Realizing high reversibility and safety of Zn anode via binary mixture of organic solvents

Abstract

The conventional aqueous electrolyte in Zn batteries often induces a chain of interconnected marvels including dendrites, passivation and hydrogen evolution leading to catastrophic battery failures. Herein, we propose a new organic electrolyte comprising of mixed solvents {trimethyl phosphate (TMP), N-methyl formamide (NMF)} and Zn(OTf)2 salt, which not only enables highly reversible and dendrite-free Zn anode but ensures excellent non-flammability endorsing battery safety. The enhanced electrolyte-electrode (Zn) interactions and changes in solvation structure of electrolyte due to NMF incorporation in TMP, assisted uniform Zn deposition free from dendrites. Consequently, Zn anode exhibited long cycling of over 1200 h at high current densities of 3.0 and 5.0 mA cm−2 with high average Coulombic efficiency (CE）99.83% and affords promising areal capacity of 20.0 mAh cm−2. Much stronger TMPNMF-Zn2+ and NMF-Zn surface interactions revealed by molecular simulations provided insights to the beneficial role of NMF as co-solvent in stabilizing Zn anode. Moreover, Zn/NaV3O8 full battery delivered remarkable capacity retention and cycling stability in TMPNMF electrolyte. The present research work proposes promising route for designing new electrolyte systems for sustainable and safe non-aqueous Zn batteries.