Rational Design of an In‐Situ Polymer‐Inorganic Hybrid Solid Electrolyte Interphase for Realising Stable Zn Metal Anode under Harsh Conditions

The in‐depth understanding of the composition‐property‐performance relationship of solid electrolyte interphase (SEI) is the basis of developing a reliable SEI to stablize the Zn anode‐electrolyte interface, but it remains unclear in rechargeable aqueous zinc ion batteries. Herein, a well‐designed electrolyte based on 2 M Zn(CF3SO3)2‐0.2 M acrylamide‐0.2 M ZnSO4 is proposed. A robust polymer (polyacrylamide)‐inorganic (Zn4SO4(OH)6.xH2O) hybrid SEI is in situ constructed on Zn anodes through controllable polymerization of acrylamide and coprecipitation of SO42− with Zn2+ and OH−. For the first time, the underlying SEI composition‐property‐performance relationship is systematically investigated and correlated. The results showed that the polymer‐inorganic hybrid SEI, which integrates the high modulus of the inorganic component with the high toughness of the polymer ingredient, can realize high reversibility and long‐term interfacial stability, even under ultrahigh areal current density and capacity (30 mA cm−2~30 mAh cm−2). The resultant Zn||NH4V4O10 cell also exhibits excellent cycling stability. This work will provide a guidance for the rational design of SEI layers in rechargeable aqueous zinc ion batteries. A robust polymer‐inorganic SEI is in situ constructed on Zn anode through controllable polymerization and coprecipitation mechanism. Compared with bare Zn and recent in situ SEIs, polymer‐inorganic SEI combines both superiorities of polymer phases for high toughness and inorganic phases for high modulus, enabling stable electrode/electrolyte interface even under harsh conditions.