Nanocrystalline ZnFe 2 O 4 and Ag x ZnFe 2 O 4 (x ϭ 0.16, 0.37, 0.50) thin films have been prepared by reactive pulsed laser deposition, and used as anode materials for Li-ion batteries for the first time. X-ray diffraction ͑XRD͒ and scanning electron microscopy measurements showed that the prepared films were composed of a nanocrystalline structure with the average particle size less than 100 nm. The initial reversible capacity of ZnFe 2 O 4 and Ag 0.37 ZnFe 2 O 4 film electrodes reached 556 and 700 mAh/g, respectively, at a current density of 10 A cm Ϫ2 between 0.01 and 3.0 V. The Ag 0.37 ZnFe 2 O 4 film electrode exhibited better cyclability than ZnFe 2 O 4 film electrode, and retained 91% of the reversible capacity up to 100 cycles. According to our results on cyclic voltammetry of Li/ZnFe 2 O 4 cell coupled with ex situ photoelectron spectroscopy and XRD measurements of as-deposited and lithiated film electrodes, we suggest that the mechanism of ZnFe 2 O 4 film reacted with lithium involves reduction of Zn 2ϩ and Fe 3ϩ to metallic Zn and Fe 2ϩ , accompanying the formation of Li-Zn alloy. The dramatically improved electrochemical performance of Ag 0.37 ZnFe 2 O 4 film electrode might be related to the change of the reaction process after silver doping.
The binding constants of non-covalent cyclodextrin-alkali cation complexes have been systematically studied by an improved mass spectrometric titration and competitive ESI-MS. Also, the structural features of the complexes were discussed. Our results are valuable for better understanding of mechanisms driving inclusion chemistry under well-defined conditions.
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