Hao Chen

Bio: Hao Chen is an academic researcher from Chongqing University. The author has contributed to research in topics: Supercapacitor & Electrode. The author has an hindex of 16, co-authored 25 publications receiving 848 citations. Previous affiliations of Hao Chen include Dalian University of Technology.

Hierarchical Cu2O/CuO/Co3O4 core-shell nanowires: synthesis and electrochemical properties.

Abstract: We prepared hierarchical Cu2O/CuO/Co3O4 core–shell nanowires (NWs) via a facile chemical deposition method followed by calcination for use as the electrode of supercapacitors. The Cu2O/CuO/Co3O4 electrode showed a specific capacitance of 318 F g �1 at a current density of 0.5 A g �1 . 80% of the original specific capacitance was retained after 3000 cycles at a current density of 5 A g �1 . An asymmetric supercapacitor cell using Cu2O/CuO/Co3O4 NWs as the positive electrode and activated graphene as the negative electrode exhibited a maximum energy density of 12 Wh kg �1 . The electrochemical properties of the electrode were strongly related to the hierarchical nanostructure, which not only provided rich active sites but also shortened ion transport pathways.

Construction of unique cupric oxide–manganese dioxide core–shell arrays on a copper grid for high-performance supercapacitors

Abstract: Unique CuO@MnO2 core–shell nanostructures on a copper grid have been prepared on a large scale by quick wet etching and hydrothermal deposition methods for advanced binder-free supercapacitor electrodes. The CuO@MnO2 nanostructures are regulated and controlled on the basis of time-dependent experiments. This core–shell nanostructure displays a very high specific capacitance (343.9 F g−1 at a current density of 0.25 A g−1), remarkable cycling stability (83.1% retention after 12 000 cycles) and a good rate capability (70.5% of the original capacitance). These perfect electrochemical properties are attributed to synergic interaction of each component. In addition, the asymmetric supercapacitor exhibits a high energy density of 29.9 W h kg−1 at a power density of 269.6 W kg−1. These findings make it attractive that the CuO@MnO2 core–shell nanostructure on a copper grid is a promising electrode material for electrochemical supercapacitors.

Low-cost high-performance asymmetric supercapacitors based on Co2AlO4@MnO2 nanosheets and Fe3O4 nanoflakes

Abstract: The development of portable and wearable electronics has promoted the increasing demand for high-performance power sources with high energy/power density, low cost, lightweight, as well as ultrathin and flexible features. Herein, a low-cost high-performance flexible asymmetric supercapacitor (ASC) with Co2AlO4@MnO2 nanosheets and Fe3O4 nanoflakes grown on nickel foam is designed and fabricated. The as-designed ASC device with an extended operating voltage window of 1.6 V achieves a specific capacitance of 99.1 F g−1 at a current density of 2 A g−1 with a maximum energy density of 35.3 W h kg−1 and very long-term cycling stability (92.4% capacitance after 5000 cycles).

Review of supercapacitors: Materials and devices

Abstract: Supercapacitors have gained a lot of attention due to their unique features like high power, long cycle life and environment-friendly nature. They act as a link for energy-power difference between a traditional capacitor (having high power) and fuel cells/batteries (having high energy storage). In this perspective, a worldwide research has been reported to address this and rapid progress has been achieved in the advancement of fundamental as well as the applied aspects of supercapacitors. Here, a concise description of technologies and working principles of different materials utilized for supercapacitors has been provided. The main focus has been on materials like carbon-based nanomaterials, metal oxides, conducting polymers and their nanocomposites along with some novel materials like metal-organic frameworks, MXenes, metal nitrides, covalent organic frameworks and black phosphorus. The performance of nanocomposites has been analysed by parameters like energy, capacitance, power, cyclic performance and rate capability. Some of the latest supercapacitors such as electrochromic supercapacitor, battery-supercapacitor hybrid device, electrochemical flow capacitor, alternating current line filtering capacitor, micro-supercapacitor, photo-supercapacitor, thermally chargeable supercapacitor, self-healing supercapacitor, piezoelectric and shape memory supercapacitor have also been discussed. This review covers the up-to-date progress achieved in novel materials for supercapacitor electrodes. The latest fabricated symmetric/asymmetric supercapacitors have also been reported.

