Concentrated Chlorine-Based Electrolyte Enabling Reversible Cl₃^–/Cl^– Redox for Energy-Dense and Durable Aqueous Batteries

Abstract

Redox of chlorine with high potential and specific capacity has attracted wide attention for energy storage applications, while it suffers from an undesired disproportionation reaction in aqueous electrolytes which hinders its development. Herein we propose a strategy via a unique solubilization effect of metal-halide complex ions to construct a high concentration of chloride (over 30 m) electrolyte with low cost to stabilize the oxidation products and suppress the side reactions, thus representing a high reversibility of the Cl 3 − /Cl − redox couple up to 96.0% with 1.0 V vs SCE. The as-fabricated Zn−Cl 3 − full cell based on the highly concentrated electrolyte exhibits an ultrahigh operating voltage of 2.02 V at 1.0 mA cm −2 in the nearly neutral system. In particular, an enhanced conversion efficiency at room temperature with durable cycling stability of 4000 cycles is demonstrated. These results open a new way for the development and application of aqueous chlorine-ion batteries.

Reversible Cl/Cl− redox in a spinel Mn3O4 electrode

“…After charging, a broad peak appeared at ∼270 nm by the electrolyte, which is very likely indicative of the [Cl 3 ] − anion. 51,52 To further confirm the existence of the polychloride monoanions formed with the Mn 3 O 4 structure after charging in the 20 M ZnCl 2 + 5 M NH 4 Cl WiSE, we immersed the fully charged Mn 3 O 4 electrode in an aqueous solution of 0.5 M KI. It was observed that the color of the KI solution quickly turned brownish, thereby indicating the presence of the polychloride monoanions as the charge products with the Mn 3 O 4 host (Fig.…”

“…Aer charging, a broad peak appeared at ∼270 nm by the electrolyte, which is very likely indicative of the [Cl 3 ] − anion. 51,52 To further…”