Physical-Chemical Characterization of Cycle Aged Commercial Cells of Automotive Interest 2022-01-0276
Nowadays, the reduction of greenhouse gases and air pollutants, largely produced by vehicles with internal combustion engines, is of primary importance. The usage of energy storage systems could represent a smart opportunity for cleaner transportation. Lithium ion batteries have emerged as the most suitable technology available on the market to reach this challenging goal. To make Li-ion battery technologies a competitive solution for the automotive industry, costs, performances and safety must be improved. A deep understanding of Li-ion battery materials and their response under real-use conditions is crucial to achieve these targets. From a full characterization of the electrochemical performances, it is possible to specifically design the charge and discharge conditions for maximizing the battery performances while optimizing its life. In this study the thorough characterization of commercial 18650 cells is carried out over their full life. First, the fresh cells have been characterized in their capacity and internal resistance. To gain understanding of the chemistry and material composition the cells have been torn down. The characterization of the electrodes, separator and electrolyte, applying techniques such as SEM, XRF, XRD, GC and IC, provides a complete description of the physical-chemical behavior.
In order to simulate real driving conditions, a set of 5 cells has been aged in such a way as to reproduce the stress the battery pack will experience during its life. The experiments were performed by means of WTLC (Worldwide Harmonized Light Vehicles Test Cycle)-based power profiles and also by applying DCFCs, in order to trigger aging phenomena inside the Li-ion cell module. At the end of life the teardown of the aged cells was exploited for the detection of aging effects on electrodes, electrolytes and other components. This allows one to gain a deep understanding of the degradation phenomena occurring during the cell life at laboratory scale and in the vehicle.
Citation: Dotoli, M., Rocca, R., Giuliano, M., Sgroi, M. et al., "Physical-Chemical Characterization of Cycle Aged Commercial Cells of Automotive Interest," SAE Technical Paper 2022-01-0276, 2022, https://doi.org/10.4271/2022-01-0276. Download Citation