Mechanistic Insight into the Electrochemical Performance of Zn/VO 2 Batteries with an Aqueous ZnSO 4 Electrolyte

Journal article (2019)

Authors

Z. Li RST/Storage of Electrochemical Energy - AS
S. Ganapathy RST/Storage of Electrochemical Energy - AS
Y. Xu ChemE/Materials for Energy Conversion and Storage - AS
Zhou Zhou Student
M. Sarilar RID/TS/Technici Pool
M. Wagemaker RST/Storage of Electrochemical Energy - AS
Research Group
RST/Storage of Electrochemical Energy (AS) (TU Delft)
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Published Date

2019

Language

English

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Faculty

Applied Sciences

Department

RST/Radiation, Science and Technology

Research Group

RST/Storage of Electrochemical Energy

Abstract


Rechargeable aqueous zinc-ion batteries (ZIBs) are promising for cheap stationary energy storage. Challenges for Zn-ion insertion hosts are the large structural changes of the host structure upon Zn-ion insertion and the divalent Zn-ion transport, challenging cycle life and power density respectively. Here a new mechanism is demonstrated for the VO
2
cathode toward proton insertion accompanied by Zn-ion storage through the reversible deposition of Zn
4
(OH)
6
SO
4
·5H
2
O on the cathode surface, supported by operando X-ray diffraction, X-ray photoelectron spectroscopy, neutron activation analysis, and density functional theory simulations. This leads to an initial discharge capacity of 272 mAh g
−1
at a current density of 3.0 A g
−1
, of which 75.5% is maintained after 945 cycles. It is proposed that the competition between proton and Zn-ion insertion in the VO
2
host is determined by the solvation energy of the salt anion and proton insertion energetics, where proton insertion has the advantage of minimal structural distortion leading to a long cycle life. As the discharge kinetics are capacitive for the first half of the process and diffusion limited for the second half, the VO
2
cathode takes the middle road possessing both fast kinetics and high practical capacities revealing a reaction mechanism that provides new perspective for the development of aqueous ZIBs.

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