Direct Proof of the Reversible Dissolution/Deposition of Mn<SUP>2+</SUP>/Mn<SUP>4+</SUP> for Mild-Acid Zn-MnO₂ Batteries with Porous Carbon Interlayers

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Moon, Hyeonseok, Ha, Kwang-Ho, Park, Yuwon, Lee, Jungho, Kwon, Mi-Sook, Lim, Jungwoo ORCID: 0000-0002-4123-2882, Lee, Min-Ho, Kim, Dong-Hyun, Choi, Jin H, Choi, Jeong-Hee et al (show 1 more authors) and Lee, Kyu Tae (2021) Direct Proof of the Reversible Dissolution/Deposition of Mn<SUP>2+</SUP>/Mn<SUP>4+</SUP> for Mild-Acid Zn-MnO₂ Batteries with Porous Carbon Interlayers. ADVANCED SCIENCE, 8 (6). 2003714-.

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Abstract

Mild-acid Zn-MnO₂ batteries have been considered a promising alternative to Li-ion batteries for large scale energy storage systems because of their high safety. There have been remarkable improvements in the electrochemical performance of Zn-MnO₂ batteries, although the reaction mechanism of the MnO₂ cathode is not fully understood and still remains controversial. Herein, the reversible dissolution/deposition (Mn²⁺/Mn⁴⁺) mechanism of the MnO₂ cathode through a 2e^- reaction is directly evidenced using solution-based analyses, including electron spin resonance spectroscopy and the designed electrochemical experiments. Solid MnO₂ (Mn⁴⁺) is reduced into Mn²⁺ (aq) dissolved in the electrolyte during discharge. Mn²⁺ ions are then deposited on the cathode surface in the form of the mixture of the poorly crystalline Zn-containing MnO₂ compounds through two-step reactions during charge. Moreover, the failure mechanism of mild-acid Zn-MnO₂ batteries is elucidated in terms of the loss of electrochemically active Mn²⁺. In this regard, a porous carbon interlayer is introduced to entrap the dissolved Mn²⁺ ions. The carbon interlayer suppresses the loss of Mn²⁺ during cycling, resulting in the excellent electrochemical performance of pouch-type Zn-MnO₂ cells, such as negligible capacity fading over 100 cycles. These findings provide fundamental insights into strategies to improve the electrochemical performance of aqueous Zn-MnO₂ batteries.

Item Type:	Article
Uncontrolled Keywords:	aqueous batteries, mild acid electrolytes, porous carbon interlayers, reaction mechanisms, Zn-MnO2 batteries
Divisions:	Faculty of Science and Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	14 Sep 2022 09:31
Last Modified:	19 Oct 2023 09:07
DOI:	10.1002/advs.202003714
Open Access URL:	https://doi.org/10.1002/advs.202003714
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3164659