Extraordinary Ultrahigh‐Capacity and Long Cycle Life Lithium‐Ion Batteries Enabled by Graphitic Carbon Nitride‐Perylene Polyimide Composites

Graphitic carbon nitride (g–C 3 N 4 ) is widely used in organic metal‐ion batteries owing to its high porosity, facile synthesis, stability, and high‐rate performance. However, pristine g–C 3 N 4 nanosheets exhibit poor electrical conductivity, irreversible metal‐ion storage capacity, and short‐term cycling owing to their high concentration of graphitic–N species. Herein, a series of 3,4:9,10‐perylenetetracarboxylic diimide‐coupled g–C 3 N 4 composite anode materials, CN–PI x ( x = 0.2, 0.5, 0.75, and 1), was investigated, which exhibited an unusually high surface nitrogen content (23.19–39.92 at.%) and the highest pyridinic–N, pyrrolic–N, and graphitic–N contents reported to date. The CN–PI 1 anode delivers an unprecedented and continuously increasing ultrahigh discharging capacity of exceeding 8400 mAh g −1 (1.96 mWh cm −2 ) at 100 mA g −1 with high specific energy density ( E sp ) of ∼7700 Wh kg −1 and the volumetric energy density ( E v ) of ∼14956 Wh L −1 and an excellent long‐term stability (414 mAh g −1 or 0.579 mWh cm −2 at 1 A g −1 ). Furthermore, the activation of the CN–PI x electrodes contributes to their superior electrochemical performance, resulting from the fact that the Li + is not only stored in the CN–PI x composites but also CN–PI x activated the Li 0 adlayer on the CN–PI 1 –Cu heterojunction as an SEI layer to avoid the direct contact of Li 0 phase and the electrolyte. The CN–PI 1 full cell with LiCoO 2 as the cathode delivers a discharge capacity of ∼587 mAh g −1 at a 1 A g −1 after 250 cycles with a Coulombic efficiency nearly 99%. This study provides a strategy to develop N‐doped g–C 3 N 4 ‐based anode materials for realizing long‐lasting energy storage devices.