Lithium-Ion Dynamics in Sulfolane-Based Highly Concentrated Electrolytes

Here,we report the use of molecular dynamics simulationswitha polarizable force field to investigate Li-ion dynamics in sulfolane(SL)-based electrolytes. In SL-based highly concentrated electrolytes(HCEs) (e.g., SL/Li = 2:1), Li displays faster translational motionthan other components, which should be related to the structural anddynamical properties of SL. In HCEs, a transient conduction networkthat penetrated the simulation system was always observed. Rapid (<1ns) Li-ion hopping between adjacent coordination sites was observedthroughout the network. Additionally, SLs rotated in the same timeframewithout disrupting the conduction network. This rotation is believedto promote the hopping diffusion in the network. This was followedby a rotational relaxation of the SL dipole axis around the non-polarcyclohydrocarbon segment of SL (& SIM;3.3 ns), which involves areorganization of the network structure and an enhancement of thetranslational motion of the coordinating Li ions. The observed lifetimeof Li-SL coordination was longer (>11 ns). Hence, it wasconcludedthat the faster Li translational motion was obtained due to the fasterrotational relaxation time of SL rather than the lifetime of Li-SLbinding. The faster rotation of SL is related to its amphiphilic molecularstructure with compact non-polar segments. Transport properties, suchas the Onsager transport coefficients, ionic conductivity, and transferencenumber under anion-blocking conditions, were also analyzed to characterizethe features of the SL-based electrolyte.