Achieving ultra-long cycle stability in aqueous zinc-ion batteries via multifunctional synergistic effects of ammonium citrate

In response to the challenges faced by zinc anodes in aqueous zinc-ion batteries, such as dendrite growth and interface corrosion, this study utilizes ammonium citrate (AC) as a multifunctional additive, leveraging its dual-ion synergistic mechanism to enhance the stability of the zinc anode interface. The experimental and theoretical results obtained from this study provide substantial evidence that, following the introduction of AC, Cit 3- and NH 4 + achieve triple functionality through a process known as “bulk-interface” synergistic interactions: (1) The -COO - /-OH groups of Cit 3- chelate Zn 2+ to reorganize the solvation shell, accelerating Zn 2+ desolvation kinetics and reducing interfacial active water content; (2)Cit 3- and NH 4 + dynamically adsorb onto the electrode surface, preferentially occupying highly active sites and forming a “shielding effect” layer on the zinc metal surface. AC decomposes in situ to form an inorganic-organic hybrid solid electrolyte interphase (SEI). This SEI effectively prevents water-involved side reactions and regulates the uniform diffusion of Zn 2+ ; (3) AC/AC - and NH 4 + /NH 3 dual buffers exhibit enhanced pH buffering capacity through synergistic effects, effectively suppressing fluctuations in stable interface pH and inhibiting the formation of passivation products. Experimental results demonstrate that the incorporation of AC enables the Zn||Zn symmetric cell to achieve an ultra-long cycling of 5670 h at 0.5 mA cm -2 /0.5 mAh cm -2 (a 38-fold improvement over the basic electrolyte’s 147 h), with a coulombic efficiency of 99.9%. The full cell paired with the MnO 2 cathode maintained a reversible specific capacity of 174 mAh g -1 after 1100 cycles at a current density of 1 A g -1 , achieving a capacity retention rate of 75.8%. These findings provide new insights for designing multifunctional additives for aqueous zinc-ion batteries.