Interlayer modification of dickite and liquid content quantification for high cation-selective quasi-solid-state electrolytes

In this work, dickite was employed as the host matrix, while urea and dimethyl sulfoxide (DMSO) were introduced as intercalation guests. Dickite-urea (WDU) and dickite-DMSO (WDD) intercalation composites were prepared via solid-state grinding and solution intercalation methods, respectively, and subsequently mixed with aqueous electrolyte to construct clay-based quasi-solid-state electrolytes. The plastic limit and liquid limit concepts from soil science were innovatively introduced to quantitatively characterize the water-retention capability and rheological state of the clay-based quasi-solid-state electrolytes. Furthermore, the regulatory mechanism of electrolyte liquid content on Zn 2+ transference number and ionic rectification effect was systematically elucidated. The results demonstrated that intercalation modification significantly enlarged the interlayer spacing of dickite while increasing the specific surface area and surface electronegativity. The Zeta potential decreased from −15.78 mV for pristine dickite to −20.51 mV for WDU and − 25.46 mV for WDD, respectively, thereby enhancing the water-retention capability and cation selectivity of the system. The ion transport behavior and ionic rectification effect were strongly dependent on the liquid content of the clay-based quasi-solid-state electrolyte. When the liquid content reached 67% of the plastic limit of the dickite-urea/dickite-DMSO intercalated clay systems, the free-water content in the quasi-solid-state electrolyte was significantly reduced, accompanied by a well-matched electric double layer structure, enabling efficient relay-type Zn 2+ transport while significantly suppressing SO 4 2− migration. Under the optimal liquid content condition, the quasi-solid-state electrolyte WDU1.0 achieved an ultrahigh Zn 2+ transference number of 0.95, and the assembled Zn||Zn symmetric cell operated stably for 2000 h at a current density of 0.2 mA cm −2 without dendrite formation or by-product generation, while the Zn||MnO 2 full cell retained 89.71% of its capacity after 500 cycles at 150 mA g −1 .