High-performance dickite strengthened double-crosslinked hydrogel electrolytes for aqueous zinc-ion batteries

Abstract

The development of flexible devices has imposed higher demands on the mechanical and electrochemical properties of hydrogel electrolytes. To enhance the mechanical properties of hydrogels, this study prepared a composite hydrogel (P-D₃₀-DIOH₁) composed of covalently crosslinked polyacrylamide (PAM), diacetone acrylamide (DAAM), and expanded dickite (DIOH). The results indicated that PAM and DAAM could form a dual crosslinked network structure through hydrogen bonding and molecular chain entanglement, thereby improving the mechanical properties of the hydrogel. Furthermore, the surface of dickite, which is rich in -OH and SiO groups, could simultaneously form hydrogen bonds with PAM and DAAM, thus acting as an inorganic crosslinking agent. After expansion treatment, the dickite layers were fully exposed, increasing the specific surface area and further enhancing the physical crosslinking effect of dickite. Mechanical testing revealed that the tensile strength of the DAAM and DIOH reinforced P-D₃₀-DIOH₁ hydrogel reached 0.374 MPa, with a tensile elongation of 2100 % and a compressive strength of 0.308 MPa at 75 % deformation. P-D₃₀-DIOH₁ hydrogel electrolyte exhibited a high ionic conductivity (20.7 mS cm⁻¹), attributed to the negatively charged expanded dickite, which enriched Zn²⁺ and formed rapid Zn²⁺ transport channels under the electric field. The P-D₃₀-DIOH₁ hydrogel effectively stabilized the surface of the Zn anode, inhibited the growth of Zn dendrites, and reduced the formation of by-products. When the P-D₃₀-DIOH₁ hydrogel electrolyte was assembled into the MnO₂//Zn battery, it operated stably for 700 cycles, maintaining a specific discharge capacity of 118 mAh g⁻¹ at a current density of 150 mA g⁻¹. Moreover, the battery delivered a specific discharge capacity of 270 mA h g⁻¹ at 60 mA g⁻¹, and even at 600 mA g⁻¹, it retained a high reversible capacity of 115 mAh g⁻¹, demonstrating excellent electrochemical performance. Furthermore, the assembled flexible battery continued to function effectively under physical deformations such as bending, impact, and puncture.