Yinzhu Jiang

Reversible conversion-alloying of Sb2O3 as a high-capacity, high-rate, and durable anode for sodium ion batteries.

Sodium ion batteries are attracting ever-increasing attention for the applications in large/grid scale energy storage systems. However, the research on novel Na-storage electrode materials is still in its infancy, and the cycling stability, specific capacity, and rate capability of the reported electrode materials cannot satisfy the demands of practical applications. Herein, a high performance Sb(2)O(3) anode electrochemically reacted via the reversible conversion-alloying mechanism is demonstrated for the first time. The Sb(2)O(3) anode exhibits a high capacity of 550 mAh g(-1) at 0.05 A g(-1) and 265 mAh g(-1) at 5 A g(-1). A reversible capacity of 414 mAh g(-1) at 0.5 A g(-1) is achieved after 200 stable cycles. The synergistic effect involving conversion and alloying reactions promotes stabilizing the structure of the active material and accelerating the kinetics of the reaction. The mechanism may offer a well-balanced approach for sodium storage to create high capacity and cycle-stable anode materials.

Electrostatic Spray Deposition of Porous SnO2/Graphene Anode Films and Their Enhanced Lithium-Storage Properties

Porous SnO₂/graphene composite thin films are prepared as anodes for lithium ion batteries by the electrostatic spray deposition technique. Reticular-structured SnO₂ is formed on both the nickel foam substrate and the surface of graphene sheets according to the scanning electron microscopy (SEM) results. Such an assembly mode of graphene and SnO₂ is highly beneficial to the electrochemical performance improvement by increasing the electrical conductivity and releasing the volume change of the anode. The novel engineered anode possesses 2134.3 mA h g⁻¹ of initial discharge capacity and good capacity retention of 551.0 mA h g⁻¹ up to the 100th cycle at a current density of 200 mA g⁻¹. This anode also exhibits excellent rate capability, with a reversible capacity of 507.7 mA h g⁻¹ after 100 cycles at a current density of 800 mA g⁻¹. The results demonstrate that such a film-type hybrid anode shows great potential for application in high-energy lithium-ion batteries.

Anatase TiO2 ultrathin nanobelts derived from room-temperature-synthesized titanates for fast and safe lithium storage.

Lithium-ion batteries (LIBs) are promising energy storage devices for portable electronics, electric vehicles, and power-grid applications. It is highly desirable yet challenging to develop a simple and scalable method for constructions of sustainable materials for fast and safe LIBs. Herein, we exploit a novel and scalable route to synthesize ultrathin nanobelts of anatase TiO2, which is resource abundant and is eligible for safe anodes in LIBs. The achieved ultrathin nanobelts demonstrate outstanding performances for lithium storage because of the unique nanoarchitecture and appropriate composition. Unlike conventional alkali-hydrothermal approaches to hydrogen titanates, the present room temperature alkaline-free wet chemistry strategy guarantees the ultrathin thickness for the resultant titanate nanobelts. The anatase TiO2 ultrathin nanobelts were achieved simply by a subsequent calcination in air. The synthesis route is convenient for metal decoration and also for fabricating thin films of one/three dimensional arrays on various substrates at low temperatures, in absence of any seed layers.

In situ growth of FeS microsheet networks with enhanced electrochemical performance for lithium-ion batteries

A facile solution-based approach has been developed for the preparation of mackinawite FeS microsheet networks directly on Fe foil. It is found that sulfur sources significantly impact the uniformity and purity of the products, while ethylenediamine as a strong donor ligand plays an important role in the formation of FeS microsheet networks. For comparison, numerous FeS microspheres are obtained in the absence of ethylenediamine. The FeS microsheet networks deliver a promising Li storage capacity (772 mA h g−1 at the 1st cycle and 697 mA h g−1 at the 20th cycle), much higher than that of the FeS microspheres. The enhanced electrochemical performance of the FeS microsheet networks can be attributed to their layered structure and unique morphology, which possess a larger electrode–electrolyte contact area, shorter diffusion length of the ions and easier transportation of the electrons.

Origin of room temperature ferromagnetism in MgO films

We report a systematic study of the crystallinity dependence of room-temperature ferromagnetism (RTFM) in pure MgO thin films prepared by pulsed laser deposition. A sequential transition from ferromagnetism to diamagnetism as a function of deposition temperature is observed. All the samples deposited from room temperature (RT) to 200 °C show clear RTFM, and the magnetization decreases monotonically with the increase of the substrate temperature, whereas the MgO film grown at 300 °C shows diamagnetism behavior like bulk MgO sample. The maximum saturation magnetization of 8 emu/cm3 is obtained for the MgO film deposited at RT, which degrades dramatically after crystallization under the annealing in both vacuum and air atmosphere. Further photoluminescence and X-ray photoelectron spectroscopies reveal that the ferromagnetism in the MgO thin films is correlated directly with the Mg vacancies.

