Cycle life characterisation of large format lithium-ion cells

To predict the remaining useful life (RUL), commercially available lithium-ion cells of 63 Ah with nickel manganese cobalt oxide (NMC) cathode material underwent cycle life ageing tests at different current rates (C) and temperature. The key performance parameters such cell capacity, discharge capability and impedance were measured for fresh and aged cells to evaluate the RUL of the cells. The results of ageing tests showed, cell capacity was not influenced by impedance increase slightly regardless of the cycling conditions, rather power fade significant in determining the RUL of the cells. Detailed study of impedance characteristics revealed series resistance (R_ser) and solid electrolyte interface resistance (R_sei) as main contributors to power fade.