Theory and Practice of Lithium Ion Cell Design

Abstract

First commercialized lithium ion cell was used for camcorder by Sony in 1991. After that, applications have been wider continuously, but energy and power density of cell have to be improved simultaneously for widening to various industrial fields even now. Though continuous research and development efforts have been made to get novel material, most of the commercial cells are producing with the material which had been developed long ago.1 Lithium ion cell have four major material components such as cathode, anode, separator and solvent electrolyte. Among them, it is really true that active materials are basic construction blocks for building an excellent cell. Active material would be used to produce cell above 1M/month on the commercial production scale and absolutely have to be converted to electrodes for using commercial cell. Electrode is absolutely the unit device for realizing the intrinsic properties of material itself. The performance of electrode would be come out from intrinsic material properties itself such as specific capacity[mAh/g] and redox potential[volt]. Also, it is important to maximize reversible cell capacity and discharge voltage through balanced design between cathode and anode with safety tolerance using specific capacity and redox potential. Lithium ion cell does not stay on the equilibrium state under usage. Charges carriers are always moving from one electrode to another through solvent electrolyte solution in the cell. So, overpotential(volt) under current flowing conditions would always affect to cell performances. Kinetic characteristics of charges, which are related to mesoporous electrode structures made by manufacturing process., should be considered to get high energy density[Wh/kg]] and power density[W/kg]2. In this presentation, we would like to think the way to develop novel material through reviewing the relationship among material property, electrode characteristics and practical lithium ion cell design.