Dongliang Chao

A New Type of Porous Graphite Foams and Their Integrated Composites with Oxide/Polymer Core/Shell Nanowires for Supercapacitors: Structural Design, Fabrication, and Full Supercapacitor Demonstrations

We attempt to meet the general design requirements for high-performance supercapacitor electrodes by combining the strategies of lightweight substrate, porous nanostructure design, and conductivity modification. We fabricate a new type of 3D porous and thin graphite foams (GF) and use as the light and conductive substrates for the growth of metal oxide core/shell nanowire arrays to form integrated electrodes. The nanowire core is Co3O4, and the shell is a composite of conducting polymer (poly(3,4-ethylenedioxythiophene), PEDOT) and metal oxide (MnO2). To show the advantage of this integrated electrode design (viz., GF + Co3O4/PEDOT-MnO2 core/shell nanowire arrays), three other different less-integrated electrodes are also prepared for comparison. Full supercapacitor devices based on the GF + Co3O4/PEDOT-MnO2 as positive electrodes exhibit the best performance compared to other three counterparts due to an optimal design of structure and a synergistic effect.

A V2O5/Conductive‐Polymer Core/Shell Nanobelt Array on Three‐Dimensional Graphite Foam: A High‐Rate, Ultrastable, and Freestanding Cathode for Lithium‐Ion Batteries

A thin polymer shell helps V2O5 a lot. Short V2O5 nanobelts are grown directly on 3D graphite foam as a lithium-ion battery (LIB) cathode material. A further coating of a poly(3,4-ethylenedioxythiophene) (PEDOT) thin shell is the key to the high performance. An excellent high-rate capability and ultrastable cycling up to 1000 cycles are demonstrated.

Array of nanosheets render ultrafast and high-capacity Na-ion storage by tunable pseudocapacitance

Sodium-ion batteries are a potentially low-cost and safe alternative to the prevailing lithium-ion battery technology. However, it is a great challenge to achieve fast charging and high power density for most sodium-ion electrodes because of the sluggish sodiation kinetics. Here we demonstrate a high-capacity and high-rate sodium-ion anode based on ultrathin layered tin(II) sulfide nanostructures, in which a maximized extrinsic pseudocapacitance contribution is identified and verified by kinetics analysis. The graphene foam supported tin(II) sulfide nanoarray anode delivers a high reversible capacity of ∼1,100 mAh g−1 at 30 mA g−1 and ∼420 mAh g−1 at 30 A g−1, which even outperforms its lithium-ion storage performance. The surface-dominated redox reaction rendered by our tailored ultrathin tin(II) sulfide nanostructures may also work in other layered materials for high-performance sodium-ion storage.

Solution synthesis of metal oxides for electrochemical energy storage applications

This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.

Self‐Assembly of Honeycomb‐like MoS2 Nanoarchitectures Anchored into Graphene Foam for Enhanced Lithium‐Ion Storage

Honeycomb-like MoS2 nanoarchitectures anchored into 3D graphene foam are successfully fabricated as a high-performance positive electrode for enhanced Li-ion storage. The unique 3D interpenetrating honeycomb-like structure is the key to the high performance. High reversible capacity, superior high-rate capability, and excellent cycling stability are demonstrated.

All Metal Nitrides Solid‐State Asymmetric Supercapacitors

Two metal nitrides, TiN porous layers and Fe2 N nanoparticles, are grown uniformly with the assistance of atomic layer deposition on vertically aligned graphene nanosheets and used as the cathode and anode for solid-state supercapacitors, respectively. Full cells are constructed and show good flexibility, high-rate capability, and 98% capacitance retention after 20,000 cycles.

Generic Synthesis of Carbon Nanotube Branches on Metal Oxide Arrays Exhibiting Stable High‐Rate and Long‐Cycle Sodium‐Ion Storage

A new and generic strategy to construct interwoven carbon nanotube (CNT) branches on various metal oxide nanostructure arrays (exemplified by V2 O3 nanoflakes, Co3 O4 nanowires, Co3 O4 -CoTiO3 composite nanotubes, and ZnO microrods), in order to enhance their electrochemical performance, is demonstrated for the first time. In the second part, the V2 O3 /CNTs core/branch composite arrays as the host for Na(+) storage are investigated in detail. This V2 O3 /CNTs hybrid electrode achieves a reversible charge storage capacity of 612 mAh g(-1) at 0.1 A g(-1) and outstanding high-rate cycling stability (a capacity retention of 100% after 6000 cycles at 2 A g(-1) , and 70% after 10 000 cycles at 10 A g(-1) ). Kinetics analysis reveals that the Na(+) storage is a pseudocapacitive dominating process and the CNTs improve the levels of pseudocapacitive energy by providing a conductive network.

Tubular TiC fibre nanostructures as supercapacitor electrode materials with stable cycling life and wide-temperature performance

Highly active electrode materials with judicious design of nanostructure are important for the construction of high-performance electrochemical energy storage devices. In this work, we have fabricated a tubular TiC fibre cloth as an interesting type of stable supercapacitive material. Hollow microfibres of TiC are synthesized by carbothermal treatment of commercial T-shirt cotton fibres. To demonstrate the rationale of nanostructuring in energy storage, the hollow fibres are further covered by interwoven TiC nanotube branches, forming 3D tubular all-TiC hierarchical fibres with high electrical conductivity, high surface area, and high porosity. For energy storage functions, organic symmetric supercapacitors based on the hollow fibre–nanotube (HFNT) TiC cloth electrodes are assembled and thoroughly characterized. The TiC-based electrodes show very stable capacitance in long charge–discharge cycles and at different temperatures. In particular, the integrated TiC HFNT cloth electrodes show a reasonably high capacitance (185 F g−1 at 2 A g−1), better cycling stability at high-rates (e.g., 97% retention at room temperature after 150 000 cycles, and 67% at −15 °C after 50 000 cycles) than other control electrodes (e.g., pure carbon fibre cloths). It is envisaged that this 3D tubular TiC fibre cloth is also useful for solar cells and electrocatalysis.

VO2 nanoflake arrays for supercapacitor and Li-ion battery electrodes: performance enhancement by hydrogen molybdenum bronze as an efficient shell material

Hydrogen molybdenum bronze (HMB) is electrochemically deposited as a homogeneous shell on VO2 nanoflakes grown on graphene foam (GF), forming a GF + VO2/HMB integrated electrode structure. Asymmetric supercapacitors based on the GF + VO2/HMB cathode and neutral electrolyte are assembled and show enhanced performance with weaker polarization, higher specific capacitance and better cycling life than the unmodified GF + VO2 electrode. Capacitances of 485 F g−1 (2 A g−1) and 306 F g−1 (32 A g−1) are obtained because of the exceptional 3D porous architecture and conductive network. In addition, the GF + VO2/HMB electrodes are also characterized as the cathode of lithium ion batteries. Very stable capacities at rates up to 30 C are demonstrated for 500 cycles. This new type of shell material is expected to have its generic function in other metal oxide based nanostructures.

Nonaqueous Hybrid Lithium‐Ion and Sodium‐Ion Capacitors

Hybrid metal-ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery-type anode and the capacitor-type cathode. Recently, some transition-metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high-rate candidates for hybrid MIC anodes. Here, the material design strategies in Li-ion and Na-ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb2 O5 , MoO3 , etc.), which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.