Radially ordered carbon nanotubes performance for Li-O2 batteries: Pre-treatment influence on capacity and discharge products

Abstract We report a novel electrode for Li-O2 battery based on radially ordered multi-walled carbon nanotubes functionalized by acid and plasma pre-treatments without degrading its structure with improved wettability leading to more effective active sites. This electrode was used in a device with DMSO/LiClO4 as the electrolyte, presenting good discharge capacity result (2804 mA h g−1C). The defects on the nanotube structure were characterized with RAMAN and a correlation from defects and discharge capacity was observed indicating that the defects could provide larger number of effective regions for discharge products. Raman, FTIR and synchrotron X-ray diffraction characterization over the discharged electrode revealed a large formation of Li2CO3 as the main product, which is uncommon for this system. Further characterization of composition and morphology in time-elapsed discharge also supported a continuous carbonate formation. By limiting the discharge capacity to 500 mA h.g−1C, an improvement in the cycling was observed, however, the higher overpotential needed to decompose the discharge product limited the cell performance.