Controlled synthesis and growth mechanism of zinc cobalt sulfide rods on Ni-foam for high-performance supercapacitors

MOF-derived scaffolds as electrode materials: a mini-review

Metal-organic frameworks (MOFs) have unique properties but suffer from low conductivity and poor stability, limiting their use in energy storage. Transforming MOFs into other materials, like porous carbon or metal oxides/chalcogenides has been explored to overcome these limitations. However, these approaches still face issues such as dead volume and poor attachment due to insulating binders, causing high resistance and detachment. To address this, MOFs and their derived scaffolds directly on conductive substrates without binders have emerged. These electrodes offer simplified preparation, enhanced electron transfer, and improved interface contact. This mini-review focuses on MOF-derived scaffold electrodes using transition metal oxides, sulfides, selenides, and tellurides, which show promise in energy storage applications. Valuable insights, identified opportunities, and future suggestions in the field of MOF-derived scaffold electrodes and their applications in energy storage applications have been discussed.

Synthesis and Electrochemical Characterization of ZnMoS4 Nanorods on Nickel Foam Substrate for Advanced Hybrid Supercapacitor Applications

A single-step hydrothermal method was utilized to grow ZnMoS4 (ZMS) nanorods uniformly. Initially, [MoS4]2- and Zn2+ ions interacted to create active nucleation centers, which then led to the formation of primary particles. These particles then underwent spontaneous aggregation and self-assembly on the nickel foam (NF) substrate, which served as a superior 3D interconnecting network template. This aggregation occurred nearly perpendicular to the NF and promoted the uniform growth of ZMS nanorods. The nanorods structure ensures efficient and rapid electrolyte accessibility and ion diffusion, resulting in an increased specific capacitance (Cs) of 2,116 Fg1- (846.4 C g-1) at 1 A g-1 and maintaining about 90% of their capacitance after 10,000 cycles of galvanic charge-discharge (GCD). In a hybrid supercapacitor configuration, ZMS@NF//AC@NF achieved a peak specific power of 7.2 kW.kg-1 and a specific energy of 40.3 Wh.kg-1. Remarkably, it preserved 93% of its initial capacitance after more than 20,000 cycles. These findings affirm the potential of binder-free ZMS nanorods as effective positive electrodes in advanced hybrid supercapacitors.

Binder-free cupric-ion containing zinc sulfide nanoplates-like structure for flexible energy storage devices

Researchers have been enthusiastic about developing high-performance electrode materials based on metal chalcogenides for energy storage applications. Herein, we developed cupric ion-containing zinc sulfide (ZnS:Cu) nanoplates by using a solvothermal approach. The as-synthesized ZnS:Cu nanoplates electrode was characterized and analyzed by using XRD, SEM, TEM, EDS, and XPS. The binder-free flexible ZnS:Cu nanoplates exhibited excellent specific capacitance of 545 F g-1 at a current density of 1 A g-1. The CV and GCD measurements revealed that the specific capacitance was mainly attributed to the Faradaic redox mechanism. Further, the binder-free flexible ZnS:Cu nanoplates electrode retained 87.4% along with excellent Coulombic efficiency (99%) after 5000 cycles. The binder-free flexible ZnS:Cu nanoplates exhibited excellent conductivity, specific capacitance, and stability which are beneficial in energy storage systems. These findings will also open new horizons amongst material scientists toward the new direction of electrode development.

Animal- and Human-Inspired Nanostructures as Supercapacitor Electrode Materials: A Review

Human civilization has been relentlessly inspired by the nurturing lessons; nature is teaching us. From birds to airplanes and bullet trains, nature gave us a lot of perspective in aiding the progress and development of countless industries, inventions, transportation, and many more. Not only that nature inspired us in such technological advances but also, nature stimulated the advancement of micro- and nanostructures. Nature-inspired nanoarchitectures have been considered a favorable structure in electrode materials for a wide range of applications. It offers various positive attributes, especially in energy storage applications, such as the formation of hierarchical two-dimensional and three-dimensional interconnected networked structures that benefit the electrodes in terms of high surface area, high porosity and rich surface textural features, and eventually, delivering high capacity and outstanding overall material stability. In this review, we comprehensively assessed and compiled the recent advances in various nature-inspired based on animal- and human-inspired nanostructures used for supercapacitors. This comprehensive review will help researchers to accommodate nature-inspired nanostructures in industrializing energy storage and many other applications.

