Bipyridine: a bidentate trace additive for a durable zinc anode

The practical deployment of aqueous zinc-ion batteries is primarily hindered by uncontrolled zinc dendrite growth and parasitic side reactions at the anode. Here, we introduce 2,2′-bipyridine (BPY) as a trace bidentate electrolyte additive to tackle these challenges. Through its preferential adsorption at the electrode interface, BPY displaces water molecules to form a dehydrated electric double layer and promotes the in situ construction of a robust, N–Zn-bonded solid electrolyte interphase (SEI). Concurrently, its bidentate coordination with Zn 2+ ions modulates the solvation structure, facilitating uniform zinc nucleation and deposition. This dual-mechanism regulation leads to exceptional electrochemical performance: Zn||Zn symmetric cells achieve an ultra-long cycle life of 5400 h at 1 mA cm −2 /1 mAh cm −2 , and Zn||Cu cells exhibit a high average Coulombic efficiency of 99.5% over 2380 cycles. The practical viability is demonstrated in full cells, in which the Zn||MnO 2 configuration retains 80% of its initial capacity after 1000 cycles at 1 A g −1 , and Zn||PANI cells deliver over 3500 stable cycles at a high rate of 5 A g −1 . This work provides a fundamental understanding of how a trace bidentate additive can simultaneously regulate interfacial chemistry and bulk solvation, offering a simple and effective strategy for developing high-performance, durable zinc-based energy storage systems.