Defect structure of Li-doped BPO4: A nanostructured ceramic electrolyte for Li-ion batteries

In this paper the defect chemistry: of Li-doped BPO4 (BPO4-xLi(2)O, 0 less than or equal to x less than or equal to 0.1) is studied. This nanostructur ed ceramic electrolyte is used in all-solid-state Li-ion batteries. By chan ging the Li-doping level the influence on the crystal structure is studied and related to the properties of the material. X-ray diffraction, Fourier-t ransformed infra-red spectroscopy (FTIR), P-31, B-11, and Li-7 magic-angle- spinning solid state nuclear magnetic resonance, neutron diffraction, and i nductively coupled plasma optical-emission spectroscopy measurements are us ed in order to study the structure. The electrical properties are studied w ith AC-impedance spectroscopy (AC-IS). The experimental data show that the defect structure of Li-doped BPO4, can be described with two defect models, Li "(B)+2Li(i)(.) and V'''(B)+3Li(i)(.), suggesting that the ionic conduct ivity takes place,ia interstitial Li ions. (C) 1999 Academic Press.