Ternary Nanohybrid of Ni3S2/CoMoS4/MnO2 on Nickel Foam for Aqueous and Solid-State High-Performance Supercapacitors

To overcome the issues related to supercapacitor (SC) electrodes, such as high cost, low specific capacitance (C_s), low energy density (ED), requirements for expensive binder, etc., binderless electrodes are highly desirable. Here, a new ternary nanohybrid is presented as a binder-free SC electrode based on Ni₃S₂, CoMoS₄, and MnO₂. A facile two-step hydrothermal route, followed by a short thermal annealing process, is developed to grow amorphous polyhedral structured CoMoS₄ and further wrap MnO₂ nanowires on Ni foam. This rationally designed binder-free electrode exhibited the highest C_s of 2021 F g⁻¹ (specific capacity of 883.8 C g⁻¹ or 245.5 mAh g⁻¹) at a current density of 1 A g⁻¹ in 1 M KOH electrolyte with a highly porous surface morphology. This electrode material exhibited excellent cycling stability (90% capacitance retention after 4000 cycles) due to the synergistic contribution of individual components and advanced surface properties. Furthermore, an aqueous binder-free asymmetric SC based on this ternary composite exhibited an ED of 20.7 Wh kg⁻¹, whereas a solid-state asymmetric SC achieved an ED of 13.8 Wh kg⁻¹. This nanohybrid can be considered a promising binder-free electrode for both aqueous and solid-state asymmetric SCs with these remarkable electrochemical properties.

Modified KBBF-like Material for Energy Storage Applications: ZnNiBO3(OH) with Enhanced Cycle Life

Not only are new and novel materials sought for electrode material development, but safe and nontoxic materials are also highly being intensively investigated. Herein, we prepare ZnNiBO₃(OH) (ZNBH), a modified and Be-free KBe₂BO₃F₂ (KBBF) family member as an effective electrode material. The novel ZNBH resembles the KBBF structure but with reinforced structure and bonding, in addition to well-incorporated conductive metals benefiting supercapacitor applications. The enhanced electronic properties of ZNBH are further studied by means of density functional theory calculations. The as-prepared ZNBH electrode material exhibits a specific capacity of 746 C g^-1 at a current density of 1 A g^-1. A hybrid supercapacitor (HSC) device is fabricated and successfully illuminated multiple color LEDs. Interestingly, even after being subjected to long charge-discharge for 10 000 cycles, the ZNBH//AC HSC device retains 97.2% of its maximum capacity, indicating the practicality of ZNBH as an electrode material.

Amin M, Yamauchi Y, Xu M, Pan L. MoS2 Nanosheets with Expanded Interlayer Spacing for Ultrastable Aqueous Mg-Ion Hybrid Supercapacitor

Aqueous magnesium ion supercapacitors (MISs) have attracted attention due to their safety, low cost and environmental friendliness. However, the cycling stability of MISs is usually not ideal due to magnesium...

Structure-controlled lignin complex for PLA composites with outstanding antibacterial, fluorescent and photothermal conversion properties

Polylactic acid (PLA) is increasingly being considered as an ideal biodegradable candidate to replace petroleum-based polymers. However, its practical applications are often hampered by the poor mechanical robustness and solo functionality. Herein, based on the mechanical property improvement of PLA we proposed a simple process of assembling lignin-hybridized modifier and PLA matrix, as opposed to the traditional trade-off between mechanical strength and functionality, while anchoring a biofluorescent moiety onto lignin surfaces. Specifically, the fluorophore group could act as interfacial compatibilizer of complex and facilitate the shape-tailored hybrids for promoting functionality flexibility. With the bimetallic hetero-particles, the preferable lignin-assembled complex could be controllably configured as an antibacterial, fluorophore and photothermal agent. Thus, mechanical enhancement, fluorescence introduction and favorable photothermal ability of the resulting PLA composites were successfully achieved for integrated unification of structural robustness, geometric integrity and functional multiplicity, which was never seen in the other reports. The results showed that PLA composites containing 5 wt% modified lignin, 10 wt% zinc oxide, and 5 wt% silver presented excellent mechanical, fluorescent, photothermal conversion properties. By controlling the ZnO content and morphology, strong inhibition of Escherichia coli (Gram-negative) than that of Staphylococcus Aureus (Gram-positive) was also observed. The flake-shaped ZnO /Ag hybrids contributed to better overall performance of PLA composites than the rod-shaped ZnO/Ag. In this work we developed a facile strategy to assemble a bioderived fluorophore with lignin particles for constructing a structure-controlled complex as a multitasking modifier, featuring mechanical unity and functional adaptability. Specifically, the lignin reinforcement and bimetallic hybrids with different morphologies were explored as an effective fluorophore, antibacterial and photothermal agent. Through multiple dehydration reactions, a conjugating fluorophore was successfully grafted on lignin surfaces to serve as an interface modifier without physical changing its structural robustness. And morphology-tailored hybrid was advantageously immobilized on predefined hetero-particle carrier of fluorescent lignin and endowed composites with desirable antimicrobial properties. The developed strategy would expand the functional applications of PLA materials in food packaging, biopharmaceuticals and simple fluorescent anti-counterfeiting.

