Closo-type complex hydride-derived interphase for stable aqueous zinc metal batteries

Abstract

Aqueous Zn metal batteries hold great promise for large–scale energy storage systems due to their inherent safety and high energy density. However, parasitic side reactions at the Zn metal anode interface, including undesirable electrolyte decomposition and the formation of byproducts, induce unstable Zn deposition, thereby accelerating performance degradation. In this study, we propose a closo–type complex hydride as an electrolyte additive that stabilizes the Zn metal anode by regulating the interfacial reactions. The closo–type complex hydride, Zn(B12H12), dissociates into Zn2+ and [B12H12]2−, and the resulting [B12H12]2− complex hydride anions interact only weakly with surrounding species without significantly altering the bulk electrolyte structure. Such weak coordination behavior allows [B12H12]2− to remain available for interfacial reactions at the Zn metal surface, contributing to the formation of a hydride−rich interphase containing reducing B-H bondings. This interphase suppresses ZnO formation and parasitic reactions while promoting uniform Zn nucleation and compact Zn growth at the electrode surface, thereby enabling homogeneous Zn deposition during repeated cycling. Consequently, Zn||V2O5 batteries maintain superior cycling stability over 5000 cycles at a high rate of 10 A g−1. This study highlights the potential of complex hydrides as electrolyte additives and their broader applicability in regulating metal−electrolyte interfacial reactions for stable aqueous metal batteries. © 2026 The Authors