Zincophilic and slightly hydrophobic separator with multifunctional groups enables dendrite-free Zn Metal anode via ion sieving and interfacial confinement effect

Aqueous zinc-ion batteries (AZIBs) are regarded as a prospective contender for next generation of energy storage devices, offering a cost-effective and inherently safe solution. However, the traditional glass fiber separators (GF) with irregular pore sizes, fragile structures and excellent hydrophilicity results in the uneven zinc deposition and undesirable side reactions. In this study, a zincophilic and slightly hydrophobic membrane (SHM) was developed through a single-step ball milling and rolling process of a mixture comprising polytetrafluoroethylene (PTFE) and 3-amino-4-hydroxybenzenesulfonic acid (AHBA). The functional groups (-SO3H) facilitate the formation of Zn-O coordination bonds with Zn ions, thereby indicating good zincophilicity and high mass transfer. This ion sieving effect results in the homogenisation of the Zn-ion flux and the enabling of dendrite-free Zn deposition. Moreover, the combined effect of PTFE and AHBA can efficiently restrict the transport of H2O and anions on the Zn surface. This interfacial confinement effect can moderately increase the hydrophobicity of the SHM separator to minimize subsequent side reactions. The SHM separator exhibits a high ionic conductivity of 17.6 mS cm- 1 and a transference number of 0.76 for Zn2+. The Zn//Zn symmetric battery with SHM separator exhibits reversible zinc plating/stripping for 1600 h at a current density of 1 mA cm- 2, accompanied by a high Coulombic efficiency of 99.48 %. The modified Zn//MnO2 full battery can retain 175.1 mAh g- 1 after 1500 cycles at a rate of 3C. This effective strategy provides a promising avenue for the design of multifunctional separators in AZIBs.