The strategy of N-doping in carbon materials could provide additional Li-ion storage sites to improve their electrochemical properties. Heteroatom-containing polymers could serve as good precursors to fabricate doped carbons due to the capability to in situ dope heteroatoms into the structures. In this work, electrospun heterocyclic polyimide (PI) nanofiber membranes containing biphenyl and pyrimidine rings were carbonized to fabricate freestanding and flexible heteroatoms-containing carbon membranes. When the polymer membranes were subjected to various calcination temperatures (from 550 degrees C to 950 degrees C) and durations (0.5-10 h), the structural evolutions strongly affect their electrochemical properties as anodes for lithium ion batteries. It demonstrated that the reversible specific capacity of obtained sample treated at 650 degrees C for 3 h could achieve 695 mAh/g at 0.1 A/g and retain 245 mAh/g at 1.5 A/g after 300 cycles. Furthermore, the electrospun membrane maintains a good electrochemical performance at bending state as a flexible electrode. (C) 2018 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.