Polymer Coating with Balanced Coordination Strength and Ion Conductivity for Dendrite-Free Zinc Anode

Decorating Zn anodes with functionalized polymers is considered as an effective strategy to inhibit dendrite growth. However, this normally brings extra interfacial resistance rendering slow reaction kinetics of Zn2+. Herein, a poly(2-vinylpyridine) (P2VP) coating with modulated coordination strength and ion conductivity for dendrite-free Zn anode is reported. The P2VP coating favors a high electrolyte wettability and rapid Zn2+ migration speed (Zn2+ transfer number, tZn2+ = 0.58). Electrostatic potential calculation shows that P2VP mildly coordinates with Zn2+ (adsorption energy = -0.94 eV), which promotes a preferential deposition of Zn along the (002) crystal plane. Notably, the use of partially (26%) quaternized P2VP (q-P2VP) further reduces the interfacial resistance to 126 omega, leading to a high ion migration speed (tZn2+ = 0.78) and a considerably low nucleation overpotential (18 mV). As a result of the synergistic effect of mild coordination and partial electrolysis, the overpotential of the q-P2VP-decorated Zn anode retains at a considerably low level (approximate to 46 mV) over 1000 h at a high current density of 10 mA cm-2. The assembled (NH4)2V6O16 center dot 1.5H2O || glass fiber || q-P2VP-Zn full cell reveals a lower average capacity decay rate of only 0.018% per cycle within 500 cycles at 1 A g-1. Poly(2-vinylpyridine) (P2VP) limits the unrestricted 2D diffusion of zinc ions through soft coordination and the partially quaternized derivative (q-P2VP) further enables a balance between coordination trapping and ion transporting, leading to a rapid ion migration speed and a lower capacity decay.image