Mechanistic insight into the performance enhancement of Si anode of a lithium-ion battery with a fluoroethylene carbonate electrolyte additive

Silicon anode, even with its theoretically high specific capacity, has only seen a limited commercial adoption in lithium-ion battery (LIB) due to the durability issues. The performance of a silicon anode in a LIB is enhanced when a small amount of fluoroethylene carbonate (FEC) is added to the battery electrolyte. In this article, we analyze the effect of FEC additive on the silicon anode in both the half- and full cell configuration. Electrochemical impedance spectroscopy is used to unravel crucial intrinsic properties of the cell. It detects a fourfold drop in the cell impedance upon addition of FEC. We also employed density functional theory (DFT)-based models to understand and complement the experimental findings. At the DFT level, the solvation energy of Li+ in the ethylene carbonate (EC) electrolyte is − 224.34 kJ mol−1 whereas that in the FEC electrolyte is − 202.96 kJ mol−1. This implies that the electrolyte with the FEC additive may act as a better carrier of Li+ that with the EC additive alone.