Dual-phase interface engineering via parallel modulation strategy for highly reversible Zn metal batteries

The reversibility and stability of aqueous Zn metal batteries (AZMBs) are largely limited by Zn dendrites and interfacial parasitic reactions. Herein, we propose a parallel modulation strategy to boost the reversibility of the Zn anode by introducing N,N,N’,N’-tetramethylchloroformamidinium hexafluorophosphate (TCFH) as an additive in the electrolyte. TCFH is composed of PF₆⁻ and TN⁺ with opposite charges. PF₆⁻ can spontaneously induce the in-situ generation of ZnF₂ solid electrolyte interface (SEI) on the anode, which can improve the transport kinetics of Zn²⁺ at the interface, thus promoting the rapid and uniform deposition of Zn as well as inhibiting the growth of dendrites. In addition, TN⁺ is enriched at the anode surface during Zn deposition through the anchoring effect, which brings a reconfiguration of the ion/molecule distribution. The anchored-TN⁺ reduces the concentrations of H₂O and SO₄²⁻, sufficiently restraining the parasitic reaction. Thanks to the dual-phase interface engineering constructed of PF₆⁻ and TN⁺ in parallel, the symmetric cell with the proposed electrolyte survives long cycling stability over 750 h at 20 mA cm⁻², 10 mAh cm⁻². This study offers a distinct viewpoint to the multidimensional optimization of Zn anodes for high-performance AZMBs.