Evidence of the defect-induced ferromagnetism in Na and Co codoped ZnO

The effect of Na concentration on the room-temperature ferromagnetism in Na and Co codoped ZnO diluted magnetic semiconductor (DMSs) was investigated. The ferromagnetic state was found to be stable below 5% doping of Na due to the exchange interaction via electron trapped oxygen vacancies (F-center) coupled with the magnetic Co ions. With large Na doping of up to 10%, a sharp reduction in the magnetization was observed, showing that the oxygen vacancy mediated antiferromagnetic state becomes predominant. The observed correlation between the Na concentration, the carrier concentration, and the magnetization demonstrated the effect of the defect in controlling the ferromagnetism in the ZnO-based DMS system.

Spatially-confined lithiation–delithiation in highly dense nanocomposite anodes towards advanced lithium-ion batteries

Spatially-confined electrochemical reactions are firstly realized in a highly dense nanocomposite anode for high performance lithium ion batteries. The spatially-confined lithiation–delithiation effectively avoids inter-cluster migration and perfectly retains full structural integrity. Large reversible capacity, high rate capability and superior cycling stability are achieved simultaneously. This spatially-confined lithiation–delithiation offers novel insight to enhance cycling performance of high capacity anode materials.

Synthesis and characterization of volatile metal β-diketonate chelates of M(DPM)n (M=Ce, Gd, Y, Zr, n=3,4) used as precursors for MOCVD

Abstract High pure Ce(DPM) 4 , Gd(DPM) 3 , Y(DPM) 3 and Zr(DPM) 4 (DPM=dipivaloylmethanate=2,2,6,6-tetramethyl-3,5-heptanedionato) powders were successfully synthesized from inorganic salts and HDPM in ethanol/aqueous solution followed by recrystallization from toluene. Freshly prepared samples have been characterized by elemental analysis, X-ray diffraction, thermogravimetry-differential thermal analysis, nuclear magnetic resonance spectroscopy and fourier transform infrared spectroscopy. Aged samples, obtained by exposing fresh ones into air for 30 days, were also represented. Various structures, stabilities and volatilities result from different metal atoms and coordination numbers. Those metal β-diketonate chelates are served as precursors of metalorganic chemical vapor deposition for single and multi-component oxide thin films.

Titanium dioxide nanotrees for high-capacity lithium-ion microbatteries

Li-ion microbatteries find wide applications in microdevices. It is important to develop electrode materials with high areal capacity, excellent rate capability and superior safety for microbatteries. TiO2 nanowire arrays satisfy the requirements of high areal capacity, short transport lengths and superior safety for microbatteries, but their areal/volumetric capacity is hindered by the insufficient surface area. TiO2 nanotrees can effectively eliminate these disadvantages of TiO2 nanowires; however, the electrochemical performances of TiO2 nanotrees for Li-ion microbatteries remain unexplored. It is highly desired yet challenging to construct two-dimensional TiO2 nanobranches with an ultrathin thickness and large length on nanoarrays, to maximize the surface area and structural hierarchy of electrodes. Herein, we developed a novel synthetic strategy to fabricate TiO2 nanotrees by depositing anatase/TiO2(B) mixed phase ultrathin nanobelts onto single-crystalline anatase nanowire arrays. The nanobelt branches were several nanometers in thickness and 200–260 nm in length. The growth process and the electrochemical mechanism were investigated. The unique nanoarchitecture and optimal phase structure endow the electrode with high areal capacity and rate capability, which is the best performance for TiO2 nanowire arrays ever documented. The 2nd discharge capacity of the TiO2 nanotrees at 0.1 mA cm−2 is ca. 267 μA h cm−2, corresponding to a volumetric capacity of 330 mA h cm−3. The TiO2 nanotrees have an areal capacity of 205, 141, 97 and 69 μA h cm−2 at a current density of 0.5, 2.0, 5.0 and 10.0 mA cm−2, respectively. The capacity can remain stable for 400 charge–discharge cycles at 1.0 mA cm−2. The present strategy may give hints to elegant electrode designs for energy applications.

SnS2 Nanowall Arrays toward High-Performance Sodium Storage

Cost-effective sodium ion batteries (SIBs) are emerging as a desirable alternative choice to lithium ion batteries in terms of application in large-scale energy storage devices. SnS2 is regarded as a potential anode material for SIBs because of its unique layered structure and high theoretical specific capacity. However, the development of SnS2 was hindered by the sluggish kinetics of the diffusion process and the inevitable volume change during repeated sodiation-desodiation processes. In this work, SnS2 with a unique nanowall array (NWA) structure is fabricated by one-step pulsed spray evaporation chemical vapor deposition (PSE-CVD), which could be used directly as binder-free and carbon-free anodes for SIBs. The SnS2 NWA electrode achieves a high reversible capacity of 576 mAh g-1 at 500 mA g-1 and enhanced cycling stability. Attractively, an excellent rate capability is demonstrated with ∼370 mAh g-1 at 5 A g-1, corresponding to a capacity retention of 64.2% at 500 mA g-1. The superior sodium storage capability of the SnS2 NWA electrode could be attributed to outstanding electrode design and a rational growth process, which favor fast electron and Na-ion transport, as well as provide steady structure for elongated cycling.