Achieving Ultrahigh Energy Density and Long Durability in a Flexible Rechargeable Quasi‐Solid‐State Zn–MnO 2 Battery

Advanced flexible batteries with high energy density and long cycle life are an important research target. Herein, the first paradigm of a high‐performance and stable flexible rechargeable quasi‐solid‐state Zn–MnO 2 battery is constructed by engineering MnO 2 electrodes and gel electrolyte. Benefiting from a poly(3,4‐ethylenedioxythiophene) (PEDOT) buffer layer and a Mn 2+ ‐based neutral electrolyte, the fabricated Zn–MnO 2 @PEDOT battery presents a remarkable capacity of 366.6 mA h g −1 and good cycling performance (83.7% after 300 cycles) in aqueous electrolyte. More importantly, when using PVA/ZnCl 2 /MnSO 4 gel as electrolyte, the as‐fabricated quasi‐solid‐state Zn–MnO 2 @PEDOT battery remains highly rechargeable, maintaining more than 77.7% of its initial capacity and nearly 100% Coulombic efficiency after 300 cycles. Moreover, this flexible quasi‐solid‐state Zn–MnO 2 battery achieves an admirable energy density of 504.9 W h kg −1 (33.95 mW h cm −3 ), together with a peak power density of 8.6 kW kg −1 , substantially higher than most recently reported flexible energy‐storage devices. With the merits of impressive energy density and durability, this highly flexible rechargeable Zn–MnO 2 battery opens new opportunities for powering portable and wearable electronics.