Asymmetric acceptor–donor small organic molecule enabling versatile and highly-stable aqueous zinc batteries

Abstract

Aqueous zinc batteries (AZBs) are promising for large-scale energy storage. However, severe side reactions and Zn dendrite growth are challenging. "Water-in-salt" and organic/aqueous hybrid electrolytes address these problems but compromise the high ionic conductivity, superior safety, low cost, and good sustainability. Herein, an asymmetric acceptor–donor small organic molecule (NMU) is proposed to boost Zn anodes without compromising the advantages of AZBs. It is found that NMU molecules alter the H-bonding network and reconstruct Zn2+ solvation sheath. Besides, NMU additives tend to be absorbed on the Zn surface to build a water-poor electrical double layer and can in-situ form a robust solid-electrolyte interphase layer that protects the Zn anode. The Zn (0 0 2) plane can be predominately guided by NMU. Consequently, the lifespan of the Zn||Zn cell using NMU can maintain over 3000 h and the average Coulombic efficiency of the Zn||Cu cell reaches 99.7 % throughout 1800 cycles. Additionally, our strategy can be applied in highly-stable and versatile full cells with MnO2, activated carbon and conversion-type I2 (capacity retention: 92.5 % throughout 10,000 cycles) cathodes under practical electrode ratios. The Zn||I2 pouch cell with NMU also presents good cycling stability over 1100 cycles.