Powering the Future: A Computational Exploration of Lithium and Sodium Salts for Better Energy Storage and Ion Mobility

Catarina Isabel Sousa da Silva

Key information

Authors:

Catarina Isabel Sousa da Silva (Catarina Isabel Sousa da Silva)

Supervisors:

Karina Shimizu (Karina Shimizu); Adilson Alves de Freitas (Adilson Alves de Freitas)

Published in

December 10, 2024

Abstract

The increasing demand for sustainable energy storage solutions has prompted extensive research into alternative battery systems. This thesis investigates the structural characteristics and aggregation behaviours of lithium-ion (Li+) and sodium-ion (Na+) electrolytes, focusing on the Na[FSA] and Li[FSA] systems, where [FSA]− stands for Bis(fluorosulfonyl)amide. Using Molecular Dynamics simulations, we explore the interactions between cations (Li+ and Na+), anions ([FSA]−), and solvent molecules (sulpholane (SL) and 3-methylsulpholane (MSL)) at various concentrations. The methodology involves analysing the aggregation tendencies of Li+ and Na+ cations with [FSA]− anions, and SL and MSL molecules across different solvent concentrations. Aggregation analysis re- veals that lower salt concentrations lead to smaller aggregates, with a significant percolation threshold observed between xsolvent = 0.67 and xsolvent = 0.75. The results demonstrate that Na+ ions form larger cation-anion aggregates, comprising up to 90% of the ion pairs, while Li+ systems predominantly exhibit smaller aggregates. The findings indicate that Na+ shows reduced binding affinity to solvent molecules compared to Li+, which facilitates greater ion transport in Na-based systems. Additionally, the structural similarity between Lithium and Sodium-based electrolytes suggests that sodium can effectively replace lithium as a charge carrier without compromising performance. The analysis of the first solvation shell reveals a more heterogeneous environment in Na+ systems, warranting further exploration of the relationship between local heterogeneity and macroscopic properties. In conclusion, this thesis provides critical insights into the potential of sodium-ion systems for energy storage applications, highlighting the feasibility of using Sodium as a sustainable alternative to lithium.