Acceptor-Enriched Charge-Transfer Engineering for Long-Life and High-Rate Organic Cathodes in Aqueous Proton Batteries

Aqueous proton batteries (APBs) are promising for safe energy storage, yet their cathode development is hindered by the lack of organic materials with reversible redox activity and long cycling stability in acidic media. Herein, an acceptor-enriched PNZ–TCNQ organic charge-transfer complex was constructed by increasing the TCNQ ratio. Spectroscopic results are consistent with strengthened donor–acceptor interactions and altered local electronic environments. The PNZ–TCNQ cathode delivered ~190 mAh g−1 at 0.6 A g−1 and retained ~85% capacity after 10,000 cycles at 5 A g−1 in acidic three-electrode tests. Kinetic analyses revealed mixed charge storage contributions from pseudocapacitive and diffusion-influenced processes. In situ/ex situ characterizations confirmed reversible redox evolution of the donor–acceptor complex with preserved molecular backbones. This work shows that tuning intermolecular charge-transfer interactions is an effective strategy for improving the cycling stability of organic cathodes in acidic aqueous electrolytes.