A self-optimized dual zinc/copper-electrolyte anodic interfaces by mechanical rolling toward zinc ion batteries with high capacity and long cycle life

The aqueous Zn ion batteries are considered ideal energy storage systems because of their high safety, environment-friendly properties, and abundant reserve. However, an uncontrollable Zn-electrolyte interface (ZEI) hinders the practical application. Herein, a dual-ZEI Zn/Cu composite is designed by one-step mechanically rolling Zn foil and Cu foam (RCZ), which possesses different zincophilicity. As-fabricated RCZ electrode in symmetric cells at various current densities and capacities exhibits unique self-optimized polarization behavior, as well as extraordinarily stable and long lifespan dendrite-free Zn deposition/stripping. As the electrodes in symmetric cells measured at 1 mA/cm2 and a capacity of 1 mA h/cm2, RCZ exhibits long life of more than 1800 h and unique self-optimized polarization behavior from an initial 80 mV–30 mV. Through both two-electrode and three-electrode systems, the individual deposition and stripping behavior have been systematically examined to unravel the synergistic effects of dual-ZEIs (Cu-electrolyte and Zn-electrolyte), which in-situ generated and self-optimized Zn/Cu composite in the top porous structure with almost endless Zn source from the bottom zinc layer plays the critical role. The advantages of mechanical rolling assist electrode-electrolyte interface design and the underlying mechanism studies provide important insights into the practical application principles of Zn metal anodes. [Display omitted] •A novel stacking structure of Zn/Cu composites by one-step mechanically rolling planar Zn foil and Cu foam.•Zn foil is partially filled in the Cu foam.•The dual zinc-electrolyte interface structure has two layers with different zincphilicity and structures.•Unique self-optimization in various current densities and capacities.