Functional multilayer solid electrolyte films for lithium dendrite suppression

The improvement of the interface between a lithium metal and a solid electrolyte layer is very important for the application of a lithium anode coated by solid electrolytes in lithium metal batteries. In order to address the issues of interface performance and compatibility between solid electrolyte films prepared by magnetron sputtering and lithium metals and the suppression of lithium dendrite during the cycling, a three-layer interface solid electrolyte film based on carbon-doped lithium phosphate oxynitride (LiCPON) was employed for coating a lithium metal. The sandwich structure of LiCPON by introducing an ultra-thin lithium niobium oxynitride (LiNbON) layer prepared by sputtering LiNbO₃ in nitrogen ambient can be confirmed by time-of-flight secondary ion mass spectrometry. Atomic force microscopy data indicated that the surface of the LiCPON thin film with the sandwich structure is flatter and smoother than that of the LiCPON thin film on the lithium metal. The interface impedance of the symmetric battery based on the sandwich structure of the LiCPON coating lithium metal was reduced from 512.2 to 65.4 Ω, and the symmetric battery stable cycles from 300 h with an overpotential of more than 200 mV to 400 h with low overpotential of about 77 mV. These results suggest that functional multilayer solid electrolyte films become an effective method for protecting lithium. The incorporation of ultra-thin LiNbON into the LiCPON thin film could significantly decrease interface impedance between the lithium metal and solid electrolyte layer.