cyclability. In addition, as can be expected, the techniques and methodology of nanotechnology have been employed to prepare many simple and complex compounds, including oxides, and have been studied for Li cycling via various mechanisms. As a result of the research on alternative anodes for LIBs, the materials chemistry and electrochemistry of these materials have been enhanced and enriched very significantly during the past decade. 1.6. Scope of the Review and NomenclatureMetal-containing compounds in the form of oxides and oxysalts, such as, oxyfluorides, oxyhydroxide, phosphates, carbonates, and oxalates, are discussed in this review. These include bulk (micrometer-size) particles, nanosize particles, or agglomerates with various morphologies, thin films, and carbon, CNT, or graphene/metal oxide composites. The latter may contain electrochemically -active or −inactive additives. Metalcontaining compounds in the form of fluorides, 147,148 sulfides, 148 selenides, 136 nitrides, 148−151 phosphides 136,148 and antimonides 136 are omitted, even though good amount of work is available in the literature.As mentioned earlier, several review articles have appeared over the years, summarizing the situation. While there are only nine reviews 6,7,115,152−157 prior to 2006, there are more than 40 articles in the last 5 years that directly or indirectly described and discussed Li storage and cycling of oxide and oxide-related materials, in the form of Feature articles, Accounts, Perspectives, and Mini-and regular reviews. Many of these are listed in the references. 8,73,102,136,146,148,158−199 In brief, discussions were made on layered vanadium oxides by Cavana et al., 165 molybdenum oxides by Cavana et al. 165 and Ellefson et al., 200 TiO 2 -based nanostructures and their composite oxides by

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Nanoflakes of α‐Fe2O3 were prepared on Cu foil by using a thermal treatment method. The nanoflakes were characterized by X‐ray diffraction, scanning electron microscopy, high‐resolution transmission electron microscopy, and Raman spectroscopy. The reversible Li‐cycling properties of the α‐Fe2O3 nanoflakes have been evaluated by cyclic voltammery, galvanostatic discharge–charge cycling, and impedance spectral measurements on cells with Li metal as the counter and reference electrodes, at ambient temperature. Results show that Fe2O3 nanoflakes exhibit a stable capacity of (680 ± 20) mA h g–1, corresponding to (4.05 ± 0.05) moles of Li per mole of Fe2O3 with no noticeable capacity fading up to 80 cycles when cycled in the voltage range 0.005–3.0 V at 65 mA g–1 (0.1 C rate), and with a coulombic efficiency of > 98 % during cycling (after the 15th cycle). The average discharge and charge voltages are 1.2 and 2.1 V, respectively. The observed cyclic voltammograms and impedance spectra have been analyzed and interpreted in terms of the ‘conversion reaction' involving nanophase Fe0–Li2O. The superior performance of Fe2O3 nanoflakes is clearly established by a comparison of the results with those for Fe2O3 nanoparticles and nanotubes reported in the literature.

ZnCo2O4 has been synthesized by the low‐temperature and cost‐effective urea combustion method. X‐ray diffraction (XRD), HR‐TEM and selected area electron diffraction (SAED) studies confirmed its formation in pure and nano‐phase form with particle size ∼ 15–20 nm. Galvanostatic cycling of nano‐ZnCo2O4 in the voltage range 0.005–3.0 V versus Li at 60 mA g–1 gave reversible capacities of 900 and 960 mA h g–1, when cycled at 25 °C and 55 °C, respectively. These values correspond to ∼ 8.3 and ∼ 8.8 mol of recyclable Li per mole of ZnCo2O4. Almost stable cycling performance was exhibited in the range 5–60 cycles at 60 mA g–1 and at 25 °C with ∼ 98 % coulombic efficiency. A similar cycling stability at 55 °C, and good rate‐capability both at 25 and 55 °C were found. The average discharge‐ and charge‐potentials were ∼ 1.2 V and ∼ 1.9 V, respectively. The ex‐situ‐XRD, ‐HRTEM, ‐SAED and galvanostatic cycling data are consistent with a reaction mechanism for Li‐recyclability involving both de‐alloying‐alloying of Zn and displacement reactions, viz., LiZn ↔ Zn ↔ ZnO and Co ↔ CoO ↔ Co3O4. For the first time we have shown that both Zn‐ and Co‐ions act as mutual beneficial matrices and reversible capacity contribution of Zn through both alloy formation and displacement reaction takes place to yield stable and high capacities. Thus, nano‐ZnCo2O4 ranks among the best oxide materials with regard to Li‐recyclability.

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We report the fabrication of vertically aligned NiO nanowalls on nickel foils using a plasma assisted oxidation method. Electrochemical properties of as-synthesized NiO nanowalls were evaluated by galvanostatic cycling and cyclic voltammetery. The results show a capacity of ∼638 (mA h)/g (at 1.25C rate), with excellent capacity retention of up to 85 cycles, when cycled in the range, 0.005−3.0 V vs Li. The superior electrochemical performance of NiO nanowalls in comparison to the previously reported results on nanosized NiO particles can be attributed to its large surface area and shorter diffusion length for mass and charge transport. A possible reaction mechanism is discussed. We also report that electron field emission studies show that the verticllay aligned NiO nanowalls are efficient field emitters with a turn-on field of 7.4 V/µm and a maximum current density of ∼160 µA/cm2 can be achieved.

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