Self-adsorbing electrolyte additive promoting Zn(002) deposition on Zn anode for aqueous zinc-ion battery

The poor cycling stability of aqueous zinc-ion batteries (AZIBs), caused by zinc dendrite growth and surface corrosion-induced passivation at the zinc anode, significantly hinders their practical development. In this work, 7-(2,3-dihydroxypropyl)theophylline (DHTP) is introduced as a functional additive into Zn(CF₃SO₃)₂ (ZOT) electrolyte to regulate the anode-electrolyte interface and mitigate side reactions. Theoretical calculations and experimental characterizations reveal that DHTP preferentially adsorbs on the zinc anode, reducing direct water contact and thereby suppressing hydrogen evolution and corrosion reactions. Notably, DHTP exhibits the lowest adsorption energy on the Zn(002) crystal plane, which optimizes Zn²⁺ diffusion and deposition behavior, guiding the preferential growth of the Zn(002) plane. Benefiting from this, the Zn||Zn symmetric cell with DHTP achieves stable cycling for over 800 h at 1 mA cm^-2 and 1 mAh cm^-2, outperforming the bare electrolyte. Furthermore, the Zn||NaV₃O₈·1.5H₂O full cell demonstrates exceptional durability of 9,000 cycles with a remarkable capacity retention of 89 % under a high current density of 10 A g^-1. This molecular adsorption strategy based on DHTP provides a novel approach to constructing highly reversible zinc anodes for advanced AZIBs.