Lipon-like Electrolyte Powders Made By Scalable Alternative Processing
Authors: Kercher Andrew Keith , Westover Andrew S , Naguib Michael , Kornbluth Mordechai , Veith Gabriel M. , Dudney Nancy J. 
Published: February 2020

Lithium phosphorus oxynitride (Lipon) is the most prominent example of glassy oxynitride electrolytes, which have demonstrated high ionic conductivities, stability over a wide voltage window, and resistance to Li dendrite formation.1Perhaps the greatest drawback of glassy oxynitride electrolytes is that expensive, high-vacuum deposition techniques have been necessary to produce electrolyte compositions with high ionic conductivity (> ~10-6S/cm). High-vacuum deposition techniques have low deposition rates (1 – 50 nm/min, which is less than 0.07 g/hr for Lipon at lab scale) and have only been successfully demonstrated for use in thin film batteries. Alternative processing routes for producing Lipon-like electrolytes could enable their wider usage as electrolytes and ionically conductive additives in commercially viable lithium metal and lithium-ion batteries.
We have used scalable alternative processing to produce Lipon-like electrolyte nanopowders at a high throughput (5 g/hr at lab scale). This alternative processing method has successfully produced Lipon-like electrolytes that conventional ceramic and glass processing methods have been unable to produce.2,3 The processed powders have a predominantly amorphous structure (x-ray diffraction), a particle size of ~100 nm (SEM), and a Lipon-like composition (energy dispersive x-ray spectroscopy and inductively coupled plasma optical emission spectroscopy). Neutron pair distribution function analysis has been coupled with ab initiomolecular dynamics to verify that the Lipon-like nanopowders have local atomic structures (0 – 20 Å) that are nearly identical to conventionally sputtered Lipon. Impedance spectroscopy was used to measure the ionic conductivity and activation energy of unsintered Lipon-like nanopowder compacts. While interparticle contact resistance likely dominates these values, the unsintered Lipon-like nanopowder compact still demonstrated an ionic conductivity of 5.3 x 10-7S/cm at room temperature.

Acknowledgements

The information, data, and work presented herein was funded by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000775. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy. Electron microscopy experiments were conducted at ORNL’s Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Computing resources were provided by the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Brendan Lewis, Rutuja Samant, Dora Cheung, and Bob Herbeck at Buffalo Manufacturing Works aided in the processing of later batches of Lipon-like material. Special thanks to: Brenda Smith, Chelsea Chen, Dale Hensley, and Robert Sacci at Oak Ridge National Laboratory.

References

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