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This paper investigates chemical bleaching of wood to make species-specific practical recommendations for colour adjustment of veneer in furniture conservation. In more detail, chemical bleaching of Honduras mahogany (Swietenia macrophylla), European walnut (Juglans regia), Rio rosewood (Dalbergia nigra), padauk (Pterocarpus spp.), and purpleheart (Peltogyne spp.) is investigated using 11 different bleach solutions. Both oxidative (e.g. hydrogen peroxide and potassium permanganate) and reductive (e.g. oxalic acid and sodium bisulphite) solutions were used. The results show that the wood species react differently with the investigated bleach solutions. It can also be noted that not all investigated solutions were suitable for all wood species. Based on the results, wood species-specific bleach solutions are recommended.

The solid electrolyte interphase (SEI) of graphite electrodes has been extensively studied using surface sensitive techniques such as photoelectron spectroscopy (PES) and soft X-ray spectroscopy. By combining measurements of reference compounds with graphite electrodes cycled in different electrolytes and under different conditions, knowledge of the solid electrolyte interphase (SEI) chemistry can be obtained. In this article, conclusive results concerning the chemical composition of the inorganic part of the SEI is described. The results show that Li2O often reported to be present in the SEI could be an artifact from abusive Ar+ sputtering. The presence of Li2CO3 is a matter of debate; the compound is not observed in anodes extracted from hermetically sealed cells that are never exposed to air. The results show that cell-design and sample handling are crucial to the observed chemical composition of the SEI.

High-power lithium-ion cells for transportation applications are being developed and studied at Argonne National Laboratory. The current generation of cells containing LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2}-based cathodes, graphite-based anodes, and LiPF6-based electrolytes show loss of capacity and power during accelerated testing at elevated temperatures. Negative electrode samples harvested from some cells that showed varying degrees of power and capacity fade were examined by X-ray photoelectron spectroscopy (XPS). The samples exhibited a surface film on the graphite, which was thicker on samples from cells that showed higher fade. Furthermore, solvent-based compounds were dominant on samples from low power fade cells, whereas LiPF{sub 6}-based products were dominant on samples from high power fade cells. The effect of sample rinsing and air exposure is discussed. Mechanisms are proposed to explain the formation of compounds suggested by the XPS data.

The origin of the different Li+ intercalation behavior of raw and jet-milled natural graphite has been investigated. Jet-milled graphite is found to cycle reversibly in equal solvent mixture of pro ...

The influence of electrolyte additives on the thermal stability of graphite anodes in a Li-ion battery has been investigated. The selected additives are: ethyltriacetoxysilane, 1,3 benzoldioxole, tetra (ethylene glycol) dimethylether and vinylene carbonate. These compounds were added in 4% to an electrolyte consisting of 1 M LiBF4 ethylene carbonate (EC/diethyl carbonate (DEC) solvent mixture. Differential scanning calorimetry (DSC) was used to investigated the thermal stability. The electrochemical performance was investigated by galvanostatic cycling and the formed solid electrolyte interphase (SEI) was characterised by photoelectron spectroscopy (PES) using Al Ka and synchrotron radiation /SR). The onset temperature for the thermally activated reactions was found to increas for all electrodes cycled with additives compared to electordes cycled without additives. The onset temperature in creased in the order: no additive < tetra (ethylene glycole) dimethyl ether < 1,3-benzoldioxole < ethyl-triacetoxysilane < vinylene carbonate. Feature in the PES spectra found to be associated with high onset temeratures for thermally activated reactions are: (i) no discernible graphite peak, (ii) small amount of salt species of the type LiF and LixBFyOz and (iii) larger amounts of organic compounds preferably with a high oxygen content.

We have measured X-ray absorption and emission near the C 1s edge of graphite electrodes cycled in lithium-ion battery cells. Resonantly excited emission spectra of graphite electrodes exhibit features characteristic of both highly oriented pyrolytic graphite as well as polycrystalline graphite. Spectra of three electrodes cycled in two different electrolytes are presented and compared with spectra of the pristine electrode. A solid electrolyte interphase (SEI) was detected on the electrochemically cycled electrodes. By the use of selective excitation, resonant X-ray emission spectra of the SEI-species were obtained and compared to spectra of reference compounds. The SEI on the cycled graphite anode was shown to comprise lithium oxalate (Li2C2O4), lithium succinate (LiO2CCH2CH2CO2Li) and lithium methoxide (LiOCH3).

Jet-milled natural Swedish graphite has been evaluated as an anode material for Li-ion battery applications, with a focus on rate capability of the material. The material was found to have a superior rate capability compared to other carbon materials with similar particle sizes. It could also intercalate and deintercalate lithium reversibly in an electrolyte based on propylene carbonate:ethylene carbonate (1:1). Jet-milling was found to increase the amount of rhombohedral phase (3R) in the material from 15 to 40%. However, after repeated electrochemical intercalation and deintercalation of lithium, the amount of 3R phase decreases to ∼5%. Neither rate capability nor PC-tolerance can therefore be correlated to the amount of 3R phase.

The thermal stability of the solid electrolyte interphase (SEI) formed on a graphite anode has been enhanced by adding an anion receptor, tris(pentafluorophenyl)borane (TPFPB), to the electrolyte. The investigated electrolyte was LiBF4 in a 2:1 mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Two concentrations of TPFPB have been investigated, 0.2 and 0.8 M. Galvanostatic cycling and differential scanning calorimetry (DSC) were used to study the effect of TPFPB on the electrochemical performance and thermal stability of graphite anodes. The best performance is obtained for a graphite anode cycled in an electrolyte with 0.2 M TPFPB: cyclability is improved, and the onset temperature for the first thermally activated reaction is increased by more than 60 °C up to 140–160 °C. X-ray photoelectron spectroscopy (XPS) has been used to examine the composition of the SEI formed in the different electrolytes; the improved performance for the graphite cycled with 0.2 M TPFPB is attributed to a reduced amount of LiF in the SEI. Keywords: Lithium-ion battery, Graphite, Thermal stability, Anion receptor, Differential scanning calorimetry, X-ray photoelectron spectroscopy

The influence of lithium salt on the interfacial reactions controlling the thermal stability of graphite anodes

High-resolution neutron powder diffraction (NPD) and small-angle neutron scattering (SANS) experiments were carried out on several different types of carbon used as anodes in secondary lithium-ion batteries. The materials selected were Swedish natural graphite (crude and jet-milled), meso-carbon microbeads, and hard carbon. SANS data revealed a nanopore structure in hard carbon. Absolute calibration of SANS data for hard carbon was done to calculate the volume fraction of the nanopores. Estimation of the hexagonal (AB) and the rhombohedral (ABC) phase content in Swedish natural graphite from NPD data revealed that the jet milling increased the amount of the ABC phase. All these results are discussed to explain the electrochemical performances and structure–property relations of different carbon anode materials.

A new TFSI- anion disordering mode has been discovered in a supercooled plastic crystalline phase of Et4NTFSI, which may, in part, account for the low melting points of TFSI- salts with organic cations, thereby forming ionic liquids, and the intriguing properties of LiTFSI for lithium battery applications.

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Surface Chemistry of Carbon-Treated LiFePO4 Particles for Li-Ion Battery Cathodes Studied by PES