A High Energy Density Aqueous Battery Achieved by Dual Dissolution/Deposition Reactions Separated in Acid‐Alkaline Electrolyte

Abstract

Aqueous batteries are facing big challenges in the context of low working voltages and energy density, which are dictated by the narrow electrochemical window of aqueous electrolytes and low specific capacities of traditional intercalation‐type electrodes, even though they usually represent high safety, low cost, and simple maintenance. For the first time, this work demonstrates a record high‐energy‐density (1503 Wh kg−1 calculated from the cathode active material) aqueous battery system that derives from a novel electrolyte design to expand the electrochemical window of electrolyte to 3 V and two high‐specific‐capacity electrode reactions. An acid‐alkaline dual electrolyte separated by an ion‐selective membrane enables two dissolution/deposition electrode redox reactions of MnO2/Mn2+ and Zn/Zn(OH)42− with theoretical specific capacities of 616 and 820 mAh g−1, respectively. The newly proposed Zn–Mn2+ aqueous battery shows a high Coulombic efficiency of 98.4% and cycling stability of 97.5% of discharge capacity retention for 1500 cycles. Furthermore, in the flow battery based on Zn–Mn2+ pairs, more excellent stability of 99.5% of discharge capacity retention for 6000 cycles is achieved due to greatly improved reversibility of the Zn anode. This work provides a new path for the development of novel aqueous batteries with high voltage and energy density.

2020 Roadmap on Zinc Metal Batteries

“…This aqueous ZnÀ MnO 2 battery with hybrid electrolyte exhibits a high average voltage of 1.7 V due to the lower redox potential of the Zn anode in the alkaline electrolyte. Similarly, Liu et al reported that the electrochemical window of the ZnÀ MnO 2 battery with the alkaline anolyte and the acidic catholyte was broadened to 3 V owing to the high overpotentials of gas evolution in alkaline/acidic conditions, and this battery can output a high voltage of 2.44 V. [18] And a novel bication electrolyte (1 M Al (CF 3 SO 3 ) 3 + 1 M Zn(CF 3 SO 3 ) 2 ) was employed in aqueous ZnÀ MnO 2 batteries to adjust the intermediate species upon charging/discharging, which is intensively associated with voltage, and fianally a high discharge voltage of 1.7 V was obtained due to the formation of the unique Al x MnO 2 species, accompanied with the expansion of the operation voltage window from 1.5 to 1.9 V owing to the suppression of gas evolution by the Al(CF 3 SO 3 ) 3 component. [19] In order to improve the reaction kinetics and structural stability of MnO 2 cathode, clever designs of composite structure are proposed with the aim to provide highly conductive network, more active sites for charge storage, void space to accommodate the volumetric change and/or self-adhesive configuration forming a free-standing electrode.…”

Latest Advances in High-Voltage and High-Energy-Density Aqueous Rechargeable Batteries

“…The assembled battery possesses an average discharge voltage plateau of 1.7 V and energy density of 487 Wh kg −1 [92]. In addition, by combining the two dissolution/deposition electrode redox reactions of MnO 2 /Mn 2+ and Zn/Zn(OH) 4 2− using acid-alkaline dual electrolytes and an ion-selective membrane, a high-energy Zn-MnO 2 battery was constructed [93]. The working mechanism is illustrated in Fig.…”

“…b The principle diagram and the mech-anism of the Zn-MnO 2 battery using the acid-base dual electrolyte under charge and discharge conditions. [93] Reproduced with permission from Ref. [93].…”

“…[93] Reproduced with permission from Ref. [93]. Copyright 2020, Wiley-VCH that of Na 3 V 2 (PO 4 ) 3 [104].…”

Rechargeable Aqueous Zinc‐Ion Batteries with Mild Electrolytes: A Comprehensive Review

“…Therefore, Zhou and Liang et al [31] further proposed a dissolution/deposition mechanism for the Zn 2 + storage ability of MnO 2 in mild electrolytes, which believe that dissolution/deposition reactions are the major attributor to the capacity. The discharge side product ZnSO 4 [58][59][60][61] However, a low pH volume will remarkably accelerate the corrosion of Zn anodes and deteriorate the cycling stability of ZIBs. [21] Commonly, the pH of mild ZIBs' electrolytes is higher than 3.…”