Eliminating the Micropore Confinement Effect of Carbonaceous Electrodes for Promoting Zn‐Ion Storage Capability

Abstract

Zinc‐ion capacitors (ZICs) are promising technology for large‐scale energy storage by integrating the attributes of supercapacitors and zinc‐ion batteries. Unfortunately, the insufficient Zn2+‐storage active sites of carbonaceous cathode materials and the mismatch of pore sizes with charge carriers lead to unsatisfactory Zn2+ storage capability. Herein, new insights for boosting Zn2+ storage capability of activated nitrogen‐doped hierarchical porous carbon materials (ANHPC‐x) are reported by effectively eliminating the micropore confinement effect and synchronously elevating the utilization of active sites. Therefore, the best‐performed ANHPC‐2 delivers impressive electrochemical properties for ZICs in terms of excellent capacity (199.1 mAh g−1), energy density (155.2 Wh kg−1), and durability (65 000 cycles). Systematic ex situ characterizations together with in situ electrochemical quartz crystal microbalance and Raman spectra measurements reveal that the remarkable electrochemical performance is assigned to the synergism of the Zn2+, H+, and SO42− co‐adsorption mechanism and reversible chemical adsorption. Furthermore, the ANHPC‐2‐based quasi‐solid‐state ZIC demonstrates excellent electrochemical capability with an ultralong lifespan of up to 100 000 cycles. This work not only provides a promising strategy to improve the Zn2+ storage capability of carbonaceous materials but also sheds lights on charge‐storage mechanism and advanced electrode materials’ design for ZICs toward practical applications.

Revealing the Self-Doping Defects in Carbon Materials for the Compact Capacitive Energy Storage of Zn-Ion Capacitors

“…However, H + (aq) is usually presented in aqueous electrolyte due to the hydrolysis of Zn 2+ , which will interfere with the understanding of the energy storage mechanism because H + (aq) can easily contribute to pseudocapacitance by reversibly reacting with the functional groups on carbon. This phenomenon has been proved by several pioneer works that some oxygenated carbons exhibit Zn 2+ and H + costorage behavior in aqueous Zn-ion capacitors. ,,− Specifically, Xu et al showed that the reduced graphene oxide (heat treatment at 200 °C) performed 245 F g –1 in the aqueous electrolyte, while only 146 F g –1 in the organic electrolyte in which H + (aq) is not present. Therefore, for an in-depth understanding of the effect of self-doping defects on electrochemical performance, we assembled the Zn-ion capacitors in not only aqueous electrolyte but also organic (acetonitrile) electrolyte (Figure ).…”

“…Defect engineering of carbon materials has been widely investigated for electrocatalytic reactions and/or energy storage. − The foreign-doping defects (e.g., heteroatoms and functional groups) not only serve as the active sites but also endow the carbon materials with some novel functions such as high activity and good surface wettability. − For example, Alshareef and Zhao proposed that oxygen-bearing functional groups possessed a reversible pseudocapacitive behavior by reacting with H + and Zn 2+ to enhance the energy storage ability of porous carbon for aqueous Zn-ion capacitors. Lu revealed that nitrogen-bearing functional groups could generate pseudocapacitance by reducing the energy barrier of C–O–Zn bonding.…”

A flexible and stable zinc-ion hybrid capacitor with polysaccharide-reinforced cross-linked hydrogel electrolyte and binder-free carbon cathode

“…3c). 42 The TEM and derived mapping images of GCNF certify that C, N, and O elements are uniformly distributed throughout GCNF, illustrating that the nitrogen heteroatom is in situ integrated into GCNF due to the employment of nitrogenous PAN (Fig. 3d).…”

Co‐Intercalation of Dual Charge Carriers in Metal‐Ion‐Confining Layered Vanadium Oxide Nanobelts for Aqueous Zinc‐Ion Batteries

“…These results were used to determine the ratio of diffusion-controlled and non-diffusion-controlled contributions to the overall cycling capacity. [33,34] Based on calculations of pseudocapacitive contributions in the Supporting Information, the fitted slope b-values are 0.82, 0.85, 0.84, and 0.87, revealing a synergistic charge storage based on diffusion-controlled and capacitive processes (Figure 4g). The detailed pseudocapacitance ratio was 52.7 % at a scan rate of 3.0 mV s À 1 (Figure 4h).…”