MnO2 core-shell type materials for high-performance supercapacitors: A short review

Recent Development on Transition Metal Oxides-Based Core-Shell Structures for Boosted Energy Density Supercapacitors

In recent years, nanomaterials exploration and synthesis have played a crucial role in advancing energy storage research, particularly in supercapacitor development. Researchers have diversified materials, including metal oxides, chalcogenides, and composites, as well as carbon materials, to enhance energy and power density. Balancing energy density with electrochemical stability remains challenging, driving intensified efforts in advancing electrode materials. This review focuses on recent progress in designing and synthesizing core-shell materials tailored for supercapacitors. The core-shell architecture offers advantages such as increased surface area, redox active sites, electrical conductivity, ion diffusion kinetics, specific capacitance, and cyclability. The review explores the impact of core and shell materials, specifically transition metal oxides (TMOs), on supercapacitor electrochemical behavior. Metal oxide choices, such as cobalt oxide as a preferred core and manganese oxide as a shell, are discussed. The review also highlights characterization techniques for assessing structural, morphological, and electrochemical properties of core-shell materials. Overall, it provides a comprehensive overview of ongoing TMOs-based core-shell material research for supercapacitors, showcasing their potential to enhance energy storage for applications ranging from gadgets to electric vehicles. The review outlines existing challenges and future opportunities in evolving TMOs-based core-shell materials for supercapacitor advancements, holding promise for high-efficiency energy storage devices.

Hierarchically core-shell structured nanocellulose/carbon nanotube hybrid aerogels for patternable, self-healing and flexible supercapacitors

The flexible and self-healing supercapacitors (SCs) are considered to be promising smart energy storage devices. Nevertheless, the SCs integrated with flexibility, lightweight, pattern editability, self-healing capabilities and desirable electrochemical properties remain a challenge. Herein, an all-in-one self-healing SC fabricated with the free-standing hybrid film (TCMP) composed of the 2,2,6,6-tetramethylpiperidin-1-yloxy-oxidized cellulose nanofibers (TOCNs) carried carbon nanotubes (CNTs), manganese dioxide (MnO2) and polyaniline (PANI) as the electrode, polyvinyl alcohol/sulfuric acid (PVA/H2SO4) gel as the electrolyte and dynamically cross-linked cellulose nanofibers/PVA/sodium tetraborate decahydrate (CNF/PB) hydrogel as the self-healing electrode matrix is developed. The TCMP film electrodes are fabricated through a facile in-situ polymerization of MnO2 and PANI in TOCNs-dispersed CNTs composite networks, exhibiting lightweight, high electrical conductivity, flexibility, pattern editability and excellent electrochemical properties. Benefited from the hierarchically porous structure and high mechanical properties of TOCNs, excellent electrical conductivity of CNTs and the desirable synergistic effect of pseudocapacitance induced by MnO2 and PANI, the assembled SC with an interdigital structure demonstrated a high areal capacitance of 1108 mF cm-2 at 2 mA cm-2, large areal energy density of 153.7 μWh cm-2 at 1101.7 μW cm-2. A satisfactory bending cycle performance (capacitance retention up to 95 % after 200 bending deformations) and self-healing characteristics (∼90 % capacitance retention after 10 cut/repair cycles) are demonstrated for the TCMP-based symmetric SC, delivering a feasible strategy for electrochemical energy storage devices with excellent performance, designable patterns and desirable safe lifespan.

Unveiling the potential of PANI@MnO2@rGO ternary nanocomposite in energy storage and gas sensing

The development of advanced materials for energy storage and gas sensing applications has gained significant attention in recent years. In this study, we synthesized and characterized PANI@MnO2@rGO ternary nanocomposites (NCs) to explore their potential in supercapacitors and gas sensing devices. The ternary NCs were synthesized through a multi-step process involving the hydrothermal synthesis of MnO2 nanoparticles, preparation of PANI@rGO composites and the assembly to the ternary PANI@MnO2@rGO ternary NCs. The structural, morphological, and compositional characteristics of the materials were thoroughly analyzed using techniques such as XRD, FESEM, TEM, FTIR, and Raman spectroscopy. In the realm of gas sensing, the ternary NCs exhibited excellent performance as NH3 gas sensors. The optimized operating temperature of 100 °C yielded a peak response of 15.56 towards 50 ppm NH3. The nanocomposites demonstrated fast response and recovery times of 6 s and 10 s, respectively, and displayed remarkable selectivity for NH3 gas over other tested gases. For supercapacitor applications, the electrochemical performance of the ternary NCs was evaluated using cyclic voltammetry and galvanostatic charge-discharge techniques. The composites exhibited pseudocapacitive behavior, with the capacitance reaching up to 185 F/g at 1 A/g and excellent capacitance retention of approximately 88.54% over 4000 charge-discharge cycles. The unique combination of rGO, PANI, and MnO2 nanoparticles in these ternary NCs offer synergistic advantages, showcasing their potential to address challenges in energy storage and gas sensing technologies.

