Fumika Fujisaki

The freezing mechanism of water contacted with mesoporous silicas with uniform pore shapes, both cylindrical and cagelike, was studied by thermodynamic and structural analyses with differential scanning calorimetry (DSC) and X-ray diffraction (XRD) together with adsorption measurements. In the DSC data extra exothermic peaks were found at around 230 K for water confined in SBA-15, in addition to that due to the freezing of pore water. These peaks are most likely to be ascribed to the freezing of water present over the micropore and/or mesopore outlets of coronas in SBA-15. Freezing of water confined in SBA-16 was systematically analysed by DSC with changing the pore size. The freezing temperature was found to be around 232 K, close to the homogeneous nucleation temperature of bulk water, independent of the pore size when the pore diameter (d) < 7.0 nm. Water confined in the cagelike pores of SBA-16 is probably surrounded by a water layer (boundary water) at the outlets of channels to interconnect the pores and of fine corona-like pores, which is similar to that present at the outlet of cylindrical pores in MCM-41 and of cylindrical channels in SBA-15. The presence of the boundary water would be a key for water in SBA-16 to freeze at the homogeneous nucleation temperature. This phenomenon is similar to those well known for water droplets in oil and water droplets of clouds in the sky. The XRD data showed that the cubic ice I(c) was formed in SBA-16 as previously found in SBA-15 when d < 8.0 nm.

All-solid-state fluoride shuttle batteries (FSBs) have the potential to become the next generation of rechargeable batteries. However, there are gaps in the fundamentals of developing all-solid-state FSBs. For example, the mechanism by which the F– ions travel through a working device is not yet fully understood. In this work, we use a cutting-edge neutron diffractometer and a suite of analysis programs to perform Rietveld refinements. We employ the maximum entropy method to experimentally determine the F– ion diffusion pathways in the superior solid electrolyte with a fluorite-type structure, namely, Ba0.6La0.4F2.4. We show that the excessive F– ions, located at the specific interstitial sites, migrate to the neighboring F– ion sites based on the interstitialcy diffusion mechanism at the operating temperature for all-solid-state FSBs. Understanding the diffusion mechanism of F– ions plays a key role in the development of solid electrolytes for all-solid-state FSBs, particularly for those that can operate at room temperature.

Although Li-ion battery is one of the most widely used energy storage devices, there have been extensive efforts to push its limit to meet the ever increasing demands to increase its energy density for applications such as electric vehicles, portable electronics, and grid storages. Here, lithium metal anode plays a key role in the next generation energy storage devices, ultimately enabling the anode-free configuration. However, there are major challenges that need to be overcome. These include low Coulombic efficiency and the formation of dendrites. In this work, we adopted gallium-based liquid metal (LM) as a coating layer on a copper current collector to uniformly deposit lithium to prevent the dendrite formation and improve the cycle efficiency. The LM coating effectively improved the cycle performance in the anode-free configuration combined with Li(Ni,Co,Mn)O 2 cathode. The effect of the LM coating was confirmed by in situ transmission electron microscopy and optical microscopy observations. LM reduced the charge/discharge overpotentials with its high affinity with lithium. It also contributed to decompose the dendritic lithium in the discharge process reducing the dead lithium disconnected from the current collector.