Ladder-type phenazine-linked covalent organic polymers with synergistic cation–π interactions for highly stable lithium metal batteries

Abstract

The construction of an efficient regulating film for lithium metal anodes, capable of addressing both dendritic growth and by-product reactions, is pivotal to the stability of lithium metal batteries. Herein, a ladder-type phenazine-linked covalent organic polymer (PZ-CHPT) with a fully extended two-dimensional aromatic π-conjugated system, enriched with nitrogen sites (C–CN–C linkages, CN units), is introduced as a lithium metal anode protective layer to control spatial ion flux and induce uniform charge distribution, aiming at enhancing the reliability of lithium metal batteries. Remarkably, the incorporation of rigid heterocyclic units into PZ-CHPT boosts interfacial stability through reinforced covalent linkage strength and reduces Li⁺ diffusion energy consumption, while the concurrent cation–π interactions between Li⁺ and electron-rich aromatic motifs dynamically polarize the π-electron distribution, ultimately establishing continuous ion-transfer pathways through electrostatic-guided hopping along the conjugated framework, as validated by multimodal characterization techniques. Leveraging these synergistic properties, the PZ-CHPT-based full cells retain an exceptional 86.1% capacity after 1800 cycles at 3C, showing a minimal cycle-to-cycle degradation of ∼0.008%. This work establishes a foundation for the molecular design and mechanism exploration of organic polymers with double-stranded ladder skeletons, which can be used to construct highly stable lithium metal batteries.