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[en] The copper-based polyanion compounds Li_6CuB_4O_1_0 and Li_2CuP_2O_7 were synthesized using a conventional solid-state reaction, and their electrochemical properties were determined. Li_6CuB_4O_1_0 showed reversible capacity of 340 mA g"−"1 at the first discharge–charge process, while Li_2CuP_2O_7 showed large irreversible capacity and thus low charge capacity. Ex situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements revealed that the electrochemical Li"+ intercalation/deintercalation reaction in Li_6CuB_4O_1_0 occurred via reversible Cu"2"+/Cu"+ reduction/oxidation reaction. These differences in their discharge/charge mechanisms are discussed based on the strength of the Cu–O covalency via their inductive effects. - Graphical abstract: Electrochemical properties for Cu-based polyanion compounds were investigated. The electrochemical reaction mechanisms are strongly affected by their Cu–O covalentcy. - Highlights: • Electrochemical properties of Cu-based polyanion compounds were investigated. • The Li"+ intercalation/deintercalation reaction progressed in Li_6CuB_4O_1_0. • The electrochemical displacement reaction progressed in Li_2CuP_2O_7. • The strength of Cu–O covalency affects the reaction mechanism.
[en] Androgen deprivation therapy (ADT) decreases bone mineral density (BMD) and increases the risk of fracture in men with prostate cancer. Smith has stated that prostate cancer patients show a degradation of BMD prior to ADT. We, therefore, studied the bone dynamics in Japanese prostate cancer patients prior to ADT. BMD of the total hip, femoral neck, lumbar spine and forearm were measured by dual-energy x-ray absorptiometry (DEXA) before treatment in 53 prostate cancer patients without bone metastasis and in 16 patients with bone metastasis. Bone metabolism measurements of serum NTX and serum BAP were also carried out before treatment in 62 prostate cancer patients without bone metastasis and 22 patients with bone metastasis. Measurements in the total hip of nine of the 53 patients without bone metastasis indicated osteoporosis. Measurements of the femoral neck in eleven of the 53 patients indicated osteoporosis. Results show that Japanese prostate cancer patients without bone metastasis do not suffer from bone density degradation prior to ADT; only the Z score of the forearm showed a minus value. Serum NTX and serum BAP were significantly elevated in prostate cancer patients with bone metastasis compared with those without bone metastasis. No screening guidelines currently exist; however, patients at risk of decreased BMD should be screened and treated to prevent consequent fractures. Serum NTX and BAP monitoring of prostate cancer patients might facilitate the timely diagnosis of bone metastasis. (author)
[en] Lithium intercalation in a lithium excess layered material Li2RuO3 was investigated using two-dimensional model electrodes with a restricted reaction plane of (002). Li2RuO3 films were synthesized on Al2O3(0001) substrate by a pulsed laser deposition, and X-ray diffraction measurements confirmed epitaxial growth of Li2RuO3(002). Electrochemical characterization using cyclic voltammetry and charge/discharge measurements indicated electrochemical reactions with a discharge capacity of 200 mAh g−1 for the film deposited at 400 °C followed by post-annealing at 550 °C. The electrochemical activity on the (002) plane indicated three-dimensional lithium diffusion in the two-dimensional layered rocksalt structure through the lithium sites in the transition metal layer. - Highlights: ► Epitaxial Li2RuO3 (002) films were successfully synthesized on Al2O3 (0001). ► Li2RuO3 (002) films exhibited a discharge capacity of 200 mAh g–1. ► 3-dimensional Li diffusion was confirmed in the 2-dimensional layered structure. ► Mechanistic studies using epitaxial films clarify the intercalation mechanism.
[en] Highlights: • Na3PS4 base solid electrolytes were fabricated by various synthetic routes. • The formation of phases in Na3+5xP1–xS4 depends on reaction conditions. • Tetragonal phase III showed the highest conductivity of 3.39 × 10-3 S cm-1at 25 °C. • Structural analysis revealed the 3D conduction pathway in the tetragonal phase III. • Na3PS4 functions as a solid electrolyte in all-solid-state sodium batteries. - Abstract: Sodium superionic conductors are highly promising as solid electrolytes for all-solid-state sodium batteries, with the capacity to improve energy and power density of liquid-electrolyte-based batteries and to address their safety issues. However, the ionic conductivity of sodium electrolytes remains roughly one order of magnitude lower than that of lithium systems. Herein, we report a synthesis method for a sodium superionic conductor, tetragonal Na3PS4, with an ionic conductivity of 3.39 × 10−3 Scm−1 at 25 °C—the highest value yet reported among sulfide-type sodium conductors. The high conductivity is achieved through quenching from 700 °C, which introduces sodium vacancies, and annealing at 450 °C, which increases vacancies and expands lattice volume. The phase is comprised of a framework of isolated PS4 tetrahedra, with partial distribution of Na over 3D pathways. The high intrinsic conductivity together with low grain boundary contribution and soft mechanical properties make Na3PS4 a promising candidate for sodium solid electrolytes.
[en] Lithium superionic conductors with the Li10GeP2S12 (LGPS)-type structure are promising materials for use as solid electrolytes in the next-generation lithium batteries. A novel member of the LGPS family, Li9.42Si1.02P2.1S9.96O2.04 (LSiPSO), and its solid solutions were synthesized 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 LSiPSO as the separator showed excellent performance with a high reversibility of 100%. Thus, oxygen doping is an effective way of improving the electrochemical stability of LGPS-type structure.
