Hetero‐Solvation‐Diluted Strongly‐Coordinated Zn2+‐Cosolvent Pairs Downshifting Zn Electrode Potential for High‐Voltage Hybrid Batteries

Abstract

AbstractMild aqueous Zn batteries (AZBs) generally suffer a low‐voltage/energy dilemma, which compromises their competitiveness for large‐scale energy storage. Pushing Zn anode potential downshift is an admissible yet underappreciated approach for high‐voltage/energy AZBs. Herein, with a mild hybrid electrolyte containing in situ‐derived diluted strongly‐coordinated Zn2+‐cosolvent pairs, a considerable Zn anode potential downshift is initially achieved for high‐voltage Zn‐based hybrid batteries. The chosen butylpyridine cosolvent not only strongly coordinates Zn2+ ions but also acts as a hydrogen‐bond end‐capping agent to inhibit hydrogen evolution reaction (HER). The electrolyte environment with hetero‐solvation‐diluted strongly‐coordinated Zn2+‐cosolvent pairs remarkably lowers Zn2+ activity, responsible for the Zn electrode potential downshift (−0.330 V vs Zn), confirming to modified Nernst law (ΔE = ln[a(Zn2 + )/a(coordinated solvent)]). With the diluted Zn2+‐containing hybrid electrolyte, the Zn//Zn symmetric cell in the hybrid electrolyte shows a long lifespan over 1270 h at a stripping/plating capacity of 0.4 mA h cm−2. Compared with in common hybrid electrolytes, the as‐assembled Zn‐MnO2 hybrid battery delivers a ca. 0.278 V enhanced voltage plateau (1.57 V) and a long‐term cyclability of over 736 cycles. This work opens a new avenue toward Zn anode potential downshift for high‐voltage AZBs, which can extend to other mild metal batteries.