Surface Characterization of Electrodes from High Power Lithium-Ion Batteries

X-ray photoelectron spectroscopy and scanning electron microscopy were used to study electrode samples obtained from 18650-type lithium-ion cells subjected to accelerated calendar-life testing at temperatures ranging from 25 to 70°C and at states-of-charge from 40 to 80%. The cells contained -based positive electrodes (cathodes), graphite-based negative electrodes (anodes), and a 1 M ethylene carbonate:diethyl carbonate (1:1) electrolyte. The results from electrochemically treated samples showed surface film formation on both electrodes. The positive electrode laminate surfaces contained a mixture of organic species that included polycarbonates, and LiF, -type and -type compounds. The same surface compounds…