Electrochemically Synthesis of Nickel Cobalt Sulfide for High‐Performance Flexible Asymmetric Supercapacitors

Abstract

A lightweight, flexible, and highly efficient energy management strategy is highly desirable for flexible electronic devices to meet a rapidly growing demand. Herein, Ni–Co–S nanosheet array is successfully deposited on graphene foam (Ni–Co–S/GF) by a one‐step electrochemical method. The Ni–Co–S/GF composed of Ni–Co–S nanosheet array which is vertically aligned to GF and provides a large interfacial area for redox reactions with optimum interstitials facilitates the ions diffusion. The Ni–Co–S/GF electrodes have high specific capacitance values of 2918 and 2364 F g−1 at current densities of 1 and 20 A g−1, respectively. Using such hierarchical Ni–Co–S/GF as the cathode, a flexible asymmetric supercapacitor (ASC) is further fabricated with polypyrrple(PPy)/GF as the anode. The flexible asymmetric supercapacitors have maximum operation potential window of 1.65 V, and energy densities of 79.3 and 37.7 Wh kg−1 when the power densities are 825.0 and 16100 W kg−1, respectively. It's worth nothing that the ASC cells have robust flexibility with performance well maintained when the devices were bent to different angles from 180° to 15° at a duration of 5 min. The efficient electrochemical deposition method of Ni–Co–S with a preferred orientation of nanosheet arrays is applicable for the flexible energy storage devices.

Explicating the Sodium Storage Kinetics and Redox Mechanism of Highly Pseudocapacitive Binary Transition Metal Sulfide via Operando Techniques and Ab Initio Evaluation

“…For both Co 2p and Ni 2p, the results represent the coexistence of both the divalent (Co 2+ , Ni 2+ ) and trivalent states (Co 3+ , Ni 3+ ) . The S 2p are divided into two peaks at 161.6 and 162.9 eV accompanied by another shake‐up satellite peak at 169.6 eV, attributed to the superficial sulfur‐anion with low coordination numbers (161.6 eV) whereas the second component (162.9 eV) corresponds to the bonding between the transition metals and sulfur (Figure S11b, Supporting Information) . All the results are similar to the recent reports of NiCo 2 S 4 , confirms the formation of the NiCo 2 S 4 structure …”

Porous Ultrathin NiSe Nanosheet Networks on Nickel Foam for High‐Performance Hybrid Supercapacitors

“…The other two strong peaks were assigned to the satellite peaks. The Ni 2p XPS spectrum confirmed that the Ni element in the put‐NiSe NNs existed in the state of Ni 2+ cations . The small peak at 852.7 eV was associated with metallic Ni 0 of the nickel foam substrate .…”

“…The Ni 2p XPS spectrum confirmed that the Ni element in the put-NiSe NNs existedi nt he state of Ni 2 + cations. [33] The small peak at 852.7 eV was associ-ated with metallic Ni 0 of the nickel foam substrate. [34] The peaks of Se 3d 5/2 at 53.9 eV and Se 3d 3/2 at 54.5 eV in the highresolution Se 3d spectrum ( Figure 3d)w ere ascribed to Se 2À , [35] and the broad peak at 58.9 eV was attributed to the surface Se at ah igh oxidations tate.…”

“…The porous 3D NN and the inherent nature of the NiSe afforded high ion mobility, plenty of accessible activated sites, high conductivity, long cycle life, and vigorous electrochemical activity. The porous NiSe NNs delivered a specific capacity of approximately 443 mA h g −1 (807 μAh cm −2 ) at 3.0 A g −1 , which is one of the highest among all the developed TM . Even at a high current density of 10.0 A g −1 , the specific capacitance was maintained at approximately 317 mAh g −1 .…”

All Hierarchical Core–Shell Heterostructures as Novel Binder‐Free Electrode Materials for Ultrahigh‐Energy‐Density Wearable Asymmetric Supercapacitors

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Supercapacitors (SCs), especially fiber-shaped supercapacitors (FSCs) with their tiny volume, remarkable flexibility, and excellent stitchability as well as fast charge-discharge capability, a high power density, and a long cycle life, are promising energy storage and supply devices. [25,[28][29][30][31][32] Additionally, low specific capacitance of fiber-shaped asymmetric supercapacitors (FASCs) has limited further improvements in the energy density of these devices. [25,[28][29][30][31][32] Additionally, low specific capacitance of fiber-shaped asymmetric supercapacitors (FASCs) has limited further improvements in the energy density of these devices.…”