Transformation of Rusty Stainless‐Steel Meshes into Stable, Low‐Cost, and Binder‐Free Cathodes for High‐Performance Potassium‐Ion Batteries

To recycle rusty stainless‐steel meshes (RSSM) and meet the urgent requirement of developing high‐performance cathodes for potassium‐ion batteries (KIB), we demonstrate a new strategy to fabricate flexible binder‐free KIB electrodes via transformation of the corrosion layer of RSSM into compact stack‐layers of Prussian blue (PB) nanocubes (PB@SSM). When further coated with reduced graphite oxide (RGO) to enhance electric conductivity and structural stability, the low‐cost, stable, and binder‐free RGO@PB@SSM cathode exhibits excellent electrochemical performances for KIB, including high capacity (96.8 mAh g −1 ), high discharge voltage (3.3 V), high rate capability (1000 mA g −1 ; 42 % capacity retention), and outstanding cycle stability (305 cycles; 75.1 % capacity retention).