Xing-Long Wu

High-quality Prussian blue crystals as superior cathode materials for room-temperature sodium-ion batteries

High-quality Prussian blue crystals with a small number of vacancies and a low water content are obtained by employing Na4Fe(CN)6 as the single iron-source precursor. The high-quality Prussian blue shows high specific capacity and remarkable cycling stability as the cathode material for Na-ion batteries because of its excellent ion storage capability and impressive structure stability.

Synthesis of CuO/graphene nanocomposite as a high-performance anode material for lithium-ion batteries

An optimized nanostructure design for electrode materials for high-performance lithium-ion batteries was realized by introducing three-dimensional (3D) graphene networks into transition metal oxide nanomicrostructures. A CuO/graphene composite was selected as a typical example of the optimized design. Self-assembled CuO and CuO/graphene urchin-like structures have been successfully synthesized by a simple solution method and investigated with SEM, TEM, XRD, and electrochemical measurements. The CuO/graphene nanocomposite exhibits a remarkably enhanced cycling performance and rate performance compared with pure CuO urchin-like structure when being used as anode materials in lithium-ion batteries. During all the 100 discharge-charge cycles under a current density of 65 mA g−1, the CuO/graphene electrode can stably deliver a reversible capacity of ca. 600 mA h g−1. At a high current density of 6400 mA g−1, the specific charge capacity of the CuO/graphene nanocomposite is still as high as 150 mA h g−1, which is three times larger than that of graphene (48 mA h g−1), while that of CuO is nearly null under the same current density. The enhancement of the electrochemical performance could be attributed to the 3D electrically conductive networks of graphene as well as the unique nanomicrostructure of the CuO/graphene nanocomposite in which the CuO nanomicroflowers are enwrapped by a thin layer of graphene as an elastic buffer.

Self-Wound Composite Nanomembranes as Electrode Materials for Lithium Ion Batteries

www.MaterialsViews.com C O M M U Self-Wound Composite Nanomembranes as Electrode Materials for Lithium Ion Batteries N IC A T By Heng-Xing Ji , Xing-Long Wu , Li-Zhen Fan , Cornelia Krien , Irina Fiering , Yu-Guo Guo , * Yongfeng Mei , * and Oliver G. Schmidt IO N Bending and rolling is commonly employed in nature to release strain in fi lms to maintain structure stability. Recently, rolledup nanotechnology has proven to be an intriguing approach on the micro-/nanoscale for various promising future applications and concepts. [ 1–5 ] Nanomembranes composed of various functional stacks can self wind (or roll up) into micro/nanotubes upon detaching from a holding substrate by releasing intrinsic differential strain. The deposition and process methods for nanomembranes are compatible to industrial-level technologies like e-beam evaporation, sputtering deposition and atomic layer deposition, etc., which are demanded by advanced materials used for applications. Moreover, the intrinsic strain accommodated in multi-layer nanomembranes is effi ciently released by self winding and thus offers a minimization of the system energy. [ 6 ] Such tubular and strain-relaxed structures are liable to improve the materials tolerance against stress cracking and are therefore promising candidates for increasing the stability of energy storage devices such as lithium ion batteries. Lithium ion batteries are attractive for applications ranging from electric vehicles to microchips. [ 7–10 ] One of the big challenges is strain accommodation during electrode lithiation, which would prevent the electrodes in batteries from being pulverized which causes capacity fading. [ 10–12 ] For example, transition-metal oxides and lithium alloys are attractive anode materials owing to their high theoretical charge capacity, which is several times larger than existing graphite anodes. [ 13–16 ]

A Superior Na3V2(PO4)3‐Based Nanocomposite Enhanced by Both N‐Doped Coating Carbon and Graphene as the Cathode for Sodium‐Ion Batteries

A superior Na3 V2 (PO4 )3 -based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most-common chelator, disodium ethylenediamintetraacetate [Na2 (C10 H16 N2 O8 )], as both sodium and nitrogen-doped carbon sources for the first time. 2D-reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium-ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high-rate capabilities and prolonged cycling life compared to the pristine NVP and single-carbon-modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g(-1) , which is obviously higher than 106 and 112.3 mAh g(-1) for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g(-1) even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP-based cathodes including the apparent Na diffusion coefficients and charge-transfer resistances.

A carbon-coated Li3V2(PO4)3 cathode material with an enhanced high-rate capability and long lifespan for lithium-ion batteries

A facile sol–gel approach combined with a carbon-coating technique via high-temperature thermally decomposing C2H2 has been developed for the synthesis of a Li3V2(PO4)3/C (LVP/C) cathode material employing the biomass of phytic acid as an eco-friendly phosphorus source. The effects of the carbon-coating on the structural, morphological and electrochemical properties of LVP have been investigated. Compared with pristine LVP, the LVP/C composite presents a higher discharge capacity of 127 mA h g−1 at 0.1 C, better rate capability and long-term cyclability in the voltage range of 3.0–4.3 V. Even at a high charge–discharge rate of 5 C, it can still deliver a reversible capacity of 107 mA h g−1 over 400 cycles without obvious fading, demonstrating great potential as a superior cathode material for lithium-ion batteries.

