Computational research conducted by CINE members has advanced the understanding of a process that occurs spontaneously within sodium-ion batteries and significantly impacts their performance. The study’s results offer concrete guidelines for controlling this phenomenon and, consequently, improving battery performance.

Sodium-ion batteries are promising contenders to compete with lithium-ion batteries, which currently dominate the market. Indeed, sodium is far more abundant and widely distributed across Earth than lithium; however, sodium technology still offers lower energy density than lithium technology, which means that sodium batteries require greater volume and weight to store the same amount of energy as lithium batteries.

To overcome this technological challenge, it is crucial to understand—at the atomic scale—the mechanisms governing interactions between the anode (the electrode where sodium ions are stored during battery discharge) and the electrolyte (the substance enabling the transport of sodium ions between electrodes).

In this context, scientists from CINE’s Computational Materials Design division are studying a critical aspect of these interactions: the formation of an extremely thin layer on the surface of anodes made of metallic sodium. Known as the “solid electrolyte interphase” (SEI), this layer forms through the decomposition of electrolyte components.

When the SEI is of high quality, it protects the anode from continuously reacting with the electrolyte while simultaneously allowing the passage of sodium ions, thereby enabling the battery to charge and discharge. On the other hand, when the SEI is of poor quality, it cracks and grows unevenly, triggering the growth of needle-like sodium structures known as dendrites—a primary cause of battery failure and safety risks.

Consequently, the CINE team set out to understand the SEI formation processes at the atomic scale. This objective could only be achieved through computational tools, as an experimental study would be unfeasible given the SEI’s nature: ultrathin, chemically heterogeneous, and dynamically variable.

“In our project, we selected a few electrolytes and one type of anode— made of sodium metal—and, then, we simulated how individual electrolyte molecules interact with that anode,” explains Professor Juarez L. F. Da Silva (IQSC-USP), coordinator of CINE’s Computational Design division, who led the research.

Initially, the authors used quantum physics-based computer simulations to construct a model of a metallic sodium surface with defects. “Real sodium metal surfaces are never perfectly smooth. They have small clusters of atoms sticking up and tiny pits where atoms are missing,” explains Tapasendra Adhikary, first author of the study and a postdoctoral researcher at the São Carlos Institute of Chemistry at USP (IQSC-USP).

In this model, the team simulated interactions with 22 chemical species commonly found in battery electrolytes. According to Tapasendra, the idea was to understand which electrolyte molecules bind to which anode sites—and why—in order to design electrolytes that can control the SEI layer formation.

Thus, the scientific team investigated how electrolyte components interact with a defective sodium anode at the atomic scale and how these interactions shape the initial stages of SEI formation.

“The key discovery is that these irregularities on the sodium surface act as critical sites for chemical activity,” says Tapasendra. In other words, he explains, the location where a molecule binds depends heavily on the surface geometry.

Based on the results obtained, the authors formulated concrete guidelines for designing electrolytes that promote the formation of high-quality SEI layers. “First, salts that release fluoride should be favored, since fluoride binds especially strongly to the reactive defect sites and forms sodium fluoride, a tough inorganic layer that is very effective at plugging these weak points and blocking dendrite growth,” suggests Tapasendra.

The second guideline involves combining these fluoride-releasing salts with cyclic carbonate solvents to create conditions favorable for the formation of a fluoride- and carbonate-rich protective layer, precisely at the anode’s most vulnerable points.

Furthermore, the authors emphasize the importance of designing and testing electrolyte formulations using real, imperfect electrode surfaces rather than idealized, flat ones, as surface roughness is what truly determines where and how the protective layer forms.

This research was funded by FAPESP and Shell, with strategic support from the ANP.

Paper reference: First-principles study of chemical species adsorption and solid electrolyte interphase formation on defective sodium metal anodes. Tapasendra Adhikary, Iván Ornelas–Cruz, Tuanan C. Lourenço, Sara Barati, Luís G. Dias, Juarez L.F. Da Silva. Applied Surface Science, Volume 745, 2026, 167352. https://doi.org/10.1016/j.apsusc.2026.167352.

CINE members who authored the paper: Tapasendra Adhikary (postdoc at IQSC-USP), Iván Ornelas-Cruz (postdoc at IQSC-USP), Tuanan da Costa Lourenço (postdoc at IQSC-USP at the time of the research), Sara Barati (postdoc at the Institute of Chemistry at 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).