Functionally Sulfur-Bridged Phenazine Polymer for Ultrarobust Aqueous Proton-Coupled Energy Storage

Aqueous proton-coupled energy storage systems enable ultrafast charging and intrinsic safety in aqueous electrolytes, but the durable anodes operating at low potential (<0.3 V vs SHE) in acidic conditions are still challenging. This work introduces 1,6-poly(phenazine sulfide) (1,6-PPS), a functionally sulfur-bridged phenazine polymer anode designed to overcome key challenges. Its minimalist architecture enables exceptional stability in 1 M H2SO4, exhibiting near-zero capacity decay over 10,000 cycles. 1,6-PPS also delivers ultrafast kinetics, retaining 56% of theoretical capacity (141 mAh g–1) at 50 A g–1 due to extended π-conjugation and high proton diffusivity (5 × 10–7 to 10–9 cm2 s–1). The synthesis maximizes redox-active phenazine density, achieving a high specific capacity of 255 mAh g–1. In a full cell with a N,N′-(2,5-dichloro-1,4-phenylene)bis(butane-1-sulfonamide) cathode, 1,6-PPS demonstrates a stable 0.77 V output and 96.4% capacity retention over 500 cycles. This work establishes sulfur-bridged phenazine polymers as durable, high-performance anodes for next-generation proton batteries.