Monday, 20 June 2016
Riverside Center (Hyatt Regency)
Rechargeable Li-ion secondary batteries are being developed for use in high power applications, such as fully electric vehicles and hybrid electric vehicles, because of their high energy density and high power density compared to other battery technologies. Future application of multilayer lithium ion secondary batteries requires a thorough understanding of the influence of microstructure on battery performance. In particular, cathode-substrate and cathode-electrolyte interfaces are known to affect charge/discharge rates, cyclability and battery lifetime. In this study, oriented LiMn2O4 and LiCoPO4 cathodic thin films were successfully fabricated on Au/Al2O3 substrates from precursor solutions. The films were analyzed by X-ray diffraction and Cs-corrected scanning transmission electron microscopy (STEM) using high-angle annular dark-field (HAADF) and annular bright-field (ABF) detectors. It was found that the film/substrate lattice misfit affects the degree of epitaxy of the thin films. Direct observation of atom columns showed that epitaxial LiMn2O4 film forms an atomically flat and coherent heterointerface with the substrate, but that the crystal lattice is distorted with a compositional gradient in the film near the interface. Using ABF-STEM, Li-ion columns in the LiCoPO4 cathode film could be viewed directly and antisite defects were identified in the surface regions.
References
[1]Y. H. Ikuhara, et al., J. Phys. Chem. C, 118 (2014) 19540.
[2]X. Gao, et al., Adv. Mater. Interfaces, 1(2014) 1400143.