Li intercalation in 2D iron phosphate synthesized from the partial dehydration and deprotonation of vivianite.

This study focuses on the cation intercalation of structurally unique compounds synthesized from the partial dehydration and deprotonation of coordinated water molecules in hydrous materials. Partial dehydration can potentially result in hydrous materials with a porous nature, which maintains the parent structure of the material, and deprotonation causes oxidation in the hydrous materials. Li-intercalation experiments were conducted on the hydrous iron(II) phosphate mineral, vivianite (Fe2+3(PO)·8HO), and its oxidized and partially dehydrated product, santabarbaraite.

Photoinduced Nonvolatile Displacive Transformation and Optical Switching in MnTe Semiconductors.

MnTe is considered a promising candidate for next-generation phase change materials owing to the reversible and nonvolatile phase transformation between its α and β' phases by irradiation of a nanosecond laser or application of a pulse voltage. In this work, for a faster phase control of MnTe, the response of metastable β-MnTe thin films to femtosecond (fs) laser irradiation was investigated. Using ultrafast optical spectroscopy, we inferred transient phase transformation.

Optimizing LiMnMO cathode materials for aqueous photo-rechargeable batteries.

Spinel oxides are promising for high-potential cathode materials of photo-rechargeable batteries. However, LiMnMO (M = Mn) shows a rapid degradation during charge/discharge under the illumination of UV-visible light. Here, we investigate various spinel-oxide materials by modifying the composition (M = Fe, Co, Ni, Zn) to demonstrate photocharging in a water-in-salt aqueous electrolyte.

Ultraporous, Ultrasmall MgMnO Spinel Cathode for a Room-Temperature Magnesium Rechargeable Battery.

Magnesium rechargeable batteries (MRBs) promise to be the next post lithium-ion batteries that can help meet the increasing demand for high-energy, cost-effective, high-safety energy storage devices. Early prototype MRBs that use molybdenum-sulfide cathodes have low terminal voltages, requiring the development of oxide-based cathodes capable of overcoming the sulfide's low Mg conductivity. Here, we fabricate an ultraporous (>500 m g) and ultrasmall (<2.

Examining Electrolyte Compatibility on Polymorphic MnO Cathodes for Room-Temperature Rechargeable Magnesium Batteries.

Rechargeable magnesium batteries are promising candidates for post-lithium-ion batteries, owing to the large source abundance and high theoretical energy density. However, there remain few reports on constructing practical cells with oxide cathodes and Mg anodes at room temperature. In this work, we compare the reaction behavior of various MnO polymorph cathodes in two representative electrolytes: Mg[TFSA]/G3 and Mg[Al(hfip)]/G3.

Laser-induced breakdown spectroscopy to obtain quantitative three-dimensional hydrogen mapping in a nickel-metal-hydride battery cathode for interpreting its reaction distribution.

We present a method for obtaining a three-dimensional quantitative hydrogen distribution in a Ni-MH battery cathode using laser-induced breakdown spectroscopy (LIBS) and demonstrate that the reaction distribution in the cathode can be interpreted based on a state-of-charge (SOC) distribution converted from the hydrogen distribution. In this method, we measured the hydrogen emission-line intensities at 656.28 nm for a model cathode cycled five times at 2.

Light-induced Li extraction from LiMnO/TiO in a water-in-salt electrolyte for photo-rechargeable batteries.

Photocharging of high-potential spinel LiMnO is demonstrated by using a water-in-salt electrolyte and TiO nanoparticles. In a developed half-cell system with an electron acceptor, Li extraction from LiMnO proceeds under the illumination of UV-visible light at an estimated rate of ∼23 mA g. This work paves the way for high-potential cathode materials in photo-rechargeable batteries.

Excellently balanced water-intercalation-type heat-storage oxide.

Importance of heat storage materials has recently been increasing. Although various types of heat storage materials have been reported to date, there are few well-balanced energy storage materials in terms of long lifetime, reversibility, energy density, reasonably fast charge/discharge capability, and treatability. Here we report an interesting discovery that a commonly known substance, birnessite-type layered manganese dioxide with crystal water (δ-type KMnO⋅ nHO), exhibits a water-intercalation mechanism and can be an excellently balanced heat storage material, from the above views, that can be operated in a solid state with water as a working pair.

Electrochemically Induced Strain Evolution in Pt-Ni Alloy Nanoparticles Observed by Bragg Coherent Diffraction Imaging.

Strain is known to enhance the activity of the oxygen reduction reaction in catalytic platinum alloy nanoparticles, whose inactivity is the primary impediment to efficient fuel cells and metal-air batteries. Bragg coherent diffraction imaging (BCDI) was employed to reveal the strain evolution during the voltammetric cycling in Pt-Ni alloy nanoparticles composed of PtNi, PtNi, and PtNi. Analysis of the 3D strain images using a core-shell model shows that the strain as large as 5% is induced on Pt-rich shells due to Ni dissolution.

Structure Design of Long-Life Spinel-Oxide Cathode Materials for Magnesium Rechargeable Batteries.

