Kohei Uosaki

Using a nondestructive synchrotron‐based position‐selective X‐ray diffraction computed tomography (XRD‐CT), position and discharged capacity dependences of the composition of the discharge products (Li‐deficient Li ₂ O ₂ ; Li _{2‐ x} O ₂ ) within the cathode of the lithium–oxygen battery (LOB) was investigated. As the discharge reaction proceeded, the discharge product, Li _{2‐ x} O ₂ (Li‐deficient Li ₂ O ₂ ), was formed and grew not from the lithium anode side where lithium ions are supplied through the separator, but from the gas diffusion layer (GDL) side where oxygen is introduced. Furthermore, the value of x , representing the lithium deficiency in Li _{2‐ x} O ₂ , decreased from the GDL side and eventually reached zero, indicating the formation of stoichiometric Li ₂ O ₂ . These results revealed that the discharge reaction proceeds preferentially from the GDL side rather than the lithium anode side.

The effect of para-substituents on the NC bond of aryl isocyanide molecules adsorbed on Au, Ag, Pt, and Pd surfaces was examined by vibrational sum frequency generation (VSFG) spectroscopy. The frequency of NC stretching vibration, υNC, depended on the electronic property of the substituents. When the substituents were more electron-withdrawing and more electron-donating, υNC shifted to lower and higher frequencies, respectively. However, υNC shifted to lower frequency again when the substituents were too electron-donating. The strong dependence of υNC on metal substrates was also observed, reflecting the difference in metal d-band energies, which leads to the difference in the contributions of σ-donation and π back-donation of the NC–metal coupling.

Online mass spectrometry of lithium oxygen batteries during linear voltage sweep charge after discharge revealed that LiOH and Li₂CO₃ are generated during discharge in addition to two types of Li₂O₂ which are oxidized in low and high charge voltages.

A metal-metal bond between coordination complexes has the nature of a covalent bond in hydrocarbons. While bimetallic and trimetallic compounds usually have three-dimensional structures in solution, the high directionality and robustness of the bond can be applied for on-surface syntheses. Here, we present a systematic formation of complex organometallic oligomers on Cu(111) through sequential ring opening of 11,11,12,12-tetraphenyl-1,4,5,8-tetraazaanthraquinodimethane and bonding of phenanthroline derivatives by multiple Cu atoms. A detailed characterization with a combination of scanning tunneling microscopy and density functional theory calculations revealed the role of the Cu adatoms in both enantiomers of the chiral oligomers. Furthermore, we found sufficient strength of the bonds against sliding friction by manipulating the oligomers up to a hexamer. This finding may help to increase the variety of organometallic nanostructures on surfaces.

The ratio of electrolyte amount against areal capacity ( E / C ) has a large impact on the performance of stacked-type lithium–oxygen batteries. The unique cell degradation behavior during the charging process under low E / C conditions was also demonstrated.