Lithium Phosphate Covered Reduced Graphene Oxide as Anode Material for Lithium-Ion Batteries

The solid electrolyte interface (SEI) formed between anode materials and the electrolyte is important for the cycling performance of the lithium-ion batteries, which promotes much research effort on studying the effect of SEI on the performance of the batteries. However, the complicated structures and chemical compositions of the SEI layer make it a complex component to understand. Therefore, investigating a specific component in the SEI can provide helpful guidelines to the design of electrolytes and artificial SEI. In this work, we chose lithium phosphate (Li3PO4), one of the attractive solid electrolytes, as an artificial SEI and studied the electrochemical performance of Li3PO4 covered reduced graphene oxide (r-GO) as anode materials for lithium-ion batteries. R-GO was produced by reducing graphene oxide using a hydrothermal process. Rather than typical coating methods such as sputtering or chemical vapor deposition, the process we chose for coating lithium phosphate layer on r-GO is through wet chemical synthesis. Since the formation of SEI occurs at all the interface between anode materials and the electrolyte instead of only the surface of the anode materials, wet chemical synthesis ensures high surface coverage of lithium phosphate on r-GO. The role of lithium phosphate on the electrochemical properties of SEI was investigated by studying the cycling performance and electrochemical impedance spectroscopy (EIS) of lithium phosphate covered r-GO as anode materials. This work provides insights for the design of artificial SEI which could effectively passivate the electrode, thereby improving the safety and cycle life of the lithium-ion batteries.