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To improve the cycling performance of carbon-coated SiO (SiO–C) as a high-capacity negative electrode material, we have used X-ray absorption fine structure measurements to assess the electronic state of Si and investigate phase changes during charge/discharge cycles. The results suggest that Si 4 + continuously absorbs Li during the charging process, mainly forming Li 4 SiO 4 . Li silicates with a lower valence are also formed. Neutral Si and Si 2 + mainly contribute to Li insertion during the initial charging stage, whereas low-valence oxides like Si 1 + and Si 2 + form during the middle charging stage. The fully charged state contains all Si phase states. These results suggest that during the discharge process, Li is mainly released from composites with Si 2 + -oxidation state, and Li is partially released from Li 4 SiO 4 at a higher voltage forming Si 0 . Si O composites with Si 1 + –Si 3 + reversibly shift to a higher valence state during cycling. We confirmed that Li 4 SiO 4 readily releases Li after long-term cycling, and Si O composites at the end of the cycle change to a higher valence state. The results indicate that disproportionation is a primary factor decreasing cell cycle performance and confirm that it is possible to design LiB cells with improved cycling performance by controlling the disproportionation linked to the structural deterioration of SiO–C.

To improve the cycling performance of the carbon-coated SiO (SiO-C) as a high capacity anode material, the charge–discharge mechanism and the structural changes in the bulk during long-term cycling were investigated by the solid-state nuclear magnetic resonance (NMR). The electron conductivity of the SiO-C was improved following the charging state, whereas the electrical resistivity tended to be low. It suggested that from the beginning of the discharge to its half state (at the low potential side), the silicide reaction is predominant, whereas at the terminal phase of the discharge (at the high potential side), the release of Li from the silicate is predominant. Upon designing a negative cutoff potential of 1.1 V, the cell's cycling performance was checked. The results suggested that during repeated charge-discharge cycling, Li release from the silicate decreased and a disproportionation reaction occurred which produced Si and Li4SiO4. It was confirmed that a part of the cycle performance was improved by designing a battery utilizing the low potential side which is supposed to increase the electron conductivity and suppressed the disproportionation.

The Li pre-doping free cells using tin-phosphate glass (GSPO)-silicon composite anodes and lithium-rich layered oxide (LR-NMC) cathode were developed, in which the irreversible capacity of the cathode was utilized in order to compensate that of the anode. The irreversible capacity was equalized to that of the cathode at a Si/(GSPO + Si) mass ratio, r , of 0.8. The cell using the composite anode of r = 0.8 displayed a discharge capacity of 187 mAh g −1 as the cathode capacity at 30 °C and the 0.1C-rate. The long cycle performance of over 100 charge–discharge cycles was achieved. The cells also showed an excellent high- and low-temperature performance and a good rate performance. A stable performance was observed for over 50 cycles at 60 °C and the 0.5C-rate, and a high capacity of ca. 100 mAh g −1 as the cathode capacity even at −20 °C and the 0.2C-rate. The cell could discharge even at the 10C-rate. Furthermore, the Li pre-doping free cell showed an outstanding safety performance during the nail penetration test. When the 1500 mAh cell using the composite anode was penetrated by a nail, no thermal runaway was observed during the test.

Olivine lithium manganese phosphate (LiMnPO 4 ) becomes research focus because of its high energy density and improved thermal stability. However, its application in lithium ion batteries suffers severely from poor electrochemical activity due to low conductivity and structural instability upon the charge and discharge process. By applying a high-energy ball-milling method we succeed in improving the capacity delivery and rate capability. LiMnPO 4 materials ball-milled without or with acetylene black are able to deliver a high capacity of 135 and 127 mAh g −1 , respectively, more than 50% greater than the pristine one. Particularly, the latter also shows an improved discharge plateau and stable cyclability. High-energy synchrotron radiation X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, laser particle analysis, and galvanostatic charge and discharge are employed to understand the effect of ball-milling on the LiMnPO 4 material.

Lithium vanadium metasilicate (LiVSi 2 O 6 ) with pyroxene structure has been exploited as an electrode material for Li-ion batteries. Galvanostatic charge and discharge tests show that LiVSi 2 O 6 is able to deliver a capacity of 85 mAh g −1 at 30 °C, and a high capacity of 181 mAh g −1 at 60 °C. The high capacity is believed to be due to the reactions of V 3+ /V 4+ and V 2+ /V 3+ redox couples, accompanied by the excess 0.42 Li + insertion into the lattice forming a Li-rich phase Li 1.42 VSi 2 O 6 . High-energy synchrotron XRD combined with the Rietveld refinement analysis confirms that the electrochemical delithiation–lithiation reaction proceeds by a single phase redox mechanism with an overall volume variation of 1.9% between LiVSi 2 O 6 and its delithiated state, indicating a very stable framework of LiVSi 2 O 6 for Li + ions extraction–insertion.

