Achieving Dendrite-Free and By-Product-Free Aqueous Zn-Ion Battery Anode via Nicotinic Acid Electrolyte Additive with Molecule-Ion Conversion Mechanism

The widespread adoption of aqueous Zn ion batteries is hindered by the instability of the Zn anode. Herein, an elegant strategy is proposed to enhance the stability of Zn anode by incorporating nicotinic acid (NA), an additive with a unique molecule-ion conversion mechanism, to optimize the anode/electrolyte interface and the typical ZnSO₄ electrolyte system. Experimental characterization and theoretical calculations demonstrate that the NA additive preferentially replaces H₂O in the original solvation shell and adsorbs onto the Zn anode surface upon conversion from molecule to ion in the electrolyte environment, thereby suppressing side reactions arising from activated H₂O decomposition and stochastic growth of Zn dendrites. Simultaneously, such a molecule-to-ion conversion mechanism may induce preferential deposition of Zn along the (002) plane. Benefiting from it, the Zn||Zn symmetric battery cycles stably for 2500 h at 1 mA cm⁻², 1 mAh cm⁻². More encouragingly, the Zn||AC full batteries and the Zn||AC full batteries using NA electrolyte and Zn||VO₂ full batteries also exhibit excellent performance improvements. This work emphasizes the role of variation in the form of additives (especially weak acid-based additives) in fine-tuning the solvation structure and the anode/electrolyte interface, hopefully enhancing the performance of various aqueous metal batteries.