Sodium-ion electrolytes based on poly-ethylene oxide oligomers in dual-carbon cells: Anion size drives the charging behavior

Author(s)

Mendes, Rodrigo A. ; Dias, Luis G. ; Da Silva, Juarez L. F. ; Siqueira, Leonardo J. A.

• Document type: Journal article
• Source: NANO ENERGY; v. 118, p. 9-pg., 2023-10-11.

Abstract

Sodium-ion dual-carbon electrochemical cells are an environmentally friendly technology for energy storage purposes. In such systems, the migration of mutual ions in both electrodes is crucial for performance and determines the cell's behavior. To investigate this effect, we have performed force-field molecular dynamics simulations of dual-carbon sodium-ion systems containing poly-ethylene oxide (PEO6) as the solvent and two different anions, bis(trifluoromethanesulfonyl)imide (TFSI-) and bis(fluorosulfonyl)imide (FSI-). We used a constant potential model that allows simulating the charging behavior of these cells at the potential differences, Delta Psi = 1, 2, 3, and 5 volt (V). Our results showed that considering the neat solution, NaTFSI-PEO6 exhibited the best transport properties. However, NaFSI-PEO6 is a better choice of electrolyte to be employed in dual-carbon cells since it provides higher and faster charge accumulation. Structural analysis also confirmed that the system containing NaFSI-PEO6 stored more ions inside their respective electrodes with Na+ cations having fewer molecules composing their first solvation shell. Overall, our findings suggest that the smaller molecular volume of the FSI- anion is the key factor to properly fill the positive electrode, and the NaFSI-PEO6 combination is the best choice for electrolytes of dual-carbon cells. (AU)

• FAPESP's process: 18/21401-7 - Multi-User Equipment approved in grant 2017/11631-2: cluster computational de alto desempenho - ENIAC
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 19/18125-0 - Computational study of materials with application in energy storage
• Grantee: Leonardo José Amaral de Siqueira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/11631-2 - CINE: computational materials design based on atomistic simulations, meso-scale, multi-physics, and artificial intelligence for energy applications
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Research Grants - Research Centers in Engineering Program