Fast Ion-Conducting Hybrid Membrane for Lithium-Air Batteries
In order to meet the demand of renewable sources for high energy density, rechargeable Lithium-air batteries are currently being investigated as they promise extremely high specific energy. With Lithium-air batteries possibly powering electronics, sensors, and electric vehicles, the market is expected to enjoy an 11% CAGR between 2018 and 2024.
Compared to organic Lithium-air batteries, Lithium-air batteries with aqueous catholytes have a higher potential to reach theoretical limits in practical devices. A fast ion-conducting membrane is the key component of an aqueous Lithium-air battery, as it protects the lithium anode from reacting chemically with the catholyte solution. Various oxide and sulfide-based fast-ion conducting solid electrolytes including NASICON-type and garnet-type ceramics have been explored but they are generally difficult and costly to prepare for large-scale energy storage systems. Their brittleness also poses a major safety hazard. Organic polymers, on the other hand, are easy and cheap to prepare but have yet to demonstrate a suitable combination of high mechanical as well as electrochemical stability with fast Lithium ion conductivity.
This invention reveals a fast Lithium ion-conducting, lightweight and flexible hybrid inorganic-organic membrane that combines the fast-ionic conductivity, electrochemical and mechanical stability of ceramics with the fundamental advantages of organic compounds — they are more easily scalable and mouldable into desired shapes and sizes. This hybrid approach not only prevents dendrite formation by Lithium ions, which is a major limitation in current membrane technology, it also surpasses earlier attempts at hybrid membranes. Instead of polymer components that tend to react with the catholyte solution, this invention utilises a NASICON-type ceramic filler within a polymer blend.
A major novelty of this approach is how it exploits the advantages of each composite material. It combines the outstanding binding efficiency, adhesion to a large number of surfaces, and high toughness of ceramic fillers with the flexibility of resins. The resins used in this invention have never been explored as lithium ion conducting membranes as they are unable to reach suitable levels of ionic conductivity on their own.