Kenji Nakane

Synthesis and properties of gallium-doped LiNiO2 as the cathode material for lithium secondary batteries

Gallium-doping to LiNiO2 was investigated, and we found that it is effective to improve the cycling behavior of LiNiO2. The obtained specimen is single phase with hexagonal structure without any other foreign matters such as LiGaO2 by X-ray diffraction measurement. The crystal structure during charging process is stabilized by gallium doping. Hexagonal structure is retained all over the charging state without monoclinic phase and without two hexagonal phase regions which are observed in undoped LiNiO2. Consequently, the crystal lattice parameters change continuously and gradually. The gallium-doped LiNiO2 shows superior rechargeable capacity of 190 mAh/g and retention of more than 95% after 100 cycles in the cycling test between 3.0 and 4.3 V at room temperature. In the cycling test with higher charging voltage (4.4 or 4.5 V), the rechargeable capacity reaches more than 200 mAh/g without significant degradation of cycling behavior. It also demonstrates excellent over-charge resistance.

Design and concept of a Biointeractive Autonomous Underwater Vehicle “BA-1”

To keep the precious protein source, it is thus extremely important to conserve the biodiversity of the ocean and at the same time to make use of its limited space as much as possible without doing any environmental harm. With this broad objective in mind, Tokyo University of Marine Science and Technology (TUMSAT) and Mitsui Engineering & Shipbuilding Co., Ltd. have started a research and development project, “Pen-free Offshore Aquaculture System using Biointeractive Autonomous Underwater Vehicles.” This project is part of a more comprehensive project, “Marine Biotechnology Innovation,” which has been funded by the Japanese government since 2007. In this paper, we propose a concept of a biointeractive AUV that monitors and takes care of schools of fish just like a sheep dog in a ranch. In a future plan of this system, multiple biointeractive AUVs monitor the environment spatially and accurately, feed the fish, monitor the growth of the fish, guide them, and report the data through satellite to the land while charging their batteries by docking with buoys. A first model of the biointeractive AUV “BA-1” has launched in early 2009. The design of the biointeractive AUV “BA-1” is described in this paper. The basic test result of the interaction system for fish is also described briefly.

Development and sea trial of an Autonomous Underwater Vehicle equipped with a sub-bottom profiler for surveying mineral resources

In recent years, Autonomous Underwater Vehicle (AUV) has received much attention as a tool of ocean survey. One of the method for the efficient of hydrothermal deposits investigation is multiple vehicle operation of AUVs. The aim of our work is to development the small and inexpensive AUV and operate together with other AUVs. This paper introduce the first AUV in our project, and show the result for the sea trial of the AUV.

Biointeractive Autonomous Underwater Vehicle “BA-1”

This paper describes the design of a biointeractive AUV that has abilities to monitor schools of fish interactively. In the very large ocean it is very difficult to understand the habits of a swimming fish because the visibility of camera and range of sonar are limited while they swim widely. It is also hard to apply bio-logging techniques to fish because loggers are still large and heavy for them, furthermore, retrieving the data is tough. The biointeractive AUV can stay in the environment where fish is living and swim together with them to monitor their life style. The vehicle has capabilities to give stimulus to fish to observe their behavior caused by the stimulation. Future plan of the biointeractive AUV is to take a role of monitoring the environment spatially and accurately, feeding the fish, monitoring their growth and guiding them in a pen-free offshore aquaculture system. A first model of the biointeractive AUV “BA-1” has launched in early 2009. The length of the vehicle is 3m and the weight in air is about 430kg. The depth rating of the vehicle is 1,000m. It has both hovering and cruising capabilities for operations in test tanks, aquaculture pens and oceans. The design of the biointeractive AUV BA-1 is described with the test results in a test tank and the result of the interaction test with fish in an aquaculture pen.

Development and sea trial of the compact cruising type AUV system

In this paper, we present an overview of two cruising AUVs recently developed by National Maritime Research Institute of Japan. Sharing the same hardware and software architectures, two AUVs divide their responsibilities by employing acoustic bottom survey devices of different purposes. Pursuing the easiness in generating a behavior plan corresponding to a specific mission, pattern-based behavior planner is developed and commonly used by two AUVs. Right after their completion, two AUVs were deployed in Suruga Bay and successfully achieved lots of missions imposed on their trial dives. Results of trial dives of our AUVs are also presented in this paper.

