Researchers from Instituto Superior Técnico contribute to the discovery and characterisation of a new family of organic materials capable of conducting ions in the solid state with the same efficiency observed in the liquid state. The research, published in Science on December 18, 2025, introduces the concept of state-independent electrolytes (SIEs), which contradicts a principle of electrochemistry.
José Nuno Canongia Lopes, Karina Shimizu and Adilson Freitas, Técnico professors at the Department of Chemical Engineering (DEQ) and researchers at Centro de Química Estrutural (CQE), were part of the international team responsible for identifying and understanding the ionic transport mechanisms (electric current) of these new materials. In conventional systems, the transition from a liquid to a solid state results in a significant decrease in ionic mobility. In the SIEs now described, this limitation does not occur: conductivity is unchanged across liquid, liquid-crystal, and solid phases.
The materials developed are based on a specific molecular architecture, composed of a “rigid disc-shaped centre and long flexible side chains”, explains José Nuno Lopes. This organisation prevents the formation of strong bonds between positive and negative ions, allowing the anions to move along solid structures organised in columns.
Over a period of two months, the Técnico team focused on molecular modeling and simulation of the system, an essential component for understanding the phenomenon observed experimentally. “We developed a systematic and coherent atomistic force field (a set of functions and parameters that describe the interactions in the system and allow the simulation of its behaviour), capable of describing all the interactions in the system and being used in molecular dynamics simulations”, says Karina Shimizu. The lack of previous data in the literature regarding these materials required the validation of the model using simpler, structurally similar crystalline systems.
The simulations helped clarify a key question raised by the experimental partners: the preferred interaction sites between chloride anions and large organic cations. “We found that the anions remain most often on the periphery of the central discs of the molecules, rather than close to the side chains”, explains José Nuno Lopes. Additional simulations, conducted in the presence of an external electric field, revealed that “the average velocity of the ions is not influenced by the orientation of the field in relation to the orientation of the crystal”, which helps explain the continuity of ion transport during phase transitions.
According to the Técnico researcher, the acceptance of this work in Science highlights the groundbreaking nature of the discovery. “It is not enough to conceive, synthesise, and characterise a new material—it is essential to demonstrate that it fully addresses a current challenge and overcomes a previously assumed scientific limitation”, he says, referring to the widely accepted idea that solidification necessarily results in a loss of electrical conductivity.
This discovery reinforces Técnico’s research efforts in the field of ionic liquids and functional materials and opens up new opportunities for international collaboration. Cooperation with the University of Oxford remains active, with new work planned. The Técnico team has also been invited to apply for an ERC Synergy grant, in partnership with the University of Oxford and the National Institute of Materials Science in Japan.
The results now published point to future applications in safer solid-state batteries, sensors, electrochromic devices, and flexible electronics, contributing to the development of more efficient and versatile devices. According to Adilson Freitas, these solutions may also involve the “development of medical devices of different shapes and sizes”, as they allow for “safe use in solid form, without loss of ionic conductivity”.
This work is the result of an international collaboration involving researchers from the Universities of Oxford, York, and Durham (United Kingdom), Instituto Superior Técnico – Universidade de Lisboa (Portugal), the University of Halle-Wittenberg (Germany), and the University of Chemistry and Technology in Prague (Czech Republic).
