New superionic material could help create more efficient batteries

Researchers from Duke University have studied the mechanism of fast ion mobility in the superionic compound Li₆PS₅Cl. They found that the ions in this material behave like a liquid, which could significantly improve the efficiency of solid-state batteries. The work was published in the journal Nature Physics.

What are superionic materials?

Superionic compounds have unique properties: in their structure, some ions remain in place, while others move freely, as in a liquid. This makes them promising electrolytes for solid-state batteries, which in the future could replace traditional lithium-ion batteries.

Unlike batteries with liquid electrolytes, solid-state batteries provide increased safety, greater durability, and high energy capacity. However, the mechanisms of ultra-fast ion movement in such materials are still poorly understood.

Research on lithium argyrodite

Scientists focused on the compound Li₆PS₅Cl, one of the most promising solid-state electrolytes.

The main question of the research: do the lithium ions in this material move like ordinary atomic vibrations or do they behave more like a liquid?

To find out, the team used:

• Neutron scattering to study atomic vibrations over a wide frequency range (from gigahertz to terahertz).
• Computer modeling using machine learning methods to analyze the interaction of lithium ions with the crystal lattice.

The calculations were carried out on high-performance computing systems, which allowed us to obtain a detailed picture of the ion motion.

Main discoveries

Transition to a liquid-like state:

• As the temperature increases, lithium ions change their behavior, becoming more mobile.
• Spectral analysis showed that their dynamics gradually transition from crystalline to liquid-like.

The reason for high conductivity:

• Previously, it was believed that ionic mobility is determined by vibrations of the crystal lattice.
• New data show that liquid-like effects play a key role.

What does this mean for batteries?

Improving Solid-State Batteries

New knowledge will help develop materials with high ionic conductivity and stability.

Applications in other technologies

Superionic materials are promising not only for batteries, but also for fuel cells, sensors and processors.

“Superionic materials have complex dynamics, and their design remains a challenge,” said Olivier Delaire, lead author of the study.

The results of the work pave the way for the development of new generations of energy-dense and safe batteries that could revolutionize the energy storage market.