Heterolayered Li +-MnO 2-[Mn 1/3Co 1/3Ni 1/3]O 2 nanocomposites with improved electrode functionality: Effects of heat treatment and layer doping on the electrode performance of reassembled lithium manganate

Kyung Min Lee, Yu Ri Lee, In Young Kim, Tae Woo Kim, Song Yi Han, Seong Ju Hwang

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Novel heterolayered nanocomposites consisting of interstratified MnO 2 and [Mn 1/3Co 1/3Ni 1/3]O 2 nanosheets are synthesized by a layer-by-layer self-assembly between negatively charged metal oxide nanosheets and lithium cations. According to powder X-ray diffraction and micro-Raman analysis, all of the as-prepared Li +-xMnO 2-(1-x)[Mn 1/3Co 1/3Ni 1/3]O 2 nanocomposites with x = 1, 0.7, and 0.4 have a lamella structure with similar basal spacing of ∼ 7.1 Å, indicating the formation of lithium intercalation structure with cointercalated water bilayers. The nanoscale mixing of MnO 2 and [Mn 1/3Co 1/3Ni 1/3]O 2 nanosheets is confirmed by energy-dispersive spectrometry-elemental mapping analysis. Upon a self-assembly with Li + ions, there occur no marked changes in the octahedral symmetry and mixed oxidation state of M 3+/M 4+ ions (M = Mn, Co, and Ni) in the precursor metal oxide nanosheets. All of the as-prepared nanocomposites commonly experience a structural transformation from hydrated layered structure to dehydrated layered structure at 200 °C, which is followed by the second-phase transition to cubic spinel structure at 600 °C. Despite distinct structural changes of the nanocomposites at elevated temperatures, their porous stacking structure is well-maintained up to 400 °C. The heat-treatment at 400 °C leads to a significant improvement of the discharge capacity of the present nanocomposites because of the dehydration of as-prepared materials and the enhancement of crystallinity. The doping of [Mn 1/3Co 1/3Ni 1/3]O 2 layers enables us not only to increase the discharge capacity of the Li-MnO 2 nanocomposite but also to prevent the phase transition of layered manganese oxide to spinel structure during electrochemical cycling. The present study clearly demonstrates that a postcalcination process as well as a partial doping of [Mn 1/3Co 1/3Ni 1/3]O 2 layer is effective in improving the electrode performance of reassembled Li-MnO 2 nanocomposites.

Original languageEnglish
Pages (from-to)3311-3319
Number of pages9
JournalJournal of Physical Chemistry C
Volume116
Issue number5
DOIs
Publication statusPublished - 2012 Feb 9

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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