The breakthrough in battery technology brings new, safe material, charges fast, and works in temperatures suitable for vehicles.
Solid-state lithium-ion batteries with solid electrolytes are safer, have higher energy density, and better ion transfer than liquid electrolyte batteries, making them promising for electric vehicles. However, they face challenges such as lower ion conductivity and difficulty maintaining good electrode contact. Sulphide-based solid electrolytes, while conductive, react with moisture to produce toxic gas. Therefore, there is a need for non-sulfide solid electrolytes that are both conductive and air-stable for safer and more efficient batteries.
Researchers from Tokyo University of Science, along with DENSO CORPORATION, have discovered a stable and highly conductive Li-ion conductor with a pyrochlore-type oxyfluoride structure.
In this study, using X-ray diffraction and Rietveld analysis, researchers analysed a pyrochlore-type oxyfluoride, Li2-xLa(1+x)/3M2O6F (M = Nb, Ta). They developed a composition, Li1.25La0.58Nb2O6F, with high ionic conductivity (3.9 mS cm⁻¹ at room temperature), outperforming known oxide solid electrolytes. This material remains highly conductive even at low temperatures, making it one of the most effective solid electrolytes, including those based on sulphide.
The material’s conductivity is maintained at –10°C, similar to conventional oxide-based electrolytes at room temperature, and it remains conductive above 100°C, extending its operational range. This is important as traditional lithium-ion batteries are not practical below freezing. The Li-ion conduction mechanism involves Li-ions moving through tunnels in the MO6 octahedra structure. Notably, this oxide-based solid-state battery technology eliminates the risks of electrolyte leakage and toxic gas generation associated with traditional and sulphide-based lithium-ion batteries.
The new material stands out for its high stability and resistance to ignition even when damaged, making it ideal for use in aeroplanes and other settings where safety is paramount. Its suitability for high-capacity applications, such as electric vehicles, is due to its ability to operate under high temperatures and support rapid charging. Additionally, its potential for miniaturising batteries makes it a promising candidate for use in home appliances and medical devices.
