ALD Enabled Performance Improvements of Li-Ion Batteries with Solid Electrolyte
Authors: Trevey James E , Ingham Kyle Patrick , King David M 
Published: February 2020

This research investigated new materials and improvements to the performance of solid state batteries in order to achieve high performance, but with acute attention to safety and manufacturability. It is widely known that liquid-based lithium-ion batteries maintain inherent safety problems on account of solvent leakage and flammability of liquid electrolytes used in commercial lithium-ion batteries.1,2 Additionally, liquid-electrolyte-containing lithium-ion batteries must be constructed in such a way to account for their inherent danger, requiring excess weight in safety containment materials, which diminishes their overall energy density and adds to manufacturing costs. In contrast to commercialized liquid-electrolyte-based lithium-ion batteries, all-solid-state batteries offer ultimate safety and potential for high energy/power density due to increased packing efficiency in final battery designs with the elimination of unnecessary safety equipment.3,4 Unfortunately current research and development efforts have yet to unveil an all-solid-state battery that can fulfill all metrics for world-wide replacement of liquid-electrolyte based lithium-ion batteries. The key issue blocking commercial-scale deployment of all-solid-state batteries is not a lack of capable bulk materials to construct the batteries; but the interfacial reactions that happen between materials within the battery in contact with one-another that prevent maintained high performance.
All-solid-state secondary batteries employing inorganic solid state electrolytes (SEs) offer a significant, inherent safety advantage over conventional liquid-electrolyte-containing batteries making them highly desirable for next generation energy storage. Key to the ultimate safety of all-solid-state secondary batteries is the SE which functions electrochemically and structurally within the battery. Much effort has gone into developing new SEs with excellent electrochemical characteristics such as high ionic conductivity and high voltage chemical stability, as well as into its structural role as the battery separator. Until recently, commercialization of all-solid-state secondary batteries has not been possible due to low conductivity of the SE as compared to batteries with liquid electrolyte. However, numerous groups have demonstrated SEs with high ionic conductivity on the order of 10-4-10-2 S cm-1 which engenders the opportunity for parallel performance between all-solid-state batteries and conventional batteries. As a final hurdle to realistically enable all-solid-state batteries as a viable, commercializable energy source it is critical to resolve the chemical instability between the SE and bulk electrode materials contained within batteries.
It is now widely accepted that the interfaces of lithium-ion battery (LIB) electrode materials can be highly dynamic in nature, and are the source of performance fade problems as well as safety issues. Atomic Layer Deposition (ALD) has been widely demonstrated as an elegant technique for addressing the shortcomings of battery performance, and has recently being demonstrated as a means for enhancing safety. Here, we will discuss recent advances in ALD coatings applied to battery materials which significantly increase the performance as well as safe handling, production, and use of a final batteries.