Multiscale Investigation on Electrolyte Systems of [(Solvent plus Additive) + LiPF6] for Application in Lithium-Ion Batteries

摘要

To investigate how the electrolyte system of [(solvent + additive) + lithium salt LiPF6] can promote the performance of lithium-ion batteries (LIBs), a multiscale method consisting of density functional theory (DFT) calculations at the pico-nano-scale level, molecular dynamics (MD) simulation at the nanoscale level, and pseudo-two-dimensional (P2D) electrochemical modeling at the macroscale level were employed. The solvent used in the studied electrolyte systems was ethyl methyl carbonate (EMC), and the additives were ethylene carbonate (EC), fluoroethylene carbonate (FEC), and succinonitrile (SN). The results indicated that at moderate temperatures the electrolyte systems [(EMC + SN 10) + LiPF6] and [(EMC + FEC 10) + LiPF6] represent higher performance compared with the conventional electrolyte [(EMC + EC 30) + LiPF6], since they create lower ohmic polarization in the LIB operation. Also, the molecular configuration of the electrolytes was obtained by DFT calculations and their structural and transport properties were evaluated by MD simulations. To determine the operational properties of LIB such as voltage and polarizations at the macroscale level, the evaluated properties by DFT and MD methods were inserted, as the basic parameters, for solving the continuity equations in the P2D model. In this way, we achieved an insight into the relation between the molecular structure and transport properties of electrolytes, which can influence the performance of a LIB and which can be useful in designing novel LIBs.