Three-dimensional (3D) flexible electrodes of stringed hollow nitrogen-doped (N-doped) carbon nanospheres as graded sulfur reservoirs and conductive frameworks were elaborately designed via a combination of the advantages of hollow structures, 3D electrodes and flexible devices. The as-prepared electrodes by a synergistic method of electrospinning, template sacrificing and activation for Li-S batteries without any binder or conductive additives but a 3D interconnected conductive network offered multiple transport paths for electrons and improved sulfur utilization and facilitated an easy access to Li+ ingress/egress. With the increase of density of hollow carbon spheres in the strings, the self-supporting composite electrode reveals an enhanced synergistic mechanism for sulfur confinement and displays a better cycling stability and rate performance. It delivers a high initial specific capacity of 1422.6 mAh g(-1) at the current rate of 0.2C with the high sulfur content of 76 wt.%, and a much higher energy density of 754Wh kg(-1) and power density of 1901 Wh kg(-1), which greatly improve the energy/power density of traditional lithium-sulfur batteries and will be promising for further commercial applications. (C) 2017 Elsevier B.V. All rights reserved.