Poor mass transport in the electrolyte of Li ion batteries causes large performance losses in high-power applications such as vehicles, and the determination of transport properties under or near operating conditions is therefore important. We demonstrate that in situ (7)Li NMR imaging in a battery electrolyte can directly capture the concentration gradients that arise when current is applied. From these, the salt diffusivity and Li(+) transport number are obtained within an electrochemical transport model. Because of the temporal, spatial, and chemical resolution it can provide, NMR imaging will be a versatile tool for evaluating electrochemical systems and methods.

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The influence of ambient concentrations of carbon dioxide on the NaCl-induced atmospheric corrosion of high purity die-cast MgAl alloys (AM20 and AM60) and MgAlZn alloy (AZ91) is reported. Samples were exposed four weeks in a carefully controlled synthetic atmosphere. Relative humidity was 95%, the temperature was 22.0°C, and the concentration of CO2 was <1 or 350 ppm. Sodium chloride was added before the exposures false(70 μnormalg/cm2false). The corrosion products were analyzed by gravimetry, ion chromatography, X-ray diffraction, and environmental scanning electron microscopy. Mass gain and metal loss results are reported. As expected, the combination of high humidity and NaCl is very corrosive toward the magnesium alloys investigated. The NaCl-induced corrosion is inhibited by ambient concentrations of CO2. Exposures in the absence of CO2 give rise to heavy pitting; normalMgfalse(OH)2, brucite, is the dominant corrosion product. In the presence of CO2, a uniform layer of hydrated magnesium hydroxy carbonate, Mg5false(CO3)4false(OH)2⋅5H2O, forms. In both environments, the corrosion rates increased in the order AZ91