In-situ construction of a hydroxide-based solid electrolyte interphase for robust zinc anodes

Abstract

A robust and Zn 2+ -conducting interphase composed of zinc hydroxide sulfate hydrate on Zn has been built in-situ by introducing SO 4 2- additives (e.g., ZnSO 4 or Na 2 SO 4 salt) into a non-concentrated aqueous electrolyte (i.e., 2 M zinc trifluoromethanesulfonate (Zn(OTF) 2 )), which significantly improves the reversibility and stability of Zn anodes by suppressing the continuous hydrogen evolution and guiding the homogeneous Zn 2+ deposition. • A robust SEI on Zn has been in-situ constructed by electrolyte design. • The hydroxide-based SEI suppresses the interfacial side-reactions on Zn anode. • The SEI-protective Zn anode achieves high reversibility and stability. • The Zn//V 2 O 5 · n H 2 O battery exhibits long lifespan and high capacity. Zinc (Zn) metal anode in conventional aqueous electrolytes suffers from water-induced side reactions (hydrogen evolution reaction (HER) and corrosion) and dendrite growth due to the absence of a reliable solid electrolyte interphase (SEI) layer. Here, a robust and Zn 2+ -conducting SEI composed of zinc hydroxide sulfate hydrate (ZHS) on Zn has been built in-situ by introducing SO 4 2- additives (e.g., ZnSO 4 or Na 2 SO 4 salt) into a non-concentrated aqueous electrolyte (i.e., 2 M zinc trifluoromethanesulfonate (Zn(OTF) 2 )). Comprehensive characterizations demonstrate that the in-situ formation of SEI with compact structure is induced by a self-terminated chemical reaction of SO 4 2- with Zn 2+ and OH – (stemming from HER) during the initial cycles, which in-turn terminates the continuous HER and Zn corrosion by isolating Zn from the bulk electrolyte and simultaneously allows a homogeneous Zn 2+ diffusion. As a result, the in-situ formed SEI enables a high reversibility of Zn//Cu cell (99.8% Coulombic efficiency over 600 cycles at 1.0 mA cm −2 ) and an unprecedented cycling life of Zn//Zn cell (over 2000 h at 1.0 mA cm −2 ), and contributes to a stable operation of Zn//V 2 O 5 · n H 2 O full battery. This work will guide the interface engineering to build reliable SEI on metal anodes for aqueous batteries.