Tomoaki Kaneko

Access full-text academic articles: J-STAGE is an online platform for Japanese academic journals.

Lithium (Li) metal negative electrodes have enticed a wide attention for high-energy-density batteries. However, its low Coulombic efficiency (CE) due to parasitic electrolyte reduction has been an alarming concern. Concentrated electrolytes are one of the promising concepts that can stabilize the Li metal/electrolyte interface, thus increasing the CE; however, its mechanism has been still controversial. In this work, we used LiN(SO₂F)₂ (LiFSI) and weakly solvating 1,2-diethoxyethane (DEE) as a model electrolyte to study how its liquid structure changes upon increasing salt concentration and how it is linked to the Li plating/stripping CE. Based on previous works, we focused on Li electrode potential (E_Li with reference to the redox of ferrocene) and solid electrolyte interphase (SEI) formation. Although the E_Li shows a different trend in DEE as compared to conventional 1,2-dimethoxyethane (DME), which is accounted for by different ion-pairing states of Li⁺ and FSI^-, the E_Li-CE plots are overlapped for both electrolytes, suggesting that the E_Li is one of the dominant factors of the CE. On the other hand, the extensive ion pairing results in the upward shift of FSI^- reduction potential, as demonstrated both experimentally and theoretically, which promotes FSI^--derived inorganic SEI. Both E_Li and SEI contribute to increasing the Li plating/stripping CE.

The transition between MgM2O4 (M = Mn, Fe, Co) spinels (SPs) and MgMO2 rock salts (RS) has attracted considerable interest for cathode reactions in future magnesium battery applications. To improve the cycling performance, one should suppress the consumption of solvent molecules. In this study, we investigated ether solvent decomposition on MgM2O4 SP and MgMO2 rock-salt surfaces using first-principles calculations. We found that the C–H bond dissociation of ether molecules on the SP surface was exothermic, while the C–H bond dissociation on RS and C–O bond dissociation on both SP and RS surfaces were endothermic, irrespective of the transition metal element. The products of C–H dissociation reactions at the SP surfaces have occupied states originating from SP surfaces inside the bandgap. As the SP surface is destabilized by C–H dissociation, the electrons at this level can be extracted as an oxidative current.

In recent times, the quality of childcare and childcare workers’ expertise have attracted public attention. This study aimed to examine the effectiveness of micro-teaching training for in-service kindergarten teachers. In Analysis 1, mock childcare practices in the two surveys were compared using utterance analysis, and behavioral changes in participants who roleplayed a teacher and a child were examined. The results indicate that the instructions and attitudes of the teacher changed positively. In addition, the child accepted the teacher’s instructions and came to participate. In Analysis 2, the effects immediately after completing the training and two months after the training were examined. The results indicated that the effects of micro-teaching on understanding young children and learning motivation could be observed immediately after the training, and teachers’ abilities related to attitudes and skills developed two months after the training.

We investigate the structures, stability and electronic properties of graphene adsorbed on Y₂O₃(111) using first-principles calculations based on density functional theories. When the interface of Y₂O₃(111) is terminated by an Y-layer, graphene is chemisorbed on Y₂O₃, resulting in the strong modification of electronic band structures. When the Y₂O₃(111) surface is terminated with O atoms and extra O atoms, on the other hand, graphene is physisorbed on Y₂O₃(111). Therefore, an O-rich environment is preferable for the graphene and Y₂O₃ interface.