Design of Palygorskite–based Quasi-solid-state electrolyte and Construction of Stable Electrode/Electrolyte Interface for High Cycling Stability Aqueous Zinc-ion Batteries

Abstract

The practical application of Aqueous Zinc-ion Batteries (AZIBs) is limited by corrosion, hydrogen evolution reaction (HER), and formation of by-products, which are triggered by the free water in the aqueous electrolyte. To suppress the adverse effects of free water, a clay-based quasi-solid-state electrolyte (D-PalE) was prepared using modified clay mineral palygorskite. The modified palygorskite had an increased number of hydrophilic groups that could bind water molecules through hydrogen bonding, enhancing bound water's content and reducing free water's content in the quasi-solid-state electrolyte. It resulted in a stronger constraining effect on free water molecules, accelerated the desolvation process of [Zn(H₂O)₆]²⁺, and suppressed the HER caused by the enrichment of active water molecules at the anode/electrolyte interface. Additionally, the electric double layer induced by the negative charges on modified palygorskite exhibited ion selectivity, improving the migration efficiency of zinc ions, inhibiting the transport of anions, and suppressing the formation of the by-products Zn₄SO₄(OH)₆·H₂O (ZSH). Ultimately, the ionic conductivity of D-PalE reached up to 9.92 mS cm⁻¹. The Zn//D-PalE//Zn cell achieved stable cycling for 2000 h at a current density of 0.2 mA cm⁻². The Zn//D-PalE//MnO₂ full cell delivered an initial discharge specific capacity of 244 mAh g⁻¹ at 0.5C, with a capacity retention of 95.29 % after 500 cycles and an average coulombic efficiency of 99.8 %.