In-situ engineered dual-interface protective layer for enhanced zincophilicity and hydrogen evolution barrier in...

The practical deployment of aqueous zinc-ion batteries is hindered by severe interfacial instability at the zinc anode, including dendrite growth, parasitic reactions, and corrosion. To address these challenges, this work presents the fabrication of an ultrathin functional separator through depositing ZnIn₂S₄ onto a cellulose-based separator. The developed separator demonstrates impressive properties, including remarkable elastic modulus of 6.9 GPa, large ionic conductivity of 20.0 mS cm^-1, high zinc ion transference number, and outstanding electrolyte wettability. More importantly, during the electrochemical cycling, ZnIn₂S₄ undergoes in-situ electrochemical conversion on the zinc electrode surface, forming a dual-component protective interphase composed of zinc sulfide and metallic indium, the former of which exhibits strong zincophilicity while the latter possesses a high hydrogen evolution overpotential. Hence, the separator effectively facilitates homogeneous zinc nucleation and deposition and suppresses side reactions and corrosion, leading to greatly improved structural and chemical stability of the zinc electrode during prolonged cycling. Owing to the synergistic interfacial engineering, the Zn//Zn cells deliver stable operation for over 2000 h and 1000 h at current densities of 10 mA cm^-2 and 40 mA cm^-2 (2 mAh cm^-2), respectively. Full-battery tests further confirm broad applicability, offering 98.7% capacity retention after 1000 cycles (MnO₂ cathode) and stable performance over 15,000 cycles in the Zn//I₂ system. This work establishes a new design paradigm for next-generation separators.