20 nm-ultra-thin fluorosiloxane interphase layer enables dendrite-free, fast-charging, and flexible aqueous zinc metal batteries

Abstract

Dendrite growth of zinc (Zn) anode at high current density severely affects the fast-charging performance of aqueous zinc metal batteries (AZMBs). While interfacial modification strategies can optimize Zn performance, challenges such as complicated preparation processes, excessive layer thicknesses, and high voltage hysteresis should be addressed. Herein, we utilize a cost-effective liquid fluorosiloxane, (3,3,3-trifluoropropyl)trimethoxysilane, for scalable modification of Zn foil via drop-casting at room temperature, resulting in an ultra-thin interphase layer of only 20 nm. The Si-O-Zn bonds formed between fluorosiloxane and Zn ensure interfacial stability, and the Si-O-Si bonds between fluorosiloxane molecules help to homogenize the electric field distribution. Additionally, the abundant highly electronegative fluorine atoms on the anode surface act as zincophilic sites, promoting the uniform deposition of Zn²⁺. Thus, the modified Zn foil (SiFO-Zn) exhibits excellent dendrite suppression, reduced voltage hysteresis, and prolonged cycle life at ultra-high current density (40 mA/cm²), achieving a cumulative areal capacity of 12.9 Ah/cm². Further, the full cell assembled with 10 μm-thick SiFO-Zn anode and MnO₂ cathode achieves 2600 cycles at 5 A/g with minimal capacity degradation, and a large-size (22.5 cm⁻²) pouch cell powers the light-emitting diode even after reverse bending, demonstrating the potential of AZMBs for fast-charging flexible devices.