2018-297 – Thin Film Ceramics that Offer Electric and Electrochemical Properties Using Nanopowders of Controlled Compositions

  • Sodium-ion battery
  • β”-Al2O3
  • Nanoparticles


Sodium-ion batteries are promising alternatives to ubiquitous lithium-ion battery technology present in many consumer and industrial products today. Lithium is relatively rare and costly to mine, in terms of both economic and environmental impact, whereas sodium is vastly more abundant and significantly cheaper to obtain. Furthermore, sodium-ion batteries offer the advantage that they can be fully drained without damaging the component materials and offer better resilience in terms of the number of charge cycles they can undergo. For these reasons, sodium-ion battery technology is being actively pursued for potential use in consumer electronic devices and for grid-storage applications paired with renewable energy production. Current limitations in sodium-ion battery technology is that they are significantly heavier than their lithium counterparts and battery designs are severely limited as a result of processes used to manufacture a critical component, beta alumina solid electrolytes.

Beta alumina solid electrolytes are composed of β’’-Al2O3 and regulate the flow of sodium ions within batteries during discharge and charging cycles by providing a rigid framework with passable channels that allow the ions to flow between the battery anode and cathode. The solid electrolytes are already in use in existing sodium ion battery technologies such as the sodium/sulfur battery and sodium nickel chloride battery. Current constraints present in the manufacturing processes for beta alumina require that the final ceramic be thick for mechanical stability. As a result, in most cases rolling the alumina into a tubular shape provides the greatest battery efficiency while accounting for the thicker electrolyte materials, which restricts the battery designs that can be achieved. Advances in component materials and processes for producing β’’-Al2O3, such that thin films are possible, will allow for the development of sodium-ion batteries with novel designs, such as linear formats, that will allow for greater penetration into the consumer and industrial markets.

Nanoparticle component materials and dopants allow for the production of thin β’’-Al2O3 films

The available technology is a method for producing thin films of β’’-Al2O3, which will prove useful in the development of alternative sodium-ion battery designs. This is accomplished through two distinct modifications of the manufacturing process: 1) component materials used to manufacture the final ceramic are first produced as nanoparticles with significantly smaller particle sizes, and 2) a combination of metal oxide dopants are added to the material to improve the manufacturing process and physical properties of the final composite. Preliminary data indicates that the nanoparticles are remarkably homogenous in size, indicating that their production could be readily scaled. More specifically, the metal oxide dopants reduce the temperatures required for sintering the components into a ceramic material and control the final grain size of the ceramic. Using this production methodology, thin films of β’’-Al2O3 that are 20-50 µm thick, with 96-98% of theoretical maximum density, and 60-80 weight percent β’’-Al2O3 have been produced and ionic conductivities were assessed to be 3-5 mS cm-1, indicating that the films have some of the necessary properties for potential application in battery technologies.

Contact Information

Name: Joohee Kim

Email: jooheek@umich.edu

Phone: (734) 647-5730