Research to develop alternative electrode materials with high energy densities in Li-ion batteries has been actively pursued to satisfy the power demands for electronic devices and hybrid electric vehicles. This critical review focuses on anode materials composed of Group IV and V elements with their composites including Ag and Mg metals as well as transition metal oxides which have been intensively investigated. This critical review is devoted mainly to their electrochemical performances and reaction mechanisms (313 references).

Li-alloy based anode materials for Li secondary batteries.

Silicon oxides have been recognized as a promising family of anode materials for high-energy lithium-ion batteries (LIBs) owing to their abundant reserve, low cost, environmental friendliness, easy synthesis, and high theoretical capacity. However, the extended application of silicon oxides is severely hampered by the intrinsically low conductivity, large volume change, and low initial coulombic efficiency. Significant efforts have been dedicated to tackling these challenges towards practical applications. This Review focuses on the recent advances in the synthesis and lithium storage properties of silicon oxide-based anode materials. To present the progress in a systematic manner, this review is categorized as follows: (i) SiO-based anode materials, (ii) SiO2-based anode materials, (iii) non-stoichiometric SiOx-based anode materials, and (iv) Si-O-C-based anode materials. Finally, future outlook and our personal perspectives on silicon oxide-based anode materials are presented.

Silicon oxides: a promising family of anode materials for lithium-ion batteries

Structural ceramic nanocomposites are reviewed with emphasis on the Al 2 O 3 SiC and Si 3 N 4 SiC systems. The incorporation of a nanosized second phase, such as SiC, into a ceramic matrix can lead to an improvement in mechanical properties. It is still unclear, however, whether those improvements can directly be related to an intrinsic ‘nanocompossite effect’ or to other factors. This review is divided into three parts. First, basic processing routes for nanocomposites, namely conventional powder processing, sol-gel processing and polymer pyrolysis are presented in detail. Second, the mechanical properties of different nanocomposites are compared. Finally, models which attempt to explain the improvements in these properties are explored. It will be shown that the strength increase can best be related to a reduction in processing defect size. For applications the most interesting properties of nanocomposites are their wear, creep and high temperature performance.

Structural ceramic nanocomposites

Review of progress, QNDE

We report the bulk preparation of nanocrystalline Si−SiO2 (nc-Si/SiO2) composites via straightforward reductive thermal annealing of a well-defined molecular precursor, hydrogen silsesquioxane. The presented method affords quantitative yields of composite powders in large quantities. Freestanding, hydride-surface-terminated silicon nanocrystals that photoluminesce throughout the visible spectrum are readily liberated from nc-Si/SiO2 composite powders upon etching in ethanol−water solutions of hydrofluoric acid. Composites and freestanding particles were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, Fourier transform infrared spectroscopy (FT−IR), and thermogravimetric analysis (TGA).

Hydrogen Silsesquioxane: A Molecular Precursor for Nanocrystalline Si−SiO2 Composites and Freestanding Hydride-Surface-Terminated Silicon Nanoparticles

The present state of research on the structure of amorphous silicon monoxide (SiO) is reviewed. The black, coal-like modification of bulk SiO is studied by a combination of diffraction, microscopy, spectroscopy, and magnetometry methods. Partial radial distribution functions of SiO are obtained by X-ray, neutron and electron diffraction. Disproportionation of SiO into Si and SiO2 is verified. High resolution TEM gives an upper limit of less than 2 nm for the typical Si cluster size. The Si K-edge electron energy-loss near-edge structure (ELNES) data of SiO are interpreted in terms of the oxidation states Si4+ and Si0. X-ray photoelectron spectroscopy gives first details about possible stoichiometric inhomogeneities related to internal interfaces. The wipe-out effect in the 29Si MAS NMR signal of SiO is confirmed experimentally. The new estimation of the wipe-out radius is about 1.1 nm. First-time W-band, Q-band, and X-band ESR and SQUID measurements indicate an interfacial defect structure. Frequency distributions of atomic nearest-neighbours are derived. The interface clusters mixture model (ICM model) suggested here describes the SiO structure as a disproportionation in the initial state. The model implies clusters of silicon dioxide and clusters of silicon surrounded by a sub-oxide matrix that is comparable to the well-known thin Si/SiO2 interface and significant in the volume because of small cluster sizes.

An interface clusters mixture model for the structure of amorphous silicon monoxide (SiO)

Residual stresses in an alumina-SiC particulate composite were studied as a function of SiC content by X-ray diffraction. The average microstresses in each phase and the stress fluctuations in the matrix were evaluated from a combination of X-ray reflection shift and line broadening analysis. The measured average microstresses show good agreement with those calculated theoretically from a simple model. The average microstresses in the matrix increases with the SiC content while the fluctuations of the stress field decrease. In effect, the mean dislocation density in the alumina matrix increases with the SiC volume fraction with more dislocations forming networks and subboundaries, as was confirmed by transmission electron microscopy.

Residual stresses in alumina-SiC nanocomposites

Strains in thin films cause reflection shifts in an x‐ray diffraction measurement. These shifts can in turn be used to determine the strains. A model is presented to calculate the reflection shifts caused by a biaxial strain state in a thin film composed of a material of any crystal class. The model takes into account the elastic anisotropy of the film material.

Calculation of thermally induced strains in thin films of any crystal class

Oxide formation on magnetron-sputtered thin copper films (35 nm thickness) was studied by x-ray reflectometry and grazing incidence x-ray diffraction. The films were oxidized in air at temperatures of 175 ◦ C, 200 ◦ C, 225 ◦ C and 250 ◦ C. The reflectometry and the diffractometry data indicate the formation of Cu2O. A power-law dependence of the oxide layer thickness was found. The activation energy obtained is weakly time dependent. Copyright  2002 John Wiley & Sons, Ltd.

Thomas Wieder

Papers

An interface clusters mixture model for the structure of amorphous silicon monoxide (SiO)

Residual stresses in alumina-SiC nanocomposites

Calculation of thermally induced strains in thin films of any crystal class

Reflectometry studies of the oxidation kinetics of thin copper films

Microstructure analysis of ohmic contacts on MBE grown n-GaSb and investigation of sub-micron contacts