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The results of a study of the electrochemical intercalation of lithium into Lonza KS15 artificial graphite in 1M LiC104 PC/EC (50:50) electrolyte are presented here. Electrolyte decomposition reactions occur during the first discharge at about 0.8 V vs. Li metal and their extent is greatly reduced by addition of crown ethers with 12 crown 4 being most effective. A mechanism is proposed for electrolyte decomposition reactions which includes at least two types of process, namely, propylene and ethylene evolution and formation on the surface of graphite of a solid electrolyte interphase film which includes lithium alkyl carbonates. The stoichiometry of lithium intercalation into graphite is found to be inversely dependent on the cycling rates and electrode thickness and proportional to the amount of carbon black added to the graphite.

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This paper will demonstrate that cathodes based on the high temperature form of orthorhombic LiMnO2, with the structure described by Hoppe, Brachtel and Jansen, have good capacity and cycle life. X-ray diffraction studies have revealed that cathodes prepared from orthorhombic LiMnO2 undergo a structural change on being charged beyond a certain potential in which the original structure is converted to spinel Lil-xMn204. Orthorhombic LiMnO2 has been found to have long-term stability in ambient conditions and is easily prepared in a one-step reaction.

, 54 1995 205-208 . This paper reports the results of electrochemical evaluations with metallic lithium anodes and on Rietveld refinements of X-ray and neutron powder diffraction data for these phases. Although these materials are prepared at moderately high temperatures, the refinements show that they have a structure similar to the monoclinic layered form of LiMnO prepared by soft chemistry at low temperatures by Armstrong and Bruce 2 w Ž. xw A.R. Armstrong, P.G. Bruce, Nature, 381 1996 499-500 and by Delmas and Capitaine C. Delmas, F. Capitaine, Extended Abstracts Ž. x of the Eighth International Meeting on Lithium Batteries 1996 470-471 . The degree of monoclinic distortion in the initial materials has an effect on the structural changes that occur on charging. The phases with a small monoclinic distortion change to an undistorted hexagonal structure on their first charge while those with a large monoclinic distortion change to a spinel-like structure on cycling. Crown

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A method that involves stenciling electrodes using dry powders for fuel cells is described and compared to anodes and cathodes prepared by the traditional spraying method using catalyst inks. Methods to determine the proton conductivity of the DMFC anode layer are also discussed. The stenciling method allows for the preparation of highly reproducible membrane electrode assemblies (MEAs) utilizing little waste material. MEAs can be prepared in a controlled manner using the stenciling technique. The resulting morphology of the as-prepared electrodes is observed to be dependent on the preparation method, while the thickness of the once hot-pressed catalyst layers appears to be independent of the preparation method. Stenciled anodes of the same catalyst loading were found to show a lower proton resistance (R p ) than sprayed anodes. However, the lower R p value was not sufficient to result in a measurable increase in the performance of a direct methanol fuel cell (DMFC); as in fact, the average steady-state DMFC performance was found to be the same using sprayed or stenciled electrodes. The DMFC performance was found to be strongly dependent on the Nafion content and large increases in the Nafion content were needed to increase the DMFC performance measurably. Even though thick electrodes were prepared in this work, the R p values of the stenciled anodes were found to be comparable to results reported in the literature for much thinner electrodes made using high metal catalyst loadings on carbon. This observation is most probably due to the higher Nafion content used in this work.

An electrolyte system which consists.of chloroethylene carbonate and propylene carbonate has been developed for lithium ion batteries containing a graphitic anode. The electrolyte decomposition during the first lithium intercalation into graphite in a propylene carbonate based electrolyte is significantly reduced in the presence of chloroethylene carbonate. Formation of a stable passivation film on the graphite surface is believed to be the reason for the improved cell performance.