Sulfur Mismatch Substitution in Layered Double Hydroxides as Efficient Oxygen Electrocatalysts for Flexible Zinc–Air Batteries

Although layered double hydroxides (LDHs) are extensively investigated for oxygen electrocatalysis, their development is hampered by their limited active sites and sluggish reaction kinetics. Here, sulfur mismatch substitution of NiFe–LDH (S–LDH) is demonstrated, which are in-situ deposited on nitrogen-doped graphene (S–LDH/NG). This atomic-level sulfur incorporation leads to the construction of the tailored topological microstructure and the modulated electronic structure for the improved catalytic activity and durability of bifunctional electrocatalysts. The combined computational and experimental results clarify that the electron transfer between the sulfur anion and Fe³⁺ generates the high-valence Fe⁴⁺ species, while the mismatch substitution of the sulfur anion induces the metallic conductivity, an increased carrier density, and the reduced reaction barrier. Consequently, the as-fabricated Zn–air battery achieves a high power density of 165 mW cm^-2, a large energy density of 772 Wh kg_Zn^-1 at 5 mA cm^-2, and long cycle stability for 120 h, demonstrating its real-life operation.