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Although 3d transition metal oxides (TMOs) are well-known as promising anodes for Li ion batteries, little is known about the mechanism of electrode process kinetics. In this work, impedance behavior of the flower-like hierarchical CuO electrode is first investigated to understand the kinetics that influences the performances of TMOs toward lithium. The electrochemical impedance spectra are measured at different discharge and charge states during cycling. A modified twoparallel diffusion path model is set up to account for the Nyquist plots. The kinetic parameters in the model that represent the migration of lithium ions through surface-passivating film, charge transfer on active material/electrolyte interfaces, and diffusion of lithium ions in solid material are discussed in detail. On the basis of the analysis of the variation of kinetic parameters, several promising approaches are proposed to improve the electrochemical performances of copper oxides, which can also be applicable to all the 3d transition metal oxides. ' INTRODUCTIONSince Tarascon et al. 1 first reported the excellent electrochemical performance of CoO toward lithium, 3d transition metal oxides (TMOs, where M is Fe, Co, Ni, and Cu) have been widely investigated as promising anodes for lithium ion batteries. [2][3][4][5] The mechanism of Li reactivity in TMOs differs from the classical Li intercalation/deintercalation or Li-alloying process but involves the formation and decomposition of Li 2 O. The electrode reaction of TMOs is shown as followsCompared to the current commercial carbonaceous anodes, TMOs have much higher theoretic capacities and better rate properties, which will hopefully realize the wide application of Li ion batteries in various areas as next-generation electronic devices, electric vehicles, solar energy storage, etc. For instance, the CuO film prepared by spray pyrolysis exhibited high reversible capacity (625 Ah kg -1 ) even over 100 cycles. 6 However, the Coulombic efficiencies and cycling performances of pure TMOs are disappointing. It is commonly attributed to the poor conductivity of active material and incomplete decomposition of Li 2 O during cycling. Thus, surface modification and nanostructure fabrication are developed to improve the electrical conductivity and enhance the electrochemical activity of TMOs. [7][8][9] Although various novel structures and original experiments have been reported, it is still short of theory supports. To effectively overcome the shortcomings of TMOs, it is necessary to understand the kinetics of lithium ion migration through surface film, charge transfer on solid/electrolyte interfaces, and further diffusion in electrode material since these processes indeed govern the polarization and reaction rate of TMOs. It would be desirable to find out what kinetics and relevant properties such as surface resistance, charge transfer resistance, and Li þ diffusion coefficient can improve the electrochemical performances of TMOs.Electrochemical impedance spectroscopy (EIS) is a commonly used technolo...

A new coordination polymer based on an aromatic carbonyl ligand is prepared and investigated as a positive active material for lithium ion batteries, namely, [Li2(C6H2O4)] (1). It is synthesized by the dehydration of [Li2(C6H2O4)·2H2O] (2). These compounds are characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), elemental analysis (EA), single crystal X-ray diffraction methods and powder X-ray diffraction (XRD). As positive material, compound 1 has an initial discharge capacity of 176 mAh·g−1 and a columbic efficiency of 93.18% in the first cycle. It might provide a new method for finding new positive-electrode materials in lithium ion batteries.

Fiberlike Fe2O3 macroporous nanomaterials have been prepared by in situ synthesis of Fe2O3 nanoparticles in the regenerated cellulose fibers during the wet spinning process, followed by the removal of cellulose matrix by calcination. The interpenetrated porous structure in the regenerated cellulose fibers at swollen state could serve as templates for the preparation of inorganic nanoparticles. The structure and properties of the Fe2O3 nanomaterials were characterized with X-ray diffraction, scanning electron microscopy, magnetometer, and electrochemical tests. The Fe2O3 nanomaterials exhibited integrated one-dimensional (1D) fiberlike morphology with macroporous structure. The results revealed that the inorganic nanomaterials displayed high purity of α-Fe2O3 and possessed large specific surface area, weak ferromagnetic properties, and superior electrochemical activity, having a discharge capacity of 2750 mA·h/g. Due to the small amounts of waste generated, this work provided a “green” pathway for the preparation of 1D inorganic nanomaterials with retention of the macropore structure, which have potential applications in the functional material fields.

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