(Invited) Safe Design of GS Yuasa Large Format Lithium Ion Cells for Industrial Applications

Abstract

Since the 1990’s, GS Yuasa has developed and produced large-format Li ion cells for a variety of applications including satellites, rockets, electrified vehicles, trains, AGVs, energy storage systems, UPS, submarines, and others. Through these activities, safer Lithium-ion cell designs have evolved not only through the careful selection of electrode chemistry, but also cell shape, case materials and cell orientation within the module or battery pack. Lithium iron phosphate, for example, is stable and often considered a “safe” material for use in the positive electrodes of lithium-ion cells; however, there have been many lithium iron phosphate cell fires in the field. Fires may be caused by leakage of a flammable electrolyte in proximity to an ignition source. GS Yuasa considers the combination of using a metal cell case with laser-welded seal and a terminals-up orientation of cells in the module or battery pack to drastically decrease the risk of electrolyte leakage. Figure 1 shows the typical cell design of our large lithium ion cells for electrified vehicles and other industrial applications such as trains, AGVs, energy storage systems and UPS. The metal case with laser-welded seal offers high reliability with respect to the prevention of electrolyte leakage. This approach to cell design and orientation locates the more sensitive potential leak paths such as the rupture disk, terminal seal and case welds in the top of the cell and away from free electrolyte. In this presentation, we will detail GS Yuasa’s cell and battery systems and discuss our field experiences. Figure 1