Halogen-Bond Chemistry-Rectified Hypervalent Tellurium Redox Kinetics towards High-Energy Zn Batteries

Abstract

Hypervalent Te redox (Te0/Te4+) in ionic liquid electrolytes (ILEs) is promising for energetic Zn batteries. However, the energy contribution of Te0/Te4+ is only one-third of the total redox-amphoteric conversion, which entails the contribution maximization for energy upgradation. The underlying kinetics-limited factor is vital but usually overlooked in previous explorations. Herein, we unlock a halogen-bond chemistry-rectified Te0/Te4+ redox with an almost maximized contribution for 700-Wh kgTe-1 Zn batteries. The Zn-X bond barriers in ZnX42- (X = Cl, Br) species from ILEs play crucial roles in rectifying the Te0/Te4+ redox kinetics, especially in localized concentrated ILEs, resulting in sharply different redox conversion depth. When the ZnBr42- with weak Zn-Br bond (34.96 kcal mol-1) as the activator, the Te0/Te4+ redox contribution can be maximized to ~90.0% over 5000 cycles at 5 A g-1, 1.8-fold higher than that with ZnCl42- activator via strong Zn-Cl bond (102.81 kcal mol-1), surpassing those in most aqueous systems (ca. 33.0%). This work decodes halogen-bond chemistry-rectified kinetics to maximize hypervalent redox contribution towards high-energy Zn batteries, which could apply to other chalcogen conversion batteries.