In Situ Growth of an Ultrathin Polymer Brush Layer Enables a Reversible Zinc Anode

Aqueous zinc-ion-based devices exhibit an attractive prospect in large-scale energy storage due to their safe, environmentally friendly, and low-cost characteristics. Nevertheless, the Zn metal anode suffers critically from severe parasitic reactions and Zn dendrites, mainly as a result of the lack of stable interphase layers. Herein, we propose the in situ grafting of an ultrathin molecular brush (≈10 nm thickness) as an artificial solid electrolyte interphase (SEI) for a highly reversible dendrite-free Zn anode by a surface-grafting strategy. The dense sulfonate functional groups of the poly[[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)] (PSBMA) SEI layer simultaneously inhibit the penetration of SO₄^2-, avoiding the occurrence of side reactions. Meanwhile, the PSBMA layer allows a uniform Zn-ion concentration field and fast Zn²⁺ migration kinetics, leading to a dendrite-free Zn anode. Therefore, the half cell using the PSBMA-modified Zn anode achieves a high average Coulombic efficiency of 99.80% over 1000 cycles at 5 mA cm^-2. In symmetrical cells, the PSBMA-modified Zn anode exhibits an ultralong lifespan of over 3300 h, far exceeding that of the bare Zn anode (120 h). As proof-of-concept demonstration, the full cells with MnO₂ and activated carbon cathodes deliver a superior capacity retention ratio. Our findings show that the construction of in situ SEI layers has promising applications in high-performance aqueous battery technology.