Controlling dendrite growth and side reactions in anode-free Zn-ion aqueous batteries with PMMA:Zn coated electrode

In this study, we propose the implementation of a protective layer consisting of a dense polymethylmethacrylate matrix containing Zn ions (PMMA:Zn) on the Cu electrode in Zn-ion aqueous batteries (ZABs). By introducing Zn2+ ions into the PMMA matrix, the PMMA:Zn coating layer exhibited significantly improved ion conductivity, enabling uniform Zn deposition between the PMMA layer and the current collector. This innovative coating effectively mitigated dendrite growth, hydrogen evolution reactions, and ZnO film formation, leading to enhanced electrochemical performance. The half-cell with PMMA:Zn-coated Cu foil exhibited remarkable sta-bility, achieving near 100 % Coulombic efficiency and enhanced rate capability even under high current densities of 10 mA cm-2. Moreover, in an anode-free configuration, the PMMA:Zn coating layer enabled extended cycling life and consistent operation. Furthermore, employing ZnMnO2 cathodes in the full cell configuration demonstrated elevated specific capacity of 257 mAh g-1 at a current density of 1 A g-1 and outstanding capacity retention over 80 % at the 300th cycle. These findings underscore the immense potential of the PMMA:Zn coating layer as a promising strategy for enhancing the performance and reliability of ZABs, thereby opening up possibilities for their practical integration in diverse energy storage systems.