Nitroxyl radical triggered the construction of a molecular protective layer for achieving durable Zn metal anodes

Abstract

The issues of dendrite growth, hydrogen evolution reaction, and zinc anode corrosion have significantly hindered the widespread implementation of aqueous zinc-ion batteries (AZIBs). Herein, trace amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) additive is introduced into AZIBs to protect the zinc metal anode. Trace amounts of the TEMPO additive with nitroxyl radical can provide fast Zn2+ transport and anode protection ability by forming an adsorbed molecular layer via Zn-O bond. This interface not only provides strong interfacial compatibility and promotes dynamic transport of Zn2+, but also induces deposition of Zn2+ along Zn (002) plane. Additionally, the molecular protective layer significantly inhibits hydrogen evolution reaction (HER) and corrosion. The Zn anodes achieve high Coulombic efficiency of up to 99.75 % and long-term plating/stripping of more than 1400 h at 1 mA cm−2 and 0.5 mAh cm−2. The Zn//Zn symmetric cell can operate continuously for 2500 h at a current density of 1 mA cm−2 and 1 mAh cm−2, and it can still last for nearly 1400 h even when the current density is increased to 5 mA cm−2. Furthermore, the Zn//V2O5 full cell using TEMPO/ZnSO4 electrolyte effectively maintains a maximum capacity retention rate of 53.4 % even after 1500 cycles at 5 A/g. This innovative strategy introduces trace additive with free radicals into the electrolyte, which may help to achieve large-scale, ultra-long-life, and low-cost AZIBs.