Well-crystallized LiFePO 4 nanoparticles have been directly synthesized in a short time via hydrothermal process in the presence of organic acid, e.g. citric acid or ascorbic acid. These acid-mediated LiFePO 4 products exhibit a phase-pure and nanocrystal nature with size about 50–100 nm. Two critical roles that the organic acid mediator plays in hydrothermal process are recognized and a rational mechanism is explored. After a post carbon-coating treatment at 600 °C for 1 h, these mediated LiFePO 4 materials show a high electrochemical activity in terms of reversible capacity, cycling stability and rate capability. Particularly, LiFePO 4 mediated by ascorbic acid can deliver a capacity of 162 mAh g −1 at 0.1 C, 154 mAh g −1 at 1 C, and 122 mAh g −1 at 5 C. The crystalline structure, particle morphology, and surface microstructure were characterized by high-energy synchrotron X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and Raman spectroscopy, respectively. And the electrochemical properties were thoroughly investigated by galvanostatic test and electrochemical impedance spectroscopy (EIS).

The detailed structural change in the charge–discharge process was investigated for the 20 mol% aluminum-substituted α-nickel hydroxide by using high-energy synchrotron X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM) analysis. The 20 mol% aluminum-substituted α-nickel hydroxide showed the α-Ni(OH) 2 /γ-NiOOH phase transformation in the charge–discharge process. The structural refinement has been done successfully on the basis of two phase models of the ideal phases and the fault ones, including the occupation sites for the potassium ions and H 2 O (OH − ) molecules. The substituted aluminum ions were situated on both nickel sites and 18h sites in the interlayer. The α-Ni(OH) 2 structure would be stabilized by the presence of the aluminum ions on the 18h sites. The α-Ni(OH) 2 phases were transformed to the β-Ni(OH) 2 phases after 50 cycles because the aluminum ions on the 18h sites would be migrated from the bulk to the surface.

Under partial charge–discharge cycling conditions at a state of charge (SoC) of 50–70%, a greater effect on the suppression of the memory effect, which occurs in rechargeable alkaline batteries containing a Ni-electrode, was observed using conductive materials such as nano-sized Co(OH) 2 and CoO powders in the Ni-electrode. The nano-sized Co(OH) 2 powder, prepared by the reverse micelle method, consisted of approximately 15–60 nm spherical-shaped particles. The Ni–Cd cells containing approximately 15- or 20-nm-sized Co(OH) 2 powder and 18 nm CoO powder in the Ni-electrode did not show any memory effect after a 150-cycle partial charge–discharge cycling test, and γ-NiOOH, which is mainly the origin of the memory effect, was not detected in the Ni-electrode, whereas the Ni–Cd cell containing the same content of 500 nm Co(OH) 2 powder and 18 nm CoO in the Ni-electrode showed the memory effect. The nano-sized Co(OH) 2 powder could be more homogeneously dispersed in the Ni-electrode when compared to the 500 nm powders and might develop a superior electro-conductive network between the Ni(OH) 2 particles.

We found that a carbon additive could suppress the unfavorable generation of polycrystals in a crucible without reduction in the yield of GaN in the Na flux method. The suppression of polycrystals due to the effect of carbon significantly increased the growth rate of liquid phase epitaxy (LPE), which has been the biggest problem of the Na flux LPE, and enabled an increase in the growth rate above 20 μm/h. A 3 mm-thick 2 in GaN crystal was obtained for the first time. In addition, the carbon additive was found to have another effect in that the nonpolar face could be widely developed. SIMS measurements revealed that carbon added into a Ga–Na mixed melt was hardly taken into LPE crystals, although carbon did have some favorable effects.

The detailed phase transformation in the charge-discharge process for the nickel hydroxide electrode have been examined by using the high-energy synchrotron X-ray absorption fine structure (XAFS) and X-ray diffraction (XRD). The structural refinement for the β-Ni(OH)2 and the β-NiOOH have been done successfully on the basis of two phase models of the ideal and fault phases. At 0% of SOC, it was found that the sample consisted of 80% of the ideal β-Ni(OH)2 phases and 20% of the fault ones. At 100% of SOC, the ideal and fault β-Ni(OH)2 phases were transformed to the ideal and fault β-NiOOH phases, respectively. It was found that the fault phases contained a larger amount of intercalated potassium ions and H2O (OH−) than the ideal ones. At 150% of SOC, the only ideal β-NiOOH phases was transformed to the ideal γ-NiOOH phases, accompanied by further intercalation of the potassium ions and H2O (OH−) into the interlayer

The effect of the addition of Li or Ca to Ga–Na melt on the promotion of nitrogen dissolution was examined quantitatively in the growth of GaN single crystals using the sodium flux method. The addition of Li or Ca to Ga–Na melt increased both the solubility of solid GaN and that of gaseous nitrogen against the solution. The increase in the solubility of gaseous nitrogen seems to be caused by additives having a high binding energy with nitrogen. We measured the solubility of GaN and that of gaseous nitrogen against Ga–Na, Ga–Na–Li and Ga–Na–Ca melt in this study. On the basis of these data, we clarified the relationship between the N/Ga ratio in the solution and the coloration of GaN crystals grown in each system, and between changes in the yield of GaN and the absolute value of supersaturation.

