High performance asymmetric supercapacitors based on Ti3C2T x MXene and electrodeposited spinel NiCo2S4 nanostructures

Flexible Hybrid Supercapacitor Achieving 2.2 V with NiCo2S4/Polyaniline/MnO2 and N, S-Co-Doped Carbon Nanofibers for Ultra-High Energy Density

Flexible all-solid-state asymmetric supercapacitors (FAASC) represent a highly promising power sources for wearable electronics. However, their energy density is relatively less as compared to the conventional batteries. Herein, a novel ultra-high energy density FAASC is developed using nickel-cobalt sulfide (NiCo2S4)/polyaniline (PANI)/manganese dioxide (MnO2) ternary composite on carbon fiber felt (CF) as positive and N, S-co-doped carbon nanofibers (CNF)/CF as negative electrode, respectively. Initially, porous δ-MnO2 nanoworm-like network is decorated on CF using potentiodynamic method. Subsequently, interconnected PANI nanostructures is grown on the MnO2 via a facile in situ chemical polymerization, followed by the electrodeposition of highly porous NiCo2S4 nanowalls. Benefiting from 3D porous structure of conductive CF and redox active properties of NiCo2S4, PANI and MnO2, FAASC achieved a superior energy storage capacity. Later, high-performance N, S-co-doped CNF/CF negative electrode is synthesized using electropolymerization of PANI nanofibers on CF, followed by the carbonization process. The assembled FAASC exhibits a wide voltage window of 2.2 V and remarkable specific capacitance of 143 F g-1 at a current density of 1 A g-1. The cell further delivers a superb energy density of 71.6 Wh kg-1 at a power density of 492.7 W kg-1, supreme cycle life and remarkable electrochemical stability under mechanical bending.

Construction of Nickel Molybdenum Sulfide/Black Phosphorous 3D Hierarchical Structure Toward High Performance Supercapacitor Electrodes

Supercapacitors (SCs) with outstanding versatility have a lot of potential applications in next-generation electronics. However, their practical uses are limited by their short working potential window and ultralow-specific capacity. Herein, the facile one-step in-situ hydrothermal synthesis is employed for the construction of a NiMo3S4/BP (black phosphorous) hybrid with a 3D hierarchical structure. After optimization, the NiMo3S4/BP hybrid displays a high specific capacitance of 830 F/g at 1 A/g compared to the pristine NiMo3S4 electrode. The fabricated NiMo3S4/BP//NiCo2S4/Ti3C2Tx asymmetric supercapacitor exhibits a better specific capacitance of 120 F/g at 0.5 A/g, which also demonstrates a high energy density of 54 Wh/kg at 1148.53 W/kg and good cycle stability with capacity retention of 86% and 97% of Coulombic efficiency after 6000 cycles. Further from the DFT simulations, the hybrid NiMo3S4/BP structure shows higher conductivity and quantum capacitance, which demonstrate greater charge storage capability, due to enhanced electronic states near the Fermi level. The lower diffusion energy barrier for the electrolyte K+ ions in the hybrid structure is facilitated by improved charge transfer performance for the hybrid NiMo3S4/BP. This work highlights the potential significance of hybrid nanoarchitectonics and compositional tunability as an emerging method for improving the charge storage capabilities of active electrodes.

Recent Advances and Strategies in MXene-Based Electrodes for Supercapacitors: Applications, Challenges and Future Prospects

With the growing demand for technologies to sustain high energy consumption, supercapacitors are gaining prominence as efficient energy storage solutions beyond conventional batteries. MXene-based electrodes have gained recognition as a promising material for supercapacitor applications because of their superior electrical conductivity, extensive surface area, and chemical stability. This review provides a comprehensive analysis of the recent progress and strategies in the development of MXene-based electrodes for supercapacitors. It covers various synthesis methods, characterization techniques, and performance parameters of these electrodes. The review also highlights the current challenges and limitations, including scalability and stability issues, and suggests potential solutions. The future outlooks and directions for further research in this field are also discussed, including the creation of new synthesis methods and the exploration of novel applications. The aim of the review is to offer a current and up-to-date understanding of the state-of-the-art in MXene-based electrodes for supercapacitors and to stimulate further research in the field.

Progress of 2D MXene as an Electrode Architecture for Advanced Supercapacitors: A Comprehensive Review

Supercapacitors, designed to store more energy and be proficient in accumulating more energy than conventional batteries with numerous charge-discharge cycles, have been developed in response to the growing demand for energy. Transition metal carbides/nitrides called MXenes have been the focus of researchers' cutting-edge research in energy storage. The 2D-layered MXenes are a hopeful contender for the electrode material due to their unique properties, such as high conductivity, hydrophilicity, tunable surface functional groups, better mechanical properties, and outstanding electrochemical performance. This newly developed pseudocapacitive substance benefits electrochemical energy storage because it is rich in interlayer ion diffusion pathways and ion storage sites. Making MXene involves etching the MAX phase precursor with suitable etchants, but different etching methods have distinct effects on the morphology and electrochemical properties. It is an overview of the recent progress of MXene and its structure, synthesis, and unique properties. There is a strong emphasis on the effects of shape, size, electrode design, electrolyte behavior, and other variables on the charge storage mechanism and electrochemical performance of MXene-based supercapacitors. The electrochemical application of MXene and the remarkable research achievements in MXene-based composites are an intense focus. Finally, in light of further research and potential applications, the challenges and future perspectives that MXenes face and the prospects that MXenes present have been highlighted.

