Li–Ni–Mn spinels of nominal composition LiNi0.5Mn1.5O4, which are functional materials for electrodes in high‐voltage lithium batteries, are prepared by thermal decomposition of mixed nanocrystalline oxalates obtained by grinding hydrated salts and oxalic acid in the presence of polyethyleneglycol 400. Their structure, microstructure, and texture are established from combined X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction, transmission electron microscopy (TEM), IR spectroscopy, and N2 absorption measurements. The polymer tailors the shape of particles, which adopt a nanorodlike morphology at low temperatures (400 °C). In fact, the nanorods consist of highly distorted oriented nanocrystals connected by a polymer‐based film as inferred from IR and XPS spectra. The electrochemical properties of spinels in this peculiar form are quite poor, mainly as a result of the high microstrain content of their nanocrystals. Raising the temperature up to 800 °C partially destroys the nanorods, which become highly crystalline nanoparticles approximately 80 nm in size. At this temperature, the polymer facilitates crystal growth; this leads to highly crystalline polyhedral nanoparticles as revealed from TEM images and microstrain data. Following functionalization as a cathode in lithium cells, this material exhibits a very good rate capability, coulombic efficiency, and capacity retention even upon cycling at voltages as high as 5 V. Moreover, it withstands fast‐charge–slow‐discharge processes, which is an important cycle‐life‐related property for commercial batteries.

Disordered carbons obtained from cherry stones were tested as electrodes for lithium batteries and their properties were compared with those of short multiwalled carbon nanotubes (s-MWCNT), proposed as candidates for use in these electrochemical devices. Cells were cycled (up to 100 cycles) over a wide range of rates (C/10 to 5C). Previously, their structural, textural, and morphological properties were examined by X-ray diffraction patterns, normalN2 adsorption data, and electron microscopy images (scanning electron microscopy and transmission electron microscopy), respectively. All carbons exhibited irreversible capacity (IC) to an extent roughly governed by the H/O content among other variables. The best performing carbons were obtained at low calcination temperatures (500°C) . Although these conditions can increase IC, the effect can be offset by limiting the amount of Li inserted in the first charge. Moreover, this method improves capacity retention and rate capabilities. This approach allows one to obtain activated carbons with specific capacities of as high as 200mAhnormalg−1 at 5C; a high rate indeed. Their performance after as many as 100 cycles over a wide range of charge/discharge rates surpassed that of s-MWCNT and matched that of the best performing carbons reported so far.

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Six different carbons in variable particle size ranging from micrometric to nanometric and morphology ͑microbeads, flakes, nanofibers, and short and long multiwalled nanotubes͒ were tested as electrodes for Li-ion batteries. Their performance ͑particu-larly in regard to rate capability and cycling properties͒ was analyzed in terms of textural and structural properties as determined from N 2 adsorption and X-ray diffraction data, respectively. All carbons exhibited irreversible capacity ͑IC͒ to an extent governed by a combination of textural ͓͑S BET ͒ and pore volume͔ and structural properties ͑average layer stacking height and orientation index͒. However, no direct correlation between IC and cell performance in terms of the rate capability and cycling properties was observed. These two properties are more markedly influenced by structural ordering in the graphite layers. At low rates, high particle sizes and crystallinity resulted in enhanced cell performance. Ensuring good performance at high rates, however, required both a highly layered ordering and a nanometric particle size in the carbon. Carbons with special morphologies such as nanotubes or nanofibers possess a high structural disorder which is detrimental for use as electrode materials in Li-ion batteries.Graphitized carbons have so far been the most widely requested materials to manufacture anodes for commercial Li-ion batteries. This use relies on their ability to react reversibly with Li 1 and deliver a theoretical capacity of 372 mAh g −1 at voltages below 0.3 V vs Li metal. Advances in the use of graphitized carbons for this purpose have been the subject of many reviews. 2-6 The discovery of graphitized carbons with structures and textures such as fullerenes, single-walled carbon nanotube, multiwalled carbon nanotubes ͑MWCNTs͒, nanofibers, etc., opened up prospects for these materials and boosted activity in this research field. 7-12 Most of the forms have been deemed promising alternatives to conventional graphite on the grounds of their good electrochemical response in regard to delivered capacity and, occasionally, cycling. [13][14][15][16] In most cases however, the appraisal has been merely testimonial because studies provided inadequate data to endorse the usefulness of these singular structures with a view to supersede commercial graphite forms. Thus, a few years ago, Che et al. 14,17 suggested the future use of carbon nanotubes ͑CNTs͒ in Li-ion batteries on the grounds of a high Li + intercalation capacity ͑490 mAh g −1 ͒. However, no additional data concerning cycling performance or rate capability, which would have been essential to support this proposal, were reported. More systematic work on CNT 18,19 revealed a low reversible capacity measured at a relatively low rate ͑below 100 mAh g −1 at ca. C/4͒. Somewhat more impressive was the lithium storage capacity of ordered mesoporous carbon reported by Zhou et al. 20 ͑around 800 mAh g −1 , which was maintained over 20 cycles͒. However, the electrode was tested at a current equivalent to appro...

The electrochemical behavior of an Au-coated LiNi 0.5 Mn 1.5 O 4 nanospinel in lithium cells was studied at two different temperatures ͑25 and 50°C͒ and at five charge/discharge rates ͑C/6, C/4, 2C, 4C, and 8C͒. Two different coating methods were tested and the resulting products characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. One method, which involved treatment with HAuCl 4 in the presence of HCOH as reductant, resulted in poorer cell performance irrespective of the particular charge/discharge regime used, probably by effect of the attack on the material degrading its surface during the coating process. The other coating method involved evaporating Au on the spinel, the effect of coating on cell performance being dependent on both temperature and the charge/discharge rate. Thus, low rates ͑C/6, C/4͒ increased the capacity delivered by the cell at 50°C by ca. 20% relative to the bare spinel. This beneficial effect can be ascribed to the coating layer altering the electrolyte decomposition and the spinel particles being protected from attack by the species formed in the electrolyte decomposition. At high rates ͑2C, 4C͒, however, electrolyte decomposition played a minor role and crossing of the gold layer by lithium ions raised an energy barrier to be overcome. Under these conditions, the capacity delivered by the cell was markedly degraded irrespective of the temperature used.