…Among these, the peaks of water decomposition were not observed in CV curves, demonstrating that the ZHC devices can charge-discharge well from 0.1 to 1.8 V. All carbon cathodes exhibited approximate rectangular CV curves, implying the capacitance-dominated mechanism for ion storage. Additionally, the existence of evident cathodic/anionic humps at 0.8/1.3 V provided a convincing demonstration of invertible oxidation-reduction reactions from Zn 2+ deposition/stripping on the Zn anode during the charge-discharge cycles, which generated considerable pseudo-capacity [26]. Observably, the CV curve of I, N-CNCs cathode-based ZHCs presented a larger integrated area than those of the Zn//N-CNCs and Zn//CMs in Figure 3b, revealing their highest specific capacity.…”

“…The XPS survey spectrum of I, N-CNCs affirmed the signals of I and N, with the of I and N doping contents of 0.4 at.% and 7.1 at.%, respectively. The high-resolution C1s XPS spectra (Figure S3a) were separated into five peaks at 284.6 eV, 285.3 eV, 286.7 eV, 288.5 eV, and 289.3 eV, representing sp 2 -C, sp 3 -C, -C-OH/-C-N, -C=O, and -COOH groups, respectively [26]. In addition, the component ratio of sp 3 to sp 2 can be applied to estimate the defect degree [27].…”

“…In addition, the Zn 2+ ion was bound with C=O and C + -I 5 − /C + -I 3 − by chemical adsorption with additional pseudo-capacitance. Moreover, the Zn 4 SO 4 (OH) 6 •4H 2 O partial precipitation and dissolution were attributed to the variation in pH from H + adsorption/desorption [26]. The OH − reacted with the Zn 2+ and SO 4 2− to prepare zinc hydroxide sulphate hydrate on the cathode surface with the increase in concentration, which was an important contribution for the Zn 2+ storage.…”

Tuning nitrogen species in 3D porous carbon via boron doping for boosted Zn-ion storage capability

“…5 Combining the benefits of capacitor-type porous carbon cathodes and battery-type Zn anodes, the ZIHCs could provide remarkable power densities as well as superior energy densities, which are much superior to those of other aqueous energy storage candidates. 6–10 Specifically, the Zn anode offers a high gravimetric capacity of 820 mA h g −1 and a low redox potential of −0.76 V versus the standard hydrogen electrode ( vs. SHE). 11–14 Compared with the high capacity of the Zn anode, porous carbon cathodes show much lower capacities, which limit the energy densities of ZIHCs.…”

Bimetallic Nitride TiVN Hollow Nanotubes for High-Performance Zinc-Ion Hybrid Supercapacitors

“…Therefore, hollow structures often possess enhanced capacity and stability compared to their solid counterparts. Indeed, many hollow structures of carbons have been explored for Zn-ion capacitors. − However, the synthesis of hollow nitrides with controlled compounds is much more challenging.…”