Development of an Amorphous Nickel Boride/Manganese Molybdate Heterostructure as an Efficient Electrode Material for a High-Performance Asymmetric Supercapacitor

The exploration of heterostructure materials with unique electronic properties is considered a desirable platform for fabricating electrode/surface interface relationships for constructing asymmetric supercapacitors (ASCs) with high energy density. In this work, a heterostructure based on amorphous nickel boride (Ni_XB) and crystalline square bar-like manganese molybdate (MnMoO₄) was prepared by a simple synthesis strategy. The formation of the Ni_XB/MnMoO₄ hybrid was confirmed by powder X-ray diffraction (p-XRD), field emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), Brunauer-Emmett-Teller (BET), Raman, and X-ray photoelectron spectroscopy (XPS). In this hybrid system (Ni_XB/MnMoO₄), the intact combination of Ni_XB and MnMoO₄ leads to a large surface area with open porous channels and abundant crystalline/amorphous interfaces with a tunable electronic structure. This Ni_XB/MnMoO₄ hybrid shows high specific capacitance (587.4 F g^-1) at 1 A g^-1, and it even retains a capacitance of 442.2 F g^-1 at 10 A g^-1, indicating superior electrochemical performance. The fabricated Ni_XB/MnMoO₄ hybrid electrode also exhibited an excellent capacity retention of 124.4% (10000 cycles) and a Coulombic efficiency of 99.8% at a current density of 10 A g^-1. In addition, the ASC device (Ni_XB/MnMoO₄//activated carbon) achieved a specific capacitance of 104 F g^-1 at 1 A g^-1 and delivered a high energy density of 32.5 Wh.kg^-1 with a power density of 750 W·kg^-1. This exceptional electrochemical behavior is due to the ordered porous architecture and the strong synergistic effect of Ni_XB and MnMoO₄, which enhances the accessibility and adsorption of OH^- ions that improve electron transport. Moreover, the Ni_XB/MnMoO₄//AC device exhibits excellent cyclic stability with a retention of 83.4% of the original capacitance after 10000 cycles, which is due to the heterojunction layer between Ni_XB and MnMoO₄ that can improve the surface wettability without causing structural changes. Our results show that the metal boride/molybdate-based heterostructure is a new category of high-performance and promising material for the growth of advanced energy storage devices.

Tetra germanium nonaselenide enwrapped with reduced graphene oxide and functionalized carbon nanotubes (Ge4Se9/RGO/FCNTs) hybrids for improved energy storage performances

The development of multifunctional layered semiconductor materials and their carbonaceous hybrids as acceptable positive electrode materials for supercapacitor application is of key interest. Ternary germanium selenide (Ge₄Se₉) with reduced graphene oxide (RGO) and functionalized carbon nanotube (FCNT) hybrids were successfully synthesized by following a one-step hydrothermal approach, and their electrochemical energy storage performance toward supercapacitor (SC) applications was investigated. It was observed that the specific capacitance of Ge₄Se₉/RGO/FCNTs was 440 F g^-1 at 1 A g^-1 in an acidic (1 M H₂SO₄) medium. Further, the material showed 83% retention of its own initial value of capacitance with 98% coulombic efficiency after 5000 galvanostatic charge-discharge cycles. Considering the two-dimensional (2D) layered structures of MXenes with their greater stability, exceptional hydrophilicity, and pseudocapacitive behavior in aqueous electrolytes makes them an alternative for the fabrication of asymmetric SC devices. The above findings about MXenes suggest the design of an asymmetric device using MXene as the negative electrode material and as-prepared Ge₄Se₉/RGO/FCNTs as the positive electrode material in a similar electrolyte media. The fabricated Ge₄Se₉/RGO/FCNTs//MXenes displayed a higher specific capacitance of 102 F g^-1 at 1 A g^-1, with an acceptable energy density (E.D.) of 32 W h kg^-1 and a power density (P.D.) of 1071 W kg^-1. Furthermore, over long-term repeated 5000 GCD cycles the fabricated device retained 92% of its initial capacitance and good reversibility (96% coulombic efficiency), making the Ge₄Se₉/RGO/FCNT//MXenes assembly a preferable electrode material for enhancing asymmetric SC performance.