Shali Zhu

Crystallite Size Control and Resulting Electrochemistry of Magnetite, Fe3O4

As an environmentally benign, superparamagnetic material, magnetite (Fe 3 O 4 ) has been a topic of interest for applications ranging from drug delivery to data storage. We report here investigation of magnetite as a lithium-battery material. While Fe 3 O 4 synthesis has been widely studied, our approach afforded excellent crystallite size control without constraining media or elaborate equipment. Upon electrochemical testing, a strong correlation between performance and crystallite size was observed, resulting in a ∼ 30% capacity increase. To the best of our knowledge, this is the first study of electrochemical effects of Fe 3 O 4 crystallite size where all nanocrystalline samples were prepared using the same method.

Nanocrystalline Magnetite: Synthetic Crystallite Size Control and Resulting Magnetic and Electrochemical Properties

A synthetic strategy for magnetite (Fe 3 0 4 ) crystallite size control is reported, along with the detailed characterization and electrochemical measurements of Fe 3 O 4 samples of varying crystallite sizes. Nanocrystalline Fe 3 O 4 is prepared by coprecipitation induced by triethylamine from aqueous iron(II) and iron(III) chloride solutions of varying concentrations. Variation of the iron(II) and iron(III) concentrations results in crystallite size control of the Fe 3 O 4 products. Materials characterization of the Fe 3 0 4 samples is reported, including X-ray diffraction, transmission electron microscopy, particle size, and saturation magnetization results. A strong correlation between discharge capacity and voltage recovery behavior vs magnetite crystallite size was observed when tested as an electrode material in lithium electrochemical cells.

Synthesis and Electrochemistry of Silver Hollandite

The electrochemical study of silver hollandite is presented, establishing the promise of this material for future secondary battery applications. A low temperature reflux-based strategy for the synthesis of pure silver hollandite is described, where an enhancement in silver loading was achieved relative to other low temperature methods.

Electrodes for Nonaqueous Oxygen Reduction Based upon Conductive Polymer-Silver Composites

Progress toward the development of current collector-conductive polymer-silver (cc-cp-Ag) composite cathodes for nonaqueous metal air batteries is presented here, where the contribution of each component toward the overall oxygen reduction activity of the multifunctional cc-cp-Ag composite is studied. First, the effect of the chemical identity of the current collector (carbon versus gold) on the electrochemical reduction of oxygen is examined, accompanied by a conductive polymer deposition study. These two studies together demonstrate that a conductive polymer deposit can eliminate any competitive electrochemistry due to the current collector. Second, the role of the conductive polymer in improving physical strength of the composite electrode is evaluated using an electrode durability test. Third, a systematic study of the Ag loading effect is undertaken to determine the minimum silver loading required for significant enhancement in oxygen reduction activity.

Metal–Air Electrochemical Cells: Silver–Polymer–Carbon Composite Air Electrodes

Reported herein is the study of the preparation, characterization, and electrochemical activity of a silver-polymer-carbon composite electrode in a nonaqueous cell. An enhanced oxygen reduction activity for the composite electrode in a nonaqueous, aprotic solvent is demonstrated, relative to uncoated glassy carbon or silver disk electrodes. The improvement of oxygen reduction activity increases the current capability and power output of the air electrode, facilitating future development of small, lightweight, long-life power sources.