High Li-Ion Conductivity Artificial Interface Enabled by Li-Grafted Graphene Oxide for Stable Li Metal Pouch Cell

The fragile electrolyte/Li interface is responsible for the long-lasting consumption of Li resources and fast failure of Li metal batteries. The polymer artificial interface with high mechanical flexibility is a promising candidate to maintain the stability of the electrolyte/Li interface; however, sluggish Li-ion transportation of the conventional polymer interface hinders the application. In this work, Li-functionalized graphene oxide (GO-ADP-Li-3), which is synthesized by covalent grafting of adenosine 5'-diphosphate lithium on GO nanosheets, is used as a functional additive to improve the Li-ion conductivity of the polymer artificial interface based on PVDF-HFP/LiTFSI. The enhanced Li-ion conductivity is contributed by accelerated Li-ion hopping at the surface between polymer chains and functionalized GO as well as the reduced crystallization degree of PVDF-HFP by this novel additive. The use of this modified polymer as an artificial interface on Li foil enables highly reversible Li stripping/plating and a high capacity retention of 78.4% after 150 cycles for a 0.2 A h Li metal pouch cell (Li/NCM811, strictly following practical conditions). This Li-grafted strategy on GO sheets provides an alternative for designing a compatible electrolyte/Li interface for practical Li metal batteries.