Freestanding LiPON: from Fundamental Study to Uniformly Dense Li Metal Deposition Under Zero External Pressure

TL;DR

This study introduces a method to produce freestanding, dense LiPON films that enable detailed analysis of their properties and facilitate uniform lithium metal deposition, advancing solid-state battery research.

Contribution

The paper presents a novel synthesis of flexible, freestanding LiPON with high-quality characterization and demonstrates uniform lithium deposition without external pressure.

Findings

Freestanding LiPON exhibits high flexibility and a Young's modulus of ~33 GPa.

High signal-to-noise ss-NMR and DSC measurements reveal detailed interface bonding and glass transition.

Uniform, dense lithium metal deposition achieved without external pressure.

Abstract

Lithium phosphorus oxynitride (LiPON) is a well-known amorphous thin film solid electrolyte that has been extensively studied in the last three decades. Despite the promises to pair with Li metal anode and various cathode materials, the presence of rigid substrate and LiPONs unique amorphous, air-sensitive nature set limitations to comprehensively understand its intrinsic properties for future development and applications. This work demonstrates a methodology to synthesize LiPON in a freestanding form that exhibits remarkable flexibility and a Young s modulus of ~33 GPa. Solid-state nuclear magnetic resonance (ss-NMR) and differential scanning calorimetry (DSC) results with unprecedented high signal-to-noise ratio could be obtained with such freestanding LiPON (FS-LiPON), revealing the Li-LiPON interface bonding environments quantitatively and a well-defined glass transition temperature for LiPON. Combining interfacial stress and a seeding layer, FS-LiPON demonstrates a uniform and fully dense Li metal deposition without the aid of external pressure. Such a FS-LiPON film offers new opportunities for fundamental study of LiPON material and associated interfaces, and provides perspectives for interface engineering in bulk solid-state battery.