In-situ construction of fluorinated solid-electrolyte interphase for highly reversible zinc anodes

Safe and low-cost aqueous zinc batteries offer a promise for energy storage. However, dendrite formation and parasitic reactions of zinc anodes hinder the practical application of this type of battery. In this work, guided by theoretical modeling, we formulate a new low-concentration electrolyte to boost the reversibility and stability of zinc anodes. Molecular dynamics simulations and first principle calculations reveal that adding dimethyl sulf-oxide (DMSO) into a Zn(TFSI)2 electrolyte can effectively introduce TFSI- anions into the solvation sheath of Zn2+, of which the TFSI- anions will be preferably reduced prior to zinc deposition, thus in-situ forming a ZnF2- rich interphase on the zinc surface. It is experimentally verified that the fluorinated interphase regulates the uniform zinc plating and stripping, thus suppressing the dendrite formation, and effectively prevents the zinc anode from side reactions with the electrolyte. As a result, the newly formulated electrolyte leads to highly reversible zinc plating/stripping with an average coulombic efficiency of as high as 98.4% and enables a zinc symmetric cell to achieve a long cycle life of over 2,000 h. More impressively, when the DMSO-modulated electrolyte is applied to full cells, a zinc-polyaniline battery can retain 87.9% of its initial capacity after 2,500 cycles at 2 A g-1, and a zinc-activated carbon hybrid supercapacitor can stably cycle up to 20,000 times at 5 A g-1. This work opens a new avenue for creating desirable solid-electrolyte interphase on the zinc anode via facile electrolyte modulation, paving the way for development of high-performance aqueous zinc batteries.

Automated summary

The study formulates a new low-concentration electrolyte to improve the reversibility and stability of zinc anodes in aqueous zinc batteries. By adding DMSO into the electrolyte, a fluorinated interphase is formed on the zinc surface, suppressing dendrite formation and side reactions. This newly formulated electrolyte enables highly reversible zinc plating/stripping and significantly improves the cycle life of zinc batteries.