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

We report a novel electrode for Li-O-2 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(-1) C). 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 Xray 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 timeelapsed discharge also supported a continuous carbonate formation. By limiting the discharge capacity to 500 mA h.g(-1) C, an improvement in the cycling was observed, however, the higher overpotential needed to decompose the discharge product limited the cell performance.