Characterization of Cycle-Life Aging in Automotive Lithium-Ion Pouch Cells

Lithium-ion battery electrodes utilizing mixtures of active materials have seen increased attention in recent years. These cells have merit for electric vehicle applications due to the potential for improved cycle life and increased performance. An aging campaign has been conducted with 15 Ah automotive pouch cells to quantify the relationship between a set of severity factors and the aging process for cells using composite electrodes, where aging is represented by capacity fade. A simplified electrochemical model which postulates that the materials within the composite electrode operate as parallel paths for current is used to interpret trends in the aging data. Using the model, loss of active material from individual components of the composite positive electrode can be simulated, as well as loss of cyclable lithium. Comparison with differential capacity data allows an assessment of the most likely degradation mechanism for the initial capacity fade.