[en] Highlights: •Composite sulfur electrodes are prepared by high-temperature mechanical milling. •The composite exhibited a high discharge capacity of greater than 1200 mAh g−1. •Novel structure unit forms via a reaction between thio-LISICON and sulfur. •Liquid phase sulfur prevents severe decompositions of materials employed. -- Abstract: Composite sulfur electrodes are prepared by high-temperature mechanical milling (443 K) for use in all-solid-state lithium–sulfur batteries, and their structures and electrochemical properties are investigated. Composites comprising sulfur, acetylene black, and a Li3.25Ge0.25P0.75S4 solid electrolyte are fabricated by planetary ball milling using a temperature-controlled system. The composite electrode exhibits a high discharge capacity of greater than 1200 mAh g−1 and a good cycle capability. As a result of high-temperature milling, composites are formed, incorporating novel structural units from the reaction between sulfur and the solid electrolyte, along with their intrinsic characteristics. Hence, high-temperature milling demonstrates promise for the fabrication of a composite electrode exhibiting high, reversible electrochemical activities for use in an all-solid-state lithium–sulfur battery.
[en] The ionic conductivities of new perovskite-structured lithium–strontium–aluminum/gallium–tantalum oxides were investigated. Solid solutions of the new perovskite oxides, (Li_xSr_1_−_x)(Al_(_1_−_x_)_/_2Ta_(_1_+_x_)_/_2)O_3 and (Li_xSr_1_−_x)(Ga_(_1_−_x_)_/_2Ta_(_1_+_x_)_/_2)O_3, were synthesized using a ball-milled-assisted solid-state method. The partial substitution of the smaller Ga"+"3 for Ta"+"5 resulted in new compositions, the structures of which were determined by neutron diffraction measurements using a cubic perovskite structural model with the Pm−3m space group. Vacancies were introduced into the Sr(Li) sites by the formation of solid solutions with compositions (Li_xSr_1_−_x_−_y☐_y)(Ga_[_(_1_−_x_)_/_2_]_−_yTa_[_(_1_+_x_)_/_2_]_+_y)O_3, where the composition range of 0≤y≤0.20 was examined for x=0.2 and 0.25. The highest conductivity, 1.85×10"−"3 S cm"−"1 at 250 °C, was obtained for (Li_0_._2_5Sr_0_._6_2_5☐_0_._1_2_5)(Ga_0_._2_5Ta_0_._7_5)O_3 (x=0.25, y=0.125). Enhanced ionic conductivities were achieved by the introduction of vacancies at the A-sites. - Graphical abstract: Novel lithium-conducting oxides with the cubic perovskite structure (Li_xSr_1_−_x_−_y☐_y)(Ga_[_(_1_−_x_)_/_2_]_−_yTa_[_(_1_+_x_)_/_2_]_+_y)O_3 provide a specific solid-solution region with various x and y values, exhibiting the highest ionic conductivity (1.85 S cm"−"1 at 250 °C) for (Li_0_._2_5Sr_0_._6_2_5☐_0_._1_2_5)(Ga_0_._2_5Ta_0_._7_5)O_3 (x=0.25, y=0.125 in (Li_xSr_1_−_x_−_y☐_y)(Ga_[_(_1_−_x_)_/_2_]_−_yTa_[_(_1_+_x_)_/_2_]_+_y)O_3). The vacancies (☐) introduced into the A-sites contribute to the enhancement of lithium diffusion in the perovskite structure because of the enlargement of the bottleneck size and suppression of the interaction between lithium and oxygen. - Highlights: • The perovskite-structured novel Li–Sr–Al/Ga–Ta oxides were investigated. • The Ga cation offers a larger bottleneck by increasing the B−O bond length. • The greater conductivity was observed upon Ga-containing perovskite. • The ionic conductivity was improved by the introduction of vacancies into A-site
[en] The novel lithium-ion conductor Li7Ge3PS12 was synthesized by slow cooling from the ternary Li2S–GeS2–P2S5 system, and was shown to exhibit a cubic argyrodite-type structure. The phase composition was determined by varying the ratio of starting materials; the observed monophasic properties were close to those for the Li7Ge3PS12 composition. The lattice parameter (a =9.80192(3) Å) of Li7Ge3PS12 was slightly smaller than that of Li7PS6 (a =9.993 Å), indicating that substitution of a Li cation by the smaller Ge cation contracted the cubic lattice. In addition, the novel structure consisted of a framework composed of four isolated (Ge/P)S4 tetrahedra. Li+ ions occupied tetrahedral sites within the framework, forming a three-dimensional conduction pathway. Finally, Li7Ge3PS12 exhibited a high ionic conductivity of 1.1×10−4 S cm−1 at 25 °C and an activation energy of 25 kJ mol−1. - Graphical abstract: A novel Li7Ge3PS12 solid lithium ion conductor, with cubic argyrodite strucuture, shows high ion conductivity of 1.1×10–4 S cm–1 with an activation energy of 25 kJ mol–1. The argyrodite structure consists of (Ge/P)S4 tetrahedra units along with partial occupation of lithium and germanium at 48 h site. - Highlights: • A novel lithium-ion conductor Li7Ge3PS12 was detected. • This was achieved through slow cooling of the ternary Li2S–GeS2–P2S5 system. • This novel conductor revealed a cubic argyrodite-type structure. • Li7Ge3PS12 exhibited a high ionic conductivity of 1.1×10−4 S cm−1 at 25 °C. • These properties will aid in the design of superior lithium-ion conductors.