(668c) Computational Analysis and Prediction of the Interfacial Structure and Na Storage Mechanism of Carbon Electrodes in an NaClO4/Carbonate Electrolyte

Sodium-ion batteries (NIBs) are in the spotlight as highly promising energy storage applications due to the low cost and wide availability of Na sources. While a number of efforts have been devoted to study the electrodes and electrolytes in NIBs, fundamental understanding on the Na-based systems are still in their infancy. In this talk, we will present the structural and transport properties of Na⁺/ClO₄^-/EC/DMC electrolyte near the pristine/N-doped graphene electrodes using molecular dynamics simulations. We particularly adopted Constant Potential Method (CPM) in which electrode atom charges were recalculated every time step in response to the local charge environment, leading to a more realistic model. We observed that the molecular geometry and polarity of EC/DMC and the applied potential significantly affected the microstructure of the electrolyte at the interface. For example, number density of EC increases with O moiety heading towards the bulk electrolyte at 2V, while O surrounds Na⁺ ions and points to the electrode at 4V near the negative electrode. We also predicted the free energy barriers to Na⁺ and ClO₄^- ion transport through the interfacial layer upon the applied potential using well-tempered metadynamics simulations. Finally, we will also discuss the impact of degree of graphene orders and heteroatom-doping on the Na ion storage behavior.