New developments mean the world may soon see all-solid-state battery technology.

Currently, Li-ion cells based on liquid electrolytes are used as batteries for electric vehicles and energy storage devices.

However, these batteries use flammable liquid electrolytes, and so come with a range of safety concerns.

To solve this safety issue, all-solid-state battery technology, in which all battery components are replaced with solid materials, has recently attracted great attention.

But unlike a liquid electrolyte in which Li-ions can freely move, a solid electrolyte has a low Li-ion conductivity of 1/10 to 1/100 of that of a liquid electrolyte because the movement of Li-ions is confined within a rigid solid lattice.

This is one of the most important and difficult challenges in the development of all-solid-state battery technology, and its technical and economic value is very great.

Korean researchers have developed a solid electrolyte with superionic conductivity using a sulfide-based crystalline structure called argyrodite.

This crystal structure has high expectations due to its high Li-ion concentration and structural stability, but its Li-ion conductivity has remained below 4 mS/cm due to the structural uniqueness of Li-ions trapped in the octahedral cage in the argyrodite crystal.

The research team has come up with a novel Li-ion pathway that crosses the octahedral cage by applying a technique for selectively substituting chlorine, a halogen element, at specific atomic positions.

The new solid electrolyte material has an Li-ion conductivity of 10.2 mS/cm, which is equivalent to that of a conventional liquid electrolyte at room temperature, and still maintains electrochemical stability under various battery operating conditions.

The new synthesis method has attracted extra attention as it is possible to maximise the mass productivity of superionic solid electrolyte materials

“Synthesis of superionic sulphide materials through rapid process is very likely to be commercialised, and can be widely used in electric vehicles and energy storage system as a solid electrolyte in the future,” says lead researcher Dr Hyoungchul Kim.

The study is accessible here.