Nitrogen, sulfur co-doped hierarchical carbon encapsulated in graphene with “sphere-in-layer” interconnection for high-performance supercapacitor

Lihua Cao, Huiling Li, Xiaolin Liu, Shuwu Liu, Lin Zhang, Wenhui Xu, Haoqi Yang, Haoqing Hou, Shuijian He, Yan Zhao, Shaohua Jiang