Graphene/polyaniline composite electrodes have attracted much attention owing to their potential applications in supercapacitors or ultracapacitors. Currently, it remains a great challenging task to a trade-off between the specific capacitance and rate performance. Herein, we demonstrate an alternative and effective route to prepare 3D multi-growth site graphene (MSG)/polyaniline (PANI) composite electrode with highly improved electrochemical properties. Multi-growth site graphene is prepared by introducing in-plane carbon vacancy defects and more oxygen functional groups into graphene sheets via a mild acid oxidation (70% HNO3/30% H2O2) chemical treatment. The in-situ prepared MSG/PANI nanocomposites exhibit a collection of unique properties with highly improved specific capacitance of 912 F/g at 1 A/g much higher than those without HNO3/H2O2 treatment (432 F/g), excellent rate capability of 86.4% retention at high current density of 20 A/g, high cycling stability of 89.5% of its initial capacitance after 10000 charge/discharge cycles at 10 A/g, and good mechanical property, which are the optimized overall performances among supercapacitor electrodes based on graphene/polyaniline composites in the literature. These results suggest that the MSG/PANI composite electrodes with excellent electrochemical properties are particularly attractive for supercapacitor applications. (c) 2017 Elsevier Ltd. All rights reserved.