Development of metal-anode rechargeable batteries is a challenging issue. Especially, magnesium rechargeable batteries are promising in that Mg metal can be free from dendrite formation upon charging. However, in case of oxide cathode materials, inserted magnesium tends to form MgO-like rocksalt clusters in a parent phase even with another structure, which causes poor cyclability.

Circumventing huge volume strain in alloy anodes of lithium batteries.

Since the launch of lithium-ion batteries, elements (such as silicon, tin, or aluminum) that can be alloyed with lithium have been expected as anode materials, owing to larger capacity. However, their successful application has not been accomplished because of drastic structural degradation caused by cyclic large volume change during battery reactions. To prolong lifetime of alloy anodes, we must circumvent the huge volume strain accompanied by insertion/extraction of lithium.

Electrochemical phase transformation accompanied with Mg extraction and insertion in a spinel MgMnO cathode material.

One of the key challenges when developing magnesium rechargeable batteries (MRB) is to develop Mg-intercalation cathodes exhibiting higher redox potentials with larger specific capacities. Although Mg-transition-metal spinel oxides have been shown to be excellent candidates as MRB cathode materials by utilizing the valence change from trivalent to divalent of transition metals starting from Mg insertion, there is no clear evidence to date that Mg can be indeed extracted from the initial spinel hosts by utilizing the change from trivalent to quadrivalent. In this work, we clearly present various experimental evidences of the electrochemical extraction of Mg from spinel MgMnO.

Solvation-Structure Modification by Concentrating Mg(TFSA)-MgCl-Triglyme Ternary Electrolyte.

Mg(TFSA)/triglyme(G3)-based electrolytes (TFSA: bis (trifluoromethanesulfonyl) amide) are one of candidates for magnesium rechargeable batteries, but the passivation of Mg-metal anode due to the TFSA anion is fatal in practical use. In this work we show that at elevated temperatures around 150 °C a comparable amount of MgCl salt can be dissolved in concentrated Mg(TFSA)/G3 solutions, and the passivation of Mg metal is markedly suppressed in such highly concentrated solutions (1 ≤ G3/Mg-salts ≤ 2) in comparison with in the dilute solutions (G3/Mg-salts ≫ 2). By decreasing the amount of G3 solvent, the solvation structure of Mg ions is modified in that free TFSA anions are drastically lowered, which would consequently decrease the reactivity of TFSA anions.

Two distinct crystallization processes in supercooled liquid.

Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials.

Intercalation and Push-Out Process with Spinel-to-Rocksalt Transition on Mg Insertion into Spinel Oxides in Magnesium Batteries.

On the basis of the similarity between spinel and rocksalt structures, it is shown that some spinel oxides (e.g., MgCoO, etc) can be cathode materials for Mg rechargeable batteries around 150 °C.

Roles of transition metals interchanging with lithium in electrode materials.

Roles of antisite transition metals interchanging with Li atoms in electrode materials of Li transition-metal complex oxides were clarified using a newly developed direct labeling method, termed powder diffraction anomalous fine structure (P-DAFS) near the Ni K-edge. We site-selectively investigated the valence states and local structures of Ni in Li0.89Ni1.

Bulk-nanoporous-silicon negative electrode with extremely high cyclability for lithium-ion batteries prepared using a top-down process.

We synthesized freestanding bulk three-dimensional nanoporous Si using dealloying in a metallic melt, a top-down process. Using this nanoporous Si, we fabricated negative electrodes with high lithium capacity, nearing their theoretical limits, and greatly extended cycle lifetimes, considerably improving the battery performance compared with those using electrodes made from silicon nanoparticles. By operating the electrodes below the accommodation volume limit of their pores, we prolonged their cycle lifetime.

Time-resolved coherent diffraction of ultrafast structural dynamics in a single nanowire.

The continuing effort to utilize the unique properties present in a number of strongly correlated transition metal oxides for novel device applications has led to intense study of their transitional phase state behavior. Here we report on time-resolved coherent X-ray diffraction measurements on a single vanadium dioxide nanocrystal undergoing a solid-solid phase transition, using the SACLA X-ray Free Electron Laser (XFEL) facility. We observe an ultrafast transition from monoclinic to tetragonal crystal structure in a single vanadium dioxide nanocrystal.

Three-dimensional nanoelectrode by metal nanowire nonwoven clothes.

Metal nanowire nonwoven cloth (MNNC) is a metal sheet that has resulted from intertwined metal nanowires 100 nm in diameter with several dozen micrometers of length. Thus, it is a new metallic material having both a flexibility of the metal sheet and a large specific surface area of the nanowires. As an application that utilizes these properties, we propose a high-cyclability electrode for Li storage batteries, in which an active material is deposited or coated on MNNC.

Elastic constant measurement of Ni-base superalloy with the RUS and mode selective EMAR methods.

This paper reports the elastic constants of the Ni-base single crystal superalloy (TMS-26) with a rafted (lamellar) structure having tetragonal symmetry. The elastic constants have been measured at room temperature with the resonance ultrasound spectroscopy method and the mode-selective electromagnetic acoustic resonance method. The value of the elastic constant C33 (250.