Gradient fluorinated alloy to enable highly reversible Zn-metal anode chemistry

Abstract

The unsatisfactory reversibility of zinc (Zn) metal anodes seriously hinders their wide practical application. This corresponds to two major issues, namely the notorious dendrite growth and exacerbated hydrogen evolution, resulting in reduced cycling stability and premature battery failure. Herein, we solve these two issues through a facile solution-dipping approach that in situ constructs a protective coating based on spatial gradient fluorinated alloy particles. Due to the synergistic combination of the advantages of electric conductive coatings, insulating coatings and 3D structural frameworks, it presented highly reversible Zn metal anode chemistry with a dendrite-free feature and the effective suppression of gas production. The protected Zn anode was stable enough to sustain cycling at a practical areal capacity of 3 mA h cm⁻² at 3 mA cm⁻². The improved reversibility was further embodied by coupling it with an I₂ cathode in full cells, which showed remarkable superiority compared to using a bare Zn anode. When assembled in bipolar pouch cells with an areal capacity of 6 mA h cm⁻², the corresponding Zn utilization ratio reached 34% and stable cycling performance was maintained for 300 cycles. This method can serve as an effective avenue to regulate Zn metal reversibility and can be readily extended to other surface-protective coatings with specific properties.