Controlling intermolecular interaction and interphase chemistry enabled highly stable aqueous ammonium-ion batteries

Abstract

Aqueous ammonium-ion batteries (AIBs) show great potential in the large scale energy storage systems due to the advantages of low cost, high safety and environmental friendliness. However, they face the challenges of low output voltage and unsatisfactory electrochemical performance because of the narrow voltage window and unstable interfacial structure in conventional aqueous electrolytes. Herein, we design an aqueous AIB based on hydrogen-bond anchored electrolyte, Mn-based Prussian blue analogues (MnHCF) cathode and NaTi2(PO4)3@carbon (NTP@C) anode. In this electrolyte, the intermolecular hydrogen-bond interaction is constructed between water and sulfolane molecules, leading to the decreased water activity and wide voltage window. Furthermore, the coordination environment of NH4+ ions between sulfolane and CF3SO3- anions produces a unique solvation structure with low hydrated degree, which favors the formation of protective interfacial layer between electrode and electrolyte. Accordingly, the dissolution of MnHCF is largely inhibited and the side reactions between electrode and electrolyte are suppressed. As a result, the MnHCF electrode displays stable cycling performance and high Coulombic efficiency compared with the cases in conventional aqueous electrolytes. Moreover, the constructed full cells demonstrate high output voltage and superior stability. This work provides a synergistic route to design high-performance aqueous AIBs.