Motif-coded phycocyanin enables coupled solvation-interphase-texture regulation for reversible aqueous zinc batteries

Aqueous zinc batteries offer a safe and cost-effective platform for large-scale energy storage, yet their practical application is impeded by the strong hydration of Zn 2+ , water-induced parasitic reactions, and uncontrolled Zn deposition. Here, we report phycocyanin (PC), a naturally derived protein-pigment biomacromolecule, as a motif-coded electrolyte regulator for reversible Zn electrochemistry. Its chemically differentiated molecular architecture enables cooperative regulation across the electrolyte and Zn/electrolyte interface. Spectroscopic analyses and molecular dynamics simulations show that PC reorganizes the local Zn 2+ –H 2 O–SO 4 2- coordination environment toward reduced hydration and increased sulfate involvement. Depth-profile XPS and Raman characterization further reveal the preferential surface enrichment of PC-derived organic species after prolonged cycling, while XRD and morphological analyses demonstrate the evolution toward compact, Zn(002)-preferred deposition. Consequently, Zn||Zn symmetric cells operate stably for over 5400 h at 2 mA cm -2 , and Zn||Cu cells deliver an average Coulombic efficiency of 99.77%. Moreover, Zn||PANI full cells deliver a capacity retention of 88.1% after 9000 cycles at 2 A g -1 , demonstrating competitive symmetric-cell longevity and full-cell cycling durability. This work advances biomolecular electrolyte additives from empirical performance optimization toward motif-coded molecular regulation, offering a structure-guided design principle for sustainable aqueous metal batteries. Download: Download high-res image (437KB) Download: Download full-size image