Bimodal Block Molecule with Ether-Type and Hydroxyl-Type Oxygen Stabilizes Zn Anode in Super-Dilute Electrolyte

Diluted electrolyte promises a further decrease of the battery cost for intrinsically safe aqueous zinc ion batteries (ZIBs). However, the parasitic side reactions between abundant water molecules and Zn metal induce serious dendrite growth and anode corrosion, leading to the rapid failure of the ZIBs. In this work, a conceptual design of a bimodal block molecule that features double types of oxygen into polyethylene glycol is proposed, which serves as an effective bifunctional mixing agent (MA) in the super-dilute electrolyte (approximate to 0.23 m). The ether-type oxygen can effectively modulate the solvation structure of the Zn2+ and break the hydrogen bond network of the electrolyte, thereby inhibiting the H2 production reaction. Furthermore, the terminal hydroxyl-type oxygen shows preferential adsorption on the Zn metal (101) plane, guiding the oriented growth of Zn (002) facets parallel to the Zn metal surface and inhibiting the dendrite growth. Consequently, the Zn||Zn symmetrical cells show highly stable reversibility (1400 h at 1 mA cm-2), and the Zn||V2O5 full cells show exceptional cycling stability for 1500 cycles at 1 A g-1, with a high capacity retention rate of 82%. This work provides an insightful design of super-dilute electrolytes for the stable operation of metal electrodes in aqueous batteries. A bimodal block molecule design of a mixing agent is proposed that features double types of oxygen atoms (ether-type oxygen and terminal hydroxyl-type oxygen) in one organic molecule, which serves different roles in stabilizing the anode in the super-dilute electrolyte (approximate to 0.23 m). The synergy between the two oxygen species boosts the electrochemical performance of ZIBs. image