Showing papers by "Kota Suzuki published in 2016"

High-power all-solid-state batteries using sulfide superionic conductors

Abstract: Compared with lithium-ion batteries with liquid electrolytes, all-solid-state batteries offer an attractive option owing to their potential in improving the safety and achieving both high power and high energy densities. Despite extensive research efforts, the development of all-solid-state batteries still falls short of expectation largely because of the lack of suitable candidate materials for the electrolyte required for practical applications. Here we report lithium superionic conductors with an exceptionally high conductivity (25 mS cm−1 for Li9.54Si1.74P1.44S11.7Cl0.3), as well as high stability ( ∼0 V versus Li metal for Li9.6P3S12). A fabricated all-solid-state cell based on this lithium conductor is found to have very small internal resistance, especially at 100 ∘C. The cell possesses high specific power that is superior to that of conventional cells with liquid electrolytes. Stable cycling with a high current density of 18 C (charging/discharging in just three minutes; where C is the C-rate) is also demonstrated. The development of all-solid-state batteries requires fast lithium conductors. Here, the authors report a lithium compound, Li9.54Si1.74P1.44S11.7Cl0.3, with an exceptionally high conductivity and demonstrate that all-solid-state batteries based on the compound have high power densities.

Bulk-Type All Solid-State Batteries with 5 V Class LiNi0.5Mn1.5O4 Cathode and Li10GeP2S12 Solid Electrolyte

Abstract: All solid-state batteries are of key importance in the development of next-generation energy storage devices with high energy density. Herein, we report the fabrication and operation of bulk-type 5 V-class all solid-state batteries consisting of LiNi0.5Mn1.5O4 cathode, Li10GeP2S12 solid-electrolyte, and Li metal anode. The 1st discharge capacity is about 80 mAh g–1 with an average voltage of 4.3 V. The discharge capacity gradually decreases during the subsequent cycles. X-ray diffraction and electrochemical impedance spectroscopy measurements reveal that the capacity fading results from the growth of a resistive interfacial layer on the cathode composite. The development of suitable conductive additive and sulfide solid electrolyte materials is essential for the development of high-voltage all solid-state batteries.

Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

Abstract: Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries.

On the Mechanism of Crystal Water Insertion during Anomalous Spinel-to-Birnessite Phase Transition

Abstract: Hydrated materials contain crystal water within their crystal frameworks and can exhibit extraordinary properties as a result. However, a detailed understanding of the mechanism involved in the hydration process is largely lacking, because the overall synthesis process is very difficult to monitor. Here, we elucidate how the insertion of crystal water mediates an anomalous spinel-to-Birnessite phase transition during electrochemical cycling in aqueous media. We find that, at the initial stage of the phase transition, crystal water is inserted into the interlayer space between MnO6 layers in the form of a hydronium ion (H3O+). The H3O+ insertion is chemically driven in the reverse (reducing) direction to the applied anodic (oxidizing) electric field, stabilizing the structure and recovering the charge balance following the deinsertion of Mn2+. A comparative investigation using various electrolyte solutions revealed that the H3O+ insertion competes with the insertion of other ionic charge carriers (Li+, Na+...

Lithium Superionic Conductor Li9.42Si1.02P2.1S9.96O2.04 with Li10GeP2S12-Type Structure in the Li2S–P2S5–SiO2 Pseudoternary System: Synthesis, Electrochemical Properties, and Structure– Composition Relationships

Abstract: Lithium superionic conductors with the Li10GeP2S12 (LGPS)-type structure are promising materials for use as solid electrolytes in next-generation lithium batteries. A novel member of the LGPS family, Li9.42Si1.02P2.1S9.96O2.04, and its solid solutions were synthesised by quenching from 1273 K in the Li2S–P2S5–SiO2 pseudoternary system. The material exhibited an ionic conductivity as high as 3.2×10−4 S cm−1 at 298 K, as well as the high electrochemical stability to lithium metal, which was improved by the introduction of oxygen into the LGPS-type structure. An all-solid-state cell with a lithium metal anode and Li9.42Si1.02P2.1S9.96O2.04 as the separator showed excellent performance with a high coulomb efficiency of 100%. Thus, oxygen doping is an effective way of improving the electrochemical stability of LGPS-type structure.