In the growth of GaN single crystal using the Na flux method, we succeeded in clarifying the role of Na in promoting nitrogen dissolution in the Ga-Na melt system above 900 K. At the gas-liquid interface of high temperature Ga-Na melt, Na functions to ionize the nitrogen gas. The ionization of the nitrogen gas results in drastic increase of nitrogen dissolution in the melt. In consequence, these synthesize GaN single crystals easily. On the other hand, the addition of a minor amount of Ca or Li to the Ga-Na melt system also increases the nitrogen dissolution. However, the additives function to maintain the nitrogen dissolved in the Ga-Na melt, which results in drastic increase in the nitrogen concentration. In the present study, we report the solubility of GaN in the Ga-Na system and the threshold pressure of nitrogen gas to grow GaN. On the basis of these data, we propose a growth mechanism of GaN and the role of additives to maintain nitrogen.

The dependency of LPE growth rate and dislocation density on supersaturation in the growth of GaN single crystals in the Na flux was investigated. When the growth rate was low during the growth of GaN at a small value of supersaturation, the dislocation density was much lower compared with that of a substrate grown by the Metal Organic Chemical Vapor Deposition method (MOCVD). In contrast, when the growth rate of GaN was high at a large value of supersaturation, the crystal was hopper including a large number of dislocations. The relationship between the growth conditions and the crystal color in GaN single crystals grown in Na flux was also investigated. When at 800 °C the nitrogen concentration in Na–Ga melt was low, the grown crystals were always tinted black. When the nitrogen concentration at 850 °C was high, transparent crystals could be grown.

We investigated the threshold pressure necessary for heterogeneous nucleation of GaN using pure nitrogen gas and nitrogen gas mixed with ammonia in the Na-flux method. In our investigation, we found the appropriate pressure region for nucleating GaN and growing GaN seed crystals without additional heterogeneous nucleation. This study revealed that the threshold pressure to nucleate GaN decreases as the ratio of ammonia increases. We also succeeded in reducing the nucleation threshold pressure from 30 to 10 atm by using nitrogen gas with 25–40% ammonia gas instead of pure nitrogen gas. We confirmed that seed growth without additional nucleation is possible in both pure nitrogen and nitrogen gas mixed with ammonia at pressures below those required for nucleation.

A new wet limestone−gypsum process for flue gas desulfurization (FGD) has been developed. The main difference compared to a conventional wet FGD process is the ability of the new process to utilize granular limestone directly as a desulfurizing reagent. Thus, the pulverizing of limestone, which causes power consumption, can be avoided. The performance of the wet FGD process using granular limestone was confirmed to be equal to or higher than that of a conventional process in various tests. Tests were also performed in a 2000 m3Normal/h demonstration plant introducing actual flue gas of various types of coals at Matsuura Thermal Power Station of the Electric Power Development Co., Ltd. (EPDC) in Japan. It was also confirmed that the desulfurization performance of the granular limestone FGD process was not decreased by aluminum−fluorine-containing compounds in the absorbing slurry as much as in the pulverized limestone case. In this new wet FGD process, gypsum quality was also higher than that in a conventi...

We developed a new liquid phase epitaxy (LPE) growth method for growing large GaN single crystals. In this method, the homo-epitaxial growth of the GaN crystal proceeds by nitrogen dissolution against a Na-Ga solution film coating the GaN thin-film substrate. A growth rate of 4 µm/h was achieved though nitrogen pressure was relatively low at 9.5 atm. Furthermore, the GaN film grown by this method showed a flat surface.

We found the yield of GaN grown in a Li-Na flux system to be much higher than that grown in Na flux. Nitrogen dissolution seemed to increase with Li in solution, which promotes the growth of GaN crystals. In this paper, we report that the yield of GaN and habit modifications greatly depend on the composition of the Li-Na flux system and that GaN can be grown in a pure Li flux at about 50 atm.

The structural analysis for the cobalt oxyhydroxide has been done by using high-energy synchrotron X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) analysis. The relationship between the structure and the electrical conductivity for cobalt oxyhydroxide was investigated. The structural refinement for cobalt oxyhydroxide heat-treated in the temperature range of 80-160°C has been done successfully on the basis of two phase models (L and S phase) with large and small c lattice constants. With increasing treatment temperature, the phase abundance for the L phases was increased, whereas the one for the S phases was decreased. By heat-treatment above 100°C, the cobalt ions for the cobalt oxyhydroxide were oxidized to the higher oxidation state over 3. The electrical resistivity was extremely decreased by treatment temperatures above 100°C. The increase in the electrical conductivity for the cobalt oxyhydroxide could be explained by the increase in cobalt oxidation state.