Facile Synthesis of Zn-Co-S Nanostrip Cluster Arrays on Ni Foam for High-Performance Hybrid Supercapacitors

Mixed metal sulfides exhibit outstanding electrochemical performance compared to single metal sulfides and mixed metal oxides because of their richer redox reactions and high electronic conductivity. In the present study, Zn-Co-S nanostrip cluster arrays were formed from ZnCo₂O₄ grown on Ni foam by an anion exchange reaction using a two-step hydrothermal process. Morphological characterization confirmed that the Zn-Co-S nanostrip cluster arrays had grown homogeneously on the skeleton of the 3D Ni foam. The length of the nanostrip was approximately 8 µm, and the width ranged from 600 to 800 nm. The Ni foam-supported Zn-Co-S nanostrip cluster arrays were assessed directly for electrochemical supercapacitor applications. Compared to ZnCo₂O₄, the Zn-Co-S electrode exhibited a three-fold higher specific capacity of 830 C g⁻¹ at a specific current of 2.0 A g⁻¹. The higher polarizability, lower electro-negativity, and larger size of the S²⁻ ion played an important role in substituting oxygen with sulfur, which enhanced the performance. The Zn-Co-S//AC hybrid device delivered a maximum specific energy of 19.0 Wh kg⁻¹ at a specific power of 514 W kg⁻¹. The remarkable performance of Zn-Co-S nanostrip cluster arrays highlights their potential as a positive electrode for hybrid supercapacitor applications.

Supercapacitor electrode materials: addressing challenges in mechanism and charge storage

In recent years, rapid technological advances have required the development of energy-related devices. In this regard, Supercapacitors (SCs) have been reported to be one of the most potential candidates to meet the demands of human’s sustainable development owing to their unique properties such as outstanding cycling life, safe operation, low processing cost, and high power density compared to the batteries. This review describes the concise aspects of SCs including charge-storage mechanisms and scientific principles design of SCs as well as energy-related performance. In addition, the most important performance parameters of SCs, such as the operating potential window, electrolyte, and full cell voltage, are reviewed. Researches on electrode materials are crucial to SCs because they play a pivotal role in the performance of SCs. This review outlines recent research progress of carbon-based materials, transition metal oxides, sulfides, hydroxides, MXenes, and metal nitrides. Finally, we give a brief outline of SCs’ strategic direction for future growth.

Development of vertically aligned trimetallic Mg-Ni-Co oxide grass-like nanostructure for high-performance energy storage applications

Direct growth of nanostructured trimetallic oxide on substrate is considered as one of the promising electrode fabrication for high-performance hybrid supercapacitors. Herein, binder-free one-dimensional grass-like nanostructure was constructed on nickel foam by using electrodeposition approach. The admirable enhancement in rate capability was observed by the substitution of Mg and Ni in cobalt oxide crystallite. The prepared nickel cobalt oxide (NCO) and cobalt oxide (CO) electrode exhibited a rate capability of 57% and 58% (2 to 10 A g^-1) respectively. Interestingly, the rate capability was increased to 87% by the substitution of Mg and Ni simultaneously. The novel vertically aligned trimetallic Mg-Ni-Co oxide (MNCO) grass-like nanostructure electrode exhibited a high specific capacity of 846 C g^-1 at 2 A g^-1_, retained 97.3% specific capacity and showed an outstanding coulombic efficiency of 99% after 10,000 charge-discharge cycles. Moreover, we assembled hybrid supercapacitor (HSC) device for practical applications by using MNCO and activated carbon (AC) as the positive and negative electrode materials, respectively. HSC device exhibited a high specific capacity of 144 C g^-1 at 0.5 A g^-1. The high energy density of 31.5 Wh kg^-1 and the power density of 7.99 kW kg^-1 were achieved. All these interesting and attractive results demonstrate the significance of the vertically aligned electrode material towards practical applications.

A 3D walking palm-like core-shell CoMoO4@NiCo2S4@nickel foam composite for high-performance supercapacitors

Supercapacitors are one of the most promising renewable-energy storage systems. In this study, a three-dimensional walking palm-like core-shell CoMoO4@NiCo2S4@nickel foam (NF) nanostructure was synthesized using a two-step hydrothermal method for high electrochemical performance. The as-prepared composite exhibited a high areal capacitance of 17.0 F cm-2 (2433 F g-1) at a current density of 5 mA cm-2 in a three-electrode system. The results revealed outstanding cycling stability of 114% after 10 000 charge-discharge cycles. An aqueous asymmetric supercapacitor device assembled with CoMoO4@NiCo2S4@NF and activated carbon (AC)@NF as the positive and negative electrodes, respectively, showed a high capacitance of 4.19 F cm-2 (182 F g-1) and delivered a high energy density of 60.2 W h kg-1 at a power density of 188 W kg-1 and a high power density of 1.5 kW kg-1 at an energy density 29.2 W h kg-1, lighting 22 parallel-connected red light emitting diodes for over 60 s. The synergistic effects of the core-shell CoMoO4@NiCo2S4@NF electrode material highlight the potential of this composite as an effective active material for supercapacitor applications.