Outer Sphere Electron Transfer Enabling High-Voltage Aqueous Electrolytes

Fan Zhang; Ting Liao; Hong Peng; Shibo Xi; Dong-Chen Qi; Aaron Micallef; Cheng Yan; Lei Jiang; Ziqi Sun

doi:10.1021/jacs.4c01188

Outer Sphere Electron Transfer Enabling High-Voltage Aqueous Electrolytes

J Am Chem Soc. 2024 Apr 17;146(15):10812-10821. doi: 10.1021/jacs.4c01188. Epub 2024 Mar 11.

Authors

Fan Zhang¹, Ting Liao^{2

3}, Hong Peng⁴, Shibo Xi⁵, Dong-Chen Qi^{1

3}, Aaron Micallef^{3

6}, Cheng Yan^{2

3}, Lei Jiang⁷, Ziqi Sun^{1

3}

Affiliations

¹ School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane 4000, Queensland, Australia.
² School of Mechanical Medical and Process Engineering, Queensland University of Technology, 2 George Street, Brisbane 4000, Queensland, Australia.
³ Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane 4000, Australia.
⁴ School of Chemical Engineering, The University of Queensland, Brisbane 4072, Queensland, Australia.
⁵ Institute of Chemical and Engineering Sciences, A*STAR, 1 Pesek Road, Singapore 627833, Singapore.
⁶ Central Analytical Research Facility, Queensland University of Technology, 2 George Street, Brisbane 4000, Queensland, Australia.
⁷ Key Laboratory of Bio-Inspired Materials and Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.

PMID: 38466658
DOI: 10.1021/jacs.4c01188

Abstract

Aqueous electrolytes with a low voltage window (1.23 V) and prone side reactions, such as hydrogen evolution reaction and cathode dissolution, compromise the advantages of high safety and low cost of aqueous metal-ion batteries. Herein, introducing catechol (CAT) into the aqueous electrolyte, an outer sphere electron transfer mechanism is initiated to inhibit the water reactivity, achieving an electrochemical window of 3.24 V. In a typical Zn-ion battery, the outer sphere electrons jump from CAT to Zn²⁺-H₂O at a geometrically favorable situation and between the solvation molecules without breaking or forming chemical bonds as that of the inner sphere electron transfers. The excited state π-π stacking further leads to the outer sphere electron transfer occurring at the electrolyte/electrode interface. This high-voltage electrolyte allows achieving an operating voltage two times higher than that of the usual aqueous electrolytes and provides almost the highest energy density and power density for the V₂O₅-based aqueous Zn-ion full batteries. The Zn//Zn symmetric battery delivers a 4000 h lifespan, and the Zn//V₂O₅ full battery achieves a ∼380 W h kg^-1 energy density and a 92% capacity retention after 3000 cycles at 1 A g^-1 and a 2.4 V output voltage. This outer sphere electron transfer strategy paves the way for designing high-voltage aqueous electrolytes.