Synthesis and characterization of Ni and Ti substituted Li2MnO3 positive electrode material for lithiumion battery

Global warming caused by CO2 gas can no longer be ignored. Therefore, we are trying to contribute to reducing the problem with our electrolytic technology accumulated so far in our company. Our target is to develop a large of alkaline water electrolysis (AWE) plant with high performance and contribute to problem solving. The performance of AWE is largely classified and influenced by four factors of anode, cathode, separator and cell structure of electrolyzer. Here, the results of electrodes and separators are mainly explained in our evaluation. Considering the use of renewable energy as standard, electricity always fluctuates in the operation of AWE. Therefore, the components of the cell must be sufficient resistant to such fluctuations. Electrode: there are two types of activated coating to reduce the overvoltage of electrode. Our investigation revealed that the anode coating of thermal decomposition is not enough tough, but the dispersion electroplating such as Raney Ni showed good durability against 100 times shutdown. During the shutdown of operation, revers current pass through in the cell. The revers current deteriorates the electrode performance and the phenomena causes difficult for anode coating life. Each saving of anode oxygen overvoltage of thermal and electroplating is around 50 mV and 100 mV compared with bare Ni. Separator: In the AWE, electrolyte is the same in both anode chamber and cathode chamber, so that diaphragm instead of ion exchange membrane can be used as separator. The point of its performance is that low cell voltage and high purity gas can be obtained. Currently, AGFA and KHI diaphragm are considered to be applicable to large-scale AWE plants. The performance of our AWE plant was around1.8 V at 5 kA/m2 and 80oC. Its performance is affected by the electrode to be used. The differences in cell voltage occur from 100 mV to 200 mV. Alkaline water electrolysis is the easiest methods for hydrogen production because of their simplicity. Although the simplicity is an advantage; reducing the energy consumption and maintaining the durability and the safety of these systems are the main challenges. In this paper, alkaline water electrolysis system, that uses cost effective electrode materials and magnetic field effects are presented. Cost effective electrodes such as high carbon steel, 304 stainless steel, 316L low carbon steel and graphite material are used for the hydrogen production. After the selection of the best electrode pair, effects of magnetic field to hydrogen production and change of current density are investigated for KOH electrolytes in different concentrations (5 wt%, 10 wt% and 15 wt%). According to the experimental observations the direction of the Lorentz Force affects the hydrogen production and current density. When the Lorentz Force is directed upward, it enhances the hydrogen production for 5 wt% and 15 wt% KOH solution by almost 17%. The increase in current density for 5 wt%, 10 wt% and 15 wt% concentration is 19%, 5%, 13%, respectively. Forced convection in the magnetic field enhances the separation of gas bubbles from electrode surface. Downward directed Lorentz Force decreases hydrogen production and current density values significantly. For 5 wt%, 10 wt% and 15 wt% the hydrogen production decreases by 14%, 8%, 7%, respectively. Similarly, current density for downward directed Lorentz Force decreases by 11%, 7%, 4%, respectively. In order to realize future hydrogen society, hydrogen production systems must meet the large demand of hydrogen usage. Alkaline water electrolysis (AWE) would be one of the candidate technologies to produce hydrogen on a large scale from renewable energy. We have conducted basic research into AWE, trying to reveal technical issues under zero gap system in new cell technology. The zero gap system contributes lower cell voltage without causing any major operating problems compared with conventional finite gap cell. However, it was observed that Ni base electrodes showed corrosion phenomena in a number of test trials including steady operating conditions and several shut-downs. Activated Raney Ni alloy coating for anode material had an advantage for oxygen overvoltage. It showed a saving of around 100 mV at 40 A/dm2 (0.4 A/cm2) against Ni bare anodes. In the Chlor–Alkali (C/A) industry, thermal decomposition coating of mixed noble metal on Ni substrate is commonly used for advanced activated cathodes. It showed very low hydrogen over-potential of around 100 mV in AWE. To achieve better cell performance, separator selection is very important. We evaluated several separators including ion exchange membrane (IEM) to understand the basic function in AWE. IEM for C/A electrolysis showed high cell voltage (over 2.2 V) but low O2 impurity in H2 gas. Hydrogen purity was over 99.95%. Porous separators made of polypropylene showed 1.76 V at 40 A/dm2 (0.4 A/cm2), 80 °C. But there was a weakness on the durability for continuous operation. Proper selection of separator is important in an actual plant for effective and safe cell operation. The concept of safety operation is referred to by diffusion coefficient of