First-principles calculations, electrochemical and X-ray absorption studies of Li-Ni-PO 4 surface-treated xLi 2MnO 3· (1-x)LiMO 2 (M = Mn, Ni, Co) electrodes for Li-ion batteries

D. Shin*, Christopher M Wolverton, J. R. Croy, M. Balasubramanian, S. H. Kang, C. M.Lopez Rivera, Michael M. Thackeray

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

It has been previously hypothesized that the enhanced rate capability of Li-Ni-PO 4-treated xLi 2MnO 3(1-x)LiMO 2 positive electrodes (M Mn, Ni, Co) in Li-ion batteries might be associated with a defect Ni-doped Li 3PO 4 surface structure i.e., Li 3-2yNi yPO 4 (0 < y < 1), thereby promoting fast Li-ion conduction at the xLi 2MnO 3(1-x)LiMO 2 particle surface. In this paper, the solubility of divalent metals (Fe, Mn, Ni, Mg) in -Li 3PO 4 is predicted with the first-principles GGAU method in an effort to understand the enhanced rate capability. The predicted solubility (x) is extremely small; this finding is consistent with experimental evidence: 1) X-ray diffraction data obtained from Li-Ni-PO 4-treated xLi 2MnO 3(1-x)LiMO 2 electrodes that show that, after annealing at 550C, a Li 3PO 4-like structure forms as a second phase at the electrode particle surface, and 2) X-ray absorption spectroscopy, which indicate that the nickel ions are accommodated in the transition metal layers of the Li 2MnO 3 component during the annealing process. However, electrochemical studies of Li 3-2yNi yPO 4-treated xLi 2MnO 3(1-x)LiMO 2 electrodes indicate that their rate capability increases as a function of y over the range y 0 (Li 3PO 4) to y = 1 (LiNiPO 4), strongly suggesting that, at some level, the nickel ions play a role in reducing electrochemical impedance and increasing electrode stability at the electrode particle surface.

Original languageEnglish (US)
Pages (from-to)A121-A127
JournalJournal of the Electrochemical Society
Volume159
Issue number2
DOIs
StatePublished - 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

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