Lithium diffusion coefficient in amorphous lithium phosphate thin films measured by secondary ion mass spectroscopy with isotope exchange methods

• Published in: Solid state ionics 2016-10, Vol.294, p.59-66
• Main Authors: Kuwata, Naoaki, Lu, Xiaoli, Miyazaki, Takamichi, Iwai, Yoshiki, Tanabe, Tadao, Kawamura, Junichi
• Format: Article
• Language: English
• Subjects: Diffusion coefficient; Haven ratio; Pulsed laser deposition; Thin-film battery
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2016.06.015

Lithium diffusion coefficients in amorphous lithium phosphate (a-Li3PO4) thin films were determined by secondary ion mass spectroscopy (SIMS), using 7Li and 6Li stable isotopes. The diffusion couples were prepared by an ion-exchange method using liquid electrolyte and a mask method based on thin-film deposition. The tracer diffusion coefficient, DLi⁎, was evaluated by analyzing the isotope profiles obtained by SIMS in the temperature range of 25–160°C. The diffusion coefficient of a-Li3PO4 was 6.0×10−13cm2/s at 25°C, while the activation energy was 0.58eV, as measured for the samples prepared by using the ion-exchange method. The conductivity diffusion coefficient, Dσ, was calculated from the thin film ionic conductivity, which was determined by impedance spectroscopy. The correlation factor, HR, was 0.55±0.20 in the measured temperature range, which indicated the cooperative motion of lithium ions in lithium phosphate glasses. •Diffusion coefficients in lithium phosphate thin films were determined.•Secondary ion mass spectroscopy and ion-exchange techniques were employed.•Isotope profiles in the diffusion couples were calculated numerically.•Haven ratio was calculated from the tracer and the conductivity diffusion coefficients.