Molecular Dynamics Simulations of Li Insertion in a Nanocrystalline V 2 O 5 Thin Film Cathode
The behavior of lithium ion diffusion from an electrolyte into a polycrystalline layered cathode has been studied using molecular dynamics computer simulations. Lithium silicate glass was the model solid electrolyte whilethe cathode was a nanocrystalline vanadia with amorphous V 2 O 5 intergranular films (IGF) between the crystals. Nanosized V 2 O 5 crystals were aligned with their (001) planes parallel to electrolyte/cathode interface, rotated 90° from each other around this interface's normal in order to present two different orientations between the crystal planes for lithium intercalation via the amorphous vanadia IGF. A series of nanocrystalline vanadia cathodes with different IGF thicknesses was simulated to examine the effects of the IGF thickness on lithium transport into the cathodes. Results showed preferential diffusion of Li from the electrolyte into the amorphous vanadia IGF, with some of those Li diffusing into the crystalline V 2 O 5 from the IGF. Results also showed easier lithium diffusion from the IGF into the V 2 O 5 crystal along the (010) direction than along the (100) direction. Additionally, an optimum IGF thickness of 2.5-3.0 nm is suggested as being neither too thick to decrease the capacity of the cathode nor too thin to impede the transport of lithium from glassy electrolyte into the cathode.
Effects of Synthesis Methods on Li1 + x V3O8 as Cathodes in Lithium-Ion Batteries
Lithiated vanadium oxides Li 1+x V 3 O 8 as promising cathode materials for secondary lithium batteries are prepared using several methods. The crystalline phase is characterized by powder X-ray diffraction, and the morphology is observed by scanning electron microscopy. The electrochemical properties of synthesized samples are systematically investigated by galvanostatic charge and discharge. The maximal initial specific discharge capacity belongs to the material produced by the hydrothermal route, which can attain 338 mAh g -1 at a current density of 50 mA g -1 . The aqueous precipitation route produced a sample that exhibits the best cycling behavior among these lithium trivanadate samples, which keeps 226 mAh g -1 as 92% of its initial capacity after 20 cycles and preserves a high charge-discharge efficiency of around 99%.
Selective etching of InP in NaF solution
Abstract The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [0 1 1] and [ 0 1 ¯ 1 ], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [1 1 1]B and [ 1 1 ¯ 1 ¯ ]B. Both are due to the selective etching of F− ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III–V compound semiconductors for photonic band gap materials.