To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
A technique to characterize the native passivation layer (NPL) on pure lithium metal foils in a scanning electron microscope (SEM) is described in this paper. Lithium is a very reactive metal, and consequently, observing and quantifying its properties in a SEM is often compromised by rapid oxidation. In this work, a pure lithium energy-dispersive x-ray spectrum is obtained for the first time in a high vacuum SEM using a cold stage/cold trap with liquid nitrogen reservoir outside the SEM chamber. A nanomanipulator (OmniProbe 400) inside the microscope combined with x-ray microanalysis and windowless energy dispersive spectrometer is used to fully characterize the NPL of lithium metal and some of its alloys by a mechanical removal procedure. The results show that the native films of pure lithium and its alloys are composed of a thin (25 nm) outer layer that is carbon-rich and an inner layer containing a significant amount of oxygen. Differences in thickness between laminated and extruded samples are observed and vary depending on the alloy composition.
Bromophenyl moieties were attached to the carbon-coated LiFePO4 (LiFePO4/C) surface by spontaneous reduction of in-situ generated 4-bromobenzene diazonium ions in organic media. The presence of the surface organic species on the grafted LiFePO4/C powders was confirmed by X-ray photoelectron spectroscopy. Thermogravimetric analyses revealed a low loading (lower than 1 wt. %) of grafted molecules. The electrochemical characterization of the LiFePO4/C cathodes showed that a low loading of bromophenyl groups at the LiFePO4/C surface can enhance the rate of Li+ extraction, presumably due to the decrease of the LiFePO4/C agglomerate size and an increase of the wettability of the electrode. On the other hand, poor performances were obtained using the grafted cathode material with the highest loading of bromophenyl moieties.
Optimized LiFePO4 positive electrode for Li-ion batteries was obtained after severe control of the fundamental properties of material. The nanoscopic structure and magnetic properties of a series of carbon-coated LiFePO4 particles prepared under various conditions were analyzed with XRD, FTIR, Raman and SQUID magnetometry. We evaluate intrinsic and extrinsic properties. The existence of low content of nano-sized ferromagnetic particles was evidenced by magnetic measurements in samples grown from iron(II) oxalate; such ferromagnetic clusters do not exist in the optimised samples grown from FePO4(H2O)2. Other impurity phases such as Fe2P, Li3Fe2(PO4)3, FeP2O7 were also detected for particular conditions of preparation. The impact of the carbon coating on the electrochemical properties is reported. Li-ion cells show excellent cyclability after 200 cycles at 60 °C without iron dissolution.
We present the properties of the carbon layer deposited at the surface of the LiFePO4 particles. Characterizations include scanning electron microscopy, high-resolution transmission electron microscopy, and Raman scattering spectroscopy. Analuysis of Raman spectra reveals that the carbon deposit is hydrogenated with very small hydrogen/carbon ratio, so that it belongs to the family of the amorphous graphitic carbon. It is expected to have the same properties (small hardness, high electronic conductivity) that favor both the Li diffusion from the LiFePO4 bulk and the charge-discharge rate of the cell.
Lithium titanium oxide (Li4Ti5O12) spinels are promising negative electrode materials for application in energy technology. In this work, we have synthesized Li4Ti5O12 and investigated its structure, electronic properties, and electrochemical features using several analytical spectroscopy and microscopy techniques. The equally spaced lattice fringes obtained using by the high-resolution transmission electron microscopy (HRTEM) along with electron diffraction reveal that the grown Li4Ti5O12 is well crystallized in the spinel structure without any indication of crystallographic defects such as dislocations or misfits. The electronic structure determination using high-resolution X-ray photoelectron spectroscopy (XPS) coupled with compositional studies using energy dispersive X-ray spectrometry (EDS) indicate excellent chemical quality of the Li4Ti5O12. Under the optimal synthetic condition, the sample delivers a discharge capacity of 161 mAh/g at C/12. The good cyclability of Li4Ti5O12 is attributed to the small expansion (δV≈1%) of the elementary unit-cell.
We report the electrochemical behavior of various layered oxides in Li cells. A series of LiNiyMnyCozO2 materials (with z=1-2y) was synthesized by “chimie douce” and investigated as positive electrodes in rechargeable lithium batteries. Electrochemical performances of LiNiyMnyCozO2 oxides are tested cell using non-aqueous 1M LiPF6 dissolved in EC-DEC. Charge discharge profiles are investigated as a function of the rate capability, the voltage window and the synthesis parameters of the cathode. A relation is found between the gravimetric capacity and the cation disorder of materials as indicated by magnetometry analysis.
Email your librarian or administrator to recommend adding this to your organisation's collection.