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

Abstract

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.