Dataset of "Mn and Au Redox Mediators in ZnCl₂ Water-in-Salt Electrolytes: Implications for Zn-Ion Battery Chemistry"

Redox mediators in water-in-salt electrolytes (WiSE) offer a compelling platform for durable, safe, and efficient Zn-ion battery. Here we investigate two model systems, i.e., MnCl2 and HAuCl4 dissolved in 15 m ZnCl2. Using a carbon positive electrode enables areal capacities of approx. 1 mAh/cm², outperforming traditional electrodes with solid-state active materials, e.g., phosphate olivines. This capacity is available in a WiSE volume, which fits the standard 2032 coin cell. Stable cycling of Mn-mediated systems requires suppression of permanganate formation above ~2.0 V vs. Zn²⁺/Zn. Once avoided, the Mn electrochemistry becomes simply diffusion-controlled, with ion transport primarily controlled by the viscosity of the WiSE. Remarkably, Au and Mn display strikingly similar electrochemical signatures, each producing broad, asymmetric voltammetric peaks with a formal potential near 1.7 V vs Zn²⁺/Zn, despite Mn redox couples being shifted by ca. 0.7 V below their standard potentials. Gold undergoes rapid oxidative dissolution toward AuCl4- as confirmed by in situ Raman spectroelectrochemistry. Multiple Au-Zn intermetallic phases are identifiable by distinct features at anodic stripping. These findings highlight both the opportunities and mechanistic complexities of liquid-phase redox mediators for high-capacity Zn-ion energy-storage systems with WiSE.