hydrogen.So-called perovskite solar cells (PSC) are composed of PbI6 4- (MeNH3 +)4 salt, where PbI6 4- plays an essential role as an effective solar light sensitizer with keeping semiconducting property even when aligned each other. Density-functional-theory-based molecular modeling (DFT/MM) using reported X-ray crystallographic structure of PbI6 4-/MeNH3 +/H2 O salt (named FOLLIB in Cambridge Structural Data) validates that the packing unit consisting of {(PbI6 4-)9 [(MeNH3 +)2 -H2 O]2 (MeNH3 +-H2 O)2 (MeNH3 +)2 }28- should show UV/Vis absorption spectrum at λmax=424 nm (pale yellow color) as observed for the PbI64- crystal. DFT/MM of the FOLLIB horizontal aligned component, [(PbI6 4-[(MeNH3 +)2 -H2 O]2 (MeNH3 +-H2 O)2 (MeNH3 +)2 /(PbI6 4-)2 )4- verifies that the component has narrow energy gap of 0.3 eV, predicting excellent semiconducting property of the PbI64- alignment with MeNH3 +. Three H2 O-free PbI6 4-/MeNH3 + aligned components, PbI6 4-(MeNH3 +)4 , [PbI6 4-(CH3 NH3 +)3 ]- and [PbI6 4-(CH3 NH3 +)2 ]2- are molecular modeled and verified to have UV/Vis spectra at λmax=570 nm, λmax=762 nm, and λmax=945 nm, respectively. Mixtures of them will be colored black, which is consistent with observable black coloration of PbI64- alignments with MeNH3+ in amorphous solute state. It is further verified that PbI6 4- undergoes van der Waals and Coulomb interactions both with electron accepting layers, i.e., nc-TiO2 in PSC of nc-TiO2/MeNH3PbI3/spiro-OMeTAD and with electron donating layer, i.e., spiro-OMeTAD in the PSC. The molecular orbital structure and electrostatic potential map verifies formation of tight interaction between them. The electron density-based alignment PbI6 4- validates unidirectional electron transport at both interfaces, resulting in high open-circuited voltage (Voc) of ~1.0 eV in PSC. In addition, the semi-conducting sensitizing layer of PbI6 4-/MeNH3 + components validates excellent short-circuited photocurrent (Jsc), and respectable fill factor of PSC. The PbI6 4--aligned solar cell will be regarded as a kind of quantum dot solar cell. Effective sensitizing components in so-called perovskite solar cells (PSC) are lead hexaiodide (PbI64−) salts of PbI64− (MeNH3+)n (n = 2∼4). Density-functional-theory-based molecular modeling (DFT/MM) of X-ray crystalline structure of PbI64−/MeNH3+ salt (FOLLIB) verifies that the packing unit of FOLLIB has UV/Vis absorption spectrum at λmax = 424 nm, giving pale yellow color as complementary color. DFT/MM of the horizontal component in the FOLLIB gives narrow energy gap of 0.3 eV, verifying remarkable semiconducting property through tight alignments of PbI64− components coupled with MeNH3+. DFT/MM of the central PbI64−/MeNH3+ components verifies that the central component has UV/Vis absorption spectra with respective λmax = 570 nm, λmax = 762 nm and λmax = 945 nm, and plays an essential role as panchromatic sensitizers. In addition, their equilibrium geometric structures show slightly hypsochromic UV/Vis absorption spectra at respective λmax = 486 nm, λmax = 560 nm, and λmax = 563 nm as results of migration of MeNH3+ close to PbI64−. DFT/MM also verifies that PbI64− components align tightly to nanocrystalline TiO2 (nc-TiO2) and to spiro-OMeTAD in PSC through electron density induced by van der Waals interaction. Electron density-based alignments of PbI64− components well explain unidirectional and leakage-free electron diffusion leading to high open-circuit voltage in PbI64−-aligned solar cells. At the same time, the semiconducting and panchromatic sensitizing layer of PbI64−/MeNH3+ components contribute to excellent short-circuit photocurrent of PbI64−-aligned solar cells. Effective sensitizing components in so-called perovskite solar cells (PSC) are lead hexaiodide (PbI64−) salts of PbI64− (MeNH3+)n (n = 2~4). Density-functional-theory-based molecular modeling (DFT/MM) of X-ray crystalline structure of PbI64−/MeNH3+ salt (FOLLIB) verifies that the packing unit of FOLLIB has UV/Vis absorption spectrum at λmax = 424 nm, giving pale yellow color as complementary color. DFT/MM of the horizontal component in the FOLLIB gives narrow energy gap of 0.3 eV, verifying remarkable semiconducting property through tight alignments of PbI64− components coupled with MeNH3+. DFT/MM of the central PbI64−/MeNH3+ components verifies that the central component has UV/Vis absorption spectra with respective λmax = 570 nm, λmax = 762 nm and λmax = 945 nm, and plays an essential role as panchromatic sensitizers. In addition, their equilibrium geometric structures show slightly hypsochromic UV/Vis absorption spectra at respective λmax = 486 nm, λmax = 560 nm, and λmax = 563 nm as results of migration of MeNH3+ close to PbI64−. DFT/MM also verifies that PbI64− components align tightly to nanocrystalline TiO2 (nc-TiO2) and to spiro-OMeTAD in PSC through electron density induced by van der Waals interaction. Electron density-based alignments of PbI64− components well explain unidirectional and leakage-free electron diffusion leading to high open-circuit voltage in PbI64−-aligned solar cells. At the same time, the semiconducting and panchromatic sensitizing layer of PbI64−/MeNH3+ components contribute to excellent short-circuit photocurrent of PbI64−-aligned solar cells.