Showing papers by "Xiaojian Wang published in 2013"

High Energy Density Metal-Air Batteries: A Review

Abstract: In the last few decades, there are some exciting developments in the field of lithium (Li)-ion batteries from small portable devices to large power system such as electric vehicles (EVs). However, the maximum energy density of lithium-ion batteries is insufficient for the extended range of EVs propulsion. On the other hand, metal-air batteries have a greater power storage capacity, a few times more than the best performing lithium-ion batteries. Mechanically rechargeable zinc (Zn)-, magnesium (Mg)-, and aluminum (Al)-air batteries are receiving increasing attention, due to the advantages of using safe, low cost and abundant materials. If successfully developed, these batteries could provide an energy source for EVs comparing that of gasoline in terms of usable energy density. Nevertheless, there are still numerous scientific and technical challenges that must be overcome, if this alluring promise can be turned into reality. This paper provides a comprehensive overview of recent advances and challenges of metal air batteries from various elements, including air cathode, electrolyte, and anode. In addition, this review outlines the fundamental principles and understanding of the electrochemical reactions in the areas of lithium-air batteries. Finally, a summary of future research directions in the field of the metal-air batteries is provided.

Combining In Situ Synchrotron X‐Ray Diffraction and Absorption Techniques with Transmission Electron Microscopy to Study the Origin of Thermal Instability in Overcharged Cathode Materials for Lithium‐Ion Batteries

Abstract: The thermal instability of the cathode materials in lithium-ion batteries is an important safety issue, requiring the incorporation of several approaches to prevent thermal runaway and combustion. Systematic studies, using combined well-defined in situ techniques, are crucial to obtaining in-depth understanding of the structural origin of this thermal instability in overcharged cathode materials. Here time-resolved X-ray diffraction, X-ray absorption, mass spectroscopy, and high-resolution transmission electron microscopy during heating are combined to detail the structural changes in overcharged LixNi0.8Co0.15Al0.05O2 and LixNi1/3Co1/3Mn1/3O2 cathode materials. By employing these several techniques in concert, various aspects of the structural changes are investigated in these two materials at an overcharged state; these include differences in phase-distribution after overcharge, phase nucleation and propagation during heating, the preferred atomic sites and migration paths of Ni, Co, and Mn, and their individual contributions to thermal stability, together with measuring the oxygen release that accompanies these structural changes. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.

Mesoporous Titanium Zirconium Oxide Nanospheres with Potential for Drug Delivery Applications

Abstract: Mesoporous titanium zirconium (TiZr) oxide nanospheres with variable Ti to Zr ratios were synthesized using sol–gel chemistry followed by solvothermal treatment. These oxide nanospheres exhibited similar diameters (∼360 nm), high surface areas (from 237 ± 2 to 419 ± 4 m2 g–1), and uniform pore diameters (∼3.7 nm). Three drugs, ibuprofen, dexamethasone, and erythromycin, were loaded into the TiZr oxide nanospheres. The TiZr oxide nanospheres exhibited a high loading capacity, up to 719 mg g–1, and sustained release profiles in phosphate buffered saline (PBS) at pH 7.4. The mesoporous TiZr oxide nanospheres also exhibited hydrolytic stability, as evidenced by the retention of the integrity of the mesostructures after drug release in PBS for 21 days.