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 Zn²⁺, 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 Zn²⁺. 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.