Shinji Inazawa

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.

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 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.