Fluoride electrolyte breaks 5-volt limit in solid-state batteries

Researchers at Yonsei University have developed a novel fluoride-based solid electrolyte, LiCl–4Li₂TiF₆, that enables all-solid-state batteries (ASSBs) to safely operate beyond the longstanding 5-volt limit. This breakthrough overcomes a major challenge in battery technology, as conventional solid electrolytes typically degrade above 4 volts. The new electrolyte combines high voltage stability with excellent ionic conductivity (1.7 × 10⁻⁵ S/cm at 30°C), allowing it to work effectively with high-energy spinel cathodes like LiNi₀.₅Mn₁.₅O₄ (LNMO). When applied as a protective coating, it prevents interfacial breakdown, resulting in batteries that retain over 75% capacity after 500 charge cycles and achieve a record areal capacity of 35.3 mAh/cm². The technology also demonstrated consistent performance in pouch-type cells, indicating practical viability for electric vehicles and electronics. Beyond enhancing