Intrinsically Conducting Polymer Composites as Active Masses in Supercapacitors

Intrinsically conducting polymers ICPs can be combined with further electrochemically active materials into composites for use as active masses in supercapacitor electrodes. Typical examples are inspected with particular attention to the various roles played by the constituents of the composites and to conceivable synergistic effects. Stability of composite electrode materials, as an essential property for practical application, is addressed, taking into account the observed causes and effects of materials degradation.

In Situ Growth of MnO2 Nanosheets on a Graphite Flake as an Effective Binder-Free Electrode for High-Performance Supercapacitors

In this work, manganese dioxide (MnO2) nanosheets in situ loaded on a high-purity graphite flake (GF) were prepared by one-step hydrothermal deposition. It was found that the specific capacitance value of a single MnO2/GF electrode was 882 F/g at a current density of 1.0 A/g in a KOH electrolyte, and the specific capacitance retention of the MnO2/GF electrode can reach about 90.1% after 5000 charge-discharge cycles at a current density of 10 A/g. Furthermore, a MnO2/GF∥MnO2/GF symmetric supercapacitor device was fabricated with two pieces of MnO2/GF electrodes and ordinary filter paper with a 1 M KOH/PVA gel electrolyte as a separator. The single symmetric device displayed a high energy density of 64.2 Wh/kg at a power density of 400 W/kg within an applied voltage of 1.6 V, and this value was superior to those of previously reported MnO2-based systems. A tandem device consisting of a five-series tandem device (the applied voltage of a single device was 0.7 V) and a three-series tandem device (the applied voltage of a single device was 1.6 V) was prepared to drive a red light-emitting diode (LED). These findings open up application prospects for MnO2-based composite electrode materials for high-performance supercapacitors.

Status review of nickel phosphides for hybrid supercapacitors

Transition metal phosphides are a new class of materials that have attracted enormous attention as a potential electrode for supercapacitors (SCs) compared to metal oxides/hydroxides and metal sulfides due to their strong redox-active behaviour, good electrical conductivity, layered structure, low cost, and high chemical and thermal stability. Recently, several efforts have been made to develop nickel phosphides (Ni_xP_y) (NPs) for high-performance SCs. The electrochemical properties of NPs can be easily tuned by several innovative approaches, such as heteroatom doping, defect engineering, and developing a hollow architecture. The prospects of NPs as a positive electrode in hybrid SCs are summarized to understand the material's practical relevance. Finally, the challenges and perspectives are provided for the development of high-performance NPs for SCs. The thorough elucidation of the structure-property-performance relationship offers a guide for developing NP-based next-generation energy-storage devices.

Hierarchical Activated Carbon-MnO2 Composite for Wide Potential Window Asymmetric Supercapacitor Devices in Organic Electrolyte

The consumption of electrical energy grows alongside the development of global industry. Generating energy storage has become the primary focus of current research, examining supercapacitors with high power density. The primary raw material used in supercapacitor electrodes is activated carbon (AC). To improve the performance of activated carbon, we used manganese dioxide (MnO₂), which has a theoretical capacitance of up to 1370 Fg^-1. The composite-based activated carbon with a different mass of 0-20% MnO₂ was successfully introduced as the positive electrode. The asymmetric cell supercapacitors based on activated carbon as the anode delivered an excellent gravimetric capacitance, energy density, and power density of 84.28 Fg^-1, 14.88 Wh.kg^-1, and 96.68 W.kg^-1, respectively, at 1 M Et₄NBF₄, maintaining 88.88% after 1000 test cycles.

Formulation and clinical advancement of nanourchins: a novel multibranched nanoparticulate drug-delivery system

Nanourchins are multibranched nanoparticles with unique optical properties and surface spikes. Because of their unique properties, gold nanourchins have advantages over gold nanoparticles. The most used nanourchins are gold, tungsten, carbon, vanadium and sea urchins. The synthesis of various nanourchins and their clinical advancement are discussed in this review. ZFNs, TALENs and CRISPR/Cas9 are discussed to facilitate understanding of advancements in nanourchins. Nanourchins have been studied for Parkinson's disease, Alzheimer's disease and bioimaging. The synthesis of molybdenum diselenide nanourchins and their bioconjugations are also discussed. Nanourchins can be further explored to improve drug targeting and delivery. Researchers from several fields may contribute to the study of nanourchins as prospective nanocarriers with target specificity.