Zhen-Dong Huang

High energy density rechargeable magnesium battery using earth-abundant and non-toxic elements.

Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO4 demonstrates a high reversible capacity exceeding 300 mAh·g−1 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO4 with a magnesium bis(trifluoromethylsulfonyl)imide–triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems.

Facile synthesis of shape-controlled graphene–polyaniline composites for high performance supercapacitor electrode materials

Graphene–polyaniline (PANI) nanocomposites with different morphologies were successfully fabricated by an effective one-step hydrothermal method. The morphologies of PANI could be controlled from nanowires to nanocones by adjusting the amount of aniline with the assistance of an ultrasonication process. By taking the advantages of the high conductivity of graphene and the pseudocapacitance of PANI, graphene–PANI composites were used as an example for the application to the supercapacitor electrode materials. The cyclic voltammograms (CV) and galvanostatic charge–discharge measurements demonstrate that the graphene–PANI shows excellent electrochemical properties. The graphene–PANI nanowire composite (724.6 F g−1) exhibited higher specific capacitance than that of the graphene–PANI nanocone composite (602.5 F g−1) at a current density of 1.0 A g−1. Furthermore, the graphene–PANI nanowire composite exhibited outstanding capacitive performance with a high specific capacitance of 957.1 F g−1 at 2 mV s−1 and a high cycle reversibility of 90% after charge–discharge 1000 cycles. The improved electrochemical properties of the graphene–PANI nanocomposites suggest their promising applications to high-performance supercapacitors.

Solution-processed copper nanowire flexible transparent electrodes with PEDOT:PSS as binder, protector and oxide-layer scavenger for polymer solar cells

The easy oxidation and surface roughness of Cu nanowire (NW) films are the main bottlenecks for their usage in transparent conductive electrodes (TCEs). Herein, we have developed a facile and scaled-up solution route to prepare Cu NW-based TCEs by embedding Cu NWs into pre-coated smooth poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films on poly(ethylene terephthalate) (PET) substrates. The so obtained Cu NW-PEDOT:PSS/PET films have low surface roughness (∼70 nm in height), high stability toward oxidation and good flexibility. The optimal TCEs show a typical sheet resistance of 15 Ω·sq−1 at high transparency (76% at λ = 550 nm) and have been used successfully to make polymer (poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester) solar cells, giving an efficiency of 1.4%. The overall properties of Cu NW-PEDOT:PSS/PET films demonstrate their potential application as a replacement for indium tin oxide in flexible solar cells.

Synthesis of shape-controlled NiO–graphene nanocomposites with enhanced supercapacitive properties

Flowerlike and polyhedral NiO–graphene nanocomposites have been successfully synthesized using a facile hydrothermal method. The formation mechanism of the two nanocomposites with different morphologies has been studied. The resulting products are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopic analysis (XPS), thermogravimetry (TG), and the Brunauer–Emmett–Teller (BET) method. The prepared NiO–graphene nanocomposites with different shapes can be used for supercapacitor electrode materials. Through electrochemical tests, the flowerlike NiO–graphene composite shows higher specific capacitance than that of the polyhedral one with a specific capacitance as high as 500 F g−1 at a scan rate of 5 mV s−1 while the polyhedral NiO–graphene composite delivers better long-term cycle stability with 84% specific capacitance remaining after 3000 cycles in a 1 M KOH electrolyte.

The synthesis of shape-controlled α-MoO3/graphene nanocomposites for high performance supercapacitors

Novel nanoflake-like and nanobelt-like α-MoO3/graphene nanocomposites were synthesized by a facile hydrothermal method through tailoring the content of Mo source. The formation mechanisms of α-MoO3/graphene nanocomposites with different morphologies has been investigated. As a model, the α-MoO3/graphene nanocomposites were studied for electrochemical energy storage supercapacitor devices. The results showed that α-MoO3 nanoflakes/graphene displayed better supercapacitive performances than that of α-MoO3 nanobelts/graphene, arising from the structural superiority and optimum compositions. The best composite exhibited a high specific capacitance (up to 360 F g−1) at a current density of 0.2 A g−1, good rate capability, and a nearly 100% long-term cycle stability. This study provided a facile and optimal experimental design to prepare α-MoO3/graphene composite materials which act as promising electrode materials for high-performance supercapacitors.

