Lithium ion conductivity of LiPN2 and Li7PN4

Single phase lithium phosphorus nitrides Li7NP2 and LiN P2 were prepared by reaction of the binary nitrides P3N5 and Li3N at 620 and 800°C, respectively. The compounds were identified by X-ray powder diffraction techniques. The lithium ion conductivity of both compounds was investigated by complex impedance spectroscopy in the temperature range between 50 and 350°C. The specific conductivity was found to be σ(400 K)=1.7×10−5 and 6.9×10−7 ω−1 cm−1 for Li7PN4 and LiPN2, respectively: The activation energy was 46.7 kJ/mol for Li7PN4 and 58.9 kJ/mol for LiPN2.