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Mildly-acid MnO2-Zn batteries have been considered as a promising alternative for large scale energy storage systems for their low toxicity, high safety, and low cost. Despite receiving much research attention, the charge-discharge mechanism remains unclear, and formation of inactive phases still hinders the further development of the batteries. In this study, we clarify that the co-precipitation of Zn and Mn during the charge process is the main cause of the formation of inactive Zn-Mn-O phases in MnO2 which leads to capacity fading upon cycling. Our results show that the addition of TiOSO4 as a facile electrolyte additive suppresses the emergence of the inactive phases by forming a Ti-doped MnO2 during cycling, thereby improving the cycling stability of the electrode. As a result, under a current of 1200 mA g-1, the MnO2 electrode still gives a capacity of 230 mAh g-1 for over 1500 cycles. Capacity retention is 80% after 6000 cycles under a current rate of 3600 mA g-1, while it is 75% after 10000 cycles under a current rate of 4800 mA g-1. These findings provide fundamental insights on the degradation mechanism of MnO2 and a new strategy to improve the electrochemical performance of aqueous MnO2-Zn batteries.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: aqueous zinc-ion batteries, manganese dioxide, electrolyte additive, phase formation

Date published: 2024-07-17

Publisher: Wiley

Journal:

• Small (ISSN: 16136810) 2404368

Funding:

• University Grants Committee PJ9229008

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/smll.202404368

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Updated at: 2024-09-18 16:30:20 +0900

Published on MDR: 2024-09-18 16:30:20 +0900