Electroceramics in Japan IX

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Authors: Kenichi Myoujin, Takashi Ogihara, Nobuo Ogata, Koji Nakane, Takayuki Kodera, Suetaka Omura, Masao Uede, Kazuya Higeta
Abstract: Spherical LiNi1/3Mn1/3Co1/3O2 precursor powders were synthesized by aerosol plasma pyrolysis using aqueous solution of metal nitrate. XRD, SEM, TEM and BET analysis were used for determi- nation of the composition, morphology, particle size and surface area. SEM observation showed that the size of as-prepared particles were about 200 nm. The value of geometrical standard deviation (σg) calculated from the particle size distribution was 1.20, suggesting that the particle size distribution was narrow. The crystal phase of LiNi1/3Mn1/3Co1/3O2 was resulted in layered rock salt structure with R3m space group. The rechargeable capacity of LiNi1/3Mn1/3Co1/3O2 was about 142-175 mAh/g. The discharge capacity of LiNi1/3Mn1/3Co1/3O2 decreased with increasing cycle number. However, the cycling stability of Li(Ni1/3Mn1/3Co1/3)O2 powders that aerosol plasma pyrolysis process offered superior performance to ultrasonic spray pyrolysis process.
Authors: Masashi Higuchi, Kaori Uchida, Keiichi Katayama, Yasuo Azuma
Abstract: LiFePO4 powders were prepared by a citric acid complex method. The effects of source composition and firing conditions on the formation of LiFePO4 were investigated. Single phase and well-crystallized LiFePO4 powders were obtained at 500°C for 5h. The particle size of the obtained powder is smaller than that of powder prepared by the conventional solid-state reaction method.
Authors: Sang Wook Woo, Kaoru Dokko, Kiyoshi Kanamura
Abstract: Three dimensionally ordered macroporous (3DOM) Li4Ti5O12 was successfully prepared by a colloidal crystal templating process. Colloidal crystal consisting of monodisperse polystyrene particles (1 9m diameter) was used as a template for the synthesis of macroporous Li4Ti5O12. A precursor sol consisting of titanium isopropoxide and lithium acetate was injected into the template, and it was calcined at high temperatures. A macroporous membrane of Li4Ti5O12 with inverse-opal structure was obtained. The prepared material had a spinel-related crystallographic structure. The interconnected pores with uniform size (0.8 9m) were clearly observed on entire part of the membrane. The electrochemical properties of the 3DOM Li4Ti5O12were characterized with cyclic voltammetry and glavanostatic charge-discharge in an organic electrolyte containing a lithium salt. 3DOM Li4Ti5O12 exhibited a discharge capacity of 160 mA h g-1 at the electrode potential of 1.55 V vs. Li/Li+ due to the solid state redox of Ti3+/4+ accompanying with Li+ ion insertion and extraction. The discharge capacity was close to the theoretical capacity (167 mA h g-1). This means that the Li+ insertion and extraction took place at all part of the 3DOM Li4Ti5O12 membrane.
Authors: Yosuke Kawakami, Masaru Miyayama
Abstract: The proton conducting properties of layered metal phosphates hydrates (M (HPO4)2·nH2O (M = Sn, Ti, Zr), MPs) were examined under various humidities at 20−150°C. SnP showed a high conductivity of more than 10-2 S cm-1 under saturated water vapor pressure and a weak humidity dependence of its conductivity at 150°C. The hydrated water content (n) of ZrP was approximately stable at 1 in a wide humidity range of more than 20% at 150°C. The n of SnP varied more widely than that of ZrP; however, the conductivity of SnP remained high even in a low-n range. The short distance between adjacent hydrated water molecules was suggested to be the reason for the high proton conductivity of SnP.
Authors: Minakshi Manickam, Pritam Singh, Touma B. Issa, Stephen Thurgate, Kathryn Prince
Abstract: The electrochemistry of olivine-type iron phosphate (FePO4) as a battery cathode material, in aqueous lithium hydroxide (LiOH), has been investigated. The material forms intercalated LiFePO4 reversibly on electroreduction/oxidation. The formation of Fe3O4 phase, in addition to the regeneration of FePO4 during reverse oxidation of LiFePO4, also occurs. In this regard, the mechanism of FePO4 discharge/charge in aqueous LiOH differs from that in non-aqueous solvents.
Authors: Toyoki Okumura, Ayumi Dodomi, Morihiro Saito, Jun Kuwano
Abstract: The locations and local environments of the Li ions in La0.56Li0.33TiO3 have been investigated by classical molecular dynamics (MD) simulations and first-principles (FP) calculations. The pair correlation functions of Li-O and Li-Ti indicate that the Li ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O2-. This is consistent well with that suggested from previous neutron diffraction and 6Li-NMR studies. The FP calculations suggest a different location of the Li ion in the vicinity of the midpoint between the centers of two adjcent bottlenecks; however it coincides with one of the locations shown by the trajectories simulated with the MD calculations.

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