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Abstract Rechargeable aqueous Zn−MnO₂batteries are promising for stationary energy storage because of their high energy density, safety, environmental benignity, and low cost. Conventional gravel MnO₂cathodes have low electrical conductivity, slow ion (de‐)insertion, and poor cycle stability, resulting in poor recharging performance and severe capacity fading. To improve the rechargeability of MnO₂, strategies have been devised such as depositing micrometer‐thick MnO₂on carbon cloth and blending nanostructured MnO₂with additives and binders. The low electrical conductivity of binders and sluggish ion (de‐)insertion in micrometer‐thick MnO₂, however, still limit the fast‐charging performance. Herein, we have prepared porous carbon fiber (PCF) supported MnO₂cathodes (PCF@MnO₂), comprised of nanometer‐thick MnO₂uniformly deposited on electrospun block copolymer‐derived PCF that have abundant uniform mesopores. The high electrical conductivity of PCF, fast electrochemical reactions in nanometer‐thick MnO_2,and fast ion transport through porous nonwoven fibers contribute to a high rate capability at high loadings. PCF@MnO₂, at a MnO₂loading of 59.1 wt %, achieves a MnO₂‐based specific capacity of 326 and 184 mAh g⁻¹at a current density of 0.1 and 1.0 A g⁻¹, respectively. Our approach of block copolymer‐based PCF as a support for zinc‐ion cathode inspires future designs of fast‐charging electrodes with other active materials.