Deyan He

Germanium Anode with Excellent Lithium Storage Performance in a Germanium/Lithium–Cobalt Oxide Lithium-Ion Battery

Germanium is a highly promising anode material for lithium-ion batteries as a consequence of its large theoretical specific capacity, good electrical conductivity, and fast lithium ion diffusivity. In this work, Co3O4 nanowire array fabricated on nickel foam was designed as a nanostructured current collector for Ge anode. By limiting the voltage cutoff window in an appropriate range, the obtained Ge anode exhibits excellent lithium storage performance in half- and full-cells, which can be mainly attributed to the designed nanostructured current collector with good conductivity, enough buffering space for the volume change, and shortened ionic transport length. More importantly, the assembled Ge/LiCoO2 full-cell shows a high energy density of 475 Wh/kg and a high power density of 6587 W/kg. A high capacity of 1184 mA h g(-1) for Ge anode was maintained at a current density of 5000 mA g(-1) after 150 cycles.

Facile synthesis of porous Fe3O4@C nanospheres as high-performance anode for lithium-ion battery

Uniform porous Fe3O4@C nanospheres are successfully synthesized via a facile hydrothermal method. When used as anode material for lithium-ion battery, it shows quite a good electrochemical performance. The Fe3O4@C nanosphere anode delivers a high reversible specific capacity of ∼609xa0mAh/g in 200th cycle at a current density of 200xa0mA/g. The thin coating carbon and porous structure play an important role in the improvement of electrochemical performances of Fe3O4 nanoparticles anode, which could provide void spaces for active Fe3O4 to buffer the volume expansion during the discharge/charge processes and increase the conductivity of the whole anode. Therefore, it is proved that the superior electrochemical performances makes this composite a promising candidate of anode material for lithium-ion battery.

Highly water-soluble nanocrystal powders of magnetite and maghemite coated with gluconic acid: Preparation, structure characterization, and surface coordination.

A simple method was developed to prepare highly water-soluble nanocrystal powders of magnetic iron oxides with different oxidation degree from magnetite (Fe(3)O(4)) to maghemite (γ-Fe(2)O(3)) coated with gluconic acid (GLA). X-ray diffraction and transmission electron microscopy measurements show that the products have a narrow size distribution, and the cores are inverse spinel iron oxides and completely crystallized. Vibrating sample magnetometry measurements reveal that all the samples exhibit superparamagnetic behavior at room temperature. Fourier transform infrared (FTIR) and Raman spectra were used to identify the products. It is shown that GLA molecules are immobilized on the nanoparticle surface by chemical bonding and the carboxyl is asymmetrically bound to the surface iron atom, and the vacancies in the γ-Fe(2)O(3) cores are disordered. Compared with FTIR, Raman spectrum analysis is a rapid, simple, and accurate method for identifying inverse spinel iron oxides. The chemical stability and the high solubility of the products are explained in terms of the proposed coordination modes of the surface iron atom with GLA.

Electrochemically deposited interconnected porous Co3O4 nanoflakes as anodes with excellent rate capability for lithium ion batteries

Interconnected porous Co3O4 nanoflakes were prepared on nickel foam by a simple electrochemical deposition combined with a subsequent heat treatment. The featured nanoflakes consisted of interconnected primary nanoparticles and nanopores resulting in a large specific surface area. As an anode material of lithium ion batteries, the as-prepared samples exhibited superior cyclic performance and excellent rate capacity. The discharge capacity remained at 1211 mA h g−1 after 100 cycles at a current density of 1 A g−1. Notably, after cycling at various current densities up to 5 A g−1, the capacity recovered to 1266 mA h g−1 at 0.1 A g−1.

A low-stress, elastic, and improved hardness hydrogenated amorphous carbon film

The evolution of hydrogenated amorphous carbon films with fullerene-like microstructure was investigated with a different proportion of hydrogen supply in deposition.The results showed at hydrogen flow rate of 50 sccm, the deposited films showed a lower compressive stress (lower 48.6%), higher elastic recovery (higher 19.6%, near elastic recovery rate 90%), and higher hardness (higher 7.4%) compared with the films deposited without hydrogen introduction. Structural analysis showed that the films with relatively high sp2 content and low bonded hydrogen content possessed high hardness, elastic recovery rate, and low compressive stress. It was attributed to the curved graphite microstructure, which can form three-dimensional covalently bonded network.