Zinc-based flow batteries hold great potential for grid-scale energy storage because of their high energy density, low cost, and high security. However, the inferior reversibility of Zn²⁺/Zn on porous carbon electrodes significantly deteriorates long-term zinc anode stability and, thus, impedes further technological advances for zinc-based flow batteries. Herein, we propose nicotinamide (NAM) as a cost-effective additive to neutral ZnCl₂ anolyte, which realizes highly reversible zinc plating/striping reactions on carbon felt electrodes for zinc–iron flow batteries. Experimental characterization and theoretical calculation prove that the nicotinamide not only effectively reshapes the Zn²⁺ solvation structure by substituting two water molecules from the primary Zn²⁺-6H₂O solvation shell but also is capable of adsorbing on deposited zinc layers to regulate Zn²⁺ diffusion toward the electrode interface and avoid an undesirable tip effect, thereby affording uniformly dendrite-free zinc deposition and significantly enhanced Zn plating/striping reversibility. Benefiting from NAM additives, the zinc–iron flow battery demonstrates a good combination of high power density (185 mW cm^–2), long cycling stability (400 cycles, 120 h), enhanced resistance to self-discharge (98.9% capacity retention in 12 h), and preeminent battery efficiency (70% energy efficiency at 50 mA cm^–2), which provides a new pathway to developing a robust zinc anode for advanced flow batteries.

中文翻译：

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溶剂化结构和电极界面的协同调制为锌铁液流电池提供高度可逆的锌阳极

锌基液流电池因其高能量密度、低成本和高安全性而在电网规模储能方面具有巨大潜力。然而，多孔碳电极上Zn ²⁺ /Zn 较差的可逆性显着降低了锌负极的长期稳定性，从而阻碍了锌基液流电池的进一步技术进步。在此，我们提出烟酰胺 (NAM) 作为中性 ZnCl ₂阳极液的一种经济有效的添加剂，可在锌铁液流电池的碳毡电极上实现高度可逆的镀锌/剥离反应。实验表征和理论计算证明，烟酰胺不仅有效地重塑了Zn ²⁺溶剂化结构通过取代初级 Zn ²⁺ -6H ₂ O 溶剂化壳中的两个水分子，而且能够吸附在沉积的锌层上以调节 Zn ²⁺向电极界面的扩散并避免不希望的尖端效应，从而提供均匀的枝晶- 无锌沉积和显着增强的锌电镀/剥离可逆性。得益于 NAM 添加剂，锌铁液流电池表现出高功率密度 (185 mW cm ^-2 )、长循环稳定性（400 次循环，120 小时）、增强的抗自放电性（98.9% 容量保持在12 小时）和卓越的电池效率（在 50 mA cm ^{–2时能效为 70%})，这为开发用于先进液流电池的坚固锌阳极提供了一条新途径。