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.