Fabrication and All Solid-State Battery Performance of TiS2/Li10GeP2S12 Composite Electrodes

Abstract: TiS2/Li10GeP2S12 composite electrodes were fabricated using a mill pot rotator, and their electrochemical properties were investigated in all solid-state batteries of TiS2 cathode/Li10GeP2S12 solid-electrolyte/In-Li anode. The batteries compressed under a pressure of 19 MPa demonstrated poor cycle stability and rate capability because of the deterioration of physical contact between the TiS2 and the Li10GeP2S12. The battery performance was considerably improved by applying a pressure of 228 MPa throughout the electrochemical cycling while maintaining the contact area. The battery delivered the reversible a capacity of over 160 mAh・g−1 under 1 C operation with high capacity retention. [doi:10.2320/matertrans.Y-M2016804]

Dynamic Behavior at the Interface between Lithium Cobalt Oxide and an Organic Electrolyte Monitored by Neutron Reflectivity Measurements

Abstract: Clarification of the interaction between the electrode and the electrolyte is crucial for further improvement of the performance of lithium-ion batteries. We have investigated the structural change at the interface between the surface of a 104-oriented epitaxial thin film of LiCoO2 (LiCoO2(104)), which is one of the stable surfaces of LiCoO2, and an electrolyte prepared using a carbonate solvent (1 M LiClO4 in ethylene carbonate and dimethyl carbonate) by in situ neutron reflectivity measurements. Owing to the decomposition of the organic solvent, a new interface layer was formed after contact of LiCoO2(104) with the electrolyte. The composition and thickness of the interface layer changed during Li+ extraction/insertion. During Li+ extraction, the thickness of the interface layer increased and the addition of an inorganic species is suggested. The thickness of the interface layer decreased during Li+ insertion. We discuss the relationship between battery performance and the dynamic behavior at the interface.

Lithium intercalation in the surface region of an LiNi1/3Mn1/3Co1/3O2 cathode through different crystal planes

Abstract: Epitaxial LiNi1/3Co1/3Mn1/3O2 film electrodes with orientations of (104), (1−18) and (003) were fabricated on SrRuO3/SrTiO3 by pulsed laser deposition. The films have a thickness of 23.8 to 25.0 nm and a flat surface with a roughness of approximately 2 nm, which offered a model system for clarifying the reaction plane dependencies of lithium intercalation at the LiNi1/3Co1/3Mn1/3O2 surface. All reaction planes delivered reversible lithium intercalation for electrochemical charging–discharging between 3.0 V and 4.3 V (vs. Li/Li+). The (104) surface exhibited reversible behavior at a higher operation voltage between 3.0 V and 4.5 V, but the (1−18) and (003) planes showed fading of the discharge capacity and average discharge voltage. The anisotropic stability of the surface region indicates the importance of crystallographic facet control for the development of an LiNi1/3Co1/3Mn1/3O2 cathode with high cycle stability.

Neutron reflectometry analysis of Li4Ti5O12/organic electrolyte interfaces: characterization of surface structure changes and lithium intercalation properties

Abstract: The structure changes and lithium intercalation properties in the surface region of Li4Ti5O12 were investigated using epitaxial Li4Ti5O12(111) film model electrodes. The discharge–charge measurements, which were conducted with 1 mol/dm3 LiPF6-containing propylene carbonate, revealed that a 23.8 nm-thick film exhibited a small capacity of 115 mA h/g compared to the theoretical value of 175 mA h/g. In situ neutron reflectometry and ex situ x-ray diffractometry and reflectometry indicated that an irreversible phase change had occurred in the 10-nm surface region of Li4Ti5O12 during the initial reaction processes. The level of deterioration of the surface structure was significantly reduced by decreasing the LiPF6 concentration; in addition, side reactions of the cell components with the electrolyte species, and their products, may be associated with the deterioration of the Li4Ti5O12 surface. The surface reactions have a significant impact on the capacity of lithium intercalation in nano-sized Li4Ti5O12.

Synthesis, Crystal Structure, and the Ionic Conductivity of New Lithium Ion Conductors, M-Doped LiScO2 (M = Zr, Nb, Ta)

Abstract: New lithium ion conductors of M-doped LiScO2 (M = Zr, Nb, and Ta) were synthesized by a solid-state reaction method. Peak shifts of the X-ray diffraction patterns revealed the formation of solid solutions with aliovalent cation doping. In addition, increase in the ionic conductivity by the M doping is indicated. The highest total conductivity of 7.94 × 10 S cm at 623 K with an activation energy of 88 ± 5 kJ mol was observed for the Zr doped sample in the systems. The Zr doped system showed the largest solid solution limit in Li1−xSc1−xZrxO2 (x ≈ 0.1) and continuous increase of the conductivity with increasing x. Structural analysis by Rietveld refinement indicated that the lattice expansion and lithium-ion vacancy formation by the Zr doping in the structure, which could contribute to the increase in the ionic conductivity.

Social ability test method and social ability test system

Abstract: PROBLEM TO BE SOLVED: To provide a social ability test method and a social ability test system in which social ability of a subject can be measured efficiently and objectively in a short time by an extremely simple device and procedure, and can be collected.SOLUTION: A human voice is passed for an instant in a small sound volume for a white noise of loud sound. A subject hearing this human voice answers by pressing a push button switch. An indicator showing the subject having pressed the push button switch is provided in an operation panel displayed in a display unit of an information processing apparatus because the subject is often an infant.SELECTED DRAWING: Figure 1