Ultra‐Low‐Cost Hydrophobic Organic Coating for Highly Reversible Zinc Anodes

ABSTRACT Electrolyte additive engineering offers a promising pathway for achieving dendrite‐free aqueous zinc‐ion batteries (ZIBs) while facing challenges related to hydrophilic characteristics and/or high loading requirements. Herein, we developed a cost‐effective and scalable facile immersion treatment to deposit a hydrophobic 1,3‐Di(o‐tolyl)thiourea (DTH) layer with nanoscale thickness (≤ 14 nm). This approach yields an ultra‐low DTH loading (5.37 × 10 −13 M) and exceptional cost efficiency (1.43 × 10 −7 USD Ah −1 ), surpassing conventional water‐miscible organic additives and biomass‐derived counterparts by orders of magnitude. The hydrophobic DTH layer optimizes Zn electrochemistry and mitigates parasitic reactions, irrespective of the immersion sequence in the same batch of ethanol solution. Consequently, the Zn||ODASnI 4 (ODA denotes 1,8‐octadiamine) coin cell demonstrated stable operation over 2500 cycles at 2 A g −1 with a low additive cost of 1.43 × 10 −6 USD per cell. The pouch cell showed an average coulombic efficiency (CE) of 99.9% and 72% capacity retention after 1200 cycles, incurring an ultra‐low additive cost of 7.02× 10 −5 USD while delivering a high energy density of 143 Wh kg −1 (based on cathode mass). This work enabled durable and high‐performance ZIBs at minimal cost, providing a foundation for further exploration of low‐cost, scalable strategies in aqueous battery systems.