Malic acid additive with a dual regulating mechanism for high-performances aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are widely used in energy storage devices due to their high safety and low cost. However, the practical application of AZIBs is constrained by the formation of dendrites and the occurrence of severe side reactions. Herein, these problems are addressed by introducing malic acid (MA) as a multifunctional additive into electrolyte. Theoretical calculations, finite element simulations and experimental tests show that MA can adsorb on the surface of the Zn anode and change the solvated structure of Zn 2+ and promote the desolvation of [Zn (H 2 O) 6 ] 2+ , thus inhibiting the hydrogen evolution reaction (HER) and the generation of by-products, and promoting the uniform deposition of Zn. Additionally, benefiting from this dual effect of solvent structure and interface adsorption regulation, a high Coulombic efficiency of 99.83 % can be achieved for the Zn//Cu half cell in an electrolyte containing a small amount of MA, and an excellent lifetime of beyond 4000 h can be achieved in a Zn//Zn symmetric cell at 5 mA cm −2 and 1 mAh cm −2 . Even under deep plating/stripping conditions (5 mA cm −2 and 5 mAh cm −2 ), it is still capable of stabling operation for 600 h. In addition, the Zn//V 2 O 5 full cell with MA also exhibited higher capacity and better rate performance. The incorporation of MA improves the electrochemical performance of zinc ion batteries to a great extent relative to the pure ZnSO 4 electrolyte.