Ah-level small-molecule proton batteries enabled by a cost-effective gradient-porous composite separator

Small-molecule–based aqueous proton batteries using conjugated organic anodes and protons as charge carriers offer low cost, fast kinetics, and long cycle life, showing strong potential for next-generation energy storage. However, their performance is severely limited by insufficient interfacial charge transport kinetics and instability issues arising from molecular dissolution and shuttling. In this study, we develop a gradient-porous composite separator (GF-S-5) by modifying a glass fiber (GF) substrate with sulfonated polyether ether ketone (SPEEK). This separator combines the microporous structure of SPEEK with the mesoporous/macroporous characteristics of GF, enabling efficient and selective proton transport while effectively mitigating the shuttling issue of the organic small-molecule anode material, hexaazatrinaphthalene-2, 8, 14-tricarbonitrile (HATN-3CN). Experimental results indicate a reversible capacity of 262.2 mAh g⁻¹ at 1 A g⁻¹ and 98.8% capacity retention after 4000 cycles for the HATN-3CN‖MnO₂ battery with the GF-S-5 separator. Additionally, a high-mass-loading HATN-3CN anode (35.6 mg cm⁻²) is assembled into a pouch cell, which consistently yields a capacity of 1.03 Ah, corresponding to an energy density of 35.4 Wh kg⁻¹ (based on the electrode stack mass), sufficient to power practical devices. This study offers a cost-effective separator engineering strategy for the advancement of high-performance, long-lifetime aqueous proton batteries toward practical applications.