Nicotinic acid additive with a double regulating mechanism for high-performance aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) are considered as future energy storage devices because of their high safety, low cost, and environmental friendliness. However, the growth of dendrites and side reactions have hindered their further development toward practical applications. Here, we for the first time propose to add trace amounts of nicotinic acid (NA) (0.3 g L-1) to 2 M ZnSO4 to prepare an optimized electrolyte for AZIBs. It is confirmed by experiments that NA not only replaces the water coordinated with Zn2+ to regulate the solvation structure, but also adsorbs on the zinc metal surface to reduce interface impedance, thus suppressing side reactions, including hydrogen evolution reactions (HER), corrosion and passivation, to achieve uniform Zn deposition and better deposition kinetic performance. Benefiting from this dual effect of solvent and interface regulation, the Zn||Zn symmetric cells exhibit ultra-long cycle stability of more than 5200 h under a current density of 1 mA cm-2 with a capacity of 1 mA h cm-2. The Zn||Ti cells display an ultra-high Coulomb efficiency (CE) of 99.2% during 400 cycles at the current density of 2 mA cm-2. In addition, the Zn||MnO2 full cells also exhibit excellent capacity retention and rate performance, far exceeding those of cells using pure ZnSO4 electrolyte. This work provides a new avenue for the development of low-cost additives to achieve high performance aqueous Zn-ion batteries. Trace nicotinic acid (NA) can not only change the solvation structure of Zn2+, but also preferentially adsorbs on the Zn anode to reduce the side reactions and inhibit Zn dendrites. Zn||Zn cells with NA can operate for 5200 h at 1 mA cm-2.