Reshaping\nthe Electrolyte\nSolvation Structure and\nElectrical Double Layer with Potassium Citrate To Stabilize the Zn\nAnode

Aqueous zinc-ion batteries (ZIBs)\nare regarded as a potential\nalternative\nto lithium-ion batteries, offering several advantages, including low\ncost, environmental compatibility, and high safety. However, dendrite\ngrowth and side reactions on the Zn anode surface can seriously shorten\nthe cycle life of ZIBs. Herein, the Zn anode was significantly stabilized\nin the ZnSO<sub>4</sub> electrolyte by adding potassium citrate to\nregulate the electrical double layer (EDL) structure. Cit<sup>3–</sup> (citrate ion) features a higher lone-pair electron density than\nH<sub>2</sub>O, partly replacing the H<sub>2</sub>O of the inner solvation\nsheath around Zn<sup>2+</sup>. In addition, Cit<sup>3–</sup> is preferentially adsorbed on the Zn metal surface rather than on\nthe water dipole, forming an EDL structure that is poor in H<sub>2</sub>O. Both are proven to be capable of inhibiting side corrosion reactions\nand inducing Zn uniform deposition behavior. Encouragingly, a long\ncycle life (2000 h) for Zn//Zn symmetric cells has been achieved at\n0.5 mA cm<sup>–2</sup> using potassium citrate additive, with\ncycle life exceeding 1500 h under more severe conditions (10 mA cm<sup>–2</sup>, 2.5 mAh cm<sup>–2</sup>). The assembled Zn-ion\nhybrid capacitor can stably cycle for 10,000 cycles even at a high\ncurrent density of 5 A g<sup>–1</sup>, further demonstrating\nthe positive effect of potassium citrate for practical application.\nThis study inspires the design of efficient electrolyte additives\nfor the development of stable aqueous ZIBs.