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 1422.6mAhg−1 at the current rate of 0.2C with the high sulfur content of 76wt.%, and a much higher energy density of 754Whkg−1 and power density of 1901Whkg−1, which greatly improve the energy/power density of traditional lithium–sulfur batteries and will be promising for further commercial applications.