Constructing Dense Morphology of Sn with High Reversibility under High Areal‐capacity for Anode‐Free Tin Batteries

Abstract Sn electrode possesses high reversibility, redox kinetics and corrosion resistance, as well as non‐toxic and environmental compatibility, which is competitive candidate for aqueous batteries. However, due to huge size of deposition particles and “dead Sn”, it is a great challenge to obtain high areal‐capacity (>5 mAh cm −2 ) and high coulombic efficiency (>99 %) simultaneously. Here, we demonstrate a highly reversible Sn redox electrochemistry with high areal‐capacity enabled by thiourea additive. Systematical investigations reveal the participation of thiourea molecules in the electrical double layer, reducing exchange current density and suppressing rampant two‐dimensional diffusion. As a result, flat and dense scale‐like deposition Sn morphology is obtained, which enables high cycle stability with high areal‐capacity of 10 mAh cm −2 for symmetrical cell with lean electrolyte (25 μL cm −2 ), and delivering a high average coulombic efficiency of 99.85 % with practical high 5 mAh cm −2 area‐capacity for asymmetrical cell. More importantly, anode‐free Organic||Sn battery is developed, and 62 % capacity retention can be obtained after 570 cycles.