Separation of the Schottky barrier and polarization effects on the photocurrent of Pt sandwiched Pb(Zr0.20Ti0.80)O3 films

Photoelectric behavior of Pt sandwiched Pb(Zr0.20Ti0.80)TiO3 (PZT) films deposited on Pt∕Ti∕SiO2∕Si substrates by a sol-gel method was investigated by testing the short-circuit photocurrent under different film thicknesses. By poling the films step by step with increased magnitude and alternated direction of the dc electric field, interesting photoelectric behavior was found when the PZT films were in virgin or poled up/down state. The photocurrent was also strongly dependent on the film thickness. A simple model was proposed to separate the effects of interface Schottky barriers and bulk ferroelectric polarization of the film on the photocurrent of the Pt/PZT/Pt structure.

Constructing the optimal conductive network in MnO-based nanohybrids as high-rate and long-life anode materials for lithium-ion batteries

Among the transition metal oxides as anode materials for lithium ion batteries (LIBs), the MnO material should be the most promising one due to its many merits mainly relatively low voltage hysteresis. However, it still suffers from inferior rate capabilities and poor cycle life arising from kinetic limitations, drastic volume changes and severe agglomeration of active MnO particulates during cycling. In this paper, by integrating the typical strategies of improving the electrochemical properties of transition metal oxides, we had rationally designed and successfully prepared one superior MnO-based nanohybrid (MnO@C/RGO), in which carbon-coated MnO nanoparticles (MnO@C NPs) were electrically connected by three-dimensional conductive networks composed of flexible graphene nanosheets. Electrochemical tests demonstrated that, the MnO@C/RGO nanohybrid not only showed the best Li storage performance in comparison with the commercial MnO material, MnO@C NPs and carbon nanotube enhanced MnO@C NPs, but also exhibited much improved electrochemical properties compared with most of the previously reported MnO-based materials. The superior electrochemical properties of the MnO@C/RGO nanohybrid included a high specific capacity (up to 847 mA h g−1 at 80 mA g−1), excellent high-rate capabilities (for example, delivering 451 mA h g−1 at a very high current density of 7.6 A g−1) and long cycle life (800 cycles without capacity decay). More importantly, for the first time, we had achieved the discharging/charging of MnO-based materials without capacity increase even after 500 cycles by adjusting the voltage range, making the MnO@C/RGO nanohybrid more possible to be a really practical anode material for LIBs.

Preparation and li storage properties of hierarchical porous carbon fibers derived from alginic acid.

One-dimensional (1D) hierarchical porous carbon fibers (HPCFs) have been prepared by controlled carbonization of alginic acid fibers and investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nitrogen adsorption-desorption isotherms, and electrochemical tests toward lithium storage. The as-obtained HPCFs consist of a 3D network of nanosized carbon particles with diameters less than 10 nm and exhibit a hierarchical porous architecture composed of both micropores and mesopores. Electrochemical measurements show that HPCFs exhibit excellent rate capability and capacity retention compared with commercial graphite when employed as anode materials for lithium-ion batteries. At the discharge/charge rate of 45 C, the reversible capacity of HPCFs is still as high as 80 mA h g(-1) even after 1500 cycles, which is about five times larger than that of commercial graphite anode. The much improved electrochemical performances could be attributed to the nanosized building blocks, the hierarchical porous structure, and the 1D morphology of HPCFs.

Anodic alumina template on Au/Si substrate and preparation of CdS nanowires

Abstract A layer of thin gold film was sandwiched between a silicon substrate and an Al film to form the Al/Au/Si structure. Subsequent anodization leads to formation of a Si-based anodic aluminum oxide (AAO) template (AAO/Au/Si structure) with ordered nanopores. This kind of template has unique electrodeposition properties and can bond well with the deposited materials. The anodic process of the Al/Au/Si structure was investigated in detail by in situ monitoring the current–time curve. As an application, CdS nanowires were fabricated on the silicon substrate using this kind of AAO templates. Light-emitting property from the CdS nanowires was observed. This kind of Si-based light-emitting nanowires are expected to have practical applications in optoelectronic integration.

Pr3+ photoluminescence in ferroelectric (Ba0.77Ca0.23)TiO3 ceramics: Sensitive to polarization and phase transitions

We reported in this study that the photoluminescence (PL) spectra of (Ba0.77Ca0.23)TiO3:Pr3+ were sensitive to both polarization and phase transitions of the ferroelectric ceramics. Comparing with the unpoled sample, all the red emissions under different temperatures of 50to300K increase about 30% for the poled 0.1mol% Pr3+-doped ceramic. Obvious peaks around 100K for the red and blue emission intensities of Pr3+ ions were found when the ceramic passed through the orthorhombic-tetragonal phase transition, and a step decrease in the red emission intensity occurs around the tetragonal-cubic transition. Both polarization and phase transition effects on the Pr3+ PL were ascribed to local environmental changes of Pr3+ ions in the (Ba0.77Ca0.23)TiO3 ceramic.