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Investigating the structural change and degradation mechanism of MnO2 for lithium-ion batteries.

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Title: Investigating the structural change and degradation mechanism of MnO2 for lithium-ion batteries.
Authors: Lin, Chia-Ching1 (AUTHOR), Kubota, Kei2 (AUTHOR), Zhao, Yu3 (AUTHOR), Yu, Denis Y.W.1,2 (AUTHOR) yu.denis@nims.go.jp
Source: Journal of Power Sources. Aug2025, Vol. 648, pN.PAG-N.PAG. 1p.
Subjects: Manganese dioxide, Ethylene carbonates, Surface coatings, Lithium-ion batteries, High voltages
Abstract: Tunnel-type manganese dioxide (MnO 2) is widely used as a cathode material for commercial lithium-metal primary batteries due to its low cost, non-toxicity, and high capacity of 308 mAh g−1. However, it has not been used in rechargeable batteries because it showed poor cycle stability in the past. In this study, we systematically investigate the electrochemical behavior of β-MnO 2 as a cathode for lithium-ion batteries, identifying key degradation mechanisms and proposing a surface modification strategy to enhance its performance. Specifically, β-MnO 2 delivers a reversible capacity of approximately 220 mAh g−1 at 30 mA g−1. During first cycle, β-MnO 2 transforms irreversibly to Li x MnO 2 with an orthorhombic phase as shown by in-situ X-ray diffraction, which causes some Li to be trapped in the structure. The emergence of a spinel-like LiMn 2 O 4 phase upon further cycling contributes to capacity fading. The cycle stability of MnO 2 is significantly influenced by the electrolyte composition, with higher capacity fading observed in electrolytes containing larger amount of ethylene carbonate which correlates with increased manganese dissolution. To mitigate these issues, a 2 wt% Li 3 PO 4 surface coating was applied to the β-MnO 2 particles, which improves its capacity retention and Coulombic efficiency, particularly at higher cut-off voltages, by reducing electrolyte decomposition. • A capacity of 230 mAh g−1 is obtained from β-MnO 2. • β-MnO 2 undergoes structural change to spinel-like phase during cycling. • Mn dissolution facilitated by ethylene carbonate in the electrolyte. • Higher Mn loss observed at higher voltage, with larger capacity drop. • Li 3 PO 4 coating improves capacity retention by reducing Mn dissolution. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Tunnel-type manganese dioxide (MnO 2) is widely used as a cathode material for commercial lithium-metal primary batteries due to its low cost, non-toxicity, and high capacity of 308 mAh g−1. However, it has not been used in rechargeable batteries because it showed poor cycle stability in the past. In this study, we systematically investigate the electrochemical behavior of β-MnO 2 as a cathode for lithium-ion batteries, identifying key degradation mechanisms and proposing a surface modification strategy to enhance its performance. Specifically, β-MnO 2 delivers a reversible capacity of approximately 220 mAh g−1 at 30 mA g−1. During first cycle, β-MnO 2 transforms irreversibly to Li x MnO 2 with an orthorhombic phase as shown by in-situ X-ray diffraction, which causes some Li to be trapped in the structure. The emergence of a spinel-like LiMn 2 O 4 phase upon further cycling contributes to capacity fading. The cycle stability of MnO 2 is significantly influenced by the electrolyte composition, with higher capacity fading observed in electrolytes containing larger amount of ethylene carbonate which correlates with increased manganese dissolution. To mitigate these issues, a 2 wt% Li 3 PO 4 surface coating was applied to the β-MnO 2 particles, which improves its capacity retention and Coulombic efficiency, particularly at higher cut-off voltages, by reducing electrolyte decomposition. • A capacity of 230 mAh g−1 is obtained from β-MnO 2. • β-MnO 2 undergoes structural change to spinel-like phase during cycling. • Mn dissolution facilitated by ethylene carbonate in the electrolyte. • Higher Mn loss observed at higher voltage, with larger capacity drop. • Li 3 PO 4 coating improves capacity retention by reducing Mn dissolution. [ABSTRACT FROM AUTHOR]
ISSN:03787753
DOI:10.1016/j.jpowsour.2025.237417