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

Abstract

Graphitic carbon nitride (g–C3N4) is widely used in organic metal‐ion batteries owing to its high porosity, facile synthesis, stability, and high‐rate performance. However, pristine g–C3N4 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–C3N4 composite anode materials, CN–PIx (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–PI1 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 (Esp) of ∼7700 Wh kg−1 and the volumetric energy density (Ev) 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–PIx electrodes contributes to their superior electrochemical performance, resulting from the fact that the Li+ is not only stored in the CN–PIx composites but also CN–PIx activated the Li0 adlayer on the CN–PI1–Cu heterojunction as an SEI layer to avoid the direct contact of Li0 phase and the electrolyte. The CN–PI1 full cell with LiCoO2 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–C3N4‐based anode materials for realizing long‐lasting energy storage devices.