A recently published computational study provides important contributions to the development of new, safe, high-performance batteries. Conducted by a team of researchers from CINE together with collaborators from the University of Bonn (Germany), the work investigated in detail compounds that can be used as electrolytes in sodium-ion batteries.

Based on sodium, an abundant element that is well distributed throughout the planet, these batteries are considered very promising, especially for storing excess energy from solar and wind farms. Their operation is based on the movement of sodium ions between the battery electrodes, passing through the electrolyte, during the device’s charging and discharging.

Among the most studied compounds for conducting these ions in the electrolyte are ionic liquids, a family of salts that are in a liquid state at room temperature. In addition to being good ion conductors, these compounds, which are non-flammable, offer high safety to batteries. However, the addition of sodium ions to these liquids leads to an increase in viscosity, which reduces the mobility of the ions, worsening the performance of the electrolyte.

Seeking to overcome this limitation, researchers at CINE investigated a series of electrolytes based on two types of ionic liquids: aprotic, which is the most widely used in electrolyte research, and protic, which is cheaper and easier to produce but has been little studied to date. The idea was to add sodium salt to these compounds in order to improve the mobility of the ions.

“The main point of this work was to evaluate the effect of increasing the concentration of sodium salt in an electrolyte based on a protic ionic liquid and its analogue containing an aprotic ionic liquid,” summarizes Tuanan da Costa Lourenço, a CINE postdoctoral fellow at IQSC-USP and corresponding author of the article reporting this study.

To develop the study, the team performed molecular dynamics simulations, a computational method that describes the interactions of atoms and molecules. Using dozens of networked computers and advanced software, the authors solved the complex mathematical equations involved in the simulations. In the process, computing resources from USP, from the Brazilian National Laboratory for Scientific Computing, and from the University of Bonn were used.

The results showed that increasing the concentration of sodium salt changes the way in which the ions in the ionic liquid organize themselves and interact with each other. The work also demonstrated that the magnitude of this change depends on the molecular structure of the ions and the protic or aprotic characteristics of the ionic liquid. “In addition, we observed that at high concentrations of sodium salt, there is a decrease in the interaction forces between the sodium ion and the anion of the electrolytes, which can be beneficial for the functioning of a battery,” says Tuanan.

International collaboration

Selecting promising electrolytes for the batteries of the future is one of the objectives of the CINE Computational Materials Design division, which is coordinated by Professor Juarez L. F. Da Silva. In this case, the work involved the participation of members from USP, as well as members of Professor Barbara Kirchner’s research group at the University of Bonn, which is dedicated to modeling large and complex systems involving liquids and their interfaces.

“The collaboration not only made it possible to deepen the discussion and obtain conclusions, but also resulted in the development of new tools, improvements to the models used in this study, and new works and collaborations,” says Tuanan, who spent 15 months in Professor Kirchner’s group working on this study. According to him, the experience was also fundamental to his training and career as a researcher, as it provided contact with new scientists and methodologies.

The study was funded by Fapesp, Shell and Capes, European agencies, and strategic support from ANP.

Currently, the scientific team is continuing this research through a second study that aims to understand how to modulate the interactions between the ions of ionic liquids in order to optimize battery performance.

Paper reference: Structural investigation of protic ionic liquid electrolytes with sodium salt using polarizable force fields. Tuanan C. Lourenço, Paul Zaby, Luis G. Dias, Juarez L. F. Da Silva, Barbara Kirchner. Journal of Molecular Liquids. Volume 428, 15 June 2025, 127496. https://doi.org/10.1016/j.molliq.2025.127496.

CINE members who authored the paper: Tuanan da Costa Lourenço (postdoc at IQSC-USP), Luís Gustavo Dias (professor at the School of Philosophy, Sciences and Letters of Ribeirão Preto – USP) and Juarez L. F. Da Silva (professor at IQSC-USP).