Harmonizing Graphene Laminate Spacing and Zinc‐Ion Solvated Structure toward Efficient Compact Capacitive Charge Storage

Abstract

Aqueous Zn-ion hybrid capacitors (ZIHCs) present prominent potentials in flexible wearable electronics application scenarios due to their inherent high safety and low cost. Simultaneously, volumetric energy density is one of the crucial parameters to determine the lifespan of the wearable electronics, in which lightweight and miniaturization is a cardinal prerequisite for realistic application. In this work, an aqueous ZIHC is constructed by harmonizing interlayer spacing of the laminate graphene film and Zn-ion solvation structure to improve the electrode space utilization. Laminate graphene film interspacing has been customized in the range of 0.72-0.81 nm via regulating the ratio of crumple graphene mediator, thereby optimizing the transport kinetics of large size hydrated Zn ions. Zn-ion solvation structure is further tailored by introducing ZnCl 2 electrolyte salt to accouple such regulated laminar ionic transport channel. In a result, the thusderived ZIHC demonstrates an ultralong cycling lifespan of 100 000 cycles (93.9% capacitance retention), a preeminent volumetric capacitance (235.4 F cm −3 ), and a remarkable specific area capacitance contribution (C ssa ≈ 72 µF cm −2 ). Quasisolid-state ZIHC is assembled with ZnCl 2 solution-filled polyacrylamide gel electrolyte to concurrently achieve a superior areal capacitance of 1227 mF cm −2 and great mechanical flexibility toward practical wearable application.

Flexible solid-state hybrid supercapacitors for the internet of everything (IoE)

“…10(d)). 151 Pandey et al designed a dual-function supercapacitor-based energy-storing carbon fiber-reinforced polymeric composite (e-CFRP) for the body panel in an electric vehicle, which can not only store electrical energy but also function as the structural component for the electric vehicle's body shell. This is made possible by using a unique vertically attached graphene on carbon fiber structure electrodes, which plays an important role in improving the energy density because of the enhanced surface area.…”

“…The various composites for flexible solid-state electrodes used in the FSHSCs are listed in Table 1. 85,[138][139][140][141][142][144][145][146][149][150][151][152]155,[159][160][161][162][163][164][165][166][167][168][169] Although different yarn-and sheet-type FSHSCs described above have expanded our portfolio of these devices for wearable devices, the interdigitated micro-structure FSHSCs will become the EES of the future miniaturized, flexible, and wearable electronic devices. These are discussed in detail in the next section.…”

Zinc‐ion hybrid supercapacitors: Design strategies, challenges, and perspectives

“…The structure of the Zn‐ion solvation was modified by the addition of ZnCl 2 electrolyte salt to accommodate the controlled laminar ionic transport channels. [ 117 ] As shown in Figure 10h,i, the assembled ZHSCs using ZnCl 2 electrolytes exhibited higher volumetric and rate capacitance, and fast ion diffusion kinetics, compared to these using Zn(Ac) 2 , ZnSO 4 , and Zn(CF 3 SO 3 ) 2 salts. Overall, the experimental findings and computational results demonstrated that the solvation structure of the novel ZnCl 2 electrolyte might significantly increase zinc ion accessibility.…”

“…The salt concentration and anion type have been proved to have a close relationship with zinc deposition and stripping efficiency. [113][114][115][116][117] Wu et al [113] used 3 M Zn (CF 3 SO 3 ) 2 electrolyte to balance the trade-off between cycling stability and energy density with high Zn stripping/plating efficiency (Figure 10a, b). When the F I G U R E 10 (a, b) Schematic illustration of the discharging and charging mechanism of the designed zinc-ion hybrid supercapacitors (ZHSCs).…”

“…(i) Nyquist plots in different electrolytes for comparison. [117] Reproduced with permission: Copyright 2022, Wiley-VCH. , which meant an irreversible process of zinc stripping/plating (Figure 10c).…”