Polyoxometalate–polymer hybrid artificial layers for ultrastable and reversible Zn metal anodes

Zn is considered a promising anode candidate for aqueous metal batteries owing to its high theoretical capacity, proper deposition potential within the electrochemical stability window of aqueous electrolytes, and low cost. However, dendrite formation, passivation layers, and hydrogen evolution reactions limit the reversibility and stability of Zn metal anodes. Herein, we demonstrate an organic–inorganic hybrid layer composed of polyoxometalate (POM) and poly(ethylene glycol) dimethyl ether (PEGDME) on the Zn metal surface. The POM–PEGDME hybrid layer, composed of POM known as an ‘electron sponge’ and PEGDME with high ionic conductivity, was obtained through a facile slurry coating method. While POM provided an energetically favorable zincophilic surface, PEGDME assisted in the formation of a thin (10–15 nm) and uniform artificial interface layer and diversified the oxidation number of molybdenum in POM. The POM-PEGDME-coated Zn metal anode achieved a high cumulative capacity of 9,050 h at 10 mA cm−2, delivering approximately 1.7 times higher capacity retention than that of bare Zn foil in a battery cell paired with a β-MnO2 cathode. This study provides significant implications for designing synergized organic–inorganic hybrid artificial layers for metal anode protection.