Relay Storage of Protons and Zinc Ions Enables Practical High‐Mass‐Loading Organic Electrodes

Rechargeable Zn–organic batteries hold great promise for sustainable energy storage, yet most reported high performances are achieved only at low mass loadings (2–3 mg cm −2 ), far from practical application. Here, we investigate poly(benzoquinonyl sulfide) (PBQS) electrodes working in a water‐in‐salt electrolyte and reveal that PBQS first undergoes faradaic proton insertion during discharge, which is subsequently displaced by Zn 2+ , releasing protons back into the electrolyte. This dynamic relay allows a small amount of H + to cycle repeatedly, acting as a kinetic buffer that offset the sluggish diffusion of Zn 2+ . Owing to this mechanism and PBQS's high conductivity, a low‐carbon (10 wt.%) PBQS electrode with an ultrahigh mass loading of 100 mg cm −2 delivers a capacity of 187.1 mAh g −1 (∼96% of low‐loading capacity) and achieves a record areal capacity of 18 mAh cm −2 . The electrode also exhibits excellent rate capability and cycling stability, suggesting its strong potential for practical applications.