- Researchers develop a mechanically and chemically stable interface that can increase lithium metal battery life without raising safety concerns.
- This superthin interface (10 nm) is made of boron nitride.
We are becoming more reliant on batteries for everything from electric cars to portable equipment. Thus, scientists are exploring ways to make these energy sources more safe and stable while increasing their life.
Almost all current devices are powered by lithium-ion batteries, which contain low energy density and highly flammable liquid electrolyte. These factors result in shorter battery life and there is always major safety concerns associated with such energy sources.
Now, researchers at Columbia University have figured out a new way of building long-lasting battery by integrating a nano-coating of boron nitride to stabilize solid electrolytes in lithium metal batteries.
Solid-State Lithium Batteries
One can enhance the energy density by replacing the battery graphite anode with lithium metal. As per theoretical calculations, it can hold nearly 10x higher charge than that of graphite. However, this replacement also increases the safety concerns: dendrites often form during the lithium plating and they can easily pass through the membrane separator, creating short-circuits in the battery.
In order to improve both energy density and safety, researchers focused on solid, ceramic (non-flammable) electrolytes. More specifically, they decided to go with rechargeable solid-state lithium batteries, which may be used in future energy storage technologies.
Although these solid ceramic electrolytes have impressive mechanical strength, most of them corrode by lithium metal, and thus can’t be used to make lithium batteries.
A Super-Thin Interface
In this work, researchers developed a mechanically and chemically stable protective layer that separates lithium anode and solid electrolytes. In order to transfer electron ions, it’s important to build an interface that is ionically conducting as well as electronically insulating. Also, the interface needs to be as thin as possible so that it doesn’t decrease the battery’s energy density.
To build this interface (protective layer), the team used nanofilm of boron nitride, which is nearly 10 nanometers thick. It isolates the electrical contact between ionic conductor and lithium metal.
Boron nitride electronically isolates Lithium aluminum titanium phosphate (LATP) from lithium, while still providing stable ionic pathways | Courtesy of researchers
The nanofilm has intrinsic defects that allow lithium ion to pass through while serving as a perfect separator. Moreover, boron nitride can be easily prepared by depositing chemical vapor to produce atomically thin, continuous films.
Unlike earlier researches that used thicker layers (up to 200 micrometers thick), the boron nitride film doesn’t reduce the energy density of batteries. According to the researchers, it is an excellent material to work as an isolating barrier between solid electrolyte and lithium metal, as well as for producing long-lasting lithium metal batteries.
The team is now exploring ways to further optimize the interface and extend their technology to various unstable solid electrolytes. The goal is to design solid-state batteries with long-cycle lifetimes and high performance.