Masatoshi Majima

Development of long life lithium ion battery for power storage

Abstract With the aim of developing lithium ion batteries with a long life and high efficiency for power storage, we experimentally evaluated combinations of cathode and anode active materials, in which batteries are able to obtain over 4000 cycles or 10 years of life. An acceleration method was evaluated using coin cells. We found that changing the current density was effective for evaluating battery life, since the logarithm of the cycle life showed a linear relationship to current density. Based on the current density increasing method, various combinations of cathode and anode active materials were tested. The cell system of LiCoO2/Li4/3Ti5/3O4 clearly showed a long life of about 4000 cycles. The energy density of the cell using the Li4/3Ti5/3O4 anode is obviously smaller than that using a graphite anode, the cell with Li4/3Ti5/3O4 anode was thought to have some merit especially in the large-scale-layer-built type battery by the applicability of the Al anode collector and a light weight battery case.

Correlation between electroconductive and structural properties of proton conductive acceptor-doped barium zirconate

Various dopants were added to BaZrO3 and the conductivities, the proton concentrations, the site occupancy of the dopants and the change in lattice volume as a result of chemical expansion were investigated. Lanthanide group dopants occupied both the Ba and Zr sites, but the amount of these dopants in the Ba site was too limited to significantly influence the conductivity. The samples doped with Yb, Tm, Er, Y and Ho showed both high proton concentrations and high conductivities, together with a relatively large lattice expansion as a result of hydration. We therefore suggest that, in most instances, the proton concentration, proton conductivity and lattice change as a result of chemical expansion were all correlated in proton conductive acceptor-doped BaZrO3. However, Sc-doped BaZrO3 seemed to be different. Its proton concentration was high, but the conductivity and lattice change as a result of chemical expansion were relatively small. This indicates that the conductivity was strongly related to the lattice expansion resulting from hydration rather than simply the proton concentration.

Origins of structural and electrochemical influence on Y-doped BaZrO3 heat-treated with NiO additive

Nickel (Ni) is expected to be an attractive anode material for protonic ceramic fuel cells using Y-doped BaZrO3 (BZY) as an electrolyte, since Ni shows good catalytic properties for the anode reaction, and NiO is a sintering aid for BZY. In this work, a systematic investigation has been performed to reveal the influence of Ni incorporation on structural and electrochemical properties of BZY. Then, some new knowledge was obtained; the important point is that Ni cations occupy the interstitial position of (1/2, 0, 0) in the lattice of BZY, with a greatly Ba-deficient environment. As a result, Ba cations were possibly driven to the grain boundary and induced the formation of a liquid phase, which promoted the sintering process. However, the occupation of Ni on this (1/2, 0, 0) position also resulted in a negative influence on conductivity. A careful processing is required to apply Ni as the electrode in BZY based fuel cells.

Design and characteristics of large-scale lithium ion battery

Adequate cell design, especially concerning energy density and cycle life, is important for the development of large-scale lithium ion batteries. In this study, we were able to survey the expansion and shrinkage of the layer-built electrodes of a prismatic cell during charge and discharge tests. Natural graphite and mesophase carbon micro beads (MCMB) were used as anode active material for the comparison purpose. Based on the findings of this study, a plate spring and lightweight battery case were designed. In addition, an improved large-scale battery employing these parts was manufactured for further examination.

Development of 1 kWh (300 Ah) class lithium-ion battery

Abstract A large-capacity lithium-ion battery of 1 kWh (300 Ah) class was fabricated by using LiCoO 2 and natural graphite as the cathode and anode materials, respectively, and LiPF 6 as the electrolyte to develop industrially usable batteries for energy source. Our battery delivered an energy density of 60 Wh/kg (133 Wh/l) with weight and volume of a container included with a cycle life of 245 cycles, which was longer compared with that of our former battery using LiBF 4 as the electrolyte [5,6]. These improvements were achieved by changing the following factors: (i) use of LiPF 6 as the electrolyte; (ii) optimizing the mixing ratio of the solvent (EC/DEC); (iii) employing a plate spring for the buffer of electrode expansion and shrinkage; (iv) minimizing residual moisture.

