are limited by high cost, safety issues, poor recycling infrastructure, and growing concerns of resource scarcity. [4,5] Therefore, in the quest of finding alternative sustainable energy storage solutions, systems based on multivalent chemistries, such as Ca 2+ , Mg 2+ , Zn 2+ , Al 3+ , etc., should provide ample opportunities owing to their greater abundance, lower costs, superior safety features, in addition to their significantly higher volumetric energy densities. [6][7][8][9][10][11] In particular, zinc metal batteries (ZMBs) are highly intriguing because Zn anode shows high specific capacity (820 mAh g −1 ), high volumetric capacity of 5851 mAh cm −3 , nontoxicity, nonflammability, cost-effectiveness, large production, and easy processing. [12][13][14][15][16][17] Moreover, differently from other multivalent chemistries (Ca 2+ , Mg 2+ , Al 3+ ), the relatively higher redox potential of Zn (−0.76 V vs standard hydrogen electrode) makes it the only feasible choice as reversible anode for aqueous electrolytes. Certainly, taking advantage of the potentially large voltage window (>2 V) and high ionic conductivity of aqueous electrolytes, aqueous zinc metal batteries (AZMBs) might present an excellent high energy/power trade-off which is triggering the growing interest of this technology in the last years. [18,19] To date, AZMBs are mainly based on inorganic intercalation/ conversion cathode materials such as metal oxides (manganese, vanadium, etc.), transition metal dichalcogenides, polyanionic olivine-based phosphates, and Prussian blue analogs. [12,13,18,19] However, these cathode materials resulted in poor cell performances, exhibiting slow kinetics, low round-trip efficiency, and unstable cycling. This is due to the large cation size which hinders interfacial charge transfer and provokes strong electrostatic interactions between the highly charged Zn 2+ and the host inorganic framework causing destabilization of the crystal lattice and significant volume changes upon intercalation/deintercalation. [6][7][8][9][10][11] It is also important to highlight that most of these multivalent cathodes still involve toxic and/or environmentally unfriendly elements (except widely used MnO 2 ), which make further steps critical toward accomplishment of large-scale, sustainable energy storage systems. Therefore, the main challenge Aqueous zinc-metal batteries (AZMBs) are predicted to be an attractive solutions for viable, high-performance, and large-scale energy storage applications, but their advancement is greatly hindered by the lack of adequate aqueous electrolytes and sustainable cathodes. Herein, an ultra-robust Zn-polymer AZMB is demonstrated using poly(catechol) redox copolymer (P(4VC 86 -stat-SS 14 )) as the cathode and concentrated Zn(TFSI) 2 aqueous solution as stable electrolyte. The Zn(TFSI) 2 electrolyte shows enhanced iontransport properties and confers improved (electro)chemical compatibility with superior cell performance compared to traditional ZnSO 4 . The assembled Zn||P(4VC 86 -stat-SS 14 ) (2.5 mg cm ...
