Tracer Diffusion Coefficients of Li Ions in LixMn2O4Thin Films Observed by Isotope Exchange Secondary Ion Mass Spectrometry

Naoaki Kuwata, Gen Hasegawa, Daiki Maeda, Norikazu Ishigaki, Takamichi Miyazaki, Junichi Kawamura

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Tracer diffusion coefficients D∗ of lithium ions in LixMn2O4 (0.2 < x < 1) thin films were measured as a function of the composition x by using secondary ion mass spectrometry. For this purpose, a new "step-isotope-exchange method"was developed to observe the time dependence of the 6Li isotope concentration ratio in the LixMn2O4 film which is in contact with a 6Li-enriched electrolyte to exchange Li+ ions. A steep decrease in D∗ depending on the Li composition was observed for LixMn2O4, with D∗ = 8 × 10-13 cm2 s-1 for x = 0.2 and decreasing to 1.5 × 10-17 cm2 s-1 for x = 1.0 (bulk diffusion coefficient, Db*). This behavior is well explained by a vacancy diffusion model for the α phase on LixMn2O4 (0.77 < x < 1.0). Chemical diffusion coefficients D were also measured in the range of 0.2 < x < 1.0 by an electrochemical method, which was compared with the D∗ to evaluate the effect of thermodynamic factors. The thermodynamic factors and interactions between Li+ ions were found to strongly influence the chemical diffusion coefficient. The tracer diffusion measurements are important to understand the charge-discharge mechanism in the electrodes of lithium-ion batteries.

Original languageEnglish
Pages (from-to)22981-22992
Number of pages12
JournalJournal of Physical Chemistry C
Volume124
Issue number42
DOIs
Publication statusPublished - 2020 Oct 22

ASJC Scopus subject areas

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

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