Dickite nanolayers for ultrathin anode coatings in highly stable zinc-ion batteries

Abstract

In aqueous zinc-ion batteries (AZIBs), Zn anode faces issues such as uncontrolled dendrite growth, electrode corrosion, and by-product formation. This study successfully exfoliated a 1:1 type layered clay mineral, dickite, into ultrathin dickite nanolayers (DE) with a layer thickness of less than 5 nm and a yield of over 40 % using an ultrasonic-assisted solvothermal method. These ultrathin dickite nanolayers were mixed with sodium alginate (SA) and coated onto a zinc matrix to obtain a coated Zn electrode (DE-Zn). Due to the abundant hydrophilic groups on the surface of the ultrathin dickite nanolayers, the DE-SA coating exhibited excellent electrolyte affinity. The uniform dispersion of ultrathin dickite nanolayers in the SA matrix constructed a polygonal network structure, providing rapid ion transport channels. The unique surface negative charge characteristics of the ultrathin dickite nanolayers allowed for significant ion selectivity, enhancing Zn²⁺ migration efficiency by adsorbing Zn²⁺ and repelling SO₄²⁻ in the electrolyte. The symmetric cell assembled with DE-Zn electrodes demonstrated stable operation for up to 5500 h at 0.5 mA cm⁻², with a polarization voltage of 40 mV, and remained stable even at 10 mA cm⁻². The addition of ultrathin dickite nanolayers to the coating inhibited dendrite growth, HER, and by-product formation, maintaining a stable zinc electrode interface. The DE-Zn//MnO₂ full cell assembled with DE-Zn electrodes maintained a high discharge specific capacity (144 mAh g⁻¹) after 750 cycles at 0.15 mA g⁻¹, exhibiting excellent electrochemical performance. This work provides new scientific insights for the low-cost, efficient exfoliation of clay minerals and the preparation of high-performance AZIBs.