New Material Promises Better Solid-State Batteries

A novel oxyhalide crystal shows how lithium can move efficiently even in cold temperatures—a potential boost for the next generation of solid-state batteries.

An international research team has presented a new crystalline solid-state electrolyte that could advance the development of more powerful lithium batteries. In the journal Science, the team describes an oxyhalide material called lithium tantalum oxychloride (LTOC), which exhibits high ionic conductivity even at low temperatures.

Chemist James Kaduk from the Illinois Institute of Technology was involved in the research and made a key contribution to elucidating the structure: Kaduk identified where the lithium ions are located within the crystal lattice and the paths along which they can move. This information is considered crucial for understanding the unusually good conductivity of the material and for further developing it in a targeted manner.

Why Lithium Is So Mobile in LTOC

Determining the lithium positions proved difficult because the usual tool for crystal analysis, X-ray diffraction, does not adequately image light elements. According to Kaduk, lithium, with only three electrons, is particularly difficult to detect when surrounded by heavy atoms such as tantalum.

Instead of locating the lithium ions directly, he used an indirect approach. First, the positions of the heavier atoms were determined. Kaduk then deduced possible lattice sites for lithium from the resulting interstices. These were so close together that easy ion transport is possible.

Open Channels in the Crystal Lattice

The structure reconstructed in this way showed long, rigid chains of tantalum, oxygen, and chlorine, between which open channels are formed. Lithium ions can diffuse relatively freely along these channels, which explains the high conductivity of the material.

The researchers used quantum mechanical simulations to verify their findings. Kaduk said that density functional quantum mechanical methods were used to optimize the structure. In the process, it remained stable with virtually no changes. The results are considered an important step toward solid-state electrolytes that work reliably even in cold temperatures and could therefore be relevant for applications ranging from electric vehicles to stationary energy storage systems.

This is a partly automated translation of this german article.