The attractive advantages of the Zn metal anode and water-based electrolyte, such as inherent safety and low cost, endow the zinc-ion batteries (ZIBs) with great potential in the future energy storage market. However, the severe surface side reactions and dendrites affect the service lifespan and electrochemical performance of ZIBs. Herein, a bifunctional electrolyte additive, l-ascorbic acid sodium (LAA), has been added into ZnSO4 (ZSO) electrolyte (ZSO + LAA) to settle the above issues of ZIBs. On the one hand, the LAA additive tends to adsorb on the Zn anode surface to generate a H2O-resistive passivation layer, which can effectively isolate the H2O corrosion and regulate the Zn2+ ion 3D diffusion, thus inducing a uniform deposition layer. On the other hand, the strong adsorption capacity between LAA and Zn2+ can transform the solvated [Zn(H2O)6]2+ into [Zn(H2O)4LAA], thus reducing the coordinated H2O molecules and further suppressing side reactions. With this synergy effect, the Zn/Zn symmetric battery with the ZSO + LAA electrolyte can deliver a cycle life of 1200 h under 1 mA cm-2, and the Zn/Ti battery also presents an ultrahigh Coulombic efficiency of 99.16% under 1 mA cm-2, greatly superior to the batteries with the ZSO electrolyte. Additionally, the effectiveness of the LAA additive can be further verified in the Zn/MnO2 full battery and pouch cell.
Keywords: LAA additive; dendrite-free; side reactions; uniform deposition; zinc-ion battery.