“Anions‐in‐Colloid” Hydrated Deep Eutectic Electrolyte for High Reversible Zinc Metal Anodes

Zn metal suffers from severe zinc dendrites, anion‐related side reactions, hydrogen evolution reaction (HER) and narrow electrochemical stable window (ESW). Herein, an“anions‐in‐colloid” hydrated deep eutectic electrolyte (ACDE‐3) is designed to improve the stability of zinc anode. The ACDE‐3 reconfigures the hydrogen‐bond (HB) network and regulates the solvation shell. More importantly, the hydroxyl‐rich β‐cyclodextrins (β‐CDs) in ACDE‐3 self‐assemble into micelles, in which the steric effect between the adjacent β‐CDs restricts the movement of anions. This unique “anions‐in‐colloid” structure enables the eutectic system with a high Zn2+ transference number (tZn2+) of 0.84. Thus, ACDE‐3 inhibits the formation of dendrite, prevents the anion‐involved side reactions, suppresses the HER, and enlarges the ESW to 2.32 V. The Zn//Zn symmetric cell delivers a long lifespan of 900 hours at 0.5 mAh cm−2, and the Zn//Cu half cells have a high average columbic efficiency (ACE) of 97.9% at 0.5 mAh cm−2 with a uniform and compact zinc deposition. When matched with a poly(1,5‐naphthalenediamine) cathode, the full battery with a low negative/positive capacity ratio of 2 can still cycle steadily for 200 cycles at a current density of 1.0 A g–1. Additionally, this electrolyte can operative over a wide temperature range from −40 °C to 40 °C.