MnO2-based nanostructures for high-performance supercapacitors

Abstract: MnO2-based materials have been intensively investigated for use in pseudocapacitors due to their high theoretical specific capacitance, good chemical and thermal stability, natural abundance, environmental benignity and low cost. In this review, several main factors that affect the electrochemical properties of MnO2-based electrodes are presented. Various strategic design and synthetic methods of MnO2-based electrode materials for enhanced electrochemical performance are highlighted and summarized. Finally, the challenges and future directions toward the development of MnO2-based nanostructured electrode materials for high performance supercapacitors (SCs) are discussed.

Review of Hybrid Ion Capacitors: From Aqueous to Lithium to Sodium.

Abstract: In this critical Review we focus on the evolution of the hybrid ion capacitor (HIC) from its early embodiments to its modern form, focusing on the key outstanding scientific and technological questions that necessitate further in-depth study. It may be argued that HICs began as aqueous systems, based on a Faradaic oxide positive electrode (e.g., Co3O4, RuOx) and an activated carbon ion-adsorption negative electrode. In these early embodiments HICs were meant to compete directly with electrical double layer capacitors (EDLCs), rather than with the much higher energy secondary batteries. The HIC design then evolved to be based on a wide voltage (∼4.2 V) carbonate-based battery electrolyte, using an insertion titanium oxide compound anode (Li4Ti5O12, LixTi5O12) versus a Li ion adsorption porous carbon cathode. The modern Na and Li architectures contain a diverse range of nanostructured materials in both electrodes, including TiO2, Li7Ti5O12, Li4Ti5O12, Na6LiTi5O12, Na2Ti3O7, graphene, hard carbon, soft carbo...

Mixed Metal Sulfides for Electrochemical Energy Storage and Conversion

Abstract: Mixed metal sulfides (MMSs) have attracted increased attention as promising electrode materials for electrochemical energy storage and conversion systems including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), hybrid supercapacitors (HSCs), metal–air batteries (MABs), and water splitting. Compared with monometal sulfides, MMSs exhibit greatly enhanced electrochemical performance, which is largely originated from their higher electronic conductivity and richer redox reactions. In this review, recent progresses in the rational design and synthesis of diverse MMS-based micro/nanostructures with controlled morphologies, sizes, and compositions for LIBs, SIBs, HSCs, MABs, and water splitting are summarized. In particular, nanostructuring, synthesis of nanocomposites with carbonaceous materials and fabrication of 3D MMS-based electrodes are demonstrated to be three effective approaches for improving the electrochemical performance of MMS-based electrode materials. Furthermore, some potential challenges as well as prospects are discussed to further advance the development of MMS-based electrode materials for next-generation electrochemical energy storage and conversion systems.

Nanostructured Transition Metal Oxides for Aqueous Hybrid Electrochemical Supercapacitors

Abstract: In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the capacitance of the metal oxides and the cell voltage of the supercapacitor. It is shown that the cell voltage of an electrochemical supercapacitor can be increased significantly with the use of hybrid systems. The most relevant associations are Fe3O4 or activated carbon as the negative electrode and MnO2 as the positive. The cell voltage of the Fe3O4/MnO2 device is 1.8 V and this value was increased to 2.2 V by using activated carbon instead of Fe3O4. These two systems have shown superior behavior compared to a symmetric MnO2/MnO2 device which only works within a 1 V potential window in aqueous K2SO4. Furthermore, the activated carbon/MnO2 hybrid device exhibits a real power density of 605 W/kg (maximum power density =19.0 kW/kg) with an energy density of 17.3 Wh/kg. These values compete well with those of standard electrochemical double layer capacitors working in organic electrolytes.