Tailoring of CNT surface oxygen groups by gas-phase oxidation and its implications for lithium ion batteries

Multi-walled CNT were oxidised with nitric acid in liquid and gas-phase. By splitting the capacity and initial charge loss during lithium intercalation into different potential regions, it was possible to relate these values to the CNT surface oxygen groups as determined by XPS. Gas-phase oxidised CNT show a significantly lower amount of initial charge loss (172 mAh/g) compared to liquid-phase oxidised CNT (283 mAh/g). This decrease originates from less pronounced exfoliation likely caused by an increase of surface carbonyl groups.

► Multi-walled CNT exhibit high initial charge losses when used as lithium ion battery anodes. ► Charge loss reactions vary depending on the reduction potential. ► Gas-phase oxidation using nitric acid changes surface oxygen chemistry. ► Carbonyl surface groups prevent exfoliation better than single-bonded oxygen.