Modulating the solvation structure and electrode interface through phosphate additive for highly reversible zinc metal anode

Aqueous zinc-ion batteries (ZIBs) are considered one of the ideal battery systems for large-scale energy storage. However, ZIBs usually show a limited cycle life due to side reactions and dendrite growth at Zn anode. In this study, an ultra-trace amount of beta-glycerophosphate sodium (beta-GADS) was employed as an additive in aqueous electrolyte to enable highly reversible Zn plating/stripping. For the first time, we show that the phosphate groups in beta-GADS could participate in the cation solvation structure, which is more favorable for the de-solvation and diffusion of Zn2+. Moreover, phosphate can absorb on the surface of Zn, and Na+ tend to accumulate at the surface protrusions to form an electrostatic shield that prevent formation of dendrites. Benefitting from the triply synergistic effects of the beta-GADS additive, the Zn anode shows the inhibition of dendrites, hydrogen evolution reaction, corrosion reactions, and the formation of by-products. Operated based on 2 M ZnSO4 electrolyte with beta-GADS additive, Zn||Zn symmetric cells demonstrated stable cycling for over 1,900 h at 0.5 mA cm-2 and over 1,200 h at a high current density of 5 mA cm-2. The Zn||(NH4)2V7O16 & sdot;3.2H2O full cell with the above electrolyte also delivered a high capacity and excellent stability for over 1,000 cycles.