Conjugated multi-ring polymers with heteroatoms (N, S or O etc.) are promising anode materials for lithium ion batteries (LIBs) owning to resource sustainability, molecular diversity and high electronic conductivity. Among these, cyclized polyacrylonitrile (cPAN) is investigated as a novel lithium storage anode in this work. Theoretical calculations and electrochemical characterizations demonstrate that the conjugated N and C atoms in the heterocyclic polymers can both act as the redox sites for Li+ uptake/release, thus giving an ultra-high theoretical capacity. Benefiting from the multiple redox centers and highly conjugated structure, cPAN nanofibers demonstrate super-high reversible capacity (1375 mA h g(-1) at 0.05 A g(-1)), excellent rate capability (383 mA h g(-1) at 10 A g(-1)) and remarkable long cycling life over 10,000 cycles. This work may shed light on the development of sustainable and versatile organics as lithium-storage electrodes.