Prof. Thomas F. Fässler in his TUM lab, where his team set a new speed record for lithium-ion conductivity in solid-state battery materials. [Image courtesy of TUM]
The breakthrough is detailed in a research article published April 28, 2025, in Advanced Energy Materials and a news announcement. In the study, Fässler’s team describes how substituting a portion of lithium in Li₃Sb with scandium created a compound, Li₂.₅₅Sc₀.₁₅Sb, that achieved lithium-ion conductivity of 42 mS/cm at room temperature (298 K). That’s more than 30% faster than any previously reported solid electrolyte, with a record-low activation energy of 17.6 kJ/mol.
What’s different
While many solid electrolytes rely on complex, often seven-element, material “cocktails,” the new TUM material from Professor Fässler’s group achieves its conductivity with just three core ingredients: lithium, scandium, and antimony. One factor driving the development was the substitution of a small amount of scandium for lithium in the parent compound Li₃Sb, resulting in the optimal formula Li₂.₅₅Sc₀.₁₅Sb. This targeted substitution engineers specific, intentionally created vacancies within the crystal lattice.
Our result currently represents a significant advance in basic research. By incorporating small amounts of scandium, we have uncovered a new principle that could prove to be a blueprint for other elemental combinations. —Fässler
These vacancies function as ‘express lanes,’ providing ions more room to move and allowing them to zip through nearly a third faster than in the previous leading material. This streamlined, three-element chemistry not only avoids the need for rare chalcogenides and potentially exotic processing steps but also hints at pathways for easier and less expensive scaling compared to more complex alternatives.
Matching liquid-electrolyte conductivity without the flammable solvent removes the main knock on solid-state batteries: sluggish power. If the material holds up inside a full cell, EV makers could chase higher energy density without adding elaborate cooling hardware.
What’s next
Building on this initial success, the team plans further research, as detailed in their Advanced Energy Materials publication, where they state, “A detailed investigation into the mechanism for lithium-ion diffusion of this compound is on-going and will be presented elsewhere.” Their “Future work will [also] focus on probing the electrochemical properties of the entire compound series… assessing electrochemical stability, and evaluating the performance in ASSBs using half-cell or full-cell setups.“
First author Jingwen Jiang elaborated that “the same concept can easily be applied to lithium-phosphorus systems” and “could have broader implications for enhancing conductivity in a wide range of other materials.
