Preparation of highly ionic conductive lithium phosphorus oxynitride electrolyte particles using the polygonal barrel-plasma treatment method

Herein, lithium phosphorus oxynitride (LiPON) electrolyte particles with high ionic conductivity were prepared using the polygonal barrel-plasma treatment method. Results showed that the ionic conductivity of Li3PO4 (particle size: 77 nm) was improved via the N-2-plasma treatment (treatment time: 60-180 min). The maximum ionic conductivity (8.8 x 10(-6) S cm(-1) at room temperature) was obtained for a treatment time of 90 min, and it approximates that of amorphous LiPON films in literature. X-ray photoelectron spectroscopy of the treated samples (particle size: 29 mu m) revealed the formation of LiPON: the area ratio of triply coordinated nitrogen (P-N < P-2) versus doubly coordinated nitrogen (P-NP) =bonds, which compose LiPON, increased as the treatment time increased to 90 min, and then decreased. The particle surface morphology hardly changed during treatment, whereas the cross-sectional observation showed that at least 320-nm amorphous LiPON layer was formed near the particle surfaces. Based on the LiPON layer thickness, it was found that amorphous LiPON particles can be obtained through N-2-plasma treatment of 77 nm Li3PO4 particles. However, the formed LiPON was partially crystallized under the 120 and 180 min treatments. Thus, a variation in the formation of P-N < P-2 and P-NP= bonds and partial crystallization of the formed amorphous LiPON cause the treatment time dependence of ionic conductivity of the treated samples. (C) 2022 Published by Elsevier B.V.