Multifunctional Polymer Interphase with Fast Kinetics for Ultrahigh‐rate Zn Metal Anode

Polymer interphase on Zn anodes obviates dendrite growth and side reactions, however has drawbacks of slow kinetics. Here, a multifunctional polymer interphase with fast kinectics is reported, using poly(phenazine‐alt‐pyromellitic anhydride) (PPPA) as an electrolyte additive. PPPA, with linear π‐conjugated structure and enriched polar pyridine (conjugated cyclic ‐C=N‐) and carbonyl (C=O) groups, preferentially absorbs on the Zn anode to form a stable solid‐electrolyte interpahse (SEI) layer in‐situ. The PPPA SEI is efficient to block direct contact between water molecules and Zn anode, and regulate the interfacial solvation structure and Zn depostion. Importantly, the expanding π‐conjugated structure of PPPA is shown to provide abundant 2D open channels for rapid Zn2+ transport, and the delocalized π electrons form a space electrostatic field to facilitate de‐solvation and diffusion of Zn2+. As a result, the Zn metal anode with PPPA/ZnSO4 electrolyte exhibits high Coulombic efficiency of 98.3% at current density of 20 mA cm−2, and excellent cycle lifespan for over 2000 cycles (400 h) at current density 50 mA cm−2 and plating/stripping capacity of 5 mAh cm−2. The Zn||MnO2 full battery exhibited a discharge capacity of 74.4 mAh g−1 after 5000 cycles at the current density of 2000 mA g−1, demonstrating practical feasibility.