Unveiling the Structural Evolution of Ag1.2Mn8O16 under Coulombically Controlled (De)Lithiation

Jianping Huang, Xiaobing Hu, Alexander B. Brady, Lijun Wu, Yimei Zhu, Esther S. Takeuchi*, Amy C. Marschilok, Kenneth J. Takeuchi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


MnO2 materials are considered promising cathode materials for rechargeable lithium, sodium, and magnesium batteries due to their earth abundance and environmental friendliness. One polymorph of MnO2, α-MnO2, has 2 × 2 tunnels (4.6 Å × 4.6 Å) in its structural framework, which provide facile diffusion pathways for guest ions. In this work, a silver-ion-containing α-MnO2 (Ag1.2Mn8O16) is examined as a candidate cathode material for Li based batteries. Electrochemical stability of Ag1.2Mn8O16 is investigated through Coulombically controlled reduction under 2 or 4 molar electron equivalents (e.e.). Terminal discharge voltage remains almost constant under 2 e.e. of cycling, whereas it continuously decreases under repetitive reduction by 4 e.e. Thus, detailed structural analyses were utilized to investigate the structural evolution upon lithiation. Significant increases in lattice a (17.7%) and atomic distances (∼4.8%) are observed when x in LixAg1.2Mn8O16 is >4. Ag metal forms at this level of lithiation concomitant with a large structural distortion to the Mn-O framework. In contrast, lattice a only expands by 2.2% and Mn-O/Mn-Mn distances show minor changes (∼1.4%) at x < 2. The structural deformation (tunnel breakage) at x > 4 inhibits the recovery of the original structure, leading to poor cycle stability at high lithiation levels. This report establishes the correlation among local structure changes, amorphization processes, formation of Ag0, and long-term cycle stability for this silver-containing α-MnO2 type material at both low and high lithiation levels.

Original languageEnglish (US)
Pages (from-to)366-375
Number of pages10
JournalChemistry of Materials
Issue number2
StatePublished - Jan 23 2018

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry


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