In cells containing Li 1.05 ͑Ni 1/3 Co 1/3 Mn 1/3 ͒ 0.95 O 2-based positive and graphite-based negative electrodes, a significant portion of cell impedance rise on aging is known to be from the negative electrode. One possible reason for this impedance rise is the dissolution of transition-metal elements from the oxide electrode that accumulate and create a high-impedance layer at the negative electrodeelectrolyte interface. This article details dynamic secondary ion mass spectrometry ͑SIMS͒ measurements, which provide a relative comparison of Mn, Co, and Ni contents on fresh, formed, and aged graphite electrodes. The data clearly indicate that these transition-metal elements accumulate at the electrode surface and diffuse into the electrode during cell aging.

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AC alternating current AFM atomic force microscopy ANL Argonne National Laboratory ASI area-specific impedance (ohm-cm 2) ATD Advanced Technology Development ATR attenuated total reflection BNL Brookhaven National Laboratory BSF battery scaling factor CSAFM current-sensing atomic force microscopy CE capillary electrophoresis CF capacity fade DEC diethyl carbonate DEDOHC diethyl-2,5-dioxahexane carboxylate DMC dimethyl carbonate DMDOHC dimethyl-2,5-dioxahexane carboxylate DME dimethoxy ethane DMF dimethyl formamide DOE U.S. Department of Energy EC ethylene carbonate EDX energy dispersive X-ray analysis EELS electron energy loss spectroscopy EMC ethyl methyl carbonate EMDOHC ethyl methyl-2,5-dioxahexane carboxylate EOC end of charge EOL end of life EXAFS extended X-ray absorption fine structure EY electron yield FFT fast Fourier transform FID flame ionization detector FTIR Fourier transform infrared FY fluorescence yield GC gas chromatography GC-MS gas chromatography mass spectrometry GPC gel permeation chromatography Gen 1 (+) LiNi 0.8 Co 0.2 O 2 cathode Gen 1 (-) MCMB:SFG-6 (82:18) Gen 1 electrolyte 1.2 M LiPF 6 EC:DEC (1:1 by wt) Gen 2 cells ATD Generation 2 baseline cells Gen 2 (+) LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode Gen 2 (-) MAG-10 synthetic graphite anode Gen 2 electrolyte 1.2 M LiPF 6 EC:EMC (3:7 by wt) HEV hybrid electric vehicle HF hydrogen fluoride (hydrofluoric acid) DIAGNOSTIC EXAMINATION OF GENERATION 2 LITHIUM-ION CELLS AND ASSESSMENT OF PERFORMANCE DEGRADATION MECHANISMS

Vertically aligned silicon oxide nanowires can be synthesized over a large area by a low-temperature, ion-enhanced, reactive vapour-liquid-solid (VLS) method. Synthesis of these randomly ordered arrays begins with a thin indium film deposited on a Si or SiO(2) surface. At the processing temperature of 190 degrees C, the indium film becomes a self-organized seed layer of molten droplets, receiving atomic silicon from a DC magnetron sputtering source rather than from the gaseous precursors used in conventional VLS growth. Simultaneous vigorous ion bombardment aligns the objects vertically and expedites mixing of oxygen and silicon into the indium. Silicon oxide precipitates from each droplet in the form of multiple thin strands having diameters as small as 5 nm. These strands form a single loose bundle growing normal to the surface, eventually consolidating to form one nanowire. The vertical rate of growth can reach 300 nm min(-1) in an environment containing argon, hydrogen, and traces of water vapour. This paper discusses the physical and chemical factors leading to the formation of the nanostructures. It also demonstrates how the shape of the resulting nanostructures can be further controlled by sputtering, during both VLS growth and post-VLS processing. Key technological advantages of the developed process are nanowire growth at low substrate temperatures and the ability to form aligned nanostructure arrays, without the use of lithography or templates, on any substrate onto which a thin silicon film can be deposited.