Electrode structure analysis and surface characterization for lithium-ion cells simulated low-Earth-orbit satellite operation: II: Electrode surface characterization

As a sequence work to investigate the performance-degradation mechanism of an aged commercial laminated lithium-ion cell experiencing 4350-cycle charge–discharge in a simulated low-Earth-orbit (LEO) satellite operation, we performed the surface characterization of LiCoO2 cathode and graphite anode by Fourier transform infrared-Attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analysis in this work. Overall, the graphite anode had a larger change in surface chemistry than that of the LiCoO2 cathode. Except the common surface components, we detected Co metal at the aged graphite surface in the first time. This Co metal deposition was believed to originate from Co2+ dissolution from LiCoO2 cathode during prolonged cycling, and detrimental to structure stability of LiCoO2 cathode which was a main cause of cell capacity loss. The amount of surface-film component was also estimated by FTIR analysis. Though the total amount of surface film increased, the organic (inorganic) surface film decreased (increased) with prolonged cycling.