Cycle life performance of lithium-ion pouch cells

Cycle life studies have been done on lithium-ion pouch cell with LiCoO2 as cathode and meso-carbon micro-beads (MCMB) as anode at five different temperatures. By using the rate capability tests done at the same temperature as that of cycling and the half cell studies done on the fresh and cycled individual electrodes, the stoichiometric windows of individual electrodes at the beginning and at the end of cycling have been estimated. By analyzing these estimates along with the X-ray diffraction studies and half cell studies on cycled cathodes, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and half cell studies on cycled anodes, possible causes of increased capacity fade with increasing temperature were found to be the anode active material loss, probably due to a solvent/salt reduction reaction on the anode. Lithium deposition on the anode also has been identified as a possible side reaction during later stages of cycling at 35 and 45 °C.