Atomic Layer Deposition of Sodium Phosphorus Oxynitride: A Conformal Solid-State Sodium-Ion Conductor

R Blake Nuwayhid; Angelique Jarry; Gary W Rubloff; Keith E Gregorczyk

doi:10.1021/acsami.0c03578

Atomic Layer Deposition of Sodium Phosphorus Oxynitride: A Conformal Solid-State Sodium-Ion Conductor

ACS Appl Mater Interfaces. 2020 May 13;12(19):21641-21650. doi: 10.1021/acsami.0c03578. Epub 2020 May 1.

Authors

R Blake Nuwayhid¹, Angelique Jarry¹, Gary W Rubloff^{1

2}, Keith E Gregorczyk¹

Affiliations

¹ Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States.
² Institute for Systems Research and the Institute for Research in Electronics and Applied Physics, University of Maryland, Collage Park, Maryland 20742, United States.

PMID: 32315520
DOI: 10.1021/acsami.0c03578

Abstract

The development of novel materials that are compatible with nanostructured architectures is required to meet the demands of next-generation energy-storage technologies. Atomic layer deposition (ALD) allows for the precise synthesis of new materials that can conformally coat complex 3D structures. In this work, we demonstrate a thermal ALD process for sodium phosphorus oxynitride (NaPON), a thin-film solid-state electrolyte (SSE), for sodium-ion batteries (SIBs). NaPON is analogous to the commonly used lithium phosphorus oxynitride SSE in lithium-ion batteries. The ALD process produces a conformal film with a stoichiometry of Na₄PO₃N, corresponding to a sodium polyphosphazene structure. The electrochemical properties of NaPON are characterized to evaluate its potential in SIBs. The NaPON film exhibited a high ionic conductivity of 1.0 × 10^-7 S/cm at 25 °C and up to 2.5 × 10^-6 S/cm at 80 °C, with an activation energy of 0.53 eV. In addition, the ionic conductivity is comparable and even higher than the ionic conductivities of ALD-fabricated Li⁺ conductors. This promising result makes NaPON a viable SSE or passivation layer in solid-state SIBs.

Keywords: atomic layer deposition; energy storage; sodium-ion batteries; sodium-ion conductors; solid-state batteries; solid-state electrolytes; solid-state sodium-ion batteries; thin-film batteries; thin-film electrolytes.