Making batteries function with zero external pressure

UC San Diego Laboratory for Energy Storage and Conversion / Diyi Cheng

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A team of battery researchers led by the University of California San Diego and the University of Chicago has engineered a material called lithium phosphorus oxynitride (LiPON) that, in functional battery tests, has been found to promote a uniformly dense lithium metal electrochemical deposition under zero external pressure.

This is according to a press release by the institutions published on Thursday.

“LiPON is a thin-film solid-state electrolyte that conducts lithium ions and shows strong promise for pairing with a broad range of electrode materials for the lithium battery industry of the future. However, existing methods for producing LiPON have prevented researchers from fully understanding the material. Now, the team found a way to produce this promising solid-state electrolyte in a free-standing form that allows LiPON to be studied more comprehensively,” noted the press statement.

“The new approach to making LiPON has also opened the door to using this solid-state electrolyte to enable lithium metal solid-state batteries that could work under minimal external pressure.”

The scientists also conceived a new methodology for producing LiPON film in a free-standing form by creating a flexible and transparent free-standing LiPON (FS-LiPON) film compatible with a broad range of spectroscopic techniques. This method yielded fresh insights, thermal properties, and mechanical properties.

The research team also implemented the new free-standing version of the solid-state electrolyte in functional battery tests, reporting that the thin-film FS-LiPON promotes a uniformly dense lithium metal electrochemical deposition under zero external pressure. This result offers valuable hints regarding interface engineering in bulk solid-state batteries.

LiPON-based thin film batteries have many applications in various fields, such as wearables and other compact electronic devices with a gigantic market. “The FS-LiPON film produced in this work enabled in-depth discussions on interfacial chemistry, ion diffusion and interface engineering, which shed light on both the fundamentals and applications of LiPON materials, and could benefit the lithium solid-state battery development in many ways,” noted the press statement in its conclusion.

This work was published in the journal Nature Nanotechnology on Thursday.

Study abstract:

Lithium phosphorus oxynitride (LiPON) is an amorphous solid electrolyte that has been extensively studied over the last three decades. Despite the promise of pairing it with various electrode materials, LiPON’s rigidity and air sensitivity set limitations to understanding its intrinsic properties. Here we report a methodology to synthesize LiPON in a free-standing form that manifests remarkable flexibility and a Young’s modulus of ∼33 GPa. We use solid-state nuclear magnetic resonance and differential scanning calorimetry to quantitatively reveal the chemistry of the Li/LiPON interface and the presence of a well-defined LiPON glass-transition temperature of 207 °C. Combining interfacial stress and a gold seeding layer, our free-standing LiPON shows a uniformly dense deposition of lithium metal without the aid of external pressure. This free-standing LiPON film offers opportunities to study fundamental properties of LiPON for interface engineering for solid-state batteries.