MgFePO4F as a feasible cathode material for magnesium batteries

A stoichiometric MgFePO4F (MFPF) is synthesised by using a solid-state carbothermal method. Its monoclinic framework, possessing an entire cationic mixing of Mg2+ and Fe2+, is validated via both crystal structure analysis and simulation. Interestingly, MFPF exhibits a relatively high potential (∼2.6 V vs. Mg/Mg2+) and good cyclic stability with an encouraging capacity (∼53 mA h g−1), bringing MFPF to the fore as a promising cathode material for magnesium batteries.

Copper Mesh Templated by Breath-Figure Polymer Films as Flexible Transparent Electrodes for Organic Photovoltaic Devices

UNLABELLED Metal mesh is a significant candidate of flexible transparent electrodes to substitute the current state-of-the-art material indium tin oxide (ITO) for future flexible electronics. However, there remains a challenge to fabricate metal mesh with order patterns by a bottom-up approach. In this work, high-quality Cu mesh transparent electrodes with ordered pore arrays are prepared by using breath-figure polymer films as template. The optimal Cu mesh films present a sheet resistance of 28.7 Ω·sq(-1) at a transparency of 83.5%. The work function of Cu mesh electrode is tuned from 4.6 to 5.1 eV by Ag deposition and the following short-time UV-ozone treatment, matching well with the PEDOT PSS (5.2 eV) hole extraction layer. The modified Cu mesh electrodes show remarkable potential as a substitute of ITO/PET in the flexible OPV and OLED devices. The OPV cells constructed on our Cu mesh electrodes present a similar power conversion efficiency of 2.04% as those on ITO/PET electrodes. The flexible OLED prototype devices can achieve a brightness of 10 000 cd at an operation voltage of 8 V.

Vanadium phosphate as a promising high-voltage magnesium ion (de)-intercalation cathode host

Magnesium batteries (MBs) have been considered as one of the most promising safe and low cost energy storage systems. Herein, vanadium phosphates, prepared by the electrochemical de-lithiation of Li3V2(PO4)3, are investigated as a high-voltage cathode host for Mg2+ (de)-intercalation. The reversible (de)-intercalation of Mg2+ into (from) the host structure of V2(PO4)3 are verified by the comprehensive analysis of the results from the electrochemical tests, synchrotron X-ray diffraction and absorption, and inductively coupled plasma measurements. Its exceptional high average working voltage (∼3.0 V vs. Mg/Mg2+) surpasses other reported values of cathode hosts for MBs.

Towards free-standing MoS2 nanosheet electrocatalysts supported and enhanced by N-doped CNT–graphene foam for hydrogen evolution reaction

Large-scale free-standing porous carbon-based catalyst supports are critically needed for the hydrogen evolution reaction (HER) in view of their practical application. In this work, MoS2 nanosheets were uniformly deposited onto N-doped carbon nanotube–graphene (N-CNT–G) hybrids, forming a three-dimensional (3D) free-standing architecture. The designed 3D hybrid materials exposed the MoS2 nanosheet catalyst on the one-dimensional CNTs and there was facilitated ion transportation because of the porous graphene foam, and these 3D hybrid materials were used as electrocatalysts for HER directly without any transferring process. Moreover, N doping decreased the overpotential to 0.08 V, which increased the stability and promoted the catalytic activity, providing a facile route to design advanced high-performance HER catalysts towards a free-standing configuration.

Hierarchical dispersed multi-phase nickel cobalt oxide mesoporous thorn microspheres as superior rate anode materials for lithium ion batteries

Hierarchical nickel cobalt oxide (NCO) microspheres comprised of nanoscale mesoporous thorn arrays are developed as superior rate high capacity anodes in this work, i.e. 1063.3 and 860 mA h g−1 at 180 and 4500 mA g−1, respectively. Stoichiometric urea serves as a self-template to favor the self-assembly of well-organized NiCo(OH)2CO3 thorn microsphere precursors under an optimized hydrothermal reaction. The dispersed multi-phase hybrid crystal structure and the favorable specific surface area obtained during the controlled pyrolysis of NiCo(OH)2CO3 microspheres markedly promote the cyclic stability of the single phase Ni1.5Co1.5O4.