Immobilizing Quinone‐Fused Aza‐Phenazine into π‐d Conjugated Coordination Polymers with Multiple‐Active Sites for Sodium‐Ion Batteries

Abstract

AbstractThe development of coordination polymers with π‐d conjugation (CCPs) provides ide prospects for exploring the next generation of environmental‐friendliness energy storage systems. Herein, the synthesis, experimental characterizations, and Na‐ion storage mechanism of π‐d CCPs with multiple‐active sites are reported, which use quinone‐fused aza‐phenazine (AP) and aza‐phenazin (AP) as the organic ligands coordinated with the metal center (Ni2+). Among them, NiQAP as the cathode material exhibits impressive electrochemical properties applied in sodium‐ion batteries (SIBs), including the high initial/stable discharge specific capacities (180.0/225.6 mAh g−1) at 0.05 A g−1, a long‐term cycle stability up to 10,000 cycles at 1.0 A g−1 with a high reversible capacity of 100.1 mAh g−1, and good rate capability of 99.6 mAh g−1 even at 5.0 A g−1. Moreover, the Na‐ion storage mechanism of NiQAP is also performed by the density functional theory (DFT) calculation, showing multiple‐active sites of C≐O and C≐N (in the quinone and phenazine structure) and NiO4 (in the coordination unit) for Na‐ion storage. These results highlight the importance of organic electrode material with the coordination units and provide a foundation for further studying the CCPs with multiple active sites for energy storage systems.