A high temperature reduction cleaning (HTRC) process: a novel method for conductivity recovery of yttrium-doped barium zirconate electrolytes

Proton conducting Y-doped BaZrO3 (BZY) and nickel oxide (NiO) are currently the most promising electrolyte and anode catalyst for protonic ceramic fuel cells, respectively. However, during the co-sintering process to fabricate the fuel cells, Ni cations diffuse from the anode into the lattice of the BZY electrolyte, resulting in significant degradation of the electrolyte conductivity and fuel cell performance. With the aim to solve such a problem, in this work, we report a novel method, named as high temperature reduction cleaning (HTRC) process, which is composed of several sequential heat-treatments in controlled atmospheres. The most interesting point is that after heat-treating the NiO-contaminated BZY at 1400 °C in a Ti-deoxidized Ar atmosphere for 100 h, Ni cations were observed to be expulsed from the BZY lattice and segregated at the grain boundary as Ni metal particles. And the conductivity of the BZY electrolyte was recovered. However, delamination along the grain boundary of the BZY electrolyte was introduced when the segregated Ni metal particles were oxidized to NiO particles in an oxygen atmosphere. And a series of sequential heat-treatments were designed to solve such a problem.

Strategy to improve phase compatibility between proton conductive BaZr0.8Y0.2O3−δ and nickel oxide

BaZr0.8Y0.2O3−δ (BZY20) is a promising candidate as an electrolyte in protonic ceramic fuel cells (PCFCs), and nickel (Ni) is known to show good electrode properties for the anode reaction. However, their compatibility seems to be questionable, since during the co-sintering process for cell fabrication, a second phase of BaY2NiO5 formed due to a reaction between BZY20 and NiO. The results in this work revealed that BaY2NiO5 was unstable against high temperature (1500 and 1600 °C), and could also be reduced in a hydrogen atmosphere at 600 °C. The products of these reactions may affect fuel cell performance. A systematic work was then performed to provide fundamental insight into the reactivity between BZY20 and NiO, which was found to be impacted significantly by the compositional homogeneity of the BZY20 powder used for cell fabrication, and also the BaO activity during the co-sintering process. It is concluded that improving the compositional homogeneity of BZY20, by elevating the final heating temperature for BZY20 from 1300 to 1600 °C in this work, and choosing a proper sintering strategy may improve effectively the phase purity of the cell.

Electroless pure nickel plating process with continuous electrolytic regeneration system

Abstract We have developed an electroless nickel plating solution in which titanium ion redox system, Ti 3+ →Ti 4+ +e − , was used as a reducing agent. The stability of the solution has been improved by the selection of chelating agents and their ratio to nickel and titanium ion, and by the addition of an amino acid and a sulfur-containing compound. A pure nickel film containing no phosphorus was obtained from the new electroless plating solution. Any other elements except nickel were not detected by inductively coupled plasma analysis. Electrolytic regeneration system of the solution has been also developed. Continuous running test for more than 100 h has been achieved in a pilot plant and the bath is believed to be stable enough to apply to a commercial production line.

Development of 1 kW h class lithium ion battery for power storage

With the aim of developing 1 kW h class lithium ion batteries with long life and high efficiencies, we trial manufactured batteries that were fabricated using LiCoO2 and natural graphite as cathode and anode materials, respectively, with 1 M LiPF6 diluted by EC/DEC as an electrolyte. Fundamental studies necessary for the development of a large-scale battery consisting of laminated large electrodes were conducted, examining various factors. These factors were selected from the observations of batteries dismantled after the battery life reached an end point. The construction of the batteries was based on the results of fundamental research done to elucidate the problems encountered in the present study. We achieved 543 cycles with high efficiencies with the fourth battery. It is noteworthy that technical factors such as homogeneous impregnation of the electrolyte into the electrode laminates and maintenance of uniform conditions of laminates by the control of expansion and contraction accompanied with charge and discharge, respectively, were very important for the long life of large-scale lithium ion batteries. # 2001 Elsevier Science B.V. All rights reserved.

Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

Y-doped BaZrO3 (BZY) is currently the most promising proton-conductive ceramic-type electrolyte for application in electrochemical devices, including fuel cells and electrolyzer cells. However, owing to its refractory nature, sintering additives, such as NiO, CuO, or ZnO are commonly added to reduce its high sintering temperature from 1600 °C to approximately 1400 °C. Even without deliberately adding a sintering additive, the NiO anode substrate provides another source of the sintering additive; during the co-sintering process, NiO diffuses from the anode into the BZY electrolyte layer. In this work, a systematic study of the effect of NiO, CuO, and ZnO on the electroconductive properties of BaZr0.8 Y0.2 O3-δ (BZY20) is conducted. The results revealed that the addition of NiO, CuO, or ZnO into BZY20 not only degraded the electrical conductivity but also resulted in enhancement of the hole conduction. Removal of these sintering additives can be realized by post-annealing in hydrogen at a mild temperature of 700 °C, but it is kinetically very slow. Therefore, the addition of NiO, CuO, and ZnO is detrimental to the electroconductive properties of BZY20, and significantly restrict its application as an electrolyte. The development of new sintering additives, new anode catalysts, or new methods for preparing BZY electrolyte-based cells is urgently needed.