Polyanion hydrogel electrolyte with a high Zn2+ transference number for dendrite-free aqueous zinc-ion batteries†

Abstract

Aqueous zinc-ion batteries have attracted great attention due to their advantages in energy storage. However, the existence of dendrites and a series of side reactions during the charge and discharge process hinder their further development. In this paper, a polyanionic hydrogel electrolyte (PMZA) based on 2-acrylamide-2-methylpropanesulfonic acid and polyvinyl alcohol (PVA) was designed and synthesized by free radical polymerization and the Hofmeister effect. It has excellent tensile properties (0.14 MPa). It also exhibits an excellent ionic conductivity of 71.17 mS cm⁻¹ and an ultra-high ion transference number of 0.912. The Zn//Zn symmetric cell achieves stable cycling for 2100 h while suppressing dendrites and side reactions. The assembled Zn//NVO has a high specific capacity of 164 mA h g⁻¹ at a load of 5 A g⁻¹ and a cycle life of over 7000 cycles with a capacity retention rate of 100%. This is due to the synergistic interaction between the large number of –SO₃⁻, –CONH–, and –OH functional groups contained in PMZA, which constructs a fast cation channel, inhibits the diffusion of SO₄²⁻ to the anode side, realizes abundant zinc–philic bonding sites, fast Zn²⁺ transport kinetics and efficient desolvation, and effectively curbs dendrites and other side reactions. This work provides a new solution for the development of high-performance gel electrolytes.