(189ap) A Molecular Dynamics Study on Interfacial Properties of NaClO4/Carbonate Electrolyte Near Graphene-Based Electrode for Na-Ion Battery
AIChE Annual Meeting
Monday, October 29, 2018 - 3:30pm to 5:00pm
Lithium ion batteries (LIBs) have been widely adopted as a promising power source for portable energy storage due to their high storage capacities and excellent rate performance over other rechargeable batteries. However, the cost for Li continues to be on the rise because of the increasing demand for LIBs. The abundance and low cost of sodium makes Sodium-ion batteries (NIBs) as a highly attractive alternatives for large-scale energy storage applications. Considerable efforts have been made to find suitable electrode and electrolytes materials for NIBs, However, the details of the electrode-electrolyte interface are not well-understood yet. In this work, molecular dynamics simulations have been employed to investigate the structural rearrangement of electrolyte comprised of ethylene carbonate(EC), dimethyl carbonate(DMC), and NaClO4 salt near the pristine/N-doped graphene using Constant Potential Method (CPM). In the CPM simulations, the electrode charges are recalculated every time step and allowed to fluctuate in response to the local charge environment, which provides more realistic results compared to the simulations where the electrode atom charges are kept fixed. Our results show that the interfacial microstructure is highly dependent on the molecular geometry and polarity of each solvent and the electrode potential. Upon charging, the more polar EC is attracted while the less polar DMC is repelled from the interface. The results also show that ClO4 anions are rapidly accumulated (repelled) near the positive (negative) electrode with increasing potential. On the other hand, Na+ in the interface has weak dependence on the applied potential excluding at very high negative potentials. Moreover, we found that the applied potential have a significant impact on composition of the electrolyte at the interface and solvation structure around Na cation. Quantitative understanding of the electrode-electrolyte interface learned from this study may bear important implications towards the early stages of solid electrolyte-interface (SEI) and intercalation/deintercation process of Na cation in the NIBs.