High-Performance Flexible Supercapacitor Device Composed of a Hierarchical 2-D MXene-Ni(OH)₂ Nanocomposite and Biomass-Derived Porous Carbon Electrodes

Abstract

The periodic layered structure due to the well-arranged sheets and the presence of surface terminations (-OH, -O, and -F) on those sheets makes MXene an attractive aspirant for supercapacitor devices. Though MXene exhibits interesting redox behavior, the collapse of its layered structure and irreversible stacking of sheets retard its redox reaction and restrict the ion transport process. To enhance its electrochemical performance, we have developed a nanocomposite where the α-Ni­(OH)2 petals are slid within the MXene structure as well as anchored on its surface. The multivalent character of Ni in Ni­(OH)2 enhances the redox performance of the nanocomposite. Fabrication of a high-performance flexible all-solid-state asymmetric supercapacitor (ASC) device has been carried out using this 50MXene-50Ni­(OH)2 nanocomposite as the cathode and the biomass-derived porous carbon as the anode. This ASC device manifested a high energy density of 29.3 W h kg–1 at a power density of 800 W kg–1 and 90% retention of specific capacitance (C S) even after ∼5000 GCD cycles. This supercapacitor device also demonstrated its mechanically flexible feature by showing its consistent electrochemical performance in diverse physical deformations. This flexible device illustrated its competence in real-world applications by illuminating an assembly of LED lights.

Nickel MXene Nanosheet and Heteroatom Self-Doped Porous Carbon-Based Asymmetric Supercapacitors with Ultrahigh Energy Density

“…The electrochemical performance of NiMX- and EMAC-700-based asymmetric supercapacitors is higher in comparison to that of recently reported MXene-based asymmetric supercapacitors as shown in Table . In all these reports, the poor performance could be ascribed to the (i) instability of MXene (i.e., Ti-, V-, and Nb-based MXene), (ii) incompatibility in the selection of the cathode and anode, and (iii) electrocatalytic activity of electrode materials. ,− By resolving this, we have demonstrated a highly stable nickel-based MXene and activated carbon-based supercapacitor with a 47.6 W h/kg energy density with outstanding stability representing an ideal combination for an asymmetric supercapacitor.…”

“…CV at 50 mV/s depicted in Figure a demonstrates a redox curve of NiMX with a small peak at ∼0.35 V, indicating the pseudonature, whereas the quasi-rectangular shape of EMAC-700 signifies the EDLC nature with a minor pseudoeffect . The presence of redox peaks in NiMX can be attributed to the adsorption and desorption of OH – ions from the electrolyte on the electrode surface as well as the formation of functional groups and interaction of Ni ions with them, thereby undergoing oxidation and reduction. , At 1 A/g, GCD curves further confirm the nature of both NiMX and EMAC-700 as shown in Figure b. NiMX showed ideal faradic or battery-like behavior of charging–discharging with negligible IR drop corresponding to high specific capacitance ( C SP ), while EMAC-700 further confirmed the synergistic effect of heteroatoms and wide distribution of micro–mesopores, inducing minor pseudobehavior to EDLC.…”

Spent Tea-Waste-Derived Porous Carbon-Supported Truncated Octahedral Cu2O for Highly Efficient Energy Storage Devices

“…4,11,12 In today's time, the usage of SCs in a public transport vehicle in China (Capabus, since 2006) and in the operating emergency door of an airplane in Europe (Airbus 380) are two live examples illustrating the future outlooks of different applications of SCs. 4,11 Supercapacitor devices are mainly categorized into two types: symmetric supercapacitor devices and asymmetric supercapacitor (ASC) devices. 13 Among these two classes of supercapacitor devices, ASCs are more preferable as they can achieve a wider potential range (e.g., ∼2.0 V in aqueous-based electrolytes, ∼2.7 V in organic electrolytes, and ∼4 V in ionic liquids).…”

Jujube Shell Based-Porous Carbon Composites Double-Doped by MnO2 and Ti3C2Tx: The Effect of Double Pseudocapacitive Doping on Electrochemical Properties

“…Materials that can induce pseudocapacitive properties include metal oxides, conductive polymers, MXenes, organometallic framework MOFs, etc. [ 17 , 18 ]. In order to provide a high operating voltage window and high energy density, induced pseudocapacitive materials must possess multiple oxidation valences.…”

“…Wang and Zhang [ 22 ] have used a solvothermal method to synthesize three-dimensional nano-flowered Ni-MOF, which shows a high specific capacitance and excellent rate performance in supercapacitors because nanoscale flower-like structures provide fast ion transport channels and low resistance. MXenes have a great application prospect in the field of pseudocapacitor materials in energy storage since their first development [ 18 ]. Due to the high conductivity, well mechanical properties, and hydrophilicity of MXenes, it is considered a pseudocapacitor material that can obtain a high specific capacitance [ 23 , 24 ].…”