Regulating Zn2+ Migration-Diffusion Behavior by Spontaneous Cascade Optimization Strategy for Long-Life and Low N/P Ratio Zinc Ion Batteries.

Abstract

Parasitic side reactions and dendrite growth on zinc anodes are formidable issues causing limited lifetime of aqueous zinc ion batteries (ZIBs). Herein, a spontaneous cascade optimization strategy is first proposed to regulate Zn²⁺ migration-diffusion behavior. Specifically, PAPE@Zn layer with separation-reconstruction properties is constructed in situ on Zn anode. In this layer, well-soluble poly(ethylene oxide) (PEO) can spontaneously separation to bulk electrolyte and weaken the preferential coordination between H₂O and Zn²⁺ to achieve primary optimization. Meanwhile, poor-soluble polymerized-4-acryloylmorpholine (PACMO) is reconstructed on Zn anode as hydrophobic flower-like arrays with abundant zincophilic sites, further guiding the de-solvation and homogeneous diffusion of Zn²⁺ to achieve the secondary optimization. Cascade optimization effectively regulates Zn²⁺ migration-diffusion behavior, dendrite growth and side reactions of Zn anode are negligible, and the stability is significantly improved. Consequently, symmetrical cells exhibit stability over 4000 h (1 mA cm^-2). PAPE@Zn//NH₄ ⁺-V₂O₅ full cells with a high current density of 15 A g^-1 maintains 72.2 % capacity retention for 12000 cycles. Even better, the full cell demonstrates excellent performance of cumulative capacity of 2.33 Ah cm^-2 at ultra-low negative/positive (N/P) ratio of 0.6 and a high mass-loading (~17 mg cm^-2). The spontaneous cascade optimization strategy provides novel path to achieve high-performance and practical ZIBs.