Multiscale molecular dynamics and electrochemical modelling of sodium- ion batteries: Impact of electrolyte composition

S Chandel and VK Garapati and NN Dingari and M Mynam and B Rai, JOURNAL OF ENERGY STORAGE, 123, 116749 (2025).

DOI: 10.1016/j.est.2025.116749

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries, owing to the similarity in chemistry and abundant supply of sodium and other essential materials. Among the battery components, electrolytes play a pivotal role in ensuring safe and reliable battery operation. However, a poor choice of electrolytes can result in high internal heat generation, especially at high discharge rates. Therefore, identifying good electrolyte material is crucial for improving battery performance and safety. While experimental approaches are typically used to do this, they are time-consuming and resource intensive. The multi- scale approach presented in this work provides a computational methodology that can help evaluate electrolyte material for Na ion systems. It employs molecular dynamics (MD) simulations to predict the transport properties of electrolytes. MD simulations of 1 M NaPF6 in a 1: 1 EC: PC solvent mixture shows good agreement with experimental data, thereby confirming the validity of the simulation protocol. The optimal concentration for peak ionic conductivity is found to be 1 M NaPF6. Among various solvent compositions tested (i.e. EC: PC from 3: 7 to 9: 1 and 1 M salt concentration), peaks in transport properties are observed for the EC: PC = 7: 3 electrolyte. Subsequently, the transport properties obtained from the MD simulations are used in the electrochemical model to obtain system level performance insights such as voltage-discharge curves, internal heat generation, and concentration polarization. We utilize this multiscale approach to evaluate two solvent ratios, 7: 3 and 1: 1, of EC: PC for NaPF6 salt based electrolyte. Simulation results show good agreement with experimental data to highlight that the multiscale approach is an effective tool to design and optimize electrolyte composition.

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