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

Polymer interphase on Zn anodes obviates dendrite growth and significant side reactions including corrosion and hydrogen evolution in aqueous zinc ion batteries (AZIBs), however has drawbacks of slow kinetics and large overpotential for Zn plating/stripping that prevent practical application especially under high-rate conditions. Here, a multifunctional polymer interphase with fast kineticsis 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 adsorbs on the Zn anode to form a stable solid-electrolyte interphase (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. It is concluded that judicious engineering of polymer additives and interphase will benefit the development of commercial AZIBs with fast kinetics for high-rate applications.