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Liquid-cell in situ transmission electron microscopy (TEM) observations of the charge/discharge reactions of nonaqueous Li-oxygen battery cathode were performed with ∼5 nm spatial resolution. The discharging reaction occurred at the interface between the electrolyte and the reaction product, whereas in charging, the reactant was decomposed at the contact with the gold current collector, indicating that the lithium ion diffusivity/electronic conductivity is the limiting factor in discharging/charging, respectively, which is a root cause for the asymmetry in discharging/charging overpotential. Detachments of lithium oxide particles from the current collector into the liquid electrolyte are frequently seen when the cell was discharged at high overpotentials, with loss of active materials into liquid electrolyte ("flotsam") under minute liquid flow agitation, as the lithium peroxide dendritic trees are shown to be fragile mechanically and electrically. Our result implies that enhancing the binding force between the reaction products and the current collector to maintain robust electronic conduction is a key for improving the battery performance. This work demonstrated for the first time the in situ TEM observation of a three-phase-reaction involving gold electrode, lithium oxides, DMSO electrolyte and lithium salt, and O2 gas. The technique described in this work is not limited to Li-oxygen battery but also can be potentially used in other applications involving gas/liquid/solid electrochemical reactions.

A scheme for full quantum electronic excited state calculation is proposed that is based on the fragment molecular orbital (FMO) method with three-body effects. The accuracy and efficiency of this scheme is checked by calculating the excitation energy of hydrated formaldehyde and hydrated phenol. In all cases, three-body effects improved the excitation energy by the one- and two-body FMO methods with small computational cost, and the excitation energy approached more closely the full calculation value. The results also show that the three-body effects were relatively large and cannot be neglected.

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An environmentally controlled magnetic resonance imaging (MRI) system was developed to investigate the effects of relative humidity (RH) and current density on the transverse water content profile in a membrane under fuel cell operation at a practical fuel cell (PEMFC) operating temperature. The MRI visualization revealed that in a dry condition (40% RH), the water content in the membrane (membrane hydration number, λ) was ∼3 , and the water content profile was flat because the diffusion process in the membrane was dominant in the water transport. In a standard condition (80% RH), a water content of ∼8 in the membrane and partial dehydration at the anode were observed at a current density of 0.2A/cm2 , indicating that electro-osmosis was influential. In a wet condition (92% RH), a higher water content of around λ=15 was observed than that at 80% RH, suggesting that the generated water in the cathode catalyst layer was transported to the membrane at 92% RH. A larger water concentration gradient was observed at 0.1A/cm2 with 92% RH than that at 80% RH, suggesting that the larger water content in the membrane induced a greater electro-osmotic drag as the electro-osmosis coefficient was positively correlated with the water content.