We've recently been hearing a lot about solid state batteries, which have some definite advantages over their conventional counterparts. Although they're still not quite ready for everyday use, a newly developed butter-like substance could help change that.
Ordinarily, lithium-ion batteries consist of two oppositely charged electrodes (the anode and cathode), which are separated by a liquid electrolyte. Lithium ions travel through that liquid, going back and forth between the two electrodes during the charge and discharge cycles.
Unfortunately, though, such electrolytes tend to be environmentally unfriendly, posing a challenge when batteries are damaged or disposed of. Additionally, they're quite flammable, and can thus ignite within an overheating process known as thermal runaway.
Solid state batteries attempt to address these problems by replacing the liquid electrolyte with an eco-friendly, non-flammable, solid ceramic electrolyte. There's still a problem, though, as the interface between the anode and this material can be chemically unstable, limiting the rate at which ions are able to pass through.
Researchers from Sweden's Chalmers University and China's Xi'an Jiaotong University are attempting to address that shortcoming, with their new interlayer paste.
Similar in texture to "butter from the fridge," the substance gets spread onto the surface of a metal lithium anode, forming a transitional layer between it and the solid electrolyte. It consists of nanoparticles of the electrolyte material – a ceramic called LAGP – along with an ionic liquid (which is salt in a liquid state).
When added to an existing solid state battery, the paste was found to produce a tenfold increase in current density, which is defined as the amount of charge per unit time that flows through a unit area of a chosen cross section.
"This interlayer makes the battery cell significantly more stable, and therefore able to withstand much higher current density," says Chalmers researcher Shizhao Xiong. "What is also important is that it is very easy to apply the soft mass onto the lithium metal anode in the battery – like spreading butter on a sandwich."
A paper on the study was recently published in the journal Advanced Functional Materials.
Source: Chalmers University